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Showing papers on "Zinc published in 1993"


Journal ArticleDOI
TL;DR: High concentrations of certain metals may play a role in the pathogenesis of AD by promoting aggregation of human βA4, a 40‐mer whose neurotoxicity is related to its aggregation.
Abstract: A major pathological feature of Alzheimer's disease (AD) is the presence of a high density of amyloid plaques in the brain tissue of patients The plaques are predominantly composed of human beta-amyloid peptide beta A4, a 40-mer whose neurotoxicity is related to its aggregation Certain metals have been proposed as risk factors for AD, but the mechanism by which the metals may exert their effects is unclear Radioiodinated human beta A4 has been used to assess the effects of various metals on the aggregation of the peptide in dilute solution (10(-10) M) In physiological buffers, 10(-3) M calcium, cobalt, copper, manganese, magnesium, sodium, or potassium had no effect on the rate of beta A4 aggregation In sharp contrast, aluminum, iron, and zinc under the same conditions strongly promoted aggregation (rate enhancement of 100-1,000-fold) The aggregation of beta A4 induced by aluminum and iron is distinguishable from that induced by zinc in terms of rate, extent, pH and temperature dependence These results suggest that high concentrations of certain metals may play a role in the pathogenesis of AD by promoting aggregation of beta A4

487 citations



Journal ArticleDOI
TL;DR: Zinc is a factor that modulates the functional properties of the substrate for beta A4 amyloidogenesis and has been shown to potentiate the inhibition of coagulation factor XIa by an APP isoform containing a Kunitz-type inhibitory domain.

313 citations


Journal Article
TL;DR: Improvement in response to skin-test antigens and taste acuity was observed after zinc supplementation, and a mild zinc deficiency appears to be a significant clinical problem in free-living elderly people.

246 citations


Journal ArticleDOI
TL;DR: Daily gain and daily feed intake were increased by ZnO addition, regardless of level, whereas ZnSO4 addition increased these performance indices only at the 3,000 mg of Zn/kg level of supplementation.
Abstract: Three trials were conducted to evaluate high levels of Zn addition from various Zn sources on growth performance and plasma Zn responses of 8-kg pigs. Zinc supplements were added to 20% CP starting diets (125 mg of Zn/kg) containing antibiotics. Trial 1 was done to evaluate plasma Zn responses of pigs fed three different feed-grade Zn sources: ZnO where supplemental Zn levels were 0, 250, 500, 1,000, 3,000, and 5,000 mg/kg; ZnSO4 at 1,500 or 2,500 mg of Zn/kg; and a zinc-lysine complex (Zn-Lys) at 1,500 or 2,500 mg of Zn/kg. Plasma Zn concentration as a function of supplemental Zn intake was fitted to a broken-line for ZnO data and to simple linear models for ZnSO4 and Zn-Lys data. For ZnO, plasma Zn did not increase until concentrations > 1,000 mg Zn/kg were fed. Above this level, plasma Zn increased linearly (P < .01) for all three sources of Zn, although slopes of the ZnO and Zn-Lys response curves were 56% (P < .05) and 110%, respectively, of the ZnSO4 slopes. In Trial 2, five diets were fed: basal, 3,000 and 5,000 mg of Zn/kg from ZnO, and 3,000 and 5,000 mg of Zn/kg from ZnSO4. Daily gain and daily feed intake were increased (P < .05) by ZnO addition, regardless of level, whereas ZnSO4 addition increased these performance indices only at the 3,000 mg of Zn/kg level of supplementation. Plasma Zn responses to ZnSO4 addition were almost double those of ZnO addition.(ABSTRACT TRUNCATED AT 250 WORDS)

