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G Vincendon

Publications and source records attributed to G Vincendon.

At least 19 recordsLinked to original sources
PubMed2000

7beta-hydroxysterol is cytotoxic to neonatal rat astrocytes in primary culture when cAMP levels are increased.

We have shown previously that 7beta-hydroxycholesterol (7betaOHCH) and 7beta-hydroxycholesteryl-3-oleate (7betaOHCH- 3-OL) are potent inhibitors of lesion-induced astrogliosis in the rat cortex or spinal cord; these substances reduce reactive astrocyte proliferation and hypertrophy. In this study, we employed cultured newborn rat astrocytes with increased cAMP levels as an in vitro model of reactive astrocytes. Treatment with either dibutyryl-cAMP (dbcAMP) or isoproterenol resulted in morphologic differentiation of astrocytes which became fibrous. Concomitant incubation with 30 microM 7betaOHCH and dbcAMP (or isoproterenol) provoked the cells to retract and was cytotoxic. When the beta-adrenergic receptor-mediated cAMP increase was abolished by propranolol, the 7betaOHCH cytotoxicity was inhibited. Immunocytochemical labelling for glial fibrillary acidic protein (GFAP) and beta-tubulin and electron microscopy suggested that intermediate filament and microtubular organizations were modified by 7betaOHCH. Analysis of the activity of cAMP-dependent protein kinase (PKA) in astrocytes treated with dbcAMP and 7betaOHCH showed a rapid and marked inhibition of the phosphotransferase activity which lasted for 24 hr. We suggest that this culture system provides an experimental system to study the molecular mechanisms involved in the effect of oxysterols on astrocytic hypertrophy. The cytotoxicity of 7betaOHCH seems to be mediated by inhibition of PKA, which phosphorylates intermediate filaments and the transcription factor cyclic AMP responsive element binding.

Adrenergic beta-Agonists↗
PubMed1998

Thyroid hormone receptor isoforms are sequentially expressed in oligodendrocyte lineage cells during rat cerebral development.

In the mammalian brain, thyroid hormones regulate myelination. Their actions are mediated by interactions with nuclear receptors that function as ligand-regulated transcription factors. Two genes, alpha and beta, encode different isoforms, of which only the beta and alpha1 isoforms are authentic nuclear triiodothyronine (T3)-receptors (NT3R). In agreement with the important role of T3 on myelination and oligodendrocyte generation, the presence of NT3Rs has been reported in oligodendrocytes and their precursors. We and others have shown that both progenitors and oligodendrocytes in vitro express the alpha1 and alpha2 isoforms, but the expression of the beta1 isoform is confined to differentiated oligodendrocytes, suggesting that they have different functions. To establish if this is the case during development in vivo, we have studied NT3R isoform expression in glial cells isolated by density gradient centrifugation from rat brains of various ages. We report the presence of the alpha1 NT3R and its variant alpha2, but not that of the beta1 isoform, in newborn rat glial progenitors. The pattern of expression of beta1, both at the level of mRNA and protein, parallels the increase in the number of oligodendrocytes. We found a significant change in the kinetic parameters of [125I]-T3 binding to NT3Rs in these cells during the first month of life, consisting of an increase in the binding capacity that peaks with myelination, and a significative decrease in Kd that coincides with the switch from the alpha to the beta1 isoform. Thus, the expression of NT3R isoforms in the rat oligodendrocyte lineage changes radically from the alpha to the beta1 isoform during the period when oligodendrocytes differentiate from progenitors.

Animals↗
PubMed1997

Expression of thyroid hormone receptors alpha and beta-1 messenger RNAs in human endothelial cells. The T3 hormone stimulates the synthesis of the messenger RNA of the intercellular adhesion molecule-1.

A study of the effect of the L-3,5,3'-triiodothyronine hormone on the expression of the mRNA of the adhesion molecule ICAM-1 led to the observation that the mRNA level is slightly up-regulated in human umbilical-cord endothelial cells. To analyze this induction at a molecular level, the search of T3 hormone receptors was undertaken. In this paper, we show that ECV 304 endothelial cells express the mRNAs encoding two thyroid hormone receptor isoforms alpha(alpha1 and alpha2) and one beta(beta1). This is, to our knowledge, a first important step towards the demonstration of the involvement of these receptors in the induction of the expression of ICAM-1 by the T3 hormone.

