Oligodendrocytes

In standard preparations, oligodendrocytes are recognized by their small, round, dark nuclei, rich in chromatin. The small perikaryons, with few and short processes, are visualized using silver stains. In the gray matter, oligodendrocytes serve as satellite cells around the neurons and regulate the perineuronal environment. In the white matter, oligodendrocytes are aligned along the myelin sheaths as interfascicular glia (Fig. 2.7). The major function of interfascicular oligodendrocytes is the formation of myelin during brain development and its maintenance thereafter. The myelin-oligodendrocyte entity plays an important role in autoimmune-mediated myelin diseases and in some viral diseases. Reactions of oligodendrocytes to injury are few.

Pathology

The pathology of oligodendrocytes is summarized in Table 2.5.

Swelling occurs in a variety of diseases, and it appears in HE-stained section as a clear halo of cytoplasm around the nucleus.

Satellitosis, an increase in number of satellite cells, indicates neuronal injury.

Cytoplasmic argyrophilic inclusions are markers of several neurodegenerative diseases. Cap-, flame-, or sickle-shaped inclusions are the histologic hallmarks of

FIGURE 2.7

Oligodendrocytes. A. Satellite oligodendrocytes around cortical neurons (HE). B. Interfascicular oligodendrocytes along myelin sheaths (LFB-CV). Oligodendrocytes showing (C) argyrophilic cytoplasmic inclusions in multiple system atrophy (Gallyas stain).

FIGURE 2.7

Oligodendrocytes. A. Satellite oligodendrocytes around cortical neurons (HE). B. Interfascicular oligodendrocytes along myelin sheaths (LFB-CV). Oligodendrocytes showing (C) argyrophilic cytoplasmic inclusions in multiple system atrophy (Gallyas stain).

multiple system atrophy (see Fig. 2.7). These inclusions are distinguished by positive immunostaining for ubiquitin, a-synuclein and a~P crystalline. Argyro-philic coiled bodies occur in progressive supranuclear palsy, corticobasal dementia, and argyrophilic grain dementia.

Viral nuclear inclusions in large, monster-like oli-godendrocytes are characteristic of progressive multi-focal leukoencephalopathy. They contain virions of JC virus of the papova virus group.

Neoplastic transformation. Oligodendrocytes commonly proliferate into slowly growing neoplasms.

FIGURE 2.8

Ependymal glia. Cuboidal epithelial cells cover the ventricular surface and small nodules of proliferated astrocytes project into the ventricular lumen (granular ependymitis) (HE).

FIGURE 2.8

Ependymal glia. Cuboidal epithelial cells cover the ventricular surface and small nodules of proliferated astrocytes project into the ventricular lumen (granular ependymitis) (HE).

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