vitamin K (redirected from vitamin K K3)

vitamin /vi·ta·min/ (vi´tah-min) any of a group of unrelated organic substances occurring in many foods in small amounts and necessary in trace amounts for the normal metabolic functioning of the body; they may be water- or fat-soluble.

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vitamin A  retinol or any of several fat-soluble compounds with similar biological activity; the vitamin acts in numerous capacities, particularly in the functioning of the retina, the growth and differentiation of epithelial tissue, the growth of bone, reproduction, and the immune response. Deficiency causes skin disorders, increased susceptibility to infection, nyctalopia, xerophthalmia and other eye disorders, anorexia, and sterility. As vitamin A it is mostly found in liver, egg yolks, and the fat component of dairy products; its other major dietary source is the provitamin A carotenoids of plants. It is toxic when taken in excess; see hypervitaminosis A.

vitamin A1  retinol.

vitamin A2  dehydroretinol.

vitamin B1  thiamine.

vitamin B2  riboflavin.

vitamin B6  any of a group of water-soluble substances (including pyridoxine, pyridoxal, and pyridoxamine) found in most foods, especially meats, liver, vegetables, whole grains, cereals, and egg yolk, and concerned in the metabolism of amino acids, in the degradation of tryptophan, and in the metabolism of glycogen.

vitamin B12  cyanocobalamin by chemical definition, but generally any substituted cobalamin derivative with similar biological activity; it is a water-soluble hematopoietic vitamin occurring in meats and animal products. It is necessary for the growth and replication of all body cells and the functioning of the nervous system, and deficiency causes pernicious anemia and other forms of megaloblastic anemia, and neurologic lesions.

vitamin B complex  a group of water-soluble substances including thiamine, riboflavin, niacin (nicotinic acid), niacinamide (nicotinamide), the vitamin B6 group, biotin, pantothenic acid, and folic acid, and sometimes including p- aminobenzoic acid, inositol, vitamin B12, and choline.

vitamin C  ascorbic acid.

vitamin D  either of two fat-soluble compounds with antirachitic activity or both collectively: cholecalciferol, which is synthesized in the skin and is considered a hormone, and ergocalciferol, which is the form generally used as a dietary supplement. Dietary sources include some fish liver oils, egg yolks, and fortified dairy products. Deficiency can result in rickets in children and osteomalacia in adults, while excessive ingestion can cause hypercalcemia, mobilization of calcium from bone, and renal dysfunction.

vitamin D2  ergocalciferol.

vitamin D3  cholecalciferol.

vitamin E  any of a group of at least eight related fat-soluble compounds with similar biological antioxidant activity, particularly α-tocopherol but also including other isomers of tocopherol and the related compound tocotrienol. It is found in wheat germ oil, cereal germs, liver, egg yolk, green plants, milk fat, and vegetable oils and is also prepared synthetically. In various species it is important for normal reproduction, muscle development, and resistance of erythrocytes to hemolysis.

fat-soluble vitamins  those (vitamins A, D, E, and K) that are soluble in fat solvents and are absorbed along with dietary fats; they are not normally excreted in the urine and tend to be stored in the body in moderate amounts.

vitamin K  any of a group of structurally similar fat-soluble compounds that promote blood clotting. Two forms, phytonadione and menaquinone, exist naturally, and there is one synthetic provitamin form, menadione. The best sources are leafy green vegetables, butter, cheese, and egg yolk. Deficiency, usually seen only in neonates, in disorders of absorption, or during antibiotic therapy, is characterized by hemorrhage.

vitamin K1  phytonadione.

vitamin K2  menaquinone.

vitamin K3  menadione.

water-soluble vitamins  the vitamins soluble in water (i.e., all but vitamins A, D, E, and K); they are excreted in the urine and are not stored in the body in appreciable quantities.

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vitamin K

n.

Any of several fat-soluble compounds that are found in alfalfa, hog liver, fish meal, and vegetable oils and are essential for the production of normal amounts of prothrombin. Also called antihemorrhagic factor.

