Showing papers on "Zinc toxicity published in 2014"
TL;DR: Zn toxicity, especially for reproduction, was influenced by pH for all Zn forms, and the importance of considering the relationship between uptake and toxicity in nanotoxicology studies is suggested.
Abstract: To determine how soil properties influence nanoparticle (NP) fate, bioavailability and toxicity, this study compared the toxicity of nano zinc oxide (ZnO NPs), non-nano ZnO and ionic ZnCl2 to the earthworm Eisenia fetida in a natural soil at three pH levels. NP characterisation indicated that reaction with the soil media greatly controls ZnO properties. Three main conclusions were drawn. First that Zn toxicity, especially for reproduction, was influenced by pH for all Zn forms. This can be linked to the influence of pH on Zn dissolution. Secondly, that ZnO fate, toxicity and bioaccumulation were similar (including relationships with pH) for both ZnO forms, indicating the absence of NP-specific effects. Finally, earthworm Zn concentrations were higher in worms exposed to ZnO compared to ZnCl2, despite the greater toxicity of the ionic form. This observation suggests the importance of considering the relationship between uptake and toxicity in nanotoxicology studies.
113 citations
TL;DR: The decreases in the four measured biochemical parameters after 3d exposure might reflect the failure of the antioxidant defense system in neutralizing the ROS generated during the metabolic process, while the recovery of the antioxidants at days 12 and 30 suggested a possible shift toward a detoxification mechanism.
111 citations
TL;DR: In this paper, the antibacterial responses of zinc oxide (ZnO) structures against Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pyogenes were investigated.
99 citations
TL;DR: Since the aggregation of NPs generally enhanced at higher salinities, both the dissolution and aggregation of CuO and ZnO NPs may control the effect of salinity on acute toxicity to T. japonicus.
77 citations
TL;DR: The hypothesis that zinc can impair thiol homeostasis, causes an increase in lipid peroxidation and inhibits GR, imposing a pro-oxidant status, which seems to trigger homeostatic mechanisms leading to a subsequent increase on antioxidant-related defenses is supported.
Abstract: Zinc demonstrates protective and antioxidant properties at physiological levels, although these characteristics are not attributed at moderate or high concentrations. Zinc toxicity has been related to a number of factors, including interference with antioxidant defenses. In particular, the inhibition of glutathione reductase (GR) has been suggested as a possible mechanism for acute zinc toxicity in bivalves. The present work investigates the biochemical effects of a non-lethal zinc concentration on antioxidant-related parameters in gills of brown mussels Perna perna exposed for 21 days to 2.6 μM zinc chloride. After 2 days of exposure, zinc caused impairment of the antioxidant system, decreasing GR activity and glutathione levels. An increase in antioxidant defenses became evident at 7 and 21 days of exposure, as an increase in superoxide dismutase and glutathione peroxidase activity along with restoration of glutathione levels and GR activity. After 7 and 21 days, an increase in cellular peroxides and lipid peroxidation end products were also detected, which are indicative of oxidative damage. Changes in GR activity contrasts with protein immunoblotting data, suggesting that zinc produces a long lasting inhibition of GR. Contrary to the general trend in antioxidants, levels of peroxiredoxin 6 decreased after 21 days of exposure. The data presented here support the hypothesis that zinc can impair thiol homeostasis, causes an increase in lipid peroxidation and inhibits GR, imposing a pro-oxidant status, which seems to trigger homeostatic mechanisms leading to a subsequent increase on antioxidant-related defenses.
77 citations
TL;DR: The results suggested that the inoculation of Zea mays plants with P. mirabilis during an earlier growth period could be related to its plant growth promoting activities and avoidance of cumulative damage upon exposure to Zn, thus reducing the negative consequences of oxidative stress caused by heavy metal toxicity.
74 citations
TL;DR: It is demonstrated that ZnT-1 extrudes zinc from mammalian cells by functioning as a Zn(2+)/H(+) exchanger.
