Lanthanum
Hyperphosphatemia
Phosphorus Metabolism Disorders
Tooth Permeability
Intercellular Junctions
Thulium
Benzoin
Phosphorus Compounds
Calcium
Metals, Rare Earth
Freeze Fracturing
Cerium
Phosphorus
Microscopy, Electron
Colubridae
Cell Membrane Permeability
Zeatin
Dopamine stimulates salivary duct cells in the cockroach Periplaneta americana. (1/803)
This study examines whether the salivary duct cells of the cockroach Periplaneta americana can be stimulated by the neurotransmitters dopamine and serotonin. We have carried out digital Ca2+-imaging experiments using the Ca2+-sensitive dye fura-2 and conventional intracellular recordings from isolated salivary glands. Dopamine evokes a slow, almost tonic, and reversible dose-dependent elevation in [Ca2+]i in the duct cells. Upon stimulation with 10(-)6 mol l-1 dopamine, [Ca2+]i rises from 48+/-4 nmol l-1 to 311+/-43 nmol l-1 (mean +/- s.e.m., N=18) within 200-300 s. The dopamine-induced elevation in [Ca2+]i is absent in Ca2+-free saline and is blocked by 10(-)4 mol l-1 La3+, indicating that dopamine induces an influx of Ca2+ across the basolateral membrane of the duct cells. Stimulation with 10(-)6 mol l-1 dopamine causes the basolateral membrane to depolarize from -67+/-1 to -41+/-2 mV (N=10). This depolarization is also blocked by La3+ and is abolished when Na+ in the bath solution is reduced to 10 mmol l-1. Serotonin affects neither [Ca2+]i nor the basolateral membrane potential of the duct cells. These data indicate that the neurotransmitter dopamine, which has previously been shown to stimulate fluid secretion from the glands, also stimulates the salivary duct cells, suggesting that dopamine controls their most probable function, the modification of primary saliva. (+info)Increased calcium entry into dystrophin-deficient muscle fibres of MDX and ADR-MDX mice is reduced by ion channel blockers. (2/803)
1. Single fibres were enzymatically isolated from interosseus muscles of dystrophic MDX mice, myotonic-dystrophic double mutant ADR-MDX mice and C57BL/10 controls. The fibres were kept in cell culture for up to 2 weeks for the study of Ca2+ homeostasis and sarcolemmal Ca2+ permeability. 2. Resting levels of intracellular free Ca2+, determined with the fluorescent Ca2+ indicator fura-2, were slightly higher in MDX (63 +/- 20 nM; means +/- s.d.; n = 454 analysed fibres) and ADR-MDX (65 +/- 12 nM; n = 87) fibres than in controls (51 +/- 20 nM; n = 265). 3. The amplitudes of electrically induced Ca2+ transients did not differ between MDX fibres and controls. Decay time constants of Ca2+ transients ranged between 10 and 55 ms in both genotypes. In 50 % of MDX fibres (n = 68), but in only 20 % of controls (n = 54), the decay time constants were > 35 ms. 4. Bath application of Mn2+ resulted in a progressive quench of fura-2 fluorescence emitted from the fibres. The quench rate was about 2 times higher in MDX fibres (3.98 +/- 1.9 % min-1; n = 275) than in controls (2.03 +/- 1.4 % min-1; n = 204). The quench rate in ADR-MDX fibres (2.49 +/- 1.4 % min-1; n = 87) was closer to that of controls. 5. The Mn2+ influx into MDX fibres was reduced to 10 % by Gd3+, to 19 % by La3+ and to 47 % by Ni2+ (all at 50 microM). Bath application of 50 microM amiloride inhibited the Mn2+ influx to 37 %. 6. We conclude that in isolated, resting MDX muscle fibres the membrane permeability for divalent cations is increased. The presumed additional influx of Ca2+ occurs through ion channels, but is well compensated for by effective cellular Ca2+ transport systems. The milder dystrophic phenotype of ADR-MDX mice is correlated with a smaller increase of their sarcolemmal Ca2+ permeability. (+info)Thapsigargin inhibits a potassium conductance and stimulates calcium influx in the intact rat lens. (3/803)
