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Biomedical subjects

M Fèvre-Montange

Publications and source records attributed to M Fèvre-Montange.

18 recordsLinked to original sources
PubMed2004

Localization of transforming growth factors, TGFbeta1 and TGFbeta3, in hypothalamic magnocellular neurones and the neurohypophysis.

The distribution of transforming growth factor beta (TGFbeta) in the rat and human hypothalamus and neurohypophysis was investigated by immunocytochemical techniques using rabbit polyclonal antisera against TGFbeta(1) and TGFbeta(3). Colocalization of TGFbeta(1) or TGFbeta(3) and arginine vasopressin (AVP) in the rat hypothalamus was studied by double immunolabelling in light microscopy, while their subcellular localization in the rat neurohypophysis was investigated by immunoelectron microscopy. TGFbeta(1) and TGFbeta(3) immunoreactivity was demonstrated in the cell bodies and processes of neurones in the supraoptic nucleus (SON) and paraventricular nucleus (PVN). The TGFbeta-immunoreactive cells were more numerous in the SON compared to the PVN. TGFbeta/AVP double-labelled cells were seen in both nuclei, but some neurones in the SON were labelled for TGFbeta(1) or TGFbeta(3), although not for AVP. In the rat and human neurohypophysis, TGFbeta(3) immunolabelling was more diffuse and stronger than TGFbeta(1) immunolabelling. TGFbeta(1) expression was seen in axonal vesicles and in neurosecretory granules of the axonal endings, while TGFbeta(3) was observed in axonal fibres. Colocalization of TGFbeta(3) or TGFbeta(1) and AVP was observed in some neurosecretory granules, but many were either single-labelled for TGFbeta or AVP or unlabelled. Our results demonstrate, for the first time, the colocalization of TGFbeta and neurohypophysial hormones in magnocellular neurones. We suggest that TGFbeta secreted by the neurohypophysis regulates the proliferation and secretion of certain anterior pituitary cells.

Animals↗
PubMed2002

Establishment of human tumoral ependymal cell lines and coculture with tubular-like human endothelial cells.

Ependymomas, rare neoplasms of the central nervous system, occur predominantly in children. They are highly vascularized, and histological findings show many perivascular rosettes of tumoral cells radially organized around capillaries. Treatment of ependymomas relies on surgery combined with radio- or chemotherapy, but the efficiency of chemotherapy is limited, probably because of their multidrug resistance (MDR) phenotype. Progress in the therapy of these neoplasms is dramatically limited by the absence of cell line models. We established conditions for the long-term culture of human tumoral ependymocytes and their 3D coculture in Matrigel with endothelial cells. Histological, immunological, and ultrastructural studies showed that the morphological features (microvilli, cilia, and caveolae) of these cultured cells were similar to those of the tumor in vivo. The cells expressed potential oncological markers related to the immature state of tumoral cells (nestin and Notch-1), their tumorigenicity [caveolae and epidermal growth factor-receptor (EGF-R)], or the MDR phenotype [P-glycoprotein (P-gp)]. The expression of P-gp, EGF-R, and caveolin-1 by these tumoral ependymocytes could be useful in studies on new drugs. This coculture model might represent a new powerful tool to study new therapeutic delivery strategies in tumoral cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Postnatal secretion of the subcommissural organ of the Meriones shawi: control of serotonin innervation.

The postnatal development of the subcommissural organ (SCO) glycoprotein secretion in form of Reissner's fiber and the putative control of the serotonin innervation upon the SCO activity were examined by immunohistochemistry in the semi-desert rodent, Meriones shawi. Abundant SCO secretory material and numerous serotoninergic fibers reaching the SCO were observed in newborns meriones. An increase of both secretory material and serotonin fibres density inside the SCO was observed during postnatal period and into adulthood. Neurotoxic destruction with 5,7-dihydroxytryptamine of the SCO serotonin input in the adult or the inhibition of serotonin synthesis by para-chlorophenylalanine at different postnatal ages, resulted in a decrease of the intensity of SCO Reissner's fiber immunolabelling suggesting a reduction in the SCO secretory material. This result might reflect either an inhibition of the synthesis or a stimulation of release of secretory material. These data suggest that serotonin innervation could be precociously involved in the regulation of the merione SCO secretion.

Age Factors↗
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↗
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

Pineal parenchymal tumors: a correlation of histological features with prognosis in 66 cases.

