Calcium Signaling: Signal transduction mechanisms whereby calcium mobilization (from outside the cell or from intracellular storage pools) to the cytoplasm is triggered by external stimuli. Calcium signals are often seen to propagate as waves, oscillations, spikes, sparks, or puffs. The calcium acts as an intracellular messenger by activating calcium-responsive proteins.Calcium Channels: Voltage-dependent cell membrane glycoproteins selectively permeable to calcium ions. They are categorized as L-, T-, N-, P-, Q-, and R-types based on the activation and inactivation kinetics, ion specificity, and sensitivity to drugs and toxins. The L- and T-types are present throughout the cardiovascular and central nervous systems and the N-, P-, Q-, & R-types are located in neuronal tissue.Calcium, Dietary: Calcium compounds used as food supplements or in food to supply the body with calcium. Dietary calcium is needed during growth for bone development and for maintenance of skeletal integrity later in life to prevent osteoporosis.Calcium Carbonate: Carbonic acid calcium salt (CaCO3). An odorless, tasteless powder or crystal that occurs in nature. It is used therapeutically as a phosphate buffer in hemodialysis patients and as a calcium supplement.Calcium Phosphates: Calcium salts of phosphoric acid. These compounds are frequently used as calcium supplements.Calcium Isotopes: Stable calcium atoms that have the same atomic number as the element calcium, but differ in atomic weight. Ca-42-44, 46, and 48 are stable calcium isotopes.Calcium Chloride: A salt used to replenish calcium levels, as an acid-producing diuretic, and as an antidote for magnesium poisoning.Calcium Channels, L-Type: Long-lasting voltage-gated CALCIUM CHANNELS found in both excitable and nonexcitable tissue. They are responsible for normal myocardial and vascular smooth muscle contractility. Five subunits (alpha-1, alpha-2, beta, gamma, and delta) make up the L-type channel. The alpha-1 subunit is the binding site for calcium-based antagonists. Dihydropyridine-based calcium antagonists are used as markers for these binding sites.Calcium Oxalate: The calcium salt of oxalic acid, occurring in the urine as crystals and in certain calculi.Calcium Gluconate: The calcium salt of gluconic acid. The compound has a variety of uses, including its use as a calcium replenisher in hypocalcemic states.Calcium Radioisotopes: Unstable isotopes of calcium that decay or disintegrate emitting radiation. Ca atoms with atomic weights 39, 41, 45, 47, 49, and 50 are radioactive calcium isotopes.Calcium Compounds: Inorganic compounds that contain calcium as an integral part of the molecule.Calcium Channels, N-Type: CALCIUM CHANNELS that are concentrated in neural tissue. Omega toxins inhibit the actions of these channels by altering their voltage dependence.Egtazic Acid: A chelating agent relatively more specific for calcium and less toxic than EDETIC ACID.Calcium Channel Agonists: Agents that increase calcium influx into calcium channels of excitable tissues. This causes vasoconstriction in VASCULAR SMOOTH MUSCLE and/or CARDIAC MUSCLE cells as well as stimulation of insulin release from pancreatic islets. Therefore, tissue-selective calcium agonists have the potential to combat cardiac failure and endocrinological disorders. They have been used primarily in experimental studies in cell and tissue culture.Calcimycin: An ionophorous, polyether antibiotic from Streptomyces chartreusensis. It binds and transports CALCIUM and other divalent cations across membranes and uncouples oxidative phosphorylation while inhibiting ATPase of rat liver mitochondria. The substance is used mostly as a biochemical tool to study the role of divalent cations in various biological systems.Calcium Hydroxide: A white powder prepared from lime that has many medical and industrial uses. It is in many dental formulations, especially for root canal filling.Phosphorus: A non-metal element that has the atomic symbol P, atomic number 15, and atomic weight 31. It is an essential element that takes part in a broad variety of biochemical reactions.Nifedipine: A potent vasodilator agent with calcium antagonistic action. It is a useful anti-anginal agent that also lowers blood pressure.Calcium Sulfate: A calcium salt that is used for a variety of purposes including: building materials, as a desiccant, in dentistry as an impression material, cast, or die, and in medicine for immobilizing casts and as a tablet excipient. It exists in various forms and states of hydration. Plaster of Paris is a mixture of powdered and heat-treated gypsum.Parathyroid Hormone: A polypeptide hormone (84 amino acid residues) secreted by the PARATHYROID GLANDS which performs the essential role of maintaining intracellular CALCIUM levels in the body. Parathyroid hormone increases intracellular calcium by promoting the release of CALCIUM from BONE, increases the intestinal absorption of calcium, increases the renal tubular reabsorption of calcium, and increases the renal excretion of phosphates.Membrane Potentials: The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).Magnesium: A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.Chelating Agents: Chemicals that bind to and remove ions from solutions. Many chelating agents function through the formation of COORDINATION COMPLEXES with METALS.Fura-2: A fluorescent calcium chelating agent which is used to study intracellular calcium in tissues.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Calcium Citrate: A colorless crystalline or white powdery organic, tricarboxylic acid occurring in plants, especially citrus fruits, and used as a flavoring agent, as an antioxidant in foods, and as a sequestrating agent. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Kinetics: The rate dynamics in chemical or physical systems.Thapsigargin: A sesquiterpene lactone found in roots of THAPSIA. It inhibits CA(2+)-TRANSPORTING ATPASE mediated uptake of CALCIUM into SARCOPLASMIC RETICULUM.S100 Calcium Binding Protein G: A calbindin protein found in many mammalian tissues, including the UTERUS, PLACENTA, BONE, PITUITARY GLAND, and KIDNEYS. In intestinal ENTEROCYTES it mediates intracellular calcium transport from apical to basolateral membranes via calcium binding at two EF-HAND MOTIFS. Expression is regulated in some tissues by VITAMIN D.Ryanodine Receptor Calcium Release Channel: A tetrameric calcium release channel in the SARCOPLASMIC RETICULUM membrane of SMOOTH MUSCLE CELLS, acting oppositely to SARCOPLASMIC RETICULUM CALCIUM-TRANSPORTING ATPASES. It is important in skeletal and cardiac excitation-contraction coupling and studied by using RYANODINE. Abnormalities are implicated in CARDIAC ARRHYTHMIAS and MUSCULAR DISEASES.Calcium Pyrophosphate: An inorganic pyrophosphate which affects calcium metabolism in mammals. Abnormalities in its metabolism occur in some human diseases, notably HYPOPHOSPHATASIA and pseudogout (CHONDROCALCINOSIS).Calcium Metabolism Disorders: Disorders in the processing of calcium in the body: its absorption, transport, storage, and utilization.Verapamil: A calcium channel blocker that is a class IV anti-arrhythmia agent.Calcium-Binding Proteins: Proteins to which calcium ions are bound. They can act as transport proteins, regulator proteins, or activator proteins. They typically contain EF HAND MOTIFS.Dihydropyridines: Pyridine moieties which are partially saturated by the addition of two hydrogen atoms in any position.Cytosol: Intracellular fluid from the cytoplasm after removal of ORGANELLES and other insoluble cytoplasmic components.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Lanthanum: Lanthanum. The prototypical element in the rare earth family of metals. It has the atomic symbol La, atomic number 57, and atomic weight 138.91. Lanthanide ion is used in experimental biology as a calcium antagonist; lanthanum oxide improves the optical properties of glass.Patch-Clamp Techniques: An electrophysiologic technique for studying cells, cell membranes, and occasionally isolated organelles. All patch-clamp methods rely on a very high-resistance seal between a micropipette and a membrane; the seal is usually attained by gentle suction. The four most common variants include on-cell patch, inside-out patch, outside-out patch, and whole-cell clamp. Patch-clamp methods are commonly used to voltage clamp, that is control the voltage across the membrane and measure current flow, but current-clamp methods, in which the current is controlled and the voltage is measured, are also used.Calcium Channels, P-Type: CALCIUM CHANNELS located within the PURKINJE CELLS of the cerebellum. They are involved in stimulation-secretion coupling of neurons.Diltiazem: A benzothiazepine derivative with vasodilating action due to its antagonism of the actions of CALCIUM ion on membrane functions.