The distribution of oligodendrocytes in cerebral gray and white matter of several mammals

Abstract

This comparative study on the regional arrangements of oligodendrocytes, as a supplement to the preceding study on perivascular distribution (Cammermeyer, '60e), has as a main objective to point out a number of cytoarchitectonic peculiarities, as e.g., the concentration of these cells in the periphery of gray matter and the adjacent white matter. These anatomical observations may offer additional circumstantial evidence in support of the hypothesis that the oligodendrocytes occupy positions consistent with intrinsic blood flow control to neurons (Cammermeyer, '60a,d,e), which substitutes for the previously suggested hypothesis that oligodendrocytes are concerned with neuronal metabolism and myelin synthesis @el Rio-Hortega, '22, '28). MATERIAL AND METHODSThe brains of male primates (Macaca mulatta, Macaca cynomolgus, squirrel monkey), carnivores (4-year-old Irish setter, raccoon, cat), lagomorph (20-monthold New Zealand rabbit), rodents (chinchilla, guinea pig, hamster, glider squirrel, rat, mouse) and marsupial (Didelphis marsupialis) used in the preceding studies (Cammermeyer, '60b,d,e) were fixed by a two-step perfusion method. The blood vessels were flushed with saline or gum acacia in saline and then with a modified Heidenhain's Susa solution. The autopsy was performed after the lapse of 4 hours.A sample of the brain was obtained by coronal sections through the optic chiasm and the infundibulum; it was placed immediately in alcohol and after 4 days in par&;and microscopic sections were stained by the periodic acid-SchB (PAS) treatment followed by immersion in gallocyanin-chrome alum, pH 1.7 or 2.5, for 24 hours at room temperature. MICROSCOPIC EXAMINATIONPrimates. The distribution of oligodendrocytes2 in the M. mulatta is in brief as follows:The first cortical layer has very few oligodendrocytes but they are slightly more numerous along the medial aspect of the hemisphere, over the superior frontal gyrus and over the dentate gyrus, than over the rest of the convexity. These cells usualIy occur singly. Sparse oligodendrocytes adhere to the blood vessel even if it continues into the second cortical layer and impinges upon the surface of several small neurons, as exemplified by a figure of the chinchilla in which the neurons are close together ( fig. 2). Within a small area of malformation, a so-called cortical "wart," where neurons of small and medium size occupy the 1st cortical layer, the oligodendrocytes are rare. The occurrence of juxtavascular oligodendrocytes varies greatly in the remaining cortical layers; the greatest number being in the deep cortical layers of the region of Betz's cells ( fig. 10) and the smallest number in both the gprus cinguli ( fig. 3) and pyramidal cell layer of the hippocampus ( fig. 19).Subjacent to the subcortical white matter the oligodendrocytes form lengthy rows, which occur in greatest number in gyri surrounding the lateral cerebral fissure ( fig. 11). The rows are often longer than those seen in the figure. Towards the superior aspect of the hemisphere, the oligodendrocy...

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