Glial fibrillary acidic protein (GFAP) immunoreactive astrocytes in the CNS of normal and rabies-infected adult cattle. I. Hippocampus and dentate gyrus

Abstract

Glial fibrillary acidic protein (GFAP) belongs to the group of intermediate filaments of the cell cytoskeleton. It is present in astrocytes and in some ependymal cells. Detection of GFAP is useful for the identification of astrocytes in a highly specific manner. In the present study, peroxidase antiperoxidase (PAP) immunohistochemical staining, with a specific antibody against GFAP was employed to determine the distribution and morphology of astrocytes in the hippocampus and dentate gyrus of normal cattle and cattle naturally infected with rabies. Paraffin sections of buffered formalin-fixed tissue were used. Positively brown coloured astrocytes in each region were classified into four levels of intensity. The number of astrocytes per mm2 was determined using a straight scale ocular micrometer. Nuclear area, larger and smaller diameter of astrocytes were also determined with an image analyser system. It was observed that the morphology of astrocytes varied in the différents microregions of hippocampus and dentate gyrus. Cattle with rabies showed astrogliosis represented by strong immunoreaction, enlargement of cell body, cytoplasm and processes. The nuclei were also enlarged and light in colour. Astrocitosis was also present. Neurons showed no alterations. These results represent a contribution to the knowledge of the normal distribution and morphology of astrocytes which permits a better understanding of pathological conditions.