Showing papers on "Zinc published in 1981"
TL;DR: The research results reviewed here suggest that zinc plays an important role in the maintenance of membrane structure and function and physiological pathology is manifested rapidly after dietary zinc deprivation.
619 citations
568 citations
TL;DR: The concentrations of cadmium, zinc, copper and barium have been determined on 2-mg samples of single-species foraminifera populations Cleaning techniques were tested using North Atlantic core tops, and followed by a detailed downcore study for the last 30,000 years in South Atlantic core V22-174 as discussed by the authors.
372 citations
TL;DR: The possibility that intrinsic iron in formulas for feeding infants and in vitamin-mineral supplement might inhibit the absorption of zinc justifies concern about the Fe/Zn ratio in the formulation of these products.
298 citations
264 citations
TL;DR: In this article, a study of oxygen chemisorption at grain boundaries confirms the importance of grain boundary effects in ZnO polycrystalline films, which have a conductivity varying from 10−2 to 50 Ω−1 cm−1.
Abstract: Polycrystalline transparent semiconducting zinc oxide films have been deposited by the oxidation of diethyl zinc. The film growth rate is controlled by a complex multistep oxidation process which is dominated by radical reactions. The effect of substrate temperature and gas pressures have been studied. Samples deposited between 280 and 350 °C have a conductivity varying from 10−2 to 50 Ω−1 cm−1. The electrical properties of the films which are typical of polycrystalline material with small crystallites are shown to depend very closely on the film growth conditions. A study of oxygen chemisorption at grain boundaries confirms the importance of grain boundary effects in ZnO polycrystalline films.
245 citations
TL;DR: In this article, a kick-out model was proposed to explain the diffusion of Zn in GaAs which could not be satisfactorily explained in terms of a Frank-Turnbull mechanism involving vacancies can be understood with a ''kick-out'' model in which the equilibrium between interstitial and substitutional Zn is established via gallium interstitials.
Abstract: Experimental results on the diffusion of Zn in GaAs which could not be satisfactorily explained in terms of a Frank–Turnbull mechanism involving vacancies can be understood with a ’’kick‐out model’’ in which the equilibrium between interstitial and substitutional Zn is established via gallium interstitials.
221 citations
TL;DR: In this paper, the adsorption of Zn2+, Pb2+, Cu2+, Co2+, and Cd2+ (M2+) by soils was measured at concentrations ranging from 10-7 to 10-2 M in 10-3 to 10 -2 M CaCI2.
Abstract: Summary
The adsorption of Zn2+, Pb2+, Cu2+, Co2+, and Cd2+ (M2+) by soils was measured at concentrations ranging from 10-7 to 10-2 M in 10-3 to 10-2 M CaCI2. Exchange between Ca2+ and M2+, and solubility products [M2+][OH−]2 indicate that M2+ is not precipitated as hydroxide but is adsorbed on cation-exchange sites. The proportion of selective adsorption sites with specified values of the selectivity coefficient calculated using Ca as reference ion, increased in the order montmorillonite 10 000. The formation of the coordination complexes of heavy metal with deprotonoted OH and COOH groups as ligands is suggested as a possible mechanism of selective adsorption.
219 citations
TL;DR: Many factors other than the daily dietary phytate:zinc molar ratio influence zinc nutriture, but the ratio concept is a tool which may contribute to a more accurate assessment of zinc status.
Abstract: The phytate content of several foods is presented. Published zinc values were used to calculate phytate:zinc molar ratios. These ratios can be used to estimate the relative risk of having an inadequate intake of zinc. They may be used in planning menus to select the combination of foods that will supply the most available zinc to the daily diet. On the basis of animal experiments to date, a daily phytate:zinc molar ratio of 10 or less is thought to be acceptable in providing adequate dietary zinc, and daily ratios consistently above 20 may jeopardize zinc status. Many factors other than the daily dietary phytate:zinc molar ratio influence zinc nutriture, but the ratio concept is a tool which may contribute to a more accurate assessment of zinc status.
206 citations
TL;DR: A computer program (CHELATE) to calculate all equilibrium species (free metal ions, metal complexes, etc.) in any user-defined system, such as xylem fluid was used to calculate the distribution of six metals in 0- to 1-hour exudate from soybean and tomato plants grown in normal and Zn-phytotoxic nutrient solutions.