243 citations


Book ChapterDOI
01 Jan 1993
TL;DR: In this paper, the root responses to deficiency of phosphorus or iron are identified as root response to rhizosphere acidification or enhanced excretion of organic acids and chelators.
Abstract: Characterizing zinc availability by soil testing provides important information on the pool size of zinc potentially available for uptake. Concentrations of zinc in soil solution, particularly at high soil pH, however, are very low and mobility and transport to the root surface are usually rate limiting factors of soil supply. Utilization of potentially available zinc is thus mainly or exclusively confined to rhizosphere soil. Root-induced changes in the rhizosphere are of particular imporatance for zinc uptake from soils. In soils of high pH, rhizosphere acidification by supply of ammonium nitrogen, or for legumes by N2 fixation, are effective mechanisms in enhancing zinc mobilization. The same holds true for rhizosphere acidification or enhanced excretion of organic acids and chelators as root responses to deficiency of phosphorus or iron. Root colonization by VA mycorrhizae increases spatial availability of zinc similarly to that of phosphorus. Mycorrhizal plants usually have higher zinc contents in the shoot dry matter and are less sensitive to zinc deficiency than non-mycorrhizal plants. As a rule, all factors which impair root colonization by VA mycorrhizae, including high levels of soil or fertilizer phosphorus, tend to decrease zinc contents in plants and increase the risk of zinc deficiency in plants grown on soils low in extractable zinc. Marked genotypical differences in zinc efficiency are usually caused by differences in zinc acquisition from soils. In lowland rice zinc deficiency is widespread in neutral and alkaline soils. Elevated bicarbonate concentrations are the major factor responsible for low zinc contents in rice plants grown on high pH soils, high in organic matter. In such soils the high bicarbonate concentrations impair zinc uptake by direct inhibition of root growth and activtiy.

230 citations


Journal ArticleDOI
TL;DR: Comparison of binding strengths was possible only through the calculation of an intrinsic stoichiometric binding constant and it was suggested that while both histidyl and carboxyl groups appear to be involved in copper binding, Histidyl residues alone were sufficient for zinc binding.

216 citations


Book ChapterDOI
01 Jan 1993
TL;DR: Though the understanding of the function of zinc has increased greatly in the last thirty years, there are still many aspects of zinc metabolism that remain controversial.
Abstract: The essential micronutrient zinc occurs in plants either as a free ion, or as a complex with a variety of low molecular weight compounds. Zinc may also be incorporated as a component of proteins and other macromolecules. As a component of proteins, zinc acts as a functional, structural, or regulatory cofactor of a large number of enzymes. Many of the physiological perturbations resulting from zinc deficiency are associated with the disruption of normal enzyme activity, thus zinc-deficiency induced inhibition of photosynthesis is coincident with a decrease in activity of key photosynthetic enzymes. Zinc deficiency also increases membrane leakiness by inhibiting the activity of enzymes involved in the detoxification of membrane damaging oxygen radicles. Recent evidence suggests that zinc plays a key role in stabilizing RNA and DNA structure, in maintaining the activity of DNA synthesizing enzymes and controlling the activity of RNA degrading enzymes. Thus, zinc may play a role in controlling gene expression. Though our understanding of the function of zinc has increased greatly in the last thirty years, there are still many aspects of zinc metabolism that remain controversial. In the following review we summarize the current knowledge of the physiology of zinc and illustrate areas in which our knowledge remains incomplete.

210 citations


Book ChapterDOI
01 Jan 1993
TL;DR: In this article, the interactions between Zn and other nutrients in soil reactions, behavior in plants and plant growth are examined, showing that Zn plays an important role in plant growth.
Abstract: This paper examines the interactions between Zn and other nutrients in soil reactions, behaviour in plants and plant growth.

200 citations



Book ChapterDOI
TL;DR: This chapter discusses the preparation and handling of cobalt enzymes and the nature of the information that can be obtained from spectroscopic measurements regarding the role of the metal center.
Abstract: Publisher Summary Cobalt ions exhibit characteristic spectra. When cobalt is introduced into proteins, the spectral properties become a desirable attribute to probe the environment of active enzymatic sites. Moreover, cobalt can be substituted for spectroscopically silent zinc when this is the native, catalytically active metal atom of enzymes. Such a metal exchange has been particularly fruitful in the study of these systems because the majority of cobalt substituted zinc enzymes retain their enzymatic activity. Hence, cobalt substitution for zinc has become an essential technique to address the structural basis of catalytic properties in zinc enzymes, as well as the coordination environment of structural zinc sites in proteins. This chapter discusses the preparation and handling of cobalt enzymes and the nature of the information that can be obtained from spectroscopic measurements regarding the role of the metal center. It evaluates the circumstances under which cobalt becomes a structural and functional substitute for zinc atoms. The existence of structural data for cobalt enzymes now makes possible such comparisons between cobalt and zinc in proteins.

