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PubMed1996

Identification of a high molecular weight polypeptide in the subcommissural organ of the chick embryo.

The subcommissural organ is an ependymal brain gland that secretes, into the ventricular cerebrospinal fluid, high molecular weight glycoproteins that form Reissner's fiber. Precursor and processed forms of secretion have been demonstrated by immunoblotting in the subcommissural organ of mammals and fish. In the chicken only a processed form has as yet been identified. In the present report, we have studied the subcommissural organ of 13-day-old chick embryos using (1) an antiserum against bovine Reissner's fiber, and (2) the lectins, concanavalin A and Limax flavus agglutinin. Paraffin sections of the subcommissural organ and blots of subcommissural organ extracts have been analyzed. The ependymal cells of sectioned subcommissural organ are strongly stained with the antiserum. Concanavalin A binds to materials in all cytoplasmatic regions, whereas Limax flavus agglutinin identifies materials confined to the apex of the ependymal cells. In the blots, a band of 540 kDa is immunostained. This band is positive for concanavalin A positive but negative for Limax flavus agglutinin and is thereby regarded as representing a precursor form of the secretion.

Animals↗
PubMed2001

Presence and functional significance of neuropeptide and neurotransmitter receptors in subcommissural organ cells.

The subcommissural organ (SCO) of mammals is innervated by several neuropeptide and neurotransmitter systems. So far, substance P (SP), oxytocin (OXT), vasopressin (VP), somatostatin (SOM), thyrotropin-releasing factor (TRF), and angiotensin II (ANGII) were identified in neuropeptidergic input systems, and serotonin (5HT), gamma-amino butyric acid (GABA), noradrenaline (NA), dopamine (DA), and acetylcholine (Ach) were neurotransmitters observed in systems afferent to the SCO. In the present report, based on literature data and our own investigations, we describe the occurrence of peptide and transmitter receptors in the SCO by means of autoradiographic and biochemical studies. Further, we summarize aspects of the signal transduction cascades possibly linked to different receptor types of the SCO; these studies included the use of calcium imaging (FURA-2 technique), ELISA technique, and immunocytochemistry. Receptors were identified for adenosine, angiotensin II, imidazoline, glucocorticoids, mineralocorticoids, NA, and embryonic brain kinase. The studies on intracellular signal-transduction indicated receptors for tachykinins and for ATP. In SCO cells, Ca(++) and c-AMP were identified to act as second messengers. As important transcription factor, cAMP-/Ca(++)-response element binding protein (CREB) was observed. Ach and NA did not show a significant effect on the subcommissural signal transduction.

Adenosine↗
PubMed1992

Developmental neuron-glia interactions: role of serotonin innervation upon the differentiation of the ependymocytes of the rat subcommissural organ.

The rat subcommissural organ (SCO), which forms the roof of the third ventricle is an adequate model to study certain mechanisms of neuron-glia interactions in vivo. The ependymocytes, the main component of the SCO, have a glial origin. They possess particular phenotypic characteristics: they accumulate [3H]GABA by a specific uptake mechanism, contain transitory GFAP during ontogenesis and do not express PS100; on the other hand they receive a 5HT input which forms typical synaptic contacts. This innervation is of particular interest to approach neuron-glia interactions during the differentiation. Studies of GABA uptake carriers during ontogenesis in SCO ependymocytes show a correlation between the onset of the 5HT innervation and the advent of the GABA uptake. Moreover, destruction of the 5HT innervation by a neurotoxin (5-7-dihydroxytryptamine), before its arrival at the SCO in newborn rat, inhibits the formation of the GABA uptake system and causes the expression of PS100 in adult SCO cells. On the other hand, the SCO of newborn rats transplanted to the fourth ventricle of an adult host rat had no capacity to take up GABA and expressed PS100 3 months after its transplantation. Finally, the SCO ependymocytes of species devoid of 5HT innervation (rabbit, mice) were unable to take up GABA and contain PS100. These data suggest that neuron-glia interactions are necessary for the advent of GABA uptake carriers and can control the expression of glial markers during ontogenesis in SCO ependymocytes.

Aging↗
PubMed1975

The surface fine structure of the bovine subcommissural organ.

The bovine subcommissural organ was studied by using scanning electron microscopy. The most prominent findings was the existence of protruded and dilated endings of the ependymal cells. The majority of these cells were ciliated with two or more cilia; only a few unciliated cells were seen. Some pore-like structures were also seen on the surface. From the functional point of view, the most interesting finding was an amorphous heterogeneous material on the subcommissural ependyma. Especially in the caudal part of the organ this material accumulated in abundance. No real filamentous structures such as Reissner's fibre could be seen, however, it was assumed that the heterogeneous material corresponds to this formation. No supraependymal neurones were demonstrated.

