Comparison of intermittent and continuous exposures to inorganic mercury in the mussel, Mytilus edulis: accumulation and sub-lethal physiological effects.

Aquatic organisms are often subject to intermittent exposure to pollutants in real ecosystems. This study aimed to compare mercury accumulation and the physiological responses of mussels, Mytilus edulis during continuous and intermittent exposure to the metal. Mussels were treated in a semi-static, triplicated design to either a control (no added Hg) or 50 µg l(-1) Hg as HgCl2 in continuous (daily) or intermittent (2 day exposure, 2 days in clean seawater alternately) exposure for 14 days. A time-dependent increase in Hg accumulation was observed in the continuous exposure, while the intermittent treatment showed step-wise changes in Hg concentrations with the exposure profile, especially in the gills. At the end of the experiment, tissue Hg concentrations were significantly increased in the continuous compared to the intermittent exposure for digestive gland (4 fold), gonad and remaining soft tissue (>2 fold), but not for the gill and adductor muscle. There was no observed oxidative damage at the end of the experiment as measured by the thiobarbituric acid reactive substances (TBARS) concentrations in tissues from all treatments. However, total glutathione was significantly decreased in the gill and digestive gland of both the continuous and intermittent exposure by the end of the experiment. The neutral red retention ability of the haemocytes was not affected, but total haemocyte counts were significantly decreased (<2 fold) in the intermittent compared to the continuous exposure. Histopathological examinations showed less pathology in the gill, but more inflammation in the digestive gland of mussels for the intermittent compared to the continuous exposure. Overall, the results showed that Hg accumulation from intermittent exposure was less than that of the continuous exposure regime, but the sub-lethal responses are sometimes more severe than expected in the former

Multiple metals exposure and neurotoxic risk in bald eagles ( Haliaeetus leucocephalus ) from two Great Lakes states

In the present study, the authors determined concentrations of several elements (As, Cd, Co, Cu, Cr, Mn, Pb, Sb, Zn) in the brains and livers of 46 bald eagles ( Haliaeetus leucocephalus ) from two Great Lakes states, Michigan and Minnesota. To explore whether exposures are of neurological concern, the authors assessed their associations with neurochemical receptors ( N ‐methyl‐ D ‐aspartate [NMDA] and γ‐aminobutyric acid A [GABA(A)]) and enzymes (glutamine synthetase [GS] and glutamic acid decarboxylase [GAD]) that play critical roles in vertebrate neurobehavior and reproduction. For most elements, levels in the livers and brains did not differ between region and gender. Hepatic Pb levels averaged 33.1 ppm (dry wt), 30.4% of all carcasses exceeded proposed avian Pb thresholds (>26.4 ppm), and in 30.8% of the birds examined evidence of Pb pellets or fragments was found. Significant changes in the activities of GS and GAD were related to brain concentrations of several metals (Pb, Cd, Co, Cu, Zn). No relationships were found among any of the nine elements and NMDA or GABA(A) receptor levels. When combined with the authors' previous study on these same eagles that showed Hg‐associated alterations in GS, GAD, and NMDA receptor levels, the present research suggests that bald eagles are exposed to various elements, especially Pb and Hg, that are capable of causing changes in GABAergic and glutamatergic neurotransmission. The functional significance of these neurochemical changes warrants attention. Environ. Toxicol. Chem. 2012;31:623–631. © 2011 SETACPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90053/1/1712_ftp.pd

History of Wildlife Toxicology and the Interpretation of Contaminant Concentrations in Tissues

