Epithelial tissue vitamin

Vitamin A is necessary for the light reactions of vision, for normal growth and reproduction, and for differentiation and maintenance of epithelial tissues. Vitamin A is an antioxidant and has anticancer activity. 

The vitamin A needs of the body are by no means centered in any one organ or tissue. It is necessary for vision, for tooth and bone development, for maintenance of healthy epithelial tissue in the skin and in many organs, for reproduction, etc. It is to be expected that deficiency would be exhibited in many ways and that in different individuals the symptoms would not be the same. The benefits of vitamin A administration may thus appear very different in different individuals, and this helps to explain why many kinds of benefits (part of which are probably real) have been ascribed (by physicians as well as others) to vitamin A administration. A substance with such diverse functions is bound to show different effects in different individuals, and, of course, for some individuals who have low requirements and get plenty in their food, its administration will appear to be wholly without effect. Otto Bessey, in discussing the problem of nutrition, has used vitamin A as an illustration of how widely different levels are needed to maintain different functions in experi-... 

Vitamin A is essential for proper functioning of the retina, for the integrity of epithelial tissue, for growth and bone development and for reproduction. For vision the active vitamin appears to be retinal as the chromophore of both rods and cones is 11-cis-retinal which, in combination with the protein opsin, forms the photoreceptor rhodopsin. Retinoic acid is the active form associated with growth, differentiation, and transformation. Both all-trans and 9-cis retinoic acid act as a steroid hormone to affect cellular differentiation, especially for morphogenesis, reproduction and for immune responses. At... 

It is vital for the functioning of retina. Vitamin A is essential for differentiation and growth of epithelial tissue. It enhances function of immune system and protect against development of certain malignancies. Different forms of vitamin A mediate different functions. 

The retinoids, a family of molecules that are related to retinol (vitamin A), are essential for vision, reproduction, growth, and maintenance of epithelial tissues. Retinoic acid, derived from oxidation of dietary retinol, mediates most of the actions of the retinoids, except for vision, which depends on retinal, the aldehyde derivative of retinol. 

Maintenance of epithelial cells Vitamin A is essential for normal differentiation of epithelial tissues and mucus secretion. 

Vitamin A Retinol Retinal Retinoic acid p-Carotene Retinol Retinal Retinoic acid FAT-SOLUBLE Maintenance of reproduction Vision Promotion of growth Differentiation and maintenance of epithelial tissues Gene expression... 

Vitamin A (retinol, retinal, retinoic acid—the three active forms of vitamin A, and p-carotene) function in the maintenance of reproduction, vision, promotion of growth, differen tiation and maintenance of epithelial tissues, and gene expression. A deficiency of vitamin A results in impotence, night blindness, retardation of growth, and xerophthalmia. Large amounts of vitamin A are toxic and can result in an increased incidence of frac tures. 

Vitamin A is necessary for growth and reproduction, resistance to infection, maintenance and differentiation of epithelial tissues, stability and integrity of membrane structures, and the process of vision. In terms of the last function, vitamin A is a component of rhodopsin or visual purple, a photosensitive pigment in the eye that is needed for vision in dim light. An early mild clinical symptom of vitamin A deficiency is night blindness a severe deficiency of this fat-soluble vitamin results in xerophthalmia, an eye condition leading to blindness. 

Retinoic acid (vitamin A acid), in which the alcohol group has been oxidized, shares some but not all of the actions of retinol. Retinoic acid is ineffective in restoring visual or reproductive function in certain species in which retinol is effective. Flowever, retinoic acid is very potent in promoting growth and controlling differentiation and maintenance of epithelial tissue in vitamin A-deficient animals. Indeed, all-trans-retinoic acid (tretinoin) appears to be the active form of vitamin A in all tissues except the retina, and is 10- to 100-fold more potent than retinol in various systems in vitro. Isomerization of this compound in the body yields 13-n.v-rctinoic acid (isotretinoin), which is nearly as potent as tretinoin in many of its actions on epithelial tissues but may be as much as fivefold less potent in producing the toxic symptoms of hypervitaminosis A. 

