Phylogenetic evolution of intermediate filament associated proteins in ependymal cells of several adult poikilotherm vertebrates.

The cytoskeletal proteins are phylogenetically well preserved in Vertebrates. However, unlike the case of Mammals, comparatively little is known about the immunocytochemical characterization of the intermediate filaments (IF) of the ependymal epithelium cells in the lower Vertebrates. The immunohistochemical response of the ependymal epithelium of the spinal cord has been examined in several poikilotherm Vertebrates. The latter were selected on the basis of the high degree of variation in adult spinal cord plasticity, a property due to the ependymal cells and probably related to different IF-associated proteins contained in them. In Triturus (Urodele Amphibian) the presence of cells having an exclusively vimentine positive cytoskeleton, apparently not organized into filamentous structures, was observed throughout ependymal epithelium. In Rana (Anuran Amphibian) the ependymal epithelium cells were found to be comparatively positive with respect to both vimentine, which was structured into cytoskeletal filaments, and glial fibrillary acidic protein (GFAP), detected using monoclonal anti-chicken-GFAP antibodies. In Lacerta (Scaly Reptile) the ependymal epithelium cells only rarely had a vimentine positive cytoskeleton and mostly appeared to stain intensely with polyclonal anti-bovine-GFAP. The different immunocytochemical response of the cytoskeleton of the ependymal epithelium cells in the poikilotherm Vertebrates examined can be explained in terms of the varying plasticity of the spinal cord. In adult animals, this plasticity is still high in the Urodeles, lower in the Anurans, much weaker in the Reptiles and disappears completely in the homeotherm Vertebrates.