Journal ArticleDOI
TL;DR: In this article, two experiments were conducted to determine the effects of supplemental microbial phytase on utilization of dietary zinc by weanling pigs, and the results indicated that either supplemental phytases or supplemental zinc increased plasma alkaline phosphatase activity and plasma zinc concentrations, but these increases were not additive.
Abstract: Two experiments were conducted to determine the effects of supplemental microbial phytase on utilization of dietary zinc by weanling pigs. Experiment 1 was a 2 x 3 factorial arrangement of treatments with 24 pigs for 4 wk. Two levels of phytase activity (0 and 1350 units/g) and three levels of zinc (0, 30 and 60 mg/kg as ZnSO4.7H2O) were added to a corn-soybean meal basal diet. Weekly measures included growth performance, plasma alkaline phosphatase activity and plasma mineral concentrations. In Experiment 2, mineral balances were determined in 12 pigs fed the basal diet or the diet with added zinc (30 mg/kg) or phytase (1350 units/g). The results indicated that either supplemental phytase or supplemental zinc increased plasma alkaline phosphatase activity and plasma zinc concentrations, but these increases were not additive. Supplemental phytase decreased plasma alkaline phosphatase activity in pigs supplemented with zinc. Supplemental phytase also significantly enhanced weight gain, feed intake, gain:feed ratio, plasma concentrations of inorganic phosphorus, and retention of phosphorus and calcium. Neither supplemental phytase nor zinc affected zinc retention. Supplementing corn-soybean meal diets with microbial phytase at 1350 units/g feed improves bioavailability of zinc as well as of phytate phosphorus to weanling pigs.

Journal ArticleDOI
TL;DR: Copper, an important angiogenic factors, is accumulated within the malignant tissues of metastatic carcinoma and malignant glioma, but not meningiomas, which may have implications regarding angiogenesis in these tumors.
Abstract: Serum copper and zinc concentrations and copper/zinc ratios have been shown to be increased in several types of human malignancies, including human brain tumors. In this study, copper and zinc levels and copper/zinc ratios were determined by atomic absorption analysis in tissue and serum from 29 primary and metastatic brain tumor patients. Metastatic carcinomas and malignant gliomas revealed significantly higher tissue copper concentrations than control tissues and meningiomas. Malignant gliomas demonstrated significantly higher tissue copper/zinc ratios. Both serum copper and copper/zinc ratio were significantly higher in the metastatic carcinoma group than control; however, serum copper levels in malignant glioma patients were not significantly different from control tissues. There were no differences both in the serum and the tissue concentrations of these trace elements in meningiomas and controls. These data suggested that copper, an important angiogenic factors, is accumulated within the malignant tissues of metastatic carcinoma and malignant glioma, but not meningiomas. These findings may have implications regarding angiogenesis in these tumors.


Book
01 Jan 1993
TL;DR: Techniques for Measurement of Zinc in Biological Samples and Interactions ofZinc with Other Micronutrients.
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.

Journal ArticleDOI
TL;DR: The FPG protein of Escherichia coli is a DNA repair enzyme with DNA glycosylase, abasic site nicking, and deoxyribose excising activities, and analysis of the amino acid sequence of this protein suggests that the Fpg protein is a zinc finger protein with a Cys-X-X2-Cys-Zn-X16-Cats motif.

