Effects Of Metal Exposure Research Articles

Associations between multiple metals exposure and cognitive function in the middle-aged and older adults from China: A cross-sectional study

The rapidly rising risk of cognitive decline is a serious challenge for the elderly. As the wide-distributed environmental chemicals, the effects of metals exposure on cognitive function have attracted much attention, but the results remain inclusive. This study aimed to investigate the roles of multiple metals co-exposure on cognition. We included a total of 6112 middle-aged and older participants, detected their plasma levels of 23 metals by using inductively coupled plasma mass spectrometry, and assessed their cognitive function by using the Mini-Mental State Examination (MMSE). The results showed that increased plasma levels of iron (Fe) and zinc (Zn) were positively associated with MMSE score, but the increased levels of nickel (Ni) and lead (Pb) were associated with decreased MMSE score (all FDR < 0.05). Subjects exposed to both high levels of Ni and Pb showed the lowest MMSE score [β (95% CI) = −0.310 (−0.519, −0.100)], suggesting that Ni and Pb had a synergistic toxic effect on cognitive function. In addition, the hazardous roles of Ni and Pb were mainly found among subjects with low plasma level of Zn, but were not significant among those with high-Zn level [Ni: β (95% CI) = −0.281 (−0.546, −0.015) vs. −0.146 (−0.351, 0.058); Pb: β (95% CI) = −0.410 (−0.651, −0.169) vs. −0.060 (−0.275, 0.155)], which suggested that Zn could attenuate the adverse effects of Pb and Ni on cognitive function. The cognitive function was gradually decreased among subjects with increased number of adverse exposures to the above four metals (Ptrend < 0.001). In conclusion, our findings revealed the individual, interactive, and combined effects of Fe, Ni, Pb, and Zn on cognitive function, which may provide new perspectives on cognitive protection, but further prospective cohort studies and biological researches are needed to validate these findings.

Association of plasma metals with resting-state functional connectivity in ischemic stroke

BackgroundMetal exposure has long been considered a significant risk factor for ischemic stroke. However, existing data on the effects of metal exposure on brain function in ischemic stroke are limited. Therefore, this study aimed to explore the correlation between exposure to various metals and changes in resting-state functional connectivity (rs-FC) in ischemic stroke patients. MethodsThis study included 28 acute ischemic stroke patients with hemiplegia and 28 matched healthy controls (HCs). All participants underwent T1-weighted MRI and 3.0 T resting-state functional magnetic resonance imaging (fMRI). After MRI acquisition, the rs-FC between 137 cortical and subcortical regions was extracted and preprocessed. Plasma levels of 19 metals were measured using inductively coupled plasma mass spectrometry (ICP-MS). The Bayesian kernel machine regression (BKMR) model and the weighted quantile sum regression (WQS) model were used to assess the overall effect of metal mixture exposure. The severity of neurological deficits in each acute ischemic stroke patient was evaluated using the National Institutes of Health Stroke Scale (NIHSS). Additionally, the associations between exposure to various metals and modifications in brain functional connectivity were determined using Pearson or Spearman correlation analysis. ResultsBilateral brain connectivity was significantly decreased compared to controls and was associated with neurological impairment in ischemic stroke. In patients with ischemic stroke, the plasma concentrations of Cr (p < 0.001), Cu (p = 0.004), As (p = 0.010), Cs (p = 0.046), Rb (p = 0.041), and Sb (p = 0.001) were significantly higher than those in the HCs, whereas the plasma Tl concentrations (p = 0.022) were significantly lower. The results of the BKMR and WQS models showed that combined exposure to metal mixtures was linked to a higher risk of ischemic stroke. Cr was positively correlated with the rs-FC between the left Rolandic_Oper and the left Supp_Motor_Area (r = 0.414, p = 0.029), while negatively correlated with the rs-FC between the right Parietal_Inf and the left supramarginal (r = −0.398, p = 0.037). Cu was negatively correlated with the rs-FC between the left paracentral lobule and the left thalamus (r = −0.409, p = 0.031). Tl was positively correlated with the rs-FC between the right Parietal_Inf and the left supramarginal cortex (r = 0.590, p = 0.001). A negative correlation was observed between Cs and rs-FC between the right Cingulate_Mid and left Occipital_Sup (r = −0.429, p = 0.024). Sb was negatively correlated with the rs-FC between the left Parietal_Inf and the right SupraMarginal (r = −0.384, p = 0.044), the right Parietal_Inf and the left SupraMarginal (r = −0.583, p = 0.001), and the left SupraMarginal and the right SupraMarginal (r = −0.377, p = 0.048). ConclusionPlasma levels of Cr, Cu, Tl, Cs, and Sb were associated with altered rs-FC in brain regions related to motor control, sensory integration, executive function, language processing, and emotional regulation in ischemic stroke patients with basal ganglia infarction.