Animals↗
PubMed1995

Specific transcripts analysed by in situ hybridization in the subcommissural organ of bovine embryos.

The subcommissural organ (SCO) secretes specific glycoproteins into the cerebrospinal fluid that aggregate to constitute Reissner's fiber (RF), a thread-like structure running along the central canal of the spinal cord. For further identification of the gene(s) encoding these secretions, we have prepared a cDNA library in the vector IGT11 from bovine embryonic SCO. The screening of this library was performed using a polyclonal antibody raised against bovine RF. Three positive clones were isolated and purified and one of these lambda RF101 comprising an insert of #400 nucleotides was undercloned into pBluescript plasmid and mapped. After labeling with 35S (ATP) this cDNA fragment served as a probe to analyse the presence of specific transcripts in the subcommissural organ of the embryonic bovine by in situ hybridization. A labeling signal was observed in the embryonic SCO both in the secretory ependymal and hypendymal cells. This labeling is specific since the ependymal layer bordering the ventricular cavity as well as the surrounding nervous tissue remained negative. Thus, the embryonic SCO contains specific transcripts that are colocalized with the specific glycoproteins as shown after the use of a specific monoclonal antibody C1B8A8. In addition, the pattern of labeling with the specific SCO cDNA is different from those of beta actin cDNA and tear lipocalin cDNA, which, respectively, served as positive and negative controls. In a subsequent set of experiments the expression pattern was compared in embryos at two different stages of development (4-month-old and 8-month-old embryos).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Morphological features of the surface of the subcommissural organ and aqueduct in the red necked wallaby (Wallabia rufogrisea).

The subcommissural organ and aqueduct of the red necked wallaby were examined using scanning electron microscopy. The surface of the subcommissural organ was similar to that of the possum brain and was superficially similar to that of the rat. However, on close examination, the apical protrusions composing the eutherian subcommissural organ were not present and tight clusters of microvilli were noted instead. Caudal to the subcommissural organ and on each side of the mesocoelic recess there were ciliated paramedian folds. These have been described in the possum but have not been noted in any eutherian mammalian brain. It is believed that these structures are peculiar to marsupial brains. Zones B and C (caudal to the subcommissural organ) represent a superior convex bulge into the aqueduct and then a concavity in the roof of the aqueduct, respectively. Both zones had sparsely ciliated ependyma, the cell surfaces being covered by microvilli. The most caudal zone, C, was much wider and longer than zone B. A line of cells in the roof of the aqueduct similar to zone C has been observed in eutherian mammalian brains in which a dorsal dilation is present. Furthermore, a ridge of long thin ependymal cells has been noted in the roof of the mesencephalon in prenatal rats as early as 16 days of gestation. It is postulated that this region is a circumventricular organ present in ontogeny in all mammals, persisting into the adult only in those with a dorsal dilation in the aqueduct.

Animals↗
PubMed1986

[Immunohistochemical investigations on the ontogenesis of the subcommissural organ].

Using an antiserum raised against bovine Reissner's fiber a ventricle border of the matrix epithel reacting in the immunohistochemical procedure according to Sternberger et al. (1970) is visible in the very early stage of the embryonic brain of Pleurodeles waltli. In the basal region of the brain the immunoreactive border later develops into the flexural organ a secretory cell formation that is situated in the deuterencephalon and spinal cord. The cells of the flexural organ release a glycoprotein into the cerebrospinal fluid, where, among other things, the Reissner's fiber is formed. Later on, Reissner's fiber is produced no longer by the flexural organ, but the subcommissural organ. It is suggested that in the very early embryonic stage the immunohistochemically reactive ventricle border, too, contains a glycoprotein that might contribute to any events in the ontogeny of the nervous system.

Animals↗
PubMed1994

Alterations of the subcommissural organ in the hydrocephalic human fetal brain.

We have studied the subcommissural organ of two hydrocephalic brains, of 20 and 21 gestational weeks and of two normal brains, aged 19 and 23 gestational weeks. Both hydrocephalic cases presented a size reduction of the subcommissural organ compared to the normal cases; only in one case, there were also alterations of the morphological components of the subcommissural organ, suggesting different pathogenic relationships between hydrocephalus and dysplasia of the subcommissural organ.

Abortion, Spontaneous↗
PubMed2001

Multiple forms of glycoproteins in the secretory product of the bovine subcommissural organ--an ancient glial structure.

