The relationship between enzyme activity and neuroglia in plaques of multiple sclerosis

Abstract

To ascertain whether the oligodendroglia are primarily affected, secondarily affected or in fact disappear from plaques, the neuroglia and certain enzymes were analyzed in 33 plaques from ten cases of multiple sclerosis. Counts of neuroglia cells and total nuclei were made on silver impregnated sections. Additional counts of the three different types of neuroglia nuclei and total neuroglial nuclei were made on hematoxylin-eosin preparations. Histochemical methods included those for adenosine triphosphatase (ATPase), lactic dehydrogenase, diphosphopyridine nucleotide diaphorase (DPND) and 5-nucleotidase. Sudan black and osmium tetroxide a-naphthylamine (OTAN) methods were used for triglyceride fats, cholesterol esters and phospholipid. Oligodendrocytes increase throughout the lesion in the small early plaques and mainly at the edge in the active older plaque. Oligodendrocytes were reduced at the center of the older plaque but the loss was not complete. Enzyme histochemistry showed (1) a marked increase in activity of oxidative and hydrolytic enzymes at the edge of active older plaques coinciding with increased oligodendrocyte counts; (2) enzyme activity and oligodendrocyte counts low in old, inactive plaques but astrocytes prominent; and (3) enzyme activity and oligodendrocyte populations increased throughout the early plaque but the astrocytes were relatively inconspicuous. These data suggest that the increase in enzyme activity is related to the increase in oligodendroglia. The major part of the enzyme reaction is in the form of fine granules, possibly mitochondrial in nature, in the neuropil. It is concluded that the increase in enzyme activity at the edge of the plaque is primarily located in neuroglial mitochondria scattered diffusely throughout the neuropil.