| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2000: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1999: ¥600,000 (Direct Cost: ¥600,000)
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| Research Abstract |
1. X-ray irradiation To evaluate the biological effects of environmental radiation, two groups of rats were irradiated with X-ray (31 keV). The first group was irradiated with the main X-ray and the second group was preliminarily irradiated with low-level X-ray, then, irradiated with the main X-ray again. The absorbed dose for the main X-ray irradiation was 0.5 Gy / rat, and for the preliminarily X-ray irradiation was 0.09 Gy/rat.
After the main X-ray irradiation, the SOD activity of rat's liver and spleen was measured by the nitrite method for both groups, which increased to 27% higher than its normal level at 6h after X-ray irradiation, and reduced to its normal level.
It is noted that, after X-ray irradiation, the SOD activity of the first group temporarily reduced to 15% lower than its normal level, although it increased again as described above. It must be emphasized that there was no reduction of the SOD activity of the second group after the main X-ray irradiation. It seems to show the important significance of the preliminary low-level X-ray irradiation.
2. Environmental ^<222>Rn. The rapid method for preparing known amounts of ^<222>Rn was developed and the mouse was exposed to ^<222>Rn for 48h. The lung of the mouse was measured with a Ge spectrometer, and the gamma-emitting daughter of ^<222>Rn, that is, ^<214>Bi on the lung was determined. During 3.5h, ^<222>Rn and its daughters came to transient equilibrium and all of these nuclides have the same radioactivity. Thus, absorbed dose due to ^<222>Rn was estimated. Since a detailed investigation of low-level radiation exposure might lead to a better understanding of the mechanisms of the radiation hormesis, the authors developed the method for determining the environmental ^<222>Rn. Based on the results, the experiment to evaluate the biological effects due to the environmental ^<222>Rn is underway.
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