Detection of glial fibrillary acidic protein (GFAP) and vimentin (Vim) by immunoelectron microscopy of the glial cells in the central nervous system of the snail Megalobulimus abbreviatus

When examined under an electron microscope, the central nervous system of Megalobulimus abbreviatus showed two types of glial cells: firstly, protoplasmic glial cells which displayed a nucleus with peripheral heterochromatin, scanty or no intermediate filaments, a developed Golgi complex, rough and smooth endoplasmic reticula, mitochondria and polymorphic lysosomes that indicate phagocytic activity of debris from the extracellular space; and, secondly, fibrous glial cells which showed numerous glial fibrillary acidic protein (GFAP) and vimentin immunoreactive intermediate filament bundles, a discrete Golgi complex, mitochondria, endoplasmic reticulum, lipid droplets and lysosomes. The contacts between the glial cells consisted of desmosomes and puncta adherentia , while those between the glial cells and the basal lamina consisted of hemidesmosomes. Both glial cell types were located in the cortex and medullary regions, however, the protoplasmic glial cells prevailed in the cortical region, while the fibrous glial cells prevailed in the medullar region. As the nervous tissue is avascular, the passage of nutrients and waste products may be facilitated by the glial labyrinthic system which is located in the cortical region. Glial processes adjacent to large and giant neurones formed a trophospongium, which seemed to be involved in a metabolic exchange between these cells. Thus, this evidence suggests that glial cells of M. abbreviatus are involved in structural support, isolation of different ganglionic areas, the formation of a microcirculatory system and an intimate metabolic relationship with neurones.