Three-dimensional architecture of the cortical region of the Golgi apparatus in rat spermatids

Abstract

Glutaraldehyde-fixed testes were impregnated with the Ur-Pb-Cu technique of Thiéry and Rambourg ('76) or postfixed in ferrocyanide-reduced osmium (Karnovsky, '71). Thin and thick (0.5 micron) sections were examined with a Philips 400 electron microscope at 80 or 100 kv. Stereopairs were prepared from pictures of the same field after tilting the specimen every 6 degrees from the -45 degree to the +45 degree position of EM goniometric stage. The cortex of the compact hemispherical Golgi apparatus of young spermatids (steps 2-8) was found to be composed of saccular and intersaccular regions similar to those described in the Golgi apparatus of Sertoli cells (Rambourg et al., '79). In the saccular region, the stacks were composed of three to nine parallel saccules perforated with pores of various dimensions. On the mature or trans-face of the stack, one or two membranous elements with a wider lumen were either closely applied to the overlying saccules or were separated from them and intermixed with the vesicular components of the medulla. On the forming or cis-face of the stack, three or four saccules were frequently interrupted by gaps in register from one saccule to another. In three dimensions, these gaps appeared as pan-shaped spaces or "wells," often containing a few vesicles. Immediately overlying the first saccule on the cis-face, a regular network of anastomotic tubules was present, corresponding to the cis-osmiophilic element observed in other cell types. In the intersaccular region, membranous tubules connected to the edges of the saccules branched, intertwined, anastomosed, and bridged adjacent stacks of saccules. Such membranous tubules bridged saccules with the cis-osmiophilic element or saccules of the same stack. Between the ER cisternae capping the surface of the Golgi apparatus and the cis-network of anastomotic tubules, there was a space called the peripheral Golgi region containing small vesicles and membranous tortuous tubules. The vesicles were frequently arranged in clusters that were capped by an ER cisterna and displayed a size gradient from the periphery to the center of the cluster. Thus, although there were similarities between the three-dimensional architectures of the Golgi apparatus in Sertoli cells and young spermatids (e.g., saccular and intersaccular regions), several structural features distinguished the spermatid's Golgi apparatus.