Abstract: Theoretical considerations of metal complex formation in aqueous solutions were used to develop a computer program (CHELATE) to calculate all equilibrium species (free metal ions, metal complexes, etc.) in any user-defined system, such as xylem fluid. Mass-balance equations were established to describe each free metal ion and each free ligand concentration as a function of solution pH, total metal or total ligand, hydrogen-association constants, and the stability constants of known metal complexes. A default data base can be altered by the user to define any desired system covered by the stored equilibrium data. The program can currently handle nine metal ions, 35 ligands, and 500 complex species. The validity of the program was confirmed by using experimental test systems in which free-metal ion activity measurements were made with ion-selective electrodes. Program CHELATE was used to calculate the distribution of six metals in 0- to 1-hour exudate from soybean ( Glycine max L. Merr.) and tomato ( Lycopersicon esculentum Mill.) plants grown in normal and Zn-phytotoxic nutrient solutions. The results indicated that Fe is bound by citric acid, and Cu is bound by several amino acids in the normal-Zn exudate. Most of the Cu in soybean exudate is bound to asparagine and histidine. In tomato, Cu is bound to histidine, glutamine, and asparagine. Zinc, Mn, Ca, and Mg are bound primarily by citric acid and malic acid in both species; the per cent bound for these metals is lower than that for Fe and Cu. Zinc phytotoxicity caused equilibrium concentration shifts and resulted in the formation of several additional metal complexes not found in the normal-Zn exudate.
191 citations
TL;DR: It is suggested that limitation of lean tissue synthesis, with resultant obesity, and a propensity to infection are the major features of a mild zinc deficiency.
TL;DR: The simplicity of the resolved thiolate spectra and their correspondence to those of tetrahedral models support the view that the various metal-binding sites of metallothionein are chemically similar and that the coordination environment of the metal ion has a symmetry related to that of a tetrahedron.
Abstract: The metal-specific absorption envelopes of zinc-, cadmium-, and mercury-metallothioneins and of complexes of these metal ions with 2-mercaptoethanol have been analyzed in terms of Jorgensen's electronegativity theory for charge-transfer excitations by using the spectra of zinc(II), cadmium(II), and mercury(II) tetrahalides as references. By Gaussian analysis the difference absorption spectra of the various forms of metallothionein vs. thionein and of the corresponding 2-mercaptoethanol complexes vs. 2-mercaptoethanol were resolved into three components. For each metal derivative the location of the lowest energy band is in good agreement with the position of the first ligand-metal charge-transfer (LMCT) transition (type t2 leads to a1) predicted from the optical electronegativity difference of the thiolate ligands and of the central metal ion by assuming tetrahedral coordination. There is also a correspondence between the effects of the metal ion on the position of the first LMCT band and the binding energy of the 2p electrons of the sulfur ligands as found by X-ray photoelectron spectroscopic measurements [Sokolowski, G., Pilz, W., & Weser, U. (1974) FEBS Lett. 48, 222]. Due to the lack of exact structural information, the assignment of the two other resolved metal-dependent bands remains conjectural, but it is likely that they include a second LMCT transition (type t2 leads to a1) analogous to that occurring in tetrahalide complexes of group-2B metal ions. The simplicity of the resolved thiolate spectra and their correspondence to those of tetrahedral models support the view that the various metal-binding sites of metallothionein are chemically similar and that the coordination environment of the metal ion has a symmetry related to that of a tetrahedron [Vasak, M. (1980) J. Am. Chem. Soc. 102, 3953].
TL;DR: The content of zinc in peripheral-blood leucocytes decreased from the second trimester of normal pregnancy, but was significantly lower in mothers giving birth to babies who were small for gestational age than in mothers with either normal or small, but appropriate for gestations, preterm babies.
TL;DR: This paper focuses on Trace Element Concentrations during Lactation, and the role of zinc, copper, and Manganese in the concentration of these elements in milk.
Abstract: INTRODUCTION . METHODOLOGY IN ANALYSIS OF MILK . Sample Collection . Methods of Estimating Milk Output . Analytical Techniques . DEVELOPMENTAL CHANGES IN TRACE ELEMENT CONCENTRATIONS DURING LACTATION . Patterns of Trace Element Concentrations During Lactation . Iron . Copper . Zinc •.•...• ••.•.• •.•........•...••.• ••• ••• •..•....... Manganese . DIETARY INFLUENCE ON MILK COMPOSITION-EFFECTS OF MATERNAL TRACE ELEMENT DEFICIENCY OR EXCESS ......... . Iran . Copper . Zinc . Manganese . Comments . TRACE ELEMENT BINDING FACTORS IN MILK . Iran . Zinc . Copper . Manganese . Comments . BIOA V AILABILITY OF TRACE ELEMENTS IN MILK .. Iran . Zinc . Copper and Manganese . INFANT FORMULAS .. CONCLUDING REMARKS .