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vitamin K,

a group of fat-soluble vitamins known as quinones that are essential for the synthesis of prothrombin in the liver and of several related proteins involved in the clotting of blood. The vitamin is widely distributed in foods, especially leafy green vegetables, pork liver, yogurt, egg yolk, kelp, alfalfa, fish-liver oils, and blackstrap molasses, and is synthesized by the bacterial flora of the GI tract. It is also produced synthetically. Deficiency results in hypoprothrombinemia, characterized by poor coagulation of the blood and hemorrhage, and usually occurs from inadequate absorption of the vitamin from the GI tract or the inability to use it in the liver. It is used to reduce the clotting time in patients with obstructive jaundice and in hemorrhagic states associated with intestinal diseases and diseases of the liver; it is given prophylactically to infants to prevent hemorrhagic disease of the newborn. Natural vitamin K is stored in the body and produces no toxicity. Excessive doses of synthetic vitamin K may cause anemia in newborns and hemolysis in people with glucose-6-phosphate deficiency. See also vitamin K₁, vitamin K₂, menadione.

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vitamin K,

n a fat-soluble vitamin found in leafy greens, beans, peas, oats, and whole wheat. Has been used to remedy deficiencies (including those associated with alcoholism, Crohn's disease, diarrhea, and ulcerative colitis), osteoporosis, and menorrhagia. Pregnant women taking anticonvulsants may need to supplement vitamin K to prevent birth defects. Contraindicated for patients taking warfarin and caution with cephalosporins. Also called
menadione, menaquinone, or
phylloquinone.

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vitamin (vi´tmin),

n one of a number of unrelated organic substances that occur in small amounts in food and are required for normal metabolic activity. The vitamins may be water soluble or fat soluble.

vitamin A,

n (retinal, retinol, retinoic acid), a fat-soluble substance, occurring in several chemical forms in food and function: retinal, an aldehyde; retinol, an alcohol; and retinoic acid, an acid. All three function in calcified and epithelial tissue growth. The aldehyde-alcohol (retinal-retinol) interconversion allows regeneration of rhodopsin (visual purple) in the rod cells of the retina. A deficiency results in hyperkeratinization of nonsecretory protective epithelium, deranged secretory function of the mucous membrane, dark dysadaptation (night blindness), and possibly, enamel hypoplasia. Dietary sources include liver, kidney, and lung as well as carotenes (provitamins A) from the plant kingdom.

vitamin, ascorbic acid

n (vitamin C, antiscorbutic factor), a water-soluble vitamin resembling glucose in structure; it is found in citrus fruits, tomatoes, cabbage, and other fresh fruits and vegetables. Necessary for hydroxylation of peptide-bound lysine and proline to hydroxylysine and hydroxyproline during collagen synthesis. A deficiency leads to scurvy, in which pathologic signs are confined mainly to the connective tissues with hemorrhages, loosening of teeth, gingivitis, and poor wound healing.

vitamin B,

n See vitamin, thiamine.

vitamin B,

n See vitamin, riboflavin.

vitamin B,

n See vitamin, pyridoxine.

vitamin B,

n See vitamin, cobalamin.

vitamin B complex,

n collectively, the various B vitamins: thiamine, riboflavin, nicotinic acid, pyridoxine, biotin, paraaminobenzoic acid, folic acid, pantothenic acid, cyanocobalamin, pteroylglutamic acid, and others that are unknown.

vitamin, biotin

n (vitamin H, anti-egg-white factor), one of the B complex vitamins found in organ meats (e.g., liver, heart, kidney), egg yolk, cauliflower, chocolate, and mushrooms. Its synthesis by intestinal bacteria makes human deficiency states rare, unless the diet contains significant raw egg white protein (avidin), which complexes the vitamin to prevent intestinal absorption. Dermatitis, retarded growth, and loss of hair and muscular control occur in experimental animals with deficiency. Biotin functions as a coenzyme for carboxylase enzymes that catalyze fixation of carbon dioxide (e.g., in fatty acid synthesis).

vitamin C,

n See vitamin, ascorbic acid.

