[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.

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.