Conspicuous dilatations and inclusions of the rough endoplasmic reticulum have been observed within the cytoplasm of sheath cells (cells of Schwann) and connective tissue in cat sympathetic ganglia. The sheath cell inclusions have been found regularly in young animals (under 6 weeks of age), and in older specimens following partial preganglionic nerve section. Electron-density of the inclusion material is characteristic for each kind of cell.
Three possible functional roles are suggested for the material observed in the dilated sacs of sheath cells: (a) for manufacture of the basement membrane (b) for participating in the nutrition of nerve processes (c) for providing lipoprotein required for myelination of axons. It is also entirely possible that the cell utilizes this product in a variety of ways. The ER inclusions of connective tissue cells are thought to function in the synthesis of collagen.
Present knowledge does not permit analysis of the mechanisms responsible for controlling this secretory machinery.