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Showing papers on "Zinc toxicity published in 2006"


Journal ArticleDOI
TL;DR: A multidisciplinary approach will most likely result in success in the pharmacology of zinc compounds as a promising area for translational research, and the current assumed range between safe and unsafe intakes of zinc is relatively narrow.

920 citations


Journal ArticleDOI
TL;DR: Physiological supplementation of Zn in ageing and in age-related degenerative diseases corrects immune defects, reduces infection relapse and prevents ageing.
Abstract: Zinc (Zn) is one of the most important trace elements in the body and it is essential as a catalytic, structural and regulatory ion. It is involved in homeostasis, in immune responses, in oxidative stress, in apoptosis and in ageing. Zinc-binding proteins (metallothioneins, MTs), are protective in situations of stress and in situations of exposure to toxic metals, infections and low Zn nutrition. Metallothioneins play a key role in Zn-related cell homeostasis due to their high affinity for Zn, which is in turn relevant against oxidative stress and immune responses, including natural killer (NK) cell activity and ageing, since NK activity and Zn ion bioavailability decrease in ageing. Physiological supplementation of Zn in ageing and in age-related degenerative diseases corrects immune defects, reduces infection relapse and prevents ageing. Zinc is not stored in the body and excess intakes result in reduced absorption and increased excretion. Nevertheless, there are cases of acute and chronic Zn poisoning.

384 citations


Journal ArticleDOI
TL;DR: A need exists to develop in situ low cost technologies to effect surface stabilization of mine tailings from a semiarid mining zone in Southeast Spain, since there are some native plant species that can colonize parts of these polluted sites unaided.

305 citations


Journal ArticleDOI
TL;DR: It is concluded that severe renal damage could occur in the N-Zn treated mice, though no significant change of blood biochemical levels occurred, which indicated that N- Zn powder could cause severe anemia.

281 citations


Journal ArticleDOI
Mei Li1, Changwei Hu1, Qin Zhu1, Li Chen1, Zhiming Kong1, Zhili Liu1 
TL;DR: Results suggest that an activation of some antioxidant enzymes was enhanced to counteract the oxidative stress induced by the two metals.

239 citations


Journal ArticleDOI
TL;DR: Comparison of relative tolerance capacities of transgenic plants, overexpressing either glyoxalase I or II individually or together in double transgenics, evaluated in terms of various critical parameters such as survival, growth, and yield, reflected double trans genics to perform better than either of the single-gene transformants.
Abstract: We reported earlier that engineering of the glyoxalase pathway (a two-step reaction mediated through glyoxalase I and II enzymes) enhances salinity tolerance. Here we report the extended suitability of this engineering strategy for improved heavy-metal tolerance in transgenic tobacco (Nicotiana tabacum). The glyoxalase transgenics were able to grow, flower, and set normal viable seeds in the presence of 5 mm ZnCl2 without any yield penalty. The endogenous ion content measurements revealed roots to be the major sink for excess zinc accumulation, with negligible amounts in seeds in transgenic plants. Preliminary observations suggest that glyoxalase overexpression could confer tolerance to other heavy metals, such as cadmium or lead. Comparison of relative tolerance capacities of transgenic plants, overexpressing either glyoxalase I or II individually or together in double transgenics, evaluated in terms of various critical parameters such as survival, growth, and yield, reflected double transgenics to perform better than either of the single-gene transformants. Biochemical investigations indicated restricted methylglyoxal accumulation and less lipid peroxidation under high zinc conditions in transgenic plants. Studies employing the glutathione biosynthetic inhibitor, buthionine sulfoximine, suggested an increase in the level of phytochelatins and maintenance of glutathione homeostasis in transgenic plants during exposure to excess zinc as the possible mechanism behind this tolerance. Together, these findings presents a novel strategy to develop multiple stress tolerance via glyoxalase pathway engineering, thus implicating its potential use in engineering agriculturally important crop plants to grow on rapidly deteriorating lands with multiple unfavorable edaphic factors.

