G. Chieffi

The effects of antiandrogens and antiestrogens in nonmammalian vertebrates

A number of compounds with antiandrogenic and antiestrogenic activity have been tested on representative species of fish, amphibians, reptiles, and birds. The results obtained so far show that cyproterone acetate (CPA) and ICI 46474 behave in a manner similar to that reported from mammalian studies. This applies particularly to their ability to inhibit testosterone- and estradiol-sensitive target tissues. It has also been shown in the frog that CPA competes specifically for the androgen receptor molecules in the thumb pads, but does not interfere with testosterone secretion. CPA did not, however, inhibit the masculinizing effects of testosterone propionate or of 11-ketotestosterone in the teleost Xiphophorus helleri. Earlier reports had found CPA to be effective in causing regression of the seminal vesicles in the catfish. n nIn a frog oviduct test some steroids, like 6-chloro-17α-hydroxy-pregna-4,6-diene-3,20-dione, 2α,17α-dimethyl-dihydrotestosterone, and 2α-methyl-dihydrotestosterone, manifest antiestrogenic effects. ICI 46474 is estrogenic in high doses but antiestrogenic in low amounts. As far as the mechanism of action of these compounds is concerned it is only possible to claim for CPA that it competes against the steroid for the receptor sites on the target organ. n nFinally the challenging problem of the nature of embryonic sex inductors in frog tadpoles has been approached through the use of such antihormones. The mesculinizing effects of CPA on one hand and lack of any effect of ICI 46474 on the other strongly suggest that embryonic sex inductors are different from gonadal steroids.

Cytological changes in the pars distalis of pituitary of the green frog, Rana esculenta L., during the reproductive cycle.

SummaryThe cytological changes in the pars distalis of pituitary of male and female green frog, Rana esculenta during the reproductive cycle have been studied by examining the form, cytoplasmic granulation and numerical proportions of the different cell types. Some sex differences were recorded, particularly in relative total number of cells in a median sagittal section of the pars distalis. No extensive cytological changes occur during the hibernation period, but there are striking alterations at the time of spring awakening, during spawning months and during replenishment of the spent gonads i.e. during late summer and autumn months. Important changes are to be observed in the acidophils type one (A1) and basophils type two (B2) and three (B3). Changes in the A1 cells during breeding season have been speculated as being in support of the spawning activity of the animal. The B2 cells exhibit most profound changes which correlate precisely with the morphological changes in gonads, and these cells are considered as the FSH-gonadotrops. The functional significance of the B3 cells is discussed and it is suggested that they might be the source of an ICSH- or LH-like hormone.

Effects of intratesticular injections of estradiol and gonadotropin-releasing hormone (GnRHA, HOE 766) on plasma androgen levels in intact and hypophysectomized Torpedo marmorata and Torpedo ocellata

The effect of a gonadotropin-releasing hormone analog (GnRHA, HOE766) was studied in hypophysectomized elasmobranch fish Torpedo marmorata and T. ocellata. In addition, estradiol (E2) effects were studied in intact and hypophysectomized (HPX) animals. Plasma androgen concentrations were measured 2 or 6 hr after GnRHA (100 ng or 10 micrograms) or 6 hr after E2 (10(-9) or 10(-6) M) intratesticular injections. Both GnRHA and E2 induced the increase of plasma androgen levels in HPX fish. E2 also enhanced androgen levels in intact animals. It is concluded that GnRH-like substances and E2 may modulate testicular activity in elasmobranch fish.

The function of fat bodies in relation to the hypothalamo-hypophyseal-gonadal axis in the frog, Rana esculenta.

SummaryIn this study the authors have tried to furnish experimental support for the importance of fat bodies in the normal functioning of the hypothalamo-hypophyseal-gonadal system of the male frog, Rana esculenta. These experiments have shown a hypothalamohypophyseal control of the mobilization of fat body contents, directly involved in the control of testicular activity. Furthermore it is proposed that the fat body contents are released into the testis through direct vascular contacts between the two organs. We suggest that the A1 cells (lactotrophs) and/or B2 cells (FSH-gonadotrops) of the pars distalis contain a factor responsible for the mobilization of fat body contents, and that the pars distalis gonadotropins are incapable of stimulating the testis in the absence of fat bodies. In the light of these results a scheme has been put forward showing the position of fat bodies in the hypothalamohypophyseal-gonadal axis of the frog.

