Physiological response of bovine subcommissural organ to endothelin 1 and bradykinin.

The circumventricular organs (CVOs) regulate certain vegetative functions. Receptors for bradykinin (BDK) and endothelin (ET) have been found in some CVOs. The subcommissural organ (SCO) is a CVO expressing BDK-B2 receptors and secreting Reissner's fiber (RF) glycoproteins into the cerebrospinal fluid.

The subcommissural organ of the rat secretes Reissner's fiber glycoproteins and CSF-soluble proteins reaching the internal and external CSF compartments.

Background: The subcommissural organ (SCO) is a highly conserved brain gland present throughout the vertebrate phylum; it secretes glycoproteins into the cerebrospinal fluid (CSF), where they aggregate to form Reissner's fiber (RF). SCO-spondin is the major constituent protein of RF. Evidence exists that the SCO also secretes proteins that remain soluble in the CSF.

The destination of the aged, nonreleasable neurohypophyseal peptides stored in the neural lobe is associated to the remodeling of the neurosecretory axon.

The present investigation was designed to investigate the fate of the large pool of neurohypophyseal hormones that is never released into the blood. Normal Sprague-Dawley and taiep mutant rats were investigated under normal water balance, after dehydration and after dehydration-rehydration. Lectin histochemistry and light- and electron-microscopic immunocytochemistry using antibodies against vasopressin, oxytocin, and neurophysins used at low (1:1,000) and high (1:15,000) dilutions allowed to distinguish (1) recently packed immature granules, as those located in the perikaryon; (2) mature; and (3) aged granules.

Transcription of SCO-spondin in the subcommissural organ: evidence for down-regulation mediated by serotonin.

The subcommissural organ (SCO) is a brain gland located in the roof of the third ventricle that releases glycoproteins into the cerebrospinal fluid, where they form a structure known as Reissner's fiber (RF). On the basis of SCO-spondin sequence (the major RF glycoprotein) and experimental findings, the SCO has been implicated in central nervous system development; however, its function(s) after birth remain unclear. There is evidence suggesting that SCO activity in adult animals may be regulated by serotonin (5HT).

The floor plate cells from bovines express the mRNA encoding for SCO-spondin and its translation products.

The floor plate (FP) is a transient structure of the embryonic central nervous system (CNS) which plays a key role in development driving cell differentiation and patterning in the ventral neural tube. The fact that antisera raised against subcommissural organ (SCO) secretion immunostain FP cells and react with high-molecular-mass proteins in FP extracts, prompted us to investigate the expression of a SCO-related polypeptide in FP cells. RNA from bovine FP was analyzed by means of reverse transcriptase polymerase chain reaction (RT-PCR), using primers derived from the 3' end of SCO-spondin which revealed products of 233, 237, 519 and 783 bp.

The dispersed cell culture as model for functional studies of the subcommissural organ: preparation and characterization of the culture system.

The subcommissural organ (SCO) is an enigmatic secretory gland of the brain, which is believed to be derived from ependymal (glial) precursor cells. We here developed a dispersed cell culture system of the bovine SCO as an approach to functional analyses of this brain gland. Tissue of the bovine SCO obtained from the slaughterhouse was papain dissociated either directly after dissection or after preparation of SCO explants.

Vertebrate floor plate transiently expresses a compound recognized by antisera raised against subcommissural organ secretion.

Located along the ventral midline of the neural tube, the floor plate (FP) performs an essential role in central nervous system development, especially in the patterning of the ventral region of the neural tube and axonal guidance. Several studies have been directed to the identification of molecules mediating some of the functions of the FP. Most of the models proposed for floor plate actions involve contact-mediated- and/or gradients of diffusible-signals acting throughout the nervous tissue.

Organ culture of the bovine subcommissural organ: evidence for synthesis and release of the secretory material.

The subcommissural organ (SCO) is a brain circumventricular organ formed by ependymal and hypendymal secretory cells. It secretes glycoproteins into the cerebrospinal fluid of the third ventricle where they condense into a thread-like structure known as Reissner's fiber (RF). The present study was designed to investigate whether or not the bovine SCO continues to synthesize and release glycoproteins after a long-term culture.

Partial sequencing of Reissner's fiber glycoprotein I (RF-Gly I).

The bulk of the secretion of the subcommissural organ is formed by glycoproteins that appear to be derived from two precursor forms of 540 and 320 kDa. Upon release into the ventricle, these glycoproteins aggregate to form Reissner's fiber. We report the isolation of three cDNA clones from a cDNA library prepared from bovine subcommissural organ RNA, by using an anti-Reissner's fiber serum for immunoscreening.