237 citations


Journal ArticleDOI
TL;DR: The role and manifestations of zinc in the environment and its importance for human health and metabolism, as well as its physiological role are summarized.
Abstract: Zinc is a common element in human and natural environments and plays an important part in many biological processes. Zinc, which is defined as an essential trace element, or a micronutrient, is essential for the normal growth and the reproduction of all higher plants and animals, and of humans. In addition, it plays a key role during physiological growth and fulfills an immune function. It is vital for the functionality of more than 300 enzymes, for the stabilization of DNA, and for gene expression. This review summarizes the role and manifestations of zinc in the environment and its importance for human health and metabolism, as well as its physiological role. Toxicity, teratogenicity, carcinogenicity, and immunological functions of zinc are outlined with particular reference to the properties of zinc as an antioxidant, and its role in cancer prevention.

231 citations


Journal ArticleDOI
TL;DR: Findings suggest that the algal cell surface may be considered as the biotic ligand in further development of a chronic BLM with microalgae as well as the possibility of using concentration-response data to estimate conditional metal-cell binding constants.
Abstract: Copper and zinc toxicity to the freshwater alga Chlorella sp. was determined at a range of pH values (5.5-8.0) in a synthetic softwater (hardness 40-48 mg CaCO(3)/L). The effects of the metals on algal growth (cell division) rate were determined after 48-h exposure at pH 5.5, 6.0, 6.5, 7.0, 7.5, and 8.0. The toxicity of both metals was pH dependent. As pH decreased from 8.0 to 5.5, the copper concentration required to inhibit the algal growth rate by 50% (IC50) increased from 1.0 to 19 microg/L. For zinc, the IC50 increased from 52 to 2,700 microg/L over the same pH range. Changes in solution speciation alone did not explain the increased toxicity observed as the pH increased. Modelled Cu(2+) and Zn(2+) concentrations decreased with increasing pH, whereas toxicity was observed to increase. Measurements of extracellular (cell-bound) metal concentrations support the biotic ligand model (BLM) theory of competition between protons (H(+)) and metals for binding sites at the algal cell surface. Higher extracellular metal concentrations were observed at high pH, indicating reduced competition. Independent of pH, both extracellular and intracellular copper were directly related to growth inhibition in Chlorella sp., whereas zinc toxicity was related to cell-bound zinc only. These findings suggest that the algal cell surface may be considered as the biotic ligand in further development of a chronic BLM with microalgae. Conditional binding constants (log K) were determined experimentally (using measured intracellular metal concentrations) and theoretically (using concentration-response curves) for copper and zinc for Chlorella sp. at selected pH values. Excellent agreement was found indicating the possibility of using concentration-response data to estimate conditional metal-cell binding constants.

174 citations


Journal ArticleDOI
TL;DR: In order to gain better insights in the integrated response of Daphnia magna following chronic zinc exposure, several physiological parameters were measured in a time-dependent manner.

173 citations


Journal ArticleDOI
TL;DR: The effect of humic acids (HAs) on the toxicity of copper, zinc, and lead was investigated using the photobacterium Vibrio fischeri (Microtox test) as a test organism and the effects of HAs on metal toxicity were evaluated as functions of time and concentration in pure compound solutions.

121 citations


Journal ArticleDOI
TL;DR: Collectively, these studies suggest that D. magna may not be representative of other cladocerans and that cadmium and zinc effects presented individually and in combination on Ceriodaphnia dubia, Daphnia magna,Daphnia ambigua, and Daphnian pulex are suggest to be less-than-additive.
Abstract: Investigations were conducted to determine acute (48-h) effects of cadmium and zinc presented individually and in combination on Ceriodaphnia dubia, Daphnia magna, Daphnia ambigua, and Daphnia pulex. Toxicity tests were conducted with single metals to determine lethal effects concentrations (lethal concentrations predicted for a given percent [x] of a population, LCx value). These were used to derive metal combinations that spanned a range of effects and included mixtures of LC15, LC50, and LC85 values calculated for each metal and species. In single-metal tests, 48-h LC50 values ranged from 0.09 to 0.9 micromol/L and 4 to 12.54 micromol/L for cadmium and zinc, respectively. For each metal, D. magna was most tolerant and showed a different pattern of response from all others as determined by slope of concentration-response curves. In the combined metal treatments, all daphnids showed a similar pattern of response when LC15 concentrations were combined. This trend continued with few exceptions when LC15 concentrations of cadmium were combined with LC50 or LC85 values for zinc. However, when this treatment was reversed (LC15, zinc + LC50 or LC85, cadmium), responses of all species except D. magna indicated less-than-additive effects. For C. dubia, a near complete reduction in toxicity was observed when the LC15 for zinc was combined with LC85 for cadmium. Multimetal tests with D. magna did not differ from additive. Collectively, these studies suggest that D. magna may not be representative of other cladocerans.

