The absence of light.
That portion of the electromagnetic spectrum in the visible, ultraviolet, and infrared range.
The regular recurrence, in cycles of about 24 hours, of biological processes or activities, such as sensitivity to drugs and stimuli, hormone secretion, sleeping, and feeding.
Adjustment of the eyes under conditions of low light. The sensitivity of the eye to light is increased during dark adaptation.
The time period of daily exposure that an organism receives from daylight or artificial light. It is believed that photoperiodic responses may affect the control of energy balance and thermoregulation.
Specialized cells that detect and transduce light. They are classified into two types based on their light reception structure, the ciliary photoreceptors and the rhabdomeric photoreceptors with MICROVILLI. Ciliary photoreceptor cells use OPSINS that activate a PHOSPHODIESTERASE phosphodiesterase cascade. Rhabdomeric photoreceptor cells use opsins that activate a PHOSPHOLIPASE C cascade.
Disruptions of the rhythmic cycle of bodily functions or activities.
A light-sensitive neuroendocrine organ attached to the roof of the THIRD VENTRICLE of the brain. The pineal gland secretes MELATONIN, other BIOGENIC AMINES and NEUROPEPTIDES.
An ovoid densely packed collection of small cells of the anterior hypothalamus lying close to the midline in a shallow impression of the OPTIC CHIASM.
The illumination of an environment and the arrangement of lights to achieve an effect or optimal visibility. Its application is in domestic or in public settings and in medical and non-medical environments.
A reflex wherein impulses are conveyed from the cupulas of the SEMICIRCULAR CANALS and from the OTOLITHIC MEMBRANE of the SACCULE AND UTRICLE via the VESTIBULAR NUCLEI of the BRAIN STEM and the median longitudinal fasciculus to the OCULOMOTOR NERVE nuclei. It functions to maintain a stable retinal image during head rotation by generating appropriate compensatory EYE MOVEMENTS.
The adjustment of the eye to variations in the intensity of light. Light adaptation is the adjustment of the eye when the light threshold is increased; DARK ADAPTATION when the light is greatly reduced. (From Cline et al., Dictionary of Visual Science, 4th ed)
Geological formations consisting of underground enclosures with access from the surface.
A biogenic amine that is found in animals and plants. In mammals, melatonin is produced by the PINEAL GLAND. Its secretion increases in darkness and decreases during exposure to light. Melatonin is implicated in the regulation of SLEEP, mood, and REPRODUCTION. Melatonin is also an effective antioxidant.
A common name for fish of the family Percidae, belonging to the suborder Percoidei, order PERCIFORMES.
A blue-green biliprotein widely distributed in the plant kingdom.
The physiological mechanisms that govern the rhythmic occurrence of certain biochemical, physiological, and behavioral phenomena.
Circadian rhythm signaling proteins that influence circadian clock by interacting with other circadian regulatory proteins and transporting them into the CELL NUCLEUS.
The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent.
Involuntary rhythmical movements of the eyes in the normal person. These can be naturally occurring as in end-position (end-point, end-stage, or deviational) nystagmus or induced by the optokinetic drum (NYSTAGMUS, OPTOKINETIC), caloric test, or a rotating chair.
Investigative technique commonly used during ELECTROENCEPHALOGRAPHY in which a series of bright light flashes or visual patterns are used to elicit brain activity.
Porphyrin derivatives containing magnesium that act to convert light energy in photosynthetic organisms.
A pre-emergent herbicide.
The process in which light signals are transformed by the PHOTORECEPTOR CELLS into electrical signals which can then be transmitted to the brain.
Photosensitive afferent neurons located in the peripheral retina, with their density increases radially away from the FOVEA CENTRALIS. Being much more sensitive to light than the RETINAL CONE CELLS, the rod cells are responsible for twilight vision (at scotopic intensities) as well as peripheral vision, but provide no color discrimination.
Voluntary or reflex-controlled movements of the eye.
An oval, bony chamber of the inner ear, part of the bony labyrinth. It is continuous with bony COCHLEA anteriorly, and SEMICIRCULAR CANALS posteriorly. The vestibule contains two communicating sacs (utricle and saccule) of the balancing apparatus. The oval window on its lateral wall is occupied by the base of the STAPES of the MIDDLE EAR.
The region of the stem beneath the stalks of the seed leaves (cotyledons) and directly above the young root of the embryo plant. It grows rapidly in seedlings showing epigeal germination and lifts the cotyledons above the soil surface. In this region (the transition zone) the arrangement of vascular bundles in the root changes to that of the stem. (From Concise Dictionary of Biology, 1990)
Bouts of physical irritability or movement alternating with periods of quiescence. It includes biochemical activity and hormonal activity which may be cellular. These cycles are shorter than 24 hours and include sleep-wakefulness cycles and the periodic activation of the digestive system.
Flavoproteins that function as circadian rhythm signaling proteins in ANIMALS and as blue-light photoreceptors in PLANTS. They are structurally-related to DNA PHOTOLYASES and it is believed that both classes of proteins may have originated from an earlier protein that played a role in protecting primitive organisms from the cyclical exposure to UV LIGHT.
Photosensitive afferent neurons located primarily within the FOVEA CENTRALIS of the MACULA LUTEA. There are three major types of cone cells (red, blue, and green) whose photopigments have different spectral sensitivity curves. Retinal cone cells operate in daylight vision (at photopic intensities) providing color recognition and central visual acuity.
Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
A plant genus of the family BRASSICACEAE that contains ARABIDOPSIS PROTEINS and MADS DOMAIN PROTEINS. The species A. thaliana is used for experiments in classical plant genetics as well as molecular genetic studies in plant physiology, biochemistry, and development.
Constriction of the pupil in response to light stimulation of the retina. It refers also to any reflex involving the iris, with resultant alteration of the diameter of the pupil. (Cline et al., Dictionary of Visual Science, 4th ed)
The synthesis by organisms of organic chemical compounds, especially carbohydrates, from carbon dioxide using energy obtained from light rather than from the oxidation of chemical compounds. Photosynthesis comprises two separate processes: the light reactions and the dark reactions. In higher plants; GREEN ALGAE; and CYANOBACTERIA; NADPH and ATP formed by the light reactions drive the dark reactions which result in the fixation of carbon dioxide. (from Oxford Dictionary of Biochemistry and Molecular Biology, 2001)
Processes and properties of the EYE as a whole or of any of its parts.
Expanded structures, usually green, of vascular plants, characteristically consisting of a bladelike expansion attached to a stem, and functioning as the principal organ of photosynthesis and transpiration. (American Heritage Dictionary, 2d ed)
Abnormal sensitivity to light. This may occur as a manifestation of EYE DISEASES; MIGRAINE; SUBARACHNOID HEMORRHAGE; MENINGITIS; and other disorders. Photophobia may also occur in association with DEPRESSION and other MENTAL DISORDERS.
Biological mechanism that controls CIRCADIAN RHYTHM. Circadian clocks exist in the simplest form in cyanobacteria and as more complex systems in fungi, plants, and animals. In humans the system includes photoresponsive RETINAL GANGLION CELLS and the SUPRACHIASMATIC NUCLEUS that acts as the central oscillator.
Voluntary or involuntary motion of head that may be relative to or independent of body; includes animals and humans.
The primary plant photoreceptor responsible for perceiving and mediating responses to far-red light. It is a PROTEIN-SERINE-THREONINE KINASE that is translocated to the CELL NUCLEUS in response to light signals.
Proteins that originate from plants species belonging to the genus ARABIDOPSIS. The most intensely studied species of Arabidopsis, Arabidopsis thaliana, is commonly used in laboratory experiments.
Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in plants.
Geographic variety, population, or race, within a species, that is genetically adapted to a particular habitat. An ecotype typically exhibits phenotypic differences but is capable of interbreeding with other ecotypes.
The aperture in the iris through which light passes.
An order of the Amphibia class which includes salamanders and newts. They are characterized by usually having slim bodies and tails, four limbs of about equal size (except in Sirenidae), and a reduction in skull bones.
Awareness of oneself in relation to time, place and person.
The portion of a retinal rod cell situated between the ROD INNER SEGMENT and the RETINAL PIGMENT EPITHELIUM. It contains a stack of photosensitive disk membranes laden with RHODOPSIN.
A genus of fungus in the family Hypocreaceae, order HYPOCREALES. Anamorphs include TRICHODERMA.
A family of fresh water fish in the order CHARACIFORMES, which includes the Tetras.
The tendency of a phenomenon to recur at regular intervals; in biological systems, the recurrence of certain activities (including hormonal, cellular, neural) may be annual, seasonal, monthly, daily, or more frequently (ultradian).
A genus of the Ambystomatidae family. The best known species are the axolotl AMBYSTOMA MEXICANUM and the closely related tiger salamander Ambystoma tigrinum. They may retain gills and remain aquatic without developing all of the adult characteristics. However, under proper changes in the environment they metamorphose.
The non-genetic biological changes of an organism in response to challenges in its ENVIRONMENT.
Very young plant after GERMINATION of SEEDS.
The branch of biology dealing with the effect of light on organisms.
The conversion of absorbed light energy into molecular signals.
The most diversified of all fish orders and the largest vertebrate order. It includes many of the commonly known fish such as porgies, croakers, sunfishes, dolphin fish, mackerels, TUNA, etc.
Basic helix-loop-helix (bHLH) domain-containing proteins that play important roles in CIRCADIAN RHYTHM regulation. They combine with CLOCK PROTEINS to form heterodimeric transcription factors that are specific for E-BOX ELEMENTS and stimulate the transcription of several E-box genes that are involved in cyclical regulation.
Elements of limited time intervals, contributing to particular results or situations.
A gelatinous membrane overlying the acoustic maculae of SACCULE AND UTRICLE. It contains minute crystalline particles (otoliths) of CALCIUM CARBONATE and protein on its outer surface. In response to head movement, the otoliths shift causing distortion of the vestibular hair cells which transduce nerve signals to the BRAIN for interpretation of equilibrium.
An acetyltransferase with specificity towards the amine group of aromatic alkylamines (arylalkylamines) such as SEROTONIN. This enzyme is also referred to as serotonin acetylase despite the fact that serotonin acetylation can also occur through the action of broad specificity acetyltransferases such as ARYLAMINE N-ACETYLTRANSFERASE.
The physical activity of a human or an animal as a behavioral phenomenon.
Process whereby a cell, bodily structure, or organism (animal or plant) receives or detects a gravity stimulus. Gravity sensing plays an important role in the directional growth and development of an organism (GRAVITROPISM).
Basic helix-loop-helix (bHLH) domain-containing proteins that contain intrinsic HISTONE ACETYLTRANSFERASE activity and play important roles in CIRCADIAN RHYTHM regulation. Clock proteins combine with Arntl proteins to form heterodimeric transcription factors that are specific for E-BOX ELEMENTS and stimulate the transcription of several E-box genes that are involved in cyclical regulation. This transcriptional activation also sets into motion a time-dependent feedback loop which in turn down-regulates the expression of clock proteins.
A species of the true toads, Bufonidae, becoming fairly common in the southern United States and almost pantropical. The secretions from the skin glands of this species are very toxic to animals.
A plant photo regulatory protein that exists in two forms that are reversibly interconvertible by LIGHT. In response to light it moves to the CELL NUCLEUS and regulates transcription of target genes. Phytochrome B plays an important role in shade avoidance and mediates plant de-etiolation in red light.
Acceleration produced by the mutual attraction of two masses, and of magnitude inversely proportional to the square of the distance between the two centers of mass. It is also the force imparted by the earth, moon, or a planet to an object near its surface. (From NASA Thesaurus, 1988)
The initial stages of the growth of SEEDS into a SEEDLINGS. The embryonic shoot (plumule) and embryonic PLANT ROOTS (radicle) emerge and grow upwards and downwards respectively. Food reserves for germination come from endosperm tissue within the seed and/or from the seed leaves (COTYLEDON). (Concise Dictionary of Biology, 1990)
Proteins found in plants (flowers, herbs, shrubs, trees, etc.). The concept does not include proteins found in vegetables for which VEGETABLE PROTEINS is available.
An increase in the rate of speed.
Photosensitive protein complexes of varied light absorption properties which are expressed in the PHOTORECEPTOR CELLS. They are OPSINS conjugated with VITAMIN A-based chromophores. Chromophores capture photons of light, leading to the activation of opsins and a biochemical cascade that ultimately excites the photoreceptor cells.
Involuntary movements of the eye that are divided into two types, jerk and pendular. Jerk nystagmus has a slow phase in one direction followed by a corrective fast phase in the opposite direction, and is usually caused by central or peripheral vestibular dysfunction. Pendular nystagmus features oscillations that are of equal velocity in both directions and this condition is often associated with visual loss early in life. (Adams et al., Principles of Neurology, 6th ed, p272)
A genus of tree shrews of the family TUPAIIDAE which consists of about 12 species. One of the most frequently encountered species is T. glis. Members of this genus inhabit rain forests and secondary growth areas in southeast Asia.
A purplish-red, light-sensitive pigment found in RETINAL ROD CELLS of most vertebrates. It is a complex consisting of a molecule of ROD OPSIN and a molecule of 11-cis retinal (RETINALDEHYDE). Rhodopsin exhibits peak absorption wavelength at about 500 nm.
An abrupt voluntary shift in ocular fixation from one point to another, as occurs in reading.
Specialized PHOTOTRANSDUCTION neurons in the vertebrates, such as the RETINAL ROD CELLS and the RETINAL CONE CELLS. Non-visual photoreceptor neurons have been reported in the deep brain, the PINEAL GLAND and organs of the circadian system.
The natural satellite of the planet Earth. It includes the lunar cycles or phases, the lunar month, lunar landscapes, geography, and soil.
PLANTS, or their progeny, whose GENOME has been altered by GENETIC ENGINEERING.
Specialized cells in the invertebrates that detect and transduce light. They are predominantly rhabdomeric with an array of photosensitive microvilli. Illumination depolarizes invertebrate photoreceptors by stimulating Na+ influx across the plasma membrane.
The continent lying around the South Pole and the southern waters of the Atlantic, Pacific, and Indian Oceans. It includes the Falkland Islands Dependencies. (From Webster's New Geographical Dictionary, 1988, p55)
Plant cell inclusion bodies that contain the photosynthetic pigment CHLOROPHYLL, which is associated with the membrane of THYLAKOIDS. Chloroplasts occur in cells of leaves and young stems of plants. They are also found in some forms of PHYTOPLANKTON such as HAPTOPHYTA; DINOFLAGELLATES; DIATOMS; and CRYPTOPHYTA.
The act of knowing or the recognition of a distance by recollective thought, or by means of a sensory process which is under the influence of set and of prior experience.
Protein complexes that take part in the process of PHOTOSYNTHESIS. They are located within the THYLAKOID MEMBRANES of plant CHLOROPLASTS and a variety of structures in more primitive organisms. There are two major complexes involved in the photosynthetic process called PHOTOSYSTEM I and PHOTOSYSTEM II.
Recording of electric potentials in the retina after stimulation by light.
The Arctic Ocean and the lands in it and adjacent to it. It includes Point Barrow, Alaska, most of the Franklin District in Canada, two thirds of Greenland, Svalbard, Franz Josef Land, Lapland, Novaya Zemlya, and Northern Siberia. (Webster's New Geographical Dictionary, 1988, p66)
The positioning and accommodation of eyes that allows the image to be brought into place on the FOVEA CENTRALIS of each eye.
Used as an electron carrier in place of the flavine enzyme of Warburg in the hexosemonophosphate system and also in the preparation of SUCCINIC DEHYDROGENASE.
Common name for Carassius auratus, a type of carp (CARPS).
A genus of diurnal rats in the family Octodonidae, found in South America. The species Octodon degus is frequently used for research.
A phylum of oxygenic photosynthetic bacteria comprised of unicellular to multicellular bacteria possessing CHLOROPHYLL a and carrying out oxygenic PHOTOSYNTHESIS. Cyanobacteria are the only known organisms capable of fixing both CARBON DIOXIDE (in the presence of light) and NITROGEN. Cell morphology can include nitrogen-fixing heterocysts and/or resting cells called akinetes. Formerly called blue-green algae, cyanobacteria were traditionally treated as ALGAE.
The functional hereditary units of PLANTS.
Blue-light receptors that regulate a range of physiological responses in PLANTS. Examples include: PHOTOTROPISM, light-induced stomatal opening, and CHLOROPLAST movements in response to changes in light intensity.
The awareness of the spatial properties of objects; includes physical space.
Flavoproteins are a type of protein molecule that contain noncovalently bound flavin mononucleotide or flavin adenine dinucleotide as cofactors, involved in various redox reactions and metabolic pathways, such as electron transfer, energy production, and DNA repair.
Recording of the average amplitude of the resting potential arising between the cornea and the retina in light and dark adaptation as the eyes turn a standard distance to the right and the left. The increase in potential with light adaptation is used to evaluate the condition of the retinal pigment epithelium.
A large multisubunit protein complex found in the THYLAKOID MEMBRANE. It uses light energy derived from LIGHT-HARVESTING PROTEIN COMPLEXES to catalyze the splitting of WATER into DIOXYGEN and of reducing equivalents of HYDROGEN.
Common name for a number of different species of fish in the family Cyprinidae. This includes, among others, the common carp, crucian carp, grass carp, and silver carp.
The organ of sight constituting a pair of globular organs made up of a three-layered roughly spherical structure specialized for receiving and responding to light.
The visually perceived property of objects created by absorption or reflection of specific wavelengths of light.
Vibrio- to spiral-shaped phototrophic bacteria found in stagnant water and mud exposed to light.
The observable response an animal makes to any situation.
An enzyme that catalyzes the transfer of a methyl group from S-adenosylmethionine to N-acetylserotonin to form N-acetyl-5-methoxytryptamine (MELATONIN).
A photo-active pigment localized in prolamellar bodies occurring within the proplastids of dark-grown bean leaves. In the process of photoconversion, the highly fluorescent protochlorophyllide is converted to chlorophyll.
Multicellular, eukaryotic life forms of kingdom Plantae (sensu lato), comprising the VIRIDIPLANTAE; RHODOPHYTA; and GLAUCOPHYTA; all of which acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations.

