Dose-response and large relative biological effectiveness of fast neutrons with regard to mouse fetal cerebral neuron apoptosis.
To evaluate the relative biological effectiveness (RBE) of low doses of neutrons on fetal nervous development, [C57BL/6J x C3H/He] hybrid (B6C3F1) mice were exposed to cyclotron-derived fast neutrons with peak energy of 10 MeV (0.02-1.0 Gy) or 137Cs-generated gamma-rays (0.1-2.0 Gy) on embryonic day 13.5. We then evaluated the incidence of neuronal apoptosis in the cerebral cortex 24 hours after irradiation. Neuronal apoptosis increased in a dose-dependent manner in both neutron- and gamma-ray-irradiated groups: even at the lowest dose, a minimal increase in the apoptotic index was noted in response to both types of radiation. The dose-response curves were best fitted to linear quadratic models, and the evaluated RBE was 9.8, which was considered to be large for a prenatal effect and acute tissue injury induced by a low dose of neutrons.
Low Dose Radiation Effects Research Project, National Institute of Radiological Sciences, Chiba, Japan. ishida@nirs.go.jp
Yuka
Y
Ishida
Yasushi
Y
Ohmachi
Yukiko
Y
Nakata
Takeshi
T
Hiraoka
Tsuyoshi
T
Hamano
Shinji
S
Fushiki
Toshiaki
T
Ogiu
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000196:embryology* / Q000473:pathology / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005214:Fast Neutrons; D020567:Fetal Weight / Q000528:radiation effects*; D005720:Gamma Rays; D051379:Mice; D008810:Mice, Inbred C57BL; D009928:Organ Specificity; D012062:Relative Biological Effectiveness