Abstract: ZnT-1 is a Cation Diffusion Facilitator (CDF) family protein, and is present throughout the phylogenetic tree from bacteria to humans. Since its original cloning in 1995, ZnT-1 has been considered to be the major Zn2+ extruding transporter, based on its ability to protect cells against zinc toxicity. However, experimental evidence for ZnT-1 induced Zn2+ extrusion was not convincing. In the present study, based on the 3D crystal structure of the ZnT-1 homologue, YiiP, that predicts a homodimer that utilizes the H+ electrochemical gradient to facilitate Zn2+ efflux, we demonstrate ZnT-1 dependent Zn2+ efflux from HEK 293T cells using FluoZin-3 and Fura 2 by single cell microscope based fluorescent imaging. ZnT-1 facilitates zinc efflux in a sodium-independent, pH-driven and calcium-sensitive manner. Moreover, substitution of two amino acids in the putative zinc binding domain of ZnT-1 led to nullification of Zn2+ efflux and rendered the mutated protein incapable of protecting cells against Zn2+ toxicity. Our results demonstrate that ZnT-1 extrudes zinc from mammalian cells by functioning as a Zn2+/H+ exchanger.
70 citations
TL;DR: There was an increase in metal toxicity measured by the biotest with increasing available metal contents in soils, and all the soil samples were classified into toxicity class III, which means that they are toxic and present severe danger.
Abstract: This research is aimed at assessing the total content and soluble forms of metals (zinc, lead and cadmium) and toxicity of soils subjected to strong human pressure associated with mining of zinc and lead ores. The research area lay in the neighbourhood of the Boleslaw Mine and Metallurgical Plant in Bukowno (Poland). The study obtained total cadmium concentration between 0.29 and 51.91 mg, zinc between 7.90 and 3,614 mg, and that of lead between 28.4 and 6844 mg kg−1 of soil d.m. The solubility of the heavy metals in 1 mol dm−3 NH4NO3 was 1–49 % for zinc, 5–45 % for cadmium, and S. alba = V. fischeri > L. sativum. Significant positive correlations (p ≤ 0.05) of the total and soluble contents of the metals with luminescence inhibition in V. fischeri and root growth inhibition in S. saccharatum were found. The general trend observed was an increase in metal toxicity measured by the biotest with increasing available metal contents in soils. All the soil samples were classified into toxicity class III, which means that they are toxic and present severe danger. Biotest are a good complement to chemical analyses in the assessment of quality of soils as well as in properly managing them.
61 citations
TL;DR: In this paper, the influence of silicon on higher zinc concentration reducing the growth of aboveground parts was investigated in young maize plants (hybrid Novania) grown in hydroponics.
Abstract: We have investigated the influence of silicon on higher zinc concentration reducing the growth of aboveground parts by ca 50 % in young maize plants (hybrid Novania) grown in hydroponics. Eight different treatments were used: control, Zn (800 μM ZnSO4·7H2O), Si1/Si2.5/Si5 (1/2.5/5 mM Na2SiO7) and Zn+Si (combination of zinc and all silicon concentrations). The concentration of Zn and Si and their distribution in plants was determined. The growth parameters (length of primary seminal root, leaf area of first and second leaves, fresh and dry weight of below- and above-ground plant parts) of plants grown in various Zn+Si treatments were significantly decreased in comparison to all other treatments. Increasing concentration of Si in combination with Zn treatment and selected hybrid (Novania) resulted in increased physiological stress in comparison to Zn treatment. However, roots and shoots of all Zn+Si treated plants contained significantly lower amount of Zn than Zn treatment. The Si concentration in roots was the same in Si and Zn+Si plants. In general, higher amount of Si was observed in shoots than in roots of Si1- and Si2.5-treated plants and opposite was observed in Si5-treated plants. In spite of significantly decreased root and shoot accumulation of Zn in the presence of Si, no positive effect of Si on Zn toxicity in young maize plants under experimental conditions used in this work and used maize hybrid was observed.
49 citations
TL;DR: In this paper, two different zinc oxide nanoparticles, as well as zinc ions, are used to study the cellular responses of the RAW 264 macrophage cell line, and a proteomic screen is used to provide a wide view of the molecular effects of zinc.
Abstract: Two different zinc oxide nanoparticles, as well as zinc ions, are used to study the cellular responses of the RAW 264 macrophage cell line. A proteomic screen is used to provide a wide view of the molecular effects of zinc, and the most prominent results are cross-validated by targeted studies. Furthermore, the alteration of important macrophage functions (e.g. phagocytosis) by zinc is also investigated. The intracellular dissolution/uptake of zinc is also studied to further characterize zinc toxicity. Zinc oxide nanoparticles dissolve readily in the cells, leading to high intracellular zinc concentrations, mostly as protein-bound zinc. The proteomic screen reveals a rather weak response in the oxidative stress response pathway, but a strong response both in the central metabolism and in the proteasomal protein degradation pathway. Targeted experiments confirm that carbohydrate catabolism and proteasome are critical determinants of sensitivity to zinc, which also induces DNA damage. Conversely, glutathione levels and phagocytosis appear unaffected at moderately toxic zinc concentrations.