Intrapreoptic microinjection of GHRH or its antagonist alters sleep in rats. (1/2379)

Previous reports indicate that growth hormone-releasing hormone (GHRH) is involved in sleep regulation. The site of action mediating the nonrapid eye movement sleep (NREMS)-promoting effects of GHRH is not known, but it is independent from the pituitary. GHRH (0.001, 0. 01, and 0.1 nmol/kg) or a competitive antagonist of GHRH (0.003, 0.3, and 14 nmol/kg) was microinjected into the preoptic area, and the sleep-wake activity was recorded for 23 hr after injection in rats. GHRH elicited dose-dependent increases in the duration and in the intensity of NREMS compared with that in control records after intrapreoptic injection of physiological saline. The antagonist decreased the duration and intensity of NREMS and prolonged sleep latency. Consistent alterations in rapid eye movement sleep (REMS) and in brain temperature were not found. The GHRH antagonist also attenuated the enhancements in NREMS elicited by 3 hr of sleep deprivation. Histological verification of the injection sites showed that the majority of the effective injections were in the preoptic area and the diagonal band of Broca. The results indicate that the preoptic area mediates the sleep-promoting activity of GHRH.  (+info)

Simulation analysis of the retinal conformational equilibrium in dark-adapted bacteriorhodopsin. (2/2379)

In dark-adapted bacteriorhodopsin (bR) the retinal moiety populates two conformers: all-trans and (13,15)cis. Here we examine factors influencing the thermodynamic equilibrium and conformational transition between the two forms, using molecular mechanics and dynamics calculations. Adiabatic potential energy mapping indicates that whereas the twofold intrinsic torsional potentials of the C13==C14 and C15==N16 double bonds favor a sequential torsional pathway, the protein environment favors a concerted, bicycle-pedal mechanism. Which of these two pathways will actually occur in bR depends on the as yet unknown relative weight of the intrinsic and environmental effects. The free energy difference between the conformers was computed for wild-type and modified bR, using molecular dynamics simulation. In the wild-type protein the free energy of the (13,15)cis retinal form is calculated to be 1.1 kcal/mol lower than the all-trans retinal form, a value within approximately kBT of experiment. In contrast, in isolated retinal the free energy of the all-trans state is calculated to be 2.1 kcal/mol lower than (13,15)cis. The free energy differences are similar to the adiabatic potential energy differences in the various systems examined, consistent with an essentially enthalpic origin. The stabilization of the (13,15)cis form in bR relative to the isolated retinal molecule is found to originate from improved protein-protein interactions. Removing internal water molecules near the Schiff base strongly stabilizes the (13,15)cis form, whereas a double mutation that removes negative charges in the retinal pocket (Asp85 to Ala; Asp212 to Ala) has the opposite effect.  (+info)

Abnormal photoresponses and light-induced apoptosis in rods lacking rhodopsin kinase. (3/2379)

Phosphorylation is thought to be an essential first step in the prompt deactivation of photoexcited rhodopsin. In vitro, the phosphorylation can be catalyzed either by rhodopsin kinase (RK) or by protein kinase C (PKC). To investigate the specific role of RK, we inactivated both alleles of the RK gene in mice. This eliminated the light-dependent phosphorylation of rhodopsin and caused the single-photon response to become larger and longer lasting than normal. These results demonstrate that RK is required for normal rhodopsin deactivation. When the photon responses of RK-/- rods did finally turn off, they did so abruptly and stochastically, revealing a first-order backup mechanism for rhodopsin deactivation. The rod outer segments of RK-/- mice raised in 12-hr cyclic illumination were 50% shorter than those of normal (RK+/+) rods or rods from RK-/- mice raised in constant darkness. One day of constant light caused the rods in the RK-/- mouse retina to undergo apoptotic degeneration. Mice lacking RK provide a valuable model for the study of Oguchi disease, a human RK deficiency that causes congenital stationary night blindness.  (+info)

Loss of the circadian clock-associated protein 1 in Arabidopsis results in altered clock-regulated gene expression. (4/2379)

Little is known about plant circadian oscillators, in spite of how important they are to sessile plants, which require accurate timekeepers that enable the plants to respond to their environment. Previously, we identified a circadian clock-associated (CCA1) gene that encodes an Myb-related protein that is associated with phytochrome control and circadian regulation in plants. To understand the role CCA1 plays in phytochrome and circadian regulation, we have isolated an Arabidopsis line with a T DNA insertion that results in the loss of CCA1 RNA, of CCA1 protein, and of an Lhcb-promoter binding activity. This mutation affects the circadian expression of all four clock-controlled genes that we examined. The results show that, despite their similarity, CCA1 and LHY are only partially redundant. The lack of CCA1 also affects the phytochrome regulation of gene expression, suggesting that CCA1 has an additional role in a signal transduction pathway from light, possibly acting at the point of integration between phytochrome and the clock. Our results indicate that CCA1 is an important clock-associated protein involved in circadian regulation of gene expression.  (+info)

Light-induced oxidation-reduction reactions of cytochromes in the green sulfur photosynthetic bacterium Prosthecochloris aesturarii. (5/2379)

The light-induced oxidation-reduction reactions of cytochromes in intact cells, starved cells, and chlorobium vesicle fractions of the green sulfur photosynthetic bacterium Prosthecochloris aesturarii were studied under anaerobic conditions. On the basis of both kinetic and spectral properties, at least three cytochrome species were found to be involved in the light-induced oxidation-reduction reactions of intact cells. These cytochromes were designated according to the positions of alpha-band maxima as C555 (rapid and slow components) and C552 (intermediate). By comparing the light-minus-dark difference spectra with the reduced-minus-oxidized difference spectra of purified cytochromes of this organism, rapid component C555 and intermediate component C552 are suggested to correspond to the purified cytochromes c-555(550) and c-551.5, respectively. Although the identity of the slow-phase component is uncertain, one possibility is that the slow phase is due to the bound form of c-555(550). In substrate-depleted (starved) cells, only one cytochrome species, C555 remained in the reduced state in the dark and oxidized upon actinic illumination. This corresponds to the rapid C555 component in intact cells. In the case of chlorobium vesicle fractions, one cytochrome species having an alpha-band maximum at 554 nm was oxidized by actinic light. The effects of several inhibitors on the absorbance changes of intact cells were studied. Antimycin A decreased the rate of the dark reduction of rapid C555 component. The complex effects of CCCP (carbonyl cyanide m-chlorophenylhydrazone) on the oxidation-reduction reactions of cytochromes were interpreted as the results of inhibition of the electron donation to oxidized C552 and C555 (slow), and a shift of the dark steady-state redox levels of cytochromes. Based on these findings, it is suggested that the rapid C555 component is located in a cyclic electron transfer pathway. The other two cytochromes, C552 and C555 (slow), may be located in non-cyclic electron transfer pathways and receive electrons from exogenous substrates such as sodium sulfide. A tentative scheme for the electron transfer system in Prosthecochloris aestuarii is presented and its nature is discussed.  (+info)

Modulation of Hydra attenuata rhythmic activity: phase response curve. (6/2379)

We investigated the effect of photic stimulation on the frequency of Hydra attenuata column contractions. We used positive or negative abrupt light transitions, single or repetitive light or darkness pulses, and alternation of light and darkness periods. The main results are: (a) The frequency of the contraction pulse trains (CPTs) varies transiently in response to an abrupt variation of the light intensity. (b) CPTs in progress can be inhibited by different types of photic stimuli. (c) The response time to a single photic stimulus varies during the inter-CPT interval and depends also on the polarity of the stimulus. (d) The CPTs are entrainable with repetitive light stimulation of various frequencies. (e) Long-lasting variations of the frequency of CPTs occur after the end of a repetitive light stimulation. We suggest that the mechanism responsible for the rhythym of column contractions is quite similar to that on which other biological rhythmic phenomena are based.  (+info)

The relation between intercellular coupling and electrical noise in turtle photoreceptors. (7/2379)

1. Intracellular recordings from cones and rods in the retina of the turtle, Pseudemys scripta elegans, revealed that in darkness the cell voltage fluctuated spontaneously about its mean level. The fluctuations were reduced during bright steady illmination of the cell often to a level close to that obtained with the electrode outside the cell where the noise did not change significantly during illumination. 2. The magnitude of the intrinsic dark noise (voltage variance in darkness minus voltage variance in strong light) varied widely from cell to cell. In the noisiest cones it was about 0-4 mV2 while in quiet cones it was often as low as 0-01 mV2. The noise appeared radom and could be fitted by a Gaussian probability density function. 3. The spread of voltage in the network of coupled photoreceptors was estimated by measuring the spatial profile of the response to a brief flash of constant intensity moved across the retina. For a light stimulus in the form of a long narrow slit, the peak flash response usually decayed exponentially with displacement from the centred position. 4. For maximum responses less than about 5 mV in cones, the length constant of exponential decay, lambda, varied from less than 10 mum to greater than 35 mum, and the values obtained in opposite directions were often unequal. Background illumination did not significantly change lambda. In cells with extremely narrow spatial profiles, an exponential fit to the decay could not be made reliably. 5. Occasionally the spatial profiles had definite secondary peaks. In the most pronounced examples in a red-sensitive cone and in a rod the maxima were separated by about 20 and 50 mum respectively; for each, one peak was approximately as sharp as the optical stimulator while the second was broader. 6. Cones with short length constants displayed high dark noise while cones with long length constants were relatively quiet. 7. Three models of electrical coupling between cells were investigated: one based on a distributed network, one on a discrete square grid arrangement, and one on a discrete hexagonal array. Each model predicts a strong dependence of both noise and input resistance on length constant, and for tightly coupled cells each predicts that voltage variance is proportional to lambda-2. 8. The measured relationship between voltage variance and lambda in a large sample of cones was well described by both discrete models when the average cell spacing was taken to be approximately 15 mum. 9...  (+info)

The prenylation status of a novel plant calmodulin directs plasma membrane or nuclear localization of the protein. (8/2379)

Post-translational attachment of isoprenyl groups to conserved cysteine residues at the C-terminus of a number of regulatory proteins is important for their function and subcellular localization. We have identified a novel calmodulin, CaM53, with an extended C-terminal basic domain and a CTIL CaaX-box motif which are required for efficient prenylation of the protein in vitro and in vivo. Ectopic expression of wild-type CaM53 or a non-prenylated mutant protein in plants causes distinct morphological changes. Prenylated CaM53 associates with the plasma membrane, but the non-prenylated mutant protein localizes to the nucleus, indicating a dual role for the C-terminal domain. The subcellular localization of CaM53 can be altered by a block in isoprenoid biosynthesis or sugar depletion, suggesting that CaM53 activates different targets in response to metabolic changes. Thus, prenylation of CaM53 appears to be a novel mechanism by which plant cells can coordinate Ca2+ signaling with changes in metabolic activities.  (+info)

I am not aware of a medical definition for the term "darkness." In general, darkness refers to the absence of light. It is not a term that is commonly used in the medical field, and it does not have a specific clinical meaning. If you have a question about a specific medical term or concept, I would be happy to try to help you understand it.

In the context of medical terminology, "light" doesn't have a specific or standardized definition on its own. However, it can be used in various medical terms and phrases. For example, it could refer to:

1. Visible light: The range of electromagnetic radiation that can be detected by the human eye, typically between wavelengths of 400-700 nanometers. This is relevant in fields such as ophthalmology and optometry.
2. Therapeutic use of light: In some therapies, light is used to treat certain conditions. An example is phototherapy, which uses various wavelengths of ultraviolet (UV) or visible light for conditions like newborn jaundice, skin disorders, or seasonal affective disorder.
3. Light anesthesia: A state of reduced consciousness in which the patient remains responsive to verbal commands and physical stimulation. This is different from general anesthesia where the patient is completely unconscious.
4. Pain relief using light: Certain devices like transcutaneous electrical nerve stimulation (TENS) units have a 'light' setting, indicating lower intensity or frequency of electrical impulses used for pain management.

Without more context, it's hard to provide a precise medical definition of 'light'.

A circadian rhythm is a roughly 24-hour biological cycle that regulates various physiological and behavioral processes in living organisms. It is driven by the body's internal clock, which is primarily located in the suprachiasmatic nucleus (SCN) of the hypothalamus in the brain.

The circadian rhythm controls many aspects of human physiology, including sleep-wake cycles, hormone secretion, body temperature, and metabolism. It helps to synchronize these processes with the external environment, particularly the day-night cycle caused by the rotation of the Earth.

Disruptions to the circadian rhythm can have negative effects on health, leading to conditions such as insomnia, sleep disorders, depression, bipolar disorder, and even increased risk of chronic diseases like cancer, diabetes, and cardiovascular disease. Factors that can disrupt the circadian rhythm include shift work, jet lag, irregular sleep schedules, and exposure to artificial light at night.

Dark adaptation is the process by which the eyes adjust to low levels of light. This process allows the eyes to become more sensitive to light and see better in the dark. It involves the dilation of the pupils, as well as chemical changes in the rods and cones (photoreceptor cells) of the retina. These changes allow the eye to detect even small amounts of light and improve visual acuity in low-light conditions. Dark adaptation typically takes several minutes to occur fully, but can be faster or slower depending on various factors such as age, prior exposure to light, and certain medical conditions. It is an important process for maintaining good vision in a variety of lighting conditions.

Photoperiod is a term used in chronobiology, which is the study of biological rhythms and their synchronization with environmental cycles. In medicine, photoperiod specifically refers to the duration of light and darkness in a 24-hour period, which can significantly impact various physiological processes in living organisms, including humans.

In human medicine, photoperiod is often considered in relation to circadian rhythms, which are internal biological clocks that regulate several functions such as sleep-wake cycles, hormone secretion, and metabolism. The length of the photoperiod can influence these rhythms and contribute to the development or management of certain medical conditions, like mood disorders, sleep disturbances, and metabolic disorders.

For instance, exposure to natural daylight or artificial light sources with specific intensities and wavelengths during particular times of the day can help regulate circadian rhythms and improve overall health. Conversely, disruptions in the photoperiod due to factors like shift work, jet lag, or artificial lighting can lead to desynchronization of circadian rhythms and related health issues.

Photoreceptor cells are specialized neurons in the retina of the eye that convert light into electrical signals. These cells consist of two types: rods and cones. Rods are responsible for vision at low light levels and provide black-and-white, peripheral, and motion sensitivity. Cones are active at higher light levels and are capable of color discrimination and fine detail vision. Both types of photoreceptor cells contain light-sensitive pigments that undergo chemical changes when exposed to light, triggering a series of electrical signals that ultimately reach the brain and contribute to visual perception.

