Cadmium as a male reproductive toxicant and natural and non-natural ways to tackle it: a review.

Cadmium (Cd) is a naturally occurring environmental pollutant, a toxic substance that causes oxidative stress. According to epidemiological studies, the data suggested that environmental and occupational Cd exposure may be related to several diseases and severe testicular damage. However, studies are going on to explore the mechanism of Cd-induced male reproductive toxicity and its treatment strategies. Currently, researchers are focusing on naturally occurring bioactive compounds, plant extracts, and biochemical, which have better efficacy, less toxicity, and high bioavailability. This review focuses on the mechanistic effect of Cd on testicular toxicity and different categories of compounds having a beneficial impact on Cd-induced male reproductive toxicity. Some potent bioactive antioxidants are quercetin, caffeic acid phenethyl ester, cyanidin-3-O-glucoside, curcumin, and silymarin. In comparison, plant extracts are Costus afer leaf methanol extract, methanol root extract of Carpolobia lutea, red carrot methanolic extract, Panax ginseng extract, and biochemicals including melatonin, progesterone, glutamine, L-carnitine, and selenium. Advanced and more detailed studies are needed on these compounds to explore their mechanism in attenuating Cd-induced testicular toxicity and can be potential therapeutics in the future.

Barbary sheep tissues as bioindicators of radionuclide and stabile element contamination in Croatia: exposure assessment for consumers.

Muscle, liver and kidney of 21 Barbary sheep (Ammotragus lervia) from Mosor Mountain, Croatia, were sampled to quantify the activity of caesium and potassium radionuclides and five toxic and ten essential stabile elements in order to establish reference values for this species and to evaluate the potential of Barbary sheep tissues to reflect environmental pollution. We also assessed seasonal diet (botanical composition and dry matter content) of Barbary sheep based on analyses of a rumen content of culled animals. None of the 19 plant species (mostly grasses) identified as part of the Barbary sheep diet is known as a stabile element or radionuclide hyperaccumulator. Measured levels reflected low environmental pollution with arsenic, cadmium, mercury and lead, with levels generally less than those reported for wild herbivorous ungulates. Methodological differences (detection limit of elements in muscle) were shown to hamper interpretation and comparison of the Toxic Contamination Index (TCI) values with those published for other species. There was no homeostasis disturbance of trace elements in Barbary sheep, either due to inadequate intake via food or as an adverse effect due to a high toxic metal(loid) burden. Consumption of the muscle and liver of wild Barbary sheep can be considered safe for the health of adult consumers regarding toxic metal(loid)s and radioactive caesium, though the liver should be avoided as a food item in vulnerable population groups due to the possible adverse effects of cadmium and lead. Otherwise, muscle and liver are a rich source of copper, iron, selenium and zinc for consumers and, as such, can benefit the overall dietary intake of essential elements.

Enantioselective Phytotoxicity and the Relative Mechanism of Current Chiral Herbicides.

BACKGROUND: Regardless of the achievable of chiral switch, most of the chiral nature agrochemical is still sold as racemate or enantiomer-enriched pesticides. Herbicides, accounted for a large proportion in pesticide market, are of great concern due to the frequent occurrence in environment and the structure selective phyto-biochemical impact on plants. METHODS: We give a systematic search on the literature database and included approximately 50 papers which were related to the review. We do careful categories for the chiral herbicides according to their structure and listed out the acute phytotoxicity endpoints. The potential mechanism for the enantioselective toxicity was concluded into 5 main points. RESULTS: The enantiomer-specific toxicity on plant growth and flowers are limited on phenoxyalkanoic acid herbicide, aryloxyphenoxypropanoic acid, imidazolinone herbicide, and acetamide pesticide. Data available on the potential mechanism explanation of enantioselective phytotoxicity has been concerned on the genetic transcription, oxidative stress, and photosynthesis disruption, etc. A comparison between the two enantiomers' enantioselective effects identified an organ-specific and species-specific phenomenon for several herbicides. Moreover, a more herbicidal activity enantiomer is also displayed the more toxicity than its antipode. CONCLUSION: The review elucidated a paucity of information on the enantioselective effect research on various types of plants at the different life stages. It appealed us to conduct a more holistic approach to balance the benefit between herbicidal activity and phytotoxicity when try to develop an enantio-pure herbicide.

Arsenic methylation by an arsenite S-adenosylmethionine methyltransferase from Spirulina platensis.

