Glial fibrillary acidic protein and vimentin immunohistochemistry in the developing and adult midbrain of the lizard Gallotia galloti

Abstract

The distribution of glial fibrillary acidic protein (GFAP)- and vimentin-containing cells was studied by immunohistochemistry in the midbrain of the lizard Gallotia galloti. At embryonic stage 32 (E32), vimentin immunoreactivity appeared first in cell bodies located in the ventricular walls, in radial fibers, and subpial end-feet and increased in these structures until E34/E35. Faint GFAP immunoreactivity gradually appeared in the same structures between E34 and E37, and this increased until adulthood, whereas vimentin immunoreactivity decreased after E35, becoming limited to a few end-feet and fibers in the adult, mainly in the tegmentum. Thus, in developing Gallotia midbrain a shift from vimentin-containing to GFAP-containing intermediate filaments begins around E36 or E37. At E40, in addition to the cell bodies in the ependymal area, dispersed GFAP-positive cells, possibly immature astrocytes appeared. These cells showed the same shift. In the adult lizard, GFAP-positive radial glia are still present and coexist with GFAP-positive astrocytes, which are prefentially located in the marginal optic tract and the oculomotor nuclei, but are absent in the fasciculus longitudinalis medialis. Optic tectum, pretectum, tegmentum, and isthmic nuclei are the areas richest in GFAP-positive radial fibers: these were much less abundant in the deep mesencephalic nuclei. Thus, in this lizard, GFAP-positive astrocytes display a clear cut regional distribution: they are present in mesencephalon, whereas they are absent in telencephalon.

Glial fibrillary acidic protein and vimentin immunoreactivity of astroglial cells in the central nervous system of adult Podarcis sicula (Squamata, Lacertidae)

“…The absence of GFAP-positive star-shaped astrocytes in Podarcis telencephalon is in accordance with observations on Gallotia (Yanes et al 1990) where only GFAP-positive ependymal cell bodies and their radial fibres are observed in the telencephalon. The same GFAP-immunolocalisation is found in the turtle, the CNS of which lacks typical astrocytes and possesses only a radial glial pattern (Kalman et al 1994).…”

“…Moreover in mammals, even though vimentin-immunopositive glial structures can be detected from the first embryonic stage, this antigen is progressively replaced by GFAP during maturation (Pixley & De Vellis, 1984 ;Elmquist et al 1994). Conversely, in Podarcis as in Gallotia, radial glial elements are still present in adults (Monzon-Mayor et al 1990 ;Yanes et al 1990), even if during lacertian development the molecular composition of the intermediate filaments in these cells changes. In fact in the embryonic Gallotia galloti, vimentin appears as the main component of the intermediate filaments in radial glial structures (Monzon-Mayor et al 1990 ;Yanes et al 1990).…”

“…Conversely, in Podarcis as in Gallotia, radial glial elements are still present in adults (Monzon-Mayor et al 1990 ;Yanes et al 1990), even if during lacertian development the molecular composition of the intermediate filaments in these cells changes. In fact in the embryonic Gallotia galloti, vimentin appears as the main component of the intermediate filaments in radial glial structures (Monzon-Mayor et al 1990 ;Yanes et al 1990). However, in Podarcis as in Gallotia, vimentin-immunoreactive glial structures have almost completely disappeared in the adult except for a few fibres and endfeet in the tegmentum of Gallotia (Monzon-Mayer et al 1990) and in the ventral diencephalon and spinal cord ependyma of Podarcis.…”

“…Even though vimentin has been found in immature cells of the astroglial lineage in mammals (Elmquist et al 1994 ;Pulido-Caballero et al 1994) and reptiles (Monzon-Mayor et al 1990 ;Yanes et al 1990), it is still present in adult glial cells in teleosts and amphibians (Zamora & Mutin, 1988 ;Cardone & Roots, 1990 ;Rubio et al 1992 ;Lazzari et al 1997). Furthermore, vimentin is highly conserved in phylogenesis as suggested by the cross reaction of antibodies produced against mammalian vimentin with the corresponding protein in birds and amphibians (Bennett et al 1978 ;Szaro & Gainer, 1988 ;Zamora & Mutin, 1988 ;Bodega et al 1994).…”

“…In particular, with regard to the saurian CNS, immunocytochemical studies on the cytoskeletal components of glial cells have only been performed in Gallotia galloti (Monzon-Mayor et al 1990Yanes et al 1990), Anolis carolinensis , Lacerta sicula (Lauro et al 1991) and Lacerta lepida (Bodega et al 1990(Bodega et al , 1994.…”