[Epithelial differentiation of rudimentary gonads of human embryos]

Changes in coelomic epihtelium of the germinal gonads in human embryos at the age of 28-35 days of intrauterine development were studied after fixation in Carnoy's fluid, in Shabadash's fluid, in 12% neutral formalin. Paraffin sections were stained with hematoxylin, with ferric hematoxylin after Heidenhain. Fibrils of the basal membrane were detected by silver impregnation after Karupu. PAS-reaction after McManus with additional staining by hamatoxylin and light green and the reaction with bromfenol blue after Michel-Kalvoux to reveal total proteins were applied. Since gonad formation, its coelomic epithelium resembles false pseudostratified one: the nuclei are arranged at different levels, with apical position of mitoses. The cells of the "germinal" epithelium secrete protein-polysaccharide products. The process reaches its maximum by 31-33 day of embryogenesis and coincides with the appearance of the gonads of primary sex cells in the epithelium. This secretion is probably connected with production of an "attractive factor" for gonocytes. On apical surfaces of the epithelium of the gonads, silver impregnation, PAS-reaction and reaction for total proteins reveal an edge which is probably represented by microvilli. The basal membrane of the coelomic epithelium of the gonads loses its integrity when migrating gonads penetrate into the "germinal" epithelium. Later, the integrity of the basal membrane structure is restorted. All these make it possible to consider the epithelium of the embryonal gonads as a specific, different from the other coelomic epithelium layer.