Journal ArticleDOI
TL;DR: The toxicity of three heavy metals on an activated sludge biomass was studied by measuring several parameters of microbiological activity and the dynamics of microbial community composition, which suggested a higher sensitivity of nitrifiers to these metals than heterotrophs.

Journal ArticleDOI
TL;DR: The results indicate that zinc toxicity -- at higher levels -- may be connected to a strong inhibition of GR activity, and related to the pro-oxidative state found.

Journal ArticleDOI
TL;DR: First zoeae were more sensitive than young crabs to acute exposure to all metals analyzed and mixed toxicity tests carried out on first-stage larvae showed different kinds of interactions.

Journal ArticleDOI
TL;DR: The correlation between experimental zinc dose, zinc contents in the brain and DNA damage in neuroblasts, and zinc concentration remained at the control level, which may be the basis for further searching for molecular mechanisms of defense against heavy metals in insects living in polluted habitats.
Abstract: The distribution and concentration of selected elements by PIXE method and DNA damage using comet assay in brains of 1st instars of grasshoppers Chorthippus brunneus from unpolluted (Pilica) and polluted (Olkusz) site, additionally exposed to various doses of zinc during diapause or after hatching, were measured. We tried to assess the degree of possible pre-adaptation of the insects to heavy metals and evaluate the utility of these parameters in estimation of insect exposure to industrial pollutants. Additionally, the mechanism of zinc toxicity for grasshopper brains was discussed. We observed the correlation between experimental zinc dose, zinc contents in the brain and DNA damage in neuroblasts, but only in groups exposed to lower zinc concentration. For higher zinc concentration the amount of the metal in brain and DNA damage remained at the control level. Some site-related differences in DNA damage between grasshoppers from Pilica and Olkusz were observed during short-term exposure (after hatching). Significant increase in the calcium contents in the brain, proportional to zinc concentration in sand, was also observed, especially in the offsprings from Olkusz. The results may be the basis for further searching for molecular mechanisms of defense against heavy metals in insects living in polluted habitats.

Journal ArticleDOI
TL;DR: Evidence indicates that the most sensitive parameter of metal toxicity for animals living in a chronically contaminated environment is the GSH/GSSG ratio, which was decreased in the liver of animals with high Cd levels.

Journal ArticleDOI
TL;DR: The data indicate that not only low level of zinc, but also high levels of zinc decrease Th1 function, as higher concentration of zinc adversely affects T-cell immune response.

Journal ArticleDOI
TL;DR: It is concluded that metal uptake in fish is not related to its ventilation rate within a normal physiological range, and observed uptake rates are considerably lower than predicted from a ventilation-and-diffusion-regulated uptake mechanism.
Abstract: Zinc is an essential micronutrient that becomes toxic at elevated concentrations. Under hypoxic events, i.e., temporal depletion of oxygen, the toxicity of Zn increases for fish, apart from the direct effects of the reduced oxygen levels. This enhanced toxicity currently is explained by the increased ventilation rates under hypoxia, causing a higher water flow over the gills. However, the few experimental studies available on the uptake of heavy metals under hypoxia draw contradictory conclusions. The present study verifies the enhanced zinc toxicity under hypoxia and tests whether accumulation of zinc is increased in common carp, Cyprinus carpio (L.). Second, the effect of acclimatization to three oxygen levels (100, 50, and 25% saturation) on the zinc uptake and elimination was studied in a standard radiotracer uptake-and-elimination study for 63 d at 100 nmol/L Zn and 25°C. The sensitivity of carp for Zn was threefold higher under hypoxia than at normoxic conditions. The lethal concentration for 50% of the population after 96 h (96-h LC50) for normoxia and hypoxia (25%) were 149 (91–317) and 55 (30–100) μmol/L Zn, respectively. However, the kinetic data indicate that zinc uptake and elimination are not altered under hypoxia for common carp. Moreover, observed uptake rates are considerably lower than predicted from a ventilation-and-diffusion–regulated uptake mechanism. Setting these results in the framework of similar experiments of other investigators, we conclude that, in general, metal uptake in fish is not related to its ventilation rate within a normal physiological range.

