DISTRIBUTION OF GLIAL FIBRILLARY ACIDIC PROTEIN IMMUNOPOSITIVE STRUCTURES IN THE DEVELOPING BRAIN OF THE TURTLE MAUREMYS LEPROSA

This study is a continuation of the description of the glial fibrillar y acidic protein (GFAP)-immunopositive structures in the adult turtle brain (Kalmin et al. 1994) and presents a comprehensive description of the development of these structures from the 20th embryonic day (E20) to the adult age. GFAP-immunopositive elements were first detected at E28 and by E34 the GFAP-immunopositivity was apparent throughout the brain, except the cerebellum. The appearance of GFAP seemed to be rela ted to the end of cell migration and the formation of the thickened pa rts of the brain wall, such as the dorsal ventricular ridge. After hat ching the pattern of the GFAP-immunopositivity differed from that in t he adult only in minute details, except for the brain tracts in which GFAP-pattern was still changing due to myelination, and the molecular layer of the cerebellum in which a transverse fiber system appeared. T he GFAP-positive elements belonged originally to the ependymoglia, but later the distortion due to the morphogenetic processes of branching and division changed the pattern almost beyond recognition. In some ca ses cell bodies - ependymal and non-ependymal - appeared to be GFAP-po sitive, but no astrocytes (i.e., stellate cells) were detected. The re sults are discussed in the light of previous observations on developin g mammalian, avian and lizard brains.