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In order to investigate the biological effects of low dose radiation, the
chromosomes were analyzed in the spleen cells from the mice exposed to low dose rate
radiation for a long term. The Fl mice between gpt-delta transgenic and SWR strains were irradiated at the three kinds of dose rate (average 0,04255 mGy/day, 0.858 mGy/day and 16.56 mGy/day) of y-ray for 483 days. The total doses in these mice were approximately 20 mGy, 400 mGy and 8 Gy. The spleen tissues were disaggregated by squeezing and the lymphocytes were collected and cultured for about 46 - 48 hrs in the20% FCS-RPMI1640 medium containing Concanavarin A and Lipopolysaccharides.
Colcemid was added to the culture for 24 hours before starting the harvest. Mitotic cells
were obtained from 6, 7, 8 and 6 mice exposed to 0 mGy (control), 20 mGy, 400 mGy and 8 Gy, respectively. In the dicentric analysis, we counted only the typical dicentric chromosome due to the reciprocal reunion of the terminal regions of two chromosomes.
The frequency of a dicentric chromosome per metaphase was 0.0004, 0.0013, 0.0022
and 0.023 in mice exposed to 0 mGy, 20 mGy, 400 mGy and 8 Gy, respectively. We also analyzed dicentric chromosomes in splenic lymphocytes from the mice received acute irradiation (dose rate: 0.72 Gy/min). The Fl mice as mentioned above were acutely irradiated at four doses; 0.4 Gy, 1.0 Gy, 2.0 Gy and 4.0 Gy. The metaphases suitable for the analysis were obtained from all the mice except for the mice irradiated at 4.0 Gy. The frequencies of typical dicentric chromosomes were 0, 0.02, 0. 14 and 0.43 in mice received 0 Gy (control), 0.4 Gy, 1.0 Gy and 2.0 Gy, respectively. The dose dependency was clearly observed in both studies, although the dose rate was different in the study of low dose rate irradiation. The results in the present study also prove that the chromosome aberration may be the most valuable and sensitive biomarker to investigate the effect of low dose (rate) radiation.
会議概要（会議名, 開催地, 会期, 主催者等）
New Nuclear Research Symposium "Biological Responses to Low Dose Radiation"
Chromosome aberrations in the mouse spleen cells exposed to low dose (rate) radiation