Journal ArticleDOI
TL;DR: The results indicate that the cysteine motifs play an important role in transformation by HPV-18 E7 but do not contribute to Rb binding.
Abstract: Human papillomavirus type 18 (HPV-18) E7 proteins bind zinc through Cys-X-X-Cys repeats located at the C terminus of the protein. In order to examine the role of these cysteine motifs in E7 function, we expressed the HPV-18 E7 protein in bacteria and found that purified E7 forms a dimer through interactions with zinc. Mutants with single mutations within the Cys-X-X-Cys motifs bound a reduced level of zinc in a zinc blot assay, while a double mutant lost all zinc-binding activity. When expressed in vivo, none of the mutants cooperated with an activated ras oncogene to transform primary rat embryo fibroblasts, but all mutants retained nearly wild-type Rb-binding activity. The results indicate that the cysteine motifs play an important role in transformation by HPV-18 E7 but do not contribute to Rb binding.

Journal ArticleDOI
TL;DR: The power of combined quick EXAFS (QuEXAFS) and X-ray diffraction as a structural and kinetic tool in high-temperature solid-state chemistry is exemplified by the study of the conversion of Mg2+-exchanged zeolite B to cordierite, a process facilitated by trace amounts of zinc oxide as discussed by the authors.
Abstract: The power of combined quick EXAFS (QuEXAFS) and X-ray diffraction as a structural and kinetic tool in high-temperature solid-state chemistry is exemplified by the study of the conversion of Mg2+-exchanged zeolite B to cordierite, a process facilitated by trace amounts of zinc oxide. With a setup consisting of a position-sensitive detector and a rapidly scanning monochromator, time-resolved studies of short-range and long-range order within samples held in excess of 1000-degrees-C are routinely possible.

Journal ArticleDOI
TL;DR: Low-dose zinc supplementation allows restoration, at least partially, of nutritional and thymic status without the known disadvantages of high doses of zinc.

Journal ArticleDOI
TL;DR: Cocatalytic zinc binding sites are characteristic of enzyme molecules which contain two or more zinc and/or other metal atoms, and aspartate seems to be preferred over glutamate in these functional units.
Abstract: Cocatalytic zinc binding sites are characteristic of enzyme molecules which contain two or more zinc and/or other metal atoms. In each site an aspartate, glutamate, or histidine residue simultaneously binds to two zinc atoms or a zinc and a different metal atom. In the resultant amino acid bridge, two of the cocatalytic metal atoms bind to the same amino acid. Consequently the participating metal atoms are in close proximity and function as a catalytic unit, typical of this motif. In these functional units aspartate seems to be preferred over glutamate. Serine, threonine, tryptophan, and lysine residues are encountered as zinc ligands, although they have not so far been identified as ligands in monozinc enzymes or DNA-binding zinc proteins. The resultant coordination spheres and their mechanistic implications raise interesting questions for further study.

Journal ArticleDOI
TL;DR: Children responded to the zinc supplement with changes in indexes of body composition rather than growth, and was the only laboratory variable that explained some of the variance in final Z scores of midarm-muscle area and MAC.

Journal ArticleDOI
TL;DR: It is postulated that displacement of hippocampal zinc by heavy metals may be important in producing clinical memory disturbance, and analysis of the CA1 region, rather than of the dentate gyrus, would have been preferable.
Abstract: The use of inductively coupled plasma source mass spectrometry (ICP-MS) for multi-element analysis has led to the observation, in two separate studies, of increased blood tin in Alzheimer's disease (AD). We have therefore applied the technique of ICP-MS to hippocampal tissues obtained post-mortem from patients with AD and from controls. There was no significant difference in tin concentrations in AD. There were increased concentrations of aluminum and silicon, and reduced concentrations of zinc and selenium. It is postulated that displacement of hippocampal zinc by heavy metals may be important in producing clinical memory disturbance. However, analysis of the CA1 region, rather than of the dentate gyrus, would have been preferable.

