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M F Belin

Publications and source records attributed to M F Belin.

At least 19 recordsLinked to original sources
PubMed1992

Somatotopic organization of tyrosine hydroxylase expression in the rat locus coeruleus: long term effect of RU24722.

Tyrosine hydroxylase (TH) tissue concentration was determined by immunostaining of tissue sections directly transferred onto nitrocellulose membranes in the restricted region of the noradrenergic perikarya of the locus coeruleus (LC) along its postero-anterior axis. TH containing cells were systematically counted on adjacent post fixed sections stained by immunohistochemistry. The absolute quantity of TH was estimated in each section and was found to be linearly related to the number of TH immuno-positive cells found in the adjacent section. The ratio between these two parameters was thus used as an index of the cellular concentration of TH in noradrenergic cells. In the LC of control rats, the TH cellular concentration was lower (-39%) in the anterior than in the posterior half of the structure. Three days after an injection of 20 mg/kg of RU24722, an eburnamine derivative known to increase the quantity of TH in the LC, increases in quantities of TH were found in both portions of the LC. Moreover in the posterior LC the increase in the amount of TH resulted from a significant increase in the number of TH-immunopositive cells. In the anterior part, however, it was primarily the result of a significant increase in TH cellular concentration. Throughout the LC there was an increase in the cellular concentration of TH which was inversely proportional to the concentrations found in control animals. TH mRNA content was measured by a quantitative in situ hybridization in sections of both the posterior and anterior LC one day after a single injection of RU24722 at the same dose. The quantity of TH mRNA was significantly increased in both parts. The number of TH mRNA-expressing neurons also increased, especially in the anterior LC. Thus the effects at the level of TH protein and TH mRNA were strikingly parallel though increase in TH protein occurred later than the increase in the TH mRNA. These results suggest that in the rat LC: (1) there is a significant population of 'sleeping cells' in which TH expression is either inactivated or, at a low level of activation; (2) TH cellular concentration could exert a retrocontrol on its own expression in cells of the LC that contained TH and (3) TH expression appears to be regulated by different selective mechanisms in these two different subpopulations of noradrenergic cells within the LC.

Animals↗
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↗
PubMed1992

[Autoantibodies in paraneoplastic polioencephalomyelitis: 8 cases].

Antibodies directed against the central nervous system were looked for by indirect immunohistochemistry in the sera of 8 patients with paraneoplastic neurological syndrome (group 1), 21 cancer patients without neurological signs, 23 patients with miscellaneous neurological diseases and 63 normal subjects (groups 2 to 4). Four patients in group 1 had very high titres of antibodies. In 2 patients with small-cell lung carcinoma associated with sensory neuropathy the antibody recognized the cytoplasm and nucleus of all neurons. A 37 Kd protein was recognized by Western blot. A woman with cancer of the ovary and cerebellar syndrome exhibited an antibody against Purkinje's cell cytoplasm with a band of about 50-55 Kd at Western blot. In a woman with chronic uveitis and cerebellar atrophy with disappearance of Purkinje's cells the antibody (in blood and CSF) recognized certain layers of the retina as well as glial cells and cells present in the subependymal areas of the brain. Two bands of 46 and 59 Kd were revealed by Western blot. Immunoglobulins were detected in the cytoplasm of white matter cells in the cerebellum and brain stem. Among the other groups, one patient with lung cancer had a moderate titre of neuronal antinuclear antibody. The Western blot test was negative. The relevance of these antibodies for the diagnosis and treatment is discussed.

Aged↗
PubMed1992

Paradoxical sleep deprivation increases glutamine synthetase in rat brain.

The modifications of glutamine synthetase (GS) level, an enzyme mainly located in astrocytes, were investigated in rat after paradoxical sleep deprivation and during recovery. An immunotitration method was used to evaluate the relative level of GS in brain tissue. At the end of a 24 hrs. paradoxical sleep deprivation, a significant increase in GS level was observed both in the frontoparietal cortex and the locus coeruleus area. 4 hrs. later, during recovery, the GS level returned to control level in the cortex but was lower in the locus coeruleus area.

Animals↗
PubMed1991

Developmental neuron-glia interaction: role of the serotonin innervation upon the onset of GABA uptake into the ependymocytes of the rat subcommissural organ.