1. An increase in lens cell calcium has long been associated with cortical cataract. Recently, it has been shown that thapsigargin induces a rise in lens cell calcium by release from endoplasmic reticulum stores. The effects of this rise on the optical and membrane characteristics of the lens were studied in the isolated rat lens. 2. The electrical characteristics of the isolated, perifused rat lens were measured using a two-internal microelectrode technique that permits measurement of plasma membrane conductance (Gm), membrane potential (Vm) and junctional conductance in the intact lens. 3. Thapsigargin (1 microM) induced a rapid overall depolarization of Vm that was accompanied by first a decrease and then an increase in Gm. 4. Replacing external Na+ with tetraethylammonium (TEA) abolished the decrease in Gm. However, a transient increase phase was still observed. 5. The changes in conductance were further characterized by measuring 22Na+ and 45Ca2+ influxes into the isolated lens. Thapsigargin (1 microM) induced a transient increase in 45Ca2+, but did not affect Na+ influx. 6. The Ca2+ channel blocker La3+ (10 microM) totally inhibited the thapsigargin-induced Ca2+ influx. It also blocked the increase in Gm observed in control and in Na+-free-TEA medium. In the absence of external calcium, thapsigargin induced a small depolarization in Vm. 7. These data indicate that thapsigargin induces both a decrease in K+ conductance and an increase in Ca2+ conductance. These probably result from release of stored Ca2+ and subsequent activation of store-operated Ca2+ channels (capacitative Ca2+ entry). 8. Thapsigargin application over the time course of these experiments (24 h) had no effect on junctional conductance or on the transparency of the lens. (+info)Sequential activation of different Ca2+ entry pathways upon cholinergic stimulation in mouse pancreatic acinar cells. (4/803)
1. We have studied capacitative calcium entry (CCE) under different experimental conditions in fura-2-loaded mouse pancreatic acinar cells by digital microscopic fluorimetry. CCE was investigated during [Ca2+]i decay after cell stimulation with a supramaximal concentration of ACh (10 microM) or during Ca2+ readmission in Ca2+-depleted cells (pretreated with thapsigargin or ACh). 2. La3+ and Zn2+ (100 microM) inhibited CCE during Ca2+ readmission but had negligible effects during ACh decay. In contrast flufenamic acid (100 microM), an inhibitor of non-selective cation channels, genistein (10 microM), a broad-range tyrosine kinase inhibitor, and piceatannol (10 microM), an inhibitor specific for non-receptor Syk tyrosine kinase, inhibited CCE during ACh decay but not during Ca2+ reintroduction. 3. Simultaneous detection of Mn2+ entry and [Ca2+]i measurement showed that, in the presence of extracellular calcium, application of 100 microM Mn2+ during ACh decay resulted in manganese influx without alteration of calcium influx, whilst when applied during Ca2+ readmission, Mn2+ entry was significantly smaller and induced a clear inhibition of CCE. 4. Application of the specific protein kinase C inhibitor GF109293X (3 microM) reduced CCE in Ca2+-depleted cells, whereas the activator phorbol 12-myristate, 13-acetate (3 microM) increased Ca2+ entry. 5. Based on these results we propose that cholinergic stimulation of mouse pancreatic acinar cells induces Ca2+ influx with an initial phase operated by a non-specific cation channel, sensitive to flufenamic acid and tyrosine kinase inhibitors but insensitive to lanthanum and divalent cations, followed by a moderately Ca2+-selective conductance inhibited by lanthanum and divalent cations. (+info)Calcium block of Na+ channels and its effect on closing rate. (5/803)
Calcium ion transiently blocks Na+ channels, and it shortens the time course for closing of their activation gates. We examined the relation between block and closing kinetics by using the Na+ channels natively expressed in GH3 cells, a clonal line of rat pituitary cells. To simplify analysis, inactivation of the Na+ channels was destroyed by including papain in the internal medium. All divalent cations tested, and trivalent La3+, blocked a progressively larger fraction of the channels as their concentration increased, and they accelerated the closing of the Na+ channel activation gate. For calcium, the most extensively studied cation, there is an approximately linear relation between the fraction of the channels that are calcium-blocked and the closing rate. Extrapolation of the data to very low calcium suggests that closing rate is near zero when there is no block. Analysis shows that, almost with certainty, the channels can close when occupied by calcium. The analysis further suggests that the channels close preferentially or exclusively from the calcium-blocked state. (+info)Isolation and characterization of a Ca2+ -binding polysaccharide associated with coccoliths of Emiliania huxleyi (Lohmann) Kamptner. (6/803)