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Potassium: An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.Kidney Calculi: Stones in the KIDNEY, usually formed in the urine-collecting area of the kidney (KIDNEY PELVIS). Their sizes vary and most contains CALCIUM OXALATE.Hypocalcemia: Reduction of the blood calcium below normal. Manifestations include hyperactive deep tendon reflexes, Chvostek's sign, muscle and abdominal cramps, and carpopedal spasm. (Dorland, 27th ed)Neurons: The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.Aequorin: A photoprotein isolated from the bioluminescent jellyfish Aequorea. It emits visible light by an intramolecular reaction when a trace amount of calcium ion is added. The light-emitting moiety in the bioluminescence reaction is believed to be 2-amino-3-benzyl-5-(p-hydroxyphenyl)pyrazine (AF-350).Intracellular Fluid: The fluid inside CELLS.Calmodulin: A heat-stable, low-molecular-weight activator protein found mainly in the brain and heart. The binding of calcium ions to this protein allows this protein to bind to cyclic nucleotide phosphodiesterases and to adenyl cyclase with subsequent activation. Thereby this protein modulates cyclic AMP and cyclic GMP levels.Receptors, Calcium-Sensing: A class of G-protein-coupled receptors that react to varying extracellular CALCIUM levels. Calcium-sensing receptors in the PARATHYROID GLANDS play an important role in the maintenance of calcium HOMEOSTASIS by regulating the release of PARATHYROID HORMONE. They differ from INTRACELLULAR CALCIUM-SENSING PROTEINS which sense intracellular calcium levels.Calcium Channels, Q-Type: CALCIUM CHANNELS located in the neurons of the brain.Strontium: An element of the alkaline earth family of metals. It has the atomic symbol Sr, atomic number 38, and atomic weight 87.62.Inositol 1,4,5-Trisphosphate Receptors: Intracellular receptors that bind to INOSITOL 1,4,5-TRISPHOSPHATE and play an important role in its intracellular signaling. Inositol 1,4,5-trisphosphate receptors are calcium channels that release CALCIUM in response to increased levels of inositol 1,4,5-trisphosphate in the CYTOPLASM.Hypercalcemia: Abnormally high level of calcium in the blood.Ionophores: Chemical agents that increase the permeability of biological or artificial lipid membranes to specific ions. Most ionophores are relatively small organic molecules that act as mobile carriers within membranes or coalesce to form ion permeable channels across membranes. Many are antibiotics, and many act as uncoupling agents by short-circuiting the proton gradient across mitochondrial membranes.Vitamin D: A vitamin that includes both CHOLECALCIFEROLS and ERGOCALCIFEROLS, which have the common effect of preventing or curing RICKETS in animals. It can also be viewed as a hormone since it can be formed in SKIN by action of ULTRAVIOLET RAYS upon the precursors, 7-dehydrocholesterol and ERGOSTEROL, and acts on VITAMIN D RECEPTORS to regulate CALCIUM in opposition to PARATHYROID HORMONE.Fluorescent Dyes: Agents that emit light after excitation by light. The wave length of the emitted light is usually longer than that of the incident light. Fluorochromes are substances that cause fluorescence in other substances, i.e., dyes used to mark or label other compounds with fluorescent tags.Ionomycin: A divalent calcium ionophore that is widely used as a tool to investigate the role of intracellular calcium in cellular processes.Electrophysiology: The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.Rabbits: The species Oryctolagus cuniculus, in the family Leporidae, order LAGOMORPHA. Rabbits are born in burrows, furless, and with eyes and ears closed. In contrast with HARES, rabbits have 22 chromosome pairs.Calcium Channels, R-Type: CALCIUM CHANNELS located in the neurons of the brain. They are inhibited by the marine snail toxin, omega conotoxin MVIIC.Inositol 1,4,5-Trisphosphate: Intracellular messenger formed by the action of phospholipase C on phosphatidylinositol 4,5-bisphosphate, which is one of the phospholipids that make up the cell membrane. Inositol 1,4,5-trisphosphate is released into the cytoplasm where it releases calcium ions from internal stores within the cell's endoplasmic reticulum. These calcium ions stimulate the activity of B kinase or calmodulin.Sodium: A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.Rats, Sprague-Dawley: A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.Bone and Bones: A specialized CONNECTIVE TISSUE that is the main constituent of the SKELETON. The principle cellular component of bone is comprised of OSTEOBLASTS; OSTEOCYTES; and OSTEOCLASTS, while FIBRILLAR COLLAGENS and hydroxyapatite crystals form the BONE MATRIX.Intestinal Absorption: Uptake of substances through the lining of the INTESTINES.Caffeine: A methylxanthine naturally occurring in some beverages and also used as a pharmacological agent. Caffeine's most notable pharmacological effect is as a central nervous system stimulant, increasing alertness and producing agitation. It also relaxes SMOOTH MUSCLE, stimulates CARDIAC MUSCLE, stimulates DIURESIS, and appears to be useful in the treatment of some types of headache. Several cellular actions of caffeine have been observed, but it is not entirely clear how each contributes to its pharmacological profile. Among the most important are inhibition of cyclic nucleotide PHOSPHODIESTERASES, antagonism of ADENOSINE RECEPTORS, and modulation of intracellular calcium handling.Adenosine Triphosphate: An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.Homeostasis: The processes whereby the internal environment of an organism tends to remain balanced and GVIA: A neurotoxic peptide, which is a cleavage product (VIa) of the omega-Conotoxin precursor protein contained in venom from the marine snail, CONUS geographus. It is an antagonist of CALCIUM CHANNELS, N-TYPE.Myocardium: The muscle tissue of the HEART. It is composed of striated, involuntary muscle cells (MYOCYTES, CARDIAC) connected to form the contractile pump to generate blood flow.Calcinosis: Pathologic deposition of calcium salts in tissues.Signal Transduction: The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway.Nitrendipine: A calcium channel blocker with marked vasodilator action. It is an effective antihypertensive agent and differs from other calcium channel blockers in that it does not reduce glomerular filtration rate and is mildly natriuretic, rather than sodium retentive.Hydrogen-Ion Concentration: The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH = log 1/2[1/(H+)], where (H+) is the hydrogen ion concentration in gram equivalents per liter of solution. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Cell Line: Established cell cultures that have the potential to propagate indefinitely.Calcitriol: The physiologically active form of vitamin D. It is formed primarily in the kidney by enzymatic hydroxylation of 25-hydroxycholecalciferol (CALCIFEDIOL). Its production is stimulated by low blood calcium levels and parathyroid hormone. Calcitriol increases intestinal absorption of calcium and phosphorus, and in concert with parathyroid hormone increases bone resorption.Ion Channels: Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS.Ryanodine: A methylpyrrole-carboxylate from RYANIA that disrupts the RYANODINE RECEPTOR CALCIUM RELEASE CHANNEL to modify CALCIUM release from SARCOPLASMIC RETICULUM resulting in alteration of MUSCLE CONTRACTION. It was previously used in INSECTICIDES. It is used experimentally in conjunction with THAPSIGARGIN and other inhibitors of CALCIUM ATPASE uptake of calcium into SARCOPLASMIC RETICULUM.Nimodipine: A calcium channel blockader with preferential cerebrovascular activity. It has marked cerebrovascular dilating effects and lowers blood pressure.Ion Transport: The movement of ions across energy-transducing cell membranes. Transport can be active, passive or facilitated. Ions may travel by themselves (uniport), or as a group of two or more ions in the same (symport) or opposite (antiport) directions.Ion Channel Gating: The opening and closing of ion channels due to a stimulus. The stimulus can be a change in membrane potential (voltage-gated), drugs or chemical transmitters (ligand-gated), or a mechanical deformation. Gating is thought to involve conformational changes of the ion channel which alters selective permeability.Parathyroid Glands: Two pairs of small oval-shaped glands located in the front and the base of the NECK and adjacent to the two lobes of THYROID GLAND. They secrete PARATHYROID HORMONE that regulates the balance of CALCIUM; PHOSPHORUS; and MAGNESIUM in the A family of structurally related neurotoxic peptides from mollusk venom that inhibit voltage-activated entry of calcium into the presynaptic membrane. They selectively inhibit N-, P-, and Q-type calcium channels.Oxalates: Derivatives of OXALIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that are derived from the ethanedioic acid structure.Rats, Wistar: A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.Isradipine: A potent antagonist of CALCIUM CHANNELS that is highly selective for VASCULAR SMOOTH MUSCLE. It is effective in the treatment of chronic stable angina pectoris, hypertension, and congestive cardiac failure.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Minerals: Native, inorganic or fossilized organic substances having a definite chemical composition and formed by inorganic reactions. They may occur as individual crystals or may be disseminated in some other mineral or rock. (Grant & Hackh's Chemical Dictionary, 5th ed; McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Sarcoplasmic Reticulum Calcium-Transporting ATPases: Calcium-transporting ATPases that catalyze the active transport of CALCIUM into the SARCOPLASMIC RETICULUM vesicles from the CYTOPLASM. They are primarily found in MUSCLE CELLS and play a role in the relaxation of MUSCLES.Muscle Contraction: A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.Calbindins: Calcium-binding proteins that are found in DISTAL KIDNEY TUBULES, INTESTINES, BRAIN, and other tissues where they bind, buffer and transport cytoplasmic calcium. Calbindins possess a variable number of EF-HAND MOTIFS which contain calcium-binding sites. Some isoforms are regulated by VITAMIN D.Cholecalciferol: Derivative of 7-dehydroxycholesterol formed by ULTRAVIOLET RAYS breaking of the C9-C10 bond. It differs from ERGOCALCIFEROL in having a single bond between C22 and C23 and lacking a methyl group at C24.Biological Transport, Active: The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy.Electric Stimulation: Use of electric potential or currents to elicit biological responses.Xanthenes: Compounds with three aromatic rings in linear arrangement with an OXYGEN in the center ring.Nicardipine: A potent calcium channel blockader with marked vasodilator action. It has antihypertensive properties and is effective in the treatment of angina and coronary spasms without showing cardiodepressant effects. It has also been used in the treatment of asthma and enhances the action of specific antineoplastic agents.Extracellular Space: Interstitial space between cells, occupied by INTERSTITIAL FLUID as well as amorphous and fibrous substances. For organisms with a CELL WALL, the extracellular space includes everything outside of the CELL MEMBRANE including the PERIPLASM