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See detailMercury immune toxicity in harbour seals: Links to in vitro toxicity
Das, Krishna ULg; Siebert, Ursula; Gillet, Audrey et al

in Environmental Health : A Global Access Science Source (2008), 7

Background Mercury is known to bioaccumulate and to magnify in marine mammals, which is a cause of great concern in terms of their general health. In particular, the immune system is known to be ... [more ▼]

Background Mercury is known to bioaccumulate and to magnify in marine mammals, which is a cause of great concern in terms of their general health. In particular, the immune system is known to be susceptible to long-term mercury exposure. The aims of the present study were (1) to determine the mercury level in the blood of free-ranging harbour seals from the North Sea and (2) to examine the link between methylmercury in vitro exposure and immune functions using seal and human mitogen-stimulated peripheral blood mononuclear cells (T-lymphocytes). Methods Total mercury was analysed in the blood of 22 harbour seals. Peripheral blood mononuclear cells were isolated from seals (n = 11) and from humans (n = 9). Stimulated lymphocytes of both species were exposed to functional tests (proliferation, metabolic activity, radioactive precursor incorporation) under increasing doses of methylmercury (0.1 to 10 µM). The expression of cytokines (IL-2; IL-4 and TGF-beta was investigated in seal lymphocytes by RT-PCR and by real time quantitative PCR (n = 5) at methylmercury concentrations of 0.2 and 1 µM. Finally, proteomics analysis was attempted on human lymphocytes (cytoplasmic fraction) in order to identify biochemical pathways of toxicity at concentration of 1 µM (n = 3). Results The results showed that the number of seal lymphocytes, viability, metabolic activity, DNA and RNA synthesis were reduced in vitro, suggesting deleterious effects of methylmercury concentrations naturally encountered in free-ranging seals. Similar results were found for human lymphocytes. Functional tests showed that a 1 µM concentration was the critical concentration above which lymphocyte activity, proliferation and survival were compromised. The expression of IL-2 and TGF-beta mRNA was weaker in exposed seal lymphocytes compared to control cells (0.2 and 1 µM). Proteomics showed some variation in the protein expression profile (e.g. vimentin). [less ▲]

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See detailMercury, polychlorobiphenyls and stable isotopes in the blood of harbour seals (Phoca vitulina) from the southern North Sea
Das, Krishna ULg; Lepoint, Gilles ULg; Fonfara, Sonja et al

Poster (2005)

The harbor seal (Phoca vitulina) is one of the most widely distributed seal species and the North Sea contains around 10 % of the world population. The harbour seal population in the North Sea was ... [more ▼]

The harbor seal (Phoca vitulina) is one of the most widely distributed seal species and the North Sea contains around 10 % of the world population. The harbour seal population in the North Sea was estimated at 36 000 individuals between 1994 and 1996). However, recurrent Phocine Distemper Virus (PDV) epizooties have affected the North Sea seal population. Recently, 21 500 harbor seals were killed by PDV in the North Sea and adjacent waters in 2002. Some intriguing questions about the interaction between PDV and immunotoxic contaminants, such as mercury (Hg) and polychlorinated biphenyls (PCBs) remain unanswered. In this framework, circulating levels of Hg and PCBs (PCBs 28, 52, 101, 118, 138, 153, 180) were measured in the blood of 24 harbour seals captured on a sandbank between 2001 and 2004 (Schleswig-Holstein, Germany). As pollutant level may be linked to the trophic position in the food web, carbon and nitrogen isotopic ratios (δ13C and δ15N) were measured in clotted blood cells. The average concentration of mercury in these living seals did not differ significantly from those observed previously in stranded harbour seals (94 ± 41 vs 146 ± 71 µg.l-1 respectively). Mean blood concentrations of total PCBs (∑PCBs) were 11 ng/ml. CB 153 clearly dominated the mix (45%) followed by PCB 138 (31%). The average isotopic composition measured in the blood cells was –15.6 ± 0.3 0/00 and 18.7 ± 0.6 0/00 for δ13C and δ15N respectively, similar to that obtained previously in muscle of stranded individuals, confirming the high position of the harbour seal in the North Sea trophic chain. Further investigations are obviously needed on a larger sampling but our preliminary results suggest that blood is an interesting substrate for both trophic and pollutant long-term monitoring of the harbour seal in the North Sea. [less ▲]

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See detailInvestigations on the development of the health status of harbour seals in the year of the PDV seal die-off in 2002
Siebert, Ursula; Fonfara, Sonja; Hasselmeier, Ilka et al

Poster (2004, March 31)

More than 21,500 harbour seals were killed by Phocine Distempter Virus in the North Sea and adjacent waters in 2002. Of those more than 3,340 seals were found dead on the coast of Schleswig-Holstein ... [more ▼]

More than 21,500 harbour seals were killed by Phocine Distempter Virus in the North Sea and adjacent waters in 2002. Of those more than 3,340 seals were found dead on the coast of Schleswig-Holstein. After the second seal die-off had ceased, seals were captured alive for a health check and also stranded seals were examined for their health status. Blood status and chemistry tests were performed, microbiological, parasitological, histological, serological and cytological investigations were conducted. During the first catch after the seal die-off animals seemed to be in clinically good condition although hematological disturbances (leucocytosis as well as leucopenia) were detected. Bacteriologically, Bordetella bronchisptica was isolated, a bacterium which was exclusively cultured during the seal die-off. At later catches hematological values normalized and also the normal bacterial flora was cultured from vagina and anus. The serological investigations for morbillivirus-specific antibodies revealed positive titers in 100% of the seals. Morphologically, there was no evidence for a continuing morbillivirus infection by both, histology and immunocytochemistry. The pathomorphological changes were similar to those before the epizootic including the predominance of parasitic and bacterial bronchopneumonia, emaciation and dermatitis. Contrary to the first seal die-off in 1988/89 an increased number of large skin wounds on the ventral side and infections of the umbilicus were not seen. This may indicate that the seal population in Schleswig-Holstein was generally in better health condition at the second seal die-off compared to the first one. The continued investigations will allow a further assessment of the development of the seal population in the Wadden Sea. [less ▲]

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See detailCytokine messenger RNA expression in the blood of harbour porpoises (phocoena phocoena).
Das, Krishna ULg; Fonfara, Sonja; Beineke, Andreas et al

Poster (2004)

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