MORPHOLOGICAL ORGANIZATION OF NEUROPIL GLIAL-CELLS IN THE CENTRAL-NERVOUS-SYSTEM OF THE MEDICINAL LEECH (HIRUDO-MEDICINALIS)

Neuropile glial (NPG) cells in the central nervous system of the medic inal leech, Hirudo medicinalis, were studied by histological, histoche mical and immunocytochemical techniques. The NPG cells are often surro unded by electron-dense microglial cells. The central cytoplasm of NPG cells shows a significant zonation. The zone around the nucleus conta ins mitochondria, glycogen and vesicles. The cytoplasm also contains m any ribosomes, a few dictyosomes and distinct inclusions up to 2 mu m in diameter. A second zone around the perinuclear region is marked by the occurrence of bundles of intermediate filaments that correspond in thickness to glial filaments of vertebrates. We found a positive reac tion with polyclonal antibodies against human glial fibrillary acidic protein (GFAP), and the areas of intense fluorescence correspond to th e regions where intermediate filaments were found to be abundant. The peripheral zone contains numerous membrane stacks that could not be co ntrasted by lanthane nitrate or tannic acid. Therefore, the membrane s tacks could be part of an extensive smooth endoplasmic reticulum, whic h is characteristic of cells with active lipid metabolism.