Reacting ultrastructure of the human oligodendrocyte (a study of cerebral cortex distant to brain tumours).

Electron microscopical examination of adjacent human cerebral cortex from patients with brain tumour revealed the following morphological distinctive features of the oligodendrocyte: the presence of a diffuse electron dense material, large quantities of free ribosomes or ribosomal rosettes, eccentric nucleus with irregular clumps of chromatin, swollen perinuclear cisterna, extensive cytoplasmic microtubules, well-developed Golgi apparatus opposite the eccentric nuclei, dilated endoplasmic reticulum and mitochondria. The majority of oligodendrocytes contain large indefinable heterogeneous electron-dense structures within their perikaryon or processes. Oligodendrocytes with similar inclusion bodies are seen in the vicinity of capillaries. For these reasons a possible phagocytic activity of the human oligodendrocyte seems likely.