The detection and interpretation of contaminants in tissues of wildlife belongs to the field of toxicology, a scientific discipline with a long, intriguing, and illustrious history (reviewed by Hayes 1991, Gallo 2001, Gilbert and Hayes 2006, Wax 2006). We review its history briefly, to provide a context for understanding the use of tissue residues in toxicology, and to explain how their use has developed over time. Because so much work has been conducted on mercury, and dioxins and polychlorinated biphenyls (PCBs), separate case histories are included that describe the evolution of the use of tissue concentrations to assess exposure and effects of these two groups of contaminants in wildlife. The roots of toxicology date back to early man, who used plant and animal extracts as poisons for hunting and warfare. The Ebers papyrus (Egypt -1550 BC) contains formulations for hemlock, aconite (arrow poison), opium, and various metals used as poisons. Hippocrates (-400 BC) is sometimes credited with proposing the treatment of poisoning by decreasing absorption and using antidotes (Lane and Borzelleca 2007). Chanakya (350-283 BC), Indian advisor of the Maurya Emperor Chandragupta (340-293 BC), urged the use of food tasters as a precaution against poisoning, and the Roman emperor Claudius may have even been poisoned by his taster Halotus in 54 AD. Moses ben Maimon (1135-1204), author of a treatise on poisoning, noted that dairy products could delay absorption of some poisons. Paracelsus (1493-1541) shaped the field of toxicology with his corollaries that experimentation is essential to examining the response, that therapeutic properties should be distinguished from toxic properties, that chemicals have specific modes of action, and that the dose makes the poison. The art of concocting and using poisons reached its zenith during the Italian Renaissance, eventually culminating in its commercialization by Catherine Deshayes (a.k.a., La Voisine, 1640-1680) in France. One of the first to suggest a chemical method for the detection of a poison in modern times was Herman Boerhaave (1668-1738), a physician and botanist, who, according to Jurgen Thorwald (The Century of the Detective), placed the suspected poison on red-hot coals, and tested for odors. The Spanish physician Orfila (1787-1853) served in the French court, and was the first toxicologist to systematically use autopsy and chemical analysis to prove poisoning. He has been credited with developing and refining techniques to detect arsenic poisoning. Other historic accounts include extraction of alkaloids from postmortem specimens (Jean Servais Stas ~1851) as evidence in a nicotine poisoning case (Levine 2003). The chemical analysis of organs and tissues became the basis for establishing poisoning. Much of the early history of toxicology addressed whether someone had been poisoned and how to treat poisoning

Contour completion at edge endings

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 1988.Vita.Includes bibliographical references.by Joseph Edward Scheuhammer.Ph.D

Framework for Accessible and Equitable Artificial Intelligence (AI) in Education

Funded by the Government of Ontario.I. General AI RisksII. AI in Education: The Hype, the Confusion, and the StoryIII. Conditions for Accessible and Equitable AIIV. Advanced Topics That Need InterrogationV. The Regulatory Domain in Ontario and in CanadaThis is a practical guide to the dizzying domain of artificial intelligence within the education ecosystem, with a particular focus on the impact on equity and accessibility. AI and accessibility are beginning to have an interesting conversation. Not unlike the conversation about AI in general, the conversation about AI and accessibility in education can be found taking a techno-solutionist or techno-tragedist perspective. As we grow wary of this false dichotomy, we move toward what is much more likely to be the case: that it will be “both/and” and “neither/nor.” AI can make things better. It can benefit us all, it can address inequities, and it can lower barriers for people with disabilities in education. It can equally be used to amplify inequities (intentional and unintended), including discrimination against people who do not fit a “norm.” AI is neither uniformly bad nor uniformly good for furthering our goals of eliminating barriers to education for people

Ecogenetics of mercury: From genetic polymorphisms and epigenetics to risk assessment and decision‐making

The risk assessment of mercury (Hg), in both humans and wildlife, is made challenging by great variability in exposure and health effects. Although disease risk arises following complex interactions between genetic (“nature”) and environmental (“nurture”) factors, most Hg studies thus far have focused solely on environmental factors. In recent years, ecogenetic‐based studies have emerged and have started to document genetic and epigenetic factors that may indeed influence the toxicokinetics or toxicodynamics of Hg. The present study reviews these studies and discusses their utility in terms of Hg risk assessment, management, and policy and offers perspectives on fruitful areas for future research. In brief, epidemiological studies on populations exposed to inorganic Hg (e.g., dentists and miners) or methylmercury (e.g., fish consumers) are showing that polymorphisms in a number of environmentally responsive genes can explain variations in Hg biomarker values and health outcomes. Studies on mammals (wildlife, humans, rodents) are showing Hg exposures to be related to epigenetic marks such as DNA methylation. Such findings are beginning to increase understanding of the mechanisms of action of Hg, and in doing so they may help identify candidate biomarkers and pinpoint susceptible groups or life stages. Furthermore, they may help refine uncertainty factors and thus lead to more accurate risk assessments and improved decision‐making. Environ Toxicol Chem 2014;33:1248–1258. © 2013 SETACPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106903/1/etc2375.pd

Methylmercury degradation and exposure pathways in streams and wetlands impacted by historical mining

