Materials and methods. Electron microscopy of BMstructure of the seminiferous tubules of 31 patients with azoospermia or severe oligospermia and normal male karyotype (46, XY) without microdeletions of the Y chromosome or structural changes in chromosomes was performed. The group 1 included 18 patients with preserved spermatogenesis including germinal cell differentiation into mature spermatids; the group 2 consisted of13 patients with either Sertoli cells and spermatogonia or only Sertoli cells.

Results. Six main types of ultrastructural changes in BM were observed. The most prominent were BM invaginations in the form of basket weaves that were observed in 8 of 13patients in the group 2. In the group 1, individual basket weaves were observed in 2 of 18patients. Im-munocytochemical examination of I order spermatocyte spread nuclei in 14 patients was performed. In patients of the group 2, spermatocytes weren’t discovered. In 10 patients of the group 1, meiosis arrest at the zygotene and pachytene stages was observed in 18—50 % of spermatocytes. In 6patients, 30 to 50 % of spermatocytes with impaired formation of the structure of the sex body were revealed.

Conclusion. The morphological changes of the BM of the seminiferous tubules (“basket weaves” and duplications of the BM) are associated with marked disorders of meiosis and spermatogenesis. It is suggested about the possibility of mutations of the genes encoding the proteins of BM.