TL;DR: In this article, Corrosion resistant ZnCo alloys were electrodeposited on the steel sheet cathode from an acid galvanizing bath containing a small amount of cobalt sulfate.
Abstract: Corrosion resistant Zn‐Co alloys were electrodeposited on the steel sheet cathode from an acid galvanizing bath containing a small amount of cobalt sulfate. Under most of the plating conditions studied, the anomalous codeposition and, hence, the preferential deposition of electrochemically less noble Zn occurred. The electrodeposition process of the alloy including the Zn hydroxide formation resulting from the rise in pH in the vicinity of the cathode was estimated by electrochemical and spectroscopic studies.
TL;DR: The data suggest that zinc exerts its antagonistic effect by inducing the synthesis of a copper-binding ligand, probably a thionein, in the mucosal cells which sequesters copper from the nutrient medium, making it unavailable for serosal transfer.
TL;DR: Rueter and Morel as mentioned in this paper found a competitive relationship between cupric ion activity and silicic acid concentration as they affect growth, silic acid uptake, and copper uptake in the marine diatom Thalassiosira pseudonana (3H) (Hust.)
Abstract: Zinc-deficient cultures of Thalassiosira pseudonana exhibited reduced silicic acid uptake rates. Copper toxicity decreased the silicic acid uptake rate at any zinc concentration. This resulted in the uptake rate being a function of the ratio in the medium of the cupric ion activity to the zinc activity rather than of either metal activity separately. These results are consistent with a proposed mechanism for the interaction between silicic acid and cupric ion activity involving a zinc-dependent active site. In work to be published elsewhere (Rueter and Morel in prep.) we found a competitive relationship between cupric ion activity and silicic acid concentration as they affect growth, silicic acid uptake, and copper uptake in the marine diatom Thalassiosira pseudonana (3H) (Hust.) Hasle and Heimdal. The result of this competitive interaction was that relatively high cupric ion activities resulted in higher rates of copper uptake and lower rates of silicic acid uptake. Conversely, high silicic acid concentrations could reverse the effect of copper toxicity, causing lower copper uptake rates and near maximal silicic acid uptake rates. We have considered a mechanism for this interaction in which an active site for silicic acid uptake is inhibited by the cupric ion activity and protected by high substrate (silicic acid) concentrations. This form of inhibition is similar to nonreversible competitive binding to the active site that has been studied in other enzyme systems (Zeffren and Hall 1973). We also thought that the binding of copper at this active site was one possible pathway for copper to enter the cell. In order to explain this proposed mechanism, we considered that zinc could be involved in silicic acid uptake. Zinc was
TL;DR: Dementia may represent the cascading effects, equivalent to an Orgel error catastrophe, of error-prone or ineffective DNA-handling enzymes in neurons which have an age-associated loss of ability to make zinc available for insertion into newly synthesised enzyme.
TL;DR: In this article, a white, non-crystalline precipitate is formed in the heated oils which is rich in zinc and oxygen and low in phosphorus and sulfur compared with the original ZDTP.
Abstract: The oil-soluble degradation products formed in heated samples of oil containing zinc di(n-, iso- or s-butyl)dithiophosphate (ZDTP) additives have been identified using 1H and 31P nuclear magnetic resonance spectroscopy. The final degradation product in each case is S,S,S-trialkyltetrathiophosphate, SP(SR)3. The intermediate degradation products are O,S,S-trialkyltrithiophosphate, SP(SR)2(OR) and O,O,S-trialkyldithiophosphate, SP(SR)(OR)2. The rate of thermal degradation of the ZDTPs follows the order s-butyl > > n-butyl > isobutyl. A white, noncrystalline precipitate is formed in the heated oils which is rich in zinc and oxygen and low in phosphorus and sulfur compared with the original ZDTP. In four-ball tests, synthesized degradation products were shown to have EP activity comparable with that of the ZDTP additives. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Dayton, Ohio, October 16–18, 1979
TL;DR: A trace-metal supplement for L. pneumophila was designed which included all metals stimulating growth in these experiments and which proved to be sufficient for optimal growth of all the strains.