The WHO classification of CNS tumors divides pineal parenchymal tumors (PPT) into pineocytoma (PC), pineoblastoma (PB) and mixed pineocytoma-pineoblastoma or PPT with intermediate differentiation. The reported incidence of mixed/intermediate PPT varies and this may reflect the difficulty in classifying tumors of this type. In an attempt to overcome the problem of the classification of PPT with intermediate differentiation, we describe the relationship between histological features and patient survival in a large cooperative series of 66 PPT from 12 neurosurgical centres. All tumors were studied with both light microscopy and immunohistochemically using antibodies against glial markers or neural/neuroendocrine markers. Our series included 11 PC, 39 mixed/intermediate PPT and 16 PB. A number of mitoses greater than 6 and the presence of necrosis were associated with a poorer outcome, while positive immunostaining for neurofilaments was associated with a better survival. We propose a new prognostic grading of 4 grades, grade I for PC, grade II for PPT with fewer than 6 mitoses and positive immunolabelling for neurofilaments, grade III for PPT with either 6 or more than 6 mitoses or fewer than 6 mitoses but without immunostaining for neurofilaments and grade IV for PB.

Adolescent↗
PubMed2000

[Practical recommendations for management of the biopsy in an expansive intra-cerebral process].

Diagnosis of an intracerebral mass requires a good collaboration between clinicians and pathologists. Different techniques may be necessary. The interest of cytological preparations and immunohistochemistry is reported. The main characteristic features of cerebral tumors are described and the differential diagnosis with reactive and inflammatory masses simulating neoplasia is discussed.

Biopsy↗
PubMed1998

Immunohistochemical, ultrastructural, biochemical and in vitro studies of a pineocytoma.

Using both tumor specimen and cultured tumor cells, we have studied the differentiation of a pineocytoma by light and electron microscopy (EM) and immunohistochemical demonstration of glial, neuronal and neuroendocrine markers. Only interstitial cells were labeled with anti-glial fibrillary acidic protein and anti-S100 protein antibodies. Synaptophysin, neurofilaments and tau labeling was found in cells forming the pineocytomatous rosettes. Some cells also bound the anti-tryptophan hydroxylase antibody (TPOH), but no staining was seen after application of anti-chromogranin A or S-antigen antibodies. EM provided evidence for neurosensory differentiation demonstrating the presence of vesicle-crowned rodlets, cilia (9+0) and fibrous filaments. In culture, tumor cells proliferated slowly and showed positive immunolabeling for vimentin and TPOH. Expression of mRNA coding for TPOH, serotonin N-acetyltransferase, hydroxyindole-O-methyl-transferase and c-myc was found in the tumor using reverse transcriptase-polymerase chain reaction. These results demonstrate neuronal differentiation of this pineocytoma and suggest that the neoplastic pineal cells are capable of synthesizing serotonin and melatonin.

Acetylserotonin O-Methyltransferase↗
PubMed1997

Tryptophan hydroxylase mRNAs analysis by RT-PCR: preliminary report on the effect of noradrenaline in the neonatal rat pineal gland.

The levels of mRNAs coding for tryptophan hydroxylase (TPOH), the first enzyme in melatonin synthesis, have been investigated by quantitative reverse transcription of RNA, followed by polymerase chain reaction (RT-PCR), after stimulation of neonatal pineal organ cultures with Noradrenaline (NA). TPOH mRNAs were specifically amplified from various adult tissues, namely the pineal gland, raphe, retina, and kidney, but not the lung. PCR signals for TPOH were detected in the neonatal pineal gland in the absence of stimulation. Stimulation of neonatal pineal organ culture with 0.1 microM NA resulted in a significant increase (x2.5) in expression of TPOH mRNAs, whereas higher doses (1 and 10 microM) had no effect. All concentrations of NA enhanced melatonin secretion. Our results suggest that the level of TPOH mRNAs can be controlled by NA and that this effect might be implicated in the gene level regulation of the daily enzyme rhythm in the rat pineal gland.

Animals↗
PubMed1997

Evidence for tryptophan hydroxylase and hydroxy-indol-O-methyl-transferase mRNAs in human blood platelets.