Effects of metals exposure on morphological and histological structure of the digestive gland in native and invasive clams in the Paraná de las Palmas River (Buenos Aires, Argentina)

Effects of metals exposure on morphological and histological structure of the digestive gland in native and invasive clams in the Paraná de las Palmas River (Buenos Aires, Argentina)

Association between plasma metal exposure and health span in very elderly adults: a prospective cohort study with mixture statistical approach.

Metals have been linked to a diverse spectrum of age-related diseases; however, the effects of metal exposure on health span remains largely unknown. This cohort study aims to determine the association between plasma metal and health span in elder adults aged ≥ 90years. The plasma concentrations of seven metals were measured at baseline in 300 elder adults. The end of the health span (EHS) was identified as the occurrence of one of eight major morbidities or mortality events. We used Cox regression to assess hazard ratios (HR). The combined effects of multiple metal mixtures were estimated using grouped-weighted quantile sum (GWQS), quantile g-computation (Q-gcomp), and Bayesian kernel machine regression (BKMR) methods. The estimated HR for EHS with an inter-quartile range (IQR) increment for selenium (Se) was 0.826 (95% confidence interval [CI]: 0.737-0.926); magnesium (Mg), 0.806 (95% CI: 0.691-0.941); iron (Fe), 0.756 (95% CI: 0.623-0.917), and copper (Cu), 0.856 (95% CI: 0.750-0.976). The P for trend of Se, Mg, and Fe were all < 0.05. In the mixture analyses, Q-gcomp showed a negative correlation with EHS (P = 0.904), with the sum of the negative coefficients being -0.211. Higher plasma Se, Mg, and Fe reduced the risk of premature end of health span, suggesting that essential metal elements played a role in health maintenance in elder adults.

Corrosion Behavior of Aluminum Alloys in Different Alkaline Environments: Effect of Alloying Elements and Anodization Treatments

Aluminum alloys are extensively used to manufacture mechanical components. However, when exposed to alkaline environments, like lubricants, refrigerants, or detergents, they can be corroded, reducing their durability. For this reason, the aim of this study is to investigate the influence of aggressive alkaline solutions (i.e., pH and presence of chlorides) on the corrosion resistance of three aluminum alloys (AA 5083-H111, AA 6082-T6, and AA 7075-T6) with and without anodizing treatments. Open circuit potential (EOCP) and anodic polarization measurements were carried out and typical corrosion parameters such as corrosion current density (icor) and corrosion rate (CR) were determined. Morphology of the corrosion attack and samples microstructure were investigated by scanning electron microscope. Results show that corrosion behavior of the three investigated alloys is influenced by (i) the aggressiveness of the testing environments; (ii) the thickness of the anodizing treatment; (iii) the alloy chemical composition; (iv) the distribution of intermetallic phases in the aluminum matrix. Moreover, three galvanic series have been built also testing other metallic alloys commonly used in mechanical applications, i.e., carbon steel (C40), stainless-steel (AISI 304), and Cu-based alloys (Cu-Ni alloy and CW 617 N, respectively). Results clearly indicate that galvanic series play a fundamental role when it is necessary to select an alloy for a specific environment, highlighting the thermodynamic conditions for corrosion occurrence. On the other hand, kinetic measurements and microstructural studies carried out on the three aluminum alloys stress the importance of the surface treatments and relevant thickness as well as the effect of metal exposure. Future work will involve the study of other surface treatments on aluminum alloys and the evaluation of their corrosion behavior in acidic environments.

