Showing papers on "Zinc published in 1989"

Neurobiology of zinc and zinc-containing neurons.

Abstract: Publisher Summary This chapter discusses separate pools of CNS zinc, which are, vesicular zinc, free zinc, and protein-bound zinc Vesicular zinc is the one which is sequestered in the presynaptic vesicles of a special class of neurons, the zinc-containing neurons, which are found primarily in limbic, cerebrocortical, and corticofugal systems This vesicular zinc can be selectively stained by several histochemical procedures and is, therefore, accessible to histological and histoanalytical studies The second pool, free zinc, is an entirely hypothetical pool of ionic Zn +2 in the cytosol or interstitial fluid that may or may not be present in normal, healthy brain tissue The third pool of zinc is that which is bound firmly into the structure of the many zinc-containing enzymes in the brain The enzymatic zinc is, therefore, a stable pool, involved only in the specific function of the zinc-containing enzymes Zinc metalloenzymes are essential to the normal biology of brain cells, and any experimental treatment that is extreme enough to affect the metalloenzymes, such as prolonged zinc undernutrition or administration of chelators, can disrupt brain function through metalloenzymatic effects

Zinc in Human Biology

Abstract: 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.

Comparative strategies of heavy metal accumulation by crustaceans: zinc, copper and cadmium in a decapod, an amphipod and a barnacle

Abstract: This study investigates the comparative strategies of accumulation under standardised laboratory conditions of the essential metals zinc and copper, and the non-essential metal cadmium by three crustaceans of different taxa; vizPalaemon elegans Rathke (Malacostraca: Eucarida: Decapoda),Echinogammarus pirloti (Sexton & Spooner) (Malacostraca: Peracarida: Amphipoda) and the barnacleElminius modestus Darwin (Cirripedia: Thoracica). The decapodP. elegans regulates body zinc concentrations to a constant level (ca. 79 µg Zn g−1) over a wide range of dissolved metal availabilities until regulation breaks down at high Zn availabilities and net accumulation begins. The amphipodE. pirloti accumulates zinc at all dissolved zinc concentrations but at a low net rate such that the accumulation strategy approaches that of regulation. The barnacleE. modestus accumulates zinc to high body concentrations with no significant excretion of accumulated zinc. In the case of copper,P. elegans similarly regulates body copper concentrations to a constant level (ca. 129 µg Cu g−1) over a range of dissolved copper availabilities until regulation breaks down at high copper concentrations. Both the amphipodE. pirloti and the barnacleE. modestus on the other hand accumulate copper at all dissolved copper exposures with no evidence of regulation. All three crustaceans accumulate the non-essential metal cadmium at all dissolved cadmium concentrations without regulation. Heavy metal accumulation strategies therefore vary between crustacean taxa and between metals. Uptake rates for zinc and cadmium have been estimated for the three crustaceans and can be interpreted in terms of cuticle permeability and way of life of each crustacean. Examination of these uptake rates provides an insight into possible reasons behind the adoption of particular metal accumulation strategies.

Corrosion Mechanisms for Nickel Exposed to the Atmosphere

Abstract: Physical and chemical information on zinc corrosion layer formation, evolution, morphology, and chemical makeup is organized and presented, together with information on minerals containing zinc and other crystalline structures that might be expected to be present. The chemical reactions involved in the formation of these constituents during the corrosion process are then surveyed. The pH of the aqueous surface film is found to be crucial to the corrosion process, since it controls the dissolution of the passive oxyhydroxide surface. (The outdoor pH is largely a function of atmospheric and and is low in fogs and some rains, near neutral in dew, and generally lower in winter than in summer; indoors, the surface acidity is controlled by the composition of deposited particles.) The transition from traditional winter maxima in outdoor zinc corrosion to the more recent summer and fall maxima is explained as the juxtaposition of annually‐varying rates of bisulfite oxidation by and of atmospheric concentrations. Indoors, most of the surface degradation can be attributed to adsorbed sulfate aerosol particles; the indoor corrosion rates can be constrained to negligible levels by maintaining moderate relative humidities. Zinc is the only one of the common industrial metals for which a product containing carbonate is abundant, but sulfates and chlorides appear as well. In each case, the predominant forms are the slightly soluble hydroxide mixed salts. While full quantitative analyses of atmospheric zinc corrosion are not yet possible, it is clear that the process can only be understood in the context of the anionic surface chemistry of zinc.