Floor plate and the subcommissural organ are the source of secretory compounds of related nature: comparative immunocytochemical study.

The subcommissural organ of vertebrates secretes glycoproteins into the third ventricle that condense to form Reissner's fiber (RF). Antibodies raised against the bovine RF-glycoproteins reacted with the floor plate (FP) cells of two teleost (Oncorhynchus kisutch, Sparus aurata) and two amphibian (Xenopus laevis, Batrachyla taeniata) species. At the ultrastructural level, the immunoreactivity was confined to secretory granules, mainly concentrated at the apical cell pole.

Light- and electron-microscopic investigation of the rat subcommissural organ grafted under the kidney capsule, with particular reference to immunocytochemistry and lectin histochemistry.

There is increasing evidence that, in the rat, a serotonin-mediated neural input may have an inhibitory influence on the secretory activity of the subcommissural organ (SCO). In the present investigation the rat SCO was studied 7, 30 and 90 days after transplantation under the kidney capsule, an area devoid of local serotonin-containing nerves. The grafted tissue was examined by use of immunocytochemistry employing a series of primary antisera, lectin histochemistry and transmission electron microscopy.

Occurrence of an anterior spinal, cerebrospinal fluid-contacting, urotensin II neuronal system in various fish species.

The occurrence of an "extraurophyseal" system of immunoreactive-urotensin II (IR-UII) neurons was determined by immunocytochemical studies in the central nervous system of different fresh- and seawater species of fish. The following general elements were identified as forming part of this system: (a) a midsagittal column of IR-UII neurons located ventral to the central canal, with dendrite-like processes projecting into the cerebrospinal fluid (CSF); (b) a medial plexus of fine beaded IR-UII fibers located ventral to the column of cell bodies; (c) a bilateral or midsagittal, probably ascending, longitudinal bundle of IR-UII beaded fibers varying in location from the ventral to the lateral funiculus; (d) putative IR-UII fiber endings along the ventrolateral surface of the spinal cord; (e) IR-UII fiber distributions (probably terminal) in the ventral horns of the spinal cord and in several brain regions. The occurrence of this system in all fishes examined and the morphological features of this IR-UII system linking the central canal CSF to several CNS regions, as well as to the periphery of the spinal cord, point to an important role for this CSF-contacting anterior spinal IR-UII system in fish.

Pinealocytes immunoreactive with antisera against secretory glycoproteins of the subcommissural organ: a comparative study.

By means of light-microscopic immunocytochemistry two polyclonal antibodies (AFRU, ASO; see p. 470) directed against secretory glycoproteins of the subcommissural organ were shown to cross-react with cells in the pineal organ of lamprey larvae, coho salmon, a toad, two species of lizards, domestic fowl, albino rat and bovine (taxonomic details, see below). The AFRU-immunoreactive cells were identified as pinealocytes of the receptor line (pineal photoreceptors, modified photoreceptors or classical pinealocytes, respectively) either due to their characteristic structural features or by combining AFRU-immunoreaction with S-antigen and opsin immunocytochemistry in the same or adjacent sections.

Relationship between urotensin II- and somatostatin-immunoreactive spinal cord neurons of Catostomus commersoni and Oncorhynchus kisutch (Teleostei).

This immunocytochemical study describes the presence of separate immunoreactive (IR)-urotensin II (UII) and IR-somatostatin (SOM) systems in the spinal cord of two species of teleost fish. Both systems are arranged in a close spatial interrelationship in which IR-SOM fibres apparently innervate cerebrospinal fluid (CSF)-contacting IR-UII neurons. Specimens of Oncorhynchus kisutch also display CSF-contacting IR-SOM neurons located in the lateral ependymal walls of the central canal, in addition to CSF-contacting IR-UII neurons located ventrally.

Co-localization of the immunoreactivities of corticotropin-releasing factor and arginine vasotocin in the brain and pituitary system of the teleost Catostomus commersoni.

The peroxidase-antiperoxidase immunocytochemical procedure was used to study the distribution of ovine corticotropin-releasing factor (CRF) and arginine vasotocin (AVT) immunoreactivities sequentially in the same sections or in adjacent sections of the brain and pituitary of Catostomus commersoni. It was found that all CRF-immunoreactive (IR) neurons in the nucleus preopticus (NPO) also contained AVT immunoreactivity. Co-localization of both immunoreactivities was also observed in fibres forming the preoptic-pituitary tract and in the neurohypophyseal digitations, the IR-CRF and IR-AVT fibres projecting mainly to the neurointermediate lobe (NIL) of the pituitary.