Phytoremediation ability and selected genetic transcription in Hydrocotyle umbellata-under cadmium stress

Cadmium (Cd) is the most toxic element which may cause serious consequences to microbial communities, animals, and plants. The use of green technologies like phytoremediation employs plants with high biomass and metal tolerance to extract toxic metals from their rooting zones. In the present work, Hydrocotyle umbellata was exposed to five Cd concentrations (2, 4, 6, 8, and 10 µmol) in triplicates to judge its phytoextraction ability. Effects of metal exposure on chlorophyll (Chl), bio-concentration factor (BCF), translocation factor (TF), and electrolyte leakage (EL) were analyzed after 10 days of treatment. Metal-responding genes were also observed through transcriptomic analysis. Roots were the primary organs for cadmium accumulation followed by stolon and leaves. There was an increase in EL. Plants showed various symptoms under increasing metal stress namely, chlorosis, browning of the leaf margins, burn-like areas on the leaves, and stunted growth, suggesting a positive relationship between EL, and programmed cell death (PCD). Metal-responsive genes, including glutathione, expansin, and cystatin were equally expressed. The phytoextraction capacity and adaptability of H. umbellata L. against Cd metal stress was also demonstrated by BCF more than 1 and TF less than 1.

Associations Between Individual and Combined Metal Exposures in Whole Blood and Kidney Function in U.S. Adults Aged 40 Years and Older.

The effects of metal exposure on kidney function have been reported in previous literature. There is limited and inconsistent information on the associations between individual and combined exposures to metals and kidney function among the middle-aged and older population.The aim of this study was to clarify the associations of exposure to individual metals with kidney function while accounting for potential coexposure to metal mixtures and to evaluate the joint and interactive associations of blood metals with kidney function.A total of 1669 adults aged 40 years and older were enrolled in the present cross-sectional study using the 2015-2016 National Health and Nutrition Examination Survey (NHANES). Single-metal and multimetal multivariable logistic regression models, quantile G-computation, and Bayesian kernel machine regression models (BKMR) were fitted to explore the individual and joint associations of whole blood metals [lead (Pb), cadmium (Cd), mercury (Hg), cobalt (Co), manganese (Mn), and selenium (Se)] with the odds of decreased estimated glomerular filtration rate (eGFR) and albuminuria. A decreased eGFR was defined as an eGFR ≤ 60 mL/min per 1.73 m2, and albuminuria was categorized as a urinary albumin-creatinine ratio (UACR) of ≥ 30.0 mg/g.The results from quantile G-computation and BKMR indicated positive associations between exposure to the metal mixture and the prevalence of decreased eGFR and albuminuria (all P values < 0.05). These positive associations were mainly driven by blood Co, Cd, and Pb. Furthermore, blood Mn was identified as an influential element contributing to an inverse correlation with kidney dysfunction within metal mixtures. Increasing blood Se levels were negatively associated with the prevalence of decreased eGFR and positively associated with albuminuria. In addition, a potential pairwise interaction between Mn-Co on decreased eGFR was identified by BKMR analysis.Findings from our study suggested a positive association between exposure to the whole blood metal mixture and decreased kidney function, with blood Co, Pb, and Cd being the main contributors to this association, while Mn demonstrated an inverse relationship with renal dysfunction. However, as our study was cross-sectional in nature, further prospective studies are warranted to better understand the individual and combined effects of metals on kidney function.

Epidemiological research progress in the effects of metal exposure on kidney.

Chronic kidney disease (CKD) is suffered progressive loss of kidney function lasting more than 3 months and is classified according to the degree of kidney damage (level of proteinuria) and the decreased glomerular filtration rate (GFR). The most severe form of CKD is end-stage renal disease. The prevalence of CKD is high with fast growth rate and the disease burden has become increasingly serious. CKD has become an important public health problem threatening human health. The etiology of CKD is complex. In addition to genetic factors, environmental factors are an important cause of CKD. With the development of industrialization, environmental metal pollution has become increasingly severe, and its impact on human health has received widespread attention. A large number of studies have shown that metals such as lead, cadmium, and arsenic can accumulate in the kidney, which can cause damage to the structure and function of the kidney, and play an important role in the development of CKD. Therefore, summarizing the epidemiological research progress in the relationship between arsenic, cadmium, lead, and other metal exposures and kidney diseases can provide new ideas for the prevention and control of kidney diseases caused by metal exposure.

Dodonaea viscosa (Sapindaceae) as a phytoremediator for soils contaminated by heavy metals in abandoned mines.

