Cytogenetic damage related to low levels of methyl mercury contamination in the Brazilian Amazon

The mercury rejected in the water system, from mining operations and lixiviation of soils after deforestation, is considered to be the main contributors to the contamination of the ecosystem in the Amazon Basin. The objectives of the present study were to examine cytogenetic functions in peripheral lymphocytes within a population living on the banks of the Tapajós River with respect to methylmercury (MeHg) contamination, using hair mercury as a biological indicator of exposure. Our investigation shows a clear relation between methylmercury contamination and cytogenetic damage in lymphocytes at levels well below 50 micrograms/gram, the level at which initial clinical signs and symptoms of mercury poisoning occur. The first apparent biological effect with increasing MeHg hair level was the impairment of lymphocyte proliferation measured as mitotic index (MI). The relation between mercury concentration in hair and MI suggests that this parameter, an indicator of changes in lymphocytes and their ability to respond to culture conditions, may be an early marker of cytotoxicity and genotoxicity in humans and should be taken into account in the preliminary evaluation of the risks to populations exposed in vivo. This is the first report showing clear cytotoxic effects of long-term exposure to MeHg. Although the results strongly suggest that, under the conditions examined here, MeHg is both a spindle poison and a clastogen, the biological significance of these observations are as yet unknown. A long-term follow-up of these subjects should be undertaken.

Chromosome fragility in hematologic disease presumably induced by environmental pollutants

Chromosome instability consists of chromosome abnoprmalities as multiple breaks in in metaphase chromosomes in syndromes of chromosaome instability such as fanconi's anemia (FA) which is mainly characaterized by bone marrow aplasia; some cases progress to acute leukemia. FA is a hereditary disease with recessive and monogenic transmission. This pair of mutated genes is related to chromosome fragility and therefore is responsible for the inefficiency of DNA repair. In normal individuals, these genes are assumed to be expressed normally, but their products ara insufficient to perform DNA repair when the intensity of the polluting agent lelads to exposure above basal levels. In the present study, the bone marrow of four patients with different hematologic diseases was submitted to cytogenetic analysis. Two had aplastic anemia, and one bad lymphoblastic leukemia. These patients were from towns unb the Amazon Region where the mercuri used for gold prospecting and the substances used and/or released in aluminium mining have been introduced into the environment. The last patient had fanconi's anemia and was used as a model in the discussion of the results. The cytogenetic findings were similar for all patients, the major ones being chromosome fragmentation and pulverization. In view of these findings, we believe that chromosome fragility, observed in the first three patients, presumably was induced by environmental pllutants

Cariótipo de paciente com leucemia mielóide crônica tratado com interferon / Karyotype of the chronic myeloid leukemia patient treated with interferon

Neste trabalho, estudamos citogeneticamente um paciente com LMC tratado com interferon. Foram analisadas 12 células metafásicas. O cromossomo Pb foi encontrado em 100 por cento das células analisadas e apenas uma apresentou isocromossomo 17q. Este achado, apesar de näo ser clonal, pode indicar prenúncio da fase blástica. Porém, o tratamento com interferon pode estar exercendo pressäo sobre as células i(17q), näo permitindo que proliferem bloqueando o início da fase blástica. Portanto acreditamos que o tratamento com interferon é capaz de sprimir as células com alteraçöes cromossômicas pós-philadelfia, melhorando o prognóstico do paciente