44 citations
TL;DR: Toxicity of cadmium, copper and zinc was tested on four green algal species isolated from a highly polluted river and showed that C. ellipsoidea was the most abundant species and the less abundant species was S. acuminatus.
Abstract: Toxicity of cadmium, copper and zinc was tested on four green algal species (Ankistrodesmus fusiformis, Chlorella ellipsoidea, Monoraphidium contortum and Scenedesmus acuminatus) isolated from a highly polluted river (Matanza–Riachuelo River, Buenos Aires, Argentina). The relative abundance of these species in river waters showed that C. ellipsoidea was the most abundant species (mean 4,540 ind mL−1), whereas the less abundant species was S. acuminatus (mean 220 ind mL−1). The most sensitive species was A. fusiformis, which EC50 were Cd = 141 μg L−1, Cu = 72 μg L−1, and Zn = 199 μg L−1, whereas C. ellipsoidea was the most resistant species to copper (EC50 = 489 μg L−1) and cadmium (EC50 = 429 μg L−1), and M. contortum and S. acuminatus were the most resistant species to zinc (EC50 = 381 and 394 μg L−1, respectively).
TL;DR: It is reported that under conditions mimicking ischemia in hippocampal neurons – normal calcium plus elevated (> 100 μM) exogenous zinc – mitochondrial dysfunction evoked by glutamate, kainate or direct depolarization is, despite significant zinc uptake, primarily governed by calcium.
Abstract: Zinc has been implicated in neurodegeneration following ischemia. In analogy with calcium, zinc has been proposed to induce toxicity via mitochondrial dysfunction, but the relative role of each cation in mitochondrial damage remains unclear. Here, we report that under conditions mimicking ischemia in hippocampal neurons - normal (2 mM) calcium plus elevated (> 100 μM) exogenous zinc - mitochondrial dysfunction evoked by glutamate, kainate or direct depolarization is, despite significant zinc uptake, primarily governed by calcium. Thus, robust mitochondrial ion accumulation, swelling, depolarization, and reactive oxygen species generation were only observed after toxic stimulation in calcium-containing media. This contrasts with the lack of any mitochondrial response in zinc-containing but calcium-free medium, even though zinc uptake and toxicity were strong under these conditions. Indeed, abnormally high, ionophore-induced zinc uptake was necessary to elicit any mitochondrial depolarization. In calcium- and zinc-containing media, depolarization-induced zinc uptake facilitated cell death and enhanced accumulation of mitochondrial calcium, which localized to characteristic matrix precipitates. Some of these contained detectable amounts of zinc. Together these data indicate that zinc uptake is generally insufficient to trigger mitochondrial dysfunction, so that mechanism(s) of zinc toxicity must be different from that of calcium.
TL;DR: Findings suggest that, despite the occurrence of an oxidative-based response after exposure to lead, copper, and cadmium, this had no consequence in terms of peroxidative membrane damage; furthermore, cholinergic neurotoxicity caused by lead, Copper, and Cadmium did not occur.
Abstract: Exposure to specific metallic compounds can cause severe deleterious modifications in organisms. Fishes are particularly prone to toxic effects from exposure to metallic compounds via their environment. Species that inhabit estuaries or freshwater environments can be chronically affected by persistent exposure to a large number of metallic compounds, particularly those released by industrial activities. In this study, we exposed yellow eels (European eel, Anguilla anguilla) for 28 days to environmentally relevant concentrations of four specific metals; lead (300, 600, and 1,200 μg/l), copper (40, 120, and 360 μg/l), zinc (30, 60, and 120 μg/l) and cadmium (50, 150, and 450 μg/l). The selected endpoints to assess the toxicological effects were neurotransmission (cholinesterasic activity in nervous tissue), antioxidant defense, and phase II metabolism (glutathione-S-transferase [GST] activity, in both gills and liver tissues), and peroxidative damage. The results showed an overall lack of effects on acetylcholinesterase for all tested metals. Lead, copper, and cadmium exposure caused a significant, dose-dependent, increase in GST activity in gill tissue. However, liver GST only significantly increased following zinc exposure. No statistically significant effects were observed for the thiobarbituric acid reactive substances assay, indicating the absence of peroxidative damage. These findings suggest that, despite the occurrence of an oxidative-based response after exposure to lead, copper, and cadmium, this had no consequence in terms of peroxidative membrane damage; furthermore, cholinergic neurotoxicity caused by lead, copper, and cadmium did not occur. The implications of these results are further discussed.
