抄録
In 1987, Planel et al. reported growth inhibition of Paramecium tetraurelia by shielding from background radiation. Here we examined this growth inhibition with an outperforming shield apparatus. We placed paramecium cultures in two identical chambers; the control chamber was a foam polystyrene box, and the shielded chamber was a foam polystyrene box but covered with aluminum film and surrounded by iron wall 15 cm thick and paraffin wall 10 cm thick. The temperature of both chambers was controlled by circulating water in constant temperature and the difference of the temperature between the control and shielded chambers was less than 0.1 degree C. Gamma ray dose rates, measured by a NaI scintillation counter, were 2.1 nGy/hr in the shielded chamber and 109 nGy/hr in the control chamber, and neutron, measured by a BF3 detector, was diminished to 1/6 in the shielded chamber. We observed proliferation of paramecia for 10 days, however, we could not find any differences of their growth. Under our condition we could not admit the growth inhibition by shielding of background radiation.
Acknowledgment: Prof. Y. Takagi (Nara Women's University) kindly helped us to culture Paramecium tetraurelia.
