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  • Author: P. G. W. J. Van Oordt x
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P. G. W. J. VAN OORDT and B. LOFTS

SUMMARY

The pars distalis of the pituitary, the testes, thumb pads, seminal vesicles and thyroids were studied in common frogs (Rana temporaria) kept at 20–24° c for 4, 6 and 8 weeks respectively from 11 October. They were compared with those of control animals kept at normal outdoor temperatures during the same periods.

The following effects of high temperatures were noted:

(1) In the distal lobe of the pituitary a regression of the γ-cells and increased secretory activity of the β-cells.

(2) In the testes formation of cholesterol-positive lipids in interstitium and Sertoli cells, disintegration of sperm bundles, and spermatogenesis.

(3) In the thumb pads a regression of the epidermis and in the seminal vesicles a reduction of the epithelium. The thyroids remained unaffected.

Comparing these results with each other and with those of earlier experiments by the same authors, it was concluded that high temperatures diminished the ICSH activity of the pituitary and thus caused a reduction in the production and secretion of male sex hormone, and degenerative changes in the Sertoli cell-sperm bundle system. Moreover, high temperatures were believed to accelerate the FSH activity of the pituitary resulting in the disappearance of old remnants of sperm bundles and Sertoli cells, and subsequent spermatogenesis.

The internal rhythm, regulating the sensitivity of the germinal epithelium to gonadotrophin, was thought to manifest itself by a varying demand for FSH and a seasonal refractoriness of the primary spermatogonia to this hormone. Each of these two factors makes it impossible to transform the discontinuous spermatogenetic cycle of Rana temporaria into a continuous cycle.

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W. G. E. J. Schoonen, J. G. D. Lambert, J. W. Resink, W. J. A. R. Viveen and P. G. W. J. Van Oordt

ABSTRACT

Quantitative aspects of bioconversions in the testes of the African catfish (Clarias gariepinus) were studied in vitro by incubation of tissue with [3H]pregnenolone or [3H]androstenedione. During the breeding period, spawning and non-spawning animals were collected from their natural habitat, the Hula nature reserve, in northern Israel. In the same period, non-spawning animals were collected from a fish pond in the same region. It was shown that spawning was accompanied by significant changes in steroid bioconversions, i.e. a reduction in androgen synthesis, especially of 11β-hydroxyandrostenedione and 11β-hydroxytestosterone and an increase in the production of C21-steroids, especially progesterone, 17α-hydroxyprogesterone and a pregnenolone ester. These changes resulted from a decreased contribution of the cytochrome P-450 enzymes 17α-hydroxylase, C17–20-lyase and 11β-hydroxylase. A rise in plasma gonadotrophin concentration was observed only in spawning catfish. In the absence of such an increase in plasma gonadotrophin, steroid synthesis in the testes of non-spawning feral and pond catfish was primarily directed towards the production of 11-oxygenated androgens and 5β-pregnane-3α,17α,20α-triol. It is suggested that spawning is induced by gonadotrophin and the ensuing change in steroidogenesis. It is possible that husbandry conditions inhibit the necessary increase in gonadotrophin release.

J. Endocr. (1987) 112, 323–332