MAMMALIAN TESTIS 



329 



TABLE 5.2 



Characteristic cell associations at each stage of the cycle of the seminiferous epithelium 

 (From E. F. Oakberg, Am. J. Anat., 99, 391, 1956.) 



Stage of Cycle 



Spermatogonia 



Type A 



Intermediate 

 Type B 



Spermatocytes I 

 First Layer 



Second layer. . . , 

 Spermatocytes II 



Spermatids (see Fig. 1) 



First layer 



Second layer 



15 



10 



Z 



Dip 



P 

 Dia 

 M-I 



S 

 Mil 



12 



A 



In 

 B 

 MI 



S 



= Spermatogonia type A 

 = Intermediate type sperm; 

 = Si^erniatogonia type B 

 = First meiotic division 

 = Secondary spermatocyte 



)goni 



M-II = Second meiotic division 



R = Resting 

 L = Leptotene 

 Z = Zygotene 

 P = Pachytene 

 Dip = Diplotene 

 Dia = Diakinesis 



Primary 

 spermatocytes 



Barlow, 1953; Eoosen-Runge, jNIarbergcr 

 and Nelson, 1957). 



X. The Interstitial Tissue 



Although miscellaneous general informa- 

 tion is available on the interstitial tissue 

 of many animals, including the gorilla, the 

 short-tailed manis, and the vampire bat 

 (Popoff, 1947), detailed knowledge comes 

 from common laboratory animals, such as 

 the rat, mouse, guinea pig, rabbit, and cat. 

 With the exception of man, however, the life 

 history of the interstitial tissue of the testis 

 is probably known best for the bull 

 (Hooker, 1944, 19481. 



In the 1 -month-old bull, when widely 

 separated, lumenless tubules are present, 

 the intertubular spaces contain only mes- 

 enchymal cells. The number of Leydig cells 

 gradually increases up to 2 years of age; 

 after this time, the Leydig cells become 

 vacuolated and increase in both number and 

 size (Fig. 5.13). From 5 to 15 years of age, 

 loss of vacuolation and decrease in size 

 occiu-. After 15 years of age, degeneration 

 ensues. 



^Metamorphosis of the Leydig cell begins 

 with nuclear changes. The nucleus acquires 

 1 to 3 nucleoli, increases by 25 per cent in 

 volume, and becomes spherical. Hyper- 

 trophy and hyperplasia of the cell occur. 

 The cell still retains its stellate appearance, 

 but becomes polygonal in shape after gran- 

 ules appear in the cytoplasm. After 2 years 

 of age, vacuolation occurs and, with age, 

 the vacuoles become larger. At 5 years of 

 age, vacuolation is present in all Leydig 

 cells. Regression of the Leydig cells be- 

 gins at 7 years of age; it is manifested 

 by a decrease in vacuolation and mitotic 

 activity (Hooker, 1944, 1948), and ends 

 in cellular disintegration (Fig. 5.14). 



In addition to regression, Leydig cells 

 may also dedifferentiate. This occurs in the 

 rabbit. In autografts of testis to the ear, 

 mature Leydig cells show fusion of granules, 

 shrinkage of cytoplasm, loss of nuclear 

 transparency, and finally cannot be dis- 

 tinguished as a Levdig cell (Williams, 

 1950). 



The life history of the Leydig cell in 

 man and monkey is in general similar to 



