title: Studies on radiation-induced chromosome aberrations in mouse spermatocytes. II. Dose-response relationships of chromosome aberrations induced at zygotene stage in mouse primary spermatocytes following fast neutron- and 60Co gamma-irradiations.
abstract: The chromosome aberrations induced at zygotene stage in mouse spermatocytes following exposures to fast neutrons and 60Co gamma-rays were examined at diakinesis-metaphase I. The dose-response relationships were well fitted to linear equation for deletion-type aberrations and to linear-quadratic equation for exchange-type aberrations in 60Co gamma-irradiation group. In fast neutron-irradiation group, the dose-response relationships were well fitted to linear equations for deletion- and exchange-type aberrations. The rate of deletion-type aberrations was remarkably high for fast neutrons, about 6 times higher than that after 60Co gamma-irradiation. The main types of chromosome aberrations observed were iso-chromatid breaks or fragments and chromatid exchanges in both irradiation groups as well as X-irradiation. These results indicate that there is a possibility that two double-strand breaks are induced simultaneously at iso-locus position in sister chromatids by a single track of radiations. Production of such single-track-induced two double-strand breaks in iso-chromatids may be very frequently expressed as iso-chromatid-type deletions in the high LET fast neutron-irradiation group. On the contrary, in the low LET 60Co gamma- or X-irradiation group, the above-mentioned mechanism may not be so effective for contribution to chromosome aberration induction in mouse spermatocytes. This mechanism was discussed in detail.
mesh_terms: D000818:Animals; D002869:Chromosome Aberrations; D002872:Chromosome Deletion; D002875:Chromosomes / Q000528:radiation effects; D003037:Cobalt Radioisotopes; D004307:Dose-Response Relationship, Radiation; D004735:Energy Transfer; D005214:Fast Neutrons; D005720:Gamma Rays; D008297:Male; D008540:Meiosis / Q000528:radiation effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D009502:Neutrons; D011839:Radiation, Ionizing; D012854:Sister Chromatid Exchange; D013090:Spermatocytes / Q000528:radiation effects*
chemical_list: D003037:Cobalt Radioisotopes