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.Carbonates: Salts or ions of the theoretical carbonic acid, containing the radical CO2(3-). Carbonates are readily decomposed by acids. The carbonates of the alkali metals are water-soluble; all others are insoluble. (From Grant & Hackh's Chemical Dictionary, 5th ed)Animal Shells: The hard rigid covering of animals including MOLLUSCS; TURTLES; INSECTS; and crustaceans.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.Lithium Carbonate: A lithium salt, classified as a mood-stabilizing agent. Lithium ion alters the metabolism of BIOGENIC MONOAMINES in the CENTRAL NERVOUS SYSTEM, and affects multiple neurotransmission systems.Antacids: Substances that counteract or neutralize acidity of the GASTROINTESTINAL TRACT.Calcification, Physiologic: Process by which organic tissue becomes hardened by the physiologic deposit of calcium salts.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)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.Pinctada: A genus of pearl oysters in the family Pteriidae, class BIVALVIA. Both cultured and natural pearls are obtained from species in the genus. They are distinct from the distantly related, edible true oysters of the family OSTREIDAE.Calcium Compounds: Inorganic compounds that contain calcium as an integral part of the molecule.Calcium Phosphates: Calcium salts of phosphoric acid. These compounds are frequently used as calcium supplements.Aluminum Hydroxide: A compound with many biomedical applications: as a gastric antacid, an antiperspirant, in dentifrices, as an emulsifier, as an adjuvant in bacterins and vaccines, in water purification, etc.Egg Shell: A hard or leathery calciferous exterior covering of an egg.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.Chemical Precipitation: The formation of a solid in a solution as a result of a chemical reaction or the aggregation of soluble substances into complexes large enough to fall out of solution.Phosphorus Metabolism Disorders: Disorders in the processing of phosphorus in the body: its absorption, transport, storage, and utilization.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.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)Calcium Chloride: A salt used to replenish calcium levels, as an acid-producing diuretic, and as an antidote for magnesium poisoning.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.Anthozoa: A class in the phylum CNIDARIA, comprised mostly of corals and anemones. All members occur only as polyps; the medusa stage is completely absent.Calculi: An abnormal concretion occurring mostly in the urinary and biliary tracts, usually composed of mineral salts. Also called stones.Lithostathine: The proteinaceous component of the pancreatic stone in patients with PANCREATITIS.Hyperphosphatemia: A condition of abnormally high level of PHOSPHATES in the blood, usually significantly above the normal range of 0.84-1.58 mmol per liter of serum.Lubrication: The application of LUBRICANTS to diminish FRICTION between two surfaces.Microradiography: Production of a radiographic image of a small or very thin object on fine-grained photographic film under conditions which permit subsequent microscopic examination or enlargement of the radiograph at linear magnifications of up to several hundred and with a resolution approaching the resolving power of the photographic emulsion (about 1000 lines per millimeter).Phosphates: Inorganic salts of phosphoric acid.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)Otolithic Membrane: A gelatinous membrane overlying the acoustic maculae of SACCULE AND UTRICLE. It contains minute crystalline particles (otoliths) of CALCIUM CARBONATE and protein on its outer surface. In response to head movement, the otoliths shift causing distortion of the vestibular hair cells which transduce nerve signals to the BRAIN for interpretation of equilibrium.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.Magnesium Hydroxide: An inorganic compound that occurs in nature as the mineral brucite. It acts as an antacid with cathartic effects.Crystallization: The formation of crystalline substances from solutions or melts. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Dihydrotachysterol: A VITAMIN D that can be regarded as a reduction product of vitamin D2.Absorption: The physical or physiological processes by which substances, tissue, cells, etc. take up or take in other substances or energy.Sodium Bicarbonate: A white, crystalline powder that is commonly used as a pH buffering agent, an electrolyte replenisher, systemic alkalizer and in topical cleansing solutions.PolyaminesMicroscopy, Electron, Scanning: Microscopy in which the object is examined directly by an electron beam scanning the specimen point-by-point. The image is constructed by detecting the products of specimen interactions that are projected above the plane of the sample, such as backscattered electrons. Although SCANNING TRANSMISSION ELECTRON MICROSCOPY also scans the specimen point by point with the electron beam, the image is constructed by detecting the electrons, or their interaction products that are transmitted through the sample plane, so that is a form of TRANSMISSION ELECTRON MICROSCOPY.Biological Availability: The extent to which the active ingredient of a drug dosage form becomes available at the site of drug action or in a biological medium believed to reflect accessibility to a site of action.Calcium: A basic element found in nearly all organized tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.Hypercalcemia: Abnormally high level of calcium in the blood.Polyethylenes: Synthetic thermoplastics that are tough, flexible, inert, and resistant to chemicals and electrical current. They are often used as biocompatible materials for prostheses and implants.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.Seawater: The salinated water of OCEANS AND SEAS that provides habitat for marine organisms.Construction Materials: Supplies used in building.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)Nacre: A biomineral consisting of layers of crystalized ARAGONITE, separated by interlamellar layers of organic matrix containing beta-CHITIN, and surrounded by an intercrystalline organic membrane of silk fibroin. Nacre is the iridescent substance better known as mother-of-pearl that is secreted by MOLLUSCS.Strongylocentrotus purpuratus: A species of SEA URCHINS in the family Strongylocentrotidae found on the Pacific coastline from Alaska to Mexico. This species serves as a major research model for molecular developmental biology and other fields.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.Chelating Agents: Chemicals that bind to and remove ions from solutions. Many chelating agents function through the formation of COORDINATION COMPLEXES with METALS.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.Pectinidae: A large family of mollusks in the class BIVALVIA, known commonly as scallops. They possess flat, almost circular shells and are found in all seas from shallow water to great depths.