Abstract
To assess effects of low-dose neutrons on fetuses, the relative biological effectiveness (RBE) should be known. In mice, prenatal exposure of gamma-rays caused several effects: reduction of cell proliferation and retention of neurocyte migration in cerebral cortex. However there had been few studies of neutron effects on fetuses. Therefore, we analyzed number of apoptotic neurocytes in mouse cerebral cortex as a marker of neutron effects on fetuses and estimated RBE values. B6C3F1 fetal mice were exposed to 10MeV fast neutrons (0.05 ~ 1.0Gy) or 137Cs gamma-rays (0.4 ~ 2.0Gy) on day 13.5 of gestation and autopsied 24h later. Cross-sections at cerebral mid-plane were stained with HE or TUNEL method. Apoptosis of neurocytes were microscopically observed at cerebral cortex on HE stained sections and were quantitatively analyzed on TUNEL stained samples. Neurocyte death increased at manner of dose dependent for neutrons and also gamma-rays, and RBE was tentatively estimated to be about 3. [J Radiat Res 44:403 (2003)]