TL;DR: Major ion composition also influenced Zn bioavailability, a common co-occurring metal contaminant in coal mine waters, with sublethal concentrations of NaHCO(3) and elevated pH increasing Zn toxicity.
Abstract: Bicarbonate is often a major ionic constituent associated with produced waters from methane gas extraction and coal mining, yet few studies have determined its specific toxicity. Currently, the environmental risk of bicarbonate anion in water discharges is assessed based on the toxicity of sodium chloride or artificial seawater and is regulated via electrical conductivity. Increased NaHCO3 added to Ceriodaphnia dubia in synthetic or natural water gave similar 48-h 10% effective concentration (EC10) values of 1750 ± 125 mg NaHCO3/L (mean ± standard error) and 1670 ± 180 mg NaHCO3/L, respectively. Bicarbonate was toxic to C. dubia in both waters with conductivities above 1900 µS/cm. In contrast, when conductivity was elevated with NaCl, toxicity to C. dubia was observed only above 2800 µS/cm. Bicarbonate also impaired C. dubia reproduction with an EC10 of 340 mg NaHCO3/L. Major ion composition also influenced Zn bioavailability, a common co-occurring metal contaminant in coal mine waters, with sublethal concentrations of NaHCO3 and elevated pH increasing Zn toxicity. Higher pH was the dominant parameter determining a 10-fold increase in the 48-h 50% effective concentration (EC50) for Zn toxicity to C. dubia at pH 8.6 of 34 µg Zn/L (95% confidence limit = 32–37 µg Zn/L) compared with the Zn toxicity at approximately circumneutral pH. Exposure of the freshwater shrimp Paratya australiensis (Atyidae) in natural water to increasing bicarbonate gave a mean 10-d 10% lethal concentration (LC10) of 850 ± 115 mg NaHCO3/L, associated with a mean conductivity EC10 of 1145 µS/cm, which is considerably lower than toxicity of NaCl and artificial seawater to this species reported elsewhere. Because toxicity was influenced by salt composition, specific ions should be regulated rather than conductivity alone in mine wastewater discharges. Environ Toxicol Chem 2014;33:1179–1186. © 2014 SETAC
TL;DR: The current concepts concerning zinc biology, its metabolism and transport into cells, its homeostasis, and its role in the functioning of the human immune and endocrine systems, as well as the biophysical mechanisms of action of zinc ions at elevated concentrations on human blood cells are reviewed and analyzed.
Abstract: In this review the current conceptions concerning zinc biology, its metabolism and transport into the cells, its homeostasis, a role in the functioning of the human immune and endocrine systems, participation in cell signaling and its cytotoxicity, as well as the biophysical mechanisms of action of zinc ions action at the elevated concentrations on human blood cells were analyzed.
TL;DR: The results show that C. elegans wild type nematodes exhibit severe lethal toxicity after a 24h exposure to zinc at higher temperatures, and the expression level of Hsp90 was highly inhibited in adult worms subjected to zinc stress.
TL;DR: This work is a relevant contribution as foundation for the use of AChE in freshwater crustaceans in further studies including biomonitoring campaigns in different contamination scenarios.
Abstract: Metals are released into freshwater ecosystems from natural and anthropogenic sources, compromising their structural and functional equilibrium. As early warning tools, cholinesterases (ChEs) are usually used to assess the effects of organophosphate and carbamate pesticides, but are also known to be inhibited by metals. The objectives of this work were to characterise the activity of ChE present in the amphipod Echinogammarus meridionalis and the shrimp Atyaephyra desmarestii and to evaluate the in vivo effects of the metals copper and zinc in their ChE activity. To achieve this, firstly the activity of ChE forms were characterised using different in vitro assays with substrates and selective inhibitors. Then, the in vivo effects of 48 h exposures to increasing concentrations of copper and zinc on ChE activity were determined. The ChE form present in both species was acetylcholinesterase (AChE) since both revealed preference for the acetylthiocholine iodide substrate, total inhibition with eserine, the inhibitor of ChEs, and with 1,5-bis(4-allyldimethylammoniumphenyl)-pentan-3-one dibromide, the specific inhibitor of AChE, and presented insensitivity to iso-OMPA, a specific inhibitor of butyrylcholinesterase. The activity of ChEs was inhibited by zinc exposures in the amphipod species, but was not affected by copper. Exposure to copper and zinc did not affect ChEs activity in the shrimp at the concentrations tested. This work is a relevant contribution as foundation for the use of AChE in freshwater crustaceans in further studies including biomonitoring campaigns in different contamination scenarios.