C-occolithophoridae, a group of mostly unicellular algae, possess a cell wall containing calcified plates, called coccoliths. The coccoliths from the species Emilania huxleyi (Lohmann) Kamptner contain a water-soluble acid polysaccharide. In this paper we describe the isolation and some characteristic properties of the polysaccharide, in particular its Ca2+ -binding capacity. A large-scale cultivation of the Coccolithophoridae was worked out and a new procedure for isolating coccoliths was developed. The polysaccharide obtained from the coccoliths contained two types of monobasic acid groups in a total amount of 1.8 mumol/mg polysaccharide. One type consisted of weakly acid groups which were identified as uronic acids. The nature of the stronger acid groups remains to be established. The ratio between the respective groups was 1:0.8. Studies with 45Ca2+ demonstrated that the isolated polysaccharide is capable of binding Ca2+. Equilibrium dialysis revealed that the maximum amount of Ca2+ which can be bound in 0.92 +/- 0.05 mumol/mg polysaccharide. Flow-rate dialysis experiments strongly suggested the presence of two classes of Ca2+ -binding sites differing in affinity for Ca2+. High-affinity sites (dissociation constant Kd for Ca2+ :2.2 +/- 1.0 X 10(-5) M) were found to be present in amounts (0.38 +/- 0.04 mumol/mg polysaccharide) approximately equivalent to the strongly acid monovalent groups mentioned above (0.8 mumol/mg polysaccharide). Low-affinity sites (Kd for Ca2+: -11 +/- 39 X 10(-5) M) were estimated at 0.74 +/- 0.11 mumol/mg polysaccharide. Although this figure could be determined less accurately, it is suggested that the uronic acids (1.0 mumol/mg polysaccharide) are identical to the low-affinity sites. Preferential binding of Ca2+ occurred in a 100-fold excess of Na+ and Mg2+ as was shown by gel filtration. A 100-fold excess of Sr2+ inhibited Ca2+ binding to a great extent while no Ca2+ was bound in the presence of an equimolar amount of La3+. The dissociation constants of the high-affinity sites for Na+, Mg2+, Sr2+ and La3+ (in the presence of Ca2+) were determined with the flow-rate dialysis technique. They confirm the order of binding preference found with gel filtration. A polysaccharide with similar properties could be isolated from subfossil coccoliths of E. hyxleyi (about 1000 years old). The possible role of the polysaccharide as a heterogeneous matrix in coccolith formation is discussed. (+info)Evidence for calcium inactivation during hormone release in the rat neurohypophysis. (7/803)
1. A study has been made of the relationship between 45Ca uptake into and hormone release from isolated rat neurohypophyses incubated in vitro. 2. Hormone secretion is triggered by high-K (56 mM) but long exposure to the stimulus does not generate a maintained release of hormone. 3. When hormone release began to wane, addition of Ba of La increased hormone output which suggests that the decline in output did not result from depletion of the neurosecretory granules at the nerve terminals. 4. 45Ca uptake is enhanced in the presence of high-K concentration, but the initial high rate declines during long exposure to the potassium stimulus with a time constant similar to that of the decline in hormone release. 5. After a period of incubation in a K-rich, calcium-free medium, addition of calcium to the medium induced hormone release. The magnitude of this release was dependent on the time of exposure to excess potassium. 6. After inactivation of secretion, mobilization of internal calcium by means of a calcium ionophore increased hormone release. (+info)Manganese-dependent propagated action potentials and their depression by electrical stimulation in guinea-pig myocardium perfused by sodium-free media. (8/803)
