STUDIES ON INDUCTION OF TRANSLOCATIONS IN MOUSE SPERMATOGONIA .2. EFFECTS OF FAST NEUTRON IRRADIATION

The rate of induction of reciprocal translocations by fast neutron irradiation of mouse spermatogonia was studied by cytological examination of descendant spermatocytes. With acute irradiation (49-55 rad/min) the frequency of affected spermatocytes rose to a maximun of 8.7% at 100 rad, falling abruptly at higher doses to 1.6% at 220 rad. With chronic irradiation over 12 weeks, however, no such fall-off was found. Instead, the yield at 214-rad neutrons was 21.7%, while that at 62-rad was 3.3%, which is significantly less than expected on a linear hypothesis. If one assumes linearity at low doses, the neutron-X RBE for acute irradiation is about 4 and the neutron-γ RBE for chronic irradiation is about 20-25. © 1969.