Cell Line↗
PubMed1996

High affinity inositol 1,3,4,5-tetrakisphosphate receptor from rat liver nuclei: purification, characterization, and amino-terminal sequence.

Inositol 1,3,4,5-tetrakisphosphate (InsP4) mediates nuclear calcium signalling [Köppler P., Matter, N., Malviya A.N. (1993) J. Biol. Chem. 268, 26248-26252], and a distinct high affinity InsP4 binding site is identified with rat liver nuclei [Köppler, P., Mersel, M., & Malviya, A.N. (1994) Biochemistry 33, 14707-14713] as compared with other rat liver membrane fractions. A novel InsP4 receptor protein derived from rat liver nuclei has been purified to apparent homogeneity employing preparative isoelectric focusing, electrophoretic mobility, nondenaturating polyacrylamide gel electrophoresis, and electroelution. Isoelectric focusing indicated an isoelectric pH around 4.3 +/- 0.2 which was further confirmed by bidimensional electrophoresis. The high affinity nuclear InsP4 receptor was identified as a 74 kDa protein both on the SDS-PAGE and on the bidimensional electrophoresis. Partial microsequence analysis showed that the N-terminal end of nuclear InsP4 receptor consists of amino acids: PNHKNEIAGNFS. The 74 kDa nuclear InsP4 receptor protein is a distinct protein from the other InsP4 receptors purified from other sources and documented in the literature.

Amino Acid Sequence↗
PubMed1994

Mannose dependent tightening of the rat ependymal cell barrier. In vivo and in vitro study using neoglycoproteins.

The possible role of carbohydrate binding proteins (lectins) and glycoconjugates in the formation of junctions ensuring tightening between ependymal cells was studied using synthetic glycoconjugates, the neoglycoproteins. These compounds are prepared by substituting bovine serum albumin with sugar residues and additional labelling (or not) with fluorescein or biotin. Injections of these components into the cerebral ventricles of adult rats resulted in a binding pattern which could be related to their carbohydrate composition. Mannose-containing neoglycoproteins were bound to ependymal cell cilia and penetrated rapidly the brain tissue. Such phenomenon was not seen with glucose- or galactose-containing neoglycoprotein molecules. In contrast, mannose-, galactose- and glucose-containing neoglycoproteins bound strongly to some endothelial cells around blood vessels. Fluorescent unglycosylated serum albumin did not bind to any brain structures. In contrast, co-injection of mannose-containing non-fluorescent neoglycoproteins with the other fluorescent compounds (including fluorescent sugar-free BSA) resulted in the penetration of the fluorescent compounds into the brain tissue. This internalization into brain was attributed to disaggregation of junctions between ependymal cells. Cultured ependymal cells behaved likewise. In short term experiments (5 min-1 h), only the mannose-containing neoglycoproteins bound strongly to the ependymal cells, particularly to the cilia. In long term experiments (1-9 days), mannose-containing neoglycoproteins specifically induced the disappearance of junctions between the cultured cells. These results emphasize the importance of mannose-dependent recognition system in the maintenance of junctions between ependymal cells, where a mannose-binding lectin has been previously detected.

Animals↗
PubMed1993

Cerebellar soluble lectin and its glycoprotein ligands in the developing brain of control and dysmyelinating mutant mice.

The levels of an endogenous lectin, the cerebellar soluble lectin (CSL) and of its endogenous glycoprotein ligands were studied using immunoblotting and affinoblotting techniques in the forebrain of quaking, shiverer and jimpy dysmyelinating mutant mice and their respective control littermates during the postnatal development. In the controls of the mutant mice, the level of CSL showed an important increase between days 5-18 then a stabilization, although at all ages the level of CSL was reduced (at least 15%) in the control littermate of the shiverer mutant. In the shiverer mutant the developmental pattern is similar to the control but was reduced by 50% as compared to the control. In the jimpy mutant an erratic development of CSL was observed which was with quasi absence of CSL at days 12 and 25. Variation of CSL levels in the quaking brain were also observed. CSL glycoprotein ligands also showed variable developmental profiles with a special persistence with ageing of CSL-binding glycoproteins in the quaking and jimpy mice. Developmental variations were also observed between the different control littermates. These results are discussed in view of developmental roles attributed to CSL and its glycoproteins ligands in cell adhesion mechanism during brain ontogenesis and especially myelination.