1. Propagated action potentials were recorded in right ventricular papillary muscles from guinea-pig heart while exposed to Na-free, Ca-free and Mg-free solutions containing Mn. 2. When Na was totally replaced by 95 mM-Mn the overshoot was about 45 mV while the resting potential was about -90mV. 3. The overshoot of action potentials was increased by about 20-30 mV per tenfold increase of Mn concentration over the range of 2-50 mM. 4. Similar increases of overshoots with increasing of Mn concentration also occurred in the presence of 0-6 mM-Ca. Increasing of Ca from 5 to 20 mM had little influence on the overshoot but shortened the duration of the Mn-dependent action potential in the presence of 5 mM-MN. 5 Mn-dependent action potentials were not depressed by 3 X 10(5) M tetrodotoxin but by La. 6. These results suggest that Mn passes through the slow inward current channel to generate the action potential seen under the Na-free condition. 7. The overshoot and duration of the Mn-dependent action potential decreased with stimulation. At stimulus frequencies (Hz) of 0-5, 0-2, 0-1, 0-017 and 0-0033 the overshoot of action potential in 5 mM-Mn Tyrode decreased by 0-5-1 mV per an action potential. This depression of the action potential is explained by assuming intracellular accumulation of Mn. (+info)Lanthanum is not a medical term itself, but it is a chemical element with the symbol "La" and atomic number 57. It is a soft, ductile, silvery-white metal that belongs to the lanthanide series in the periodic table.
However, in medical contexts, lanthanum may be mentioned as a component of certain medications or medical devices. For example, lanthanum carbonate (trade name Fosrenol) is a medication used to treat hyperphosphatemia (elevated levels of phosphate in the blood) in patients with chronic kidney disease. Lanthanum carbonate works by binding to phosphate in the gastrointestinal tract, preventing its absorption into the bloodstream.
It is important to note that lanthanum compounds are not biologically active and do not have any specific medical effects on their own. Any medical uses of lanthanum are related to its physical or chemical properties, rather than its biological activity.
Hyperphosphatemia is a medical condition characterized by an excessively high level of phosphate (a form of the chemical element phosphorus) in the blood. Phosphate is an important component of various biological molecules, such as DNA, RNA, and ATP, and it plays a crucial role in many cellular processes, including energy metabolism and signal transduction.
In healthy individuals, the concentration of phosphate in the blood is tightly regulated within a narrow range to maintain normal physiological functions. However, when the phosphate level rises above this range (typically defined as a serum phosphate level greater than 4.5 mg/dL or 1.46 mmol/L), it can lead to hyperphosphatemia.
Hyperphosphatemia can result from various underlying medical conditions, including:
* Kidney dysfunction: The kidneys are responsible for filtering excess phosphate out of the blood and excreting it in the urine. When the kidneys fail to function properly, they may be unable to remove enough phosphate, leading to its accumulation in the blood.
* Hypoparathyroidism: The parathyroid glands produce a hormone called parathyroid hormone (PTH), which helps regulate calcium and phosphate levels in the body. In hypoparathyroidism, the production of PTH is insufficient, leading to an increase in phosphate levels.
* Hyperparathyroidism: In contrast, excessive production of PTH can also lead to hyperphosphatemia by increasing the release of phosphate from bones and decreasing its reabsorption in the kidneys.
* Excessive intake of phosphate-rich foods or supplements: Consuming large amounts of phosphate-rich foods, such as dairy products, nuts, and legumes, or taking phosphate supplements can raise blood phosphate levels.
* Tumor lysis syndrome: This is a complication that can occur after the treatment of certain types of cancer, particularly hematological malignancies. The rapid destruction of cancer cells releases large amounts of intracellular contents, including phosphate, into the bloodstream, leading to hyperphosphatemia.
* Rhabdomyolysis: This is a condition in which muscle tissue breaks down, releasing its contents, including phosphate, into the bloodstream. It can be caused by various factors, such as trauma, infection, or drug toxicity.
Hyperphosphatemia can have several adverse effects on the body, including calcification of soft tissues, kidney damage, and metabolic disturbances. Therefore, it is essential to diagnose and manage hyperphosphatemia promptly to prevent complications. Treatment options may include dietary modifications, medications that bind phosphate in the gastrointestinal tract, and dialysis in severe cases.