A cytological study of the pars distalis of pituitary gland of normal, gonadectomized, and gonadectomized steroid hormone-treated green frog, Rana esculenta L

The cytology of the pars distalis of pituitary green frog, Rana esculenta, was studied using various staining techniques. In general, besides the irregular occurrence of chromophobes, five chromophilic cell types were readily distinguishable (acidophils types 1 and 2, and basophils types 1, 2, and 3). The distribution of various cell types in the pars distalis has been described. The cytological modifications in the pars distalis of the male and female green frogs, gonadectomized during different periods of the sexual cycle, were studied at short and long intervals after gonadectomy. Administration of different doses of testosterone propionate and estradiol benzoate in the long-term castrates has been found effective in restoring the postgonadectomy changes. Similar treatment in the recently gonadectomized frogs prevented the occurrence of postgonadectomy changes. In general the basophils type 2 (B 2) exhibited the most profound modifications following gonadectomy and steroid hormone administration in both the male and female green frogs. The functional significance of the B 2 cells is discussed. It is suggested that these cells are the source of gonadotropic hormone(s) in this species.

Effect of cyproterone, cyproterone acetate and ICI 46,474 on gonadal sex differentiation in Rana esculenta ☆

Abstract The action of estradiol-17β, ICI 46,474 (antiestrogen), testosterone, and cyproterone and cyproterone acetate (antiandrogens) on gonadal sex differentiation was studied in the tadpoles of Rana esculenta . Testosterone masculinizes the embryonic gonads, and so also do the antiandrogens. Estradiol-17β feminizes the tadpole gonads, but the antiestrogen has no definite effect, either feminizing or masculinizing. However, these antihormones compete with the sex hormones at the target sites in the adult frog. It is apparent from these results, as also from the data available elsewhere, that embryonic sex inductors are not similar to sex hormones.

Effects of Methallibure (ICI 33,828) on the pars distalis of pituitary, testis and thumb pad of the green frog, Rana esculenta L.

SummaryThe influence of ICI compound 33,828 (1-α-methylallylthiocarbamoyl-2-methylthiocarbamoylhydrazine = Methallibure) on the pars distalis of pituitary, testes and thumb pads was investigated in the intact adult male green frog, Rana esculenta. Methallibure affected the gonadotropic basophils (particularly the B2 cells) of the pars distalis, which showed varying degrees of degranulation and underwent a notable decrease in their percentage. Within the testis this compound caused the arrest of spermatogenesis. The most uniform effect of Methallibure was observed in the thumb pads, which invariably showed regression of the epidermis and glandular epithelium. No histological changes occurred in the thyroid and adrenal glands and the B1 and A1 cells of the pars distalis remained unchanged cytologically. It is concluded, in concordance with the available data, that Methallibure is a non-steroidal antigonadotropic compound. The important question about its mode of action has been brought into discussion.

In vitro steroidogenesis in the testicular tissue of the fresh water teleost Esox lucius

Abstract Some important steps of steroidogenesis have been studied during the breeding season in the testicular tissue of Esox lucius using histochemical and biochemical techniques. Incubations of acetone powder from testicular tissue with several substrates yielded the following metabolites: pregnenolone was converted to dehydroepiandrosterone and progesterone, dehydroepiandrosterone was converted to androstenediol and testosterone, androstenediol was converted to testosterone and dehydroepiandrosterone, and androstenedione was only slightly converted to testosterone. These steroids were identified and quantified through gas-liquid chromatography before and after derivative formation. These findings support the view that androstenediol is an important intermediate in the biosynthesis of testosterone in the testis of Esox lucius. Histochemical reactions for 3β- and 17β-hydroxysteroid dehydrogenases with all the substrates used and for cholesterol were negative for both seminiferous lobules and “lobule boundary cells.”

Inhibition of pituitary gonadotropic effects in the pars distalis-ectomized Rana esculenta by methallibure (ICI 33,828)

SummaryEffects of Methallibure on the gonadotropic stimulation of the regressed gonads and secondary sex characters of the pars distalis-ectomized adult green frog, Rana esculenta, were studied. Regression of the gametogenetic activity and reduction of oviducts and thumb pads are the eventual consequences of the removal of pars distalis. Homoplastic pars distalis homogenates restimulate the gametogenesis and regressed secondary sex characters due to their gonadotropic hormone contents. Methallibure in this case blocks the stimulation of these organs by homoplastic pars distalis, which indicates that this compound inhibits the action of gonadotropic hormones upon their target tissues.

Changes in the cytology of the pars distalis of pituitary of green frog, Rana esculenta, under laboratory confinement

The cytological changes in the pars distalis of female and male green frogs, Rana esculenta, were studied following varying periods of confinement in open air vivaria and inside the laboratory with the temperature regulated at 18–20°. In general, after long confinement up to a period of nearly 1 year, the basophils type two (B2) showed partial degranulation, total loss of their orangeophilic granules, reduction in size, and an insignificant decrease in their percentage. The acidophils and chromophobes also showed no significant changes in their percentage. The effect of confinement upon pituitary cytology was thus more morphological than “numerical.” The results have been discussed in the light of our earlier observations on this gland under different experimental conditions.