and the cell wall.Models, Biological: Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.Muscles: Contractile tissue that produces movement in animals.Aniline CompoundsAmino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Potassium Chloride: A white crystal or crystalline powder used in BUFFERS; FERTILIZERS; and EXPLOSIVES. It can be used to replenish ELECTROLYTES and restore WATER-ELECTROLYTE BALANCE in treating HYPOKALEMIA.Myocardial Contraction: Contractile activity of the MYOCARDIUM.Endoplasmic Reticulum: A system of cisternae in the CYTOPLASM of many cells. In places the endoplasmic reticulum is continuous with the plasma membrane (CELL MEMBRANE) or outer membrane of the nuclear envelope. If the outer surfaces of the endoplasmic reticulum membranes are coated with ribosomes, the endoplasmic reticulum is said to be rough-surfaced (ENDOPLASMIC RETICULUM, ROUGH); otherwise it is said to be smooth-surfaced (ENDOPLASMIC RETICULUM, SMOOTH). (King & Stansfield, A Dictionary of Genetics, 4th ed)Rats, Inbred Strains: Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations or by parent x offspring matings carried out with certain restrictions. This also includes animals with a long history of closed colony breeding.Calcium Dobesilate: A drug used to reduce hemorrhage in diabetic retinopathy.Mibefradil: A benzimidazoyl-substituted tetraline that selectively binds and inhibits CALCIUM CHANNELS, T-TYPE.Biological Transport: The movement of materials (including biochemical substances and drugs) through a biological system at the cellular level. The transport can be across cell membranes and epithelial layers. It also can occur within intracellular compartments and extracellular compartments.Cell Membrane Permeability: A quality of cell membranes which permits the passage of solvents and solutes into and out of cells.Bone Density: The amount of mineral per square centimeter of BONE. This is the definition used in clinical practice. Actual bone density would be expressed in grams per milliliter. It is most frequently measured by X-RAY ABSORPTIOMETRY or TOMOGRAPHY, X RAY COMPUTED. Bone density is an important predictor for OSTEOPOROSIS.Plasma Membrane Calcium-Transporting ATPases: Calcium-transporting ATPases found on the PLASMA MEMBRANE that catalyze the active transport of CALCIUM from the CYTOPLASM into the extracellular space. They play a role in maintaining a CALCIUM gradient across plasma membrane.Electron Probe Microanalysis: Identification and measurement of ELEMENTS and their location based on the fact that X-RAYS emitted by an element excited by an electron beam have a wavelength characteristic of that element and an intensity related to its concentration. It is performed with an electron microscope fitted with an x-ray spectrometer, in scanning or transmission mode.Cyclic AMP: An adenine nucleotide containing one phosphate group which is esterified to both the 3'- and 5'-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and ACTH.Buffers: A chemical system that functions to control the levels of specific ions in solution. When the level of hydrogen ion in solution is controlled the system is called a pH buffer.Electric Conductivity: The ability of a substrate to allow the passage of ELECTRONS.Absorption: The physical or physiological processes by which substances, tissue, cells, etc. take up or take in other substances or energy.Dietary Supplements: Products in capsule, tablet or liquid form that provide dietary ingredients, and that are intended to be taken by mouth to increase the intake of nutrients. Dietary supplements can include macronutrients, such as proteins, carbohydrates, and fats; and/or MICRONUTRIENTS, such as VITAMINS; MINERALS; and PHYTOCHEMICALS.Arsenazo III: Metallochrome indicator that changes color when complexed to the calcium ion under physiological conditions. It is used to measure local calcium ion concentrations in vivo.Cattle: Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.Calcium-Calmodulin-Dependent Protein Kinase Type 2: A multifunctional calcium-calmodulin-dependent protein kinase subtype that occurs as an oligomeric protein comprised of twelve subunits. It differs from other enzyme subtypes in that it lacks a phosphorylatable activation domain that can respond to CALCIUM-CALMODULIN-DEPENDENT PROTEIN KINASE KINASE.Terpenes: A class of compounds composed of repeating 5-carbon units of HEMITERPENES.Aminoquinolines: Quinolines substituted in any position by one or more amino groups.Cations, Divalent: Positively charged atoms, radicals or groups of atoms with a valence of plus 2, which travel to the cathode or negative pole during electrolysis.Ruthenium Red: An inorganic dye used in microscopy for differential staining and as a diagnostic reagent. In research this compound is used to study changes in cytoplasmic concentrations of calcium. Ruthenium red inhibits calcium transport through membrane channels.Enzyme Inhibitors: Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction.Protein Kinase C: An serine-threonine protein kinase that requires the presence of physiological concentrations of CALCIUM and membrane PHOSPHOLIPIDS. The additional presence of DIACYLGLYCEROLS markedly increases its sensitivity to both calcium and phospholipids. The sensitivity of the enzyme can also be increased by PHORBOL ESTERS and it is believed that protein kinase C is the receptor protein of tumor-promoting phorbol esters.Benzofurans: Compounds that contain a BENZENE ring fused to a furan ring.Dantrolene: Skeletal muscle relaxant that acts by interfering with excitation-contraction coupling in the muscle fiber. It is used in spasticity and other neuromuscular abnormalities. Although the mechanism of action is probably not central, dantrolene is usually grouped with the central muscle relaxants.Calcification, Physiologic: Process by which organic tissue becomes hardened by the physiologic deposit of calcium salts.Dairy Products: Raw and processed or manufactured milk and milk-derived products. These are usually from cows (bovine) but are also from goats, sheep, reindeer, and water buffalo.Sodium-Calcium Exchanger: An electrogenic ion exchange protein that maintains a steady level of calcium by removing an amount of calcium equal to that which enters the cells. It is widely distributed in most excitable membranes, including the brain and heart.Protein Binding: The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.Osmolar Concentration: The concentration of osmotically active particles in solution expressed in terms of osmoles of solute per liter of solution. Osmolality is expressed in terms of osmoles of solute per kilogram of solvent.Edetic Acid: A chelating agent that sequesters a variety of polyvalent cations such as CALCIUM. It is used in pharmaceutical manufacturing and as a food additive.Phosphorylation: The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety.Type C Phospholipases: A subclass of phospholipases that hydrolyze the phosphoester bond found in the third position of GLYCEROPHOSPHOLIPIDS. Although the singular term phospholipase C specifically refers to an enzyme that catalyzes the hydrolysis of PHOSPHATIDYLCHOLINE (EC, it is commonly used in the literature to refer to broad variety of enzymes that specifically catalyze the hydrolysis of PHOSPHATIDYLINOSITOLS.Heart: The hollow, muscular organ that maintains the circulation of the blood.Neuronal Calcium-Sensor Proteins: A family of intracellular calcium-sensing proteins found predominately in NEURONS and PHOTORECEPTOR CELLS. They contain EF HAND MOTIFS and undergo conformational changes upon calcium-binding. Neuronal calcium-sensor proteins interact with other regulatory proteins to mediate physiological responses to a change in intracellular calcium concentration.Urinary Calculi: Low-density crystals or stones in any part of the URINARY TRACT. Their chemical compositions often include CALCIUM OXALATE, magnesium ammonium phosphate (struvite), CYSTINE, or URIC ACID.Spider Venoms: Venoms of arthropods of the order Araneida of the ARACHNIDA. The venoms usually contain several protein fractions, including ENZYMES, hemolytic, neurolytic, and other TOXINS, IVA: A neuropeptide toxin from the venom of the funnel web spider, Agelenopsis aperta. It inhibits CALCIUM CHANNELS, P-TYPE by altering the voltage-dependent gating so that very large depolarizations are needed for channel opening. It also inhibits CALCIUM CHANNELS, Q-TYPE.Gallopamil: Coronary vasodilator that is an analog of iproveratril (VERAPAMIL) with one more methoxy group on the benzene ring.Microscopy, Confocal: A light microscopic technique in which only a small spot is illuminated and observed at a time. An image is constructed through point-by-point scanning of the field in this manner. Light sources may be conventional or laser, and fluorescence or transmitted observations are possible.Calcium Ionophores: Chemical agents that increase the permeability of CELL MEMBRANES to CALCIUM ions.Flunarizine: Flunarizine is a selective calcium entry blocker with calmodulin binding properties and histamine H1 blocking activity. It is effective in the prophylaxis of migraine, occlusive peripheral vascular disease, vertigo of central and peripheral origin, and as an adjuvant in the therapy of epilepsy.Enzyme Activation: Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme.Hyperparathyroidism: A condition of abnormally elevated output of PARATHYROID HORMONE (or PTH) triggering responses that increase blood CALCIUM. It is characterized by HYPERCALCEMIA and BONE RESORPTION, eventually leading to bone diseases. PRIMARY HYPERPARATHYROIDISM is caused by parathyroid HYPERPLASIA or PARATHYROID NEOPLASMS. SECONDARY HYPERPARATHYROIDISM is increased PTH secretion in response to HYPOCALCEMIA, usually caused by chronic KIDNEY DISEASES.Myocytes, Cardiac: Striated muscle cells found in the heart. They are derived from cardiac myoblasts (MYOBLASTS, CARDIAC).Binding Sites: The parts of a macromolecule that directly participate in its specific combination with another molecule.Dogs: The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)Gallic