Chronobiology disorders are a group of conditions that involve disruptions in the body's internal biological clock, which regulates various physiological processes such as sleep-wake cycles, hormone release, and metabolism. These disorders can result in a variety of symptoms, including difficulty sleeping, changes in mood and energy levels, and problems with cognitive function.

Some common examples of chronobiology disorders include:

1. Delayed Sleep Phase Syndrome (DSPS): This condition is characterized by a persistent delay in the timing of sleep, so that an individual's preferred bedtime is significantly later than what is considered normal. As a result, they may have difficulty falling asleep and waking up at socially acceptable times.
2. Advanced Sleep Phase Syndrome (ASPS): In this condition, individuals experience an earlier-than-normal timing of sleep, so that they become sleepy and wake up several hours earlier than most people.
3. Non-24-Hour Sleep-Wake Rhythm Disorder: This disorder is characterized by a persistent mismatch between the individual's internal biological clock and the 24-hour day, resulting in irregular sleep-wake patterns that can vary from day to day.
4. Irregular Sleep-Wake Rhythm Disorder: In this condition, individuals experience a lack of consistent sleep-wake patterns, with multiple periods of sleep and wakefulness throughout the 24-hour day.
5. Shift Work Sleep Disorder: This disorder is caused by the disruption of normal sleep-wake patterns due to working irregular hours, such as night shifts or rotating schedules.
6. Jet Lag Disorder: This condition occurs when an individual travels across time zones and experiences a temporary mismatch between their internal biological clock and the new local time.

Treatment for chronobiology disorders may include lifestyle changes, such as adjusting sleep schedules and exposure to light, as well as medications that can help regulate sleep-wake cycles. In some cases, cognitive-behavioral therapy (CBT) may also be helpful in managing these conditions.

The pineal gland, also known as the epiphysis cerebri, is a small endocrine gland located in the brain. It is shaped like a pinecone, hence its name, and is situated near the center of the brain, between the two hemispheres, attached to the third ventricle. The primary function of the pineal gland is to produce melatonin, a hormone that helps regulate sleep-wake cycles and circadian rhythms in response to light and darkness. Additionally, it plays a role in the onset of puberty and has been suggested to have other functions related to cognition, mood, and reproduction, although these are not as well understood.

The suprachiasmatic nucleus (SCN) is a small region located in the hypothalamus of the brain, just above the optic chiasm where the optic nerves from each eye cross. It is considered to be the primary circadian pacemaker in mammals, responsible for generating and maintaining the body's internal circadian rhythm, which is a roughly 24-hour cycle that regulates various physiological processes such as sleep-wake cycles, hormone release, and metabolism.

The SCN receives direct input from retinal ganglion cells, which are sensitive to light and dark signals. This information helps the SCN synchronize the internal circadian rhythm with the external environment, allowing it to adjust to changes in day length and other environmental cues. The SCN then sends signals to other parts of the brain and body to regulate various functions according to the time of day.

Disruption of the SCN's function can lead to a variety of circadian rhythm disorders, such as jet lag, shift work disorder, and advanced or delayed sleep phase syndrome.

I'm sorry for any confusion, but "lighting" does not have a specific medical definition. In a general context, lighting refers to the arrangement or use of light sources to achieve a particular effect or atmosphere. However, if you are referring to a term in medicine that may be similar to "lighting," you might be thinking of "lumination" or "illumination," which refer to the act of providing or admitting light, especially for medical examination or surgical procedures. I hope this helps! If you have any other questions, please don't hesitate to ask.

A vestibulo-ocular reflex (VOR) is a automatic motion of the eyes that helps to stabilize images on the retina during head movement. It is mediated by the vestibular system, which includes the semicircular canals and otolith organs in the inner ear.

When the head moves, the movement is detected by the vestibular system, which sends signals to the oculomotor nuclei in the brainstem. These nuclei then generate an eye movement that is equal and opposite to the head movement, allowing the eyes to remain fixed on a target while the head is moving. This reflex helps to maintain visual stability during head movements and is essential for activities such as reading, walking, and driving.

The VOR can be tested clinically by having the patient follow a target with their eyes while their head is moved passively. If the VOR is functioning properly, the eyes should remain fixed on the target despite the head movement. Abnormalities in the VOR can indicate problems with the vestibular system or the brainstem.

Ocular adaptation is the ability of the eye to adjust and accommodate to changes in visual input and lighting conditions. This process allows the eye to maintain a clear and focused image over a range of different environments and light levels. There are several types of ocular adaptation, including:

1. Light Adaptation: This refers to the eye's ability to adjust to different levels of illumination. When moving from a dark environment to a bright one, the pupils constrict to let in less light, and the sensitivity of the retina decreases. Conversely, when moving from a bright environment to a dark one, the pupils dilate to let in more light, and the sensitivity of the retina increases.
2. Dark Adaptation: This is the process by which the eye adjusts to low light conditions. It involves the dilation of the pupils and an increase in the sensitivity of the rods (specialised cells in the retina that are responsible for vision in low light conditions). Dark adaptation can take several minutes to occur fully.
3. Color Adaptation: This refers to the eye's ability to adjust to changes in the color temperature of light sources. For example, when moving from a room lit by incandescent light to one lit by fluorescent light, the eye may need to adjust its perception of colors to maintain accurate color vision.
4. Accommodation: This is the process by which the eye changes focus from distant to near objects. The lens of the eye changes shape to bend the light rays entering the eye and bring them into sharp focus on the retina.

Overall, ocular adaptation is an essential function that allows us to see clearly and accurately in a wide range of environments and lighting conditions.

I believe there may be some confusion in your question as "caves" are not a medical term. A cave is a natural underground space that is large enough for a person to enter and can form in a variety of ways, such as the dissolution of limestone by acidic groundwater or the collapse of a volcanic tube. If you have any questions about geology or speleology (the study of caves), I would be happy to try to help answer those!

Melatonin is a hormone that is produced by the pineal gland in the brain. It helps regulate sleep-wake cycles and is often referred to as the "hormone of darkness" because its production is stimulated by darkness and inhibited by light. Melatonin plays a key role in synchronizing the circadian rhythm, the body's internal clock that regulates various biological processes over a 24-hour period.

Melatonin is primarily released at night, and its levels in the blood can rise and fall in response to changes in light and darkness in an individual's environment. Supplementing with melatonin has been found to be helpful in treating sleep disorders such as insomnia, jet lag, and delayed sleep phase syndrome. It may also have other benefits, including antioxidant properties and potential uses in the treatment of certain neurological conditions.

It is important to note that while melatonin supplements are available over-the-counter in many countries, they should still be used under the guidance of a healthcare professional, as their use can have potential side effects and interactions with other medications.

I'm sorry for any confusion, but "perches" is not a term commonly used in medical terminology. It is most often used to refer to a place where a bird or small animal perches, or in measurements of height (such as "perches above ground"). If you have any questions about a medical term or concept, I would be happy to help clarify!

Phytochrome is a photoreceptor protein responsible for detecting and mediating responses to different wavelengths of light, primarily red and far-red, in plants and some microorganisms. It plays a crucial role in various physiological processes such as seed germination, stem elongation, leaf expansion, chlorophyll production, and flowering.

The phytochrome protein exists in two interconvertible forms: Pr (the red-light-absorbing form) and Pfr (the far-red-light-absorbing form). The conversion between these forms regulates the downstream signaling pathways that control plant growth and development. Red light (around 660 nm) promotes the formation of the Pfr form, while far-red light (around 730 nm) converts it back to the Pr form. This reversible photoresponse allows plants to adapt their growth patterns based on the quality and duration of light they receive.

"Biological clocks" refer to the internal time-keeping systems in living organisms that regulate the timing of various physiological processes and behaviors according to a daily (circadian) rhythm. These rhythms are driven by genetic mechanisms and can be influenced by environmental factors such as light and temperature.

In humans, biological clocks help regulate functions such as sleep-wake cycles, hormone release, body temperature, and metabolism. Disruptions to these internal timekeeping systems have been linked to various health problems, including sleep disorders, mood disorders, and cognitive impairment.

Period (PER) circadian proteins are a group of proteins that play a crucial role in the regulation of circadian rhythms, which are physical, mental, and behavioral changes that follow a daily cycle. They are named after the PERIOD gene, whose protein product is one of the key components of the molecular circadian clock mechanism.

The molecular clock is a self-sustaining oscillator present in most organisms, from cyanobacteria to humans. In mammals, the molecular clock consists of two interlocking transcriptional-translational feedback loops that generate rhythmic expression of clock genes and their protein products with a period of approximately 24 hours.

The primary loop involves the positive regulators CLOCK and BMAL1, which heterodimerize and bind to E-box elements in the promoter regions of target genes, including PERIOD (PER) and CRYPTOCHROME (CRY) genes. Upon transcription and translation, PER and CRY proteins form a complex that translocates back into the nucleus, where it inhibits CLOCK-BMAL1-mediated transcription, thereby suppressing its own expression. After a certain period, the repressive complex dissociates, allowing for another cycle of transcription and translation to occur.

The second loop involves the regulation of additional clock genes such as REV-ERBα and RORα, which compete for binding to ROR response elements (ROREs) in the BMAL1 promoter, thereby modulating its expression level. REV-ERBα also represses PER and CRY transcription by recruiting histone deacetylases (HDACs) and nuclear receptor corepressor 1 (NCOR1).

Overall, Period circadian proteins are essential for the proper functioning of the molecular clock and the regulation of various physiological processes, including sleep-wake cycles, metabolism, hormone secretion, and cellular homeostasis. Dysregulation of these proteins has been implicated in several diseases, such as sleep disorders, metabolic syndromes, and cancer.

The retina is the innermost, light-sensitive layer of tissue in the eye of many vertebrates and some cephalopods. It receives light that has been focused by the cornea and lens, converts it into neural signals, and sends these to the brain via the optic nerve. The retina contains several types of photoreceptor cells including rods (which handle vision in low light) and cones (which are active in bright light and are capable of color vision).

In medical terms, any pathological changes or diseases affecting the retinal structure and function can lead to visual impairment or blindness. Examples include age-related macular degeneration, diabetic retinopathy, retinal detachment, and retinitis pigmentosa among others.

Physiologic nystagmus is a type of normal, involuntary eye movement that occurs in certain situations. It is characterized by rhythmical to-and-fro movements of the eyes, which can be horizontal, vertical, or rotatory. The most common form of physiologic nystagmus is called "optokinetic nystagmus," which occurs when a person looks at a moving pattern, such as stripes on a rotating drum or scenery passing by a car window.

Optokinetic nystagmus helps to stabilize the image of the environment on the retina and allows the brain to perceive motion accurately. Another form of physiologic nystagmus is "pursuit nystagmus," which occurs when the eyes attempt to follow a slowly moving target. In this case, the eyes may overshoot the target and then make a corrective movement in the opposite direction.

Physiologic nystagmus is different from pathological nystagmus, which can be caused by various medical conditions such as brain damage, inner ear disorders, or medications that affect the nervous system. Pathological nystagmus may indicate a serious underlying condition and should be evaluated by a healthcare professional.

Photic stimulation is a medical term that refers to the exposure of the eyes to light, specifically repetitive pulses of light, which is used as a method in various research and clinical settings. In neuroscience, it's often used in studies related to vision, circadian rhythms, and brain function.

In a clinical context, photic stimulation is sometimes used in the diagnosis of certain medical conditions such as seizure disorders (like epilepsy). By observing the response of the brain to this light stimulus, doctors can gain valuable insights into the functioning of the brain and the presence of any neurological disorders.

However, it's important to note that photic stimulation should be conducted under the supervision of a trained healthcare professional, as improper use can potentially trigger seizures in individuals who are susceptible to them.

Chlorophyll is a green pigment found in the chloroplasts of photosynthetic plants, algae, and some bacteria. It plays an essential role in light-dependent reactions of photosynthesis by absorbing light energy, primarily from the blue and red parts of the electromagnetic spectrum, and converting it into chemical energy to fuel the synthesis of carbohydrates from carbon dioxide and water. The structure of chlorophyll includes a porphyrin ring, which binds a central magnesium ion, and a long phytol tail. There are several types of chlorophyll, including chlorophyll a and chlorophyll b, which have distinct absorption spectra and slightly different structures. Chlorophyll is crucial for the process of photosynthesis, enabling the conversion of sunlight into chemical energy and the release of oxygen as a byproduct.

Diuron is a pesticide and herbicide that is used to control weeds in various settings, such as agriculture, landscaping, and forestry. Its chemical name is 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Diuron works by inhibiting photosynthesis in plants, which prevents them from growing and eventually kills them.

While diuron is effective at controlling weeds, it can also have harmful effects on non-target organisms, including aquatic life and pollinators. Additionally, there are concerns about the potential for diuron to contaminate water sources and pose risks to human health. As a result, its use is regulated in many countries, and there are restrictions on how it can be applied and disposed of.

It's worth noting that Diuron is not a medical term or a drug used for treating any medical condition in humans or animals.

Ocular vision refers to the ability to process and interpret visual information that is received by the eyes. This includes the ability to see clearly and make sense of the shapes, colors, and movements of objects in the environment. The ocular system, which includes the eye and related structures such as the optic nerve and visual cortex of the brain, works together to enable vision.

There are several components of ocular vision, including:

* Visual acuity: the clarity or sharpness of vision
* Field of vision: the extent of the visual world that is visible at any given moment
* Color vision: the ability to distinguish different colors
* Depth perception: the ability to judge the distance of objects in three-dimensional space
* Contrast sensitivity: the ability to distinguish an object from its background based on differences in contrast

Disorders of ocular vision can include refractive errors such as nearsightedness or farsightedness, as well as more serious conditions such as cataracts, glaucoma, and macular degeneration. These conditions can affect one or more aspects of ocular vision and may require medical treatment to prevent further vision loss.

Retinal rod photoreceptor cells are specialized neurons in the retina of the eye that are primarily responsible for vision in low light conditions. They contain a light-sensitive pigment called rhodopsin, which undergoes a chemical change when struck by a single photon of light. This triggers a cascade of biochemical reactions that ultimately leads to the generation of electrical signals, which are then transmitted to the brain via the optic nerve.

Rod cells do not provide color vision or fine detail, but they allow us to detect motion and see in dim light. They are more sensitive to light than cone cells, which are responsible for color vision and detailed sight in bright light conditions. Rod cells are concentrated at the outer edges of the retina, forming a crescent-shaped region called the peripheral retina, with fewer rod cells located in the central region of the retina known as the fovea.

Eye movements, also known as ocular motility, refer to the voluntary or involuntary motion of the eyes that allows for visual exploration of our environment. There are several types of eye movements, including:

1. Saccades: rapid, ballistic movements that quickly shift the gaze from one point to another.
2. Pursuits: smooth, slow movements that allow the eyes to follow a moving object.
3. Vergences: coordinated movements of both eyes in opposite directions, usually in response to a three-dimensional stimulus.
4. Vestibulo-ocular reflex (VOR): automatic eye movements that help stabilize the gaze during head movement.
5. Optokinetic nystagmus (OKN): rhythmic eye movements that occur in response to large moving visual patterns, such as when looking out of a moving vehicle.

Abnormalities in eye movements can indicate neurological or ophthalmological disorders and are often assessed during clinical examinations.

The vestibular system is a part of the inner ear that contributes to our sense of balance and spatial orientation. It is made up of two main components: the vestibule and the labyrinth.

The vestibule is a bony chamber in the inner ear that contains two important structures called the utricle and saccule. These structures contain hair cells and fluid-filled sacs that help detect changes in head position and movement, allowing us to maintain our balance and orientation in space.

The labyrinth, on the other hand, is a more complex structure that includes the vestibule as well as three semicircular canals. These canals are also filled with fluid and contain hair cells that detect rotational movements of the head. Together, the vestibule and labyrinth work together to provide us with information about our body's position and movement in space.

Overall, the vestibular system plays a crucial role in maintaining our balance, coordinating our movements, and helping us navigate through our environment.