Journal ArticleDOI
TL;DR: Three QTLs for Zn 2+ toxicity tolerance were detected on chromosomes 1, 3 and 10 and explained 21.9, 8.9 and 7.6%, respectively, of the total phenotypic variation.

Journal ArticleDOI
TL;DR: Homeostatic crosstalk between the plasma membrane and intracellular zinc transporters is demonstrated and it is suggested that attenuating zinc influx may enhance β-cell survival.

Journal ArticleDOI
TL;DR: It is concluded that the interactions between elevated dietary Ca2+ and waterborne zinc can protect freshwater fish against waterborne arsenic toxicity and acute zinc tolerance relative to control.
Abstract: This study investigated the effects of dietary Ca2+ on branchial Ca2+ and Zn2+ uptake, new and total zinc accumulation in target tissues (gill, liver and kidney), calcium and zinc homeostasis, and acute tolerance to waterborne zinc in fish chronically exposed to waterborne zinc. Juvenile rainbow trout (Oncorhynchus mykiss) were maintained on a calcium-enriched diet [41.2 mg vs. 21.2 mg (control) calcium/g dry wt. of food] and chronic waterborne zinc exposure (2.3 μmol/L), both separately and in combination, for 28 days. Calcium-supplemented diet in the absence of waterborne zinc significantly reduced branchial Ca2+ and Zn2+ influx rates, and new and total zinc accumulations in target tissues relative to control. However it did not protect against the acute zinc challenge. In contrast, waterborne zinc exposure significantly increased branchial Ca2+ and Zn2+ influx rates, new and total zinc concentrations in target tissues, and acute zinc tolerance relative to control. Interestingly, no such changes in any of these parameters were recorded in fish treated simultaneously with elevated dietary Ca2+ and waterborne zinc, except acute zinc tolerance which was highest among all the treatments. Thus, we conclude that the interactions between elevated dietary Ca2+ and waterborne zinc can protect freshwater fish against waterborne zinc toxicity.

Journal ArticleDOI
TL;DR: The result of the in vitro study indicated that the bacterial strains are sensitive to Zn 2+ stress, and Zn 1+ contamination would pose serious threat to their metabolism in natural environments.
Abstract: Toxicity of Zn 2+ on four planktonic bacteria isolated from New Calabar River water was assessed via dehydrogenase assay. Pure cultures of the bacterial strains were exposed to various Zn 2+ concentrations (0.2 - 2.0 mM) in a nutrient broth amended with glucose and TTC. The responses of the bacterial strains to Zn 2+ is concentration-dependent. At 0.2 mM, Zn 2+ stimulated dehydrogenase activity in Proteus sp. PLK2 and Micrococcus sp. PLK4. In all strains, dehydrogenase activity was progressively inhibited at concentrations greater than 0.2 mM. The IC 50 ranges from 0.236 ± 0.044 to 0.864 ± 0.138 mM. Total inhibition occurred at concentrations ranging from 1.283 ± 0.068 to 2.469 ± 0.045 mM. The order of zinc tolerance is: Micrococcus sp. PLK4 > Proteus sp. PLK2 > Pseudomonas sp. PLK5 > Escherichia sp. PLK1. The result of the in vitro study indicated that the bacterial strains are sensitive to Zn 2+ stress. Therefore, Zn 2+ contamination would pose serious threat to their metabolism in natural environments. Key words: New Calabar River, zinc toxicity, planktonic bacteria, dehydrogenase.

