RESUMO
The radiation accident in focus here occurred in a section of Goiânia (Brazil) where more than a hundred individuals were contaminated with 137Cesium on September 1987. In order to estimate the absorbed radiation doses, initial frequencies of dicentrics and rings were determined in 129 victims [A.T. Ramalho, PhD Thesis, Subsidios a tecnica de dosimetria citogenetica gerados a partir da analise de resultados obtidos com o acidente radiologico de Goiânia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil, 1992]. We have followed some of these victims cytogenetically over the years seeking for parameters that could be used as basis for retrospective radiation dosimetry. Our data on translocation frequencies obtained by fluorescence in situ hybridization (FISH) could be directly compared to the baseline frequencies of dicentrics available for those same victims. Our results provided valuable information on how precise these estimates are. The frequencies of translocations observed years after the radiation exposure were two to three times lower than the initial dicentrics frequencies, the differences being larger at higher doses (>1 Gy). The accuracy of such dose estimates might be increased by scoring sufficient amount of cells. However, factors such as the persistence of translocation carrying lymphocytes, translocation levels not proportional to chromosome size, and inter-individual variation reduce the precision of these estimates.
Assuntos
Radioisótopos de Césio/efeitos adversos , Aberrações Cromossômicas/genética , Hibridização in Situ Fluorescente , Liberação Nociva de Radioativos , Brasil , Células Cultivadas , Feminino , Seguimentos , Raios gama/efeitos adversos , Humanos , Linfócitos/efeitos da radiação , Masculino , Radiometria , Estudos Retrospectivos , Translocação Genética/efeitos da radiaçãoRESUMO
For conducting an adequate human cancer risk assessment of inorganic arsenic (As) in the low-dose region, it is important to establish its mode of action. In this context, the nature of genotoxic effects induced by this agent is of considerable interest. However, the results from such investigations in human have been conflicting. In an attempt to resolve this issue, the clastogenic and aneugenic potential of As was investigated in women and children from native population exposed to high levels (around 0.2 mg/l) of natural As via drinking water in San Antonio de los Corbes in the Andean region of Salta, Northwestern Argentina. The water did not contain elevated levels of heavy metals, such as lead or cadmium, nor was the investigated population exposed to significant industrial pollution or to pesticides. An ethnically similar control group from Rosario de Lerma, Salta, where only extremely low concentration of arsenic in drinking water could be detected, was used as a control. To evaluate the genotoxic effects in peripheral blood lymphocytes, micronuclei (MN) in binucleated cells, sister-chromatid exchanges (SCEs) and the fluorescence in situ hybridization technique (FISH) in combination with chromosome specific DNA libraries were employed. The data obtained clearly indicate a highly significant increase in the frequency of MN and of trisomy in lymphocytes from exposed children and women in comparison with controls, but no notable effects were found on the frequencies of SCEs, specific translocations, or on cell cycle progression. As supported by FISH analysis, at least a proportion of MN appears to originate from whole chromosome loss. An additional finding was the unusually low background levels of MN in unexposed individuals from this ethnic group as compared to other populations, e.g., Caucasians.
Assuntos
Arsênio/toxicidade , Aberrações Cromossômicas , Mutagênicos/toxicidade , Poluentes Químicos da Água/toxicidade , Abastecimento de Água , Adolescente , Adulto , Argentina , Criança , Feminino , Humanos , Hibridização in Situ Fluorescente , Testes para Micronúcleos , Pessoa de Meia-Idade , Troca de Cromátide Irmã , TrissomiaRESUMO
Several primary and transformed human cell lines derived from cancer prone patients are employed routinely for biochemical and DNA repair studies. Since transformation leads to some chromosomal instability a cytogenetic analysis of spontaneous chromosome aberrations in fibroblast cell lines derived from patients with Fanconi anaemia (FA), ataxia telangiectasia (AT), and in lymphoblastoid cell lines derived from patients with Bloom's syndrome (BS), was undertaken. Unstable aberrations were analysed in Giemsa stained preparations and the chromosome painting technique was used for evaluating the frequencies of stable aberrations (translocations). In addition, the frequency of sister-chromatid exchanges (SCEs) was determined in differentially stained metaphases. The SV40-transformed fibroblasts from these cell lines have higher frequencies of unstable aberrations than the primary fibroblasts. In the four lymphoblastoid cell lines derived from BS patients higher frequencies of spontaneously occurring chromosomal aberrations in comparison to normal TK6wt cells were also evident. The frequency of spontaneously occurring chromosome translocations was determined with fluorescence in situ hybridisation (FISH) and using DNA libraries specific for chromosomes 1, 2, 3, 4, 7, 8, 11, 14, 19, 20 and X. The translocation levels were found to be elevated for primary FA fibroblasts and lymphoblastoid cells derived from BS patients in comparison with control cell lines, hetero- and homozygote BS cell lines not differing in this respect. The SV40-transformed cell lines showed very high frequencies of translocations independent of their origin and almost every cell contained at least one translocation. In addition, clonal translocations were found in transformed control TK6wt and AT cell lines for chromosomes 20 and 14, respectively. The spontaneous frequencies of SCEs were similar in transformed fibroblasts derived from normal individuals and AT patients, whereas in SV40-transformed FA cells these were higher (4-fold). Among cell lines derived from BS patients, heterozygote lines behaved like control, whereas in homozygote cell lines very high frequencies of SCEs (about 12-fold) were evident.