vitamin, calciferol,

n See vitamin D.

vitamin, cholecalciferol,

n See vitamin D.

vitamin, choline

n not truly a vitamin, because it can be synthesized in the body if sufficient precursors are available. Prevents the accumulation of fat in the liver of certain animal species. Occurs as a constituent of lecithin, sphingomyelin, and acetylcholine.

vitamin, cobalamin

n (antipernicious factor, vitamin B₁₂, cyanocobalamin, erythrocyte maturing factor [EMF], extrinsic factor) a vitamin that contains cobalt and is essential for the maturation of erythrocytes. Inability of the body to produce intrinsic factor, which is necessary for vitamin B₁₂ absorption, results in pernicious anemia. Liver, kidney, muscle, and milk are good sources.

vitamin D (antirachitic factor, calciferol, cholecalciferol, ergosterol, ergocalciferol),

n the group of lipid-soluble sterol compounds capable of preventing rickets. Of primary importance are D₂, or ergosterol, from plants and D₃, or cholecalciferol, from animal sources, especially fish liver oils. The latter is also formed in the skin from 7-dehydrocholesterol on exposure to ultraviolet light. Liver mitochondria further activate vitamin D to 25-(OH)-D, which in turn is metabolized to 1,25-(OH)₂-D by the kidney. The dihydroxy metabolites significantly increase dietary calcium absorption and bone resorption to maintain proper blood calcium and phosphorus levels. A primary vitamin D deficiency results from inadequate exposure to sunlight and low dietary intake. Secondary deficiencies occur from abnormalities of intestinal resorption and interference with vitamin D hydroxylation. The manifestations of rickets include enamel hypoplasia, poorly calcified bones, bowed legs, and a deformed rib cage with beadlike swellings of the ribs (rachitic rosary) in infants and children and osteomalacia in adults. Vitamin D intake in excess is toxic.

vitamin E,

n (tocopherol, tocotrienol antisterility factor) the tocopherol and tocotrienols have varying degrees of vitamin E activity, but α-tocopherol is the most active. These fat-soluble compounds are found in eggs, muscle meats, liver, fish, chicken, oatmeal, and the oils of corn, soya, and cottonseed. In rats, the lack of vitamin E leads to fetus resorption in the female and atrophy of spermatogenic tissue with permanent sterility in the male. Vitamin E deficiency in humans is correlated with increased hemolysis of erythrocytes. The tocopherols prevent peroxidation of unsaturated fatty acids, and vitamin E requirements appear to be directly related to the dietary intake of unsaturated fatty acids. Although animals develop symptoms of muscular dystrophy on deficient diets, the vitamin has no effect on the human disease.

vitamin, ergocalciferol,

n See vitamin D.

vitamin, folacin,

n (adermine, folic acid, citrovorum factor, pteroylglutamic acid, vitamin M, vitamin B_c) occurs in many tissues as the free acid or is conjugated with one to seven glutamic acid molecules. Green, leafy vegetables; kidney; liver; and yeast are good sources, and bacterial synthesis in humans occurs readily. As a coenzyme, the vitamin serves as a carrier of one-carbon units (formyl, hydroxymethyl, formimino groups), especially in the synthesis of nucleoproteins. Inadequate folate levels produce a variety of species-dependent symptoms that include megaloblastic anemia in humans.

vitamin G,

n See vitamin, riboflavin.

vitamin H,

n See vitamin, biotin.

vitamin, inositol

n (
myo-inositol,
meso-inositol), a six-carbon alcohol closely related to the hexoses. Inositol is not truly a vitamin because the body can synthesize significant amounts from glucose. Its biologic role is not established, but it is essential to the growth of liver and bone marrow cells and helps alleviate fatty livers.

