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In order to investigate the effect of low dose rate radiation and to evaluate the
combined effects of chemicals and radiation, chromosomes were analyzed in spleen
cells from the mice exposed to low dose rate radiation for a long periods and also from the mice treated with tobacco-specific nitrosamine NNK and radiation. Chromosomes were prepared from the spleen cells in F1 mice between gpt delta transgenic and SWR strains after irradiation for 483 days.
The total dose in these mice were OGy, 20mGy (0.04255 mGy/day), 400mGy (0.858 mGy/day) and 8Gy(16.56mGy/day). Frequencies of dicentric chromosome (die) per cell at each dose were 0.00042 (OGy), 0.00118(20mGy), 0.00233 (400mGy) and 0.02261 (8Gy), respectively. It may be worth to be mentioned that die was detected in mice irradiated at the lowest dose, 20mGy (dose rate: 0.04255mGy/day), although it was not significant statistically.
It may be also important that the frequency of die was increasing according to the total dose.
In the present study, we also analyzed chromosomes in gpt delta transgenic mice
treated with irradiation at a dose rate of0.5, 1.0, 1.5 mGy for 22h /day for 31days and NNK at a dose of 2mg/mouse/day. NNK treatment was performed for four days in the middle course of irradiation; Frequencies of dicentric per cells in mice exposed to only radiation were 0.0049 (OGy), 0.0039 (0.5mGy/day), 0.0134 (l.OmGy/day) and 0.0114(1.5mGy/day), respectively. On the other hand, frequencies of die in mice treated with NNK and radiation were 0 (OGy+NNK), 0.0031 (0.5mGy/day+NNK), 0.0045
(l.OmGy/day+NNK) and 0.00112 (1.5mGy/day+NNK). Thus, there was no
enhancement in the frequency of die in mice with combined treatment. Further
chromosome analysis should be performed in an increased number of metaphase.
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"
Frequency of dicentric chromosome in spleen from the mice exposed to low dose rate radiation and/or chemicals.
