Postnatal differentiation of the gametogenic and endocrine functions of the testis in the tree-shrew ( XXXX ).

@entity13190 @entity251 @entity3800
Testicular development was studied in @entity13190 (tree-shrew) from birth to sexual maturity. At birth the seminiferous cords contained peripheral supporting cells and centrally located gonocytes. Large foetal Leydig cells were prominent in the interstitium. The mitotic index of the gonocytes was low at birth and rose to peak levels at Day 20, following the regression of the foetal generation of Leydig cells, and during the nadir in circulating @entity251 concentrations. Mitotic activity returned to low levels at Day 30 in association with the reappearance of differentiated Leydig cells and the first signs of increased androgenesis. The negative temporal relationship between mitogenesis and androgenic function suggests that the proliferation of the gonocytes does not require, and may be inhibited by, high titres of @entity3800 . Post-mitotic development of the gonocytes occurred during a period of rising @entity251 levels, and the first appearance of spermatogonia coincided with peak @entity251 levels. This indicates that @entity3800 may be specifically involved in the initiation of spermatogenesis. Spermatogenesis progressed to completion during a phase of declining @entity251 levels. The precise temporal correlations established during post-natal development suggest that the tree-shrew is a suitable animal model for studies on the endocrine control of the initiation of spermatogenesis in primates.