The subcommissural organ (SCO) of the rat allows the analysis of neuron-glia interactions, in vivo, during the maturation of the brain. The SCO contains a single glial cell type which receives a homogeneous serotonin (5-HT) innervation. The onset of gamma-aminobutyric acid (GABA) uptake transport into the SCO ependymocytes is dependent on the 5-HT innervation since destruction of this innervation, at birth, or transplantation of newborn rat SCO ependymocytes to the fourth ventricle of adult host rats prevented the appearance of [3H]GABA uptake as visualized by autoradiography.

Animals↗
PubMed1991

Primary dissociated cell culture of embryonic rat metencephalon: presence of GABA in serotonergic neurons.

This study was performed to determine whether neurons, where gamma-aminobutyric acid (GABA) and serotonin (5-HT) coexist, represent neuronal entities which can survive in vitro. In dissociated cultures from 18-day-old embryonic rat metencephalon, it was possible to develop glial and neuronal cells. Among the neurons, some of them, which contain glutamate decarboxylase or are capable of accumulating [3H]GABA are GABAergic; others, containing tryptophan hydroxylase or 5-HT are serotoninergic. By combining radioautography and immunocytochemistry, it was possible to observe neurons where 5-HT and GABA coexist. Cultures might be a suitable model to study the functioning (release or synthesis of both neurotransmitters) of neurons where two classical neurotransmitters coexist.

Animals↗
PubMed1991

Developmental expression of glial markers in ependymocytes of the rat subcommissural organ: role of the environment.

The rat subcommissural organ (SCO), principally composed of modified ependymocytes (a type of glial cell), is a suitable model for the in vivo study of glial differentiation. An immunohistochemical study of the ontogenesis of rat SCO-ependymocytes from embryonic day 13 to postnatal day 10 shows that these cells express transitory glial fibrillary acidic protein (GFAP) from embryonic day 19 until postnatal day 3. However, S100 protein (S100) is never expressed in the SCO-cells, contrasting with the ventricle-lining cells of the third ventricle, which contain S100 as early as embryonic day 17. Environmental factors could be responsible for the repression of GFAP and S100 in adult rats, because GFAP and S100 are observed in ependymocytes of SCO 3 months after being grafted from newborn rat into the fourth ventricle of an adult rat. Neuronal factors might be involved in the control of the expression of S100, since after the destruction of serotonin innervation by neurotoxin at birth, S100 can be observed in some SCO-ependymocytes of adult rats. On the other hand, GFAP expression is apparently not affected by serotonin denervation, suggesting the existence of several factors involved in the differentiation of SCO-cells.

5,7-Dihydroxytryptamine↗
PubMed1991

A comparative immunocytochemical and immunochemical analysis of glycoproteins synthesized in the bovine subcommissural organ.

To extend our previous immunochemical investigations in the chick embryo (Karoumi et al., 1990 b), we raised antibodies in the rabbit against crude extracts of the subcommissural organ (SCO) of the bovine. The antiserum labeled A99 was absorbed by crude brain extracts and its specificity was tested by different techniques. Comparison of crude SCO and cerebral hemispheres supernatants after immunoblotting allow to identify specific 98, 60, 52, 42, 38, and 32 kDa polypeptides in the SCO profile. Immunoaffinity chromatography on A99 immunoadsorbent of crude SCO, cerebral hemispheres (CH) and classical ependyma (CE) supernatants was followed by electrophoretical analysis and electrotransfer. Concanavalin A (Con A) and wheat germ agglutinin (WGA) labeling procedures demonstrated the presence of numerous glycopeptides specific of crude SCO supernatants and having an apparent molecular weight ranging from 240 to 50 kDa. In the CH-eluted fraction, 50 and 52 kDa glycopeptides were revealed by ConA and WGA, whereas in the CE-immunopurified fraction no band was visualized. The similarity of the chick embryo and bovine electrophoretic pattern corresponding to the SCO eluted fractions speaks in favour of a high degree of conservation of the SCO secretory material and an evolutionary stability of the antigens recognized by A99IgG.

Animals↗
PubMed1991

[Demonstration of viral proteins and RNA in hypothalamus of mice infected by canine distemper virus].

