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Biological dosimetry in a radiation accident
254
Abstracts/Mutation Research 360 (1996) 201-300
to the inactivation of one copy of X chromosome in female somatic cells. In this study the in situ hybridization of binucleated cells with a X centromeric probe has been used to investigate the role of chromosome loss (CL) and non-disjunction (ND) in the age-related malsegregation of sex chromosomes in peripheral lymphocytes of female donors. Whole blood cultures were established from 12 healthy non-smoking women aged from 25 to 56 years. Cytochalasin B (6 Ixg/ml) was added 44 h after PHA stimulation and binucleated cells were collected at 60 h. Slides from all donors were hybridized with a X chromosome centromeric probe and for five donors slides were separately hybridized with a chromosome 1 centromeric probe. One thousand binucleated cells were scored on each slide. Within the population investigated, the frequency of micronuclei (MN) encompassed a quite large interval (1 to 33 MN in 1000 scored cells), with a slight correlation with age ( p < 0.05). X centromere positive MN ranged from 1 to 25%0 and displayed a positive correlation with age ( p < 0.05). Out of 272 scored MN, 172 (63.2%) contained at least one copy of X chromosome. The frequencies of CL and ND ranged from 0 to 16.9%o (mean 7.5%0) and from 2.0%~ to 13.3%o (mean 5.7%0) respectively. No statistically significant difference was observed between CL and ND, indicating that both events contribute to X chromosome malsegregation in vitro at a similar extent. A small but not negligible fraction of binucleated cells with 2 and 6 copies of X chromosome was observed in all donors. These cells are supposed to arise from parent monosomic and trisomic types, indicating that X chromosome malsegregation may occurs in vivo as well. Also the incidence of these putative aneuploid types in peripheral lymphocytes was significantly related to the age of donors. The parallel analysis of the segregation of chromosome 1 confirmed the greater susceptibility (about 10-fold) of X chromosome to malsegregate with respect to autosomes. Finally, the analysis of X chromosome distribution demonstrated that in a relevant portion of unbalanced cells both X chromosome homologs were involved. The frequency of these multiple events was greater than that expected by chance, suggesting that the malsegregation of a homologous may impair the segregation of the other one and possibly of other chromosomes.
5-11
Biological dosimetry in a radiation accident C. Lindholm a, S. Salomaa ~, W. Paile ~, M. Tekkel b, T. Veidebaum b; a Finnish Centre for Radiation and Nuclear Safety, Laboratory for Biological Dosimetry, P.O.Box 14, FIN-00881 Helsinki, Finland, b Institute of Experimental and Clinical Medicine, Hiiu 42, EE0016 Tallinn, Estonia Analysis of chromosomal aberrations in peripheral blood lymphocytes was used in the assessment of radiation exposure of eight persons involved in a radiation accident in Kiisa, Estonia. A high-activity radiation source probably originating from a sterilization device was discovered in a private house in November 1994. During 4 weeks it had been irradiating several people, causing the death of one of them and acute radiation effects (blood count changes and/or skin bums) to four others. Based on the frequency of dicentric chromosomes the four people with symptoms were estimated to have received doses above 1 Gy and one other above 0.5 Gy. In addition to conventional chromosomal aberration (CA) analysis from Giemsa stained slides, stable chromosome aberration (translocation) analysis was performed. Fluorescence in situ hybridization (FISH) was applied with paints for chromosomes 1, 2 and 4. To avoid misclassification of dicentrics for translocations, a centromere specific probe was acquired. Between 1222-1500 metaphases were scored from each person. The yield of dicentrics in the FISH analysis agreed well with the results obtained from the conventional CA studies, thus confirming the dose estimation of those persons exposed. Translocation frequencies were equal to those for dicentrics in five persons. In three cases the frequencies were much higher, which partially reflects the higher background level of translocations and partially was due to the presence of clonal translocations. A key question in biological dosimetry of old exposures is whether the frequency of translocations can be assumed to be truly stable. To clarify this, the aberration rates of these exposed people will be followed till future.
