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News Article | May 5, 2017
Site: www.eurekalert.org

Supplements containing arsenic have been banned in the European Union since 1999 and in North America since 2013. In many countries they are still added to poultry feed to prevent parasitic infection and promote weight gain. In the journal Angewandte Chemie, scientists have now demonstrated that the danger to human health may be greater than previously thought because the metabolic breakdown of these compounds in chickens occurs via intermediates that are significantly more toxic than the initial additives. Roxarsone (3-nitro-4-hydroxyphenylarsonic acid, "Rox") is a common feed supplement that is only slightly toxic to those animals that have been tested. However, we do not yet have enough knowledge about which arsenic-containing metabolites are found in treated chickens and what risks these pose to human health. The toxicity of arsenic-containing species depends strongly on the type of compound and can vary by orders of magnitude. In a study of 1600 chickens under controlled feeding, a team headed by Bin Hu at Wuhan University in China and X. Chris Le at the University of Alberta in Canada analyzed liver samples from birds treated with Rox. Previously, these researchers found a number of different arsenic-containing species in chicken livers, breast meat, and waste. By using various mass spectrometric and chromatographic methods, they have now been able to identify three additional compounds. These compounds are Rox derivatives that have an additional methyl group (-CH3) on their arsenic atom. The three methylated compounds make up about 42 % of the total arsenic compounds found in the chicken livers. What causes this methylation? The researchers are pointing to the enzyme arsenic methyltransferase (As3MT), which is also involved in the human metabolism of arsenic. However, this enzyme only methylates trivalent arsenic, whereas Rox and its derivatives contain arsenic in its pentavalent form. Tests with reduced versions of Rox have shown that the process of breaking down Rox occurs via trivalent intermediates. Tests with cell cultures have shown that these species are 300 to 30,000 times as toxic as Rox derivatives with pentavalent arsenic. It remains to be determined whether and at what concentrations these highly toxic intermediates occur in treated chickens. In the poultry industry, Rox supplementation is usually halted five days before slaughter. Liver samples taken after this interval still contained residues of arsenic compounds at a concentration that--at least if the chicken liver is consumed--could be alarming. The researchers recommend an assessment of the extent of human exposure to various arsenic compounds to determine whether feed containing arsenic is not more problematic for human health than previously thought. Dr. Chris Le is Distinguished University Professor and Director of the Analytical and Environmental Toxicology Division at the University of Alberta. He is Fellow of the Royal Society of Canada (Academy of Science) and Canada Research Chair in Bio-analytical Technology and Environmental Health.


News Article | May 5, 2017
Site: www.eurekalert.org

For many, experience with Daphnia, commonly known as water fleas, ends in high school. The organism is often used for science experiments exploring water toxicity, because of its sensitivity to environmental factors. But the tiny, transparent microcrustaceans have been studied intensively for more than 150 years, and new research published and featured on the cover of the journal G3 reveals scientists can now take a closer look at its genome. Researchers have completed a new and improved genome sequence of Daphnia pulex (D. pulex), providing a clearer roadmap of the organism's genome so they can identify the genes and pathways that make this organism so successful in freshwater ecosystems. Populations of Daphnia, barely visible to the naked eye, can be found in virtually every standing body of water on the planet, including Antarctica. They evolve quickly and are masters of responding to the conditions in their environment. Sensing the chemical cues of nearby predators, some species of Daphnia develop elaborate defensive structures such as spines and helmets that make them harder to eat. While scientists have gained a thorough understanding of what these tiny water fleas do to adapt to varying conditions, they don't yet know how they do it. "That's why a system like this is so powerful," said Michael E. Pfrender, director of the Genomics & Bioinformatics Core Facility and associate professor in the Department of Biological Sciences and the Environmental Change Initiative at the University of Notre Dame. "We need this genomic infrastructure to add to the ecological context we already have to gain a better understanding of how Daphnia adapt. Because we have an improved genome sequence, we can get a more accurate catalog of genes and when thinking about response to the environment and chemical cues, it's the turning on and off of genes and pathways that's important. The picture is much more complete than it was before." Calling it the "Portland Arch" genome after the Indiana Nature Preserve where the Daphnia was collected, the new assembly comes six years after the first sequence of D. pulex in 2011. The current study describes how scientists used the latest technology as part of a thorough and methodical process the result of which led to the identification of 18,440 genes. D. pulex plays a vital role in Earth's ecology. Feeding off of algae and phytoplankton in standing freshwaters, they are the primary grazer in those environments, the "cows of lakes," said Pfrender. They're also primary forage, transferring all of that energy to the fish that eat them. By understanding how species of Daphnia respond to toxic elements like industrial contaminants, toxic algae blooms or thermal stress, scientists can look at how environmental changes caused by agriculture and road runoff or warming temperatures and climate change could impact populations in lakes, rivers and standing bodies of water. "What happens to this vital part of the ecosystem when conditions change very rapidly? What genes allow some populations to cope with these changes while others fail?" Pfrender said. "That's what we want to find out. This genome sequence provides the toolkit." Co-authors of the study include Pfrender, Jacqueline Lopez and Brent Harker of the Notre Dame Genomics and Bioinformatics Core Facility; Zhiqiang Ye, Ken Spitze, Xiaoqian Jiang, Matthew S. Ackerman and Michael Lynch at the Department of Biology at Indiana University; Sen Xu at the Department of Biology at Indiana University and the University of Texas at Arlington; Jana Asselman, Laboratory for Environmental Toxicology at Ghent University; R. Taylor Raborn at the Department of Biology and School of Informatics and Computing at Indiana University; and W. Kelley Thomas and Jordan Ramsdell at the Hubbard Center for Genome Studies at the University of New Hampshire. The study was funded through a grant from the National Institutes of Health to Michael Lynch at Indiana University, Bloomington and Notre Dame Research.


