Mechanism for the Formation of Seminiferous Tubules in Mammals

用光镜和透射电子显微镜观察发育过程中小鼠生精上皮，以阐明支持细胞的起源。在胎鼠第12天至第14天的睾丸中，PAS阳性物质仅见于C57BL/6小鼠Sertoli细胞的胞浆。出生后第12天，支持前细胞在生殖细胞周围形成不规则的索状排列，这种排列与体腔上皮无关。提示支持细胞起源于中肾组织。接下来，我们检测了发育中的小鼠胚胎睾丸凝集素结合的变化，以阐明生精小管形成的机制。在睾丸发育的3种凝集素中，BS-I和BPA在12~14天优先结合在生殖细胞的质膜和小致密小体上。但在16天的胎儿睾丸中，这两种凝集素的反应完全消失。与GS-II的反应仅限于12~14天的支持细胞，16天后消失。凝集素结合模式的显著变化表明，某些含有D-半乳糖和N-乙酰-D-半乳糖胺残基的糖偶联物在12~14DPC期间表达，功能和结构的变化可能发生在14~16DPC期间，与睾丸发育有关。

The seminiferous epithelium in the developing mice was studied by light and transmission electron microscopy to elucidate the origin of Sertoli cells. In the testis of fetal mice from day 12 to day 14 pc, PAS-positive substances were detected exclusively throughout the cytoplasm of Sertoli cells in C57BL/6 mice. On day 12 pc, pre-Sertoli cells formed irregular and cord-like arrangements around germ cells, and the arrangements were not associated with the coelomic epithelium. This suggests that Sertoli cells are originated from the mesonephric tissues. Next, the changes in lectin binding of developing fetal mouse testis were examined to clarify the mechanism of seminiferous tubule formation. out of three lectins, which, showed the characteristic binding pattern during the testicular development, BS-I and BPA preferentially bound to the plasma membrane and small dense bodies of germ cells during 12 to 14 day pc. However, in the fetal testis on day 16 pc, the reaction with these two lectins completely disappeared. The reaction with GS-II was restricted to Sertoli cells from 12 to 14 day pc, and thereafter disappeared on day 16 day pc. The striking changes in lectin binding pattern suggest that certain glyco-conjugates containing D-galactose and N-acetyl-D-galactosamine residues are expressed during the period of 12 to 14 dpc, and the changes in function and structure may take place during 14 to 16 dpc, in association with testicular development.