ULTRASTRUCTURAL CHARACTERISTICS OF GLIAL FIBRILLARY ACIDIC PROTEIN EXPRESSION IN EPOXY RESIN-EMBEDDED HUMAN BRAIN-TUMORS

Thirteen surgically removed, epoxy resin (Durcupan ACM or Epon 812)-em bedded human brain tumors were examined for glial fibrillary acidic pr otein (GFAP) content in semithin and ultrathin sections with the immun ogold-silver staining method. Mild aldehyde fixation and the hydrophob ic resin embedding did not interfere with the antigenicity, since silv er intensification of the immunogold marker provided excellent visuali zation of the reaction on both light microscopic and ultrastructural l evels. The GFAP reaction was usually localized on the glial intermedia te filament bundles, usually correlating well with the amount of filam ents. The unstained filamental regions of two ependymomas might corres pond to the vimentin expression revealed by double labeling in semithi n sections. Occasional GFAP immunopositivity without filamental appear ance was observed in one of the oligodendrogliomas, as patchy electron -dense cytoplasmic corpuscules, in Rosenthal fibers and in some mainly necrobiotic tumor cells, reflecting a possible connection with glial filaments.