Hisao Yamashita

EFFECTS OF BETA RAYS UPON A SINGLE NERVE FIBER

Summary We have made some physiological investigations of the response of a single nerve fiber to beta rays. Small exposures, up to 20 millicurie-hours at a distance of 1 mm in air with the filter shown, showed no effect. Moderate exposures (20-30 mc h.) evoked an injury current from the irradiated region. At higher exposures, the threshold value of stimulus increased and the action current decreased in strength and duration, and ultimately disappeared at 70 millieurie-hours. Complete breakdown occurred at the highest doses.

Effects of radioactive fallout on the pregnant woman and the fetus

The levels of 90Sr and 137Cs in human placenta, fetus and diet were determined by radiochemical methods during the period from March 1966 to December 1968. The possible effects of these radionuclides on the pregnant woman and the fetus were discussed. The metabolic characteristics of both 90Sr and 137Cs were also discussed on the basis of estimates of discrimination factors and observed ratios of these radionuclides. As a result of the analyses, the dose rate to the human placenta resulting from deposition of 90Sr in the organ was estimated at about 0.003 mrem/month and that of 137Cs at about 0.013 mrem/month. The dose rate to the total body resulting from the body burden of these radionuclides in the mother was estimated at about 0.012 mrem/ month. These values are much smaller than the monthly dose from 40K normally existing in the body. It was rather difficult to draw definitive conclusions concerning the possible correlation between the 90Sr fallout and the annual changes of infant mortality rates in ...