Mammals mercury

The mink Mustela vision) is a piscivorous mammal that also has been exposed to relatively high dietary levels of methyl mercury in North America in recent times. In a Canadian study, mink trapped in Yukon territory, Ontario, and Nova Scotia were analyzed for levels of mercury and abundance of muscarinic, cholinergic and dopaminergic receptors in the brain (Basu et al. 2005). A correlation was found between total Hg levels and abundance of muscarinic receptors, but a negative correlation was found between total Hg and abundance of dopaminergic receptors. Thus, it was suggested that environmentally relevant concentrations of Hg (much of it in methyl form) may alter neurochemical function. The highest levels of mercury contamination were found in mink from Nova Scotia that had a mean concentration of total Hg of 5.7 pg/g in brain, 90% of which was methyl mercury. 

Brain is a key tissue to analyze for mercury concentration because it is the site of MeHg toxicity. The neurotoxic effects of MeHg in adrrlt mammals inclnde ataxia, difficulty in locomotion neurasthenia, a generalized weakness impairment of hearing... 

Thompson DR. 1996. Mercury in birds and terrestrial mammals. In Beyer WN, Heinz GH, Redmon-Norwood AW, editors. Environmental contaminants in wildlife interpreting tissue concentrations. Boca Raton (FL) Lewis Publishers. 

Wren CD. 1986. A review of metal accumulation and toxicity in wild mammals. 1. Mercury. Environ Res 40 1737-1744. 

In mammals, as in yeast, several different metallothionein isoforms are known, each with a particular tissue distribution (Vasak and Hasler, 2000). Their synthesis is regulated at the level of transcription not only by copper (as well as the other divalent metal ions cadmium, mercury and zinc) but also by hormones, notably steroid hormones, that affect cellular differentiation. Intracellular copper accumulates in metallothionein in copper overload diseases, such as Wilson s disease, forming two distinct molecular forms one with 12 Cu(I) equivalents bound, in which all 20 thiolate ligands of the protein participate in metal binding the other with eight Cu(I)/ metallothionein a molecules, with between 12-14 cysteines involved in Cu(I) coordination (Pountney et ah, 1994). Although the role of specific metallothionein isoforms in zinc homeostasis and apoptosis is established, its primary function in copper metabolism remains enigmatic (Vasak and Hasler, 2000). 

Mercury concentrations in livers of four species of pinniped mammals... 

Figure 5.2 Mercury concentrations in livers of tour species of pinniped mammals. (From Eisler, R. 1984. Trace metal changes associated with age of marine vertebrates. Biol. Trace Elem. Res. 6 165-180. With permission.)... 

Mercury is a known mutagen, teratogen, and carcinogen. At comparatively low concentrations in birds and mammals, it adversely affects reproduction, growth and development, behavior, blood... 

Proposed mercury criteria for the protection of sensitive aquatic organisms, birds, and mammals, as well as human health, are shown in Table 5.11. In almost every instance, these criteria are listed as concentrations of total mercury, with most, if not all, the mercury present as an organomercury species. In some cases the recommended criteria are routinely exceeded, as is the case for brown bears (Ursus arctos) in the Slovak Republic (Zilincar et al. 1992), and in Italian seafood products recommended for human consumption (Barghigiani and De Ranieri 1992). 

Cannella, E.G. and D.J. Kitchener. 1992. Differences in mercury levels in female sperm whale, Physeter macrocephalus (Cetacea Odontoceti). Austral. Mammal. 15 121-123. 

Das, S.K., A. Sharma, and G. Talukder. 1982. Effects of mercury on cellular systems in mammals — a review. Nucleus (Calcutta) 25 193-230. 

Dietz, R., C.O. Nielsen, M.M. Hansen, and C.T. Hansen. 1990. Organic mercury in Greenland birds and mammals. Sci. Total Environ. 95 41-51. 

Schintu, M., F. Jean-Caurant, and J.C. Amiard. 1992. Qrganomercury determination in biological reference materials application to a study on mercury speciation in marine mammals off the Faroe Islands. Ecotoxicol. Environ. Safety 24 95-101. 

Talmage, S.S. and B.T. Walton. 1993. Food chain transfer and potential renal toxicity of mercury to small mammals at a contaminated terrestrial field site. Ecotoxicology 2 243-256. 

Wagemann, R., R.E.A. Stewart, W.L. Lockhart, and B.E. Stewart. 1988. Trace metals and methyl mercury associations and transfer in harp seal (Phoca groenlandica) mothers and their pups. Mar. Mammal Sci. 4 339-355. 

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