Journal ArticleDOI
TL;DR: The current composite-species BLM for Zn could be improved for fathead minnows if that species were modeled separately from the other species used to calibrate Version 2.1.1 of the Zn BLM.
Abstract: We conducted laboratory toxicity tests in support of the development of a biotic ligand model (BLM) to predict acute toxicity of zinc (Zn) to fathead minnows (Pimephales promelas). To test the effect of dissolved organic matter (DOM) on Zn toxicity, we exposed larval fathead minnows to Zn in water containing elevated concentrations of dissolved organic carbon (DOC) in 96-h static-renewal toxicity tests. We tested DOM isolated from four surface waters: Cypress Swamp, Delaware; Edisto River, South Carolina; Suwannee River, Georgia; and Wilmington, Delaware, wastewater treatment effluent. The DOM isolates from the Edisto River and Wilmington wastewater treatment effluent contained elevated concentrations of NaCl (20-110x control NaCl) due to the use of a Na+-exchange resin to remove Ca2+ and Mg2+ during the DOM isolation process. Therefore, we also performed Zn toxicity tests in which we added up to 20 mM NaCl to exposure solutions containing Cypress Swamp and Suwannee River DOM. A threshold concentration of 11 mg DOC/L was needed to decrease Zn toxicity, after which the 96 h Zn LC50 was positively correlated with DOC concentration. Elevated NaCl concentrations did not alter Zn toxicity in the presence of DOM. In conjunction with data from other studies with fish and invertebrates, results of this study were used to calibrate Version 2.1.1 of the Zn BLM. BLM-predicted LC50s for our exposure waters containing elevated DOM concentrations were within the range of acceptable deviation relative to the observed LC50s (i.e., 0.5-2x observed LC50s); however, BLM-predicted LC50s for our exposure waters containing < 1 mg DOC/L were 2-3x lower than the observed LC50s (i.e., the BLM over-predicted the toxicity). Therefore, the current composite-species BLM for Zn could be improved for fathead minnows if that species were modeled separately from the other species used to calibrate Version 2.1.1.

Journal ArticleDOI
TL;DR: This study evaluated the performance of a Hormosira banksii germination inhibition bioassay developed to assess the toxicity of single compounds and complex effluents in the Australasian region using four reference toxicants.


Journal ArticleDOI
TL;DR: The present results suggest that a Raf-1/MEK/ERK1/2 pathway and the ERK substrate Elk-1 are involved in free radical-induced injury in rat renal cortical slices exposed to zinc.
Abstract: Zinc is an essential nutrient that can also be toxic. We have previously reported that zinc-related renal toxicity is due, in part, to free radical generation in the renal epithelial cell line, LLC-PK(1) cells. We have also shown that an MEK1/2 inhibitor, U0126, markedly inhibits zinc-induced renal cell injury. In this study, we investigated the role of an upstream MEK/ERK pathway, Raf-1 kinase pathway, and the transcription factor and ERK substrate Elk-1, in rat renal cortical slices exposed to zinc. Immediately after preparing slices from rat renal cortex, the slices were incubated in medium containing Raf-1 and MEK inhibitors. ERK1/2 and Elk-1 activation were determined by Western blot analysis for phosphorylated ERK (pERK) 1/2 and phosphorylated Elk-1 (pElk-1) in nuclear fractions prepared from slices exposed to zinc. Zinc caused not only increases in 4-hydroxynonenal (4-HNE) modified protein and lipid peroxidation, as an index of oxidant stress, and decreases in PAH accumulation, as that of renal cell injury in the slices. Zinc also induced a rapid increase in ERK/Elk-1 activity accompanied by increased expressions of pERK and pElk-1 in the nuclear fraction. A Raf-1 kinase inhibitor and an MEK1/2 inhibitor U0126 significantly attenuated zinc-induced decreases PAH accumulation in the slices. The Raf-1 kinase inhibitor and U0126 also suppressed ERK1/2 activation in nuclear fractions prepared from slices treated with zinc. The present results suggest that a Raf-1/MEK/ERK1/2 pathway and the ERK substrate Elk-1 are involved in free radical-induced injury in rat renal cortical slices exposed to zinc.