TL;DR: In this article, the expression profiles of the following genes were analyzed: BAX, Bcl-2, Beclin-1, CFLAR, HIF1α, KRAS, mTOR, MT1A, MT2A, NF-κB1, p53, survivin, ZIP1, ZnT-1.
Abstract: Zinc(II) ions are important components of many proteins and are involved in numerous cellular processes such as apoptosis or drug resistance. Prostate cancer has a unique relationship with zinc(II) ions. However, the relationship was examined only in short-term zinc(II) treatments. Therefore, the aim of this study was to create zinc-resistant prostatic cell lines at various stages of the disease (22Rv1 and PC-3) and a normal prostate epithelium (PNT1A) using a long-term zinc exposure. Consequently, the expression profile of the following genes was analyzed: BAX, Bcl-2, Beclin-1, CFLAR, HIF1α, KRAS, mTOR, MT1A, MT2A, NF-κB1, p53, survivin, ZIP1, ZnT-1. The resistance was verified using the MTT test; on average a 1.35-fold lower zinc(II) toxicity (higher IC50) was determined in zinc(II)-resistant cells. The associated resistance to cisplatin was also determined; IC50 for cisplatin was 1.52-fold higher. With regard to the gene expression profiles, our results indicate that differential mechanisms participate in the short-term zinc toxicity regulation and long-term resistance; the short-term treatment was associated with MT2A (p < 0.001), ZnT-1 (p < 0.001), and MT1A (p < 0.03) and the long-term resistance was associated particularly with NF-κB1 (p < 0.001), CFLAR (p < 0.001), KRAS (p < 0.001), p53 (p < 0.002), survivin (p = 0.02), ZIP1 (p = 0.002), BAX (p = 0.005), and HIF1α (p = 0.05). Therefore, the KRAS-PI3K-NF-κB pathway is expected to play a crucial role in the regulation of zinc resistance. In summary, compared to previous studies, identical mechanisms of resistance were demonstrated on multiple cell lines, both non-tumor and tumorous, derived both from primary and advanced secondary sites.
TL;DR: This is the first study to demonstrate the effect of waterborne Zn exposure on lipid metabolism in extrahepatic tissues at the molecular level, and contributes to the understanding of Zn-induced toxicity in fish.
Abstract: The aim of this study was to determine the potential mechanisms of exposure to waterborne zinc (Zn) on lipid metabolism in three extrahepatic tissues (ovary, muscle and mesenteric adipose tissue) of female yellow catfish Pelteobagrus fulvidraco. Female yellow catfish were chronically exposed to Zn (0.05, 0.35 or 0.86 mg Zn/l; duration of treatment 8 weeks) or acutely exposed to a high level of Zn (4.71 mg Zn/l for 96 h). Following the respective treatment, lipid deposition and mRNA levels of 11 genes (CPT IA, CPT IB, PPARα, PPARγ, SREBP-1, G6PD, 6PGD, FAS, ACCa, ACCb and LPL) involved in lipid metabolism were determined. Waterborne Zn exposure significantly reduced growth performance and lipid content in muscle but had no significant effect on lipid content in ovary and mesenteric adipose tissue. The change in the levels of the mRNA genes under study was Zn concentration-dependent and tissue-dependent. Pearson correlations between the mRNA levels of three transcriptional factors and enzymes in these tissues revealed that variations in gene expression as a result of the different Zn treatments underlay the patterns of lipid metabolism, which in turn affected fat storage and mobilization. To our knowledge, this is the first study to demonstrate the effect of waterborne Zn exposure on lipid metabolism in extrahepatic tissues at the molecular level. These results therefore contribute to our understanding of Zn-induced toxicity in fish.
TL;DR: The metal resistance-related genes showed different transcriptional expression patterns in six A. ferrooxidans strains and the results of RT-qPCR and bioinformatics analysis showed a clear correlation between the zinc tolerance levels of six strains.
