Chromosome Aberrations in Mouse Spermatocytes and Oocytes Exposed to 300R ϒ-Radiation: A Comparison

Abstract

<p>It has been repeatedly demonstrated that radiation induces chromosome aberrations in mouse oocytes and spermatocytes. However, the results of previous studies, in which the frequency of aberrations recovered from irradiated oocytes and spermatocytes were compared, are conflicting (reviewed by L. B. Russell, 1962, L. B. Russell, 1968). The development of new techniques for making chromosome preparations from oocytes (Edwards, 1965; Tarkowski, 1966) and spermatocytes (Evans et al., 1964) has made it possible to reinvestigate the radiosensitivities of spermatocytes and oocytes.</p> <p>In the present study, the frequency of chromosome aberrations recovered from irradiated dictyotene oocytes was compared to the frequencies of aberrations recovered from irradiated pachytene and diplotene spermatocytes.</p> <p>Oocytes and spermatocytes were collected from mature mice one day and five days after exposure to a single acute dose of 300R ϒ-radiation. At the time of irradiation, all of the oocytes were in dictyotene while the spermatocytes collected one day and five days post-irradiation were in diplotene and pachytene, respectively. The average number of oocytes collected from irradiated mice was no different from the average number collected from controls. Although the ability of oocytes collected one day post-irradiation to mature in vitro (58.0%) was not affected, significantly fewer (53.6%) of the oocytes cultured five days post-irradiation matured in vitro. Since the frequency of abnormal cells vas the same in oocytes cultured one day and five days post-irradiation, it is unlikely that oocytes with chromosome aberrations were selectively inhibited from maturing in vitro.</p> <p>The frequencies of chromosome aberrations in dictyate oocytes cultured one day and five days after irradiation were not significantly different from the frequency of aberrations in diplotene spermatocytes (20.7%). However, significantly more chromosome aberrations (32.0%) were recovered fraa irradiated pachytene spermatocytes than from either dictyate oocytes or diplotene spermatocytes. Some variation in the relative frequencies of aberrations was found.</p>