838 



RADIATION BIOLOGY 



and Miller perhaps indicate not the absence of killing, but rather the 

 rapid disappearance of degenerating cells. This would also explain the 

 fact that the number of degenerating cells found by those investigators 

 who have reported seeing them is not high enough, at any one time, to 

 account for the magnitude of the reduction in number of spermatogonia. 



Table 12-7. Litter Size in Poststerile-period Matings of Irradiated Males 



Reference 



Strandskov(1932). 



Snell (1933b) 



Hertwig (1938a). 



Species 



Guinea pig 

 Guinea pig 



Mouse 

 Mouse 



Snell and Aebersold 

 (1937) 



Mouse 

 Mouse 

 Mouse 

 Mouse 

 Mouse 

 Mouse 

 Mouse 

 Mouse 

 Mouse 

 Mouse 



Radiation 



Control 

 •X rays 



Control 

 X rays 



Mouse 

 Mouse 



Russell et ah' ". 



Mouse 

 Mouse 



Control 

 X rays 

 X rays 

 X rays 

 X rays 

 X rays 

 X rays 

 X rays 

 X rays 

 X rays 



Dose, r 



173-2592 



600-800 



Control 

 Neutrons 



Control 

 X rays 



200 



400 



500 



600 



800 



1000 



1200-1400 



1500-1600 



Total irrad. 



No. of 

 litters 



140 

 62 



24 



4 



Mean 



litter 



size 



2.69 

 2.16 



7.71 

 8.00 



120-140 "r" 6 



600 



Per cent 



of 



control 



litter 



size 



80 



104 



9 

 4 



9,710 

 12,986 



8.44 

 5.75 



5.75 



5.58 



95 

 98 



102 

 88 

 91 

 97 



103 

 84 

 95 



68 



97 



" Not given by Hertwig. Calculated as weighted mean of mean litter sizes for 

 each dose. 



b Cyclotron neutrons measured on r scale of Victoreen condenser-type dosimeter. 



c Unpublished data collected by W. L. Russell, Josephine S. Gower, Gloria J. Jasny, 

 Elizabeth M. Kelly, Mary H. Major, and Patricia A. Sarvella. Litter size recorded 

 three weeks after birth. 



The view that spermatogonia are killed is supported by extensive data 

 showing that cells of other rapidly dividing animal tissues are destroyed 

 by moderate doses of radiation and that the degeneration occurs at cell 

 division. It, therefore, seems plausible to attribute at least the major 

 part of the radiation-induced reduction in number of spermatogonia, 

 and the consequent sterile period, to dominant cell lethals. If this 

 interpretation is correct, then dominant lethals are apparently induced 



