Electron-microscopic identification of Gomori-positive rings in normal spinal cord white matter.

Longitudinal vibratome slices from glutaraldehyde-fixed adult guinea pig lateral funiculus white matter were incubated in a Gomori medium, stained with ammonium sulfide, osmicated and section-embedded in vestopal. Following light-microscopic localization of ring-shaped deposits of reaction product series of thin sections were cut from these areas. In the electron microscope ring-shaped deposits of reaction product were consistently found to surround lamellated myelinoid bodies within glial cells. By following the series some of these cells could be identified as microglia. Sparse aggregates of reaction product were occasionally seen outside myelinoid bodies in typical astrocytes. Precipitates were not related to myelinoid bodies associated with typical oligodendrocytes. The findings suggest that microglia and possibly astroglia participate in the breakdown of spontaneously formed myelin fragments in normal adult white matter.