Effect of chemical forms of cadmium, zinc, and lead in polluted soils on their uptake by cabbage plants

Abstract: Seven soils which had been polluted with heavy metals from a zinc smelter were sequentially extracted so that Cd, Zn, and Pb could be partitioned into five operationally defined chemical fractions: exchangeable, bound to carbonate, bound to Fe−Mn oxide, bound to organic matter, and residual. Cabbage was planted in the soils to examine the effects of concentration and chemical form of the metals in soil on their uptake. The exchangeable fraction contained 55, 13, and 6%, and carbonate fraction 11, 10, and 6% of the total Cd, Zn, and Pb, respectively. The highest amount of Zn (42%) was detected in residual, and Pb (43%) in organic fraction. Metal levels in plant were in accord with their levels in soil. Heavy metals in exchangeable and carbonate forms strongly controlled their uptake more than the total content in soil. Proportion of metal uptake to their amount in the soils was Cd>Zn>Pb agreeing with soluble sequence of the elements in soil. The uptake rate of exchangeable+carbonate forms was the same for the three elements (0.76, 1.01, and 0.98% of Cd, Zn, and Pb, respectively).

Papillomavirus polypeptides E6 and E7 are zinc-binding proteins.

Abstract: Papillomavirus proteins E6 and E7 have Cys-X-X-Cys repeats which have been suggested to mediate zinc binding. We have developed a modification of an assay that detects zinc binding to proteins immobilized on filters. Using well-characterized metalloproteins, we show that, under reducing conditions, this assay distinguishes proteins that coordinate zinc through cysteine residues from those that bind the metal through other amino acids. Under these conditions, E6 and E7 polypeptides of human papillomavirus type 18 and bovine papillomavirus type 1 exhibited high-affinity zinc binding. Our results suggest that E6 and E7 are metalloproteins and may coordinate the metal ions through cysteine residues.

Zinc methionine for ruminants: relative bioavailability of zinc in lambs and effects of growth and performance of growing heifers.

Abstract: Studies were conducted to evaluate zinc methionine (ZnMet) as a source of Zn for ruminants. Experiment 1 compared the availability of Zn in ZnMet and zinc oxide (ZnO) in lambs fed a semi-purified diet deficient in Zn. Based on growth rate and animal performance, plasma Zn and plasma alkaline phosphatase activity, no differences in Zn availability were detected between the two Zn sources. Apparent absorption of Zn also was similar, but Zn retention was higher (P less than .01) in lambs fed ZnMet because of a tendency for lower urinary Zn excretion (P less than .19) in this group. Zinc absorption and retention by lambs were similar for the two Zn sources in Exp. 2 when 20 mg Zn/kg was added to an orchardgrass hay-based diet containing 30 mg Zn/kg. In Exp. 3, lambs were dosed orally with 300 mg of Zn as ZnO or ZnMet, and the increase in plasma Zn following dosing was monitored. The increase in plasma Zn above predosing values was similar at 6 h but was higher at 12 (P less than .10) and 24 h (P less than .05) postdosing in lambs given ZnMet. Thirty-six Hereford x Simmental heifers (271 kg) were used in Exp. 4 to determine the influence of supplementing Zn (25 mg/kg) as ZnO or ZnMet of growth performance and Zn status. Heifers were fed a corn silage-based diet that contained 23.1 mg Zn/kg during the 126-d study. Zinc supplementation to the basal diet increased (P less than .05) gain and feed/gain during the first 56 d, but not for the entire 126-d study.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasmid-determined inducible efflux is responsible for resistance to cadmium, zinc, and cobalt in Alcaligenes eutrophus.

Abstract: In Alcaligenes eutrophus CH34, resistance to chromate is plasmid determined, inducible, and based on decreased net accumulation of the metal anion. Plasmid-encoded resistances to zinc, cadmium, cobalt, and nickel are resulting from inducible, energy-dependent cation efflux systems.

