Article

Analysis of radiation-induced micronuclei in two-cell human-hamster embryos using telomeric and centromeric FISH probes

Department de Biologia Cel.lular i Fisiologia, Universitat Autònoma de Barcelona, Bellaterra, Spain.
Cytogenetics and cell genetics 02/1996; 74(1-2):102-6. DOI: 10.1159/000134392
Source: PubMed

ABSTRACT Simultaneous, fluorescent in situ hybridization using a centromeric human alpha satellite DNA probe and a telomeric DNA probe was used to analyze the chromosome content of micronuclei induced in two-cell human-hamster embryos by in vitro gamma-ray irradiation of human spermatozoa. In unirradiated samples, about 26% of micronuclei were centromere positive, indicating that both structural chromosome aberrations and numerical changes are involved in the spontaneous production of micronuclei. After exposure of spermatozoa to radiation, a significant increase in the number of micronuclei was found. About 77% of induced micronuclei contained only telomeric signals suggesting that they originated from acentric fragments. However, both centromere-positive and centromere-negative micronuclei increased with radiation dose. These results are consistent with the well known clastogenic effect of ionizing radiation and with its weak aneugenic effect.

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    • "For FISH analysis, to identify centromeres, 50 MN for each individual and type of culture on coded slides in a blind study were analyzed for the presence of a fluorescent signal. MN were classified as centromere-negative (CN − ) or centromerepositive (CN + ) by considering the presence of a hybridization signal in a MN as a direct indication of the presence of a centromere [32]. Among CN + MN, signals of different intensities were found due to variable amounts of alpha-satellite DNA on different human chromosomes [33]. "
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    • "Although the micronucleus test can be used to evaluate the residual lesions left after occupational or accidental exposure to radiation, this test cannot be used to estimate the dose received at the testicular level due to the different radiosensitivities of spermatogenic cells. Since micronuclei may contain acentric fragments [120] as well as centric fragments or whole chromosomes with damaged centromeres [121], and even groups of chromosomes that produce large micronuclei [122], we decided to carry out a FISH study with telomeric and centromeric probes for all human chromosomes to characterize the chromosomal content of micronuclei [123]. The results showed that over 75% of micronuclei were centromere-negative, indicating that they originated from acentric fragments. "
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Laura Tusell