Abstracts/Mutation Research 360 (1996) 201-300
to the inactivation of one copy of X chromosome in female somatic cells. In this study the in situ hybridization of binucleated cells with a X centromeric probe has been used to investigate the role of chromosome loss (CL) and non-disjunction (ND) in the age-related malsegregation of sex chromosomes in peripheral lymphocytes of female donors. Whole blood cultures were established from 12 healthy non-smoking women aged from 25 to 56 years. Cytochalasin B (6 Ixg/ml) was added 44 h after PHA stimulation and binucleated cells were collected at 60 h. Slides from all donors were hybridized with a X chromosome centromeric probe and for five donors slides were separately hybridized with a chromosome 1 centromeric probe. One thousand binucleated cells were scored on each slide. Within the population investigated, the frequency of micronuclei (MN) encompassed a quite large interval (1 to 33 MN in 1000 scored cells), with a slight correlation with age ( p < 0.05). X centromere positive MN ranged from 1 to 25%0 and displayed a positive correlation with age ( p < 0.05). Out of 272 scored MN, 172 (63.2%) contained at least one copy of X chromosome. The frequencies of CL and ND ranged from 0 to 16.9%o (mean 7.5%0) and from 2.0%~ to 13.3%o (mean 5.7%0) respectively. No statistically significant difference was observed between CL and ND, indicating that both events contribute to X chromosome malsegregation in vitro at a similar extent. A small but not negligible fraction of binucleated cells with 2 and 6 copies of X chromosome was observed in all donors. These cells are supposed to arise from parent monosomic and trisomic types, indicating that X chromosome malsegregation may occurs in vivo as well. Also the incidence of these putative aneuploid types in peripheral lymphocytes was significantly related to the age of donors. The parallel analysis of the segregation of chromosome 1 confirmed the greater susceptibility (about 10-fold) of X chromosome to malsegregate with respect to autosomes. Finally, the analysis of X chromosome distribution demonstrated that in a relevant portion of unbalanced cells both X chromosome homologs were involved. The frequency of these multiple events was greater than that expected by chance, suggesting that the malsegregation of a homologous may impair the segregation of the other one and possibly of other chromosomes.
5-11
Biological dosimetry in a radiation accident C. Lindholm a, S. Salomaa ~, W. Paile ~, M. Tekkel b, T. Veidebaum b; a Finnish Centre for Radiation and Nuclear Safety, Laboratory for Biological Dosimetry, P.O.Box 14, FIN-00881 Helsinki, Finland, b Institute of Experimental and Clinical Medicine, Hiiu 42, EE0016 Tallinn, Estonia Analysis of chromosomal aberrations in peripheral blood lymphocytes was used in the assessment of radiation exposure of eight persons involved in a radiation accident in Kiisa, Estonia. A high-activity radiation source probably originating from a sterilization device was discovered in a private house in November 1994. During 4 weeks it had been irradiating several people, causing the death of one of them and acute radiation effects (blood count changes and/or skin bums) to four others. Based on the frequency of dicentric chromosomes the four people with symptoms were estimated to have received doses above 1 Gy and one other above 0.5 Gy. In addition to conventional chromosomal aberration (CA) analysis from Giemsa stained slides, stable chromosome aberration (translocation) analysis was performed. Fluorescence in situ hybridization (FISH) was applied with paints for chromosomes 1, 2 and 4. To avoid misclassification of dicentrics for translocations, a centromere specific probe was acquired. Between 1222-1500 metaphases were scored from each person. The yield of dicentrics in the FISH analysis agreed well with the results obtained from the conventional CA studies, thus confirming the dose estimation of those persons exposed. Translocation frequencies were equal to those for dicentrics in five persons. In three cases the frequencies were much higher, which partially reflects the higher background level of translocations and partially was due to the presence of clonal translocations. A key question in biological dosimetry of old exposures is whether the frequency of translocations can be assumed to be truly stable. To clarify this, the aberration rates of these exposed people will be followed till future.