Effects of methylmercury on epigenetic markers in three model species: mink, chicken and yellow perch.

We previously reported that methylmercury (MeHg) exposure is associated with DNA hypomethylation in the brain stem of male polar bears. Here, we conveniently use archived tissues obtained from controlled laboratory exposure studies to look for evidence that MeHg can disrupt DNA methylation across taxa. Brain (cerebrum) tissues from MeHg-exposed mink (Neovison vison), chicken (Gallus gallus) and yellow perch (Perca flavescens) were analyzed for total Hg levels and global DNA methylation.

Derivation of screening benchmarks for dietary methylmercury exposure for the common loon (Gavia immer): rationale for use in ecological risk assessment.

The current understanding of methylmercury (MeHg) toxicity to avian species has improved considerably in recent years and indicates that exposure to environmentally relevant concentrations of MeHg through the diet can adversely affect various aspects of avian health, reproduction, and survival. Because fish-eating birds are at particular risk for elevated MeHg exposure, the authors surveyed the available primary and secondary literature to summarize the effects of dietary MeHg on the common loon (Gavia immer) and to derive ecologically relevant toxic thresholds for dietary exposure to MeHg in fish prey. After considering the available data, the authors propose three screening benchmarks of 0.

Toxicity of methylmercury injected into eggs of thick-billed murres and arctic terns.

Mercury (Hg) has been increasing in some marine birds in the Canadian Arctic over the past several decades. To evaluate the potential reproductive impact of Hg exposure, eggs of two species of arctic-breeding seabirds, the thick-billed murre and arctic tern, were dosed with graded concentrations of methylmercury (MeHg) and artificially incubated in the laboratory to determine species differences in sensitivity. Based on the dose-response curves, the median lethal concentrations (LC(50)) for thick-billed murre and arctic tern embryos were 0.

Selenium accumulation and reproduction in birds breeding downstream of a uranium mill in northern Saskatchewan, Canada.

Selenium (Se) concentrations in aquatic invertebrates and bird eggs collected along the treated effluent receiving environment of the Key Lake uranium mill in northern Saskatchewan were significantly greater than from nearby reference areas, and in some cases (e.g., eggs of common loons--Gavia immer) were higher than commonly used thresholds for adverse reproductive effects in birds (i.

Spatial gradients of methylmercury for breeding common loons in the Laurentian Great Lakes region.

Much of the Laurentian Great Lakes region is a mercury-sensitive landscape, in which atmospheric deposition and waterborne sources of mercury (Hg) have led to high concentrations of bioavailable methylmercury (MeHg) in predatory fish and piscivorous wildlife. Efforts since the early 1990s have established the common loon (Gavia immer) as the primary avian indicator for evaluating the exposure and effects of MeHg in North America. A regional Hg dataset was compiled from multiple loon tissue types and yellow perch (Perca flavescens), a preferred prey fish species for loons.

Evidence for sex differences in mercury dynamics in double-crested cormorants.

Aquatic fish-eating birds can demethylate methylmercury in their livers. In this study, we determined whether a previously documented male bias in mercury concentration in double-crested cormorants ( Phalacrocorax auritus ) was due entirely to the depuration of mercury into eggs or might also in part be related to sex differences in methylmercury demethylation or biliary excretion capability in the liver. We found egg depuration accounted for less than a fifth of the mercury concentration difference between males and females, hence not entirely explaining the sex difference.

Predicting mercury concentrations and fluxes in the water column and sediment of lakes with a limited dataset.

The purpose of the present study was to evaluate the mercury (Hg) Environmental Ratios Multimedia Ecosystem Sources (HERMES) model on two Ontario, Canada lakes (Harp and Dickie) and to include modifications to enable the model to estimate the major model input variables that tend to be missing for lakes with limited datasets. No significant differences were found for either sediment solid or bulk water total mercury (THg) when the HERMES model was applied to the two Ontario lakes, regardless of whether all available data were altered during application or only the 10 variables that tend to cause the most variation in model output (i.e.

In vitro and whole animal evidence that methylmercury disrupts GABAergic systems in discrete brain regions in captive mink.

The effects of mercury (Hg) on key components of the GABAergic system were evaluated in discrete brain regions of captive juvenile male American mink (Neovison vison) using in vitro and in vivo (whole animal) experimental approaches. In vitro studies on cortical brain tissues revealed that inorganic Hg (HgCl(2); IC50=0.5+/-0.

Neurochemical and electrophysiological diagnosis of reversible neurotoxicity in earthworms exposed to sublethal concentrations of CL-20.