Abstract: Metal resistance of acidophilic bacteria is very significant during bioleaching of copper ores since high concentration of metal is harmful to the growth of microorganisms. The resistance levels of six Acidithiobacillus ferrooxidans strains to 0.15 M copper and 0.2 M zinc were investigated, and eight metal resistance-related genes (afe-0022, afe-0326, afe-0329, afe-1143, afe-0602, afe-0603, afe-0604, and afe-1788) were sequenced and analyzed. The transcriptional expression levels of eight possible metal tolerance genes in six A. ferrooxidans strains exposed to 0.15 M Cu(2+) and 0.2 M Zn(2+) were determined by real-time quantitative PCR (RT-qPCR), respectively. The copper resistance levels of six A. ferrooxidans strains declined followed by DY26, DX5, DY15, GD-B, GD-0, and YTW. The zinc tolerance levels of six A. ferrooxidans strains exposed to 0.2 M Zn(2+) from high to low were YTW > GD-B > DY26 > GD-0 > DX5 > DY15. Seven metal tolerance-related genes all presented in the genome of six strains, except afe-0604. The metal resistance-related genes showed different transcriptional expression patterns in six A. ferrooxidans strains. The expression of gene afe-0326 and afe-0022 in six A. ferrooxidans strains in response to 0.15 M Cu(2+) showed the same trend with the resistance levels. The expression levels of genes afe-0602, afe-0603, afe-0604, and afe-1788 in six strains response to 0.2 M Zn(2+) did not show a clear correlation between the zinc tolerance levels of six strains. According to the results of RT-qPCR and bioinformatics analysis, the proteins encoded by afe-0022, afe-0326, afe-0329, and afe-1143 were related to Cu(2+) transport of A. ferrooxidans strains.
Journal Article•
TL;DR: In this paper, the effect of zinc on primary reactions of photosynthesis was investigated and the PAM kinetic measurements revealed suppression of variable fluorescence in terms of relative distance from 5.4 to 2.7 Cm during the treatment.
Abstract: In this investigation an attempt has been made to study the effect of Zinc on primary reactions of photosynthesis. Photosystem II mediated electron transport activity exhibited 68% loss at 180 μM concentration. The PAM kinetic measurements revealed suppression of variable fluorescence in terms of relative distance from 5.4 to 2.7 Cm during the treatment. These measurements suggest that the targets of PSII are at water oxidation complex and Light harvesting complex as multiple sites of damage in Zinc toxicity. Another target site of zinc toxicity in photosystem II is evidenced from the loss of 33kDa protein band SDS-PAGE profiles of thylakoid membranes.
Dissertation•
01 Jan 2014
TL;DR: The results obtained in this study suggested that N. virens is tolerant to copper and zinc pollution through the activation of detoxification processes as defence mechanisms leading to the possibility of metal adaptation at a population level.
Abstract: Although copper and zinc are essential metals to aquatic organisms, they can become contaminants and potentially toxic to marine invertebrates due to anthropogenic activities. The king ragworm, Nereis virens is an ecologically and commercially important polychaete species of soft sediment inter-tidal communities found throughout Europe and the northern hemisphere and is exposed to elevated levels of contaminants including metals. However, the impact of longterm exposure of copper and zinc alone and combined has not yet been investigated. In this context, this study aimed to undertake a nine months experiment, sampling every three months, based on environmentally relevant concentrations obtained from a field sampling effort, in combination to a multi-biomarker approach. Using the polychaete N. virens as test species, this multi-biomarker approach revealed the effects of copper and zinc not only at an individual level but also and more importantly at a population level. It is valid to investigate chronic effects of these pollutants as this species readily acclimatises to captive conditions and the endocrine control of growth, maturation and reproduction is already well documented. N. virens were incubated for nine months in environmentally relevant concentrations of copper-spiked sediment, zinc-spiked sediment and copper & zinc combined-spiked sediment. These concentrations were obtained thanks to preliminary field samples of sediment, pore-water and N. virens collected from seven sites along the English Channel coast namely Mylor (Fal Estuary), Saltash, Tamar Estuary), Holes Bay (Poole Harbour), Tipner (Portsmouth Harbour), Broadmarsh (Langstone Harbour) and the Conservancy & Dell quay (Chichester Harbour). Results from these seven sites showed that site-specific metal levels and sediment characteristics were important in determining the bioavailability of metals to worms. Strong correlations were found between copper in the sediment and in the pore water and between zinc in the pore water and in N. virens. Zinc from the pore water was thus more readily available to N. virens than copper. Data also showed that metal concentrations in the worms were lower than those found in other closely related polychaetes, indicating