Vitamin growth requirements

The chemical environment of the cells has to be considered very carefully. Animal cells do not need only a carbon and nitrogen source. They are dependent on a variety of other compounds (amino acids, vitamins, growth factors etc.).This complexity of requirements of the culture medium and the complexity of the metabohsm hamper not only the development of defined media but... 

One of the organisms fulfills the need for a growth requirement by the other, for example, vitamin requirements of one organism that is provided by the other. Examples are provided by biotin in cocultures of Methylocystis sp. and Xanthobacter sp. (Lidstrom-O Connor et al. 1983), and thiamin in cocultures of Pseudomonas aeruginosa and an undefined Pseudomonas sp. that degraded the phosphonate herbicide glyphosate (Moore et al. 1983). 

Vitamins are required for satisfactory development or function of most yeasts. Wickerham (177) devised a complete yeast medium which included eight vitamins biotin, pantothenic acid, inositol, niacin, p-aminobenzoic acid, pyridoxine, thiamine, and riboflavin. The concentrations of these growth factors varied widely with inositol in the greatest concentration and biotin in trace amounts. Many of these vitamins are considered major growth factors for yeast multiplication and development, as noted in several studies and reviews (178, 179, 180, 181, 182). Generally, the benefit of adding vitamins to musts and wines has not been established as a normal winery practice. This lack of response is because vitamins occur naturally in sufficient quantities in grapes and are produced by yeasts themselves (3). 

Although vitamins are required in small amounts, they serve essential functions in maintaining normal growth and reproduction. Few vitamins can be synthesized by the bird in sufficient amounts to meet its needs. Some are found in adequate amounts in the feedstuffs commonly used in poultry diets, others must be supplemented. Although the total amount of a vitamin may appear to be adequate, some vitamins are present in bound or unavailable forms in feedstuffs. Supplementation is then essential. 

Yamada, et al. (34) have studied the vitamin Bg biosynthesis of a pdx B mutant, Escherichia coli B WG3, in amino acid - supplemented medium. An amino acid mixture and glycolaledhyde, which satisfy the vitamin Bg requirement of E. Coli B WG 3, a pdx B mutant, have been examined for their effect on growth of the mutant in liquid culture. 

Homocystinuria may result from one or several abnormalities in the mechanism whereby homocysteine is methylated to form methionine. About half of the patients respond to treatment with pyridoxine and it is thought that the vitamin overcomes a block at the homocysteine/cystathionine level by mass action (C23). However, Schuh et al. (S22) have recently described a patient who responded to vitamin B12. The infant presented with severe developmental delay, homocystinuria, and a megaloblastic anemia. Treatment with cyanocobalamin was without effect but treatment with hydroxocobalamin resulted in a rapid clinical improvement, and the homocystinuria disappeared. Methionine synthetase activity in cell extracts was normal, while cultured fibroblasts showed an absolute growth requirement for methionine. The defect appeared to be limited to methyleobalamin accumulation and an inability to transfer the methyl group from 5-methyltetrahydrofolate to homocysteine. 

There are a number of media available which are not based on a detailed investigation of growth requirements, but rather include crude mixtures of nutrients added to promote cell growth. These include lactalbumin hydrolysate (Appendix 1 Table 9) or yeast extract (Appendix 4) to provide an inexpensive source of amino acids or vitamins. Thus Melnick s monkey kidney media A and B (Melnick, 1955) contain lactalbumin hydrolysate and calf serum in Hanks and Earle s BSS, respectively. Chick embryo extract and tryptose phosphate broth (Appendix 1, Tables 11 and 12) are also used occasionally and their use is referred to where appropriate throughout the book. Mitsuhashi and Maramorosch mosquito cell medium contains lactalbumin hydrolysate, yeast extract and foetal calf serum in a specially developed saline (Mitsuhashi and Maramorosch, 1964 Singh, 1967). 

Dietary fat is also important as a source of the fat-soluble vitamins, A, D, E, and K. Requirements for the fat-soluble vitamins are several orders of magnitude lower than that of the essential fatty acids, being measured in micrograms rather than grams per day. Since the fat-soluble vitamins are required for growth and development, much interest has been focused on the concentration and availability of these vitamins in human milk. 

Coburn SP (1994) A critical review of minimal vitamin Be requirements for growth in various species with a proposed method of calculation. Vitamins and Hormones 48, 259-300. 

Estimation of the vitamin Be requirements of infants presents a problem, and there is a clear need for further research. Eiuman milk, which must be assumed to be adequate for infemt nutrition, provides only 2.5 to 3.5 /rg of vitamin Be per g of protein- lower them the requirement for adults. Although their requirement for catabolism of amino acids may be lower than in adults (because they have net new protein synthesis), they must also increase their body content of the viteimin as they grow. Coburn (1994) noted that tbe requirement for growth in a number of animal species was less tban tbat to maintain saturation of transaminases or minimum excretion of tryptophan metabolites after a test dose and was about 15 nmol per g of body weight gain across a range of species. 

Vitamins are required in the diet for growth, maintenance, and reproduction. These qualities are shared by other nutrients, such as the amino acids and the minerals. Why are amino acids and minerals not called vitamins The vitamins share a family of characteristics. They are organic compoimds required in the diet in only small amoxmts. They are not catabolized to satisfy part of the energy requirement and are not used for struchual purposes. Many vitamins are used as cofactors for enz5unes. Pyruvate dehydrogenase is one striking example. This enzyme uses five cofactors, where four of these cofactors are derived from vitamins. 

D-Amino acids vary in availability with the species. For example d-phenylalanine is used by rat, mouse, and man (15, 35, 727, 730, 962), whereas D-tryptophan is used by the rat (53, 54, 759, 895), is partially used by the mouse and pig (139, 867), and is not used by man (7, 29). The utilization of the D-amino acids is probably determined by the relative rates of absorption of the D-amino acid from the intestine, and of conversion of d- to L-amino acid in the liver (288). The conversion of d- to L-phenylalanine is reduced in vitamin-Be deficiency (52), as is to be expected for a transformation involving transamination to phenylpyruvic acid. Phenylpyruvic and indolepyruvic acids, the a-keto acids corresponding to phenylalanine and tryptophan, may also, to an extent varying with the species, satisfy growTh requirements (e.g., 55, 109, 436, 725, 911). 

C. Calculation of Vitamin B6 Requirement for Growth Refining Models of Vitamin B6 Kinetics... 

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