EFFECTS OF A SINGLE BRIEF PERIOD OF MODERATE HEATING OF THE TESTES ONSEMINIFEROUS TUBULES IN HYPOPHYSECTOMIZED RAMS TREATED WITH PITUITARYEXTRACT

An experiment was conducted to examine the appearance of the seminifer ous tubule 20 days after a single exposure of the testes of rams to a scrotal temperature of about 42-degrees-C for 45 min. Ten of the anima ls were surgically hypophysectomized and five were simultaneously heat ed; these rams were treated twice a day with ovine pituitary extract t o avoid modifications in the negative feedback from the testes to the pituitary and consequent changes in gonadotrophin secretion. Six intac t rams (three heated and three unheated) were also studied. The pituit ary extract significantly increased the testis weight and spermatogoni al multiplications from A1 spermatogonia onwards. Twenty days after th e heat treatment, testis weight was significantly reduced by heating; both tubular and intertubular tissues were affected. The total length of seminiferous tubules per testis was not modified, whereas the mean seminiferous tubule diameter was significantly reduced after heating. The total number of Sertoli cells per testis was not significantly mod ified, while their mean cross-sectional nuclear area was significantly reduced by heat treatment. A decrease in the number of all germ cells except A0 spermatogonia, from A1 spermatogonia onwards, was observed. The number of round spermatids decreased by 95 and 90%, slightly more than the diplotene primary spermatocytes (76 and 77%) and elongated s permatids (79 and 85%) in hypophysectomized pituitary extract-treated and intact rams, respectively. Round and elongated spermatids would be derived from germ cells that were respectively leptotene and young pa chytene primary spermatocytes at the time of heating, whereas diploten e primary spermatocytes would have been type B spermatogonia. Normal s permiation did not take place and some testicular spermatozoa remained loosely attached to the seminiferous epithelium. It is concluded that this mild heat treatment caused considerable disruption to the sperma togenic cells, but the effect was comparable in intact rams, in which pituitary gonadotrophin secretion may have changed and in hypophysecto mized rams treated with a constant dose of pituitary extract.