Acid: A colorless or slightly yellow crystalline compound obtained from nutgalls. It is used in photography, pharmaceuticals, and as an analytical reagent.Exocytosis: Cellular release of material within membrane-limited vesicles by fusion of the vesicles with the CELL MEMBRANE.Kidney: Body organ that filters blood for the secretion of URINE and that regulates ion concentrations.Diet: Regular course of eating and drinking adopted by a person or animal.Hypoparathyroidism: A condition caused by a deficiency of PARATHYROID HORMONE (or PTH). It is characterized by HYPOCALCEMIA and hyperphosphatemia. Hypocalcemia leads to TETANY. The acquired form is due to removal or injuries to the PARATHYROID GLANDS. The congenital form is due to mutations of genes, such as TBX1; (see DIGEORGE SYNDROME); CASR encoding CALCIUM-SENSING RECEPTOR; or PTH encoding parathyroid hormone.Cytoplasm: The part of a cell that contains the CYTOSOL and small structures excluding the CELL NUCLEUS; MITOCHONDRIA; and large VACUOLES. (Glick, Glossary of Biochemistry and Molecular Biology, 1990)Hypercalciuria: Excretion of abnormally high level of CALCIUM in the URINE, greater than 4 mg/kg/day.Microscopy, Fluorescence: Microscopy of specimens stained with fluorescent dye (usually fluorescein isothiocyanate) or of naturally fluorescent materials, which emit light when exposed to ultraviolet or blue light. Immunofluorescence microscopy utilizes antibodies that are labeled with fluorescent dye.Calbindin 1: A calcium-binding protein that mediates calcium HOMEOSTASIS in KIDNEYS, BRAIN, and other tissues. It is found in well-defined populations of NEURONS and is involved in CALCIUM SIGNALING and NEURONAL PLASTICITY. It is regulated in some tissues by VITAMIN D.Alkaline Phosphatase: An enzyme that catalyzes the conversion of an orthophosphoric monoester and water to an alcohol and orthophosphate. EC An atom or group of atoms that have a positive or negative electric charge due to a gain (negative charge) or loss (positive charge) of one or more electrons. Atoms with a positive charge are known as CATIONS; those with a negative charge are ANIONS.Carbachol: A slowly hydrolyzed CHOLINERGIC AGONIST that acts at both MUSCARINIC RECEPTORS and NICOTINIC RECEPTORS.Animals, Newborn: Refers to animals in the period of time just after birth.Trifluoperazine: A phenothiazine with actions similar to CHLORPROMAZINE. It is used as an antipsychotic and an antiemetic.Hippocampus: A curved elevation of GRAY MATTER extending the entire length of the floor of the TEMPORAL HORN of the LATERAL VENTRICLE (see also TEMPORAL LOBE). The hippocampus proper, subiculum, and DENTATE GYRUS constitute the hippocampal formation. Sometimes authors include the ENTORHINAL CORTEX in the hippocampal formation.Tetrodotoxin: An aminoperhydroquinazoline poison found mainly in the liver and ovaries of fishes in the order TETRAODONTIFORMES, which are eaten. The toxin causes paresthesia and paralysis through interference with neuromuscular conduction.Muscle, Smooth, Vascular: The nonstriated involuntary muscle tissue of blood vessels.Inositol Phosphates: Phosphoric acid esters of inositol. They include mono- and polyphosphoric acid esters, with the exception of inositol hexaphosphate which is PHYTIC ACID.Presynaptic Terminals: The distal terminations of axons which are specialized for the release of neurotransmitters. Also included are varicosities along the course of axons which have similar specializations and also release transmitters. Presynaptic terminals in both the central and peripheral nervous systems are included.Osteoporosis: Reduction of bone mass without alteration in the composition of bone, leading to fractures. Primary osteoporosis can be of two major types: postmenopausal osteoporosis (OSTEOPOROSIS, POSTMENOPAUSAL) and age-related or senile osteoporosis.Intracellular Membranes: Thin structures that encapsulate subcellular structures or ORGANELLES in EUKARYOTIC CELLS. They include a variety of membranes associated with the CELL NUCLEUS; the MITOCHONDRIA; the GOLGI APPARATUS; the ENDOPLASMIC RETICULUM; LYSOSOMES; PLASTIDS; and VACUOLES.Neurotransmitter Agents: Substances used for their pharmacological actions on any aspect of neurotransmitter systems. Neurotransmitter agents include agonists, antagonists, degradation inhibitors, uptake inhibitors, depleters, precursors, and modulators of receptor function.Lasalocid: Cationic ionophore antibiotic obtained from Streptomyces lasaliensis that, among other effects, dissociates the calcium fluxes in muscle fibers. It is used as a coccidiostat, especially in poultry.Spectrometry, Fluorescence: Measurement of the intensity and quality of fluorescence.Synaptic Transmission: The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.Synapses: Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions.Cadmium: An element with atomic symbol Cd, atomic number 48, and atomic weight 114. It is a metal and ingestion will lead to CADMIUM POISONING.Durapatite: The mineral component of bones and teeth; it has been used therapeutically as a prosthetic aid and in the prevention and treatment of osteoporosis.Second Messenger Systems: Systems in which an intracellular signal is generated in response to an intercellular primary messenger such as a hormone or neurotransmitter. They are intermediate signals in cellular processes such as metabolism, secretion, contraction, phototransduction, and cell growth. Examples of second messenger systems are the adenyl cyclase-cyclic AMP system, the phosphatidylinositol diphosphate-inositol triphosphate system, and the cyclic GMP system.Mitochondria: Semiautonomous, self-reproducing organelles that occur in the cytoplasm of all cells of most, but not all, eukaryotes. Each mitochondrion is surrounded by a double limiting membrane. The inner membrane is highly invaginated, and its projections are called cristae. Mitochondria are the sites of the reactions of oxidative phosphorylation, which result in the formation of ATP. They contain distinctive RIBOSOMES, transfer RNAs (RNA, TRANSFER); AMINO ACYL T RNA SYNTHETASES; and elongation and termination factors. Mitochondria depend upon genes within the nucleus of the cells in which they reside for many essential messenger RNAs (RNA, MESSENGER). Mitochondria are believed to have arisen from aerobic bacteria that established a symbiotic relationship with primitive protoeukaryotes. (King & Stansfield, A Dictionary of Genetics, 4th ed)Phosphorus, Dietary: Phosphorus used in foods or obtained from food. This element is a major intracellular component which plays an important role in many biochemical pathways relating to normal physiological functions. High concentrations of dietary phosphorus can cause nephrocalcinosis which is associated with impaired kidney function. Low concentrations of dietary phosphorus cause an increase in calcitriol in the blood and osteoporosis.Oxalic Acid: A strong dicarboxylic acid occurring in many plants and vegetables. It is produced in the body by metabolism of glyoxylic acid or ascorbic acid. It is not metabolized but excreted in the urine. It is used as an analytical reagent and general reducing agent.RNA, Messenger: RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.Calcitonin: A peptide hormone that lowers calcium concentration in the blood. In humans, it is released by thyroid cells and acts to decrease the formation and absorptive activity of osteoclasts. Its role in regulating plasma calcium is much greater in children and in certain diseases than in normal adults.Nickel: A trace element with the atomic symbol Ni, atomic number 28, and atomic weight 58.69. It is a cofactor of the enzyme UREASE.Nephrolithiasis: Formation of stones in the KIDNEY.EF Hand Motifs: Calcium-binding motifs composed of two helices (E and F) joined by a loop. Calcium is bound by the loop region. These motifs are found in many proteins that are regulated by calcium.Apatites: A group of phosphate minerals that includes ten mineral species and has the general formula X5(YO4)3Z, where X is usually calcium or lead, Y is phosphorus or arsenic, and Z is chlorine, fluorine, or OH-. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Tetradecanoylphorbol Acetate: A phorbol ester found in CROTON OIL with very effective tumor promoting activity. It stimulates the synthesis of both DNA and RNA.Boron Compounds: Inorganic or organic compounds that contain boron as an integral part of the molecule.Glutamic Acid: A non-essential amino acid naturally occurring in the L-form. Glutamic acid is the most common excitatory neurotransmitter in the CENTRAL NERVOUS SYSTEM.Calcineurin: A CALCIUM and CALMODULIN-dependent serine/threonine protein phosphatase that is composed of the calcineurin A catalytic subunit and the calcineurin B regulatory subunit. Calcineurin has been shown to dephosphorylate a number of phosphoproteins including HISTONES; MYOSIN LIGHT CHAIN; and the regulatory subunits of CAMP-DEPENDENT PROTEIN KINASES. It is involved in the regulation of signal transduction and is the target of an important class of immunophilin-immunosuppressive drug complexes.Indoles: Benzopyrroles with the nitrogen at the number one carbon adjacent to the benzyl portion, in contrast to ISOINDOLES which have the nitrogen away from the six-membered ring.CitratesHydroxycholecalciferols: Hydroxy analogs of vitamin D 3; (CHOLECALCIFEROL); including CALCIFEDIOL; CALCITRIOL; and 24,25-DIHYDROXYVITAMIN D 3.Crystallization: The formation of crystalline substances from solutions or melts. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Membrane Proteins: Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.Muscle, Smooth: Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed)Stimulation, Chemical: The increase in a measurable parameter of a PHYSIOLOGICAL PROCESS, including cellular, microbial, and plant; immunological, cardiovascular, respiratory, reproductive, urinary, digestive, neural, musculoskeletal, ocular, and skin physiological processes; or METABOLIC PROCESS, including enzymatic and other pharmacological processes, by a drug or other chemical.

