X-RAYS AND REPRODUCTIVE ORGANS OF RAT 



331 



result, the number of follicles in the advanced stages of growth (<^ > 180/x), 

 and the volumes of the ovaries are increased. Besides, mean values for 480 

 follicles with antrum were found in the controls and for 819 in the exposed 

 rats. Apparently, during the first nine days after irradiation the oocytes in 

 the ovaries are stimulated to develop by the total-body X-irradiation. On the 

 other hand, there are data in the literatm-e, which register only the destruc- 

 tive effect of X-rays on the primary oocytes, but with no stimulating effect 

 (Spalding et al., 1957). We are inclined to believe that this can be explained 



10' 



- ^ 



10^ 



10' 



10^ 



I — I No, of primary 

 oocytes 



rr. No. of growing 

 ^ follicles 



m 



17 24 42-50 



Age of rats (days) 



Fig. 1. This graph shows the total number of ova cells present and the relationship between 

 the number of primary oocytes and the growing follicles as a function of time in the ovaries of 

 rats exposed when 8-day-old to 50 r and 100 r of X-rays. 



by the doses applied (750 and 3,000 r), which destroyed most of the primary 

 oocytes, the remaining number of primary oocytes being too small to allow 

 the phenomenon of stimulation to express itself. 



In 24-day-old female rats, i.e. 16 days after exposure, the total number of 

 germ cells decreased by 42 per cent. Nevertheless, the number of growing 

 follicles, the number of follicles in advanced stages of growth and the number 

 of mitotic divisions in granulosa cells in the ovaries of exposed rats did not 

 significantly differ from the control ovaries. Throughout our observation on 

 the rat ovaries up to 50 days of age, the percentage of growing foUicles was 

 higher in the exposed than in the control rats. 



