Preparation and discharge of secretion in the subcommissural organ of the rat

Abstract

The secretion of the subcommissural organ (SCO) of the rat was studied by means of immunocytochemistry at the electron-microscopic level with the use of (1) the polar embedding medium Lowicryl K4M at -30 degrees C, (2) the protein A-gold technique, and (3) a rabbit antiserum against bovine Reissner's fiber (see Sterba et al. 1981). Two different substructures of the ependymal and the hypendymal SCO-cells display a positive immunocytochemical reaction: (1) sacs containing flocculent secretion, which originate from the granular endoplasmic reticulum, and (2) vacuoles filled with fine granular secretion, which are pinched off from the Golgi apparatus. The secretory material of the sacs and the vacuoles is discharged both (i) apically into the cerebrospinal fluid and (ii) basally into intercellular spaces of the SCO-hypendyma. The apically released secretion is condensed to a lamina-like formation, which more caudally assumes the form of Reissner's fiber. The route of the basally released secretion remains, however, vague. The "periodically striated bodies", which were thought to be morphological mediators of the discharge of the secretion into the capillaries, are never labeled by gold particles.

Polarized expression of integrin β1 in diencephalic roof plate during chick development, a possible receptor for SCO‐spondin

“…In these animals, the immunoreactive material was observed on the basal process endfeets and associated to blood vessels; however, the secretory pathways of SCO-spondin toward the leptomeningeal space as well as the sorting of this protein through the perivascular space and the endothelial cells have not been demonstrated. On the other hand, following immunoelectron microscopy in the adult rat brain, Losecke et al (1984) also found AFRU-immunoreactive material within the intercellular spaces between the basal processes but no signal was observed in the endothelial cells of the capillaries. Of interest, Schoebitz et al (1986) described the presence of AFRU-immunoreactive material in the basal processes of chick embryos incubated for 5 days as well as in the adult stage, but the methodology used in this study did not discriminate whether this material was inside these processes or aggregated on the surface.…”

“…Even though the apical secretion of SCO-spondin toward the cerebrospinal fluid has been widely described, it is not clear if SCOspondin is also secreted by the basal prolongations, and the destination of this hypothetical secretion. In the few studies related to the basal secretion (Losecke et al, 1984(Losecke et al, , 1986Biosca and Azcoitia, 1989;Rodríguez et al, 1984a,b;Peruzzo et al, 1990), the authors performed studies in adult animals, and concluded that basal secretion of SCO-spondin was probably toward the blood vessels or toward the subarachnoidal space. Nonetheless, despite the fact that SCO-spondin has been suggested to play a role in PC development (Gobron et al, 2000;Meiniel, 2001;Ferná ndez-Llebrez et al, 2001;Lehmann and Naumann, 2005), there are no reports addressing the basal secretion of this protein toward the extracellular matrix that surrounds the axons of the PC at embryonic stages.…”

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

“…The ventricular discharge of its secretory products and their involvement in the formation of Reissner's fibre, a structure of unknown function running throughout the length of the spinal canal, have been established by ultrastructural, histochemical, immunocytochemical and autoradiographic studies (Ermish et al, 1971;Krstic, 1975;Hess et al, 1977;Tulsi and Kennaway, 1979;Hofer et al, 1980;Sterba et al, 1981Sterba et al, , 1986Vullings et al, 1986). Morphological observations (Oksche, 1969;Murakami et al, 1969;Kimble and Mollgard, 1973) and more recently immunocytochemical results (Sterba et al, 1982;Tulsi, 1983;Rodriguez et al, 1984 a, b;L6secke et al, 1984, 1986) also suggest a hypendymal vascular release.…”

The subcommissural organ

“…The pre-RF material and the material stored in the apical secretory granules share the same histochemical (Herrera and Rodríguez, 1990;W. Naumann, 1968;Oksche, 1961;Olsson, 1958a,b;Rodríguez et al, 1986;Wingstrand, 1953), and immunocytochemical (Herrera and Rodríguez, 1990;Lösecke et al, 1984;Rodríguez et al, 1986Rodríguez et al, , 1987a characteristics. Pre-RF is readily visualized with transmission (Hofer et al, 1980;Krstic, 1973;Mü ller and Sterba, 1965;Rodríguez, 1970a) and scanning (Krstic, 1975; Sturrock, 1984;Weindl and Schinko, 1975) electron microscopy.…”

“…Ultrastructural immunocytochemistry using polyclonal and monoclonal antibodies has demonstrated strong labeling of the secretory material located in the dilated RER cisternae (Figs. 15, 16) and the secretory granules located at the apical cell pole (Grondona et al, 1994b;Lösecke et al, 1984;Pérez et al, 1995;Peruzzo et al, 1990;Rodríguez et al, 1986Rodríguez et al, , 1987a and in the vascular and leptomeningeal ependymal endings Rodríguez et al, 1987b). There are monoclonal antibodies that react with the secretory granules but not with the RER content .…”