Phosphorus metabolism disorders refer to a group of conditions that affect the body's ability to properly regulate the levels and utilization of phosphorus. Phosphorus is an essential mineral that plays a critical role in many biological processes, including energy production, bone formation, and nerve function.
Disorders of phosphorus metabolism can result from genetic defects, kidney dysfunction, vitamin D deficiency, or other medical conditions. These disorders can lead to abnormal levels of phosphorus in the blood, which can cause a range of symptoms, including muscle weakness, bone pain, seizures, and respiratory failure.
Examples of phosphorus metabolism disorders include:
1. Hypophosphatemia: This is a condition characterized by low levels of phosphorus in the blood. It can be caused by various factors, such as malnutrition, vitamin D deficiency, and kidney dysfunction.
2. Hyperphosphatemia: This is a condition characterized by high levels of phosphorus in the blood. It can be caused by kidney failure, tumor lysis syndrome, and certain medications.
3. Hereditary hypophosphatemic rickets: This is a genetic disorder that affects the body's ability to regulate vitamin D and phosphorus metabolism. It can lead to weakened bones and skeletal deformities.
4. Oncogenic osteomalacia: This is a rare condition that occurs when tumors produce substances that interfere with phosphorus metabolism, leading to bone pain and weakness.
Treatment for phosphorus metabolism disorders depends on the underlying cause of the disorder and may include dietary changes, supplements, medications, or surgery.
I am not able to find a single medical definition for "tooth permeability" as it is not a widely used or recognized term in dental or medical literature. However, I can provide some context that might help you understand the concept.
In general, permeability refers to the ability of a material or tissue to allow fluids or gases to pass through it. In the case of teeth, they are composed of several layers: the outer enamel, dentin, and the inner pulp. Enamel is highly mineralized and does not have living cells, making it relatively impermeable to substances. Dentin, on the other hand, contains microscopic tubules filled with fluid and nerve endings, which can potentially allow for some permeability.
However, when people talk about tooth permeability in a dental context, they might be referring to the ability of various substances (such as acids, bacteria, or chemicals) to penetrate through the enamel and dentin layers and reach the inner pulp chamber. This can lead to dental issues like tooth decay, sensitivity, or infection.
In summary, while "tooth permeability" is not a standard medical term, it may refer to the ability of substances to pass through the various layers of the tooth and potentially cause damage.
Intercellular junctions are specialized areas of contact between two or more adjacent cells in multicellular organisms. They play crucial roles in maintaining tissue structure and function by regulating the movement of ions, molecules, and even larger cellular structures from one cell to another. There are several types of intercellular junctions, including:
1. Tight Junctions (Zonulae Occludentes): These are the most apical structures in epithelial and endothelial cells, forming a virtually impermeable barrier to prevent the paracellular passage of solutes and water between the cells. They create a tight seal by connecting the transmembrane proteins of adjacent cells, such as occludin and claudins.
2. Adherens Junctions: These are located just below the tight junctions and help maintain cell-to-cell adhesion and tissue integrity. Adherens junctions consist of cadherin proteins that form homophilic interactions with cadherins on adjacent cells, as well as intracellular adaptor proteins like catenins, which connect to the actin cytoskeleton.
3. Desmosomes: These are another type of cell-to-cell adhesion structure, primarily found in tissues that experience mechanical stress, such as the skin and heart. Desmosomes consist of cadherin proteins (desmocadherins) that interact with each other and connect to intermediate filaments (keratin in epithelial cells) via plakoglobin and desmoplakin.
4. Gap Junctions: These are specialized channels that directly connect the cytoplasm of adjacent cells, allowing for the exchange of small molecules, ions, and second messengers. Gap junctions consist of connexin proteins that form hexameric structures called connexons in the plasma membrane of each cell. When two connexons align, they create a continuous pore or channel between the cells.
In summary, intercellular junctions are essential for maintaining tissue structure and function by regulating paracellular transport, cell-to-cell adhesion, and intercellular communication.
