Ultrastructure and histochemistry of human SIF cells and paraganglia

The FIF method and electron microscopy were used to study SIF cells in the human sympathetic ganglia. In serial sections SIF cells in one ganglion often numbered less than 30, although they were found in every ganglion examined. Microspectrofluorimetry demonstrated the high catecholamine content in SIF cells. Electron microscopically these cells appeared as small granule-containing cells that receive a rich cholinergic type innervation. The diameter of the storage granules was 300 to 400 nm. In addition the SIF cells had close connections with each other. The SIF cells, situated solitary or as small clusters, were surrounded by satellite cells. Frequently the SIF cells located close to blood vessels.