There are a number of reports suggesting that neurological disorders may be due to infectious agents, such as viruses. In order to study the role of viruses on cellular plasticity in the central nervous system, we established a model of virus infection in the mouse. Inoculation of mouse with canine distemper virus (CDV) led to an acute encephalitis, late neurological disorders and an obesity syndrome. To analyse the role of viral replication on the development of this syndrome we studied the cerebral distribution of viral products during the course of infection. Viral proteins and RNA accumulated in mouse brain from the 9th day to the 6th week post-inoculation, particularly in hypothalamus, a cerebral structure implicated in obesity. Such selective viral tropism may explain some of the unexpected features of viral-induced disorders.

Animals↗
PubMed1990

Neuron-glia interactions: effect of serotonin on the astroglial expression of GFAP and of its encoding message.

The trophic effect of serotonin on the glial fibrillary acidic protein (GFAP) expression was investigated in rat brainstem astrocytes in primary culture. GFAP immunolabelling decreased and gliofilaments appeared localized in the cytoplasm periphery. GFAP protein level decreased in parallel with a decrease in its encoding message. Serotonin may act as an inhibitor of GFAP expression either on the transcription or on the stability of the GFAP-mRNA.

Animals↗
PubMed1990

Glycoprotein synthesis in the subcommissural organ of the chick embryo. II. An immunochemical study.

In the chick embryo, A74 immunoaffinity chromatography allowed to purify specific glycoproteins relevant to the SCO ventricular secretory process. The eluted fractions of the subcommissural organ (SCO), the cerebral hemispheres (CH) and the medulla oblongata (MO) were compared using the Concanavalin A (Con A) and wheat germ agglutinin (WGA) staining procedures after western-blotting. Analysis of the optical density of the reactive bands allowed to estimate the relative concentration of the various glycopeptides in the eluted fractions. In the SCO-eluted fractions at least ten Con A-positive glycopeptides were identified, their apparent molecular weight ranging from 240 to 42 kD. Only three of these appeared to be WGA-positive (98, 88, and 52 kD). In the CH-eluted fractions only a 52 kD Con A- and WGA-positive glycopeptide was revealed, while in the MO-eluted fractions a 32 kD glycopeptide was also Con A- and WGA-positive. These results are discussed in regard to the known biosynthesis pathway of complex type glycoproteins.

Animals↗
PubMed1990

Glycoprotein synthesis in the subcommissural organ of the chick embryo. I. An ontogenetical study using specific antibodies.

Antibodies were raised in rabbit against crude subcommissural organ (SCO) extract of 19 day old chick embryos. After absorption with crude brain extract, the IgG fraction was purified by ion exchange chromatography. The specificity of the antibodies was controlled by immunostaining and by a competition test between lectins (Concanavalin A-Con A- and wheat germ agglutinin-WGA-) and antibodies (A74 IgG). Using A74 IgG, some ependymal cells containing immunoreactive material (IRM) could be detected in the SCO anlage at 4 days of incubation. During the following stages (5 to 12 days), the immunostaining extended caudal-ward 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). Secretion of IRM into the ventricular cavity, contributing to the formation of Reissner's fiber (RF) occurred during the 7th day of incubation. The formation of RF was examined at different levels of the spinal cord using A74 IgG, WGA and aldehyde fuchsin (AF) staining. The appearance of SCO specific glycoproteins was observed at 11 days in the central canal but the presence of a non-immunoreactive material at 10 days suggests that the formation of RF probably happens inside a guidance material.

Animals↗
PubMed1990

[Histogenesis of subependymal glioma in Bourneville's tuberous sclerosis].

The phenotypic characteristics of 7 subependymal giant cell astrocytomas (GSECG) (6 of these being associated with tuberous sclerosis) are studied using morphological and immunohistochemical methods with antiserums against vimentine, glial fibrillary acid protein (GFA), S100 protein, and neurofilaments. The glycoproteic secretion of the tumor cells was also analyzed after exposure to Concanavalin A (CON A) by a direct fluorescent method. Our results suggest that some GSECG originate from specialized ependyma (circum-ventricular organs). They have the same location (foramen of Monro), present some common ultrastructural features (cytoplasm with lumen containing cilia), are positive with certain immunohistochemical markers (staining with S100 protein in 4 cases, with vimentin in 3 cases) and show a strong glycoproteic secretion (positive with CON A). Therefore, some GSECG might be considered hamartomas of specialized ependyma, with a reduced evolutivity potential.

Adolescent↗
PubMed1989

Neuronal control of [3H]GABA uptake in the ependymocytes of the subcommissural organ: an in vivo model of neuron-glia interaction.