Arsenic-contaminated water is a serious hazard for human health. Plankton plays a critical role in the fate and toxicity of arsenic in water by accumulation and biotransformation. Spirulina platensis (S. platensis), a typical plankton, is often used as a supplement or feed for pharmacy and aquiculture, and may introduce arsenic into the food chain, resulting in a risk to human health. However, there are few studies about how S. platensis biotransforms arsenic. In this study, we investigated arsenic biotransformation by S. platensis. When exposed to arsenite (As(III)), S. platensis accumulated arsenic up to 4.1mg/kg dry weight. After exposure to As(III), arsenate (As(V)) was the predominant species making up 64% to 86% of the total arsenic. Monomethylarsenate (MMA(V)) and dimethylarsenate (DMA(V)) were also detected. An arsenite S-adenosylmethionine methyltransferase from S. platensis (SpArsM) was identified and characterized. SpArsM showed low identity with other reported ArsM enzymes. The Escherichia coli AW3110 bearing SparsM gene resulted in As(III) methylation and conferring resistance to As(III). The in vitro assay showed that SpArsM exhibited As(III) methylation activity. DMA(V) and a small amount of MMA(V) were detected in the reaction system within 0.5hr. A truncated SpArsM derivative lacking the last 34 residues still had the ability to methylate As(III). The three single mutants of SpArsM (C59S, C186S, and C238S) abolished the capability of As(III) methylation, suggesting the three cysteine residues are involved in catalysis. We propose that SpArsM is responsible for As methylation and detoxification of As(III) and may contribute to As biogeochemistry.

Vitamin D, Essential Minerals, and Toxic Elements: Exploring Interactions between Nutrients and Toxicants in Clinical Medicine.

In clinical medicine, increasing attention is being directed towards the important areas of nutritional biochemistry and toxicant bioaccumulation as they relate to human health and chronic disease. Optimal nutritional status, including healthy levels of vitamin D and essential minerals, is requisite for proper physiological function; conversely, accrual of toxic elements has the potential to impair normal physiology. It is evident that vitamin D intake can facilitate the absorption and assimilation of essential inorganic elements (such as calcium, magnesium, copper, zinc, iron, and selenium) but also the uptake of toxic elements (such as lead, arsenic, aluminum, cobalt, and strontium). Furthermore, sufficiency of essential minerals appears to resist the uptake of toxic metals. This paper explores the literature to determine a suitable clinical approach with regard to vitamin D and essential mineral intake to achieve optimal biological function and to avoid harm in order to prevent and overcome illness. It appears preferable to secure essential mineral status in conjunction with adequate vitamin D, as intake of vitamin D in the absence of mineral sufficiency may result in facilitation of toxic element absorption with potential adverse clinical outcomes.

The effects of 3,3',4,4'-tetrabromobiphenyl on rats fed diets containing a constant level of copper and varying levels of molybdenum.

Copper (Cu) metabolism is altered in rats fed diets high in molybdenum (Mo) and low in Cu. This 10-week study was carried out to examine the effects of supplemental Mo (7.5-240 µg/g diet) on male Sprague-Dawley rats fed diets adequate in Cu (5 µg/g diet) and to determine the susceptibility of Mo-treated animals to the environmental pollutant 3,3',4,4'-tetrabromobiphenyl (TBB). After 7 weeks of dietary treatment, half of the rats in each group received a single IP injection of TBB (150 µM/kg bw), while the other half received the corn oil vehicle. Rats sacrificed at 10 weeks showed no effects of Mo on growth, feed efficiency, or selected organ or tissue weights. Dose-dependent effects on plasma Mo (0-5.1 µg/mL), plasma Cu (0.95-0.20 µg/mL), and bone Cu (3.4-10 µg/g) in control through the high dose were found. Cu sequestration in the bone of Mo-treated rats is a new finding. TBB treatment resulted in dramatic weight loss and loss of absolute organ mass. Relative organ weights were increased, except for the thymus. TBB altered the concentrations of certain amino acids. Compared to control rats, this polybrominated biphenyl congener significantly decreased plasma Cu and ceruloplasmin at higher concentrations of dietary Mo and promoted the process of plasma Cu decrease by Mo, suggesting a combined effect.

Mercury capture into biogenic amorphous selenium nanospheres produced by mercury resistant Shewanella putrefaciens 200.