The authors acknowledge financial support from the National Science Foundation: EAR-1226741 (to M.B.S.) and EAR-1225630 (to J.D.B.).Monomethyl mercury (MMHg) and total mercury (THg) concentrations and Hg stable isotope ratios (δ202Hg and Δ199Hg) were measured in sediment and aquatic organisms from Cache Creek (California Coast Range) and Yolo Bypass (Sacramento Valley). Cache Creek sediment had a large range in THg (87 to 3870 ng/g) and δ202Hg (− 1.69 to − 0.20‰) reflecting the heterogeneity of Hg mining sources in sediment. The δ202Hg of Yolo Bypass wetland sediment suggests a mixture of high and low THg sediment sources. Relationships between %MMHg (the percent ratio of MMHg to THg) and Hg isotope values (δ202Hg and Δ199Hg) in fish and macroinvertebrates were used to identify and estimate the isotopic composition of MMHg. Deviation from linear relationships was found between %MMHg and Hg isotope values, which is indicative of the bioaccumulation of isotopically distinct pools of MMHg. The isotopic composition of pre-photodegraded MMHg (i.e., subtracting fractionation from photochemical reactions) was estimated and contrasting relationships were observed between the estimated δ202Hg of pre-photodegraded MMHg and sediment IHg. Cache Creek had mass dependent fractionation (MDF; δ202Hg) of at least − 0.4‰ whereas Yolo Bypass had MDF of + 0.2 to + 0.5‰. This result supports the hypothesis that Hg isotope fractionation between IHg and MMHg observed in rivers (− MDF) is unique compared to + MDF observed in non-flowing water environments such as wetlands, lakes, and the coastal ocean.PostprintPeer reviewe

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 0.1, 0.18, and 0.4 µg g −1 wet weight MeHg in prey fish. The lowest benchmark (0.1 µg g −1 wet wt) is the threshold for adverse behavioral impacts in adult loons and is close to the empirically determined no observed adverse effects level for subclinical effects observed in captive loon chicks. The remaining benchmarks (0.18 and 0.4 µg g −1 wet wt) correspond to MeHg levels in prey fish associated with significant reproductive impairment and reproductive failure in wild adult loons. Overall, these benchmarks incorporate recent findings and reviews of MeHg toxicity in aquatic fish‐eating birds and provide the basis for a national ecological risk assessment for Hg and loons in Canada. Environ. Toxicol. Chem. 2012; 31: 2399–2407. © 2012 SETACPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/93756/1/1971_ftp.pd

Cadre pour une intelligence artificielle (IA) accessible et équitable en éducation

Funded by the Government of Ontario.I. Risques généraux liés à l’IAII. L’IA dans l’éducation : l’engouement, la confusion et l’histoireIII. Conditions pour une IA accessible et équitableIV. Sujets avancés nécessitant un interrogatoireV. Le domaine réglementaire en Ontario et au CanadaIl s’agit d’un guide pratique sur le domaine vertigineux de l’intelligence artificielle au sein de l’écosystème éducatif, avec un accent particulier sur l’impact sur l’équité et l’accessibilité. L’IA et l’accessibilité commencent à avoir une conversation intéressante. À l’instar du débat sur l’IA en général, le débat sur l’IA et l’accessibilité dans l’éducation peut s’inscrire dans une perspective techno-solutionnisme ou techno-tragédienne. À mesure que nous devenons plus méfiants à l’égard de cette fausse dichotomie, nous nous dirigeons vers ce qui est beaucoup plus probable, à savoir que la situation sera « à la fois/et » et « non/ni ». L’IA peut améliorer les choses. Elle peut nous être bénéfique à tous, elle peut remédier aux inégalités et elle peut réduire les obstacles pour les personnes handicapées dans le domaine de l’éducation. Elle peut également être utilisée pour amplifier les inégalités (intentionnelles et involontaires), y compris la discrimination contre les personnes qui ne correspondent pas à une « norme ». L’IA n’est ni uniformément mauvaise ni uniformément bonne pour la réalisation de nos objectifs d’élimination des obstacles à l’éducation pour les personnes. Il y a cependant quelques domaines clés dans lesquels nous devons être vigilants pour nous assurer que les outils d’IA sont utilisés pour faire tomber les barrières, pas pour les créer Nous vous implorons, vous, la communauté élargie des professionnels de l’enseignement supérieur en Ontario, de vous intéresser aux informations contenues dans cette ressource et de participer à la conversation sur les utilisations accessibles et équitables de l’IA dans l’éducation