The rat subcommissural organ (SCO) is a particular but adequate paradigm for the approach, in vivo, to some aspects of neuron-glia interaction in gamma-aminobutyric acid (GABA) uptake. The rat SCO ependymocytes (the main component of this structure lying at the junction of the aqueduct and the third ventricle) accumulate [3H]GABA by a highly specific uptake mechanism and receive a serotoninergic input forming typical synaptic contacts. It seems that there is a correlation between the capacity of the rat SCO ependymocytes to take up [3H]GABA and the presence of a serotonin (5-HT) innervation. Indeed, in the newborn rat, no uptake of [3H]GABA was observed before the onset of this innervation and the increased [3H]GABA accumulation in the SCO was correlated with the appearance of the 5-HT terminals in the SCO. Moreover, in the mouse, whose SCO is devoid of a 5-HT innervation, no accumulation of [3H]GABA was observed in the SCO ependymocytes. Thus, the 5-HT innervation could be involved directly or indirectly in the onset of the GABA uptake carriers. On the other hand, in adult rats parachlorophenylalanine (pCPA) treatment decreased the 5-HT content of the SCO, and increased [3H]GABA accumulation; such an augmentation was not observed when rats were treated with pCPA plus 5-hydroxytryptophan to restore the 5-HT content. However, an increase in 5-HT content of the SCO by pargyline treatment appeared to have no effect on [3H]GABA uptake. Control of GABA uptake activity by 5-HT in the SCO ependymocytes could be an interesting model for the study of a possible interaction between amino-acids and other neurotransmitters by terminating their action in the extracellular space.

Animals↗
PubMed1989

Comparative marker analysis of the ependymocytes of the subcommissural organ in four different mammalian species.

The subcommissural organ (SCO), classified as one of the circumventricular organs, is composed mainly of modified ependymal cells, attributable to a glial lineage. Nevertheless, in the rat, these cells do not possess glial markers such as glial fibrillary acidic protein (GFAP), protein S100, or the enzyme glutamine synthetase (GS). They receive a synaptic 5-HT input and show pharmacological properties for uptake of GABA resembling the uptake mechanism of neurons. In this study, we examine the phenotype of several mammalian SCO (cat, mouse, rabbit) and compare them with the corresponding features of the rat SCO. In all these species, the SCO ependymocytes possess vimentin as an intermediate filament, but never express GFAP or neurofilament proteins. They do not contain GS as do glial cells involved in GABA metabolism, and when they contain protein S100 (rabbit, mouse), its rate is low in comparison to classical glial or ependymal cells. Thus, these ependymocytes display characteristics that differentiate them from other types of glial cells (astrocytes, epithelial ependymocytes and tanycytes). Striking interspecies differences in the capacity of SCO-ependymocytes for uptake of GABA might be related to their innervation and suggest a species-dependent plasticity in their function.

Animals↗
PubMed1987

Immunohistochemistry of tryptophan hydroxylase in the rat brain.

An antiserum raised against tryptophan tetrahydropterine oxygen oxidoreductase was used to examine in rat brain the immunohistochemical localization of this rate-limiting enzyme catalysing the biosynthesis of serotonin. Tryptophan tetrahydropterine oxygen oxidoreductase was detected in numerous nerve cell bodies, proximal dendrites and axon varicosities or terminals corresponding to those of serotonin neurons as judged by their anatomical distribution and concomitant immunoreactivity to an antiserum against serotonin. In hypothalamus, a serotonin-containing nerve cell group previously visualized in the pars ventralis of the nucleus dorsomedialis by radioautography after serotonin uptake, and by serotonin immunohistochemistry after tryptamine loading, remained tryptophan tetrahydropterine oxygen oxidoreductase-unreactive even in rats treated with colchicine. On the other hand, a small group of tryptophan tetrahydropterine oxygen oxidoreductase-positive cells was identified in the rostrolateral portion of nucleus dorsomedialis, which could play a part in the intrinsic serotonin innervation of hypothalamus. There was no overlap between tryptophan tetrahydropterine oxygen oxidoreductase immunostaining and the cellular distribution of N-acetyl serotonin as reported in earlier studies. It is therefore likely that the synthesis of N-acetyl serotonin from tryptophan does not take place in N-acetyl serotonin-containing neurons.

Animals↗