Shewanella putrefaciens 200, resistant to high concentration of Hg(II), was selected for co-removal of mercury and selenium from aqueous medium. Biogenic Hg(0) reduced from Hg(II) by S. putrefaciens 200 was captured into extracellular amorphous selenium nanospheres, resulting in the formation of stable HgSe nanoparticles. This bacterial reduction could be a new strategy for mercury removal from aquatic environments without secondary pollution of mercury methylation or Hg(0) volatilization.

Coal fly ash basins as an attractive nuisance to birds: parental provisioning exposes nestlings to harmful trace elements.

Birds attracted to nest around coal ash settling basins may expose their young to contaminants by provisioning them with contaminated food. Diet and tissues of Common Grackle (Quiscalus quiscala) nestlings were analyzed for trace elements to determine if nestlings were accumulating elements via dietary exposure and if feather growth limits elemental accumulation in other tissues. Arsenic, cadmium, and selenium concentrations in ash basin diets were 5× higher than reference diets. Arsenic, cadmium, and selenium concentrations were elevated in feather, liver, and carcass, but only liver Se concentrations approached levels of concern. Approximately 15% of the total body burden of Se, As, and Cd was sequestered in feathers of older (>5 days) nestlings, whereas only 1% of the total body burden of Sr was sequestered in feathers. Feather concentrations of only three elements (As, Se, and Sr) were correlated with liver concentrations, indicating their value as non-lethal indicators of exposure.

Bioaccumulation of organic contaminants in humans: a multimedia perspective and the importance of biotransformation.

Bioaccumulation is an important component of the exposure hazard assessment and risk assessment of organic chemicals. Screening criteria for chemical hazard used in national and international regulations are based on the paradigm that partitioning properties are the primary chemical determinants of bioaccumulation. We use a holistic multimedia perspective to evaluate the partitioning property paradigm with respect to assessing human bioaccumulation. Multimedia bioaccumulation factors (mmBAFs) for humans were modeled for hypothetical chemicals with a wide range of physical-chemical properties. Varying partitioning properties over 12 orders of magnitude (a plausible range for nonionizing organics) resulted in only modest changes in mmBAFs (a factor of ∼ 10) for all but very volatile or hydrophilic chemicals. In contrast, varying biotransformation rate constants over 6 orders of magnitude resulted in substantial differences in mmBAFs (greater than a factor of 10(9)). Our model results are supported by empirical observations of well characterized pollutants, which demonstrate that chemicals with similar partitioning properties can have very different bioaccumulation behavior. Susceptibility to biotransformation clearly determines bioaccumulation in humans for many chemicals. We conclude that a holistic multimedia perspective for bioaccumulation assessment is necessary to develop regulations, criteria, and policies that are protective of human health and the environment.

A thermodynamically-based model for predicting microbial growth and community composition coupled to system geochemistry: Application to uranium bioreduction.

'Bioimmobilization' of redox-sensitive heavy metals and radionuclides is being investigated as a way to remediate contaminated groundwater and sediments. In one approach, growth-limiting substrates are added to the subsurface to stimulate the activity of targeted groups of indigenous microorganisms and create conditions favorable for the microbially-mediated reductive precipitation ('bioreduction') of targeted contaminants. We present a theoretical framework for modeling this process that modifies conventional geochemical reaction path modeling to include thermodynamic descriptions for microbial growth and may be called biogeochemical reaction path modeling. In this approach, the actual microbial community is represented by a synthetic microbial community consisting of a collection of microbial groups; each with a unique growth equation that couples a specific pair of energy yielding redox reactions. The growth equations and their computed standard-state free energy yields are appended to the thermodynamic database used in conventional geochemical reaction path modeling, providing a direct coupling between chemical species participating in both microbial growth and geochemical reactions. To compute the biogeochemical reaction paths, growth substrates are reacted incrementally with the defined geochemical environment and the coupled equations are solved simultaneously to predict reaction paths that display changing microbial biomass, community composition (i.e. the fraction of total biomass in each microbial group), and the aqueous and mineral composition of the system, including aqueous speciation and oxidation state of the targeted contaminants. The approach, with growth equations derived from the literature using well-known bioenergetics principles, was used to predict the results of a laboratory microcosm experiment and an in situ field experiment that investigated the bioreduction of uranium. Predicted effects of ethanol or acetate addition on uranium concentration and speciation, major ion geochemistry, mineralogy, microbial biomass and community composition were in qualitative agreement with experimental observations although the available data precluded rigorous model testing. While originally developed for use in better understanding of bioimmobilization of heavy metals and radionuclides, the modeling approach is potentially useful for exploring the coupling of microbial growth and geochemical reactions in a variety of other basic and applied biotechnology research settings.