A hypocotyl is not a medical term per se, but it is a term used in the field of botany, which is a branch of biology that deals with the study of plants. Therefore, I'd be happy to provide you with a definition of hypocotyl in a botanical context:

The hypocotyl is the portion of the embryo or seedling of a plant that lies between the cotyledons (the embryonic leaves) and the radicle (the embryonic root). In other words, it is the stem-like structure that connects the shoot and the root systems in a developing plant.

When a seed germinates, the hypocotyl elongates and pushes the cotyledons upward through the soil, allowing the young plant to emerge into the light. The hypocotyl can vary in length depending on the species of plant, and its growth is influenced by various environmental factors such as light and temperature.

While the term "hypocotyl" may not be commonly used in medical contexts, understanding basic botanical concepts like this one can still be useful for healthcare professionals who work with patients who have plant-related allergies or other health issues related to plants.

'Activity cycles' is a term that can have different meanings in different contexts, and I could not find a specific medical definition for it. However, in the context of physiology or chronobiology, activity cycles often refer to the natural rhythms of behavior and physiological processes that occur over a 24-hour period, also known as circadian rhythms.

Circadian rhythms are biological processes that follow an approximate 24-hour cycle and regulate various functions in living organisms, including sleep-wake cycles, body temperature, hormone secretion, and metabolism. These rhythms help the body adapt to the changing environment and coordinate various physiological processes to optimize function and maintain homeostasis.

Therefore, activity cycles in a medical or physiological context may refer to the natural fluctuations in physical activity, alertness, and other behaviors that follow a circadian rhythm. Factors such as sleep deprivation, jet lag, and shift work can disrupt these rhythms and lead to various health problems, including sleep disorders, mood disturbances, and impaired cognitive function.

Cryptochromes are a type of photoreceptor protein found in plants and animals, including humans. They play a crucial role in regulating various biological processes such as circadian rhythms (the internal "body clock" that regulates sleep-wake cycles), DNA repair, and magnetoreception (the ability to perceive magnetic fields).

In humans, cryptochromes are primarily expressed in the retina of the eye and in various tissues throughout the body. They contain a light-sensitive cofactor called flavin adenine dinucleotide (FAD) that allows them to absorb blue light and convert it into chemical signals. These signals then interact with other proteins and signaling pathways to regulate gene expression and cellular responses.

In plants, cryptochromes are involved in the regulation of growth and development, including seed germination, stem elongation, and flowering time. They also play a role in the plant's ability to sense and respond to changes in light quality and duration, which is important for optimizing photosynthesis and survival.

Overall, cryptochromes are an essential component of many biological processes and have been the subject of extensive research in recent years due to their potential roles in human health and disease.

Retinal cone photoreceptor cells are specialized neurons located in the retina of the eye, responsible for visual phototransduction and color vision. They are one of the two types of photoreceptors, with the other being rods, which are more sensitive to low light levels. Cones are primarily responsible for high-acuity, color vision during daylight or bright-light conditions.

There are three types of cone cells, each containing different photopigments that absorb light at distinct wavelengths: short (S), medium (M), and long (L) wavelengths, which correspond to blue, green, and red light, respectively. The combination of signals from these three types of cones allows the human visual system to perceive a wide range of colors and discriminate between them. Cones are densely packed in the central region of the retina, known as the fovea, which provides the highest visual acuity.

In the context of medicine, particularly in anatomy and physiology, "rotation" refers to the movement of a body part around its own axis or the long axis of another structure. This type of motion is three-dimensional and can occur in various planes. A common example of rotation is the movement of the forearm bones (radius and ulna) around each other during pronation and supination, which allows the hand to be turned palm up or down. Another example is the rotation of the head during mastication (chewing), where the mandible moves in a circular motion around the temporomandibular joint.

'Arabidopsis' is a genus of small flowering plants that are part of the mustard family (Brassicaceae). The most commonly studied species within this genus is 'Arabidopsis thaliana', which is often used as a model organism in plant biology and genetics research. This plant is native to Eurasia and Africa, and it has a small genome that has been fully sequenced. It is known for its short life cycle, self-fertilization, and ease of growth, making it an ideal subject for studying various aspects of plant biology, including development, metabolism, and response to environmental stresses.

A pupillary reflex is a type of reflex that involves the constriction or dilation of the pupils in response to changes in light or near vision. It is mediated by the optic and oculomotor nerves. The pupillary reflex helps regulate the amount of light that enters the eye, improving visual acuity and protecting the retina from excessive light exposure.

In a clinical setting, the pupillary reflex is often assessed as part of a neurological examination. A normal pupillary reflex consists of both direct and consensual responses. The direct response occurs when light is shone into one eye and the pupil of that same eye constricts. The consensual response occurs when light is shone into one eye, causing the pupil of the other eye to also constrict.

Abnormalities in the pupillary reflex can indicate various neurological conditions, such as brainstem injuries or diseases affecting the optic or oculomotor nerves.

Photosynthesis is not strictly a medical term, but it is a fundamental biological process with significant implications for medicine, particularly in understanding energy production in cells and the role of oxygen in sustaining life. Here's a general biological definition:

Photosynthesis is a process by which plants, algae, and some bacteria convert light energy, usually from the sun, into chemical energy in the form of organic compounds, such as glucose (or sugar), using water and carbon dioxide. This process primarily takes place in the chloroplasts of plant cells, specifically in structures called thylakoids. The overall reaction can be summarized as:

6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2

In this equation, carbon dioxide (CO2) and water (H2O) are the reactants, while glucose (C6H12O6) and oxygen (O2) are the products. Photosynthesis has two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle). The light-dependent reactions occur in the thylakoid membrane and involve the conversion of light energy into ATP and NADPH, which are used to power the Calvin cycle. The Calvin cycle takes place in the stroma of chloroplasts and involves the synthesis of glucose from CO2 and water using the ATP and NADPH generated during the light-dependent reactions.

Understanding photosynthesis is crucial for understanding various biological processes, including cellular respiration, plant metabolism, and the global carbon cycle. Additionally, research into artificial photosynthesis has potential applications in renewable energy production and environmental remediation.

"Ocular physiological phenomena" is not a standardized medical term with a specific definition. However, I can provide some examples of ocular physiological phenomena, which refer to various normal functions and processes that occur in the eye. Here are a few examples:

1. Accommodation: The ability of the eye to change optical power to maintain a clear image or focus on an object as its distance varies. This is primarily achieved by changing the curvature of the lens through the action of the ciliary muscles.
2. Pupillary reflex: The automatic adjustment of the pupil's size in response to changes in light intensity. In bright light, the pupil constricts (miosis), while in dim light, it dilates (mydriasis). This reflex helps regulate the amount of light that enters the eye.
3. Tear production: The continuous secretion of tears by the lacrimal glands to keep the eyes moist and protected from dust, microorganisms, and other foreign particles.
4. Extraocular muscle function: The coordinated movement of the six extraocular muscles that control eyeball rotation and enable various gaze directions.
5. Color vision: The ability to perceive and distinguish different colors based on the sensitivity of photoreceptor cells (cones) in the retina to specific wavelengths of light.
6. Dark adaptation: The process by which the eyes adjust to low-light conditions, improving visual sensitivity primarily through changes in the rod photoreceptors' sensitivity and pupil dilation.
7. Light adaptation: The ability of the eye to adjust to different levels of illumination, mainly through alterations in pupil size and photoreceptor cell response.

These are just a few examples of ocular physiological phenomena. There are many more processes and functions that occur within the eye, contributing to our visual perception and overall eye health.

I believe there may be a slight misunderstanding in your question. "Plant leaves" are not a medical term, but rather a general biological term referring to a specific organ found in plants.

Leaves are organs that are typically flat and broad, and they are the primary site of photosynthesis in most plants. They are usually green due to the presence of chlorophyll, which is essential for capturing sunlight and converting it into chemical energy through photosynthesis.

While leaves do not have a direct medical definition, understanding their structure and function can be important in various medical fields, such as pharmacognosy (the study of medicinal plants) or environmental health. For example, certain plant leaves may contain bioactive compounds that have therapeutic potential, while others may produce allergens or toxins that can impact human health.

Photophobia is a condition characterized by an abnormal sensitivity to light. It's not a fear of light, despite the name suggesting otherwise. Instead, it refers to the discomfort or pain felt in the eyes due to exposure to light, often leading to a strong desire to avoid light. This can include both natural and artificial light sources.

The severity of photophobia can vary greatly among individuals. Some people may only experience mild discomfort in bright light conditions, while others may find even moderate levels of light intolerable. It can be a symptom of various underlying health issues, including eye diseases or disorders like uveitis, keratitis, corneal abrasions, or optic neuritis, as well as systemic conditions such as migraines, meningitis, or certain medications that increase light sensitivity.

Circadian clocks are biological systems found in living organisms that regulate the daily rhythmic activities and functions with a period of approximately 24 hours. These internal timekeeping mechanisms control various physiological processes, such as sleep-wake cycles, hormone secretion, body temperature, and metabolism, aligning them with the external environment's light-dark cycle.

The circadian clock consists of two major components: the central or master clock, located in the suprachiasmatic nucleus (SCN) of the hypothalamus in mammals, and peripheral clocks present in nearly every cell throughout the body. The molecular mechanisms underlying these clocks involve interconnected transcriptional-translational feedback loops of several clock genes and their protein products. These genetic components generate rhythmic oscillations that drive the expression of clock-controlled genes (CCGs), which in turn regulate numerous downstream targets responsible for coordinating daily physiological and behavioral rhythms.

Circadian clocks can be synchronized or entrained to external environmental cues, mainly by light exposure. This allows organisms to adapt their internal timekeeping to the changing day-night cycles and maintain proper synchronization with the environment. Desynchronization between the internal circadian system and external environmental factors can lead to various health issues, including sleep disorders, mood disturbances, cognitive impairment, metabolic dysregulation, and increased susceptibility to diseases.

Head movements refer to the voluntary or involuntary motion of the head in various directions. These movements can occur in different planes, including flexion (moving the head forward), extension (moving the head backward), rotation (turning the head to the side), and lateral bending (leaning the head to one side).

Head movements can be a result of normal physiological processes, such as when nodding in agreement or shaking the head to indicate disagreement. They can also be caused by neurological conditions, such as abnormal head movements in patients with Parkinson's disease or cerebellar disorders. Additionally, head movements may occur in response to sensory stimuli, such as turning the head toward a sound.

In a medical context, an examination of head movements can provide important clues about a person's neurological function and help diagnose various conditions affecting the brain and nervous system.

Phytochrome A is a type of phytochrome, which is a photoreceptor protein that plants use to detect and respond to different wavelengths of light. Specifically, phytochrome A is responsible for mediating the response to red light. It exists in two interconvertible forms: Pr (the inactive form, absorbing red light) and Pfr (the active form, absorbing far-red light). The conversion between these two forms triggers a range of physiological responses in plants, such as seed germination, stem elongation, leaf expansion, and flowering. Phytochrome A is the most sensitive phytochrome to changes in light quality and quantity, making it a crucial photoreceptor for plants' adaptation to their environment.

Arabidopsis proteins refer to the proteins that are encoded by the genes in the Arabidopsis thaliana plant, which is a model organism commonly used in plant biology research. This small flowering plant has a compact genome and a short life cycle, making it an ideal subject for studying various biological processes in plants.

Arabidopsis proteins play crucial roles in many cellular functions, such as metabolism, signaling, regulation of gene expression, response to environmental stresses, and developmental processes. Research on Arabidopsis proteins has contributed significantly to our understanding of plant biology and has provided valuable insights into the molecular mechanisms underlying various agronomic traits.

Some examples of Arabidopsis proteins include transcription factors, kinases, phosphatases, receptors, enzymes, and structural proteins. These proteins can be studied using a variety of techniques, such as biochemical assays, protein-protein interaction studies, and genetic approaches, to understand their functions and regulatory mechanisms in plants.

Gene expression regulation in plants refers to the processes that control the production of proteins and RNA from the genes present in the plant's DNA. This regulation is crucial for normal growth, development, and response to environmental stimuli in plants. It can occur at various levels, including transcription (the first step in gene expression, where the DNA sequence is copied into RNA), RNA processing (such as alternative splicing, which generates different mRNA molecules from a single gene), translation (where the information in the mRNA is used to produce a protein), and post-translational modification (where proteins are chemically modified after they have been synthesized).

In plants, gene expression regulation can be influenced by various factors such as hormones, light, temperature, and stress. Plants use complex networks of transcription factors, chromatin remodeling complexes, and small RNAs to regulate gene expression in response to these signals. Understanding the mechanisms of gene expression regulation in plants is important for basic research, as well as for developing crops with improved traits such as increased yield, stress tolerance, and disease resistance.

An ecotype is a population of a species that is adapted to specific environmental conditions and exhibits genetic differences from other populations of the same species that live in different environments. These genetic adaptations allow the ecotype to survive and reproduce more successfully in its particular habitat compared to other populations. The term "ecotype" was first introduced by botanist John Gregor Mendel in 1870 to describe the variation within plant species due to environmental factors.

Ecotypes can be found in various organisms, including plants, animals, and microorganisms. They are often studied in ecology and evolutionary biology to understand how genetic differences arise and evolve in response to environmental pressures. Ecotypes can differ from each other in traits such as morphology, physiology, behavior, and life history strategies.

Examples of ecotypes include:

* Desert and coastal ecotypes of the lizard Uta stansburiana, which show differences in body size, limb length, and reproductive strategies due to adaptation to different habitats.
* Arctic and alpine ecotypes of the plant Arabis alpina, which have distinct flowering times and cold tolerance mechanisms that help them survive in their respective environments.
* Freshwater and marine ecotypes of the copepod Eurytemora affinis, which differ in body size, developmental rate, and salinity tolerance due to adaptation to different aquatic habitats.

It is important to note that the concept of ecotype is not always clearly defined or consistently applied in scientific research. Some researchers use it to describe any population that shows genetic differences related to environmental factors, while others reserve it for cases where there is strong evidence of local adaptation and reproductive isolation between populations.

A pupil, in medical terms, refers to the circular opening in the center of the iris (the colored part of the eye) that allows light to enter and reach the retina. The size of the pupil can change involuntarily in response to light intensity and emotional state, as well as voluntarily through certain eye exercises or with the use of eye drops. Pupillary reactions are important in clinical examinations as they can provide valuable information about the nervous system's functioning, particularly the brainstem and cranial nerves II and III.

Urodela is not a medical term, but a taxonomic category in the field of biology. It refers to a group of amphibians commonly known as newts and salamanders. These creatures are characterized by their slender bodies, moist skin, and four legs. They undergo a process of metamorphosis during their development, transitioning from an aquatic larval stage to a terrestrial adult stage.

While not a medical term itself, understanding the biology and ecology of Urodela can be relevant in fields such as environmental health and toxicology, where these animals may serve as indicators of ecosystem health or potential subjects for studying the effects of pollutants on living organisms.

In a medical context, "orientation" typically refers to an individual's awareness and understanding of their personal identity, place, time, and situation. It is a critical component of cognitive functioning and mental status. Healthcare professionals often assess a person's orientation during clinical evaluations, using tests that inquire about their name, location, the current date, and the circumstances of their hospitalization or visit.

There are different levels of orientation:

1. Person (or self): The individual knows their own identity, including their name, age, and other personal details.
2. Place: The individual is aware of where they are, such as the name of the city, hospital, or healthcare facility.
3. Time: The individual can accurately state the current date, day of the week, month, and year.
4. Situation or event: The individual understands why they are in the healthcare setting, what happened leading to their hospitalization or visit, and the nature of any treatments or procedures they are undergoing.

Impairments in orientation can be indicative of various neurological or psychiatric conditions, such as delirium, dementia, or substance intoxication or withdrawal. It is essential for healthcare providers to monitor and address orientation issues to ensure appropriate diagnosis, treatment, and patient safety.

A rod cell outer segment is a specialized structure in the retina of the eye that is responsible for photoreception, or the conversion of light into electrical signals. Rod cells are one of the two types of photoreceptor cells in the retina, with the other type being cone cells. Rod cells are more sensitive to light than cone cells and are responsible for low-light vision and peripheral vision.

The outer segment of a rod cell is a long, thin structure that contains stacks of discs filled with the visual pigment rhodopsin. When light hits the rhodopsin molecules in the discs, it causes a chemical reaction that leads to the activation of a signaling pathway within the rod cell. This ultimately results in the generation of an electrical signal that is transmitted to the brain via the optic nerve.

