1. Physiology of Zinc: General Aspects.- 2. An Introduction to the Biochemistry of Zinc.- 3. Intestinal Absorption of Zinc.- 4. Promoters and Antagonists of Zinc Absorption.- 5. Systemic Transport of Zinc.- 6. Systemic Interactions of Zinc.- 7. Biochemistry of Zinc in Cell Division and Tissue Growth.- 8. Zinc in Cell Division and Tissue Growth: Physiological Aspects.- 9. Biochemical Pathologies of Zinc Deficiency.- 10. Zinc and Iron in Free Radical Pathology and Cellular Control.- 11. Zinc Status and Food Intake.- 12. Zinc and Reproduction: Effects of Deficiency on Foetal and Postnatal Development.- 13. A Note on Zinc and Immunocompetence.- 14. Zinc and Behaviour.- 15. Neurobiology of Zinc.- 16. Zinc in Endocrine Function.- 17. Severe Zinc Deficiency.- 18. Mild Zinc Deficiency in Human Subjects.- 19. Putative Therapeutic Roles for Zinc.- 20. The Diagnosis of Zinc Deficiency.- 21. Human Zinc Requirements.- 22. Dietary Pattern and Zinc Supply.- 23. Zinc Excess.- 24. The Biological Significance of Zinc for Man: Problems and Prospects.

Zinc in Human Biology

Publisher Summary The chapter discusses cerebral protein metabolism, general problems of protein metabolism in other organs and organisms, and some of the recent reviews discussing the areas of importance in cerebral protein metabolism. In the brain, more than in any other organ, the functional metabolism seems to involve changes in the proteins of the organ. The controlling factors of cerebral protein metabolism are of interest, particularly because there is very little regeneration in the central nervous system. Some diseases of the nervous system are apparently caused by the lack of some enzyme proteins normally present. In other diseased states, the presence of abnormal proteins, and structural changes in normal proteins, are found. Also of interest are the reported effects of a number of drugs on cerebral protein metabolism. The control of protein metabolism in all its aspects is the most important problem. It is related to processes of growth, differentiation, degeneration, as well as maintenance of the cells and their protein complement. The growth factor discussed affects one or more of these processes. This factor is specific for a part of the nervous system, but controlling factors of decisive influence may be operative that are specific for other parts of the nervous system, or specific for a cell type in other organs. The knowledge of the mechanism of action of such factors sheds light on the control mechanisms of cellular metabolism.

Protein metabolism of the nervous system.

In the experiments to be described a histochemical study has been made of the distribution of true and pseudo-cholinesterase in the hypothalamus of the dog. There is considerable evidence to indicate that cholinergic neurones are involved in the release of neurohypophyseal hormones. Pickford (1939) showed that the intravenous injection of acetylcholine (ACh) produced antidiuresis in atropinized dogs, and that this antidiuresis was reduced or abolished by surgical removal of the posterior lobe of the pituitary. She therefore concluded that the ACh caused release of the antidiuretic hormone. Later experiments (Pickford, 1947; Duke, Pickford & Watt, 1950) showed that the ACh most probably acted on the neurones of the hypothalamus, since injections of ACh, as well as anticholinesterases, into the supraoptic nuclei, produced antidiuresis in chloralosed dogs, but only as long as the posterior lobe of the pituitary was intact. The injection of the irreversible anticholinesterase, diisopropylfluorophosphate (DFP), into the supraoptic nucleus produced immediate antidiuresis followed by prolonged polyuria. This prolonged polyuria was attributed to permanent paralysis of neurones resulting from local excess of ACh. There is some evidence that the neurones concerned with the release of oxytocin are also cholinergic, since the injection of DFP into the supraoptic nucleus increases spontaneous uterine activity (Abrahams & Pickford, 1956). So far no histochemical studies have been performed concerning the distribution of cholinergic neurones in the hypothalamus. From histochemical studies it is known that the peripheral and central nervous system cholinergic neurones contain high concentrations. of true cholinesterase, whereas non-cholinergic

https://physoc.onlinelibrary.wiley.com/doi/pdf/10.1113/jphysiol.1957.sp005881

Histochemical demonstration of cholinesterases in the hypothalamus of the dog.

Reugents. ~-[l-~~C]Glutamic ac d (9.5 pCi/pmol) was obtained from Volk Radiochemical Co. (Skokie, Ill.) pyridoxal phosphate was from Mann Chemical Co. (New York), and NCSTY reagent was from Nuclear Chicago Co. @es Plaines, Ill.) All other chemicals were reagent grade, obtained from Sigma Chemical Company (St. Louis, Mo.), and stored in glass distilled water at -20°C unless otherwise indicated. Analytical method. The method of ALBERS and BRADY (1959) was followed with a number of modifications. The incubation, diffusion, and counting tubes were manipulated by hand rather than with a micromanipulator. F'yndoxal phosphate was used at 1.1 m rather than 0.5 m ~ ; 2-Mercaptoethanol (10 m) and Triton X-100 (05%. w/v) were added to the incubation medium; and 84 msodium-potassium phosphate with sodium and potassium both 42 m was used instead of 0.1 m~ potassium phosphate. NCST' solution (HANSEN and Bum, 1967) was used to trap evolved CO, and 1 4 C O t in place of the free base of p-(diisobutylcresoxyethoxyethyl) dimethyldibenzylammonium chloride (Hyamine).