Thulium is not a medical term, but a chemical element in the periodic table with atomic number 69. It's a rare earth metal that is silvery-gray and has a bright blue emission line in its spectrum. In medicine, thulium is used in some medical devices such as thulium lasers for the treatment of various conditions like kidney stones and benign prostatic hyperplasia (BPH). However, it's not a term that would be used to describe a medical condition or diagnosis.
Benzoin, in a medical context, most commonly refers to a type of compound called a benzoin resin or benzoin tincture, which is derived from the bark of certain trees in the genus Styrax. It has been used traditionally in medicine for its antiseptic and expectorant properties.
Benzoin resin is obtained by making incisions in the bark of the tree and allowing the resin to exude and harden. The solidified resin is then collected and may be ground into a powder or dissolved in alcohol to create a tincture.
Benzoin tincture has been used topically as an antiseptic and to help heal wounds, ulcers, and burns. It has also been used as an expectorant to help clear respiratory congestion and coughs.
It is important to note that benzoin should be used with caution, as it can cause skin irritation and allergic reactions in some people. Additionally, benzoin tincture contains a significant amount of alcohol and should not be taken internally without the guidance of a healthcare professional.
Phosphorus compounds refer to chemical substances that contain phosphorus (P) combined with one or more other elements. Phosphorus can form a variety of compounds due to its ability to exist in several oxidation states, most commonly +3 and +5.
In biological systems, phosphorus is an essential element for life, playing crucial roles in energy transfer, metabolism, and structural components of cells. Some common examples of phosphorus compounds include:
1. Phosphoric acid (H3PO4): A weak triprotic acid that forms salts called phosphates when combined with metal ions or basic radicals.
2. Phosphates (PO4^3-): The salt or ester form of phosphoric acid, widely found in nature and essential for various biological processes such as bone formation, energy metabolism, and nucleic acid synthesis.
3. Phosphorus pentachloride (PCl5): A pungent, white crystalline solid used in organic chemistry as a chlorinating agent.
4. Phosphorus trichloride (PCl3): A colorless liquid with a suffocating odor, used in the production of various chemical compounds, including pharmaceuticals and agrochemicals.
5. Dicalcium phosphate (CaHPO4): A calcium salt of phosphoric acid, commonly found in mineral supplements and used as a dietary supplement for animals and humans.
6. Adenosine triphosphate (ATP): A high-energy molecule that stores and transfers energy within cells, playing a critical role in metabolic processes such as muscle contraction and biosynthesis.
Phosphorus compounds have numerous applications across various industries, including agriculture, food processing, pharmaceuticals, and chemical manufacturing.
Calcium is an essential mineral that is vital for various physiological processes in the human body. The medical definition of calcium is as follows:
Calcium (Ca2+) is a crucial cation and the most abundant mineral in the human body, with approximately 99% of it found in bones and teeth. It plays a vital role in maintaining structural integrity, nerve impulse transmission, muscle contraction, hormonal secretion, blood coagulation, and enzyme activation.
Calcium homeostasis is tightly regulated through the interplay of several hormones, including parathyroid hormone (PTH), calcitonin, and vitamin D. Dietary calcium intake, absorption, and excretion are also critical factors in maintaining optimal calcium levels in the body.
Hypocalcemia refers to low serum calcium levels, while hypercalcemia indicates high serum calcium levels. Both conditions can have detrimental effects on various organ systems and require medical intervention to correct.
Rare earth metals, also known as rare earth elements, are a group of 17 metallic elements found in the periodic table. They include:
1. Lanthanum (La)
2. Cerium (Ce)
3. Praseodymium (Pr)
4. Neodymium (Nd)
5. Promethium (Pm)
6. Samarium (Sm)
7. Europium (Eu)
8. Gadolinium (Gd)
9. Terbium (Tb)
10. Dysprosium (Dy)
11. Holmium (Ho)
12. Erbium (Er)
13. Thulium (Tm)
14. Ytterbium (Yb)
15. Lutetium (Lu)
1
Phosphates, in a medical context, refer to the salts or esters of phosphoric acid. Phosphates play crucial roles in various biological processes within the human body. They are essential components of bones and teeth, where they combine with calcium to form hydroxyapatite crystals. Phosphates also participate in energy transfer reactions as phosphate groups attached to adenosine diphosphate (ADP) and adenosine triphosphate (ATP). Additionally, they contribute to buffer systems that help maintain normal pH levels in the body.
