PHYSIOLOGY OF RADIATION INJURY 999 



gonia are most sensitive, thus accounting for the delay between irradia- 

 tion and the diminution in sperm count (Eschenbrenner and Miller, 

 1950; Fogg and Cowing, 1951). Prior to the development of oligo- 

 spermia, however, matings by the irradiated male result in a smaller 

 than normal litter size, which may be explained by chromosome trans- 

 locations in the sperm cells (Brenneke, 1937; Snell, 1935). This decrease 

 in litter size and associated evidence of arrested segmentation of fertil- 

 ized ova (Parkes, 1948) appear in the dosage range between 250 and 500 r. 

 Local and total-body irradiation yield similar findings in the testes (Fogg 

 and Cowing, 1951). At lower dosages, recovery is essentially complete, 

 while no recovery occurs in mice subjected to testicular irradiation at 

 2000 r. After 5000 r the interstitial cells remain intact (Fogg and Cow- 

 ing, 1952a). The human being may be considerably more sensitive than 

 rodents in terms of temporary or permanent sterility (Glucksmann, 1947). 

 Sterility induced by 2000 r in mice and 4500 r in rats does not result in 

 feminizing changes in the submaxillary gland, which are a characteristic 

 consequence of castration (Fogg and Cowing, 1952b). " Castration cells " 

 do, however, appear in the pituitary after sterilizing irradiation (Liebow, 

 Warren, and DeCoursey, 1949). 



The situation regarding physiological effects of irradiating the ovaries 

 seems to be somewhat more complicated. While temporary sterility 

 may be produced by 170 r to the human ovaries (Glucksmann, 1947; 

 Martin, 1950) and permanent sterility by less than twice this dose, it has 

 nevertheless been customary to treat sterility with similar dosages, and 

 pregnancies have been reported in 35 per cent of a large series of women, 

 believed to be sterile, after X irradiation of the ovaries with about 175 r 

 and of the pituitary with 225 r (Kaplan, 1949). The ovarian dosages 

 required to produce permanent amenorrhea vary within wide limits 

 (Liebow, Warren, and DeCoursey, 1949). In evaluating the effect of 

 radiation on the human ovary, it is well to remember that amenorrhea 

 does not necessarily imply inability to conceive. Mice show a temporary 

 reduction in the frequency of estrus after 200 r and temporary abolition 

 of estrus after 400 r (Bischoff et al., 1944). It would appear that second- 

 ary sex characters are more sensitive to gonadal irradiation in the female 

 than in the male (Bloom and Bloom, Chap. 17). Consideration of the 

 circumstances involved in the production of ovarian tumors in mice after 

 local X irradiation with 200 r suggests that this dosage, if delivered to all 

 of the ovarian tissue, results in a gonadotrophs response by the pituitary 

 (Lick, Kirschbaum, and Mixer, 1949). 



Bone and Cartilage. Responses of these tissues have been described 

 thoroughly by Bloom and Bloom (Chap. 17). Retardation of bone 

 growth following moderate irradiation of the growing areas is a matter of 

 some concern to radiotherapists treating younger individuals, since 

 recovery is likely to be incomplete following 1000 or 2000 r or more. 