Dodonaea viscosa (L.) Jacq. is a plant with a wide distribution that expands throughout almost all Mexican territory and is used in traditional medicine to treat many ailments. This species has been found associated with polluted areas, including mine tailings. Huautla, Morelos, Mexico, was a metallurgic district where mining activities generated 780,000 tons of waste rich in metals, deposited at 500m from the town without any treatment; this situation has been related to different environmental threats and human health risks. The study was carried out for 18months on seedlings developed under greenhouse conditions in two treatments: control substrate and mine tailings substrate. The concentration of six metals (Cd, Cr, Cu, Fe, Pb, and Zn) was measured through atomic absorption spectrophotometry in plant tissues, roots, and leaves. Effects of metal exposure were analyzed by size, micro-morphological character changes, and genetic damage in foliar tissue using the comet assay. The results showed significantly higher metal concentrations in the roots and leaves of individuals growing on the mine tailing substrate in comparison to the same plants tissues growing on control substrate. Positive and significant relationships between exposure time and metal concentration in roots and leaves, and between metal bioaccumulation in leaves and genetic damage were registered. Four out of six micro-morphological and size characters evaluated decreased significantly in exposed plants, except for stomatic index and root biomass. The most important metals in terms of the number of significantly affected micro-morphological and size characters showed the next pattern: Fe > Cd = Cr = Pb > Cu > Zn. D. viscosa is an efficient accumulator of Cu, Cd, Fe, Pb, and Zn in its root and leaf tissues. Overall, metal translocation factors in exposed D. viscosa plants showed the following pattern: Zn > Cu > Cd. We conclude that D. viscosa has the potential to phytoextract (Zn, Cu, and Cd), and phytostabilize (Cu, Cd, Fe, Pb, and Zn) metals from polluted soils, and along with its abundance, natural establishment in mine tailings, high levels of metal translocation, and bioconcentration factors, without affecting plant development, it can be an ideal candidate for phytoremediation of metal polluted soils.

The Relationship between Metal Exposure and Chronic Obstructive Pulmonary Disease in the General US Population: NHANES 2015-2016.

The effects of metal on pulmonary function are inconsistent, and abnormal distribution of metals can decrease lung function. However, the effects of metals exposure on chronic obstructive pulmonary disease (COPD) are still unclear. This study aims to explore the relationship between metal exposure and COPD risk. Cross-sectional data from the National Health and Nutrition Survey (NHANES) 2015–2016 was analyzed. Inductively coupled plasma dynamic reaction cell mass spectrometry (ICP-DRC-MS) was used to measure the metals concentration in the blood. The multiple linear regression and restricted cubic spline (RCS) were used to analyze the relationship between metals exposure and COPD risk. In this study, 1399 participants were included, of which 107 participants were diagnosed with COPD using self-reported chronic bronchitis, emphysema, and COPD. The second and third tertiles of copper increased the COPD risk by 1.98-fold (95% CI: 1.08–3.62) and 2.43-fold (95% CI: 1.32–4.48) compared with the first tertile, using p = 0.005 for the trend after adjusting for the covariates. RCS showed a positive linear correlation between copper and COPD risk (p = 0.006 for overall association) in all participants. When stratified by sex, the multi-factor analysis showed that the third tertile of copper increased male’s COPD risk by 3.42-fold (95% CI: 1.52–7.76), with p = 0.003 for the trend, and RCS also showed a positive linear correlation (p = 0.013 for overall association). Although RCS showed that selenium can reduce the COPD risk (p = 0.008 for overall association) in males, an association between selenium and COPD was not observed (p > 0.05). Our findings suggest that a high concentration of copper may increase COPD risk in males in the general US population, and more research is needed to explore its possible mechanism of action.

Child Health Cohort Study. “Bruminha project”.

Background: After the breakdown of the metal residue dam in Brumadinho - Minas Gerais State, Brazil, one of the main concerns is possible impacts these residues on the health of children living in the affected areas. We will investigate metal concentrations and their effects on immunologic and neurological development, growth and respiratory health of children from 0 to 4 years old living in areas affected by the disaster. Methods: A prospective cohort study, whose study population comprises 200 children aged 0 - 4 years old living in the struck areas, and a control group, living in a non-affected area. Questionnaires, clinical evaluations, and metal assessments in biological samples (urine and blood) will be carried out each year over 4 years. Results: The investigation and identification of possible metal exposure effects on child health will be applied to public health action settlements.

