Electron microscopic identification of three classes of oligodendrocytes and a preliminary study of their proliferative activity in the corpus callosum of young rats

Abstract

In recent electron microscope studies of the corpus callosum i n 60-80 gm male rats, some of the cells were identified as rnicroglia by staining with thc weak silver carbonate method of del Rio-Hortega, and others as astrocytes by staining with the gold chloride sublimate method of Kamcin y Cajal. In the present work, the cells which did not belong i n one of these two groups were examined i n the light microscope using semithin sections stained with toluidine blue and in the electron microscope using thin sections stained with uranyl-lead.These cells make up a largc, somewhat heterogeneous group, but they have a few common features: regular nucleus, cytoplasm rich in ribosomes and microtubules, and a variahle number of narrow, non-branching fine processes of uniform diameter. Because of these features, the cells are all taken to be oligodendrocytes. Three classes may be described within this group of cells: ( a ) light oligodendrocytes, which are large cclls with pale nucleus, a large nucleolus, a cytoplasm containing rather small organelles as well as many free ribosomes, and giving off nunierous fine processes; they make up about 6% of the glial cells in the corpus callosum; and they undergo mitosis at a rapid ratc; ( b ) mediumahade oligodendrocytes, which are somewhat smaller cells with moderately dense nucleus and cytoplasm, containing well developed organelles, and giving ofl' a fair number of fine processes; they make up about a quarter of the glial cells; and they undergo mitosis at a moderate rate; ( c ) dark oligodendrocytes, which are even smaller cells with very dense nucleus and cytoplasm, containing a prominent Golgi and structures referred to as lamellar bodies, and giving OR' very few fine processes; these cells make up about 40% of the glial cells; they do not undergo mitosis and probably arise from divisions of medium oligodendrocytes.

Immunohistochemical localization of Ih channel subunits, HCN1–4, in the rat brain

“…35). HCN2-immunopositive cells close to neurons had some clumps of heterochromatin along nuclear membrane and their nuclei were eccentrically located in soma, having similar morphological properties to those of previously described perineuronal oligodendrocytes (Mori and Leblond, 1970;Miyake and Kitamura, 1992).…”

Microtubule Organization and Stability in the Oligodendrocyte

“…The presence of centrioles and microtubules in oligodendrocytes in vivo and in vitro has been described by many authors (Mori and Leblond, 1970;Gonatas et al, 1982;Kachar et al, 1986;Kuhlmann-Krieg et al, 1988;Peters et al, 1991), although there are no descriptions of an association between these organelles. In the present EM study, the vast majority of microtubules present in oligodendrocytes had no association with any structures with the appearance of microtubule-organizing centers.…”

Differential effects of cysteamine on heat shock protein induction and cytoplasmic granulation in astrocytes and glioma cells

“…Ultrastructurally, oligodendrocytes are characterized by a cytoplasm which varies in electron density from pale to very dense, is rich in ribosomes and microtubules, contains no filaments, and has weIl developed cistcrnac of rough endoplasmic reticulum (rER; Mori and LeBlond, 1970). ln the hllman brain three main types of oligodendrocytes can be identified on the basis of their location and presence during development: 1) Perineuronal stellate cells which are found apposed to the neuronal perikarya or dendrites.…”