Human blood platelets were tested for the presence of mRNAs coding for tryptophan hydroxylase (TPOH) and hydroxy-indol-o-methyl-transferase (HIOMT). Total RNA was extracted from platelets (12.9 +/- 3.3 mg RNA/100 ml blood, mean +/- SEM of 6 preparations) and cDNA synthesized by reverse transcription using random hexamers, oligo-dT or TPOH- or HIOMT-specific primers, designed to amplify a 254 bp fragment for TPOH and a 301 bp fragment for HIOMT. Positive controls were performed using RNA extracted from human normal or tumoral pineal glands. The PCR products were analyzed by gel electrophoresis, transferred to a nylon membrane and hybridized with a 32P-labeled internal probe. When random hexamers, oligo-dT or specific primers were used for reverse transcription, amplification products of the predicted sizes were detectable following electrophoresis in the case of pineal glands and following transfer and hybridization in the case of platelets. These results show TPOH and HIOMT mRNAs to be present in human blood and support the hypothesis that serotonin and melatonin may be synthesized in blood and, more particularly, in platelets.

Acetylserotonin O-Methyltransferase↗
PubMed1996

Nycthemeral expression of tryptophan hydroxylase mRNAs in the rat pineal gland.

The expression of mRNAs coding for tryptophan hydroxylase (TPOH), the first enzyme involved in melatonin synthesis, has been studied in the rat adult pineal gland at four different circadian time points by in-situ hybridization using an oligonucleotide probe. TPOH mRNAs were detected at all chosen time-points. The lowest level was seen at 13:00 h. Quantification of the hybridization signals demonstrated a significant increase in expression (+16.5%) between 13:00 h and 19:30 h, with the values at 23:30 h and 09:00 h being similar to that of 19:30 h. These results coincide with the nycthemeral rhythm of TPOH activity. Day/night rhythms in the rat pineal gland are controlled by noradrenaline release at lights-off, which results in an increase in cAMP levels and in gene activation. This study suggests that the TPOH gene might be one such gene whose activation is stimulated in this way.

Animals↗
PubMed1995

Developmental expression of tryptophan hydroxylase mRNAs in the rat pineal gland: an in situ hybridization study.

The expression of messenger RNAs encoding for tryptophan hydroxylase (TPOH), the first enzyme involved in serotonin and melatonin synthesis, has been investigated by in situ hybridization during the development of the rat pineal gland. TPOH mRNAs were detected as early as the twentieth day of gestation (E20) in the rat embryo before any nerve ending was observed in the pineal gland. After birth, their expression increased strongly, and attained a plateau during the second week. This coincides with the setting up of sympathetic innervation. From day 17 (D17), the TPOH mRNA expression diminished. These results indicate that noradrenergic innervation is not involved in the initiation of rat pinealocyte differentiation, but might modulate cell maturation. This study showed the existence of three types of cells arranged in patches in the young rat pineal gland (D6): regions in which cells expressed TPOH mRNAs, regions in which cells expressed vimentin, an intermediate filament protein present in the cytoskeleton of immature cells, and regions in which both TPOH mRNAs and vimentin are expressed. In older rat pineal gland (D20), almost all cells express TPOH mRNAs, and some cells still express vimentin. This suggests that all cells do not reach the same level of differentiation at the same time in the rat pineal gland.

Animals↗
PubMed1994

Structural and ultrastructural characteristics of human pineal gland, and pineal parenchymal tumors.

We have studied 20 pineal parenchymal tumors (PPT) and 4 normal or cystic pineal glands both by light and electron microscopy and immunohistochemistry with antibodies against glial markers [glial fibrillary acidic protein (GFAP) and protein S-100] or neural/neuroendocrine markers [neurofilaments (NF), synaptophysin and chromogranin A]. Light microscopy revealed the cellular organization of pinealocytes in the normal gland and in different morphological types of pineal tumors (typical pineocytomas, PPT with intermediate differentiation, mixed PPT exhibiting elements of both pineocytoma and pineoblastoma and pineoblastomas). Immunohistochemistry showed the presence of GFAP and protein S-100 in interstitial cells in non-neoplastic pineal gland. Cell processes were labeled with anti-synaptophysin and anti-NF antibodies. No immunoreactivity was found for chromogranin A in non-neoplastic pineal gland. In pineocytomas, GFAP and protein S-100 were observed in interstitial cells. Synaptophysin and NF were present in the large rosettes of pineocytomas. Synaptophysin, NF and chromogranin A were present in pineocytomas with a lobular arrangement of cells. Anti-chromogranin A immunoreactivity was also seen in lobular areas of some PPT with intermediate differentiation. Analysis of normal human pineal gland by electron microscopy showed the presence of vesicle-crowned rodlets (VCR or synaptic ribbons), fibrous filaments (F), paired twisted filaments but few dense-core vesicles (DCV) in normal pinealocytes. Tumoral pineal cells appeared to differentiate either towards a neurosensory pathway characterized by the presence of sensory cells elements (VCR and F), or towards a neuroendocrine pathway, with the occurrence of many DCV. Immunogold labeling demonstrated the presence of chromogranin A in neurosecretory granules.

