Vitamins, continued vitamin

In a recent study, serum ascorbate concentrations were significantly reduced in a group of elderly diabetic patients (w = 40, mean age 69 years) in comparison with an age-matched group of non-diabetic controls ( = 22, mean age 71 years), and this reduction was more pronounced in those patients with microangiopathy (Sinclair et al., 1991). Diabetic patients were shown to have a high serum dehydroascorbate/ascorbate ratio indicative of increased oxidative stress. Ascorbate deficiency was partially corrected by vitamin C supplementation, 1 g daily by mouth, but the obvious disturbance in ascorbate metabolism in the diabetic patients was accentuated, since serum ascorbate concentrations fell (after the initial rise) despite continued vitamin C supplementation (Fig. 12.3). 

Table 1.1 [continued] Vitamin Functions Deficiency Disease... 

The isotope dilution technique has been employed for Ihe determination of about thirty elements in a variety of matrix materials, Isotopic dilution procedures have also been most widely used for the determination of compounds of interest in organic chemistry and biochemistry, Thus, methods have been developed for the determination of such diverse substances as vitamin D, vitamin B12, sucrose, insulin, penicillin, various amino acids, corticosterone, various alcohols, and thyroxine. Isotope dilution analysis has experienced less widespread application since the advent of activation methods. Continued use of the procedure can be expected, however, because of the relative simplicity of the equipment required. In addition, isotope dilution is often applicable where activation analysis is not. 

A. Role of Vitamin B, Vitamin Bi (cobalamin), a cobalt-containing molecule, is (along with folic acid) a cofactor in the transfer of one-carbon units, a step necessary for the synthesis of DNA. Impairment of DNA synthesis affects all cells, but because red blood cells must be produced continuously, deficiency of either Bj, or folic acid usually manifests first as anemia. In addition, an important manifestation of vitarnin B, deficiency is the development of neurologic defects, which may become irreversible if not treated promptly. 

It is not possible to assure industrial workers or anyone else that they can maintain optimal nutritional health just by swallowing vitamin or vitamin-mineral pills daily, and continuing to eat poorly balanced meals. 

Continue vitamin B for at least 2 weeks longer if malnourished or ongoing drinking. 

Although a tremendous number of fermentation processes have been researched and developed to various extents, only a couple of hundred ate used commercially. Fermentation industries have continued to expand in terms of the number of new products on the market, the total volume (capacity), and the total sales value of the products. The early 1990s U.S. market for fermentation products was estimated to be in the 9-10 x 10 range. The total world market is probably three times that figure, and antibiotics continue to comprise a primary share of the industry. Other principal product categories are enzymes, several organic acids, baker s yeast, ethanol (qv), vitamins (qv), and steroid hormones (qv). 

There are numerous reports of the effects of antioxidant vitamins on transformation. Vitamin C suppresses x-ray-induced transformation when CSHlOTy cells are treated daily for one week following irradiation (97), suppresses transformation by y-rays or neutrons, and prevents the promotion of radiation-induced transformation by 12-0-tetradecanoylphorbol 13-acetate (TPA), but has no effect on cell survival (98). In these studies, the continuous presence of vitamin C for a critical period appears to be necessary for suppression of transformation. Vitamin C may act on the promotion stage of... 

More than one process is available for some of the vitamins. Further, manufacturers have developed variants of the classical syntheses during Optimization. Whereas some of this information is available, as described in the individual sections on vitamins, much is closely held as trade secrets. Judging from the more recent patent Hterature, the assessment can be made that vitamin production technologies are in general mature. However, the economic value of these products drives continuing research aimed at breakthrough processes. Annual production of vitamins varies gready, from ca 10 metric tons of vitamin B 2 to ca 50,000 metric tons of vitamin C. 

It is generally assumed that adequate vitamin levels in humans can be obtained through a balanced diet. However, ongoing studies continue to indicate that the majority of the U.S. population is not receiving even the RDA through diet. Supplementary vitamins are thus provided for fortification of foods (20) and as oral or parenteral dosage forms. 

Reichsteia and Grbssner s second L-ascorbic acid synthesis became the basis for the iadustrial vitamin C production. Many chemical and technical modifications have improved the efficiency of each step, enabling this multistep synthesis to remain the principal, most economical process up to the present (ca 1997) (46). L-Ascorbic acid is produced ia large, iategrated, automated faciUties, involving both continuous and batch operations. The process steps are outlined ia Figure 7. Procedures require ca 1.7-kg L-sorbose/kg of L-ascorbic acid with ca 66% overall yield ia 1977 (55). Siace 1977, further continuous improvement of each vitamin C production step has taken place. Today s overall ascorbic acid yield from L-sorbose is ca 75%. In the mid-1930s, the overall yield from L-sorbose was ca 30%. 

Market Forms. Vitamin B 2 is sold almost exclusively as cyanocobalamin. Approximately one-third of the material is for the human pharmaceutical market whereas two-thirds is used in the animal feed market, primarily for poultry and swine (see Feeds AND FEED ADDITIVES). Modest growth in both markets has occurred in the period 1980—1995 and this trend is expected to continue. 

More than 20 other, naturally occurring metaboUtes of vitamin D have been isolated and characterized, and many derivatives have been synthesized. Their function is the subject of continuing research (16,51,141,162). 

PTH has a dual effect on bone cells, depending on the temporal mode of administration given intermittently, PTH stimulates osteoblast activity and leads to substantial increases in bone density. In contrast, when given (or secreted) continuously, PTH stimulates osteoclast-mediated bone resorption and suppresses osteoblast activity. Further to its direct effects on bone cells, PTH also enhances renal calcium re-absorption and phosphate clearance, as well as renal synthesis of 1,25-dihydroxy vitamin D. Both PTH and 1,25-dihydroxyvitamin D act synergistically on bone to increase serum calcium levels and are closely involved in the regulation of the calcium/phosphate balance. The anabolic effects of PTH on osteoblasts are probably both direct and indirect via growth factors such as IGF-1 and TGF 3. The multiple signal transduction... 

Vitamin D is not strictly a vitamin since it can be synthesized in the skin, and under most conditions that is its major source. Only when sunlight is inadequate is a dietary source required. The main function of vitamin D is in the regulation of calcium absorption and homeostasis most of its actions are mediated by way of nuclear receptors that regulate gene expression. Deficiency—leading to rickets in children and osteomalacia in adults—continues to be a problem in northern latitudes, where sunlight exposure is poor. 

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