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Please use this identifier to cite or link to this item: http://hdl.handle.net/10451/1577

Título: Small mammals as bioindicators in the assessment of toxicological effects resulting from the exposure to heavy metals
Autor: Marques, Carla Cristina Antunes, 1971-
Orientador: Mathias, Maria da Luz, 1952-
Crespo, Ana Maria Viegas, 1946-
Palavras-chave: Ecofisiologia
Teses de doutoramento - 2009
Issue Date: 2009
Resumo: Abandoned metal mines are among the most severe environmental problems in Portugal, particularly taking into account the fact that in many cases the closing of mines are not followed by environmental requalification plans. As a consequence tones of metal residues are still circulating in their surroundings, with unpredictable effects to living organisms. However, in selected animal models, in spite of the potential environmental risk that these polluted areas may represent, few studies have investigated the environmental health impacts of long-term exposure to mining residues. The main objective of the present PhD project was the evaluation of the environmental impact of metal abandoned mines located in southern Portugal (the Preguiça mine deactivated since 1964, and the Aljustrel mine deactivated since 1996), using two small mammals species, the white-toothed shrew (Crocidura russula) and the Algerian mouse (Mus spretus), as sentinels. The main results can be summarized, as follows: 1) environmental levels of manganese, iron, copper, zinc, lead and arsenic are still circulating in the surroundings of both mines; 2) high hepatic contents of cadmium and nickel were detected in C. russula collected in the Preguiça area, while in shrews from Aljustrel besides cadmium and nickel also an increased accumulation of iron, lead, mercury and molybdenum in liver and/or kidney was found; 3) shrews from Preguiça revealed no significant alterations on haematological parameters and antioxidant enzyme activities, while Aljustrel shrews presented a hepatic decrease in glutathione S-transferase (GST) activity, an increase in relative liver mass and in hepatic histological alterations, and also an increase in micronucleus frequency in peripheral blood; 4) findings in M. spretus showed an increased of selenium in Preguiça individuals and increased hepatic iron and selenium in Aljustrel area; 5) in Algerian mice, hepatic glutathione peroxidase (GPx) activity increase, especially in dry season, and also hepatic histological alterations in both mining areas were detected; 6) high induction of hepatic metallothioneins was found in winter in Algerian mice from Aljustrel mine; 7) season seemed to be an important factor regulating the several biomarkers variation, whereas sex and age were less relevant factors; 8) in experimental conditions using the M. spretus as a model, the toxicity of lead seemed to be dependent of the duration of exposure and originate alterations in body and spleen mass, and in haematological and cytogenetical parameters; 9) also in controlled conditions, contamination by cadmium, lead and zinc induced micronucleus, sister chromatid exchange and sperm abnormalities in Algerian mice and the mutagenic potential of these elements could be dependent of the time of exposure and of the interaction between elements. These results confirm the potential environmental impact of abandoned mines, and strongly support the need of requalification plans in old mines. This study also confirms the relevance of small mammals as bioindicators of environmental pollution and the usefulness of biomarkers in identifying toxicological effects in living organisms.
Descrição: Tese de doutoramento em Biologia (Ecofisiologia), apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2009
URI: http://sibul.reitoria.ul.pt/F/?func=item-global&doc_library=ULB01&type=03&doc_number=000545910
Appears in Collections:FC - Teses de Doutoramento

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