THE REACTION OF TESTICLES IN WHITE MICE FOLLOWING WHOLE-BODY CHRONIC GAMMA IRRADIATION WITH Co$sup 6$$sup 0$

The injury and the reparative ability of the testicles in white mice following an 8-day and 3 to 3.5-month continuous irradiation with Co/sup 60/ gamma rays (100, 500, and 1,000 r, the dose rate being from 1.1 to 125 r per 24 hours) were studied. In irradiation with doses causing a depression of spermatogenesis, a dissppearance of various types of cells of the germinal epithelium was noted at definite periods. This dependsd upon the biological cycle of development of these cells in the process of differestiation, and permitted the duration of these cycles to be determined. In 8-day irradiation with Cow gamma rays (600 to 1,000 r) the reparative processes appear in the injured testicular epithelium later than after the same doses of irddiation of short duration Another group of mice was irradiated with a dose of 1,000 r. the duration of irradiation being 3.5 months and the dose rate 8.7 per 24 hours. After a temporary period of depression of spermatogenesis the reparative processes and the parial reestablishment of spermatogenesis was noted 30 days after the beginning of irradiation (although the irradiation was still continued). The second depression of spermatogenesis appeared in the 60 days following a more prolongedmore » irradiation. The reestablishment of spermatogenesis against the background of continuing irradiation was evidently caused by the mobilization of compensatory mechanisms. After a 3-month irradiation in the dose of 500 and 100 r no radiobiological effect was revealed in the histological sections of the testicles. This may be due to the important role played by the reparative processes in the testicle, and confirms the role of physiological regeneration as one of the factors decreasing the sensitivity of the tissues in definite conditions of irradiation (auth)« less