The distribution of 'extraurophyseal' urotensin I-immunoreactivity in the central nervous system of Catostomus commersoni after urophysectomy.

The occurrence and distribution of the fish neuropeptide urotensin I-immunoreactive (IR-UI) perikarya and fibres was investigated by peroxidase-anti-peroxidase immunohistochemistry in paraffin and vibratome sections of the central nervous system of urophysectomized and control fishes. IR-UI neurones not described previously were found in the area ventralis telencephali pars dorsalis, in the area pretectalis and in two unidentified brainstem nuclei of control and urophysectomized fishes. In urophysectomized fishes a 4-fold increase in the number of parvocellular IR-UI neurons was observed in the nucleus lateralis tuberis, whereas no significant differences were seen in other IR-UI neuronal groups.

Extraurophyseal distribution of urotensin II immunoreactive neuronal perikarya and their processes.

The use of the unlabeled antibody enzyme method on serially adjacent sections permitted the demonstration of urotensin II (UII) and urotensin I (UI) immunoreactivities colocalized in most of the cells of the caudal neurosecretory system of Catostomus commersoni. The study of the upper regions of the central nervous system from the spinal cord anterior to the fifth preterminal vertebral region up to and including the brain stem revealed the presence of UII immunoreactivity in cerebrospinal fluid-contacting neurons, located ventral to the central canal along the entire length of the spinal cord and medulla. Beaded nerve fibers were observed projecting to the ventrolateral surface of the spinal cord and also forming a seemingly ascending immunoreactive-UII longitudinal bundle directed toward the brain.

Localization of urotensin I- and corticotropin-releasing factor-like immunoreactivity in the central nervous system of Catostomus commersoni.

The distribution of urotensin I (UI) and corticotropin-releasing factor (CRF) immunoreactive (IR) structures was studied in the central nervous system (CNS) of the white sucker using the peroxidase-antiperoxidase immunocytochemical procedure. The close sequence homology between both peptides resulted in a high degree of crossreactivity. This was resolved by saturating the antisera solutions with heterologous antigens and specificity tests were done by adding excess of homologous peptides.

The fish neuropeptide urotensin I: its physiology and pharmacology.

Significant structural and biological homologies between urotensin I (UI), ovine hypothalamic corticotropin releasing factor (oCRF) and the frog skin peptide sauvagine (SVG) have been investigated and compared in fishes and mammals. In mammals, urotensin and the related peptides exert uniquely selective mesenteric vasodilatation, oCRF having approximately equal to 4% the activity of the other two. All three peptides are equipotent in stimulation of ACTH secretion in the rat in vivo and in vitro.

Immunocytochemistry and ultrastructure of the neuropil located ventral to the rat supraoptic nucleus.

The neuropil located ventral to the SON was investigated by the use of immunoperoxidase staining for neurophysins, oxytocin and vasopressin, and electron microscopy. The study was performed in six groups of rats: 1) control; 2) infusion of isotonic saline into the CSF; 3) infusion of hypertonic saline into the CSF; 4) drinking hypertonic saline for 4 days; 5) same as group 4 but injection of colchicine into the CSF on second day of dehydration; 6) salt loading for 3 months. In the control rats the ventral neuropil contained a few immunoreactive processes, the general morphology of which was completely different from that of the neurosecretory axons emerging from the SON at its dorsal aspect.

Neurophysin pathways in the normal and hypophysectomized rat.

The hypothalamo-extrahypophyseal neurophysin pathways (HEH) and the three hypothalamic nuclei secreting neurophysins, the supraoptic (SON), paraventricular (PVN) and suprachiasmatic (SCN) nuclei, of normal and hypophysectomized rats were studied by application of the immunoperoxidase procedure. Eight well-defined HEH pathways were recognized. Their main sites of projection were: lateral septum and subfornical organ (1 and 2); tractus diagonalis (3); medial nucleus of the amygdala and lateral ventricle (4); nucleus periventricularis thalami, nucleus habenulae lateralis and periaqueductal gray (5); periaqueductal gray, pineal organ, collicular recess and subependymal region of the fourth ventral (6); dorsomedial nucleus and premammillary area (7); perimammillary region, corpus trapezoideum, ventral surface of medulla oblongata, nucleus tractus solitarii, nucleus commissuralis, substantia gelatinosa and formatio reticularis lateralis of the medulla oblongata and spinal cord (8).