News Article | December 8, 2016
Site: www.eurekalert.org

Evolution is working hard to rescue some urban fish from a lethal, human-altered environment, according to a study led by the University of California, Davis, and published Dec. 9 in the journal Science. While environmental change is outpacing the rate of evolution for many other species, Atlantic killifish living in four polluted East Coast estuaries turn out to be remarkably resilient. These fish have adapted to levels of highly toxic industrial pollutants that would normally kill them. The killifish is up to 8,000 times more resistant to this level of pollution than other fish, the study found. While the fish is not commercially valuable, it is an important food for other species and an environmental indicator. What makes Atlantic killifish so special? Extremely high levels of genetic variation, higher than any other vertebrate -- humans included -- measured so far. The more genetic diversity, the faster evolution can act. That's one reason why insects and weeds can quickly adapt and evolve to resist pesticides, and why pathogens can evolve quickly to resist drugs created to destroy them. Not all species are so lucky, however. "Some people will see this as a positive and think, 'Hey, species can evolve in response to what we're doing to the environment!'" said lead author Andrew Whitehead, associate professor in the UC Davis Department of Environmental Toxicology. "Unfortunately, most species we care about preserving probably can't adapt to these rapid changes because they don't have the high levels of genetic variation that allow them to evolve quickly." EVOLUTION A POLLUTION SOLUTION? NOT FOR MOST OF US The scientists sequenced complete genomes of nearly 400 Atlantic killifish from polluted and nonpolluted sites at New Bedford Harbor in Massachusetts; Newark Bay, New Jersey; Connecticut's Bridgeport area; and Virginia's Elizabeth River. The sites have been polluted since the 1950s and 1960s by a complex mixture of industrial pollutants including dioxins, heavy metals, hydrocarbons and other chemicals. The team's genetic analysis suggests that the Atlantic killifish's genetic diversity make them unusually well positioned to adapt to survive in radically altered habitats. At the genetic level, the tolerant populations evolved in highly similar ways. This suggests that these fish already carried the genetic variation that allowed them to adapt before the sites were polluted, and that there may be only a few evolutionary solutions to pollution. The study lays the groundwork for future research that could explore which genes confer tolerance of specific chemicals. Such work could help better explain how genetic differences among humans and other species may contribute to differences in sensitivity to environmental chemicals. "If we know the kinds of genes that can confer sensitivity in another vertebrate animal like us, perhaps we can understand how different humans, with their own mutations in these important genes, might react to these chemicals," Whitehead said. "This study shows that different populations of Atlantic killifish exposed to toxic pollution evolve tolerance to that pollution through changes in one molecular pathway," said George Gilchrist, program director in the National Science Foundation's Division of Environmental Biology, which funded the study along with the National Institute of Environmental Health Sciences. "This pathway may play a similar role in many animals exposed to pollutants, with slightly different adaptations in response to different toxicants." The study's co-authoring institutions include the United States Department of Agriculture, U.S. Environmental Protection Agency, Washington University School of Medicine, University of Birmingham, Indiana University, Woods Hole Oceanographic Institution, and University of Miami.