Determination of iron, cobalt, copper, zinc, rubidium, molybdenum, and cesium in human serum by inductively coupled plasma mass spectrometry.

Abstract: A method was developed for the determination of seven trace elements (Fe, Co, Cu, Zn, Rb, Mo, and Cs) in human serum by inductively coupled plasma mass spectrometry (ICP-MS). Sample preparation was kept as limited as possible. As the only sample pretreatment serum samples were diluted with nitric acid and indium was added as an internal standard. The results for iron, cobalt, copper, and zinc were corrected for interferences from polyatomic ions by using a blank solution containing the same concentration of sodium, sulfur, chlorine, and calcium as human serum. For copper and zinc the corrections are small, whereas for iron and cobalt they are important. No interferences occur for the considered isotopes of rubidium, molybdenum, and cesium. In order to test the accuracy and precision of the analytical technique, a "second-generation biological reference material (human serum)" was analyzed. The results obtained by ICP-MS for the seven elements considered showed good agreement with the certified values.

Carboxylate-histidine-zinc interactions in protein structure and function

Abstract: The three-dimensional structures of proteins contained in the Brookhaven Protein Data Bank were analyzed for bound metal ions. Well over 150 unique protein structures are available which contain seven different types of bound metal ions. Iron, calcium, and zinc are most commonly observed, and the extended coordination polyhedra of biological zinc are the subject of this study. In particular, histidine residues ligating zinc ions are often found to bridge both the zinc ion and the carboxylate side chain of a nearby aspartate (sometimes glutamate) residue. We refer to the carboxylate-histidine-zinc interaction as indirect carboxylate-metal coordination, and we observe this feature in all zinc enzymes of reported three-dimensional structure. Additionally, we also observe a related carbonyl-histidine-zinc interaction in some metalloproteins. We observe some direct carboxylate-zinc interactions, and their coordination stereochemistry is exclusively syn with respect to the carboxylate. On the basis of available protein structures and known homologues thereof, more than 30 examples of indirect carboxylate-zinc coordination across bridging histidine can be identified. The carboxylate-histidine-zinc triad may be important in the function of many zinc-containing proteins and enzymes, e.g., by strengthening metal complexation or modulating the nucleophilicity of zinc-bound water. The presence of an uncomplexed carboxylate-histidine couple (a grouping more basic than histidine alone) in a native protein can also signal a regulatory metal binding site. Indeed, the Asp"—His couple of the serine protease active site may comprise a structural, evolutionary link to the Asp"—His of the zinc protease metal coordination polyhedron.

Effect of Protein Level and Protein Source on Zinc Absorption in Humans

Abstract: The effect of increasing levels of various protein sources on zinc absorption from a legume-based meal was studied in humans with the use of a radionuclide technique. The meals were extrinsically labelled with 65Zn and absorption was determined from measurements of the whole-body retention of the isotope. The mean fractional zinc absorption for the 13 meals was 24.7 +/- 6.9% and was only influenced by the protein content of the meal to a limited extent (r = 0.45). However, the amount of zinc absorbed from the meals was strongly correlated with both the protein (r = 0.85) and zinc content (r = 0.86): 5.9 +/- 1.7 mumol of zinc was absorbed from the basal bean meal which had the lowest protein content; the addition of low zinc chicken doubled the protein content and increased zinc absorption to 10.3 +/- 2.0 mumol; the addition of zinc-rich beef also doubled the protein content, however, zinc absorption was increased to 15.9 +/- 4.7 mumol. It is concluded that the zinc content of the main protein source of the diet determines the amount of zinc absorbed to a large extent. However, relatively small amounts of animal protein can significantly improve the value of a legume-based meal as a source of zinc.

Zinc absorption in human small intestine.

