Perineuronal satellite cells in the motor cortex of aging brains.

Abstract

Information regarding the supportive system of glia which lends reinforcement to the neuron and its processes was greatly advanced by del Rio Hortega (8), who described the perisomatic and periaxonic cells. The satellite system under investigation here embodies the perisomatic glia cells which surround the body of the neuron and its dendrites. These cells are located in such positions as to have part or all of their cytoplasmic extensions in contact with an adjacent neuron or neurons. Cajal (12, 13) suggested that the perineuronal satellite cells, which for the most part were made up of oligodendroglia, lived symbiotically with nerve cells. An increase in number of perineuronal satellite cells is a phenomenon that, for a long time, has been associated with abnormality in nervous tissue. However, it has also been shown by Critchley (7), Andrew (2), Bailey (3), Riese (14), and Brownson (6), that such a numerical increase in satellite cells does not necessarily indicate necrobiosis in neurons. On the contrary, satellitosis could suggest a vitalizing-like phenomenon. Satellitosis is a condition that often characterizes the essentially normal, aged neurological specimens. Brain and Greenfield (5) called attention to the common disappearance of periaxonic oligodendroglia in arterial sclerosis. They also remind us that it is impossible now to decide to what extent myelin degeneration of nerve fibers might be due to the failure of nutritive action of oligodendroglia or vice versa. Pomerat (11) has further emphasized the importance of the view that oligodendroglia may sub serve a special role in metabolism of neurons. It has been the author's experience that an intense degree of perineuronal satellitosis was present. not only in aged human brains but also in very young, normal brains (6). Such records of hyperplasia in both extremes of the age spectrum immediately raises the question as to whether these cells comprise the same or different types of glia in similar or dissimilar ratios. With this concept in mind the following qualitative analysis was performed in anticipation of establishing some ratios among perineuronal neuroglial satellite cells with special emphasis on the age factor.