Sex Differentiation of Avian Gonads In Vitro

The analysis of avian sex differentiation in vitro has beenlimited to the following problems: morphological sex differentiationof gonads cultured in vitro; analysis of the chemical natureof the hormonal secretion; differentiation of germ cells inrelation to their somatic environment. Morphological sex differentiationof avian gonads occurs in vitro. Differentiated gonads of thechick embryo carry out biosynthesis of sex hormones from severalradioactive precursors. Female gonads in particular synthesizeestrogens while male gonads synthesize testosterone. Some experimentshave given evidence of estrogen synthesis by undifferentiatedfemale gonads. Embryonic gonads of quail, like those of chick,are able to synthesize sex steroids from radioactive precursors.However, in the quail and mainly in the testes, a delayed appearanceand a lower activity of the enzyme system 3ß-HSDHs-4-isomerase was found. Histoenzymological results corroboratethe biochemical ones. Combination of culture and grafting experimentshave shown that male germ cells when they are forced into femaledifferentiation by early colonization of a female gonad degenerateafter entering the premeiotic stage. The reasons for this delayedfailure of sex differentiation of "male oocytes" have certainlyto be searched for at the level of perturbation in the mechanismsof meiosis.