The outer segment of a rod cell is constantly being regenerated and broken down through a process called shedding and renewal. The tips of the outer segments are shed and phagocytosed by cells called retinal pigment epithelial (RPE) cells, which help to maintain the health and function of the rod cells.

"Hypocrea" is a genus of fungi in the family Hypocreaceae. These fungi are typically saprophytic, meaning they grow on dead or decaying organic matter. They are known for producing colorful and structurally complex fruiting bodies, which are often brightly colored and have a flask-like shape. Some species of Hypocrea are also known to be mycoparasites, meaning they obtain nutrients by growing on and eventually killing other fungi.

One particularly well-known species of Hypocrea is Trichoderma reesei, which has been widely studied for its ability to produce large amounts of cellulases and xylanases, enzymes that break down plant material. This has made it an important organism in the field of biotechnology, where it is used to produce these enzymes for use in various industrial processes, such as the production of biofuels and paper products.

It's worth noting that Hypocrea species are not typically considered to be human pathogens, and are not known to cause disease in healthy individuals. However, some species may be able to cause infection in people with weakened immune systems.

Characidae is a family of freshwater fish that are commonly known as characins. They belong to the order Characiformes and can be found primarily in tropical waters of Central and South America, with a few species in Africa. The family includes over 100 genera and more than 900 described species, making it one of the most diverse families of ray-finned fishes.

Characids exhibit a wide range of body shapes, sizes, and colors, with many having adaptations for specific ecological niches. Some well-known examples of characids include piranhas (Serrasalmus spp.), tetras (Hyphessobrycon spp., Hemigrammus spp., etc.), and hatchetfish (Gasteropelecidae).

The medical significance of characids is relatively limited, as they are not typically associated with human diseases or health issues. However, some species may be kept in aquariums as pets, and proper care should be taken to maintain water quality and prevent the spread of disease among fish populations. Additionally, research on characid fishes can contribute to our understanding of evolution, ecology, and biogeography, which have broader implications for science and conservation.

In the context of medicine, "periodicity" refers to the occurrence of events or phenomena at regular intervals or cycles. This term is often used in reference to recurring symptoms or diseases that have a pattern of appearing and disappearing over time. For example, some medical conditions like menstrual cycles, sleep-wake disorders, and certain infectious diseases exhibit periodicity. It's important to note that the duration and frequency of these cycles can vary depending on the specific condition or individual.

"Ambystoma" is a genus of salamanders, also known as the mole salamanders. These amphibians are characterized by their fossorial (burrowing) habits and typically have four limbs, a tail, and moist skin. They are found primarily in North America, with a few species in Asia and Europe. Some well-known members of this genus include the axolotl (A. mexicanum), which is famous for its ability to regenerate lost body parts, and the spotted salamander (A. maculatum). The name "Ambystoma" comes from the Greek words "amblys," meaning blunt, and "stoma," meaning mouth, in reference to the wide, blunt snout of these animals.

Physiological adaptation refers to the changes or modifications that occur in an organism's biological functions or structures as a result of environmental pressures or changes. These adaptations enable the organism to survive and reproduce more successfully in its environment. They can be short-term, such as the constriction of blood vessels in response to cold temperatures, or long-term, such as the evolution of longer limbs in animals that live in open environments.

In the context of human physiology, examples of physiological adaptation include:

1. Acclimatization: The process by which the body adjusts to changes in environmental conditions, such as altitude or temperature. For example, when a person moves to a high-altitude location, their body may produce more red blood cells to compensate for the lower oxygen levels, leading to improved oxygen delivery to tissues.

2. Exercise adaptation: Regular physical activity can lead to various physiological adaptations, such as increased muscle strength and endurance, enhanced cardiovascular function, and improved insulin sensitivity.

3. Hormonal adaptation: The body can adjust hormone levels in response to changes in the environment or internal conditions. For instance, during prolonged fasting, the body releases stress hormones like cortisol and adrenaline to help maintain energy levels and prevent muscle wasting.

4. Sensory adaptation: Our senses can adapt to different stimuli over time. For example, when we enter a dark room after being in bright sunlight, it takes some time for our eyes to adjust to the new light level. This process is known as dark adaptation.

5. Aging-related adaptations: As we age, various physiological changes occur that help us adapt to the changing environment and maintain homeostasis. These include changes in body composition, immune function, and cognitive abilities.

I'm sorry for any confusion, but "seedling" is not a term that has a specific medical definition. It is an agricultural and horticultural term that refers to a young plant grown from a seed, typically during the early stages of its growth. If you have any questions related to health or medicine, I'd be happy to try to help with those!

Photobiology is the study of the interactions between non-ionizing radiation, primarily ultraviolet (UV), visible, and infrared radiation, and living organisms. It involves how these radiations affect organisms, their metabolic processes, and biological rhythms. This field also includes research on the use of light in therapy, such as phototherapy for treating various skin conditions and mood disorders. Photobiology has important implications for understanding the effects of sunlight on human health, including both beneficial and harmful effects.

Light signal transduction is a biological process that refers to the way in which cells convert light signals into chemical or electrical responses. This process typically involves several components, including a light-sensitive receptor (such as a photopigment), a signaling molecule (like a G-protein or calcium ion), and an effector protein that triggers a downstream response.

In the visual system, for example, light enters the eye and activates photoreceptor cells in the retina. These cells contain a light-sensitive pigment called rhodopsin, which undergoes a chemical change when struck by a photon of light. This change triggers a cascade of signaling events that ultimately lead to the transmission of visual information to the brain.

Light signal transduction is also involved in other biological processes, such as the regulation of circadian rhythms and the synthesis of vitamin D. In these cases, specialized cells contain light-sensitive receptors that allow them to detect changes in ambient light levels and adjust their physiology accordingly.

Overall, light signal transduction is a critical mechanism by which organisms are able to sense and respond to their environment.

I'm sorry for any confusion, but "Perciformes" is not a medical term. It is a term used in the field of biology, specifically in taxonomy and ichthyology (the study of fish). Perciformes is an order of ray-finned bony fishes that includes over 10,000 species, making it the largest order of vertebrates. Examples of fish within this order include perch, sea bass, sunfish, and tuna.

ARNTL (aryl hydrocarbon receptor nuclear translocator-like) transcription factors, also known as BMAL1 (brain and muscle ARNT-like 1), are proteins that bind to DNA and promote the expression of specific genes. They play a critical role in regulating circadian rhythms, which are the physical, mental, and behavioral changes that follow a daily cycle.

ARNTL transcription factors form heterodimers with another set of transcription factors called CLOCK (circadian locomotor output cycles kaput) proteins. Together, these complexes bind to specific DNA sequences known as E-boxes in the promoter regions of target genes. This binding leads to the recruitment of other cofactors and the activation of gene transcription.

ARNTL transcription factors are part of a larger negative feedback loop that regulates circadian rhythms. After activating gene transcription, ARNTL-CLOCK complexes eventually lead to the production of proteins that inhibit their own activity, creating a cycle that repeats approximately every 24 hours.

Disruptions in the function of ARNTL transcription factors have been linked to various circadian rhythm disorders and other health conditions, including sleep disorders, mood disorders, and cancer.

In the field of medicine, "time factors" refer to the duration of symptoms or time elapsed since the onset of a medical condition, which can have significant implications for diagnosis and treatment. Understanding time factors is crucial in determining the progression of a disease, evaluating the effectiveness of treatments, and making critical decisions regarding patient care.

For example, in stroke management, "time is brain," meaning that rapid intervention within a specific time frame (usually within 4.5 hours) is essential to administering tissue plasminogen activator (tPA), a clot-busting drug that can minimize brain damage and improve patient outcomes. Similarly, in trauma care, the "golden hour" concept emphasizes the importance of providing definitive care within the first 60 minutes after injury to increase survival rates and reduce morbidity.

Time factors also play a role in monitoring the progression of chronic conditions like diabetes or heart disease, where regular follow-ups and assessments help determine appropriate treatment adjustments and prevent complications. In infectious diseases, time factors are crucial for initiating antibiotic therapy and identifying potential outbreaks to control their spread.

Overall, "time factors" encompass the significance of recognizing and acting promptly in various medical scenarios to optimize patient outcomes and provide effective care.

The otolithic membrane is a part of the inner ear's vestibular system, which contributes to our sense of balance and spatial orientation. It is composed of a gelatinous material containing tiny calcium carbonate crystals called otoconia or otoliths. These crystals provide weight to the membrane, allowing it to detect linear acceleration and gravity-induced head movements.

There are two otolithic membranes in each inner ear, located within the utricle and saccule, two of the three main vestibular organs. The utricle is primarily responsible for detecting horizontal movement and head tilts, while the saccule senses vertical motion and linear acceleration.

Damage to the otolithic membrane can result in balance disorders, vertigo, or dizziness.

Arylalkylamine N-acetyltransferase (AANAT) is an enzyme that plays a crucial role in the regulation of melatonin synthesis in the body. It catalyzes the acetylation of serotonin to produce N-acetylserotonin, which is then converted to melatonin by the enzyme acetylserotonin O-methyltransferase (ASMT).

Melatonin is a hormone that helps regulate sleep-wake cycles and other physiological processes in the body. The activity of AANAT is influenced by light exposure, with higher levels of activity occurring in darkness and lower levels during light exposure. This allows melatonin production to be synchronized with the day-night cycle, contributing to the regulation of circadian rhythms.

Genetic variations in the AANAT gene have been associated with differences in sleep patterns, mood regulation, and other physiological processes. Dysregulation of AANAT activity has been implicated in various conditions, including insomnia, depression, and seasonal affective disorder.

"Motor activity" is a general term used in the field of medicine and neuroscience to refer to any kind of physical movement or action that is generated by the body's motor system. The motor system includes the brain, spinal cord, nerves, and muscles that work together to produce movements such as walking, talking, reaching for an object, or even subtle actions like moving your eyes.

Motor activity can be voluntary, meaning it is initiated intentionally by the individual, or involuntary, meaning it is triggered automatically by the nervous system without conscious control. Examples of voluntary motor activity include deliberately lifting your arm or kicking a ball, while examples of involuntary motor activity include heartbeat, digestion, and reflex actions like jerking your hand away from a hot stove.

Abnormalities in motor activity can be a sign of neurological or muscular disorders, such as Parkinson's disease, cerebral palsy, or multiple sclerosis. Assessment of motor activity is often used in the diagnosis and treatment of these conditions.

'Gravity sensing' is not a term typically used in medical definitions. However, in the context of physiology and neuroscience, it refers to the ability of certain cells or organisms to detect and respond to changes in gravity. This is particularly relevant in the vestibular system, which is responsible for maintaining balance and spatial orientation.

In the human body, gravity sensing in the vestibular system is achieved through the detection of head movement and position by hair cells located in the inner ear. These hair cells are embedded in a gel-like structure within the semicircular canals and the utricle and saccule of the vestibular apparatus. When the head moves, the fluid within these structures moves as well, bending the hair cells and stimulating nerve impulses that are sent to the brain. The brain then interprets these signals to help us maintain our balance and spatial orientation.

Therefore, while not a traditional medical definition, gravity sensing is an important concept in understanding how the body maintains its equilibrium and navigates through space.

CLOCK proteins are a pair of transcription factors, CIRCADIAN LOComotor OUTPUT Cycles Kaput (CLOCK) and BMAL1 (brain and muscle ARNT-like 1), that play a critical role in the regulation of circadian rhythms. Circadian rhythms are biological processes that follow an approximately 24-hour cycle, driven by molecular mechanisms within cells.

The CLOCK and BMAL1 proteins form a heterodimer, which binds to E-box elements in the promoter regions of target genes. This binding activates the transcription of these genes, leading to the production of proteins that are involved in various cellular processes. After being transcribed and translated, some of these proteins feed back to inhibit the activity of the CLOCK-BMAL1 heterodimer, forming a negative feedback loop that is essential for the oscillation of circadian rhythms.

The regulation of circadian rhythms by CLOCK proteins has implications in many physiological processes, including sleep-wake cycles, metabolism, hormone secretion, and cellular proliferation. Dysregulation of these rhythms has been linked to various diseases, such as sleep disorders, metabolic disorders, and cancer.

'Bufo marinus' is the scientific name for a species of toad commonly known as the Cane Toad or Giant Toad. This toad is native to Central and South America, but has been introduced to various parts of the world including Florida, Australia, and several Pacific islands. The toad produces a toxic secretion from glands on its back and neck, which can be harmful or fatal if ingested by pets or humans.

Phytochrome B is a type of phytochrome photoreceptor found in plants that regulates various physiological and developmental processes in response to red and far-red light. It plays a crucial role in seed germination, de-etiolation, shade avoidance responses, and flowering time regulation. Phytochrome B exists in two interconvertible forms: Pr (the inactive, red light-absorbing form) and Pfr (the active, far-red light-absorbing form). The conversion between these forms allows phytochrome B to act as a molecular switch that mediates plant responses to different light conditions.

I'm sorry for any confusion, but "gravitation" is not a term that is typically used in the context of medical definitions. Gravitation is a fundamental force that attracts two objects with mass towards each other. It is the force that causes objects to fall towards the earth and keeps the planets in orbit around the sun.

In the field of medicine, the concepts of gravity or gravitational forces are not directly relevant to the diagnosis or treatment of medical conditions. However, there may be some indirect applications related to physiology and human health, such as the effects of microgravity on the human body during space travel.

In the context of medical terminology, "germination" is not typically used as a term to describe a physiological process in humans or animals. It is primarily used in the field of botany to refer to the process by which a seed or spore sprouts and begins to grow into a new plant.

However, if you are referring to the concept of germination in the context of bacterial or viral growth, then it could be defined as:

The process by which bacteria, viruses, or other microorganisms become active and start to multiply, often after a period of dormancy or latency. This can occur when the microorganisms encounter favorable conditions, such as moisture, warmth, or nutrients, that allow them to grow and reproduce. In medical contexts, this term is more commonly used in relation to infectious diseases caused by these microorganisms.

"Plant proteins" refer to the proteins that are derived from plant sources. These can include proteins from legumes such as beans, lentils, and peas, as well as proteins from grains like wheat, rice, and corn. Other sources of plant proteins include nuts, seeds, and vegetables.

Plant proteins are made up of individual amino acids, which are the building blocks of protein. While animal-based proteins typically contain all of the essential amino acids that the body needs to function properly, many plant-based proteins may be lacking in one or more of these essential amino acids. However, by consuming a variety of plant-based foods throughout the day, it is possible to get all of the essential amino acids that the body needs from plant sources alone.

Plant proteins are often lower in calories and saturated fat than animal proteins, making them a popular choice for those following a vegetarian or vegan diet, as well as those looking to maintain a healthy weight or reduce their risk of chronic diseases such as heart disease and cancer. Additionally, plant proteins have been shown to have a number of health benefits, including improving gut health, reducing inflammation, and supporting muscle growth and repair.

In the context of medicine and physiology, acceleration refers to the process of increasing or quickening a function or process. For example, heart rate acceleration is an increase in the speed at which the heart beats. It can also refer to the rate at which something increases, such as the acceleration of muscle strength during rehabilitation. In physics terms, acceleration refers to the rate at which an object changes its velocity, but this definition is not typically used in a medical context.

Retinal pigments refer to the light-sensitive chemicals found in the retina, specifically within the photoreceptor cells called rods and cones. The main types of retinal pigments are rhodopsin (also known as visual purple) in rods and iodopsins in cones. These pigments play a crucial role in the process of vision by absorbing light and initiating a series of chemical reactions that ultimately trigger nerve impulses, which are then transmitted to the brain and interpreted as visual images. Rhodopsin is more sensitive to lower light levels and is responsible for night vision, while iodopsins are sensitive to specific wavelengths of light and contribute to color vision.

Pathological nystagmus is an abnormal, involuntary movement of the eyes that can occur in various directions (horizontal, vertical, or rotatory) and can be rhythmical or arrhythmic. It is typically a result of a disturbance in the vestibular system, central nervous system, or ocular motor pathways. Pathological nystagmus can cause visual symptoms such as blurred vision, difficulty with fixation, and oscillopsia (the sensation that one's surroundings are moving). The type, direction, and intensity of the nystagmus may vary depending on the underlying cause, which can include conditions such as brainstem or cerebellar lesions, multiple sclerosis, drug toxicity, inner ear disorders, and congenital abnormalities.