Clinical biochemical parameters associated with the exposure to multiple environmental metals in residents from Kabwe, Zambia

Lead (Pb) interferes with various bodily functions. Although high blood Pb (Pb–B) levels in residents from Kabwe, Zambia have been reported, the accumulation pattern of other metals remains unknown. The study was designed to determine the Pb–B, blood cadmium (Cd–B), and zinc (Zn–B) values of 504 representative samples from Kabwe, as well as the potential associated adverse health effects. The Pb–B level ranged from 0.79 to 154.75 μg/dL and generally increased in areas near the mine. A significant elevation of Cd–B was observed in two areas (0.37 ± 0.26 and 0.32 ± 0.30 μg/L) where the two highest mean Pb–B levels were recorded. By contrast, the Zn–B values did not differ greatly with respect to area. Some blood biochemical parameters relating to hepatic and renal functions were out of the normal range in approximately 20–50% of studied adult participants. The δ-aminolevulinic acid dehydratase (δ-ALAD) activity was significantly inhibited in the two areas contaminated by Pb and Cd. A significant negative relationship was observed between metal levels and clinical parameters, e.g., between Pb–B and δ-ALAD for all the age categories and between Cd–B and the estimated glomerular filtration rate for all the age categories except 0–4 years. The elevated Cd–B in areas near the mine relative to the other areas suggested the potential adverse health effects of Cd and/or the interaction of Pb and Cd. A significant association of metal levels with clinical parameters also indicated the effects of metal exposure on hematopoietic, hepatic, and renal systems.

Nitrate-N-mediated toxicological responses of Scenedesmus acutus and Daphnia pulex to cadmium, arsenic and their binary mixture (Cd/Asmix) at environmentally relevant concentrations

Several biomarkers used for ecological risk assessment have been established for single contaminant toxicity, many of which are less predictive of the influence of media and/or dietary nutrients on toxicity outcomes of contaminant mixtures. In this study, we investigate toxicological responses and life traits of Scenedesmus acutus and Daphnia pulex to heavy metals (cadmium-Cd, arsenic-As, binary mixture-Cd/Asmix) in media and diets with varied nutrient (nitrate-N) conditions (low-LN, median-MN, optimum−COMBO). Results showed that nitrate-N-mediated metal inhibitory effects on growth and productivity of primary producer (S. acutus) were significantly interactive (p < 0.05; effect size, ƞ2≤56 %). Cadmium toxicities (Cd-IC50s) in S. acutus were 1.2×, 5.3×, and 4.3× As-IC50s in LN, MN and COMBO media, respectively, while mixture (Cd/Asmix) toxicities were synergistic in MN medium and partial additivity in COMBO and LN media. Nitrate-N and metal exposure effects on S. acutus nutrient stoichiometry, metal uptake and bioaccumulation were significantly interactive (p < 0.05, ƞ2≤100 %). Moreover, survival of primary consumer (D. pulex) was significantly impaired by single and mixed dietary-metal exposures with greater effect under LN condition coupled with significant interactive effects on reproductive capacity (p < 0.05, ƞ2≤21.2 %) but not on swimming activity. We recommend that nitrate-N-mediated metal exposure effects/toxicity in bioindicator species should be considered during ecological risk assessments.

Adaptation and Growth of Botryococcus braunii on Acid Mine Drainage

Phycoremediation of acid mine drainage (AMD) is an alternative to AMD treatment but has limited applications. The obstacle in the application of AMD phycoremediation is that the characteristic of wastewater which limits the growth of microalgae, where AMD has a high metal content and low pH. In this study, Botryococcus braunii was cultured on media with variations in the addition of AMD of (v/v) 0%, 2.5%, 3%, 3.5%, 4% and had a pH of 7.2, 5.6, 5.1, 4.8, 4.3, respectively, on the photobioreactor. Botryococcus braunii growth rate was analyzed, as well as the effect of metal exposure and pH variations on the growth of Botryococcus braunii. Botryococcus braunii showed different growth rates, sequentially from the highest rate in the media with addition of AMD (v/v) 2.5%, 3%, 0%, 3.5%, 4% is 1.403 d-1 ,1.374 d-1 ,0.0862 d-1 ,0.0738 d-1 , and 0.0616 d-1 . It is known that the highest growth rate of Botryococcus braunii is obtained in media with 2.5% (v/v) AMD with an initial pH of 5.6, and Fe and Mn concentrations of 2.15 mg.L-1 and 0.62 mg.L-1 , respectively. It is also known the ability of Botryococcus braunii to adapt to acidic conditions with Fe and Mn content, where Botryococcus braunii plays a role in increasing media pH and is able to remove Fe and Mn with the highest values of 84.28% and 98%, respectively.