Background, Aim, And Scope: Hexanitrohexaazaisowurtzitane (CL-20) is a relatively new energetic compound sharing some degree of structural similarity with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), a known neurotoxic compound. Previously, we demonstrated using a noninvasive electrophysiological technique that CL-20 was a more potent neurotoxicant than RDX to the earthworm Eisenia fetida. In the present study, we investigated the effect of CL-20 exposure and subsequent recovery on muscarinic acetylcholine receptors (mAChRs) to further define the mechanism of reversible neurotoxicity of CL-20 in E.

Bone lead levels and lead isotope ratios in red grouse from Scottish and Yorkshire moors.

Leg and foot bones of adult and juvenile red grouse (Lagopus lagopus scoticus) were collected from hunter-shot birds on two Scottish estates (Glendye and Invermark) and one Yorkshire estate in September, 2003. The lead content of bones was measured by atomic absorption spectrophotometry, and corresponding stable lead isotopes (Pb(204, 206, 207, 208)) by inductively coupled plasma mass spectrometry. At the Glendye (N=111) and Invermark (N=85) estates, relatively few birds (5.

Is dietary mercury of neurotoxicological concern to wild polar bears (Ursus maritimus)?

Polar bears (Ursus maritimus) are exposed to high concentrations of mercury because they are apex predators in the Arctic ecosystem. Although mercury is a potent neurotoxic heavy metal, it is not known whether current exposures are of neurotoxicological concern to polar bears. We tested the hypotheses that polar bears accumulate levels of mercury in their brains that exceed the estimated lowest observable adverse effect level (20 microg/g dry wt) for mammalian wildlife and that such exposures are associated with subtle neurological damage, as determined by measuring neurochemical biomarkers previously shown to be disrupted by mercury in other high-trophic wildlife.

The effects of mercury on muscarinic cholinergic receptor subtypes (M1 and M2) in captive mink.

A combination of in vitro (competitive binding assays) and in vivo (tissues from animals exposed to dietary methyl mercury, MeHg) experimental procedures was employed to assess the effects of mercury (MeHg, HgCl(2)) on the two-key muscarinic cholinergic (mACh) receptor subtypes (M1, M2) in two brain regions (occipital cortex, brain stem) of captive mink (Mustela vison). In vitro, HgCl(2) and MeHg were equipotent in inhibiting [(3)H]-pirenzipine binding to the M1 receptor in the occipital cortex, but in the brain stem, MeHg was about 65x more potent than HgCl(2). For the M2 receptor, both HgCl(2) and MeHg were more potent at inhibiting [(3)H]-AFDX-384 binding in the occipital cortex than in the brain stem.

Trace element and metallothionein concentrations in seabirds from the Canadian Arctic.

Livers and kidneys were collected for five seabird species from the Canadian Arctic during the 1983 and 1991 to 1993 breeding seasons. Livers were analyzed for Cd, Hg, Pb, and Se, and kidneys were analyzed for Cd, Cu, Zn, and metallothionein (MT). Concentrations of the essential elements, Cu and Zn, were in agreement with those previously published in the literature.

Effects of environmental methylmercury on the health of wild birds, mammals, and fish.

Wild piscivorous fish, mammals, and birds may be at risk for elevated dietary methylmercury intake and toxicity. In controlled feeding studies, the consumption of diets that contained Hg (as methylmercury) at environmentally realistic concentrations resulted in a range of toxic effects in fish, birds, and mammals, including behavioral, neurochemical, hormonal, and reproductive changes. Limited field-based studies, especially with certain wild piscivorous bird species, e.

Polychlorinated biphenyls, organochlorinated pesticides, and polybrominated diphenyl ethers in the cerebral cortex of wild river otters (Lontra canadensis).

We measured the levels of ortho-substituted polychlorinated biphenyls (PCB), organochlorinated pesticides (OCP), and polybrominated diphenyl ethers (PBDE) in the cerebral cortex of river otters (Lontra canadensis) trapped from Ontario and Nova Scotia between 2002 and 2004. The mean concentration of total PCBs was 70.9+/-12.

Decreased N-methyl-D-aspartic acid (NMDA) receptor levels are associated with mercury exposure in wild and captive mink.

Mercury (Hg) impairs glutamate homeostasis but little is known about its effects on the N-methyl-d-aspartic acid (NMDA) receptor. Here, we investigated NMDA receptor levels, as determined by [(3)H]-MK801 binding, in both wild and captive mink (Mustela vison) that experienced different levels of methylmercury (MeHg) exposure. Competitive in vitro binding experiments showed that inorganic Hg (HgCl(2); IC(50)=1.

