Small, intensely fluorescent cells of human sympathetic ganglia.

Human sympathetic ganglia obtained from sympathectomies were studied using the formaldehyde-induced fluorescence (FIF) method and electron microscopy to identify the small, intensely fluorescent (Sif) cells. Microspectrofluorimetry was used to study the intensity of the emitted FIF and the emission spectra. The SIF cells were found in every ganglion studied, but they were very sparce. They occurred alone or in small clusters and were mostly situated close to the blood vessels. The SIF cells contained high amounts of catecholamines, as indicated by microspectrofluorimetry. Electron microscopy revealed granule-containing cells (GC) enveloped by satellite cells; the former cells contained osmiophilic granules 300--400 nm in diameter and synapses of the cholinergic type were frequently found on their surface.