Further evidence that prostaglandins inhibit the release of noradrenaline from adrenergic nerve terminals by restriction of availability of calcium. (1/62881)

1 Guinea-pig vasa deferentia were continuously superfused after labelling the transmitter stores with [3H](-)-noradrenaline. Release of [3H]-(-)-noradrenaline was induced by transmural nerve stimulation. 2 Prostglandin E2 (14 nM) drastically reduced the release of [3H]-(-)-noradrenaline, while tetraethylammonium (2 mM), rubidium (6 mM), phenoxybenzamine (3 muM) each in the presence or absence of Uptake 1 or 2 blockade, and prolonged pulse duration (from 0.5 to 2.0 ms) all significantly increased the release of [3H]-(-)-noradrenaline per nerve impulse. 3 The inhibitory effect of prostaglandin E2 on evoked release of [3H]-(-)-noradrenaline was significantly reduced by tetraethylammonium, rubidium and prolonged pulse duration, whilst it was actually enhanced by phenoxybenzamine. This indicates that increased release of noradrenaline per nerve impulse does not per se counteract the inhibitory effect of prostaglandin E2. 4 It is concluded that tetraethylammonium, rubidium and prolonged pulse duration counteracted the inhibitory effect of prostaglandin E2 on T3H]-(-)-noradrenaline release by promoting calcium influx during the nerve action potential. The results are consistent with, and add more weight to the view that prostaglandins inhibit the release of noradrenaline by restriction of calcium availability.  (+info)