Abnormal levels of phosphates in the blood can indicate certain medical conditions. High phosphate levels (hyperphosphatemia) may be associated with kidney dysfunction, hyperparathyroidism, or excessive intake of phosphate-containing products. Low phosphate levels (hypophosphatemia) might result from malnutrition, vitamin D deficiency, or certain diseases affecting the small intestine or kidneys. Both hypophosphatemia and hyperphosphatemia can have significant impacts on various organ systems and may require medical intervention.
Freeze fracturing is not a medical term itself, but it is a technique used in the field of electron microscopy, which is a type of imaging commonly used in scientific research and medical fields to visualize structures at a very small scale, such as cells and cellular components.
In freeze fracturing, a sample is rapidly frozen to preserve its structure and then fractured or split along a plane of weakness, often along the membrane of a cell. The freshly exposed surface is then shadowed with a thin layer of metal, such as platinum or gold, to create a replica of the surface. This replica can then be examined using an electron microscope to reveal details about the structure and organization of the sample at the molecular level.
Freeze fracturing is particularly useful for studying membrane structures, such as lipid bilayers and protein complexes, because it allows researchers to visualize these structures in their native state, without the need for staining or other chemical treatments that can alter or damage the samples.
Cerium is a chemical element with the symbol "Ce" and atomic number 58. It belongs to the lanthanide series in the periodic table and is the second element in this series. Cerium is a solid at room temperature, with a silver-white appearance and has a face-centered cubic crystal structure.
In medicine, cerium oxide nanoparticles have been studied for their potential therapeutic applications, particularly in neurodegenerative diseases such as Alzheimer's and Parkinson's disease. These nanoparticles are believed to have antioxidant properties that can help protect neurons from oxidative stress and inflammation. However, more research is needed to fully understand the safety and efficacy of cerium-based therapies in medical treatments.
Phosphorus is an essential mineral that is required by every cell in the body for normal functioning. It is a key component of several important biomolecules, including adenosine triphosphate (ATP), which is the primary source of energy for cells, and deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), which are the genetic materials in cells.
Phosphorus is also a major constituent of bones and teeth, where it combines with calcium to provide strength and structure. In addition, phosphorus plays a critical role in various metabolic processes, including energy production, nerve impulse transmission, and pH regulation.
The medical definition of phosphorus refers to the chemical element with the atomic number 15 and the symbol P. It is a highly reactive non-metal that exists in several forms, including white phosphorus, red phosphorus, and black phosphorus. In the body, phosphorus is primarily found in the form of organic compounds, such as phospholipids, phosphoproteins, and nucleic acids.
Abnormal levels of phosphorus in the body can lead to various health problems. For example, high levels of phosphorus (hyperphosphatemia) can occur in patients with kidney disease or those who consume large amounts of phosphorus-rich foods, and can contribute to the development of calcification of soft tissues and cardiovascular disease. On the other hand, low levels of phosphorus (hypophosphatemia) can occur in patients with malnutrition, vitamin D deficiency, or alcoholism, and can lead to muscle weakness, bone pain, and an increased risk of infection.
Electron microscopy (EM) is a type of microscopy that uses a beam of electrons to create an image of the sample being examined, resulting in much higher magnification and resolution than light microscopy. There are several types of electron microscopy, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), and reflection electron microscopy (REM).
In TEM, a beam of electrons is transmitted through a thin slice of the sample, and the electrons that pass through the sample are focused to form an image. This technique can provide detailed information about the internal structure of cells, viruses, and other biological specimens, as well as the composition and structure of materials at the atomic level.
In SEM, a beam of electrons is scanned across the surface of the sample, and the electrons that are scattered back from the surface are detected to create an image. This technique can provide information about the topography and composition of surfaces, as well as the structure of materials at the microscopic level.