vitamin K,

n (phytonadione, antihemorrhagic factor), one of the many fat-soluble naphthoquinone compounds with vitamin D activity. Vitamin K₁ is found primarily in leafy vegetables, K₂ is synthesized by human intestinal bacteria, and K₃ (menadione, N.F.) is a synthetic compound. Vitamin K is essential for the synthesis of prothrombin by the liver. A dietary deficiency of vitamin K is rare, however. The vitamin has been used in conjunction with extensive oral antibiotic therapy to treat hemorrhagic disease of the newborn, hemorrhage of obstructive jaundice, and sprue, and during anticoagulant therapy. Prothrombin, Stuart factor, Christmas factor, and serum prothrombin conversion accelerator require vitamin K for their synthesis.

vitamin, niacin

n (nicotinic acid, nicotinamide, niacinamide, pellagra-preventive factor), a deficiency of niacin or its amide derivative, niacinamide, results in acute pellagra that is characterized by dermatitis, diarrhea, dementia, stomatitis, and glossitis. Dietary sources include liver, kidney, lean meats, wheat germ, yeast, soybeans, and peanuts. There is some intestinal synthesis by bacteria. Although the amino acid tryptophan contributes to the body supply of niacin, sufficient vitamin B₆ must be present for its metabolism. Niacin and niacinamide are interconvertible in the body, and the latter functions as a constituent of two coenzymes, NAD and NADP, which operate as hydrogen and electron transfer agents by virtue of their reversible oxidation and reduction in several enzyme systems.

vitamin, pantothenic acid

n (pantothen, panthenol), this vitamin is a component of coenzyme A and thereby functions in the metabolism of lipids, carbohydrates, and proteins. A deficiency is unusual because of its wide distribution, but a “burning feet syndrome” has been reported in people suffering from acute malnutrition.

vitamin, pyridoxine

n (vitamin B₆, pyridoxal, pyridoxol, pyridoxamine) part of the B complex vitamins, the group includes three chemically related substances: pyridoxol, pyridoxal, and pyridoxamine, all of which serve as substrate in the formation of pyridoxal phosphate, the prosthetic group for several enzymes that decarboxylate, deaminate, transaminate, or desulfurate specific amino acids. It further functions in porphyrin, fatty acids, and cholesterol metabolism. Deficiency signs include an acrodynia-like syndrome, convulsive seizures, arteriosclerotic-like lesions, hypochromic microcytic anemia, and impaired antibody formation. Dietary sources include wheat; corn; liver; milk; eggs; and green, leafy vegetables.

vitamin, retinal,

n See vitamin A.

vitamin, retinoic acid,

n See vitamin A.

vitamin, retinol,

n See vitamin A.

vitamin, riboflavin

n (vitamin B₂, vitamin G, lactoflavin) a heat-stable B complex vitamin that functions as a component of FAD and FMN for the reversible transfer of hydrogen and electrons in several enzyme systems. It is found in green, leafy vegetables; whole grains; eggs; liver; milk; and legumes; small amounts are synthesized in the intestinal tract by microorganisms. Signs of ariboflavinosis include angular stomatitis, seborrheic dermatitis of the face, and glossitis (magenta tongue).

vitamin, thiamine

n (vitamin B₁, aneurine, antiberiberi factor, antineuritic factor) a B complex vitamin found primarily in plants, especially legumes; whole grains; and green, leafy vegetables; it is also synthesized by bacteria in the large intestine, which is not a reliable source. Thiamine pyrophosphate (TPP, cocarboxylase) is a coenzyme in the oxidative decarboxylation of pyruvate and α-ketoglutarate, in the transketolase reaction of glucose metabolism and in the metabolism of branched chained amino acids. A deficiency results in beriberi.

vitamin, tocopherol,

n See vitamin E.

vitamin, tocotrienol,

n See vitamin E.

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vitamin K

a group of fat-soluble compounds which are required for the formation of prothrombin and therefore play a role in blood clotting. They are present in most green feeds and are not likely to be absent from natural diets. Failure to absorb the vitamin is a real risk in diseases in which fat absorption is defective, such as obstructive jaundice.

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vitamin K K deficiency

most commonly due to anticoagulant rodenticide poisoning in dogs, and less often cats.

vitamin K K₁

phylloquinone.

vitamin K K₂

menaquinone.

vitamin K K₃

menadione.