1114 RADIATION BIOLOGY 



tremendous variations in width of the epiphyseal plate and great 

 abnormality in the appearance of the whole metaphysis. 



MALE GENERATIVE SYSTEM 



Total-body irradiation, whether it is carried out with single or repeated 

 doses of X rays or 7 rays or single exposure to fast neutrons, produces the 

 same pattern of damage and repair in the testis. The degenerative 

 changes are mainly induced through injury to the free stem cells. With 

 all types and amounts of external and internal radiations that produce 

 cellular depletion, the testis is reduced in size and there is a gradual 

 cessation of spermatogenesis (Albers-Schonberg, 1903; Barratt and 

 Arnold, 1911-1912; Bergonie and Tribondeau, 1905; Heller, 1948b; 

 Regaud and Blanc, 1906; Schinz and Slotopolsky, 1925). 



A single total-body exposure of rabbits to 800 r of X rays destroys the 

 spermatogonia. This causes an interruption in the production of new 

 spermatocytes and consequently of spermia several weeks later. Cell 

 death, evidenced by dead spermatogonia (and only rarely by a dead 

 spermatocyte) 1 day after treatment, is less obvious at 3 and 5 days 

 (Heller, 1948b). By 9 days spermatogonia are inconspicuous in most 

 tubules, which contain only Sertoli cells, a decreased number of spermato- 

 cytes (some damaged), spermatids and spermia, and great numbers of 

 multinucleated and bizarre cells. Beginning regeneration (at 30 to 35 

 days) is indicated by the presence on the basement membrane of baso- 

 philic outstretched cells or very early spermatogonia (Heller, 1948b). 

 Some of the tubules even contain a few spermatocytes at this time. 

 Spermatogenesis returns to normal by four months in some specimens, 

 while in others the tubules contain Sertoli cells alone. There is some- 

 times edema of the intertubular connective tissue. 



After 600 r the cessation of spermatogenesis followed by regeneration is 

 similar to that after the higher dose except that not quite so many tubules 

 are depleted and regeneration begins earlier. Attempts at recovery are 

 indicated at 21 days by the presence in a few tubules of spermatogonia in 

 all stages of development, more tubules showing this appearance by 31 days 

 and at least half the tubules showing some degree of recovery by 45 days. 



In the rat the effects of 600 r of X rays on the testis are the same as in 

 the rabbit, even in time sequence. However, in different rats 132 days 

 after exposure, there are great differences in the degree of recovery. 



The damage to the mouse testis after 350 r of X rays is much like that 

 in the rabbit after 600 r except that regeneration begins earlier. 



The cumulative effect of repeated small doses of radiation is more 

 striking on the testis than on any other organ of the same animal, although 

 not quite so marked as on the ovary. The testes of mice irradiated daily 

 with 80 r of X rays show progressive damage. Twenty-four hours after 



