Three-dimensional organization of the Golgi complex observed by scanning electron microscopy.

With the development of new specimen preparation techniques and improvements in instrumental resolution, scanning electron microscopy (SEM) became an effective means of studying the three-dimensional organization of the Golgi complex. When specimens prepared by the osmium-DMSO-osmium method are observed with high-resolution SEMs, cis-most cisternae of Golgi stacks appear as sieve-like plates with many small perforations. In some cell types, larger fenestrations are also present. The trans-most cisternae showed a fenestrated or retucular pattern. At the trans-side of Golgi stacks, distinctive structures, such as a well-developed tubular plexus or a single widely extended cisterna, are observed in some types of cells. In lacrimal gland cells, Golgi stacks are linked by an irregular network of anastomosing branches extending throughout the cytoplasm. In these cells, the piled cisternae seemed to be connected to each other either directly within the stack or via cisternae of other stacks. Connections between Golgi stack and rough endoplasmic reticulum (ER) were often found in our SEM observations. In nerve cells, interconnecting tubules arise from the rough ER and most often fuse with the rim of the cis-cisternae of Golgi stacks.