The glial subcommissural organ (SCO) is a conserved structure of the vertebrate brain that secretes a glycoprotein-rich product into both the extracellular matrix and the cerebrospinal fluid of the third ventricle that forms Reissner's fibre (RF). In order to identify specific secretory proteins of the subcommissural organ, a panel of antigen- and epitope-specific monoclonal antibodies was raised against bovine RF to study the distribution of epitopes in Western blots of bovine RF. Six groups of epitopes that were specific for SCO secretion were distinguished on the basis of their phylogenetic conservation and their different grades of resistance against chemical denaturation. The monoclonal antibody aRFME 4 recognised a carbohydrate-containing epitope that was strongly conserved in vertebrates and unique for SCO secretion. All epitopes showed essentially the same distribution pattern over 15 bovine RF glycoprotein fractions of different molecular masses in immunoblots indicating that the different RF fractions are closely related. They may represent multiple forms of SCO spondin.

Animals↗
PubMed2000

Secretory activity and serotonin innervation of subcommissural organ.

We investigated immunohistochemically the subcommissural organ (SCO) glycoprotein secretion, its serotoninergic (5-HT) innervation and the possible control of this innervation upon the SCO activity in lizards (Agama impalearis, Saurodactylus mauritanicus and Eumeces algeriensis). Inside the SCO, interspecific differences in the intensity and the distribution of both secretary product and 5-HT nerve fibers were observed. Compared with Agama and Eumeces, the SCO of Saurodactylus displayed intense secretory products and several 5-HT fibers. In Saurodactylus, i.p. injection of parachlorophenylalanine, a potent inhibitor of 5-HT synthesis, produced a marked decrease of SCO secretory product. We report in this study species differences of the lizard SCO secretory activity and its possible physiological control by 5-HT innervation, as previously demonstrated in mammals.

Animals↗
PubMed2000

Secretory activity and serotonin innervation of lizard's subcommissural organ.

We investigated immunohistochemically the subcommissural organ (SCO) glycoprotein secretion, its serotoninergic (5-HT) innervation and the possible control of this innervation upon the SCO activity in lizards (Agama impalearis, Saurodactylus mauritanicus and Eumeces algeriensis). Inside the SCO, interspecific differences in the intensity and the distribution of both secretory product and 5-HT nerve fibers were observed. Compared with Agama and Eumeces, the SCO of Saurodactylus displayed intense secretory products and several 5-HT fibers. In Saurodactylus, i.p. injection of parachlorophenylalanine, a potent inhibitor of 5-HT synthesis, produced a marked decrease of SCO secretory product. We report in this study species differences of the lizard SCO secretory activity and its possible physiological control by 5-HT innervation, as previously demonstrated in mammals.

Animals↗
PubMed1977

Histological and ultrastructural study on the subcommissural organ of Bradypus tridactylus.

The subcommissural organ (SCO) of the Bradypus tridactylus was studied from the histological and ultrastructural point of view. The methods of GOMORI (alum-chromic-hematoxylin-phloxine), AZAN (M. Heidenhain), KLUVER and BARRERA (for nerve cells and myelinated fibers) and silver impregnation according to PALMGREN and CAJAL-DE CASTRO, were used. The material prepared for ultrastructural analize was submitted to the sequence of gluteraldehyde, osmium tetroxide, uranyl acetate and lead citrate. In function of the secretory phenomenon, a systematic study is made of different hystological and ultrastructural characteristics of the SCO and hypendymal rosettes, which were considered in the B. tridactylus as a morphofunctional unit. Fine vascular and nerve networks were observed, by the basal parts of the compact tubule alveolar system (hypendymal rosettes) which composes part of the SCO. Nerve fibers were seen between its cells reaching even up to the lumen, and they may end there in bulbar dilatations which seem to show secretory characteristics at the ultrastructural examination.

Animals↗
PubMed1995

Antibody-mediated lysis of the bovine subcommissural organ maintained in culture.

The subcommissural organ (SCO) is a brain gland that secretes glycoproteins into the cerebrospinal fluid (CSF). It is an ancient and conserved secretory structure of the brain, developing very early in ontogeny. However, the function of the SCO is unknown. The secretory cells of the SCO are arranged into a single or double, irregularly shaped layer located at the interface of the CSF and nervous tissue. This has prevented its selective surgical destruction. The present investigation was designed to destroy the secretory cells of 30-day-old explants of bovine SCO by use of an immunological approach. A membrane preparation enriched with plasma membrane of the secretory cells of the bovine SCO was obtained. This preparation was further processed to separate the structural proteins. A similar procedure was applied to obtain a fraction of integral proteins of the plasma membrane of a nonsecretory ciliated ependyma. Antisera were prepared against both preparations of integral proteins. The antiserum against the fraction obtained from the SCO cells immunostained the plasma membrane of the bovine SCO cells and in immunoblot it reacted with several proteins of the membrane preparation from SCO cells. When added to the culture medium this antibody bound to the apical plasma membrane of the secretory ependyma of the bovine SCO kept in culture; it caused the lysis of these cells when used together with complement. None of these properties were displayed by the antiserum raised against the integral proteins of the plasma membrane of the ciliated ependyma. This antiserum, however, immunostained the bovine ciliated ependyma neighboring the SCO. These results indicate that immunological surgery of the SCO in living animals may be possible to achieve.