Bone Remodeling and Metals Exposure during Pregnancy: Results from Progress Cohort

Background: Environmental exposure to metals has been associated with decreased bone density and higher risk of fracture mainly among premenopausal women and older adults. Metals such as lead (Pb) and cadmium (Cd) interfere with calcium incorporation into the bone cells leading to low bone density. However, little is known about the effects of metals exposure on bone remodeling during pregnancy, a window of susceptibility to the toxic effects of metals.Objective: The aim of this study was to assess concurrent exposure to metals [Pb, Cd, chromium (Cr) and arsenic (As)] and bone remodeling at radius during second and third trimester of pregnancy.Methods: We studied 1,054 mothers from PROGRESS cohort (Programming Research in Obesity, Growth, Environment and Social Stress). We measured BMD at radius by ultrasound and metals exposure by inductively coupled plasma during second and third trimesters of pregnancy. We generated linear mixed models to assess associations between metals exposure and z-scores at radius during second and third trimesters of pregnancy. Additionally, at each trimester of pregnancy, we assessed associations between metals exposures and z-scores using simple linear regression models.Results: At third trimester of pregnancy, Pb and Cr were associated with lower z-score at radius [for Pb (estimate: -0.89; 95% CI: -1.54, -0.24) and for Cr (estimate:-0.70; 95% CI: -1.37, -0.34)] in adjusted models. Similarly, we observed a decreasing trend in z-score at radius associated with Pb and Cr exposure during pregnancy, although it was not statistically significant. Overall, we did not observe associations between Cd or As and z-scores during pregnancy.Conclusions: Lead and chromium exposure during the third trimester of pregnancy might decrease bone remodeling at radius. Further studies should be conducted to assess bone remodeling at different anatomic sites in relation to metals exposure during pregnancy.

Effects of cadmium, manganese, and lead on locomotor activity and neurexin 2a expression in zebrafish.

The synaptic adhesion protein Neurexin 2a (Nrxn2a) plays a key role in neuronal development and is associated with cognitive functioning and locomotor behavior. Although low-level metal exposure poses a potential risk to the human nervous system, especially during the developmental stages, little is known about the effects of metal exposures on nrxn2a expression during embryonic development. We therefore exposed wild-type zebrafish embryos/larvae to cadmium (CdCl2 ), manganese (MnCl2 ), and lead ([CH3 COO]2 Pb), to determine their effect on mortality, malformation, and hatching rate. Concentrations of these metals in zebrafish were detected by inductively coupled plasma mass spectrometry analysis. Locomotor activity of zebrafish larvae was analyzed using a video-track tracking system. Expression of nrxn2a was assessed by in situ hybridization and quantitative polymerase chain reaction. The results showed that mortality, malformation, and bioaccumulation increased as the exposure dosages and duration increased. Developmental exposure to these metals significantly reduced larval swim distance and velocity. The nrxn2aa and nrxn2ab genes were expressed in the central nervous system and downregulated by almost all of the 3 metals, especially Pb. These data demonstrate that exposure to metals downregulates nrxn2a in the zebrafish model system, and this is likely linked to concurrent developmental processes. Environ Toxicol Chem 2017;36:2147-2154. © 2017 SETAC.

