The pituitary-gonad relationship in Xenopus laevis

Abstract

The suitability of Tricaine methane sulphonate, urethane and ether as anaesthetics for Xenopus laevis was investigated. Tricaine was found to be the best of these anaesthetics and a suitable dose /body weight relationship was established.Frequency of feeding was shown to have no effect on spermiation and the secondary sex characters of male Xenopus over a period of months.The proximity of other animals of the same or a different species was shown to inhibit spermiation and the secondary sex characters of male X. laevis. The evidence suggests this effect is due to inhibition of adenohypophyseal gonadotrophin secretion.Nuptial pads (gloving) in male Xenopus was shown to Ìbe controlled by testicular and adrenocortical hormones which are secreted under adenohypophyseal stimulation.Evidence was obtained which suggests that there are two pituitary gonadotrophins in Xenopus; one which stimulates gametogenesis and the other which stimulates the secretion of a gonadal steroid.A inhibiting effect of the gonads on the secretion of adenohypophyseal gonadotrophin has been found.A well controlled technique for investigating invitro ovulation of excised Xenopus ovaries has been developed. Ovaries have been shown to ovulate in-vitro in response to a number of steroids as well as to luteinizing gonadotrophins and adrenocorticotrophic hormone (A.C.T.H.). This is the first report of in-vitro ovulation of excised Amphibian ovaries in response to oestrogens. It is postulated that ovulation in Xenopus is caused by an ovarian steroid secreted as a result of gonadotrophic stimulation.In-vivo ovulation has been shown to result from injection of adrenocorticosteroids, methyl testosterone and projesterone but not in response to injected oestradiol or A.C.T.H. Hydrocortisone has been found to inhibit the ovulatory response of female X. laevis to a subsequent injection of human chorionic gonadotrophin (H.C.G.).Cloacal hyperaemia in female Xenopus has been shown to be controlled by an ovarian hormone secreted in response to stimulation by an adenohypophyseal hormone. Ovulation is only stimulated by a gonadotrophin with luteinizing properties but a gonadotrophin with follicle - stimulating activity is more potent in stimulating cloacal hyperaemia.Gloving, which is essentially a male secondary sex character, was found to be present in some female X. laevis. This gloving is not under the control of the ovaries. Evidence is provided which suggests that it is developed under adrenocortical stimulation.