Connections between the various elements of the Cis‐ and mid‐compartments of the Golgi apparatus of early rat spermatids

Abstract

The exact structural relationships of the saccules, membranous tubules, and vesicles that compose the cis- and mid-compartments of the Golgi cortex of rat spermatids was investigated to determine the relationship of these elements to each other. Tissues fixed with glutaraldehyde and buffered in sodium cacodylate were examined with the electron microscope. Electron micrographs, including stereopairs, were analyzed to determine the three-dimensional organization of the Golgi elements. The deeper layer of the Golgi cortex was composed of stacks of saccules connected to each other either by saccules or membranous tubules. The peripheral region of the Golgi cortex, located between the cis-side of the stacks and a network of overlying ER cisternae contained numerous membranous tubules and vesicles of two class sizes: 50-100 nm vesicles and microvesicles 5-10 nm in diameter. The tubules formed tight networks, known as cis-elements or cis-Golgi networks (CGN), which were strictly parallel and next to the first or cis-saccule of the stack. The cis-elements were continuous with more loosely arranged peripheral tubules which formed elaborate, intertwined and interconnected networks. These peripheral tubules closely approximated the overlying ER cisternae in areas often showing fuzz-coated finger-like projections. Occasionally such peripheral tubules were continuous with ER cisternae. The saccules forming the stacks were continuous with membranous tubules which not only connected saccules of adjacent stacks, but also saccules of the same stack. These tubules were also connected with the tight tubular networks forming the cis-elements and the broad networks formed by the peripheral membranous tubules. Vesicles (50-100 nm) and microvesicles (5-10 nm) frequently formed aggregates in the peripheral Golgi region next to areas of ER membrane free of fuzz-coated projections. The microvesicles, embedded in a denser cytoplasmic matrix, had a more or less distinct delimiting membrane suggestive of their disintegration in this juxta-ER location. The 50-100 nm vesicles that were seen at the periphery of the vesicular aggregates appeared to form mainly from the membranous tubules of the Golgi cortex. Thus the saccules and membranous tubules of the spermatid's Golgi cortex formed a single continuous membraneous system connected to ER cisternae. The vesicles, seemingly arising from the membranous tubules, appear to follow a retrograde pathway and undergo dissolution next to ER cisternae.