News Article | December 8, 2016
Site: phys.org

While environmental change is outpacing the rate of evolution for many other species, Atlantic killifish living in four polluted East Coast estuaries turn out to be remarkably resilient. These fish have adapted to levels of highly toxic industrial pollutants that would normally kill them. The killifish is up to 8,000 times more resistant to this level of pollution than other fish, the study found. While the fish is not commercially valuable, it is an important food for other species and an environmental indicator. What makes Atlantic killifish so special? Extremely high levels of genetic variation, higher than any other vertebrate—humans included—measured so far. The more genetic diversity, the faster evolution can act. That's one reason why insects and weeds can quickly adapt and evolve to resist pesticides, and why pathogens can evolve quickly to resist drugs created to destroy them. Not all species are so lucky, however. "Some people will see this as a positive and think, 'Hey, species can evolve in response to what we're doing to the environment!'" said lead author Andrew Whitehead, associate professor in the UC Davis Department of Environmental Toxicology. "Unfortunately, most species we care about preserving probably can't adapt to these rapid changes because they don't have the high levels of genetic variation that allow them to evolve quickly." Evolution a pollution solution? Not for most of us The scientists sequenced complete genomes of nearly 400 Atlantic killifish from polluted and nonpolluted sites at New Bedford Harbor in Massachusetts; Newark Bay, New Jersey; Connecticut's Bridgeport area; and Virginia's Elizabeth River. The sites have been polluted since the 1950s and 1960s by a complex mixture of industrial pollutants including dioxins, heavy metals, hydrocarbons and other chemicals. The team's genetic analysis suggests that the Atlantic killifish's genetic diversity make them unusually well positioned to adapt to survive in radically altered habitats. At the genetic level, the tolerant populations evolved in highly similar ways. This suggests that these fish already carried the genetic variation that allowed them to adapt before the sites were polluted, and that there may be only a few evolutionary solutions to pollution. The study lays the groundwork for future research that could explore which genes confer tolerance of specific chemicals. Such work could help better explain how genetic differences among humans and other species may contribute to differences in sensitivity to environmental chemicals. "If we know the kinds of genes that can confer sensitivity in another vertebrate animal like us, perhaps we can understand how different humans, with their own mutations in these important genes, might react to these chemicals," Whitehead said. "This study shows that different populations of Atlantic killifish exposed to toxic pollution evolve tolerance to that pollution through changes in one molecular pathway," said George Gilchrist, program director in the National Science Foundation's Division of Environmental Biology, which funded the study along with the National Institute of Environmental Health Sciences. "This pathway may play a similar role in many animals exposed to pollutants, with slightly different adaptations in response to different toxicants." More information: "The genomic landscape of rapid repeated evolutionary adaptation to toxic pollution in wild fish," Science, science.sciencemag.org/cgi/doi/10.1126/science.aah4993


News Article | December 9, 2016
Site: www.eurekalert.org

A new report identifies the genetic mechanism responsible for evolutionary adaptation to toxic pollution observed in wild Atlantic killifish populations. The Atlantic killifish is renowned for its ability to tolerate large fluctuations in temperature, salinity and oxygen levels. However, its rapid adaptation to the normally lethal levels of toxic pollution found in some urban estuaries in the US is unusual, even for such a hardy species. A report, published today in the journal Science by a collaborative team of research institutions including the University of Birmingham, found that some populations of killifish are up to 8,000 times more resistant than others to highly toxic industrial pollutants such as dioxins, heavy metals and hydrocarbons. The team analysed the genomes of four wild populations of pollution-tolerant killifish compared with four non-tolerant populations, to identify the mechanism behind this adaptation. They found that the genes responsible for the trait were those involved in the aryl hydrocarbon receptor (AHR) signalling pathway, which combined with observations of desensitisation of this pathway in tolerant populations, led them to conclude that the AHR pathway is a key target of natural selection. The team also showed that the potentially negative effects of desensitisation of the AHR pathway were ameliorated through compensatory adaptations in terms of cell cycle regulation and immune system function. This, combined with the diversity of pollutants present in estuaries, results in a relatively complex adaptive genotype in wild populations compared to that of laboratory models. Professor John Colbourne, Chair of Environmental Genomics at the University of Birmingham, who oversaw the sequencing of the genomes, said: 'This report highlights the complexity of the processes involved in the adaptation of wild fish to lethal levels of environmental pollution. It also demonstrates how the DNA of populations that differ in their susceptibility to pollutants can reveal "signatures" of the adverse effects of chemicals in the environment. 'The Atlantic killifish seem particularly well-positioned to evolve the necessary adaptations to survive in radically altered habitats, because of their large population sizes and the relatively high level of DNA diversity seen in their populations.' The researchers warn that these findings should not be used to justify the harm caused by human pollution of the natural environment. Andrew Whitehead, associate professor in the UC Davis Department of Environmental Toxicology and lead author on the study, said: 'Unfortunately, most species we care about preserving probably can't adapt to these rapid changes because they don't have the high levels of genetic variation that allow them to evolve quickly.'