REM is a variation of SEM in which the beam of electrons is reflected off the surface of the sample, rather than scattered back from it. This technique can provide information about the surface chemistry and composition of materials.
Electron microscopy has a wide range of applications in biology, medicine, and materials science, including the study of cellular structure and function, disease diagnosis, and the development of new materials and technologies.
Colubridae is a family of snakes that includes a large majority of the world's snake species. It is a diverse group, with members ranging from relatively small and harmless species to large and potentially dangerous ones. Some colubrids have evolved specialized adaptations for specific hunting strategies or defense mechanisms.
Colubridae species are found worldwide, except in Antarctica, and they inhabit various environments such as forests, grasslands, deserts, and wetlands. Many colubrids are constrictors, meaning they kill their prey by wrapping their bodies around it and squeezing until the prey can no longer breathe.
It is worth noting that some colubrid species were previously classified under other families such as Natricidae or Dipsadidae, but recent genetic studies have led to a reclassification of these snakes into Colubridae.
Some examples of colubrids include rat snakes, gopher snakes, racers, whip snakes, and tree snakes. The family also includes some well-known species like the king cobra (Ophiophagus hannah) and the black mamba (Dendroaspis polylepis), which are among the longest and most venomous snakes in the world. However, it is important to note that not all colubrids are venomous, and those that are typically pose little threat to humans due to their mild venom or shy nature.
Cell membrane permeability refers to the ability of various substances, such as molecules and ions, to pass through the cell membrane. The cell membrane, also known as the plasma membrane, is a thin, flexible barrier that surrounds all cells, controlling what enters and leaves the cell. Its primary function is to protect the cell's internal environment and maintain homeostasis.
The permeability of the cell membrane depends on its structure, which consists of a phospholipid bilayer interspersed with proteins. The hydrophilic (water-loving) heads of the phospholipids face outward, while the hydrophobic (water-fearing) tails face inward, creating a barrier that is generally impermeable to large, polar, or charged molecules.
However, specific proteins within the membrane, called channels and transporters, allow certain substances to cross the membrane. Channels are protein structures that span the membrane and provide a pore for ions or small uncharged molecules to pass through. Transporters, on the other hand, are proteins that bind to specific molecules and facilitate their movement across the membrane, often using energy in the form of ATP.
The permeability of the cell membrane can be influenced by various factors, such as temperature, pH, and the presence of certain chemicals or drugs. Changes in permeability can have significant consequences for the cell's function and survival, as they can disrupt ion balances, nutrient uptake, waste removal, and signal transduction.
A neurilemma, also known as a schwannoma or neurolemmoma, is a type of benign tumor that arises from the nerve sheath. Specifically, it develops from the Schwann cells, which produce the myelin sheath that insulates and protects the nerves. Neurilemmomas can occur anywhere in the body where there are nerves, but they most commonly affect the cranial nerves, particularly the eighth cranial nerve (the vestibulocochlear nerve). They can also be found along the spine and in the extremities.
Neurilemmomas typically appear as solitary, slow-growing, and well-circumscribed masses that do not usually cause pain or other symptoms unless they compress nearby structures. In some cases, however, they may cause hearing loss, tinnitus, balance problems, or facial nerve paralysis when they affect the cranial nerves. Treatment typically involves surgical removal of the tumor, and the prognosis is generally good, with a low risk of recurrence.
Zeatin is not a medical term per se, but it is a significant compound in the field of plant biology and agriculture. It is a type of cytokinin, which is a class of hormones that play crucial roles in plant growth and development. Specifically, zeatin is involved in cell division, differentiation, and delaying senescence (aging) in plants.
In a broader biological context, understanding the functions of phytohormones like zeatin can have implications for agricultural practices and crop management, which may indirectly impact human health through improved food production and quality.
APF, or Acidulated Phosphate Fluoride, is a dental product that contains fluoride ion in the form of sodium fluoride. It is used as a topical agent to prevent tooth decay by promoting remineralization and inhibiting demineralization of tooth enamel. The acidulated phosphate component helps to maintain a stable pH level and enhance fluoride absorption. It is typically applied in a dental office as a part of professional dental care.