Journal ArticleDOI
TL;DR: In this paper, an atomistic simulation technique was used to predict the spatial arrangement of the dopant species sodium, lithium, and chlorine within the zinc oxide lattice, which hindered the migration of zinc interstitials and hence slow the degradation of the varistor.
Abstract: An atomistic simulation technique has been used to predict the spatial arrangement of the dopant species sodium, lithium, and chlorine within the zinc oxide lattice. The alkaline oxides are preferentially incorporated via a self-compensating mode, forming interstitial cations which hinder the migration of zinc interstitials and hence slow the degradation of the varistor. The addition of chloride ions is shown to negate this effect by forming sodium and chloride substitutional defects rather than any species involving sodium interstitial ions.

Journal ArticleDOI
TL;DR: A fluoresence-based fiber optic biosensor capable of detecting zinc(II) at nanomolar concentrations is described, which transduces the specific recognition of the ion by an enzyme as change in the fluorescence of an inhibitor which binds to the zinc in the active site.
Abstract: A fluoresence-based fiber optic biosensor capable of detecting zinc(II) at nanomolar concentrations is described. The sensor transduces the specific recognition of the ion by an enzyme (carbonic anhydrase) as change in the fluorescence of an inhibitor which binds to the zinc in the active site. The concentration of metal ion is proportional to the ratio of fluorescence intensity at two wavelengths, corresponding to the emission from bound and free inhibitor. Sensing of zinc may be performed through a single optical fiber.

Journal ArticleDOI
TL;DR: In this article, the formation of zinc chlorohydroxosulfates as corrosion products in a marine environment is described by means of a multianalytical approach, which involves the consecutive formation of three structurally related phases.

Journal ArticleDOI
TL;DR: High performance liquid chromatography analyses show that increased zinc tolerance in S. vulgaris is not due to increased production of phytochelatins, but is also due to an increase in the concentration of cysteine and the production of nonidentified thiols.
Abstract: The concentration of acid-soluble thiols other than reduced glutathione (SH - GSH) increases in the roots of zinc-sensitive and zinc-tolerant Silene vulgaris (Moench) Garcke after exposure to zinc for 1 to 3 d. The concentration of SH - GSH in the roots is higher in the sensitive plants than in the tolerant ones, both at equal external zinc concentrations and at zinc concentrations causing the same level of root-length growth inhibition. High performance liquid chromatography analyses show that the increase in the concentration of SH - GSH is not only due to the production of phytochelatins, but is also due to an increase in the concentration of cysteine and the production of nonidentified thiols. The cysteine concentration increases equally in the roots of sensitive and tolerant plants. The accumulation of phytochelatins is higher in the roots of the sensitive plants, whereas the chain length distribution of phytochelatins is the same in sensitive and tolerant plants. It is concluded that increased zinc tolerance in S. vulgaris is not due to increased production of phytochelatins.

Journal ArticleDOI
TL;DR: It is concluded that zinc supplementation is effective for inducing growth in short children with zinc deficiency, and that body zinc clearance tests facilitate detection of marginal zinc deficiency.

Book ChapterDOI
01 Jan 1993
TL;DR: Zinc is a metallic element with atomic number 30 and stable isotopes of mass 66, 67, 68, and 70, averaging 65.38 a.m.u.m.
Abstract: Zinc is a metallic element with atomic number 30 and stable isotopes of mass 66, 67, 68, and 70, averaging 65.38 a.m.u. The terrestrial chemistry of Zn is that of Zn (II) rather than Zn(0). The Zn (II) ion has an electron configuration of 1s 2, 2s 2, 2p 6, 3d 10, and therefore lacks unfilled d subshells in the well-known oxidation state, the requisite criterion for true transition metals. Zinc(II) has an ionic radius comparable with Mg(II) but a Lewis acidity more like that of the smaller Cu(II) ion.

Journal ArticleDOI
TL;DR: In this paper, the James-Healy model for adsorption of hydrolyzed species, with the use of a single adjustable parameter, ΔGchem, for each cation, correctly predicted both the direction and magnitude of the temperature dependence of the pH range for adaption, but failed to account for its concentration dependence.

Journal ArticleDOI
TL;DR: In this paper, ultrathin zinc oxide (ZnO) films were grown on polycrystalline copper substrates via the sublimation of anhydrous zinc acetate (zn(CH3COO)2) in high vacuum (5 × 10−7mbar).