Ontogenetical study of the chick embryo subcommissural organ by lectin-histofluorescence and electronmicroscopy

Abstract

The secretory activity of the subcommissural organ (SCO) was studied during embryogenesis of the chick (Gallus gallus) using two lectins labelled with fluorescein isothiocyanate, concanavalin A (Con A) and wheat-germ agglutinin (WGA). While WGA labels the apical or ventricular border of the organ, Con A labels both, the apical and vascular poles of the cells. Glycoproteinaceous secretory products, visualized by Con A appear early, at 5 days, in the ependymal epithelium and expand progressively in a rostrocaudal direction. A correlation is established between histofluorescence and the ultrastructural aspects of the ependymocytes. This throws light on the role of the endoplasmic reticulum in the synthesis, storage and transport of the material produced by the SCO, and points to the existence of two poles of exchange between the secretory cells and the extracellular medium, i.e., the ventricular and the vascular one. WGA reactivity at the apical border is linked up with the formation of Reissner's fibre and shows that the secretory product of the SCO cells undergoes at least partly modifications during its intracytoplasmic transport preceding apical discharge.

Glycoprotein synthesis in the subcommissural organ of the chick embryo

“…The appearance of IRM in the secretory ependymal cells of the SCO parallel that of Concanavalin A-positive glycoproteins (Bruel et al, 1987). During the following stages (5 to 12 days), the immunostaining extended caudalward in the SCO epithelium according to a rostro-caudal gradient of differentiation.…”

“…The appearance of IRM in the secretory ependymal cells of the SCO parallel that of Concanavalin A-positive glycoproteins (Bruel et al, 1987). After absorption with crude brain extract, the IgG fraction was purified by ion exchange chromatography.…”

Monoclonal Antibodies as Probes for the Analysis of the Secretory Ependymal Differentiation in the Subcommissural Organ of the Chick Embryo

“…In earlier ontogenetic studies on the chick embryo SCO, the first signs o f release of secretory material into the ventricular cavity were detected at the 7th day [10,11,13]. The appearance of RF in the central canal of the spinal cord would take place at either the 11th [13] or the 12th day [10].…”

“…The SCO shows a rem ark able phylogenetic and structural constancy in all chordate classes [8,9] appearing very early during ontogene sis [10][11][12][13][14]. We decided to investigate some molecular characteristics of this organ.…”

GABA uptake and phenotypic characteristics of the subcommissural ependymocytes of the semi-desertic rodent, Meriones shawi: correlation with serotoninergic innervation

“…This organ appears during early ontogeny in various species (Calvo and Boya 1981;Schoebitz et al 1986;Bruel et al 1987) and is principally composed of modified ependymocytes that contribute to the glycoprotein secretory activity of the central nervous system (Hess and Sterba 1973;Meiniel and Meiniel 1985;Diederen et al 1987;Karoumi et al 1990). It has been postulated to play a role in water-balance regulation (Lenys 1965;Fidelina 1972;Ziegels 1976;Buijs and Pévet 1980;Vullings and Diederen 1985;Karoumi 1989;Severs et al 1993).…”