23 resultados para INDUCED CHROMOSOMAL INSTABILITY
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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5-azacytidine (5-azaC) treatment combined with cytosine arabinoside (ara-C) or caffeine were performed in vitro in Chinese hamster cells, CHO-K1 (wild-type) and xrs-5 (mutant) cell lines, in order to compare the cell response to the induction of chromosomal aberrations. Exponentially growing cells were treated with 5-azaC (4-16 uM) for 1 h, the cells were washed and incubated for 7 h, and 500 uM caffeine or 5 uM ara-C were added to the cultures for the last 2 h. In both cell lines, 5-azaC induced a significantly increase (P<0.01) in the frequencies of aberrations; in the combined treatments (5-azaC + Ara-C), a significant reduction (P<0.05) was observed for the aberrations which were randomly distributed. Caffeine had no influence at the same conditions. 5-azaC induced-DNA lesions were probably processed at S/G2 phase in a common pathway in both cell lines, but alternatively, 5-azaC may cause xrs-5 cells to revert to the wild-type.
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Measurements of the coefficient of thermal expansion on the spin-liquid candidate κ-(BEDT-TTF) 2Cu 2(CN) 3 have revealed distinct and strongly anisotropic lattice effects around 6 K - a possible spin liquid instability. In order to study the effects of a magnetic field on the low-temperature spin-liquid state, dilatometric measurements have been conducted both as a function of temperature at B = const. and as a function of field at T = const. While the 6 K anomaly is found to be insensitive to magnetic fields B ≤ 10 T, the maximum field applied, surprisingly strong B -induced effects are observed for magnetic fields applied along the in-plane b-axis. Above a threshold field of 0.5 T < B c ≤ 1 T, a jump-like anomaly is observed in the b-axis lattice parameter. This anomaly, which is located at 8.7 K at B = 1 T, grows in size and shifts to lower temperatures with increasing the magnetic field. Although the anomaly bears resemblance to a first-order phase transition, the lack of hysteresis suggests otherwise. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Contaminant driven genetic erosion reported through the inspection of selectable traits can be underestimated using neutral markers. This divergence was previously reported in the aquatic system of an abandoned pyrite mine. The most sensitive genotypes of the microcrustacean cladoceran Daphnia longispina were found to be lacking in the impacted reservoir near the entrance of the metal rich acid mine drainage (AMD). Since that divergence could be, at least partially, accounted for by mutagenicity and genotoxicity of the AMD, the present study aimed at providing such a characterization. The Allium cepa chromosomal aberration assay, using root meristematic cells, was carried out, by exposing seeds to 100, 10, 1, and 0.1 % of the local AMD. Chromosomal aberrations, cell division phases and cell death were quantified after the AMD exposure and after 24 and 48 h recovery periods. The AMD revealed to be mutagenic and genotoxic, even after diluting it to 1 and 0.1 %. Dilutions within this range were previously found to be below the lethality threshold and to elicit sublethal effects on reproduction of locally collected D. longispina clonal lineages Significant mutagenic effects (micronuclei and chromosomal breaks) were also found at 0.1 % AMD, supporting that exposure may induce permanent genetic alterations. Recovery tests showed that AMD genotoxic effects persisted after the exposure. © 2013 Springer Science+Business Media New York.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)