Abstract: Serial passage of six strains of Legionella pneumophila and one strain of Pseudomonas aeruginosa in a liquid chemically defined medium deficient in trace metals resulted in the death of five L pneumophila strains and very limited growth in the remaining strain and the P aeruginosa strain Addition of either iron or magnesium restored growth to almost normal levels in all of the strains when early-passage inocula were used A low concentration of magnesium stimulated growth with cobalt, copper, iron, manganese, molybdenum, vanadium, or zinc When a complete defined medium containing trace metals was used, growth was inhibited by adding the chelators ethylenediaminetetraacetic acid, citrate, or 2,2'-bipyridyl Chelator inhibition was partly or fully relieved with either calcium, cobalt, copper, iron, magnesium, molybdenum, nickel, vanadium, or zinc P aeruginosa differed from L pneumophila in that it required higher concentrations of each chelator to inhibit growth and that its growth was stimulated by only four metals: calcium, iron, magnesium, and zinc A trace-metal supplement for L pneumophila was designed which included all metals stimulating growth in these experiments and which proved to be sufficient for optimal growth of all the strains
TL;DR: In this article, the 0.05M HCl method was compared with EDTA, DTPA, EDTA and DTPA as an extractant for available zinc and copper.
Abstract: Because zinc deficiency is a widespread disorder of wetland rice and copper deficiency may occur with it, 0.05M HCl was compared with 0.1M HCl, EDTA and DTPA as an extractant for available zinc and copper. It was also compared with the reflux method for boron assay. Thirty-three wetland rice soils were analyzed for zinc and copper by the four methods. Rice was grown on the flooded soils, scored visually for zinc deficiency, and the plants analyzed for zinc and copper content. In the boron study, 53 soils were extracted by the reflux method and the 0.05M HCl procedure. Rice was grown on the flooded soils, scored visually for boron toxicity, and the plants analyzed for boron content. Fourteen of the 16 soils on which rice showed zinc deficiency gave <1.0 mg/kg Zn by the 0.05M HCl method but values far in excess of the critical limits by the other methods. The r values for available and plant zinc were: 0.05M HCl (0.88**); 0.1M HCl (0.55**); EDTA (0.43**); and DTPA (0.31ns). Twelve of the zinc-deficient soils gave<0.1 mg/kg Cu by the 0.05M HCl method but values exceeding the critical limits by the EDTA and DTPA methods. The r values for available and plant copper were: 0.05M HCl (0.74**), 0.1M HCl (0.64**), EDTA (0.28ns), and DTPA (0.20ns). The critical limit of 1.0 mg/kg by the 0.05M HCl extraction was confirmed for zinc deficiency and a tentative value of 0.1 mg/kg for copper deficiency proposed. The 0.05M HCl method separated boron-toxic soils from non-toxic soils and gave a better correlation (r=0.91**) between available and plant boron than the reflux extraction (r=0.84**). The toxic limit by the 0.05M HCl method was provisionally set at 4 mg/kg.
TL;DR: In this paper, the ZnO smoke particles prepared by burning zinc metal in a gas mixture of 80% Ar and 20% O2 at a total pressure of 100 Torr were studied by electron microscopy.
TL;DR: Photosystem I (PSI) associated electron transport 2,6-dichlorophenol indophenol (DCPIP)red → methyl viologen (MV) → O2, in contrast to total photosynthetic capacity, was only slightly inhibited by Zn, Cd and Hg, whereas the levels of activity of NADP-oxidoreductase in cells untreated or treated with heavy metals showed development like total photosynthesis.
Abstract: Results on the effect of sub-lethal concentrations of zinc chloride (ZnCl2), cadmium chloride (CdCl2), and mercuric chloride (HgCl2) on Euglena are presented. During the growth cycle respiratory oxygen uptake and photosynthetic oxygen evolution in the light are initially strongly inhibited by Zn, Cd and Hg. The effects of the three metals on photosynthesis, using oxygen evolution as a criterion was confirmed by carbon fixation techniques. Photosystem I (PSI) associated electron transport 2,6-dichlorophenol indophenol (DCPIP)red. → methyl viologen (MV) → O2, in contrast to total photosynthetic capacity, was only slightly inhibited by Zn, Cd and Hg, whereas the levels of activity of NADP-oxidoreductase in cells untreated or treated with heavy metals showed development like total photosynthesis. Metals strongly inhibited this enzyme which means that the supply of NADPH is lowered due to the action of Zn, Cd and Hg. Photosystem II (PSII) associated electron transport (H2O → dibromothymoquinone/2,3-dimethyl-5,6-methylenedioxy-D-benzoquinone → O2), however, was severely inhibited in a way similar to total photosynthesis. Effects on the cooperation of PSI + II showed patterns similar to PSII alone, i.e., heavy metals strongly reduced PSI + II dependent activities.