Metals in medicine.

The effects of toxicant metals on human health have been reported in peer-reviewed literature with increasing frequency. Toxicant metals are present in many diseases of aging, especially vascular diseases. Toxicant metals are a natural environmental phenomenon as well as a byproduct of industrialization. The historical experience of toxicologists who treated individuals poisoned by acutely toxicant metals is waning; very few of these cases have been reported during the past 30 years in the US. Researchers with a special interest in clinical metal toxicology have noticed a clinical correlation between metal detoxification by chelation therapy and clinical improvement of vascular diseases. Chelation therapy currently is being tested by the National Institutes of Health (NIH) for post-myocardial infarction patients in the Trial to Assess Chelation Therapy (TACT). This article's author is on the NIH Data and Safety Management Board of that study. He was asked to write this review article and include an update on the clinical, environmental, historical, and scientific elements of this expanding field. This article reviews toxicant metals in the environment and their potential health consequences.

Molecular biomarkers and adaptation to environmental stress in moon jelly (Aurelia spp.).

We describe a strategy that identifies molecular biomarkers and links the study of abiotic stress to evolutionary history. By utilizing the moon jellyfish Aurelia spp. as a model, we identified genes differentially regulated in response to the chemical stressor tributyltin by means of complementary DNA subtraction analyses. Expression of 3 out of 25 identified candidate genes, one oxidative stress gene, one heat shock (hsp70) gene, and one GTP-binding gene, was quantified under laboratory conditions and in field tests using semiquantitative reverse transcriptase polymerase chain reaction. Differential expression patterns were found following exposure to tributyltin and temperature treatments. The findings suggest that the identified genes are involved in response to chemical as well as heat- induced stress and may serve as biomarkers for monitoring marine habitats. Gene regulatory patterns combined with phylogenetic inferences of the hsp70 gene support a possible role of ecologically driven divergence within the genus Aurelia. We show that added information on genetic variability can raise the predictive power of molecular biomarkers in studies of individual stress response.

Incompatibilities of chemicals.

Chemical incompatibilities are potentially significant problems where hazardous chemicals are found. A number of chemical segregation systems have been developed which provide recommendations for the separation of incompatible chemicals. Three segregation systems were identified in this study: the UN Dangerous Goods system (which uses physical hazard as the main reason for segregation and has 14 categories), the US CHRIS system (which uses chemical reactivity and has 24 categories) and a third system which uses environmental risks (and has 25 categories). These systems were combined. Merging of each system was initially problematic, but became considerably easier once certain characteristics had been defined (such as flammability or water incompatibility). This gave a final merged incompatibility table containing 100 different segregation groups. This research study showed that it was possible to combine different segregation systems based on different criteria and that more comprehensive segregation systems can be developed. These can be of use in the decision-making process about where groups of chemicals may be used, and during the use of chemicals, where chemicals should not be combined. The use of more comprehensive segregation systems will also assist in developing proper measures for their control.

Fate of explosives and their metabolites in bioslurry treatment processes.

Microcosm tests simulating bioslurry reactors with 40% soil content, containing high concentrations of TNT and/or RDX, and spiked with either [14C]-TNT or [14C]-RDX were conducted to investigate the fate of explosives and their metabolites in bioslurry treatment processes. RDX is recalcitrant to indigenous microorganisms in soil and activated sludge under aerobic conditions. However, soil indigenous microorganisms alone were able to mineralize 15% of RDX to CO2 under anaerobic condition, and supplementation of municipal anaerobic sludge as an exogenous source of microorganisms significantly enhanced the RDX mineralization to 60%. RDX mineralizing activity of microorganisms in soil and sludge was significantly inhibited by the presence of TNT. TNT mineralization was poor (< 2%) and was not markedly improved by the supplement of aerobic or anaerobic sludge. Partitioning studies of [14C]-TNT in the microcosms revealed that the removal of TNT during the bioslurry process was due mainly to the transformation of TNT and irreversible binding of TNT metabolites onto soil matrix. In the case of RDX under anaerobic conditions, a significant portion (35%) of original radioactivity was also incorporated into the biomass and bound to the soil matrix.