[Contribution of experimental intersexuality in chickens to the problem of gonadal differentiation and its abnormalities in amniotic vertebrates]. / Apport de l'intersexualité expérimentale chez le Poulet au problème de la différenciation gonadique et de ses anomalies chez les vertébrés amniotes.

The grafting of embryonic testes to chick embryos realizes an experimental model which is near the spontaneous situation of the cattle "free-martin". It allows to obtain a masculinization of female host embryos developing in some cases up to a total and definitive reversal of sex differentiation. Indeed, it is possible, by this way to obtain testes induced under the influence of substance(s) secreted by the grafts which determine epigenetically a sexual phenotype opposite to the genotype of the host embryos. The analysis of such testis morphogenesis shows that it results from an inhibitory mechanism. Some experimental data strongly suggest to ascribe it to the anti-Mullerian hormone secreted by the graft. The ovotestes and testes observed in adult treated animals present various degrees of development, especially at the level of seminiferous tubules in which the spermatogenesis, when present, may be completed until spermatozoa. Some gonadal abnormalities interesting genetically female human beings, like a majority of the hermaphrodites, or certain XX men, are discussed at the light of these experimental data.

New insights on the mechanism of testis differentiation from the morphogenesis of experimentally induced testes in genetically female chick embryos.

Embryonic testes grafted in the extraembryonic coelom of 3-day-old genetically female chick embryos may induce total and definitive reversal of gonadal sex differentiation. In this experimental condition, the left gonad becomes a testis instead of an ovary. This makes it possible to compare testicular and ovarian morphogenesis in animals having the same genetic sex and to discount what is due to differences in the genetic determination between male and female. The morphogenesis of such testes is marked by a disappearance of the cortical germinal epithelium. The medullary sex cords keep a narrow lumen instead of becoming large lacunae. The germ cells remain few in the sex cords and do not become meiotic. Furthermore, interstitial cell development is known to be very slow. As a consequence the gross size of the gonad is much smaller than that of an ovary. All these morphogenetic phenomena are unlike those observed during normal ovarian differentiation and evidence an inhibiting influence of the grafted testes. Since inhibition and masculinization are concomitant, inhibition appears to be the mechanism responsible for gonadal sex reversal. The extraembryonic situation of the grafted testes and their relation with the embryo only via the blood stream demonstrates the role of a secreted substance or substances still to be exactly identified. Previous data suggest that this could be the anti-Müllerian-hormone (AMH). Furthermore, previous and present results show that testis differentiation can be actively induced in a bird. This does not agree with the hypothesis that the gonads of the homogametic sex, i.e., the testes in birds, do not need any inducer in order to differentiate.(ABSTRACT TRUNCATED AT 250 WORDS)

Structure of the right testis of sexually mature genetically female fowl experimentally masculinized during embryonic life and submitted to a posthatching left castration.

Posthatching left castration of genetically female fowl, Gallus domesticus, preceded, during embryonic life, by a masculinizing treatment associating a testis graft and an antiestrogen resulted in the development of the right rudimentary gonad into a testis. Examined after the sexual maturity, the right testis of most treated animals was entirely composed of seminiferous tubules possessing a spermatogenic cell complement. Spermiogenesis proceeded to the stage of spermatozoon in 4 out of 17 treated animals and was almost as well organized as in a normal cock testis in 3 of them. Testis development appeared then as clearly improved, compared to that described previously in only left-castrated, with or without treatment with an antiestrogen, or only sex-reversed female fowl. The possible mechanism of this improvement is discussed.

Absence of anti-Müllerian activity of inhibin in the chick embryo.

Inhibin extracted from bovine follicular fluid and administered to chick embryos at a dosage increasing from 0.4 to 30 micrograms per embryo did not induce the regression of the Müllerian ducts of treated females. This result contrasts with that obtained with a testis graft which acts through its anti-Müllerian hormone. Although both hormones were of glycoproteic nature and secreted by the same cells, this study shows no functional analogy between them.

Development of interstitial cells in experimentally sex-reversed gonads of genetically female chick embryos.

A testis graft implanted in young genetically female embryos induced a male gonadal differentiation. The interstitial cell percentage and actual content were strongly lowered in masculinized gonads compared to normal female embryos and became similar to those observed in the normal developing embryonic testis. This effect was enhanced by the association of a graft and an antiestrogenic drug, and was not observed after administration of the drug alone. This inhibiting influence of the graft on interstitial cell formation may be considered as resulting in an inhibition of estrogen production. Its possible causative role in gonadal masculinization is discussed in the light of previous and present results.

[Decrease in the secretion of anti-Müllerian hormone by the chick testis during development]. / Sur la décroissance de la sécrétion de l'hormone anti-müllérienne par le testicule du poulet au cours du développement.

At the end of embryonic life the chick embryonic testis possesses a low anti-Müllerian activity, as evidenced by the grafting method to female hosts. The percentage of grafted embryos presenting a Müllerian duct regression is not increased by administration of an anti-estrogenic drug (tamoxifen). This observation does not favour the hypothesis according to which the low percentage of regression could be due to a protection of Müllerian ducts by estrogens from the host ovary. It shows rather that the anti-Müllerian hormone secretion actually decreases during development.

[Synergistic action, on the masculinization of female chick embryo gonads, of a graft of embryonic testis and administration of an anti-estrogenic substance (tamoxifen)]. / Action synergique, sur la masculinisation des gonades de l'embryon femelle de Poulet, d'une greffe de testicule embryonnaire et de l'administration d'une substance anti-oestrogène (tamoxifène).

The capability of an embryonic testis graft to induce a male gonadal sex differentiation in genetically female chick embryos was significantly enhanced by the administration of a antiestrogenic drug (tamoxifen). This observation reinforces the view that the experimentally-induced testis differentiation depends chiefly on a inhibition of estrogen influence.

Role of the thyroid in the involution of the mesonephric Malpighian corpuscles in the chick embryo.

The mesonephros of the chick embryo normally begins to regress during the second half of embryonic life. Experimental methods, such as adenohypophysis grafting, hypophysectomy or use of antithyroid drugs, which stimulate or depress the thyroid function of the embryo, modified accordingly the regressive processes occurring in the mesonephric Malpighian corpuscles, particularly at the level of the glomerular basement laminae. These results as well as the known sensitivity of the mesonephros to thyroxine and the concordance between the steps of embryonic thyroid development and the mesonephric modifications show that the thyroid normally plays a major determining role in this phenomenon.

[Action of the testosterone treated chicken testis on the regression of the Müllerian duct]. / Action du testicule de poulet traité par la testostérone sur la régression des canaxu de Müller.

After administration of testosterone propionate to male chick embryos and chickens, their testis have an activity, on the retrogression of mullerian ducts, much more important than that observed in testis of normal subjects of the same age, activity measured by grafting testis fragments in undifferentiated female chick embryos. The results suggest that testosterone gives such an effect by inhibiting pituitary gonadotropins, peculiarly FSH.

[Influence of an antiandrogen, cyproteron acetate, on the morphogenesis of the epididymis in the chick]. / Influence d'un anti-adrogène, l'acétate de cyprotérone, sur la morphogenèse de l'épididyme du coq

Morphogenesis of the epididymis, which takes place in the chick, during the two months after hatching, is inhibited by the antiandrogenic drug, cyproteron acetate, which acts as strongly as castration. This fact is a good argument for our conception of sexual differentiation after which epididymis is induced by testosterone.