EPENDYMA - PHYLOGENETIC EVOLUTION OF GLIAL FIBRILLARY ACIDIC PROTEIN (GFAP) AND VIMENTIN EXPRESSION IN VERTEBRATE SPINAL-CORD

The phylogenetic evolution was studied of both glial fibrillary acidic protein (GFAP) and vimentin expression in the ependyma of the adult v ertebrate spinal cord. Eleven species from different vertebrate groups were examined using different fixatives and fixation procedures to de monstrate any differences in immunoreactivity. GFAP expression in the ependymal cells showed a clear inverse relation with phylogenetic evol ution because it was more elevated in lower than in higher vertebrates . GFAP positive cells can be ependymocytes and tanycytes, although dep ending on their structural characteristics and distribution, the scarc e GFAP positive ependymal cells in higher vertebrates may be tanycytes . Ependymal vimentin expression showed a species-dependent pattern ins tead of a phylogenetic pattern of expression. Vimentin positive ependy mal cells were only found in fish and rats; in fish, they were tanycyt es and were quite scarce, with only one or two cells per section being immunostained. However, in the rat spinal cord, all the ependymocytes showed positive immunostaining for vimentin. The importance of the im munohistochemical procedure, the cellular nature of GFAP positive epen dymal cells and the relationship between tanycytes and ependymocytes a re discussed, as well as GFAP and vimentin expression.