| antiberiberi vitamin | A member of the water-soluble B vitamin group, necessary for energy production and carbohydrate metabolism. Deficiency is known as beriberi. (27 Sep 1997) |
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| antihemorrhagic vitamin | <biochemistry> A fat soluble vitamin that plays an important role in blood clotting. (27 Sep 1997) |
| antineuritic vitamin | A member of the water-soluble B vitamin group, necessary for energy production and carbohydrate metabolism. Deficiency is known as beriberi. (27 Sep 1997) |
| antiscorbutic vitamin | <biochemistry> A requisite in the diet of man and guinea pigs. May act as a reducing agent in enzymic reactions, particularly those catalysed by hydroxylases. Synonym: Vitamin C. (18 Nov 1997) |
| antisterility vitamin | <biochemistry> Functions as an antioxidant, binds oxygen free radicals that can cause tissue damage, may also play a protective role in the coronary arteries from the damaging effects of cholesterol. (27 Sep 1997) |
| b-complex vitamin | <biochemistry> A group of vitamins that includes: B1(thiamin), B2 riboflavin), B3 (niacin), B6(pyridoxine), B12 (cobalamin) and folate. (24 Mar 1998) |
| vitamin | <biochemistry> An essential low molecular weight organic compound required in trace amounts for normal growth and metabolic processes. They usually serve as components of coenzyme systems. For humans Vitamin A, the B series, C, D1 and D2, E and K are required. Deficiencies of one or more vitamins in the nutrient supply result in deficiency diseases. (11 Nov 1997) |
| vitamin A | <biochemistry> Deficiency of this vitamin interferes with the production of rhodopsin in the eye resulting in night blindness and xerophthalmia. (27 Sep 1997) |
| vitamin A1 | Vitamin A1alcohol; 2,6,6-trimethyl-1-(9'-hydroxy-3',7'-dimethylnona-1',3',5',7'-tetraenyl)cyclohex-1-ene;a half-carotene bearing the b (or beta-ionone) form of the cyclic end group and a CH2OH at the C-15 position (numbering as in carotenoids) or 9'-position (numbering as a nonyl side chain on a cyclohexene ring); an intermediate in the vision cycle, it also plays a role in growth and differentiation. See: dehydroretinol. Synonym: vitamin A1 alcohol, vitamin A1. Retinol dehydrogenase, an oxidoreductase catalyzing interconversion of retinal and NADH to retinol and NAD+. (05 Mar 2000) |
| vitamin A1 acid | <biochemistry> The aldehyde (retinal) has long been known to be involved in photoreception, but retinoic acid has other roles. There are cytoplasmic retinoic acid binding proteins and retinoic acid response elements that regulate gene transcription. Retinoic acid is thought to be a morphogen in chick limb bud development and in early development of the chick that probably accounts for its potent teratogenic action. Synonym: vitamin A. (03 Jul 1999) |
| vitamin A1 alcohol | Vitamin A1alcohol; 2,6,6-trimethyl-1-(9'-hydroxy-3',7'-dimethylnona-1',3',5',7'-tetraenyl)cyclohex-1-ene;a half-carotene bearing the b (or beta-ionone) form of the cyclic end group and a CH2OH at the C-15 position (numbering as in carotenoids) or 9'-position (numbering as a nonyl side chain on a cyclohexene ring); an intermediate in the vision cycle, it also plays a role in growth and differentiation. See: dehydroretinol. Synonym: vitamin A1 alcohol, vitamin A1. Retinol dehydrogenase, an oxidoreductase catalyzing interconversion of retinal and NADH to retinol and NAD+. (05 Mar 2000) |
| vitamin A2 | 3-Dehydroretinol;retinol with an additional double bond in the 3-4 position of the cyclohexane ring. Synonym: vitamin A2. (05 Mar 2000) |
| vitamin A2 aldehyde | 3-Dehydroretinaldehyde;dehydroretinol with -CHO instead of -CH2OH at the terminal carbon of the side chain. Synonym: retinene-2, vitamin A2 aldehyde. (05 Mar 2000) |
| vitamin A aldehyde | <chemical> A carotenoid constituent of visual pigments. It is the oxidised form of retinol which functions as the active component of the visual cycle. It is bound to the protein opsin forming the complex rhodopsin. When stimulated by visible light, the retinal component of the rhodopsin complex undergoes isomerization at the 11-position of the double bond to the cis-form; this is reversed in "dark" reactions to return to the native trans-configuration. Chemical name: Retinal (03 Jul 1999) |
| vitamin a deficiency | A nutritional condition produced by a deficiency of vitamin a in the diet, characterised by night blindness and other ocular manifestations such as dryness of the conjunctiva and later of the cornea (xerophthalmia). Vitamin a deficiency is a very common problem worldwide, particularly in developing countries as a consequence of famine or shortages of vitamin a-rich foods. In the united states it is found among the urban poor, the elderly, alcoholics, and patients with malabsorption. (12 Dec 1998) |