. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 272 JOHN H. D. BRYAN AND JOHN W. GOWEN point is: what are the relative levels of importance which may be ascribed to either process ? It appeared likely that a comparison of results following exposure to different dose levels of x-rays would shed more light on the nature of any rela- tionship between these proposed mechanisms. In our previous paper results ob- tained following exposure to 320 r of x-rays were reported. This present paper reports data obtained following exposure to a high dose of x-rays (2560 r). These data a
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 272 JOHN H. D. BRYAN AND JOHN W. GOWEN point is: what are the relative levels of importance which may be ascribed to either process ? It appeared likely that a comparison of results following exposure to different dose levels of x-rays would shed more light on the nature of any rela- tionship between these proposed mechanisms. In our previous paper results ob- tained following exposure to 320 r of x-rays were reported. This present paper reports data obtained following exposure to a high dose of x-rays (2560 r). These data are, where feasible, presented together with corresponding data from our 320 r experiment. As will be seen, the available evidence suggests that both mechanisms play a role in the observed radiation response of spermatogonia, the level of importance ascribable to either one depending upon the dosage levels of radiation employed. O oc \- z O O 200- 150- •—• SPERMATOGONIA-INTERPHASE O—O SPERMATOGONIA-MITOTIC A—A SPERMATOCYTE -CHROMATIN Ld O o: LU 10 35 10 DAYS AFTER X-RAYS (2560r) 28 FIGURE 1. Strain Ba. Incidence of spermatogonia and spermatocytes at different times following 2560 r of x-rays. MATERIALS AND METHODS The animals chosen were 58-day-old males of strains BALB/Gw (hereinafter referred to as Ba) and S. These inbred strains of mice differ in their sensitivity to mouse typhoid. The experimental animals were irradiated in plastic tubes and were exposed to a dose of 2560 r (250 pkv, 30 ma; filtration mm. Cu, 1 mm. Al; anode-target distance cm., dose rate 430 r/min.). The irradia- tion was delivered to the pelvic region only, the rest of the body being shielded with lead. These conditions of irradiation are, except for the x-ray dose, identical with those of our previous studies (Bryan and Go wen, 1956). Control and irradiated animals were killed at 1, 8 and 24 hours, 3, 5, 10, 16. Please note that these images are extracted from scanned page images t
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