量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum Science and Technology.
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We have studied the effect of natural radiation on the chromosomes of lymphocytes of the residents in a HBRA and a control area in Southern China.
Individual dose was measured with electric pocket dosimeters (Aloka PDM-101) for 24 hours and/or thermoluminescence dosimeters (National UD-200S) for 2 months. The level of natural radiation at HBRA is 3 to 5 times higher than that in control area.
Cultures were set up within 8 hours after taking blood. Colcemid was supplemented in cultures from the beginning to the end for 48 hours. Chromosome preparations were made according to the high yield chromosome preparation method. Air-dry slides were stained with Giemsa or with fluorescent dyes using whole chromosome painting probes for Nos.1, 2, and 4.
Unstable types of chromosome aberrations (dicentrics and rings) were studied in 22 members of eight families in HBRA and 17 members of five families in CA. From each family three generations participated in this study. On average 2600 cells per subject were analyzed. 27 adults and six children in HBRA and 25 adults and eight children in CA were studied with respect to stable types, i.e., translocations. On average 4741 cells per subject were examined.
Increase of Dic and Ring was observed in HBRA where the dose rate was lower than one cGy per year. This dose rate is the condition that less than one track of radiation passes through one cell in two months. Therefore, there seems to be no threshold dose for the induction of chromosome aberration. Activation of DNA repair enzyme for adaptive response does not seem to be triggered at such low dose rate. In case of translocations, the frequencies were much higher than that of Dic+Rc both in HBRA and in control. Statiscally there was no difference in the frequencies between HBRA and control, but the frequencies in children were lower than those in adults in both groups. Individual variation was small in children while that in adults was large. To examine the effect of confounding factors on the production of chromosome aberrations, we compared smokers with non smokers. Smoking seems to be a factor inducing more chromosome aberrations than radiation in HBRA in the Southern China.
Chromosome aberrations induced by the radiation at the dose rate 3 to 5 times higher than that in the control are within the range of individual variation of total chromosome aberrations which are caused by all kinds of mutagenic factors, such as chemicals, radiation, and metabolic factors in the normal living conditions.
会議概要（会議名, 開催地, 会期, 主催者等）
6th International Conference on High levels of Natural Radiation and Radon Areas
Chromosome study in HBRA in Southern China