Abstract: We determined the intestinal site of zinc absorption in humans and investigated the interaction between intestinal absorption of zinc and other solutes using the triple-lumen steady-state perfusion technique. Twenty-one healthy subjects participated in the study. During intestinal perfusion of a balanced electrolyte solution containing 0.1 mM zinc acetate, zinc absorption occurred throughout the entire small intestine. However, the jejunum had the highest rate of absorption (357 +/- 14 nM.min-1.40 cm-1) compared with the duodenum (230 +/- 33 nM.min-1.40 cm-1) and ileum (84 +/- 10 nM.min-1.40 cm-1). Over a range of zinc concentrations infused into the jejunum (0.1, 0.9, and 1.8 mM) there were linear increases in the rate of zinc absorption (P less than 0.05). Intestinal absorption of zinc was significantly stimulated by the addition of glucose (20 mM). Zinc absorption increased from 459 +/- 39 to 582 +/- 45 nM.min-1.40 cm-1 (P less than 0.05). Conversely, zinc (0.9 mM) also enhanced the absorption of glucose, which was increased from 293 +/- 43 to 447 +/- 27 microM.min-1.40 cm-1 (P less than 0.05). The enhanced absorption of zinc or glucose was not accompanied by any increase in absorption of water and sodium. In contrast, increasing the concentration of zinc in the perfusate resulted in decreased absorption of sodium and water in a dose-related manner. In conclusion, our study demonstrated that zinc absorption is concentration dependent and occurs throughout the small intestine. The jejunum has the highest rate of absorption of zinc. The interactions between absorption of zinc and other solutes suggest that the transport process of zinc is carrier mediated.

The accumulation and the effect of heavy metals on the water fern Azolla filiculoides

Abstract: Azolla filiculoides Lamarck grown for 3-7 days in nutrient media containing 8-1 5 ppm of different heavy metals was found to contain about 10000 ppm cadmium, 1990 ppm chromium, 9000 ppm copper, 9000 ppm nickel and 6500 ppm zinc. The content of heavy metal in the roots was two- to five-fold higher than in the shoots, and 98 %h of the heavy metals were bound to the insoluble fraction of the Azolla. The content of heavy metals in dead dried Azollia was 3-7 times higher than in the living plants. Zinc and cadmium were more readily transferred from the roots to the shoots than nickel, copper and chromium. Growth in the presence of the heavy metals resulted in severe leakage of K', Mg2" and Na+ ions from the roots with less leakage of Ca2". The effect of heavy metals on the loss of K', Na+ and Mg2" from the shoots was more limited. Nitrogenase activity was almost completely inhibited by cadmium, nickel and zinc, while copper and chromium had less effect. Azolla may prove useful in the detoxification of industrial effluents.

Poly(ADP-ribose)polymerase: a novel finger protein

Abstract: By Energy Dispersive X-ray fluorescence we have determined that calf thymus poly(ADP-ribose) polymerase binds two zinc ions per enzyme molecule. Using 65Zn (II) for detection of zinc binding proteins and polypeptides on western blots, we found that the zinc binding sites are localized in a 29 kd N-terminal fragment which is included in the DNA binding domain. Metal depletion and restoration experiments proved that zinc is essential for the binding of this fragment to DNA as tested by Southwestern assay. These results correlate with the existence of two putative zinc finger motifs present in the N-terminal part of the human enzyme. Poly(ADP-ribose)polymerase fingers could be involved in the recognition of DNA strand breaks and therefore in enzyme activation.

Copper–zinc oxide catalysts. Activity in relation to precursor structure and morphology

Abstract: Cu–Zn hydroxycarbonates have been studied as precursors of Cu–ZnO catalysts, with particular reference to the effect on catalyst activity of ageing the precursor prior to decomposition and reduction. The precursor obtained by precipitation from mixed nitrate solution (Cu/Zn molar ratio 2:1) at 333 K and pH 7.0 consisted of zincian malachite (Cu/Zn ≈ 85:15) and aurichalcite. The precursor was aged in the mother liquor at 333 K for various times. Characterisation by XRD, i.r., DTA, electron microscopy, EDAX and XPS showed that ageing led to loss of the aurichalcite and production of a more finely divided copper-enriched (Cu/Zn = 2:1) malachite phase. The unaged precursor yielded a catalyst of low activity for both methanol synthesis (studied at 50 bar and at 1 bar) and the reverse water-gas shift reaction. The aged precursor gave catalysts of much higher activity for both reactions. Increased ageing did not change the selectivity ratio for methanol synthesis vs. reverse shift in the CO2+ H2 reaction at normal pressure.