Journal ArticleDOI
TL;DR: In this paper, the effects of zinc and manganese on the reductive dissolution of hematite by the dissimilatory metal-reducing bacterium (DMRB) Shewanella putrefaciens CN32 were studied in batch culture.
Abstract: The effects of zinc and manganese on the reductive dissolution of hematite by the dissimilatory metal-reducing bacterium (DMRB) Shewanella putrefaciens CN32 were studied in batch culture. Experiments were conducted with hematite (2.0 g L–1) in 10 mM PIPES (pH 6.8), and H2 as the electron donor under nongrowth conditions (108 cell mL–1), spiked with zinc (0.02–0.23 mM) or manganese (0.02–1.8 mM) and incubated for 5 days. Zinc inhibition was calculated based on the 5-day extent of hematite bioreduction in the absence and presence of zinc. Zinc inhibition of hematite bioreduction increased with anthraquinone- 2,6-disulfonate (AQDS), a soluble electron shuttling agent, and ferrozine, a strong Fe(II) complexant. Both amendments would otherwise stimulate hematite bioreduction. These amendments did not significantly increase zinc sorption, but may have increased zinc toxicity by some unknown mechanism. At equal total Me(II) concentrations, zinc inhibited hematite reduction more than manganese and caused greater ...

Journal ArticleDOI
TL;DR: In general, zinc toxicity decreased while copper toxicity increased downstream of the confluence of the mine impacted Leona Creek and background Lion Creek, indicating a significant source of zinc in upstream, non mine-impacted samples.
Abstract: Water samples collected in an acid mine impacted watershed indicated that the concentrations of dissolved trace metals were diurnally influenced by mineral saturation, which is controlled primarily by pH and water temperature. Measurements taken suggested that these variations only occur at sample locations immediately downstream from the confluence of acidic and alkaline waters. It is at these locations where initial mineral precipitation occurred and where subtle changes in solubility were most affected, increasing trace metal removal when both the rate of photosynthesis (influencing pH in headwaters) and water temperature were at a maximum. The role of iron photoreduction (increased midday production of ferrous iron) on overall Cu, Mn, and Zn transport was also evaluated, but found to be inconclusive. Iron photoreduction may however influence adsorption and/or coprecipitation of trace metals through associated changes in oxidation state, solubility, and mineralogy of various iron colloids, which are produced upon the neutralization of acidic, metal enriched water. Furthermore, measured values of copper and zinc were compared to relative USEPA chronic criterion for exposure to continuous concentration (CCC) of metals by the calculation of a “toxicity unit” (TU). It was found that average values of both copper and zinc only exceeded the CCC (TU>1) in the acid mine-impacted Leona Creek. In general, zinc toxicity decreased while copper toxicity increased downstream of the confluence of the mine impacted Leona Creek and background Lion Creek (sampled at Lake Aliso), indicating a significant source of zinc in upstream, non mine-impacted samples.

01 Jan 2006
TL;DR: Three QTLs for Zn 2+ toxicity tolerance were detected on chromosomes 1, 3 and 10 and explained 21.9, 8.9 and 7.6%, respectively, of the total phenotypic variation in this study.
Abstract: Excess zinc harms the growth of rice plants and zinc toxicity can easily occur in acid soils. The aim of the study was to map quantitative trait loci (QTLs) in rice for tolerance to zinc toxicity, using a recombinant inbred (RI) population derived from the cross of a japonica variety (Asominori: relatively tolerant to Zn 2+ toxicity) with an indica variety (IR24, relatively susceptible), through 289 RFLP markers. The index scores of damage (representing Zn 2+ toxicity tolerance), after irrigating rice seedlings with a 1000-ppm Zn 2+ solution for 20 successive days, were examined for each RI line and its parental varieties. Continuous distributions and transgressive segregations of the index scores were observedin the RI population, suggesting that Zn 2+ toxicity tolerance was a quantitatively inherited trait. Three QTLs for Zn 2+ toxicity tolerance were detected on chromosomes 1, 3 and 10 and explained 21.9, 8.9 and 7.6%, respectively, of the total phenotypic variation. The results and the tightly linked molecular markers that flank the QTLs, detected in this study, will be useful in improving Zn 2+ tolerance in rice. In addition, the genomic positions between QTLs for Zn 2+ toxicity tolerance and the QTLs for other metal (Fe 2+ ,M n 2+ ,A l 3+ ) toxicity tolerances, from previous studies, are discussed. # 2005 Published by Elsevier B.V.