"Tupaia" is not a term found in general medical terminology. It is most likely referring to a genus of small mammals known as tree shrews, also called "tupaias." They are native to Southeast Asia and are not closely related to shrews, but rather belong to their own order, Scandentia.

However, if you're referring to a specific medical condition or concept that uses the term "Tupaia," I would need more context to provide an accurate definition.

Rhodopsin, also known as visual purple, is a light-sensitive pigment found in the rods of the vertebrate retina. It is a complex protein molecule made up of two major components: an opsin protein and retinal, a form of vitamin A. When light hits the retinal in rhodopsin, it changes shape, which initiates a series of chemical reactions leading to the activation of the visual pathway and ultimately results in vision. This process is known as phototransduction. Rhodopsin plays a crucial role in low-light vision or scotopic vision.

A saccade is a quick, rapid, and ballistic conjugate eye movement that shifts the point of fixation from one target to another. It helps in rapidly repositioning the fovea (the central part of the retina with the highest visual acuity) to focus on different targets of interest in the visual scene. Saccades are essential for efficient scanning and exploration of our environment, allowing us to direct our high-resolution vision towards various points of interest. They typically take only about 20-200 milliseconds to complete and can reach peak velocities of up to 500 degrees per second or more, depending on the amplitude of the movement. Saccades are a critical component of normal visual function and are often studied in fields such as ophthalmology, neurology, and neuroscience.

Photoreceptor cells in vertebrates are specialized types of neurons located in the retina of the eye that are responsible for converting light stimuli into electrical signals. These cells are primarily responsible for the initial process of vision and have two main types: rods and cones.

Rods are more numerous and are responsible for low-light vision or scotopic vision, enabling us to see in dimly lit conditions. They do not contribute to color vision but provide information about the shape and movement of objects.

Cones, on the other hand, are less numerous and are responsible for color vision and high-acuity vision or photopic vision. There are three types of cones, each sensitive to different wavelengths of light: short (S), medium (M), and long (L) wavelengths, which correspond to blue, green, and red, respectively. The combination of signals from these three types of cones allows us to perceive a wide range of colors.

Both rods and cones contain photopigments that consist of a protein called opsin and a light-sensitive chromophore called retinal. When light hits the photopigment, it triggers a series of chemical reactions that ultimately lead to the generation of an electrical signal that is transmitted to the brain via the optic nerve. This process enables us to see and perceive our visual world.

I'm sorry for any confusion, but "Moon" is not a commonly used medical term. The moon is a natural satellite that orbits around the Earth and is not related to medical terminology or anatomy. If you have any questions about medical definitions or topics, I would be happy to help!

Genetically modified plants (GMPs) are plants that have had their DNA altered through genetic engineering techniques to exhibit desired traits. These modifications can be made to enhance certain characteristics such as increased resistance to pests, improved tolerance to environmental stresses like drought or salinity, or enhanced nutritional content. The process often involves introducing genes from other organisms, such as bacteria or viruses, into the plant's genome. Examples of GMPs include Bt cotton, which has a gene from the bacterium Bacillus thuringiensis that makes it resistant to certain pests, and golden rice, which is engineered to contain higher levels of beta-carotene, a precursor to vitamin A. It's important to note that genetically modified plants are subject to rigorous testing and regulation to ensure their safety for human consumption and environmental impact before they are approved for commercial use.

Photoreceptor cells in invertebrates are specialized sensory neurons that convert light stimuli into electrical signals. These cells are primarily responsible for the ability of many invertebrates to detect and respond to light, enabling behaviors such as phototaxis (movement towards or away from light) and vision.

Invertebrate photoreceptor cells typically contain light-sensitive pigments that absorb light at specific wavelengths. The most common type of photopigment is rhodopsin, which consists of a protein called opsin and a chromophore called retinal. When light hits the photopigment, it changes the conformation of the chromophore, triggering a cascade of molecular events that ultimately leads to the generation of an electrical signal.

Invertebrate photoreceptor cells can be found in various locations throughout the body, depending on their function. For example, simple eyespots containing a few photoreceptor cells may be scattered over the surface of the body in some species, while more complex eyes with hundreds or thousands of photoreceptors may be present in other groups. In addition to their role in vision, photoreceptor cells can also serve as sensory organs for regulating circadian rhythms, detecting changes in light intensity, and mediating social behaviors.

The Antarctic regions typically refer to the geographical areas surrounding the continent of Antarctica, including the Southern Ocean and various subantarctic islands. These regions are known for their extreme cold, ice-covered landscapes, and unique wildlife adapted to survive in harsh conditions. The Antarctic region is also home to important scientific research stations focused on topics such as climate change, marine life, and space exploration. It's worth noting that the Antarctic Treaty System governs these regions, which prohibits military activity, mineral mining, nuclear testing, and nuclear waste disposal, and promotes scientific research and cooperation among nations.

Chloroplasts are specialized organelles found in the cells of green plants, algae, and some protists. They are responsible for carrying out photosynthesis, which is the process by which these organisms convert light energy from the sun into chemical energy in the form of organic compounds, such as glucose.

Chloroplasts contain the pigment chlorophyll, which absorbs light energy from the sun. They also contain a system of membranes and enzymes that convert carbon dioxide and water into glucose and oxygen through a series of chemical reactions known as the Calvin cycle. This process not only provides energy for the organism but also releases oxygen as a byproduct, which is essential for the survival of most life forms on Earth.

Chloroplasts are believed to have originated from ancient cyanobacteria that were engulfed by early eukaryotic cells and eventually became integrated into their host's cellular machinery through a process called endosymbiosis. Over time, chloroplasts evolved to become an essential component of plant and algal cells, contributing to their ability to carry out photosynthesis and thrive in a wide range of environments.

Distance perception refers to the ability to accurately judge the distance or depth of an object in relation to oneself or other objects. It is a complex process that involves both visual and non-visual cues, such as perspective, size, texture, motion parallax, binocular disparity, and familiarity with the object or scene.

In the visual system, distance perception is primarily mediated by the convergence of the two eyes on an object, which provides information about its depth and location in three-dimensional space. The brain then integrates this information with other sensory inputs and prior knowledge to create a coherent perception of the environment.

Disorders of distance perception can result from various conditions that affect the visual system, such as amblyopia, strabismus, or traumatic brain injury. These disorders can cause difficulties in tasks that require accurate depth perception, such as driving, sports, or manual work.

Photosynthetic Reaction Center (RC) Complex Proteins are specialized protein-pigment structures that play a crucial role in the primary process of light-driven electron transport during photosynthesis. They are present in the thylakoid membranes of cyanobacteria, algae, and higher plants.

The Photosynthetic Reaction Center Complex Proteins are composed of two major components: the light-harvesting complex (LHC) and the reaction center (RC). The LHC contains antenna pigments like chlorophylls and carotenoids that absorb sunlight and transfer the excitation energy to the RC. The RC is a multi-subunit protein complex containing cofactors such as bacteriochlorophyll, pheophytin, quinones, and iron-sulfur clusters.

When a photon of light is absorbed by the antenna pigments in the LHC, the energy is transferred to the RC, where it initiates a charge separation event. This results in the transfer of an electron from a donor molecule to an acceptor molecule, creating a flow of electrical charge and generating a transmembrane electrochemical gradient. The energy stored in this gradient is then used to synthesize ATP and reduce NADP+, which are essential for carbon fixation and other metabolic processes in the cell.

In summary, Photosynthetic Reaction Center Complex Proteins are specialized protein structures involved in capturing light energy and converting it into chemical energy during photosynthesis, ultimately driving the synthesis of ATP and NADPH for use in carbon fixation and other metabolic processes.

Electroretinography (ERG) is a medical test used to evaluate the functioning of the retina, which is the light-sensitive tissue located at the back of the eye. The test measures the electrical responses of the retina to light stimulation.

During the procedure, a special contact lens or electrode is placed on the surface of the eye to record the electrical activity generated by the retina's light-sensitive cells (rods and cones) and other cells in the retina. The test typically involves presenting different levels of flashes of light to the eye while the electrical responses are recorded.

The resulting ERG waveform provides information about the overall health and function of the retina, including the condition of the photoreceptors, the integrity of the inner retinal layers, and the health of the retinal ganglion cells. This test is often used to diagnose and monitor various retinal disorders, such as retinitis pigmentosa, macular degeneration, and diabetic retinopathy.

The Arctic region is not a medical term per se, but it is a geographical and environmental term that can have health-related implications. The Arctic is defined as the region surrounding the North Pole, encompassing the Arctic Ocean and parts of Canada, Greenland (Denmark), Russia, the United States (Alaska), Norway, Sweden, Finland, and Iceland. It is characterized by its cold climate, permafrost, and unique ecosystems.

Exposure to the harsh Arctic environment can pose significant health risks, such as hypothermia, frostbite, and other cold-related injuries. Additionally, the Arctic region has been impacted by climate change, leading to changes in the distribution of wildlife, which can have implications for food security and infectious disease transmission.

Therefore, while not a medical term itself, understanding the Arctic regions and their unique environmental and health challenges is important in fields such as wilderness medicine, environmental health, and public health.

Ocular fixation is a term used in ophthalmology and optometry to refer to the ability of the eyes to maintain steady gaze or visual focus on an object. It involves the coordinated movement of the extraocular muscles that control eye movements, allowing for clear and stable vision.

In medical terminology, fixation specifically refers to the state in which the eyes are aligned and focused on a single point in space. This is important for maintaining visual perception and preventing blurring or double vision. Ocular fixation can be affected by various factors such as muscle weakness, nerve damage, or visual processing disorders.

Assessment of ocular fixation is often used in eye examinations to evaluate visual acuity, eye alignment, and muscle function. Abnormalities in fixation may indicate the presence of underlying eye conditions or developmental delays that require further investigation and treatment.

Methylphenazonium methosulfate is not a medication itself, but rather a reagent used in the production and pharmacological research of certain medications. It's commonly used as a redox mediator, which means it helps to facilitate electron transfer in chemical reactions. In medical contexts, it may be used in the laboratory synthesis or testing of some drugs.

It's important to note that methylphenazonium methosulfate is not intended for direct medical use in humans or animals. Always consult with a healthcare professional or trusted medical source for information regarding specific medications and their uses.

I'm sorry for any confusion, but "Goldfish" is not a term used in medical definitions. Goldfish are small domesticated fish that are often kept as pets. They belong to the family Cyprinidae and the genus Carassius. The most common species of goldfish is Carassius auratus. If you have any questions about goldfish or their care, I might be able to help with some general information, but for specific medical concerns, it would be best to consult a veterinarian.

"Octodon" is the genus name for a group of rodents that are native to South America, also known as "degu." They are small animals, typically weighing between 200-350 grams, with a body length of about 10-15 inches including their tail.

Octodons have a distinct appearance, with a pointed snout, large ears, and a bushy tail that is longer than their body. They are primarily herbivorous, feeding on a variety of plant materials such as grasses, leaves, and seeds.

In a medical context, "octodon" may be used in scientific research to refer to this species of animal. Researchers may study octodons to learn more about various aspects of biology and medicine, including their physiology, behavior, genetics, and responses to drugs or diseases. However, it is important to note that the use of animals in research should always be done in an ethical and responsible manner, with careful consideration given to their welfare and well-being.

Cyanobacteria, also known as blue-green algae, are a type of bacteria that obtain their energy through photosynthesis, similar to plants. They can produce oxygen and contain chlorophyll a, which gives them a greenish color. Some species of cyanobacteria can produce toxins that can be harmful to humans and animals if ingested or inhaled. They are found in various aquatic environments such as freshwater lakes, ponds, and oceans, as well as in damp soil and on rocks. Cyanobacteria are important contributors to the Earth's oxygen-rich atmosphere and play a significant role in the global carbon cycle.

A gene in plants, like in other organisms, is a hereditary unit that carries genetic information from one generation to the next. It is a segment of DNA (deoxyribonucleic acid) that contains the instructions for the development and function of an organism. Genes in plants determine various traits such as flower color, plant height, resistance to diseases, and many others. They are responsible for encoding proteins and RNA molecules that play crucial roles in the growth, development, and reproduction of plants. Plant genes can be manipulated through traditional breeding methods or genetic engineering techniques to improve crop yield, enhance disease resistance, and increase nutritional value.

Phototropins are a type of photoreceptor protein found in plants that play a crucial role in the perception and response to light. They are responsible for mediating phototropism, which is the growth movement of a plant in response to a unidirectional light source. This process allows the plant to optimize its exposure to sunlight for photosynthesis.

Phototropins contain two flavin-binding domains called LOV (Light, Oxygen, or Voltage) domains that absorb blue light at around 450 nm wavelength. Upon absorption of light, a conformational change occurs in the phototropin protein, leading to activation of downstream signaling pathways involved in various light-dependent responses such as chloroplast movement, leaf expansion, and stomatal opening.

Overall, phototropins are essential for plants' ability to sense and adapt to their light environment, which is critical for their growth, development, and survival.

Space perception, in the context of neuroscience and psychology, refers to the ability to perceive and understand the spatial arrangement of objects and their relationship to oneself. It involves integrating various sensory inputs such as visual, auditory, tactile, and proprioceptive information to create a coherent three-dimensional representation of our environment.

This cognitive process enables us to judge distances, sizes, shapes, and movements of objects around us. It also helps us navigate through space, reach for objects, avoid obstacles, and maintain balance. Disorders in space perception can lead to difficulties in performing everyday activities and may be associated with neurological conditions such as stroke, brain injury, or neurodevelopmental disorders like autism.

Flavoproteins are a type of protein molecule that contain noncovalently bound flavin mononucleotide (FMN) or flavin adenine dinucleotide (FAD) as cofactors. These flavin cofactors play a crucial role in redox reactions, acting as electron carriers in various metabolic pathways such as cellular respiration and oxidative phosphorylation. Flavoproteins are involved in several biological processes, including the breakdown of fatty acids, amino acids, and carbohydrates, as well as the synthesis of steroids and other lipids. They can also function as enzymes that catalyze various redox reactions, such as oxidases, dehydrogenases, and reductases. Flavoproteins are widely distributed in nature and found in many organisms, from bacteria to humans.

Electrooculography (EOG) is a technique for measuring the resting potential of the eye and the changes in this potential that occur with eye movements. It involves placing electrodes near the eyes to detect the small electric fields generated by the movement of the eyeball within the surrounding socket. This technique is used in research and clinical settings to study eye movements and their control, as well as in certain diagnostic applications such as assessing the function of the oculomotor system in patients with neurological disorders.

Photosystem II Protein Complex is a crucial component of the photosynthetic apparatus in plants, algae, and cyanobacteria. It is a multi-subunit protein complex located in the thylakoid membrane of the chloroplasts. Photosystem II plays a vital role in light-dependent reactions of photosynthesis, where it absorbs sunlight and uses its energy to drive the oxidation of water molecules into oxygen, electrons, and protons.

The protein complex consists of several subunits, including the D1 and D2 proteins, which form the reaction center, and several antenna proteins that capture light energy and transfer it to the reaction center. Photosystem II also contains various cofactors, such as pigments (chlorophylls and carotenoids), redox-active metal ions (manganese and calcium), and quinones, which facilitate the charge separation and electron transfer processes during photosynthesis.

Photosystem II Protein Complex is responsible for the initial charge separation event in photosynthesis, which sets off a series of redox reactions that ultimately lead to the reduction of NADP+ to NADPH and the synthesis of ATP, providing energy for the carbon fixation reactions in the Calvin cycle. Additionally, Photosystem II Protein Complex is involved in oxygen evolution, contributing to the Earth's atmosphere's oxygen levels and making it an essential component of global carbon fixation and oxygen production.

I cannot provide a medical definition for "carps" as it is not a term used in medicine. The term "carp" refers to a type of freshwater fish that belongs to the family Cyprinidae. If you meant to ask about something else, please provide more context or clarify your question.