Abnormal calcium metabolism in normocalcaemic sarcoidosis. (2/62881)

In studies of calcium metabolism in 13 unselected patients with untreated sarcoidosis all were normocalcaemic but five had hypercalcuria. All had normal renal function. Calcium absorption was indexed by a double isotope test. 45Ca hyperabsorption occurred in six patients. Ten kinetic studies were carried out with 47Ca and in six bone turnover was increased. 45Ca absorption correlated well with the calculated bone uptake rate of calcium, and with urine calcium excretion. These results suggest that in sarcoidosis abnormalities in calcium metabolism are fairly common although they rarely result in sustained hypercalcaemia.  (+info)

Automatic activity in depolarized guinea pig ventricular myocardium. Characteristics and mechanisms. (3/62881)

Membrane potential was changed uniformly in segments, 0.7-1.0 mm long, of guinea pig papillary muscles excised from the right ventricle by using extracellular polarizing current pulses applied across two electrically insulated cf preparations superfused with Tyrode's solution at maximum diastolic membrane potentials ranging from-35.2+/-7.5 (threshold) to +4.0+/-9.2 mV. The average maximum dV/dt of RAD ranged from 17.1 to 18.0 V/sec within a membrane potential range of -40 to +20 mV. Raising extracellular Ca2+ concentration [Ca2+]0 from 1.8 to 6.8 mM, or application of isoproterenol (10(-6)g/ml) enhanced the rate of RAD, but lowering [Ca2+]0 to 0.4 mM or exposure to MnCl2 (6 mM) abolished RAD. RAD were enhanced by lowering extracellular K+ concentration [K+]0 from 5.4 to 1.5 mM. RAD were suppressed in 40% of fibers by raising [K+]0 to 15.4 mM, and in all fibers by raising [K+]0 to 40.4 mM. This suppression was due to increased [K+]0 and not to K-induced depolarization because it persisted when membrane potential was held by means of a conditioning hyperpolarizing puled gradually after maximum repolarization. These observations suggest that the development of RAD in depolarized myocardium is associated with a time-dependent decrease in outward current (probably K current) and with increase in the background inward current, presumably flowing through the slow cha-nel carrying Ca or Na ions, or both.  (+info)

Intrarenal site of action of calcium on renin secretion in dogs. (4/62881)

We studied the effects of intrarenal calcium infusion on renin secretion in sodium-depleted dogs in an attempt to elucidate the major site of calcium-induced inhibition of renin release. Both calcium chloride and calcium gluconate reduced renal blood flow and renin secretion while renal perfusion pressure was unchanged. These data indicate that calcium inhibition of renin secretion did not occur primarily at the renal vascular receptor; decreased renal blood flow is usually associated with increased renin secretion. Calcium chloride infusion increased urinary chloride excretion without affecting sodium excretion, and calcium gluconate failed to increase either sodium or chloride excretion. Also, the filtered loads of sodium and chloride were unchanged during the calcium infusions. These results give no indication that calcium inhibited renin secretion by increasing the sodium or chloride load at the macula densa. The effects of intrarenal calcium infusion on renin release were also assessed in dogs with a nonfiltering kidney in which renal tubular mechanisms could not influence renin secretion. The observation that calcium still suppressed renin release in these dogs provides additional evidence that the the major effect of calcium involved nontubular mechanisms. Thus, it appears likely that calcium acted directly on the juxtaglomerular cells to inhibit renin secretion.  (+info)

