[show abstract][hide abstract] ABSTRACT: Effects of low dose rate radiation on the process of carcinogenesis induced by a chemical carcinogen were examined. ICR female mice, 35 or 36 mice for each group, were kept and exposed to 137 Cs gamma-rays in the long-term low dose rate irradiation facility at the Central Research Institute of Electric Power Industry at a dose rate of 0.3, 0.96, or 2.5 mGy/h. Thirty-five days later, the mice were injected in the groin with 0.5 mg of 20-methylcholanthrene (MC) dissolved in olive oil, and irradiation was continued. Tumours started to appear 2 months after MC injection. Cumulative tumour incidences after 216 days following MC injection were 94% in the mice irradiated at 0.3 mGy/h, 76% at 0.95 mGy/h, 89% at 0.30 mGy/h, and 94% in non-irradiated control mice. The difference between the tumour incidence in the control mice and that in the mice irradiated at 0.95 mGy/h was statistically significant. These results indicate the suppressive effect of low dose rate irradiation on the process of tumour induction initiated by MC with an optimum dose rate of approximately 1 mGy/h.
Int. J. Low Radiation International Journal of Low Radiation. 01/2003; 1(1):142-146.
[show abstract][hide abstract] ABSTRACT: Female ICR mice, 6 weeks old, 35 in each group, were exposed to gamma-rays from a 137Cs source in the long-term low-dose rate irradiation facility at the Central Research Institute of Electric Power Industry (CRIEPI). The dose rate was 2.6 (A), 0.96 (B), or 0.30 mGy/h (C). Thirty-five days later, the mice were injected in the groin with 0.5 mg of methylcholanthrene (MC) dissolved in olive oil and irradiation was continued. Cumulative tumor incidences after 216 days following MC injection were 89% in group A, 76% in group B, and 94% in group C. The one in the non-irradiated control group was 94%. The difference in the tumor incidence between the control and position B was statistically significant, indicating the suppressive effect of the low-dose rate irradiation on the process of MC-induced carcinogenesis with an optimum dose rate around 1 mGy/h.
[show abstract][hide abstract] ABSTRACT: A photoluminescence glass dosimeter, GD-301, was applied to the measurement of low absorbed doses in mice exposed to low-dose rate 137Cs gamma-rays. The dosimeter system consists of small rod-shaped glass chip detectors capable of embedded in the body of a mouse and an automatic readout device equipped with a standard detector irradiated with 137Cs gamma-source. The measured absorbed doses were compared with the "exposure" estimated by an ionization chamber and with the doses measured by a BeO:Na thermoluminescence system. The results clearly demonstrate the superiority of the glass dosimetry regarding simplicity of operation, stability of long-term dose accumulation and good detector uniformity, which allow accurate tissue dosimetry.
Journal of Radiation Research 07/2000; 41(2):129-37. · 1.45 Impact Factor