Brain glutamate decarboxylase: changes in the developing rat brain.

THE distribution of acid phosphatase in the central nervous system as demonstrated by histochemical methods has been investigated by LANDOW, KABAT and NEWMAN (1942), WISLOCKI and DEMPSEY (1948), and by SHIMIZU (1950) in comparative studies that included mice, rats, guinea pigs, rabbits, cats and chickens. Numerous papers deal with the cytological distribution of acid phosphatase in selected regions of the brain of various species, but little attention has been given to gradations of enzyme activity among those regions. The present paper reports a mapping of acid phosphatase activity in the brain of the rhesus monkey. A quantitative histochemical method was used, based upon spectrophotometric measurements of dye extracts from standard size tissue discs taken from brain sections that had been incubated with a substrate for acid phosphatase. Previous mappings of oxidative enzymes (FRIEDE, 1961), and particularly a mapping of lactate dehydrogenase in the brain of the rhesus monkey (FRIEDE and FLEMING, 1963), facilitate comparison of enzyme patterns. MATERIAL AND METHODS Histochemical method. Preliminary testing and standardization of the quantitative method for acid phosphatase activity were done on cat and monkey brains; a detailed account of methodology will be given elsewhere. For the present experiment three adult, healthy rhesus monkeys were killed under pentothal anaesthesia; the brains were removed immediately and placed in 10 % formalin at 4". After 8 hr fixation, the material was cut into slices, 3-5 mm thick. Twenty-four hours after removal of each brain, 30 p frozen sections were cut, rinsed, and stored in chilled distilled water until all material from the brain had been prepared. All sections were transferred to a 4-litre Erlenmeyer flask containing a small portion of the buffer component of the incubation medium. The substrate and diazo salt were mixed with the remaining portion of the buffer and filtered as quickly as possible; the filtrate was added immediately to the sections and buffer in the Erlenmeyer flask and incubation was started. The incubation medium was a mixture of 1 mg of sodium-a-naphthyl phosphate (Signia Chemical Co. St Louis, Missouri) and 1 mg of the stable diazotate of o-amino azotoluene (Fast Garnet GBC) (Dajac Laboratories, Philadelphia) in 1 ml of 0.2 M-Walpole buffer of pH 5 (PEARSE, 1960). For each monkey brain approximately 2 I. of reaction mixture were used. The sections were incubated in an Eherbach water-bath shaker with constant agitation for 1 hr at 38". The reaction was stopped by transferring all sections into a large quantity of 10% formalin. The stained sections were mounted temporarily on a microslide covered with three layers of parafilm. Discs were cut from selected areas of the sections with stainless steel tubes, 1.1 mm and 2.4 mm in diameter. Each disc was placed in a stoppered test tube containing a drop of distilled water. Care was taken not to transfer particles of parafilm into the tubes since these would cause turbidity and false readings. The azo dye was extracted with 1 ml of chloroform-ethanol (1 :l), v/v and the colour density was determined within 10-30 min at 555 mp in microcells in a Beckman DU spectrophotometer. For the data collected in Table I an average of ten samples were taken from the regions indicated for each monkey, and means and standard deviations were calculated. The dependability of this method was tested in various experiments (unpublished data) the results of which are only briefly summarized: tissue fixed in formalin after incubation was used since it was impractical to cut discs from loose sections During the required 24-hr fixation period, some loss of

/pdf/a-quantitative-mapping-of-acid-phosphatase-in-the-brain-of-2514dj0xvl.pdf

A quantitative mapping of acid phosphatase in the brain of the rhesus monkey.

FLFXNER (1955) has shown that the cytological changes occurring during the development of nervous tissues are associated with concurrent changes in the pattern of enzymic activity. Changes have been reported in the activity of various enzymes in a number of localized regions of the brain (NACHMANSOHN, 1939, 1940; YOUNGSTROM, 1941; H~MWICH and APRXSON, 1955), but little systematic information is available, however, about the enzymes of the hypothalamus. The hypothalamic centres are of interest in view of their role in relation to the chief autonomic and endocrine functions of the body, and since they may also influence the activity of the cerebral cortex (LE GROS CLARK and MEYER, 1950). The vegetative functions of the hypothalamus are particularly important in the 'early life of the animal. The development of biochemical activity in the hypothalamo-neurohypophysial system was studied by HELLW and ZAIMIS (1949), who found a lower concentration of antidiuretic hormone in the neurohypophysis of the newborn than of the adult rat. DAWSON (1953) observed the appearance of neurosecretory substance in the hypothalamus and posterior pituitary of the rat within a few days after birth. In the present investigation the maturation of the hypothalamus of the rat was studied by following the changes with age in the activities of the enzymes phosphomonoesterase I and I1 (nonspecific alkaline and acid phosphatase) and acetylcholinesterase. The values obtained for the hypothalamus were compared with values obtained concurrently for the cerebral cortex and the thalamus. In addition, histochemical techniques were applied to study the localization of the two phosphomonoesterases in the different hypothalamic nuclei. More information was thus obtained about the distribution of these enzymes than could be obtained by biochemical or histochemical methods alone.

P. Cohn

Papers

Enzymic development and maturation of the hypothalamus.