Structural and functional changes in acute liver injury. (5/62881)

Carbon tetrachloride produces liver cell injury in a variety of animal species. The first structurally recognizable changes occur in the endoplasmic reticulum, with alteration in ribosome-membrane interactions. Later there is an increase in intracellular fat, and the formation of tangled nets of the ergastoplasm. At no time are there changes in mitochondria or single membrane limited bodies in cells with intact plasmalemma, although a relative increase in cell sap may appear. In dead cells (those with plasmalemma discontinuties) crystalline deposits of calcium phosphatase may be noted. Functional changes are related to the endoplasmic reticulum and the plasma membrane. An early decrease in protein synthesis takes place; an accumulation of neutral lipid is related to this change. Later alterations in the ergastoplasmic functions (e.g., mixed function oxidation) occurs. Carbon tetrachloride is not the active agent; rather, a product of its metabolism, probably the CC1, free radical, is. The mechanisms of injury include macromolecular adduction and peroxide propagation. A third possibility includes a cascade effect with the production of secondary and tertiary products, also toxic in nature, with the ability to produce more widespread damage to intracellular structures.  (+info)

Nonbehavioral selection for pawns, mutants of Paramecium aurelia with decreased excitability. (6/62881)

The reversal response in Paramecium aurelia is mediated by calcium which carries the inward current during excitation. Electrophysiological studies indicate that strontium and barium can also carry the inward current. Exposure to high concentrations of barium rapidly paralyzes and later kills wild-type paramecia. Following mutagenesis with nitrosoguanidine, seven mutants which continued to swim in the ;high-barium' solution were selected. All of the mutants show decreased reversal behavior, with phenotypes ranging from extremely non-reversing (;extreme' pawns) to nearly wild-type reversal behavior (;partial' pawns). The mutations fall into three complementation groups, identical to the pwA, pwB, and pwC genes of Kunget al. (1975). All of the pwA and pwB mutants withstand longer exposure to barium, the pwB mutants surviving longer than the pwA mutants. Among mutants of each gene, survival is correlated with loss of reversal behavior. Double mutants (A-B, A-C, B-C), identified in the exautogamous progeny of crosses between ;partial' mutants, exhibited a more extreme non-reversing phenotype than either of their single-mutant (;partial' pawn) parents.---Inability to reverse could be expected from an alteration in the calcium-activated reversal mechanism or in excitation. A normal calcium-activated structure was demonstrated in all pawns by chlorpromazine treatment. In a separate report (Schein, Bennett and Katz 1976) the results of electrophysiological investigations directly demonstrate decreased excitability in all of the mutants, a decrease due to an altered calcium activation. The studies of the genetics, the survival in barium and the electro-physiology of the pawns demonstrate that the pwA and pwB genes have different effects on calcium activation.  (+info)

Dopamine stimulates salivary duct cells in the cockroach Periplaneta americana. (7/62881)

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)

PKCdelta acts as a growth and tumor suppressor in rat colonic epithelial cells. (8/62881)

We have analysed the expression of three calcium-independent isoforms of protein kinase C (PKC), PKCdelta, PKCepsilon and PKCzeta, in an in vitro model of colon carcinogenesis consisting of the nontumorigenic rat colonic epithelial cell line D/WT, and a derivative src-transformed line D/src. While PKCzeta and PKCepsilon showed similar protein levels, PKCdelta was markedly decreased in D/src cells when compared to the D/WT line. To assess whether down-regulation of PKCdelta was causally involved in the neoplastic phenotype in D/src cells, we prepared a kinase-defective mutant of PKCdelta. Stable transfection of this sequence caused morphological and growth changes characteristic of partial transformation in D/WT cells. Moreover, to test whether PKCdelta was involved in growth control and transformation in this model, we overexpressed PKCdelta in D/src cells. Transfected cells underwent marked growth and morphological modifications toward the D/WT phenotype. In a late stage in culture, transfected cells ceased to proliferate, rounded up and degenerated into multinucleated, giant-like cells. We conclude that PKCdelta can reverse the transformed phenotype and act as a suppressor of cell growth in D/src cells. Moreover, our data show that downregulation of this isoenzyme of PKC may cooperate in the neoplastic transformation induced by the src oncogene in D/WT cells.  (+info)