Proton NOE studies on dicopper(II) dicobalt(II) superoxide dismutase

Abstract: Substitution of zinc (II) with cobalt (II) in copper zinc superoxide dismutase gives rise to a derivative suitable for 1 H NMR investigation owing to the magnetic coupling between the two metal ions. 1 H NOE measurements have been performed in order to relate them to interproton distances

Cadmium carcinogenesis in male Wistar [Crl:(WI)BR[ rats: dose-response analysis of effects of zinc on tumor induction in the prostate, in the testes, and at the injection site

Abstract: The ability of zinc acetate to modify the carcinogenic effects of CdCl2 in male Wistar [Crl:(WI)BR] rats was studied over a 2-year period. Groups of rats received a single s.c. injection of Cd (30.0 mumol/kg) in the dorsal thoracic midline or i.m. in the right thigh at time 0. Zinc was given in three separate s.c. doses of 0.1, 0.3, or 1.0 mmol/kg (at -6, 0, and +18 h relative to cadmium) in the lumbosacral area or p.o. at 100 ppm in the drinking water (-2 to +100 weeks). Cadmium treatments (s.c.) resulted in the appearance of tumors at the injection site and in the testes. The incidence of s.c. injection site tumors (mostly mixed sarcomas) was markedly reduced by high dose (1.0 mmol/kg) s.c. zinc (50% reduction) and was almost abolished by p.o. zinc (92% reduction). Testicular tumors (mostly Leydig cell adenomas) induced by s.c. cadmium were reduced in a dose-related fashion by zinc and were found to be highly dependent on the ability of zinc to prevent the chronic degenerative effects of cadmium in the testes. Oral zinc had no effect on s.c. cadmium-induced testicular tumors, while i.m. cadmium alone did not induce these tumors. In rats in which s.c. cadmium-induced testicular tumors and chronic degenerative effects were prevented by zinc (1.0 mmol/kg, s.c.), a marked elevation in prostatic tumors (exclusively adenomas) occurred (control, 9.6%; cadmium plus high zinc 29.6%). Cadmium given i.m., which did not result in testicular tumors or degeneration, also induced an elevated incidence (42.3%) of prostatic tumors, again indicating a dependence on testicular function. Prostatic tumor incidence was also significantly elevated (25.0%) in rats receiving 1.0 mmol/kg zinc, s.c., in combination with i.m. cadmium. These results indicate that zinc inhibition of cadmium carcinogenesis is a complex phenomenon, depending not only on dose and route but also on the target site in question.

The reactions of copper and zinc with calcium carbonate surfaces

Abstract: SUMMARY The reaction of copper and zinc were studied by adding the metal nitrate to a 4g:50ml suspension of calcite and water which had been equilibrated for two days, and then equilibrating for a further three days. Zinc behaved in a similar manner to cadmium in forming a surface-solid solution of ZnχCa1-χCO3 as a result of adsorption, and the pIAP of the equilibrium solutions were close to those expected from the Thorstenson & Plummer equation. However, the continuity from adsorption to precipitation was broken by the formation of Zn5(OH)6(CO3)2 which has a higher stability than ZnCO3. The CaCO3 surface appears to constrain the adsorbed Zn to conform to a carbonate structure despite its lower stability than the hydroxy carbonate. The adsorption data for Cu can also be explained in terms of a surface-solid solution of CuχCa1-XCO3, but CuCO3 is not found naturally because of much greater stability of Cu(OH)2, and so there is no independent value for the solubility of a CuCO3 end-member if a surface-solid solution is formed. Secondary reactions are more likely to occur for Cu, especially close to the adsorption-precipitation boundary. Continuity from adsorption to precipitation again was not found. Theory predicts that Cu is less likely to form a surface-solid solution than Zn. Upper Chalk (calcite with 4% other minerals, mostly quartz) behaved in a similar way but with increased adsorption due to its higher surface area.