News Article | March 1, 2017
Site: www.eurekalert.org

A new study looks at how neonicotinoid pesticides affect wood frogs, which use surface waters in agricultural environments to breed and reproduce. Neonicotinoids are widely used insecticides that are applied to a variety of crops and are relatively persistent in the environment. The study found that some neonicotinoids may cause developmental delays in the frogs, but these are not necessarily detrimental. Additional studies are needed to investigative the direct and indirect effects of neonicotinoids on wood frogs and other amphibian populations. "The slight delay in development may not be cause for concern on its own; however, in the natural environment, additional stressors such as mixtures of pesticides, predators, or parasites can contribute to further delays," said Dr. Stacey Robinson, lead author of the Environmental Toxicology and Chemistry article. "Such cumulative stressors are important to consider in understanding the potential impact on amphibian populations."


News Article | March 1, 2017
Site: phys.org

A new study looks at how neonicotinoid pesticides affect wood frogs, which use surface waters in agricultural environments to breed and reproduce. Neonicotinoids are widely used insecticides that are applied to a variety of crops and are relatively persistent in the environment. The study found that some neonicotinoids may cause developmental delays in the frogs, but these are not necessarily detrimental. Additional studies are needed to investigative the direct and indirect effects of neonicotinoids on wood frogs and other amphibian populations. "The slight delay in development may not be cause for concern on its own; however, in the natural environment, additional stressors such as mixtures of pesticides, predators, or parasites can contribute to further delays," said Dr. Stacey Robinson, lead author of the Environmental Toxicology and Chemistry article. "Such cumulative stressors are important to consider in understanding the potential impact on amphibian populations." Explore further: Impact of pesticide on bumblebees revealed by taking experiments into the field More information: Stacey A. Robinson et al, Sublethal effects on wood frogs chronically exposed to environmentally relevant concentrations of two neonicotinoid insecticides, Environmental Toxicology and Chemistry (2017). DOI: 10.1002/etc.3739


News Article | October 26, 2016
Site: www.eurekalert.org

PENSACOLA, Fla. - Environmental contaminants such as perfluoroalkyl substances (PFASs) can be transferred from mother to offspring through the placenta and mother's milk, exposing the young mammal before and after birth. PFASs are a family of human-made chemicals, which have been used in a number of consumer products such as textiles, carpets, paper plates and food packaging because they repel grease, water and stains and are heat resistant. Since it was discovered that they pose a risk to wildlife and human health, some PFASs have been phased out of use, but they have not been universally banned. The Environmental Toxicology and Chemistry article, "Maternal Transfer of Perfluoroalkyl Substances in Hooded Seals" reports on the samples collected from lactating hooded seal mothers and their pups in West Ice, just east of Greenland. Hooded seals are particularly vulnerable to PFASs exposure as marine predators - the concentration of persistent contaminants increases with each level on the food web. They were also particularly suited for this study because they only nurse for 3-4 days, and their pup does not feed on anything other than milk during this time. Additionally, hooded seal milk is extremely energy rich, with 60-70% lipids, and PFASs are amphiphilic, which means they tend to bind to proteins and lipids. PFASs were found in both the plasma and milk of all tested seal mothers and pups. While the concentrations were within the range of levels analyzed in other seal species, and lower than toxicity thresholds for rodents, the developmental effects are still not fully understood in wildlife. Developmental effects of PFASs are associated with reduced birth weight, and the hooded seal is dependent on an intense weight gain for the 3-4 days of nursing in order to survive a long fasting period that follows. This, coupled with the fact that young mammals are more susceptible to toxic effects than adults, could prove detrimental to this species.