  • The blood levels of phosphate are closely linked to calcium levels and they work in opposite ways: As blood calcium levels get high, phosphate levels get low, and the opposite is also true. (
  • Decreased kidney function (common in older adults) and certain popular prescription drugs lower the body's ability to get rid of excess calcium and raise the risk of toxic excess. (
  • Most people who have low or high levels of calcium do not have any symptoms. (
  • A test for calcium in urine is a 24-hour test that checks the amount of calcium that is passed from the body in the urine. (
  • They also control the amount of calcium you absorb from food and the amount passed from the body in urine. (
  • It is important to get the right amount of calcium in your food because the body loses calcium every day. (
  • Test results may be affected by the amount of calcium in the diet. (
  • Usually triggered in recent times by consuming too much supplemental calcium, patients have excess calcium in their blood, overly alkaline body chemistry, and kidney problems. (
  • The body stores more than 99 percent of its calcium in the bones and teeth to help make and keep them strong. (
  • At any given time, about 99% of our total body calcium stores are found in bones and teeth. (
  • Calcium is needed for healthy bones and teeth, and to make your heart work properly. (
  • 99% of calcium is deposited in bones and teeth, constantly being withdrawn and re-deposited at controlled rates. (
  • Approximately ninety nine percent of the body's calcium reserve is stored in our bones and teeth to support their structure and function. (
  • Most of us know that our bones and teeth are made primarily of calcium. (
  • Ninety-nine percent of it is stored within our bones and teeth, with 1% circulating as serum calcium in the blood. (
  • The metabolism of calcium in the body is very tightly regulated, and the body uses the bones and teeth as both the source and the reserve of calcium to maintain serum calcium levels. (
  • Calcium is important in the maintenance of healthy bones and teeth, as many of us know, but it is also involved in ensuring proper muscle function, nerve transmission, cellular signaling, vascular contraction and dilation, and hormone secretion. (
  • Phosphorus is needed alongside calcium in the maintenance of healthy bones and teeth. (
  • While calcium is the most critical nutrient to skeletal health, other nutrients provide important support to help absorb and use calcium in the bones. (
  • A healthy balanced diet will provide all the nutrients, including calcium, that they need. (
  • Recent Examples on the Web Kale, spinach, and Swiss chard contain essential prenatal nutrients like calcium , iron, and folate (which also helps protect against birth defects), not to mention tons of vital daily dietary fiber, says Williams. (
  • Which foods contain calcium and how much is in an average portion? (
  • Calcium-fortified foods. (
  • Some foods are very high in calcium. (
  • Because calcium is so important, food companies often add it to cereal, bread, juice, and other kid-friendly foods. (
  • But preteens and teens may need to add more calcium-rich foods to their diet. (
  • It is important to get plenty of calcium in the foods you eat. (
  • From this very simple description, you can see how calcium-rich foods can play a role in many aspects of your health that extend far beyond the specific area of bone health. (
  • There is still some debate about how much of a problem this is for the average adult, but at this time, most nutrition experts agree that excess dietary calcium is very unlikely, and probably the result of a diet that is largely dependent upon dairy foods. (
  • Contrary to popular belief, you do not need to eat dairy foods to get the calcium you need in your meal plan. (
  • However, if you want to avoid dairy foods altogether, it is definitely possible for you to do so while obtaining all of the calcium you need from other foods. (
  • Of course, most likely you won't be sitting down to a dish of parsley, as you would collards or kale, but just knowing how loaded with calcium it is, maybe you'll be adding it to more foods. (
  • Use the Nutrition Facts label to find foods with at least 20% DV (Daily Value) of calcium. (
  • Also include foods with less than 20% DV of calcium to help you meet your daily goal. (
  • The calcium calculator provides a list of calcium-rich foods and links to bone-healthy recipes. (
  • It also helps you see which foods are more calcium rich per serving compared to others. (
  • Plenty of foods are rich in calcium, and many do not contain dairy. (
  • The following foods are rich in calcium and contain no animal-based products. (
  • If these findings are correct then it calls into question the push to increase the consumption of dairy foods in childhood and the assumption that calcium is the important factor in creating a bigger personal bone bank for the future. (
  • 1. Get calcium from greens, beans, or fortified foods. (
  • Beans are humble foods, and you might not know that they are loaded with calcium. (
  • Sodium (salt) in the foods you eat can greatly increase calcium loss through the kidneys. (
  • Here's a list of foods and beverages filled with calcium (no cows required), along with recipes to help make them an everyday occurrence in a variety of meals. (
  • As our bodies cannot make calcium, we must get it from the foods we eat and drink. (
  • Foods containing 20% or more of the DV is considered to provide a high level of calcium. (
  • Anhydrous calcium sulfate, Anhydrous gypsum, Anhydrous sulfate of lime, Calcium salt of sulfuric acid [Note: Gypsum is the dihydrate form and Plaster of Paris is the hemihydrate form. (
  • Said subterfuge regards the amount of actual, usable calcium, called 'Elemental Calcium' (E.Cal. (
  • 1000mg**, you might logically assume that you are getting 1000mg of usable, Elemental Calcium - but you would be wrong! (
  • In the experimental group, the women received 1gram (0.03oz) of elemental calcium daily. (
  • There is no such thing as a nugget of pure, elemental calcium. (
  • Low Blood Calcium And Sudden Cardiac Arrest Posted by Denis OMalley on 9 Oct 2017 at 8:56 pm This is another article worth dismissing as irrelevant, curiously following one, last week, on low Potassium, just as worthless. (
  • Usually, low or high blood calcium is the result of some other underlying medical problem, and either one can cause heart rhythm failures, for one thing. (
  • Maintaining a balanced blood calcium level is essential to life, especially for cardiac function. (
  • A normal blood calcium level is about 10 mg. percent-that is, about 10 mg. per 100 milliliters (ml.) of blood. (
  • In the blood, calcium is either free or bound to the protein albumin. (
  • When blood calcium levels are low, the parathyroid glands are stimulated to produce and release parathyroid hormone. (
  • The test may also be useful if the patient has signs of too much blood calcium (hypercalcemia) or low blood calcium (hypocalcemia). (
  • Hypercalcemia- High levels of blood calcium. (
  • Hypocalcemia- Low levels of blood calcium. (
  • Basic blood tests, such as blood calcium levels, do not carry any significant risks, other than slight bruising and the chance of brief dizziness. (
  • When we eat the soft bones of fish, as with sardines, pilchards and tinned salmon, they supply us with valuable calcium. (
  • Adolescents as well as seniors, whose ability to absorb calcium declines with age, have higher calcium requirements. (
  • Thus, infants, children, adolescents and pregnant and lactating women should consume a diet rich in calcium. (
  • To be sure, if your diet is deficient in calcium it will aggravate the situation. (
  • If you don't consume dairy for health reasons (e.g., lactose intolerance) or other personal reasons (e.g., dietary restrictions due to religious beliefs), it is still possible to obtain necessary levels of calcium in your diet through non-dairy food sources. (
  • Too much calcium can sometimes be a result of taking too much in the diet. (
  • Calcium needs to be obtained from the diet as it is not manufactured by the body. (
  • Supplementing calcium in the diet when requirements are higher than normal, for example during childhood, pregnancy, breastfeeding or in old age. (
  • Experts say promoting a balanced diet including calcium would be a better strategy. (
  • We should return to seeing calcium as an important component of a balanced diet and not as a low cost panacea to the universal problem of postmenopausal bone loss. (
  • Although many people think of calcium in the diet as good protection for their bones, this is not at all the whole story. (
  • To protect your bones you do need calcium in your diet, but you also need to keep calcium in your bones. (
  • Their health clinics treated patients including women falling short on calcium in their diet -- by about 50 percent -- during pregnancy. (
  • You should be able to get all the calcium you need by eating a varied and balanced diet. (
  • The Government's National Diet and Nutrition Survey has identified calcium as generally lacking in the British diet, particularly among young children and women. (
  • These applications exploit the fact that calcium sulfate which has been powdered and calcined forms a moldable paste upon hydration and hardens as crystalline calcium sulfate dihydrate. (
  • As the disk cooled, the first solids condensed out like frost on a windowpane: crystalline clumps of aluminium and calcium as big as poppy seeds. (
  • Calcium sulfate (or calcium sulphate ) is the inorganic compound with the formula CaSO 4 and related hydrates . (
  • Calcium is essential for strong teeth and bones because it gives them strength and rigidity. (
  • Almost all (98 percent) of our approximately three pounds of calcium is contained in our bones, about 1 percent in our teeth, and the rest in the other tissues and the circulation. (
  • Ninety-nine percent of calcium is in teeth and bones. (
  • Calcium is an important component of the blood, that helps to form teeth and bones, but is also essential for helping to regulate muscle contraction and transmit impulses along our nerves. (
  • Almost all of this calcium is found in the skeleton and the rest is found in the teeth, the blood plasma, the body's soft tissues and the extracellular fluid. (
  • You need extra calcium while you're pregnant, because it helps build your babies' teeth and bones -- and keeps your own bones strong. (
  • Kids and teens 9 to 18 years old need 1,300 mg of calcium a day (4 servings). (
  • In fact, those pregnant and between the ages of 14 and 18 need 1,300 mg of calcium each day. (
  • Kale is a good producer of calcium, also. (
  • Find more information about kale and collards and about calcium and how your body uses it at . (
  • Any cause of multiple fractures and a relatively rare primary cancer of the bone marrow - multiple myeloma can also be the guilty party to a high calcium level. (
  • Calcium is often taken by older people to strengthen bones and prevent fractures. (
  • Calcium chromate loses water at 200 °C. It reacts with organic matter or reducing agents to form chromium(III). (
  • Retrieved on February 25, 2021 from (
  • Dictionary , Merriam-Webster, (