Chromosomal rearrangements induced in mouse spermatogonia by 14.5-MeV neutrons

Inbred CBA male mice were irradiated with 14.5MeV neutrons. Three acute doses, 75, 150 and 250 rad, and one chronic dose, 250 rad, were given. The percentages of affected spermatocytes as counted from reciprocal translocation which had been induced in spermatogonia were 0.7, 0.8 and 1.6 respectively for acute series and 2.2 after chronic exposure. The data could be fitted to a linear or concave curvilinear regression line. There seemed to be a slight increase of damage with dose, even if the percentages were generally lower than those reported earlier for fast neutrons with energies around 1 MeV. The existence of dose-relat effects is discussed, and the conclusion drawn so far is that there seems to be no such effect either for 1-MeV fast neutrons or 14.5-MeV high energy neutrons. The term "reversed dose-rate effect" as used earlier, relates to another phenomenon. The difference between the point estimates for the chronic and acute 250 rad series is not significant. The effectiveness of neutrons with energies around 14MeV versus neutrons with energies around 1 MeV is discussed.