Action of testosterone on the estradiol-induced feminization of the male chick embryo.

The early treatment of male chick embryos with estradiol induces the feminization of their sex tract, i.e. both their gonads and müllerian tract exhibit female features.

Action of testosterone on the anti-müllerian activity of the chick embryonic testis assayed in vivo by organotypic grafting.

The implantation of embryonic testis grafts into female chick embryos induces the regression of their müllerian ducts (MDs) in a certain number of cases. The treatment of either the grafts or the grafted females with testosterone propionate (TP) results in a significant increase in the number of MD regressions observed. Our data are interpretable in terms of a direct activation by TP of the anti-müllerian activity of the embryonic testis.

Action of estradiol and tamoxifen on the testis-inducing activity of the chick embryonic testis grafted to the female embryo.

The implantation of two testes from 13-day-old male chick donor embryos into the extra-embryonic celom of 3-day-old female embryos induces the masculinization of their ovaries up to a total and definitive inversion of their gonadal sex, i.e., the differentiation of testes in the female hosts.

Action of estradiol and tamoxifen on the Müllero-regressive activity of the chick embryonic testis assayed in vivo by organotypic grafting.

In the chick, the implantation of a testis graft from a 13-day-old male donor embryo into the extra-embryonic coelom of 3-day-old female embryos induces the total regression of their Müllerian ducts because of the anti-Müllerian hormone (AMH or MIS) secreted by the implant. Pre-treatment of the donors with estradiol (E2), between day 12 and day 13, counteracts in a significant way the Müllero-regressive activity of the implant. Co-treatment of donors at the same stage with both Tamoxifen (TAM) and E2 restores the initially observed activity, thus demonstrating the presence of Tamoxifen-sensitive estrogen receptors at the late stage of treatment in the Sertoli cells responsible for AMH secretion.

[Contribution of experimental intersexuality in chickens to the problem of gonadal differentiation and its abnormalities in amniotic vertebrates].

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.

[Crossed graft of embryonic testis between quail and chick embryos: contribution to the study of the mechanism of female bird embryo masculinization].

Quail, or chick embryonic testes grafted respectively in the extraembryonic coelom of chick or quail embryos induce both a Mullerian duct regression and a masculinization of the female host gonads up to the differentiation of two testes, in some cases. Such a result confirms the fact evidenced previously in other bird species (chick and duck) that the testis-inducer is interspecific. Quail cells are not observed in histological sections of embryonic gonads of testis-grafted chicks.

Influence of heterospecific testis graft on the gonadal sex differentiation of female bird embryos.

Testes from duck and chick embryos grafted, respectively, to chick and duck genetically female host embryos modifies their gonadal differentiation. It results in masculinization developing, in some cases as far as testis formation. This demonstrates 'in vivo' that the testis inductor(s) secreted by the grafted testis is (are) interspecific.

Action of estradiol on müllerian duct regression induced by treatment with norethindrone of female chick embryos.

Treatment of genetically female chick embryos with norethindrone (NET), a progesterone-like steroid chemically related to testosterone, caused two types of Müllerian duct (MD) deficiencies. The first consisted in an absence of the caudal part of the ducts owing to their partial agenesia occurring between Days 5 and 7 of embryonic life. This is nonspecific since it was observed after a treatment with almost all steroidal sex hormones.

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.

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.

Influence of an antiestrogenic drug (tamoxifen) on Müllerian duct agenesia induced by various steroidal sex hormones in the female chick embryo.

The caudal deficiencies of the Müllerian ducts (MDs) induced in chick embryos after early treatment with testosterone propionate (TP), 17 beta-estradiol benzoate (EB), or dihydrotestosterone (DHT) are the consequence of agenesia, i.e., a stop in duct development occurring during the sexually indifferent stage.

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.

Secretion of the anti-müllerian hormone by the gonads of experimentally sex reversed female chick embryos.

The gonads of genetically female chick embryos experimentally transformed into testes under the influence of a embryonic testis graft are able to induce in vivo the regression of Müllerian ducts when they are grafted to female embryonic hosts. On the other hand female gonads only transformed into ovotestes are ineffective on the host MDs, as in the case for female gonads. These results show that totally sex reversed gonads have the same properties as a normal testis.

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.

Experimentally induced true hermaphroditism in genetically female fowl.

Two types of hermaphroditism were experimentally induced in genetically female fowls by grafting of embryonic testes in embryos. Of the 27 hermaphrodites observed during the 8 months after hatching, 20 possessed a right testis and a left ovary and 7 a right testis and a left ovotestis. The testes and ovotestes contained seminiferous tubules with a more or less developed germ cell complement, attaining in many cases the early spermatid stage.

[Decrease in the secretion of anti-Müllerian hormone by the chick testis during development].

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.

[Effects of testosterone and progesterone on the regression of Mullerian ducts induced by estradiol in the female chick embryo].

An administration of testosterone or of progesterone to estradiol-treated female chick embryos increased the rate of those presenting a regression of their Müllerian ducts. This observation favoured the hypothesis according to which the regression induced by estrogens depends on the anti-Müllerian hormone of ovarian origin.

[Synergistic action, on the masculinization of female chick embryo gonads, of a graft of embryonic testis and administration of an anti-estrogenic substance (tamoxifen)].

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.

[Development of an embryonic thyroid grafted into a chick embryo].

A morphological and physiological study of an embryonic thyroid grafted in a chick embryo showed that it developed according to the endocrine status of the host. Its relative age appreciated at various stages of embryonic life is different from that of a gland developing normally during similar lengths of time.

[Hypothalamo-hypophyseal correlates in the chick embryo: thyrotropic activity of adenohypophyseal grafts from donor embryos of various ages. Effect or pretreatment with TRH].

Adenohypophyses from 10 to 18-day-old chick embryonic donors grafted in 3 days chick embryos, thus disconnected from the hypothalamus, had a partially autonomous thyrotrophic activity. However this functional autonomy was greater in grafts from donors aged 10 or 11 days than from older embryos or from 11-day donors pretreated with T.R.

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.

Development of the testes in female domestic fowls submitted to an experimental sex reversal during embryonic life.

The sex differentiation of the female chick embryo can be totally inverted toward the male sex by an early extraembryonic testis grafting. This sex reversal remains permanent, as shown by three adult fowls described in this paper. They possess two testes associated with normally differentiated male excretory ducts and their Müllerian ducts have regressed.

Influence of an early grafted adenohypophysis on the thyroid of the chick embryo.

A hypophyseal pars distalis from an 11-day-old chick embryonic donor was implanted in the extraembryonic coelom of a 3-day-old recipient in order to evaluate the reactions of the thyroid of the host embryo and thus the functional capabilities of the grafted pituitary related to the thyroid. The graft did not modify the general growth of the embryo, but strongly influenced thyroidal development. The volume, colloid content, and radioiodide uptake of the thyroid gland were significantly increased, from Day 10 of incubation, compared with controls, as was the development of cytological structures, studied with the electron microscope.

Action of testis graft from puromycin- or cAMP-pretreated donor embryos on the regression of Müllerian ducts in the female chick embryo.

Female chick embryos grafted with a piece of embryonic testis manifest in a high percentage of cases a regression of their Müllerian ducts (MD) under the influence of a anti-Müllerian hormone (AMH) secreted by the graft. Puromycine or cAMP administered to grafted females reduced significantly the percentage of those presenting a MD regression. In the present work puromycin or cAMP was administered to the male graft-donor embryos and not to the grafted females as was done previously.