[Secretory activity of the coelomic epithelium of human embryonal gonads as a factor attracting migrating gonocytes]

Gonades were studied in 10 human embryos at the age of 28 days up to 6 weeks of gestation. The material was immediately fixed in 3% glutaraldehyde, and then in 2% osmium tetraoxide; after dehydration in alcohols it was embedded in araldit. Histological sections were contrasted in saturated alcohol solution of uranilacetate and in lead citrate. The material was studied with an electron microscope Tesla 613. Coelomic epithelium of the gonade, at the beginning of its formation excretes a peculiar secretion into the coelomic cavity. Secretory protrusions possess a large amount of vesicles and canals identical in their structure to elements of the smooth cytoplasmic reticulum. Mature secretion consists only of compact and concentrated canals and vesicles surrounded with a plasmic membrane. The mechanism of excretion is rather of apocrine type. With increasing size of the gonade, at the expense of proliferation of coelomic epithelium, secretion is excreted predominantly into intercellular intervals and gaps. Gonadocytes, appearing in the gonade at that time, demonstrate their affinity to the secretion product capturing it after the phagocytosis type. Secretion of the gonade epithelial cells continues even after gonocytes complete their migration. The type of secretion described seems to play a definite role in attracting primary germ cells of the human embryo, nevertheless, it does not exclude other excretory mechanisms for the "attractive factor" excretion.