Mink as a sentinel species in environmental health.

The concept of "sentinel species" is important in the environmental health sciences because sentinel species can provide integrated and relevant information on the types, amounts, availability, and effects of environmental contaminants. Here we discuss the use of mink (Mustela vison) as a sentinel organism by reviewing the pertinent literature from exposure- and effects-based studies. The review focuses on mercury (Hg) and polychlorinated biphenyls (PCBs), as they are persistent, ubiquitous, and bioaccumulative contaminants of concern to both humans and wildlife.

Mercury exposure and reproduction in fish-eating birds breeding in the Pinchi Lake region, British Columbia, Canada.

To determine whether Hg from geologic/mining-related sources at Pinchi Lake (BC, Canada) was causing elevated Hg exposure and/or adversely affecting reproduction in fish-eating birds, breeding bald eagles (Haliaeetus leucocephalus) on Pinchi Lake and four nearby reference lakes were sampled for blood and feather Hg concentrations and monitored for reproductive success during the summers of 2000, 2001, and 2002. Eggs of red-necked grebes (Podiceps grisgena) also were collected and analyzed. Mercury levels in species at various trophic levels from Pinchi Lake averaged approximately twice those in the same species from nearby lakes combined, even in the absence of substantial new inputs of Hg to Pinchi Lake over several decades.

Methylmercury impairs components of the cholinergic system in captive mink (Mustela vison).

The effects of methylmercury (MeHg) on components of the cholinergic system were evaluated in captive mink (Mustela vison). Cholinergic parameters were measured in brain regions (occipital cortex, cerebellum, brain stem, basal ganglia) and blood (whole blood, plasma, serum) following an 89-day exposure to MeHg at dietary concentrations of 0, 0.1, 0.

Effects of mercury on neurochemical receptor-binding characteristics in wild mink.

Piscivorous wildlife, such as mink (Mustela vison), routinely are exposed to mercury (Hg) in their natural environment at levels that may cause adverse behavioral outcomes. The purpose of this study was to determine if a correlation exists between neurochemical receptors and concentrations of Hg in the brains of wild mink. Specifically, receptor-binding assays were conducted to characterize the muscarinic cholinergic (mACh) and dopaminergic-2 (D2) systems in brain tissues collected from mink trapped in the Yukon Territory, Ontario, and Nova Scotia (Canada), and values were correlated with total Hg and methyl Hg (MeHg) concentrations in the brains.

Mercury in freshwater fish of northeast North America--a geographic perspective based on fish tissue monitoring databases.

As part of an initiative to assemble and synthesize mercury (Hg) data from environmental matrices across northeastern North America, we analyzed a large dataset comprised of 15,305 records of fish tissue Hg data from 24 studies from New York State to Newfoundland. These data were summarized to provide mean Hg concentrations for 40 fish species and associated families. Detailed analyses were carried out using data for 13 species.

Lead and stable lead isotope ratios in soil, earthworms, and bones of American woodcock (Scolopax minor) from eastern Canada.

A study to discriminate among different possible sources of elevated Pb exposure for American woodcock (Scolopax minor) in eastern Canada is described. Undamaged wing bones excised from young-of-the-year woodcock collected from several locations in southern Ontario, southern Quebec, New Brunswick, and Nova Scotia, Canada, along with soil and earthworm (Aporrectodea tuberculata and Lumbricus rubellus) samples from the same sites, were analyzed for total Pb, and stable Pb isotopes. Ignoring six soil samples with high (> 60 microg/g) Pb concentration from the vicinity of Montreal (QC, Canada), the mean soil-Pb concentration for all sites combined was 19 microg/g (dry wt; n = 64), with a mean 206Pb:207Pb ratio of 1.

Effects of cadmium ingestion on plasma and osmoregulatory hormone concentrations in male and female Pekin ducks.

Effects of ingested cadmium (Cd) on body mass and plasma, urine, salt-gland secretion, and osmoregulatory hormone concentrations were assessed in male and female Pekin ducks, Anas platyrhynchos, acclimated to 450 mM NaCl over 6 wk and then held an additional 13 wk on 300 mM NaCl (prolonged saline exposure). Groups of six birds ate diets containing 0 (control), 50 (low-Cd diet), or 300 (high Cd diet) micrograms Cd/g food. Ducks that ingested Cd, especially females, lost body mass.