TL;DR: The response of circulating T-lymphocytes to phytohemagglutinin was assessed both during the episode of clinical zinc deficiency and after intravenous zinc supplementation as the sole means of nutritional intervention, showing the detrimental effect of zinc deficiency on cellular immunity.
Abstract: Two patients developed severe zinc deficiency with acrodermatitis during parenteral hyperalimentation. The response of circulating T-lymphocytes to phytohemagglutinin was assessed both during the episode of clinical zinc deficiency and after intravenous zinc supplementation as the sole means of nutritional intervention. Maximum T-cell response to phytohemagglutinin, expressed as percent of simultaneous normal control response, was 2.1% and 27.9% in Patients 1 and 2 respectively. After 20 days of intravenous zinc supplementation (12 mg/d), repeat studies showed the T-cell response of Patient 1 to be 221% of the control, and that of Patient 2 to be 139% of control. In addition, Patient 1 was anergic during the period of zinc deficiency and normally reactive after zinc supplementation. These findings agree with extensive animal studies showing the detrimental effect of zinc deficiency on cellular immunity.
TL;DR: In this paper, the reformatsky reaction, the Grignard reaction, and cyclopropanation with dibromomethane are described, as well as applications to the reformatization of metal powders.
Abstract: Highly reactive zinc and magnesium metal powders can be prepared by the lithium reduction of the corresponding metal salt with a catalytic amount of naphthalene as an electron carrier. Applications to the Reformatsky reaction, the Grignard reaction, and cyclopropanation (with dibromomethane) are described.
TL;DR: In this article, the rotating ring disk electrode has been applied to the related phenomena of dissolution, current oscillation, and passivation of zinc in concentrated aqueous, and a physical model was proposed to describe the anodic behavior of zinc.
Abstract: The rotating ring‐disk electrode has been applied in this study to the related phenomena of dissolution, current oscillation, and passivation of zinc in concentrated aqueous . The results of potentiostatic and potentiodynamic experiments are compared with those of previous workers, and a physical model is proposed to describe the anodic behavior of zinc in four successive potential regions: active dissolution, prepassivation, pseudopassivation, and true passivation.
TL;DR: Pair-feeding copper, zinc, iron and manganese to diabetic and control groups demonstrated that the enhanced food consumption of the diabetic rat was not a significant factor in the observed accumulation of trace metals in liver and kidney.
Abstract: An insulin-dependent diabetic condition was induced in male Sprague-Dawley rats by streptozotocin injection. Ten days after administration of the diabetogenic drug, tissue levels of copper, zinc, iron and manganese were determined and compared to control animals. Increased quantities of hepatic copper, zinc and manganese, renal copper and zinc and plasma zinc were observed in the diabetic group. Intestinal, muscle and spleen contents of the metals were similar in control and diabetic rats. Elevated levels of zinc- and copper-metallothionein were found in liver and kidney of diabetic rats. The distribution of zinc among soluble proteins in the diabetic liver was also content of tissues, intracellular distribution of zinc and the quantity of zinc-and copper-metallothionein to normal levels. Pair-feeding copper, zinc, iron and manganese to diabetic and control groups demonstrated that the enhanced food consumption of the diabetic rat was not a significant factor in the observed accumulation of trace metals in liver and kidney. These data suggest that the hormonal imbalance characteristic of the insulin-dependent diabetic condition influences trace metal metabolism. These studies also demonstrate the usefulness of the streptozotocin-diabetic rat as an animal model for investigations concerning hormone-mediated regulation of trace metal metabolism.
TL;DR: In this paper, the ability of a model to describe quantitatively the adsorption of copper, lead and zinc on goethite was tested, and the model was able to describe both the increase in adhesion of metals with increasing pH and the release of protons that accompanied adhesion.
Abstract: The ability of a model to describe quantitatively the adsorption of copper, lead and zinc on goethite was tested. The model was able to describe both the increase in adsorption of metals with increasing pH and the release of protons that accompanied adsorption. For copper and zinc, MeOH+ were the adsorbing species. Part of the increase in adsorption with increasing pH arose because these ions increase in concentration with pH. For lead, Pb2+ ions appeared to be adsorbed, and in this case the increase in adsorption with pH was entirely due to the decreased charge on the surface and thus decreased repulsion. For all three metals, the MeCl+ ions also appeared to be adsorbed, and this explained higher adsorption from chloride solution than from nitrate solutions. The observed release of protons accompanying adsorption was matched by moving the plane of adsorption of metal ions relative to that of the H+ and OH- ions. When the two planes were close, the proton release was almost equivalent to the charge on the metal ions; as the distance increased, proton release decreased.