The eye is the organ of sight, primarily responsible for detecting and focusing on visual stimuli. It is a complex structure composed of various parts that work together to enable vision. Here are some of the main components of the eye:

1. Cornea: The clear front part of the eye that refracts light entering the eye and protects the eye from harmful particles and microorganisms.
2. Iris: The colored part of the eye that controls the amount of light reaching the retina by adjusting the size of the pupil.
3. Pupil: The opening in the center of the iris that allows light to enter the eye.
4. Lens: A biconvex structure located behind the iris that further refracts light and focuses it onto the retina.
5. Retina: A layer of light-sensitive cells (rods and cones) at the back of the eye that convert light into electrical signals, which are then transmitted to the brain via the optic nerve.
6. Optic Nerve: The nerve that carries visual information from the retina to the brain.
7. Vitreous: A clear, gel-like substance that fills the space between the lens and the retina, providing structural support to the eye.
8. Conjunctiva: A thin, transparent membrane that covers the front of the eye and the inner surface of the eyelids.
9. Extraocular Muscles: Six muscles that control the movement of the eye, allowing for proper alignment and focus.

The eye is a remarkable organ that allows us to perceive and interact with our surroundings. Various medical specialties, such as ophthalmology and optometry, are dedicated to the diagnosis, treatment, and management of various eye conditions and diseases.

In the context of medical terminology, 'color' is not defined specifically with a unique meaning. Instead, it generally refers to the characteristic or appearance of something, particularly in relation to the color that a person may observe visually. For instance, doctors may describe the color of a patient's skin, eyes, hair, or bodily fluids to help diagnose medical conditions or monitor their progression.

For example, jaundice is a yellowing of the skin and whites of the eyes that can indicate liver problems, while cyanosis refers to a bluish discoloration of the skin and mucous membranes due to insufficient oxygen in the blood. Similarly, doctors may describe the color of stool or urine to help diagnose digestive or kidney issues.

Therefore, 'color' is not a medical term with a specific definition but rather a general term used to describe various visual characteristics of the body and bodily fluids that can provide important diagnostic clues for healthcare professionals.

"Rhodospirillum rubrum" is a gram-negative, facultatively anaerobic, photosynthetic bacteria species. It is commonly found in freshwater and soil environments, and it has the ability to carry out both photosynthesis and respiration, depending on the availability of light and oxygen. The bacteria contain bacteriochlorophyll and carotenoid pigments, which give them a pinkish-red color, hence the name "rubrum." They are known to be important organisms in the study of photosynthesis, nitrogen fixation, and other metabolic processes.

'Animal behavior' refers to the actions or responses of animals to various stimuli, including their interactions with the environment and other individuals. It is the study of the actions of animals, whether they are instinctual, learned, or a combination of both. Animal behavior includes communication, mating, foraging, predator avoidance, and social organization, among other things. The scientific study of animal behavior is called ethology. This field seeks to understand the evolutionary basis for behaviors as well as their physiological and psychological mechanisms.

Acetylserotonin O-methyltransferase (ASMT) is an enzyme that catalyzes the final step in melatonin synthesis. It transfers a methyl group from S-adenosylmethionine to acetylserotonin, forming melatonin and S-adenosylhomocysteine. ASMT plays a crucial role in regulating the sleep-wake cycle and other physiological processes influenced by melatonin.

Protochlorophyllide is a pigment involved in the process of photosynthesis. It is a precursor to chlorophyll, which is the main pigment responsible for light absorption during photosynthesis. Protochlorophyllide is present in the chloroplasts of plant cells and certain types of algae. It is converted to chlorophyllide by the action of light during the process of photoactivation, which is the activation of a chemical reaction by light. Defects in the biosynthesis of protochlorophyllide can lead to certain types of genetic disorders that affect photosynthesis and plant growth.

I apologize for any confusion, but "plants" is not a term that has a medical definition. The term "plants" refers to a large and diverse group of organisms that obtain their energy through photosynthesis, which is the process of converting sunlight into chemical energy. Plants are typically characterized by having cells with cell walls containing cellulose, chloroplasts containing the pigment chlorophyll, and the ability to synthesize their own food through photosynthesis.

In a medical or biological context, you might be thinking of "plant-based" or "phytomedicine," which refer to the use of plants or plant extracts as a form of medicine or treatment. Phytomedicines have been used for thousands of years in many traditional systems of medicine, and some plant-derived compounds have been found to have therapeutic benefits in modern medicine as well. However, "plants" itself does not have a medical definition.

