Ultrastructural characterization of the manchette microtubules in the seminiferous epithelium of the mouse

Abstract

Abstract In the mouse seminiferous epithelium four sites of formed microtubules (MTS) are axonemes and manchettes of spermatids, Sertoli‐cell cytoplasm, and spindles of dividing cells. Various experimental treatments indicate that the manchette MTS are different from other formed MTS. Fixation in 1% osmium tetroxide yields good preservation of axonemal MTS, varying degrees of preservation of manchette MTS, but no preservation of spindle or Sertoli‐cell MTS. Cell‐suspension, and intact‐tubule cultures subjected to 0–4°C or 50°C exhibit a breakdown of spindle and Sertoli‐cell MTS while manchette and axonemal MTS remain intact. Cell suspensions exposed to Colcemid or colchicine show no MTS in Sertoli and dividing cells; axonemal MTS are unaffected while in the manchette there is an increase in cross‐bridging between MTS. Cell suspensions treated for 120 minutes with vinblastine sulfate do not show MTS in the Sertoli cells, but crystals presumed to be microtubule protein are present after 15 minutes of exposure. Spindle MTS are dismantled but vinblastine‐induced crystals are not present even after 120 minutes of exposure. The manchette MTS are dismantled by vinblastine in a proximal direction from their distal limits. This is accompanied by the formation of crystals of microtubule protein in the spermatid cytoplasm, while axonemal MTS are unaffected. Vinblastine and Colcemid used in combination cause the disruption of Sertoli‐cell MTS after 15 minutes, spindle MTS after 30 minutes and formation of crystals after 60 minutes of exposure. The manchette MTS are disassembled, the pattern is disrupted and increased numbers of cross‐bridges are seen. These findings indicate that the manchette MTS might be intermediate‐type microtubules since they exhibit the reactions of both cytoplasmic and flagellar‐type MTS.