[Morphology of glial cells in the lower olivary complex of the pigeon (Columba livia). II. Oligodendrocytes].

The morphologic peculiarities of oligodendrocytes in the lower olivary complex (LOC) of a pigeon were examined at light and electron microscopy level. The analysis on the basis of the applied histological techniques (staining with cresyl-violet and silver impregnation according to Goldgi-Rio Hortega) showed that oligodendrocytes were small rounded cells with nuclei stained more darkly than those of astrocytes. Oligodendrocytic arborizations were thin, slightly ramified and small in number. The predominant number of oligodendrocytes were of median type in LOC of a pigeon, observed by the electron microscope. The nuclei of oligodendrocytes were dense, seen by the electron microscope, in comparison with those of the astrocytes. The cytoplasm contained abundance of short and median cysternae of granulated endoplasmic reticulum, microtubules, but there were no microfilaments. Gap junctions contacts of the type astro-oligodendrocytes were found on the surface of cellular membrane. Oligodendrocytes were located in the perineuronal position, connected with myelinated nervous fibers or were situated freely among the elements of the neuropila. The functional significance of these glial cells and their probable role in neuronal metabolism is discussed on the basis of the comparative analysis of the morphologic characteristics of oligodendrocytes in LOC of a pigeon and those of mamals. The present work is a part of our observations on the structure of LOC in phylogenic aspect.