The dictionary definition of darkness at Wiktionary Quotations related to Darkness at Wikiquote Media related to Darkness at ... Artists use darkness to emphasize and contrast the presence of light. Darkness can be used as a counterpoint to areas of ... Exposure to alternating light and darkness (night and day) has caused several evolutionary adaptations to darkness. When a ... "workes of darkness". In Divine Comedy, Dante described hell as "solid darkness stain'd". In Old English there were three words ...
Wikiquote has quotations related to Eternal Darkness. Eternal Darkness: Sanity's Requiem at MobyGames Eternal Darkness: ... "Nintendo's Eternal Darkness Film Contest". Gaming Edge. Archived from the original on May 18, 2011. "Eternal Darkness TV Show ... "Eternal Darkness Films Contest This Week". Nintendo World Report. Billy Berghammer. "Eternal Darkness Films Contest Winner ... "Eternal Darkness: Sanity's Requiem Reviews". GameRankings. Retrieved December 27, 2008. "Eternal Darkness: Sanity's Requiem ( ...
... had plans to tour Europe in late 2000, but this seems to have not occurred. Kelson has also featured in the ... Cryptal Darkness started life as a grindcore/death metal band, that later changed styles and became doom metal band. With the ... Cryptal Darkness were an Australian doom metal band from Melbourne featuring Mark Kelson, now of The Eternal and InSomnius Dei ... Kelson is also involved with InSomnius Dei with fellow Cryptal Darkness alumni, Terry Vainoras. Last Known Lineup Mark Kelson ...
... ". Dusk & Shiver. Retrieved 2021-11-18. Turpitt, Elle (2019-09-23). "[Review] - Calling Darkness Podcast". ... Calling Darkness is a horror comedy podcast written by Gemma Amor and S.H.Cooper. It was co-created by S.H.Cooper, Gemma Amor, ... "Calling Darkness: the Podcast", gemmaamorauthor.com, 28 January 2019, retrieved 2021-11-18 "About: The Cast and Crew of Calling ... Calling Darkness on Twitter (Articles with short description, Short description matches Wikidata, Short description is ...
... may refer to: After Darkness (1985 film), a Swiss horror film After Darkness (2019 film), an American-Mexican ... science fiction film After Darkness (novel), a 2014 novel by Christine Piper After the Darkness (disambiguation) This ... disambiguation page lists articles associated with the title After Darkness. If an internal link led you here, you may wish to ...
... is the debut EP from Devil Sold His Soul, released in 2005. It was produced and recorded by Mark Williams at ... "Clouds (Remix)" "Darkness Prevails (Final Demo)" "Some Friend (Original Demo)" "Clouds (Final Demo)" "Like It's Your Last ( ... "Darkness Prevails" (live video) "Like It's Your Last" (live video) "The Starting" (live video) v t e (Articles lacking sources ... Original Demo)" "Darkness Prevails" (music video) "Clouds" (music video) "Like It's Your Last" (music video) "Recording" ( ...
... may refer to: In Darkness (2009 film), a 2009 Turkish film In Darkness (2011 film), a 2011 Polish film In Darkness ... 2013 In Darkness (Varials album), 2019 Poet Anderson: ...In Darkness, a 2018 American novel by Tom DeLonge and Suzanne Young ... 2018 film), a 2018 American film In Darkness (Agathodaimon album), ... This disambiguation page lists articles associated with the title In Darkness. If an internal link led you here, you may wish ...
... appears in the video games To Love Ru Darkness: Battle Ecstasy (2014) and To Love Ru Darkness: True Princess ( ... In the sequel to To Love Ru, entitled To Love Ru Darkness, after some convincing from Mikan, Golden Darkness enrolls in the ... Reviewing To Love Ru Darkness, Martin noted how Golden Darkness has been demoted to a substantially "meatier role" in the ... But due to Golden Darkness' feelings for Rito, instead of giving her an insatiable thirst for destruction, the "Darkness" ...
Man - Maximum Darkness (1975) album reviews, credits & releases at AllMusic.com Man - Maximum Darkness (1975) album releases & ... credits at Discogs.com Man - Maximum Darkness (1975) album credits & user reviews at ProgArchives.com Man - Maximum Darkness ( ... Maximum Darkness is the tenth album by the Welsh rock band Man and was released on the United Artists Records label September ... Maximum Darkness > Overview )))". www.allmusic.com. Retrieved 1 December 2009. "Manband Archive - Music". www.manband-archive. ...
... or The White Darkness may refer to: White Darkness (album), by the Swedish rock band Nightingale White Darkness ... novel), a Doctor Who novel by David A. McIntee The White Darkness (film), a 2002 collaboration between Richard Stanley and ... Simon Boswell The White Darkness (Grann book), a 2018 non-fiction book by David Grann The White Darkness (novel), a children's ... novel by Geraldine McCaughrean This disambiguation page lists articles associated with the title White Darkness. If an internal ...
"Darkness Darkness". Allmusic.com. Retrieved 21 February 2009. "Darkness Darkness album credits". Allmusic.com. Retrieved 21 ... Darkness Darkness is an album by the former vocalist from The Animals, Eric Burdon. It was recorded in May 1978 at Roundwood ... "Darkness, Darkness" (Jesse Colin Young) (4:11) "On the Horizon" (Jerry Leiber, Mike Stoller) (3.32) "Rat Race" (Jerry Leiber, ... The line up for Darkness Darkness included Bobby Tench (Streetwalkers), Brian Robertson (Thin Lizzy, Motörhead), Henry ...
... at the official website Of Darkness... at MusicBrainz Of Darkness... at Discogs Audio samples Of Darkness... at ... "Of Darkness..." Therion. "Of Darkness". Allmusic. Retrieved 2008-02-05. "Of Darkness..." Rate Your Music. Retrieved 2008-02-05 ... Of Darkness... consists of songs Christofer Johnsson had written in the years of 1987-1989, many of which were available on the ... Of Darkness... received a medium rating 2.5 of 5 at Allmusic with "Morbid Reality" and "Megalomania" songs picked by its staff ...
The Light in Darkness: Limited edition book featuring original stories and photos from this iconic 1978 album and tour. The ... Bruce Springsteen and the E Street Band's Darkness Tour was a concert tour of North America that ran from May 1978 through the ... "Prove It All Night", the failed first single from Darkness, was reshaped into an eleven-minute epic with a long, howling guitar ... In 2006, Springsteen manager Jon Landau indicated that a full-length filmed concert DVD from the Darkness Tour might be in the ...
... is a 30-minute documentary film on the dangers and prevalence of the drug methamphetamine. The film features ... The Crystal Darkness documentary was created and produced in Reno, Nevada in 2006 by Michael Reynolds. The campaign was ... About Crystal Darkness Archived 2008-09-19 at the Wayback Machine East Valley Tribune: Campaign working, can do more Archived ... "Crystal Darkness Simulcast Generates Calls for Help". Join Together. crystaldarkness.com: About the film. Archived 2008-09-19 ...
... is the fifth studio album from British musician Fink, and the fourth to be recorded with his self-titled band ... "New LP - Perfect Darkness". Finkworld.co.uk. 29 April 2011. Archived from the original on 2 May 2011. Retrieved 11 July 2021. " ... Perfect Darkness was met with "generally favorable" reviews from critics. At Metacritic, which assigns a weighted average ... "Perfect Darkness - Fink". Ninja Tune. Retrieved 11 July 2021. Kerr, Will (7 June 2011). "Fink: Interview". Gigwise. Retrieved ...
... is a 2014 horror-thriller comedy film directed and written by James Townsend and starring Kyle Blitch, Ronnie ... Caleb Carter at IMDb Kissing Darkness at IMDb v t e (Articles with short description, Short description is different from ...
... was reviewed by Kirkus Reviews. Moser, Margaret (29 September 2006). "Love in the Time of 'Green Darkness'". ... Following the Trail of Anya Seton's Green Darkness "Book Review: Green Darkness". Kirkus Reviews. Retrieved 2020-05-29. ( ... Green Darkness is a 1972 novel by Anya Seton. It spent six months on The New York Times Best Seller list and became her most ... The Manor House setting in Green Darkness at Ightham Mote was faithfully replicated at Cape Elizabeth, Maine by Charles Henry ...
Look up darkness in Wiktionary, the free dictionary. Darkness is the absence of light. Darkness or The Darkness may also refer ... "Darkness", a song by Disturbed from Believe "Darkness", a song by Lamb from Between Darkness and Wonder "Darkness", a song by ... "Darkness" (Aerosmith song) "Darkness" (Darren Hayes song) "Darkness" (Eminem song) "Darkness", a song by Black Uhuru from Chill ... Darkness (KonoSuba), a character in the light novel series KonoSuba The Darkness (band), a British rock band The Darkness ( ...
35-37 "Darkness," ll. 55-69 "Darkness," ll. 45 "Darkness," ll. 41 see Matt 24:12 "Darkness," ll. 81-82 Paley, 6 "Darkness," ll ... 305-6. Darkness public domain audiobook at LibriVox "Darkness" at Poetry Foundation "Darkness" at Wikisource (Articles with ... in Vail 186 "Darkness," ll. 122-123 qtd. in Schroeder 116 "Darkness," ll. 4 Schroeder, 116 Schroeder 117 see Matt 24:51 " ... 38-39 "Darkness," ll. 37 Paley 6 Paley, 6 Gordon, George. "Darkness." The Norton Anthology of English Literature. Stephen ...
... may refer to: Star Trek Into Darkness, a 2013 film in the Star Trek franchise Into Darkness (album), the first ... the second album by Vital Remains This disambiguation page lists articles associated with the title Into Darkness. If an ... and only full-length album of American doom metal band Winter Into Cold Darkness, ...
"Redefining Darkness - Shining". AllMusic. Retrieved 5 January 2013. "Shining's 'Redefining Darkness' OUT TODAY!". Spinefarm ... Redefining Darkness is the eighth studio album by the Swedish black metal band Shining. It was released through Spinefarm ... "Shining (3) - Redefining Darkness (CD, Album) at Discogs". Discogs. Retrieved 6 January 2013. (Use dmy dates from November 2021 ... Keevill, David (22 October 2012). "Album: Shining - Redefining Darkness". thrashhits.com. Retrieved 5 January 2013. " ...
... is the third studio album of the Slovak band Lavagance. The album was recorded at Lavagance studio and released ... Divine Darkness". cdbaby.com. Retrieved 2010-03-21. Official Lavagance website: lavagance.com Lavagance on MySpace v t e ( ...
... is the debut album of the Greek metal band Saddolls. This was also the only album to feature a live keyboard ... "About Darkness"(Emotion Art Music)". Archived from the original on 2014-10-19. Retrieved 2014-10-15. (Articles needing ...
It is recorded as three days of darkness after a period of extreme storms and devastation. Following the three days of darkness ... and provides the obscuring of the Sun as the cause of the darkness: It was now about noon, and darkness came over the whole ... This darkness Thallus, in the third book of his History, calls, as appears to me without reason, an eclipse of the sun. For the ... The image of darkness over the land would have been understood by ancient readers as a cosmic sign, a typical element in the ...
... on Philadelphia - DFA Live at the Trocadero, October 23, 1988 Darkness Descends on Reseda - DFA Live at the ... The song "Darkness Descends" is about the comic book characters known as the Dark Judges from the Judge Dredd comic book series ... Darkness Descends was Dark Angel's final album to feature original vocalist Don Doty. The album is the first to feature ... Darkness Descends is the second studio album by the American thrash metal band Dark Angel, released on November 17, 1986. ...
In Christianity, the "exterior darkness" or outer darkness is a place referred to three times in the Gospel of Matthew (8:12, ... the outer darkness is thought to be hell; however, many Christians associate the outer darkness more generally as a place of ... "outer darkness" references in Matthew to refer to the last judgment. Today, interpretation of these "outer darkness" verses are ... Matthew 8:11, D-R The use of the term exterior darkness is in Jesus' parable of the wedding feast (also known as the parable of ...
... is a young adult novel by Scott Westerfeld. The second book in his Midnighters series, it was released in ... Touching Darkness begins shortly after The Secret Hour ends. It starts with Jessica's meeting Jonathan in the secret hour. As ... They return to Anathea, who dies from the darkness after Jonathan grants her last wish to fly again. They leave her in front of ... Westerfeld, S. (2004). Touching Darkness, London: Atom. Children and Young Adult Literature portal (Articles lacking in-text ...
... , also known under the title Touched, is a 2019 American thriller film written and directed by Barak Barkan ... Long Silence & Darkness premiered on March 3, 2019, at the DC Independent Film Festival, where it screened under the title ... Silence & Darkness at IMDb Official website (Orphaned articles from July 2022, All orphaned articles, Articles with short ... Rue Morgue praised Silence & Darkness for its acting and tension, which they felt was well developed. High on Films and Battle ...
Darkness, in turn, is the absence of light, and therefore the absence of the same restrictions. Note that Darkness in this ... The darkness that we refer to is the primordial wellspring of Chaos that is the abode of our gods, and unto which their ... Lawless Darkness is the fourth studio album by Swedish black metal band Watain, released through Season of Mist, on 7 June 2010 ... "WATAIN: 'Lawless Darkness' U.S. First-Week Sales Revealed". BLABBERMOUTH.NET. 16 June 2010. Retrieved 15 November 2016. "WATAIN ...
... (2008) is the seventh novel in the Merry Gentry series written by Laurell K. Hamilton. Swallowing Darkness ... Some may enjoy this volume; others may prefer something with more meat on its bones." Swallowing Darkness.(Brief article)(Book ... Audiobook narrated by Claudia Black Publishers Weekly praised Swallowing Darkness, stating "The dreamy development of the ... www.penguinrandomhouseaudio.com/book/74325/swallowing-darkness/ v t e (2008 American novels, American horror novels, American ...
The dictionary definition of darkness at Wiktionary Quotations related to Darkness at Wikiquote Media related to Darkness at ... Artists use darkness to emphasize and contrast the presence of light. Darkness can be used as a counterpoint to areas of ... Exposure to alternating light and darkness (night and day) has caused several evolutionary adaptations to darkness. When a ... "workes of darkness". In Divine Comedy, Dante described hell as "solid darkness staind". In Old English there were three words ...
Wikiquote has quotations related to Eternal Darkness. Eternal Darkness: Sanitys Requiem at MobyGames Eternal Darkness: ... "Nintendos Eternal Darkness Film Contest". Gaming Edge. Archived from the original on May 18, 2011. "Eternal Darkness TV Show ... "Eternal Darkness Films Contest This Week". Nintendo World Report. Billy Berghammer. "Eternal Darkness Films Contest Winner ... "Eternal Darkness: Sanitys Requiem Reviews". GameRankings. Retrieved December 27, 2008. "Eternal Darkness: Sanitys Requiem ( ...
Once we begin to recognize our propensity to deceive ourselves into darkness, we can begin to see signals of how we might ... He tries to convince everyone-Batman included-that darknesss chaos is an ontological reality. But Batman shows that ours is a ... But I find one particular element of this recurrent gloom most compelling-the sense in which this darkness is ... Lenny (Guy Pearce) wrestles with a psychological darkness that stems from finding his wife raped and murdered. That trauma ...
Discover everything you need to know about Castlevania: Curse of Darkness.
Find every single Relic in The Darkness II.  Below we have a video showing all of their locations, as well as brief ... After you get the darkness it is in your path. Grab it! Note: Chapter 19s relics are the only two that come out of order in ... Chapter 19 - Heart of Darkness). To the right after you see Jenny for the first time. Note: Chapter 19s relics are the only ... Find every single Relic in The Darkness II. Below we have a video showing all of their locations, as well as brief descriptions ...
To celebrate the anniversary, fans can now dive even deeper into the sonic and visual worlds of "Darkness" with a new 20-song ... Finally, in celebration of 45 years of "Darkness on The Edge of Town," revisit "The Promise" documentary from 2010 - which ... View Frank Stefankos photo album of rarely-seen material from the "Darkness" era, including new shots from the iconic cover ... Listen to 20 live standouts from The Darkness Tour 78 - all previously unavailable on major streaming platforms - including ...
Decade of Darkness by Artemis Sere at Blurb Books. Ten-year anniversary edition of "Obscurious", the first poetical picturebook ...
The Darkness are getting back together to play the Download Festival five years after splitting up. ... The Darkness reunite for Download Festival. The Darkness are getting back together to play the Download Festival five years ... The Darkness are getting back together to play the Download Festival five years after splitting up. ...
Metacritic aggregates music, game, tv, and movie reviews from the leading critics. Only Metacritic.com uses METASCORES, which let you know at a glance how each item was reviewed.
Lie Down in Darkness is the first novel by American novelist William Styron, published in 1951. Written when he was 26 years ... Lie Down in Darkness is the first novel by American novelist William Styron, published in 1951. Written when he was 26 years ... Lie Down in Darkness is the first novel by American novelist William Styron, published in 1951. Written when he was 26 years ... Among the honors bestowed on Lie Down in Darkness was the prestigious Rome Prize, awarded by the American Academy in Rome and ...
Death in darkness: a new type of cell death discovered in fly guts Peer-Reviewed Publication RIKEN ... Death in darkness: a new type of cell death discovered in fly guts. RIKEN ... They tentatively named the process erebosis, based on the Greek erebos meaning darkness, because the dying cells looked so ...
Cummings reveals the Unionist heart of darkness. * 7 July 2021, 7:03am. ...
Darkness Brutal as its meant to be heard, narrated by Will Damron. Discover the English Audiobook at Audible. Free trial ... Aidan OLinns childhood ended the night he saw a demon kill his mother and mark his sister, Ava, with Darkness. Since then, ... With the fate of humanity in his hands, can Aidan keep the Darkness at bay and accept his brilliant, terrifying destiny? ... and unleashes a new era of war between the forces of Light and the forces of Darkness. ...
I think its good to touch the darkness so we remember why we need Jesus. But thats what we have to do in those moments. ... I forget about His love and His timing and slip into darkness. During one of these moments I was telling my husband, "I just ... Sometimes We Have to Touch the Darkness. Oct 19, 2015 1:30:49 PM , by Sterling Jay ...
Unyielding Faith Amid Darkness. 02/21/2024 Nigeria (International Christian Concern) - Saendos heart condition cast a ... Jesus is the only hope that can bring true life and meaning to those living in darkness in North Korea. So many are crying out ...
Darkness to Light, foster family, foster kids, fostering, healthy touch, Hugging, Stewards of Children ...
Get notified when Darkness bottom is updated. Sign up with Facebook. Sign up with Google. ...
The White Darkness Inspired by the true life account of Henry Worsley, a devoted husband and father, a former soldier, a man of ...
Explosive New Star Trek Into Darkness Ad Premieres ... Explosive New Star Trek Into Darkness Ad Premieres. Explosive ... James T. Kirk kicks it into high gear in this explosive new look at Star Trek Into Darkness,which premiered during The Walking ... The action-packed 60-second spot marks the beginning of Paramounts advertising campaign for Star Trek Into Darkness, which ...
... by Joseph Conrad. "Heart of Darkness advances and withdraws as in a succession of long dark waves borne by ... Heart of Darkness as a Night Journey. Heart of Darkness explores something truer, more fundamental, and distinctly less ... Themes in Heart of Darkness. Self-Discovery. Heart of Darkness concerns Marlow (a projection to whatever degree great or small ... Heart of Darkness was first serialized in Blackwoods Magazine; it appeared soon afterward as a single volume, and Conrad then ...
In darkness let me dwell, the tenors veiled lower register and. seamless phrases, supported by bass viol and lute, took us to ... Tristes; In darkness let me dwell; LachrimÊ CoactÊ; Time stands still; If my. complaints/ Captaine Digory Piper, his Galliard ... product_title=John Dowland: In Darkness. product_by=A review by Claire Seymour. product_id=Above: Woman with a Lute by Johannes ... that in darkness dwell giving way to pianissimo resignation;. exquisite harmonic inflection, with false relations lightly ...
Here comes the sun: giant mirrors to combat towns darkness. Residents of a small valley in Norway will enjoy a brighter winter ...
... co-creator of the Darkness franchise, has told IGN Top Cow is hoping to continue the video game advent… ... Marc Silvestri, co-creator of the Darkness franchise, has told IGN Top Cow is "hoping to continue the video game adventures of ... Or how about combining it with the Darkness and make one based on Artifacts? ...
Nancy Bonus gathered to discuss Shining Light on the Darkness. The discussion took place in Part III of the three part series ... Shining Light on the Darkness - on The Glazov Gang. Nonie Darwish, Eric Allen Bell and Dr. Nancy Bonus open up about what ... and Part III involved a discussion on Shining Light on the Darkness. ...
Concert of Europe is a mod for Victoria 2 Heart of Darkness version 3.04. It sets the start date to 1815-11-20, with close to ... Heart of Darkness support for RTX. Hide this dialog. ... Victoria 2: Heart of Darkness mod , Early Access 2021. *summary ...
EVE Online developer CCP Games has cancelled the development of a fantasy MMO game by the name of World of Darkness. As a ... EVE Online developer cancels vampire-based World of Darkness MMO. By Shawn Knight April 15, 2014, 7:30 8 comments ... World of Darkness players would have assumed the role of vampires blended into normal human society. The game was announced in ... EVE Online developer CCP Games has cancelled the development of a fantasy MMO game by the name of World of Darkness. As a ...
Katy Rose Pools There Will Come a Darkness A Morris Award Finalist for best debut young adult novel A Kirkus Best Book of the ... New York Times bestselling author of SlayerThe Age of Darkness approaches. ... There Will Come a Darkness , Leigh Bardugos Six of Crows meets Kristin Cashores Graceling, with a dash of Winter is Coming, ... Katy Rose Pools There Will Come a Darkness. A Morris Award Finalist for best debut young adult novel. A Kirkus Best Book of ...
Darkness. A Leonard Cohen Songbook with lyrics and chords for guitar, ukulele banjo etc. Also with PDF for printing.. Home ... Darkness, lyrics, chords and PDF for printing. ...
Penny Arcade Adventures: On the Rain-Slick Precipice of Darkness is an RPG-Adventure game series set in the comic-book-meets- ... Hothead is best known for its RPG-adventure game series, On the Rain-Slick Precipice of Darkness, based on the widely popular ... Penny Arcade Adventures: On the Rain-Slick Precipice of Darkness, Episode One has been rated "M" for Mature by the ... Penny Arcade Adventures: On the Rain-Slick Precipice of Darkness Episode One now available to download onto PS3s. ...
  • The emotional response to darkness has generated metaphorical usages of the term in many cultures, often used to describe an unhappy or foreboding feeling. (wikipedia.org)
  • Melatonin is a naturally occurring hormone secreted primarily by the pineal gland in response to darkness. (medscape.com)
  • Darkness, is the direct opposite of lightness, is defined as a lack of illumination, an absence of visible light, or a surface that absorbs light, such as black. (wikipedia.org)
  • The perception of darkness differs from the mere absence of light due to the effects of after images on perception. (wikipedia.org)
  • Exposure to alternating light and darkness (night and day) has caused several evolutionary adaptations to darkness. (wikipedia.org)
  • Also, the light detecting cells in the human eye (rods and cones) will regenerate more unbleached rhodopsin when adapting to darkness. (wikipedia.org)
  • Artists use darkness to emphasize and contrast the presence of light. (wikipedia.org)
  • Color paints are mixed together to create darkness, because each color absorbs certain frequencies of light. (wikipedia.org)
  • The first creation narrative in Judaism and Christianity begins with darkness, into which is introduced the creation of light, and the separation of this light from the darkness (as distinct from the creation of the Sun and Moon on the fourth day of creation). (wikipedia.org)
  • Thus, although both light and darkness are included in the comprehensive works of God, darkness was considered "the second to last plague" (Exodus 10:21), and the location of "weeping and gnashing of teeth" (Matthew 8:12). (wikipedia.org)
  • and there was a thick darkness in all the land of Egypt three days: They saw not one another, neither rose any from his place for three days: but all the children of Israel had light in their dwellings. (fivedoves.com)
  • All the darkness in the world cannot extinguish the light of a single candle. (synchronosart.com)
  • Despite the reigning utter darkness, the light of Peace shall shine. (who.int)
  • how biological clocks respond to light and darkness. (cdc.gov)
  • Using data from National Transportation Safety Board reports, the authors carried out logistic regression analysis with the following variables: age, flight experience, use of a shoulder restraint, weather conditions (visual flight vs. instrument flight), light conditions (daylight vs. darkness), type of aircraft (airplane vs. helicopter), postcrash fire, crash location (airport vs. elsewhere), and state of residence. (cdc.gov)
  • She says, "I talk to them, calm them and advise that they should take care of themselves, clear their mind and search for the light amid this darkness. (who.int)
  • Referring to a time of day, complete darkness occurs when the Sun is more than 18° below the horizon, without the effects of twilight on the night sky. (wikipedia.org)
  • The remainder of this article will present my personal interpretation of what these 3 days of darkness, if it occurs at all, COULD entail. (fivedoves.com)
  • As a poetic term in the Western world, darkness is used to connote the presence of shadows, evil, and foreboding, or in modern parlance, to connote that a story is grim, heavy, and/or depressing. (wikipedia.org)
  • As such, having a supernatural darkness descend on the land as in the time of the Exodus would appear to violate this rule. (fivedoves.com)
  • In other words, I am expecting a different type of darkness to descend upon the land than that illustrated in Exodus. (fivedoves.com)
  • Nancy Anderson, curator of American and British Paintings at the National Gallery of Art, Washington, DC, wrote, In these experimental, complex, and deeply personal paintings, Remington explored the technical and aesthetic difficulties of painting darkness. (cdc.gov)
  • I find Into Darkness no more unenjoyable than The Search For Spock and Generations in the broad scheme of things and it's not objectively the tire fire that The Final Frontier, Insurrection, and Nemesis are. (trekbbs.com)
  • But I find one particular element of this recurrent gloom most compelling-the sense in which this darkness is characteristically psychological. (christianitytoday.com)
  • Darkness Below is the largest active online caving and underground news site worldwide, but there are plenty of other caving and mining blogs out there you can browse at your leisure. (darknessbelow.co.uk)
  • In the years since Eternal Darkness' release, it has been regarded as one of the greatest games of all time, as well as one of the best horror games ever made. (wikipedia.org)
  • Sephie Michaela Deviluke, the Queen of Deviluke and the mother to Momo, Lala, and Nana from "To Love-Ru Darkness," appears before you wearing the "Darkness" outfit -- or sort of wearing it, anyway! (play-asia.com)
  • Two cult classics clash for the first time in an epic crossover miniseries: ARMY OF DARKNESS VS. BUBBA HO-TEP. (midtowncomics.com)
  • This period of darkness is lengthened by the return to Standard Time, which immediately precedes Halloween. (cdc.gov)
  • Spooky Hand of Darkness' Doppelbock beer recipe by Forest Brewery. (brewersfriend.com)
  • And the Lord said unto Moses, Stretch out thine hand toward heaven, that there may be darkness over the land of Egypt, even darkness which may be felt. (fivedoves.com)
  • Even so, such darkness should still be noticeable by those who are watching, versus simply occurring in the unnoticeable spirit world. (fivedoves.com)
  • In Old English there were three words that could mean darkness: heolstor, genip, and sceadu. (wikipedia.org)
  • Mel Gibson opens in "Edge of Darkness" this Friday. (showbiz411.com)
  • Star Trek Into Darkness opens domestically (US & Canada) on May 17th, which is actually a week after it opens in a number of international markets (including the UK, Germany and Australia). (trekmovie.com)
  • This summer is going to be an especially exciting time on Turner Classic Movies, as TCM launches a two-month film noir festival, the "TCM Summer of Darkness. (blogspot.com)
  • Part of Ground Breaker's Roll Up Door Series, Imperial Darkness is a dark gluten-free beer that incorporates coffee and cacao nibs and will be available in 22 oz. bottles and on draft. (brewpublic.com)
  • Imperial Darkness is an imperial dark ale made with deeply roasted chestnuts, lentils, and cacao nibs from TCHO . (brewpublic.com)
  • Do buy his book if you want to understand more fully the woman who said, "If I ever become a saint, I will be a saint of darkness. (wordonfire.org)
  • Feel free to share anything about Ultima I: The First Age of Darkness (1986) here! (goodolddays.net)