Adolescent↗
PubMed1994

Effects of an acute immobilization stress upon proopiomelanocortin (POMC) mRNA levels in the mediobasal hypothalamus: a quantitative in situ hybridization study.

The aim of this study was to examine by quantitative in situ hybridization the effects of an acute stress on the expression of the POMC gene in the mediobasal hypothalamus (MBH) of the rat. In control animals, the highest levels of POMC mRNA were observed in the posterior periventricular region of the MBH. Lower levels were found in the anterior and posterior arcuate nucleus. At the end of a one hour immobilization, a small decrease (-8%) was observed in the periventricular region only. Four hours after the end of immobilization, increases in POMC mRNA levels were detected in the anterior part (7%), in the posterior part (25%) and in the periventricular region (13%) of the MBH. These results suggest that MBH POMC-derived peptides might be an important component in the central response to stress.

Analysis of Variance↗
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↗
PubMed1990

Ultrastructural localization of oxytocin mRNA in the rat hypothalamus by in situ hybridization using a synthetic oligonucleotide.

In situ hybridization (ISH) was used to study at the electron microscope level, the subcellular localization of oxytocin (OT) mRNA in the rat hypothalamic magnocellular neurons. Rat brains were fixed with paraformaldehyde and glutaraldehyde and vibratome slices were incubated with a 25-base synthetic oligonucleotide complementary to OT mRNA and labelled at the 3'-end with [3H]dCTP. Hybridized slices were embedded in Epon after post-fixation with osmium tetroxide and cut into ultrathin sections that were processed for ultrastructural radioautography. OT mRNA was observed in magnocellular neurons of supra-optic and paraventricular nuclei in the vibratome sections. On ultrathin sections, the cytological preservation appeared to be satisfactory. Except for a few silver grains over the nucleus, sometimes close to its membrane, most grains were localized over the cytoplasm of some magnocellular neurons, where they frequently overlapped the endoplasmic reticulum. To decrease exposure time, ISH was also performed with OT probes labelled with a long tritiated tail. In this case, clusters of silver grains occurred over the cell nuclei not only in magnocellular neurons but also in non-secretory neurons and even in glial cells. However, an excess of poly C added to the hybridization buffer strongly decreased this non-cytoplasmic labelling. In conclusion, the results obtained with the short-tailed oligonucleotides demonstrate that these synthetic oligonucleotides have possible applications for the ultrastructural localization of mRNAs and constitute a powerful tool for the dynamic study of cellular mRNA processing in several physiological and experimental conditions.

Animals↗
PubMed1985

Effect of indolamines on beta-endorphin release by rat anterior pituitary cells.

The effect of indolamine derivatives on beta-endorphin (beta-end) release has been studied in vitro using rat anterior pituitary cells. Incubation of primary cultures for 2 h with 100 nmol/l of melatonin, serotonin or 5-methoxytryptamine significantly increased the beta-end release in response to 20 nmol/l of ovine corticotropin-releasing factor (oCRF). Incubation of the cultures with 100 nmol/l of L-tryptophan, 5-hydroxy-L-tryptophan, 5-hydroxytryptophol or 5-methoxytryptophol had no effect on basal or CRF-induced beta-end release. The effect of serotonin and melatonin was further tested in a superfusion system of dispersed rat anterior pituitary cells. Superfusion with oCRF (200 nmol/l) for 4 min elicited an immediate rapid increase in beta-end release which lasted 30-40 min. Simultaneous superfusion with melatonin (1 mumol/l) or serotonin (1 mumol/l) significantly increased the effect of oCRF pulses on beta-end release. We conclude that melatonin and serotonin are able to act directly on anterior pituitary cells to potentiate the effect of oCRF on beta-end release.

5-Hydroxytryptophan↗