News Article | December 10, 2016
Site: www.techtimes.com

Evolution has come to the rescue of some urban fish that live in lethal and human-altered environments. In a new study, researchers reported of a fish that has evolved to be 8,000 times more resilient to toxic waste compared with normal fish. The Atlantic killifish that lives in the heavily polluted East Coast estuaries such as the Elizabeth River in Virginia and the Newark Bay in New Jersey turned out to be very resilient to environmental change. The fish has evolved to adapt to the amount of highly toxic industrial pollutants that would normally kill them. The small striped fish is not commercially valuable but it is a favorite among aquarium owners because of its small size and beautiful colors. Ecologists also use it as an indicator species acting like an aquatic canary in polluted environments. Researchers attributed the resilience of the killifish to high levels of genetic variation that scientists have so far found to be higher than those of other vertebrates including humans. Evolution tends to act faster with more genetic diversity which explains why insects and weeds can easily evolve to resist the pesticides meant to eliminate them and why disease-causing bacteria and viruses can evolve fast to resist the drugs developed to destroy them. For the study published in the journal Science on Dec. 9, researchers sequenced the genomes of nearly 400 killifish from polluted and non-polluted sites. The polluted sites have been contaminated by a mixture of industrial plants which include heavy metals, dioxins, hydrocarbons and other chemicals since the 1950's and the 1960's. Genetic analysis revealed that the genetic diversity of the killifish makes it unusually well-positioned to adapt and survive in habitats that have been radically changed. The researchers conclude that the fish already has the genetic variation needed for them to adapt even before the habitats they live in became polluted. "High genetic diversity in killifish seems to allow selection to act on existing variation, driving rapid adaptation to selective forces such as pollution," the researchers wrote in their study. Study author Andrew Whitehead, from the University of California Davis Department of Environmental Toxicology, however, said that this does not mean species would just evolve to respond to human-caused changes to the environment. "Unfortunately, most species we care about preserving probably can't adapt to these rapid changes because they don't have the high levels of genetic variation that allow them to evolve quickly," Whitehead said. © 2017 Tech Times, All rights reserved. Do not reproduce without permission.


News Article | November 11, 2016
Site: www.eurekalert.org

Washington, DC - November 11, 2016 - Pesticide exposure in farmworkers from agricultural communities is associated with changes in the oral microbiome. This is the first study to demonstrate such a correlation in humans. The research is published November 11th in Applied and Environmental Microbiology, a journal of the American Society for Microbiology. In the study, the investigators sampled oral swabs from 65 farmworkers and 52 non-farmworker adults from the Yakima Valley (Washington) community agricultural cohort during the spring and summer (2005), when farmworkers can undergo high pesticide exposures while working in recently sprayed orchards, thinning the fruit and pruning; and during winter (2006), when exposures are quite low. Concurrently, they measured blood levels of organophosphate pesticides in the study subjects. The most important finding was that among those farmworkers in whom the organophosphate pesticide, Azinphos-methyl was detected in the blood, the researchers found "significantly reduced abundances of seven common taxa of oral bacteria, including Streptococcus, one of the most common normal microbiota in the mouth," said first author, Ian B. Stanaway, a PhD candidate in Environmental Toxicology in Elaine M. Faustman's lab at the University of Washington, Seattle. Changes in populations, species, and strains of Streptococcus, as well as from the genus, Halomonas, remained particularly low during the following winter. The investigators also saw a pesticide-associated spring/summer general reduction in bacterial diversity in the study subjects, which persisted into the winter,suggesting that "long-lasting effects on the commensal microbiota have occurred," according to the report. Predictably, farmworkers had greater blood concentrations of pesticide, and greater changes in their oral microbiota than local, non-farmworking adults. "The challenge becomes, what does this mean," said principal investigator Faustman, PhD, Professor in the department of Environmental and Occupational Health Sciences. "We don't know," she said, adding that "we depend on the micriobiome for many metabolic processes." Nonetheless, "in other studies, changes in species and strains of Streptococcus have been associated with changes in oral health," noted Stanaway. The study subjects' enthusiasm for the research has been important to its success, said coauthor Beti Thompson, PhD, Professor, School of Public Health, University of Washington. The investigators have followed the study participants for more than ten years, she said. "They are very interested in all the effects of pesticides. They have contributed thousands of urine samples, tens of cheek cell samples, blood samples, saliva samples, and house and vehicle dust." The American Society for Microbiology is the largest single life science society, composed of over 48,000 scientists and health professionals. ASM's mission is to promote and advance the microbial sciences. ASM advances the microbial sciences through conferences, publications, certifications and educational opportunities. It enhances laboratory capacity around the globe through training and resources. It provides a network for scientists in academia, industry and clinical settings. Additionally, ASM promotes a deeper understanding of the microbial sciences to diverse audiences.

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