Animals↗
PubMed1980

Studies on the presence of vasopressin, oxytocin and vasotocin in the pineal gland, subcommissural organ and fetal pituitary gland: failure to demonstrate vasotocin in mammals.

The demonstration of vasotocin in the mammalian pineal gland, subcommissural organ and fetal pituitary gland by bioassay has led to hypotheses regarding the function of this hormone in various reproductive processes. Preliminary examinations of the pineal gland and subcommissural organ with a specific radioimmunoassay failed to show vasotocin immunoreactivity. The presence of vasotocin, vasopressin and oxytocin in the pineal gland, subcommissural organ and fetal neurohypophysis was therefore investigated, using three specific radioimmunoassays. Frog and chicken pituitary glands were used to validate the vasotocin radioimmunoassay. Direct measurements in diluted homogenates of pituitary glands from frogs, chickens, mid-term fetal sheep and near-term fetal seals revealed the presence of vasotocin only in the frog and chicken pituitary glands, while vasopressin and oxytocin were found in the two fetal pituitary homogenates. Vasopressin and ocytocin were measured in homogenates of rat and bovine pineal glands and in preparations of the subcommissural organ of rats and rabbits after extraction with Vycor glass powder, but no specific vasotocin immunoreactivity was observed. These results indicate a discrepancy between the reported biological activity of vasotocin in the pineal gland, subcommissural organ and fetal pituitary gland and the immunoreactivity of this material, which can at present only be explained by the presence of a peptide which is structurally closely related to, but not identical with, vasotocin.

Animals↗
PubMed1985

Observations on organized areas of the endoplasmic reticulum, mitochondria, and ribosomes in ependymal cells of the subcommissural organ of Cebus, Saimiri and Callicebus (Platyrrhina, Primates).

The endoplasmic reticulum, the distribution of ribosomes attached to its membranes and the topographic relation of mitochondria have been studied in ependymal cells of the subcommissural organ of Cebus, Saimiri, and Callicebus. Occasionally, these organelles appear to be distinctly organized in restricted areas. They may be either irregularly arranged, formed into stacks, or organized into individualized corpuscules. The constituents of these organized areas are the same. Topographic relations with the GOLGI apparatus which would indicate a close interaction between these organelles, were not observed. The assemblage of substructures known to be involved in the synthesis of secretions of the subcommissural organ indicates a specific function of those areas.

Animals↗
PubMed2006

The secretory ependymal cells of the subcommissural organ: which role in hydrocephalus?

Ependyma in the central nervous system gives rise to several specialized cell types, including the secretory ependymal cells located in the subcommissural organ. These elongated cells show large cisternae in their cytoplasm, which are filled with material secreted into the cerebrospinal fluid and toward the leptomeningeal spaces. A specific secretion of the subcommissural organ was named SCO-spondin, regarding its marked homology with developmental proteins of the thrombospondin superfamily (presence of thrombospondin type 1 repeats). The ependymal cells of the subcommissural organ and SCO-spondin secretion are suspected to play a crucial role in cerebrospinal fluid flow and/or homeostasis. There is a close correlation between absence of the subcommissural organ and hydrocephalus in rat and mouse strains exhibiting congenital hydrocephalus, and in a number of mice transgenic for developmental genes. The ependymal cells of the subcommissural organ are under research as a key factor in several developmental processes of the central nervous system.

Animals↗
PubMed2000

The subcommissural organ of the frog Rana perezi is innervated by nerve fibres containing GABA.

The innervation of the frog subcommissural organ was studied by light-microscopic and ultrastructural immunocytochemistry using antisera against serotonin, noradrenaline, dopamine, gamma-aminobutyric acid (GABA), glutamic acid decarboxylase, different GABA receptor subunits and bovine Reissner's fibre material (AFRU). In the proximity of the organ, serotonin- and noradrenaline-containing fibres were rare whereas dopamine-immunoreactive fibres were more numerous. Many GABA- and glutamic acid decarboxylase-containing nerve fibres were found at the basal portion of the ependymal cells of the subcommissural organ. Under the electron microscope, these GABA-immunolabelled nerve endings appeared to establish axoglandular synapses with secretory ependymal cells of the subcommissural organ. In addition, the secretory ependymal cells expressed high amounts of the beta2-subunit of the GABA(A) receptor. Since GABA-immunoreactive neurons were present in the frog pineal organ proper and apparently contributed axons to the pineal tract, we suggest that at least part of the GABAergic fibres innervating the frog subcommissural organ could originate from the pineal organ.

Animals↗