Copper tolerant ecotypes of Heliscus lugdunensis differ in their ecological function and growth

Metal tolerance in aquatic hyphomycetes varies with the level of pollution at the fungal isolation site. While the focus of previous research has been on the effects of metal exposure on interspecies diversity, intraspecies variation of aquatic hyphomycetes remains largely unexplored. In this study we investigate the effects of Cu on ecological function (litter decomposition) and growth of five strains of Heliscus lugdunensis, isolated from contaminated and un-contaminated streams, in order to examine whether strains are expressed as ecotypes with distinct growth and functional signatures in response to metal stress. When exposed to Cu, strains of H. lugdunensis differed significantly in their litter decomposition and reproductive activity (sporulation) as well as mycelial growth, corresponding to the Cu concentrations at their isolation site. Strains isolated from sites with high Cu concentrations induced the highest litter decomposition or invested most in growth. This study broadens our understanding of Cu pollution in streams, which may lead to evolved adaptations of Cu tolerant ecotypes of H. lugdunensis differing in their ecological function, behaviour and morphology when exposed to metals.

Effect of metal exposure in rats: amelioration by diallylsulphide

The effect of diallylsuphide (DAS) was investigated on mercuric chloride (HgCl2)-induced renal damage in rats. Oral administration of DAS (200 mg/kg) effectively inhibited the levels of antioxidant enzymes as compared to HgCl2-treated group. Exposure to HgCl2 also resulted in an increase in the uric acid, creatinine and blood urea nitrogen levels. A significant decrease in the uric acid, creatinine and blood urea nitrogen was also observed in DAS-pre-treated HgCl2 group. The results suggest that DAS possesses significant potential as nephroprotective agent.

Effects of metal exposure on motor neuron development, neuromasts and the escape response of zebrafish embryos

Low level metal contaminations are a prevalent issue with often unknown consequences for health and the environment. Effect-based, multifactorial test systems with zebrafish embryos to assess in particular developmental toxicity are beneficial but rarely used in this context. We therefore exposed wild-type embryos to the metals copper (CuSO4), cadmium (CdCl2) and cobalt (CoSO4) for 72h to determine lethal as well as sublethal morphological effects. Motor neuron damage was investigated by immunofluorescence staining of primary motor neurons (PMNs) and secondary motor neurons (SMNs). In vivo stainings using the vital dye DASPEI were used to quantify neuromast development and damage. The consequences of metal toxicity were also assessed functionally, by testing fish behavior following tactile stimulation. The median effective concentration (EC50) values for morphological effects 72h post fertilization (hpf) were 14.6mg/L for cadmium and 0.018mg/L for copper, whereas embryos exposed up to 45.8mg/L cobalt showed no morphological effects. All three metals caused a concentration-dependent reduction in the numbers of normal PMNs and SMNs, and in the fluorescence intensity of neuromasts. The results for motor neuron damage and behavior were coincident for all three metals. Even the lowest metal concentrations (cadmium 2mg/L, copper 0.01mg/L and cobalt 0.8mg/L) resulted in neuromast damage. The results demonstrate that the neuromast cells were more sensitive to metal exposure than morphological traits or the response to tactile stimulation and motor neuron damage.

Low-temperature biosynthesis of fluorescent semiconductor nanoparticles (CdS) by oxidative stress resistant Antarctic bacteria

Bacterial biosynthesis of nanoparticles represents a green alternative for the production of nanostructures with novel properties. Recently, the importance of antioxidant molecules on the biosynthesis of semiconductor fluorescent nanoparticles (quantum dots, QDs) by mesophilic bacteria was reported. The objective of this work was the isolation of psychrotolerant, oxidative stress-resistant bacteria from Antarctica to determine their ability for biosynthesizing CdS QDs at low temperatures. QDs biosynthesis at 15°C was evaluated by determining their spectroscopic properties after exposing oxidative-stress resistant isolates identified as Pseudomonas spp. to Cd2+ salts. To characterize the QDs biosynthetic process, the effect of metal exposure on bacterial fluorescence was determined at different times. Time-dependent changes in fluorescence color (green to red), characteristic of QDs, were observed. Electron microscopy analysis of fluorescent cells revealed that biosynthesized nanometric structures localize at the cell periphery. QDs were purified from the bacterial isolates and their fluorescence properties were characterized. Emission spectra displayed classical CdS peaks when excited with UV light. Thiol content, peroxidase activity, lipopolysaccharide synthesis, metabolic profiles and sulfide generation were determined in QDs-producing isolates. No relationship between QDs production and cellular thiol content or peroxidase activity was found. However, sulfide production enhanced CdS QDs biosynthesis. In this work, the use of Antarctic psychrotolerant Pseudomonas spp. for QDs biosynthesis at low temperature is reported for the first time.