Vitamin A has essential roles in vision, bone and muscle growth, reproduction and maintenance of healthy epithelial tissue. Naturally occurring precursors of vitamin A are found in some seeds, leafy green vegetables and forages such as lucerne. The common form of the precursor is p-carotene, which can be converted into vitamin A in the intestinal wall. Carotene is present in considerable quantities in pasture, lucerne hay or meal, and yellow maize. Carotene and vitamin A are rapidly destroyed by exposure to air, light and rancidity, especially at high temperature. Since it is difficult to assess the amount of vitamin A present in the feed, diets should be supplemented with this vitamin. 

Vitamin A A fat-soluble compound found in fish-liver oils, milk, green and yellow vegetables, and egg yolk. It is required for cell growth and development, epithelial tissue growth and protection, and normal vision. 

Vitamin A and its analogues, in particular retinoic acid, are involved in the proliferation and differentiation of epithelial tissues and have continued to be used in the treatment of dermatological disorders such as acne, psoriasis and hyperkeratosis [133, 134]. Currently, much effort is being focused on... 

The differentiation of epithelial tissue, growth, reproduction and the process of sight are dependent, in mammals and in humans, on an adequate provision of vitamin A. Ensuring this provision is therefore of great importance for nutrition and health in man. Via the vitaminization of animal feedstuff, which ensures healthy animal stocks, the vitamins additionally contribute to the provision of man with adequate and high quality foodstuffs. The vitamin demand arising therefrom could only be covered by synthetically produced products identical to the natural vitamin, a fact which gave a commercial stimulus to the development of industrial production processes. 

Retinoic acid is a metabolic product of vitamin A that supports the growth and differentiation of epithelial tissues. Retinoic acid is formed in the cytosol by the reversible oxidation of retinol to retinal, and the irreversible oxidation of retinal to retinoic acid. There is controversy as to whether retinal is oxidized by retinal dehydrogenase, which is linked to NAD+, or by retinal oxidase. 

Vitamin A is used for treatment of acne and other skin disorders. It helps to maintain epithelial tissue, eyes, hair, and bone growth. Excess vitamin A causes a toxic effect. Vitamin A is stored in the liver for up to 2 years and can result in inadvertent toxicity. Vitamin A-caused birth defects can occur if greater than 6000 international units (IU) are taken during the pregnancy. 

Which of the following statements regarding vitamin A is true Vitamin A promotes maintenance of epithelial tissue... 

Vitamin A (retinol) (Fig. 7.12) and its metabolic oxidation products assume a critical physiological role in growth, development and differentiation of epithelial tissue, the maintenance of vision, and as well in spermatogenesis and the normal development of the placenta and the foetus. (allE)-Retinoic acid and (13Z)-retinoic acid are important medicaments for the treatment of acne and psoriasis the former has also demonstrated complete remission in most cases of acute promyelocytic leukemia (APL). 

In its second role, in the regulation of cellular differentiation, vitamin A is involved in the formation and protection of epithelial tissues and mucous membranes. In this way it has particular importance in growth, reproduction and immune response. Vitamin A is important in the resistance to disease and promotion of healing through its effect on the immune system and epithelial integrity. In addition, it acts, along with vitamins E and C and 3-carotene, as a scavenger of free radicals (see Box 5.2, p. 83). 

Animals require an external source of vitamin A to maintain a variety of normal functions—growth, differentiation and integrity of epithelial tissue, bone... 

Functions. Vitamin A is essential for a number of physiological processes among them, (1) vision, (2) growth, (3) bone development, (4) tooth development, (5), maintenance of body epithelial tissues, (6) protective effect... 

Although adequate vitamin A is necessary to maintain healthy epithelial tissues, excessive intakes will not increase resistance to infections which enter through the epithelium. 

Protective effects against cancer—Vitamin A, either as retinol or carotene, appears to play an important nutritional role in keeping the body free of certain kinds of cancer, especially cancers of epithelial tissue (the skin and various membranes that line the mouth, internal passages, and hollow organs). This does not call for megadoses of vitamin A rather, it indicates that getting sufficient vitamin A in the daily diet is likely a very important anticancer measure. 

Rough, dry, scaly skin increased sinus trouble, sore throat, and abscesses in ears, mouth, or salivary gland increased diarrhea and kidney and bladder stones—A deficiency of vitamin A injures the epithelial tissues throughout the body, and leads to a peculiar type of horny degeneration called keratinization. The epithelial cells form the outer layer... 

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