Showing papers by "Ananda S. Prasad published in 1993"

Biochemistry of zinc

Abstract: Historical Aspects of Zinc. Zinc and Enzymes. Zinc and Gene Expression. Biochemistry of Metallothionein. Zinc and Hormones. Zinc and Lipid Metabolism. Zinc and Cells. Zinc and Neurobiology. Zinc and Immunity. Metabolism of Zinc. Clinical Spectrum of Human Zinc Deficiency. Interactions of Zinc with Other Micronutrients. Techniques for Measurement of Zinc in Biological Samples. Index.

Clinical Spectrum of Human Zinc Deficiency

Abstract: During the past two decades, a spectrum of clinical deficiency of zinc in human subjects has been recognized. At one end, the manifestations of zinc deficiency may be severe, and at the other end, zinc deficiency may be mild or marginal.

Zinc and Enzymes

Abstract: Zinc metalloenzymes catalyze approximately 50 important biochemical reactions Many of these enzymes have been isolated from more than one species, resulting in identification of over 200 catalytically active zinc metalloproteins (Galdes and Vallee, 1983)

Zinc and Gene Expression

Abstract: Recent studies show that zinc has a very important role in gene expression (Chesters, 1982; Falchuk, 1988; Vallee, 1983; Miller et al., 1985). A role of zinc in growth and development and the teratological abnormalities of zinc deficiency in fetal development have been known for many years. However, its role in cell differentiation and gene expression has been appreciated only recently.

Zinc and Cells

Abstract: Many studies have shown that zinc ions as an integral part of tissues and biologic fluids play an important role in homeostatic mechanisms regulating the reactivity of tissues and cells. In lymphocytes, zinc acts as a nonspecific mitogen (Chvapil, 1976). Within a range of 1.5 to 4.5 × 10−4 M Zn concentration in the culture medium, the blastogenic transformation of lymphocytes as well as their mitosis was significantly increased after 6 days in comparison with the effect of phytohemagglutinin (PHA). Zinc acted as a weak mitogen (Kirchner and Ruhl, 1970; Ruhl et al., 1974). Surprisingly, only zinc and mercury were stimulatory. Calcium and magnesium did not affect DNA synthesis in the culture system. Mn2+, Co2+, Cd2+, Cu2+, and Ni2+ at concentrations from 10−3 to 10−7 M were inhibitory. Inasmuch as DNA-synthesizing enzymes are zinc dependent, one may assume that enhanced mitosis of lymphocytes by zinc may be the result of increased activity of enzymes involved in cell mitosis.

Historical Aspects of Zinc

Abstract: Raulin (1869) was the first to show that zinc was essential for the growth of Aspergillus niger. This was confirmed forty years later by Bertrand and Javillier (1911). In 1926, its essentiality for higher forms of plant life was established (Sommer and Lipman, 1926) (see Figs. 1-1 and 1-2).

Interactions of Zinc with Other Micronutrients

Abstract: During the past two decades, it has become clear that the addition of a trace element to the animal diet alters the metabolism of other elements. In some instances the interaction between the added element and the responding element is complementary. For example, the dietary level of iron needed to maintain a given concentration of hemoglobin is dependent on the dietary copper level (Hill and Matrone, 1961). A majority of other interactions, however, are of antagonistic nature. For example, high levels of zinc added to diets are known to precipitate copper deficiency in animals and humans (Hill and Matrone, 1970; Prasad et al., 1978a). Several years ago, Hill and Matrone (1961) proposed that those elements whose electronic structure of the valence shell of the ions was the same, would act antagonistically to each other in biological systems (Hill, 1976).

Techniques for Measurement of Zinc in Biological Samples

Abstract: This chapter provides a brief description of techniques employed to assay zinc in plasma and blood cell in my laboratory. Many clinical laboratories use inaccurate and imprecise methods for assay of zinc. Since the levels of zinc in plasma and blood cells are very low, the methods must be very accurate in order to derive important biological information from this assay.

Biochemistry of Metallothionein

Abstract: Historically the term metallothionein (MT) has been used to designate the Cd-, Zn-, and Cu-containing sulfur-rich protein from equine renal cortex (Kagi and Vallee, 1960). The major characteristics of this protein were defined by Kagi et al. (1974) and Kojima et al. (1976).

Zinc and Neurobiology

Abstract: Zinc deficiency is known to affect the development of many derivatives of the primitive neural tube. Defects such as agenesis and dysmorphogenesis of the brain, spinal cord, eyes, and olfactory tract have been reported in the offsprings of zinc-deficient female rats (Hurley and Shrader, 1972). Hydrocephalus caused by closure of the aqueducts of Sylvius has also been noted as a result of zinc deficiency (Hurley, 1974). In general, the pattern of early brain malformations appears to be consistent with impaired mitosis during embryonic development and the involvement of zinc in DNA synthesis and cell division offers a plausible explanation of these observations (see Figs. 8-1, 8-2, and 8-3). It has also been suggested that the developing brain is more sensitive to zinc deficiency with respect to cell division than other organs (Eckert and Hurley, 1977).

Metabolism of Zinc

Abstract: The primary dietary sources of zinc are red meats, seafood, and cereals (Welsh and Marston, 1983). The zinc content of raw vegetables, legumes, cereals, and even meat is not retained after cooking and the availability of zinc in various foods may be adversely affected by ligands such as phytate. Because of the above, it is difficult to estimate the actual absorbed amounts of zinc solely on the basis of zinc as calculated from food tables.

Zinc and Lipid Metabolism

Abstract: Essential fatty acids (EFA) belong to two families, those with the n-6 configuration (first double bond at the sixth carbon from the methyl terminal) and those with the n-3 configuration (first double bond at the third carbon from the methyl terminal) (see Fig. 6-1). The parent fatty acids of these two families (linoleic acid, 18:2n-6; and α-linoleic acid, 18:3n-3) cannot be synthesized in vivo,and hence are considered to be essential (Fig. 6-1). Their products are formed by stepwise desaturation and elongation reactions characteristic of the metabolism of long-chain fatty acids.

Zinc and Hormones

Abstract: Zinc supplementation studies first performed in Egypt demonstrated reversible growth retardation in zinc-deficient human subjects (Prasad, 1966; Sandstead et al, 1967) Following zinc supplementation, the average increment in height in male subjects between the ages of 14 and 20 (average 17 years) was 50 inches per year Biochemical studies were consistent with the concept that the growth retardation in these subjects was the result of deficiency of zinc