that N. virens may regulate the uptake of metals. Based on data obtained from Holes Bay, Saltash and Mylor, the copper-spiked sediment values ranged from 70 mg kg⁻¹ to 575 mg kg⁻¹, the zinc-spiked sediment values from 200 mg kg⁻¹ to 1160 mg kg⁻¹ and the combination of both were used for the combined treatments. A range of endpoints were then used allowing the study of behavioural, biochemical, cellular and genetic changes over time. As high variability in responses were observed over time, this study revealed the complexity of interpreting metal toxicity. Overall, high copper and high copper & zinc combined treatments showed the most damages with hypoactivity, increase of metallothionein concentrations, inhibition of acetylcholinesterase activity, decrease in cell viability and increase of DNA damage. However, no significant correlations were obtained for acetylcholinesterase activity suggesting that this biomarker is not adequate when considering metal toxicity to N. virens. In addition, the effects of metals on energy reserves were difficult to evaluate as no clear trends were observed. Moreover, seasonal fluctuations and reproduction that occurred during the long-term experiment have proven to be important factors while investigating long-term effects of metals on N. virens. However, the results obtained in this study suggested that N. virens is tolerant to copper and zinc pollution through the activation of detoxification processes as defence mechanisms leading to the possibility of metal adaptation at a population level. For the first time, this study revealed that not only high levels of copper were toxic to N. virens but also that the combination of high copper & zinc treatment was highly and even more toxic to these worms. BioAccumulation Ratios showed that the competition for the uptake between copper and zinc varied over time and was dependent on metal concentrations. In addition, the evaluation of the Biomarker Response Index revealed 1. that the combined, high copper & zinc treatment, was the most toxic to the worms and 2. that DNA damage, metallothioneins and weight were the most sensitive and reliable endpoints used to evaluate copper and zinc toxicity.
TL;DR: Morphological changes were observed in mucilage cells concerning the mucilage structure and appearance and the vacuome was drastically reduced in all cells, except in the subglandular ones and electron dense membrane remnants were observed.
Abstract: Zinc toxicity in secretory cells caused a range of effects, mainly depending on metal concentration. Low concentrations activated nectary function increasing nectar secretion but secretion was greatly inhibited or stopped entirely by ongoing concentration. Water loss rate of zinc treated flower parts was significantly reduced whereas green sepals were dehydrated more rapidly in comparison to colored petals. The content of zinc, calcium, magnesium and manganese increased mainly in sepals under excess of zinc, but in the secreted nectar this metal was not evident. Morphological changes were observed in mucilage cells concerning the mucilage structure and appearance. The parenchymatic, subglandular cells displayed an early vacuolarization and cytoplasm condensation. Secretory hairs appeared to be thinner, the apical cell folded inwards and plasmolytic shrinkage became severe in all cells. The waxy cuticula showed an increased electron density. A plasmalemma detachment from the external cell walls was observed creating a gap between cell wall and plasmalemma. ER cisterns of all treated nectary hairs dominated the cytoplasm and electron dense deposits were seen within its profiles. A great number of other organelles were also present, showing electron dense deposits in their membranes as well. The vacuome was drastically reduced in all cells, except in the subglandular ones and electron dense membrane remnants were observed.
13 May 2014
TL;DR: In this paper, the toxic effect of zinc (Zn) was studied with special attention being given to the biochemical response of lens culinaris L., exposed to zinc toxicity at different concentration levels.
Abstract: In the given study, the toxic effect of zinc (Zn) was studied with special attention being given to thebiochemical response of Lens culinaris L., exposed to zinc toxicity at different concentration levels.The research carried out in a randomized complete block design with 3 replications of each treatment.The major change was observed in the production and accumulation of primary metabolites (i.e.protein and protease) and activity of antioxidant enzymes i.e. catalase (CAT) and acid phosphatase(APS). The data showed that the low concentration of Zn addition support soluble protein accumulationin lentil leaves, although protease activity greatly arrested the protein content and appeared as anegative factor with increasing Zn levels. The response of antioxidant enzymes was also dose dependant,it increases their activity to suppress oxidative stress produced by heavy metal but at high dose theybecome ineffective due to increase in oxidation process controlled by metal application. The peak ofactivity appeared at 4ppm to 8ppm Zn.a