Host: The Japan Radiation Research Society, Chairman of the 52nd Annual Meeting, Toshiteru Okubo (Radiation Effects Research Foundation)
The effects of low-dose gamma rays on the postnatal and prenatal development of mice as well as on the differentiation of neural crest cells were investigated. Pregnant females of C57BL/10JHir mice at 9 days of gestation were whole-body irradiated with a single acute dose of gamma rays. The effect was studied by scoring changes in the postnatal development of mice and in the white spot in the ventrum 22 days after birth. The percentage of pregnancy, birth, survival to day 22 and body weight at day 22 showed no change even in mice irradiated with 0.5 Gy gamma rays. Radiations elicit mid-ventral white spots in offspring 22 days after birth due to the inhibition of neural crest cell differentiation. The frequency of white spots in the mid-ventrum was increased from the dose of 0.25 Gy, and the size of white spots was also increased from the dose of 0.25 Gy. Irradiated 18-day-old embryos were dissected and effects of gamma rays on the number of living embryos, body weight, developmental anomalies, and the differentiation of hair bulb melanocytes were investigated in detail. In irradiated 18-day-old embryos, the litter size was not decreased even in 0.75 Gy. However, the abnormalities in tails were observed at the embryos irradiated with 0.1 Gy gamma rays and its frequency was increased with increasing dose. The hemorrhage at the base of tail and limbs was observed at the control embryos and its frequency was increased with increasing dose. Moreover, the number of hair bulb melanocytes in the dorsal and ventral skins decreased from 0.1 Gy-treated embryos, and gradually decreased with increasing dose. These results suggest that low-dose gamma rays have inhibitory effects on the prenatal development of tail and blood vessels as well as on the neural crest cell differentiation in mice.