Aging↗
PubMed1993

Lesion-induced re-expression of neonatal recognition molecules in adult rat cerebellum.

It has been previously shown that sectioning of parallel fibers in the cerebellar molecular layer of adult rats gave rise to rapid reinnervation of the target cells, i.e., Purkinje cells. This paper reports that such a reinnervation is accompanied by reexpression (partial and total) of two developmentally regulated complementary molecules. These are an endogenous mannose-binding lectin, called R1, which reappears at the surface of the dendrites of Purkinje cells, and an endogenous glycoprotein ligand of R1, the 31 kDa glycoprotein, which seems to be neosynthetized and transported to the surface of parallel fibers. In this system, embryonic N-CAM is not reexpressed in neurons but reappears in reactive astrocytes in the vicinity of the lesion. The reexpression of recognition molecules (lectin and glycoprotein ligand) involved in normal synaptogenesis, may constitute the molecular basis for repair of nervous circuits in the adult as well.

Animals↗
PubMed1993

Malignant cells have increased levels of common glycoprotein ligands of the endogenous cerebellar soluble lectin CSL.

The glycoprotein composition of various transformed cells or malignant tumors was analyzed and compared to their respective non-malignant control cells or tissues of several species, including man, using an endogenous carbohydrate-binding protein, the cerebellar soluble lectin CSL (Zanetta et al., J. Neurochem. 49, 1250-1257 (1987). A large variety of transformed cells contain a much higher number and larger quantity of glycoprotein ligands of CSL than the control cells or normal tissues. The glycoprotein profiles were, in most cases, independent of the nature of the cell transformation of the degree of differentiation, of the tissue and species. Thus, it is suggested that many transformed cells have, as a common anomaly, the increased synthesis of the special type of glycan recognized by CSL, expressed on the same polypeptide chains.

Animals↗
PubMed1992

Effect of dibutyryl cyclic AMP and isoproterenol on 7 beta-hydroxycholesterol cytotoxicity and esterification in spontaneous transformed cell lines derived from astrocyte primary cultures.

Incubation of spontaneous transformed cells derived from astrocyte primary cultures with 30 microM 7 beta-hydroxycholesterol (7 beta-OH-CH) which is lethal to the cells or with 150 microM isoproterenol reduces the intracellular level of cAMP (4- and 2-fold respectively). Treatment of the cultures with 0.5 mM dibutyryl (db)-cAMP and 7 beta-OH-CH increases 3-fold the intracellular level of cAMP and both, db-cAMP and isoproterenol, raise the lethal effect of 7 beta-OH-CH and its esterification on C-3-OH by naturally occurring fatty acids (metabolite). Kinetic studies of net steryl-3-esters hydrolysis revealed that db-cAMP and isoproterenol lower that of cholesteryl-3-esters (2-fold) whereas the opposite is found for the metabolite. These data demonstrate that (i) high cAMP intracellular levels modulate differently the net hydrolysis of cholesteryl-3-esters and metabolite, (ii) isoproterenol acts otherwise than cAMP on 7 beta-OH-CH esterification, (iii) the cytotoxicity of 7 beta-OH-CH is linked to its own esterification. The accumulation of metabolite subsequent to db-cAMP or isoproterenol treatment as a result of acyl-CoA:cholesterol acyl transferase activation is discussed.

Animals↗
PubMed1992

Glycoproteins and lectins in cell adhesion and cell recognition processes.

The discovery of endogenous lectins having specific and high affinity for the carbohydrate portions of glycoproteins has opened up new directions in the field of cell adhesion and cell recognition. Two endogenous lectins, termed as CSL and R1, initially isolated from the rat cerebellum and having a wide distribution in mammalian tissues, have been shown to participate in essential mechanisms of cell adhesion. The membrane-bound lectin R1 seems to be involved in transient recognition between neuronal cells, followed by elimination of the glycoprotein ligands at the surface of the recognized cell. In contrast, CSL is a molecule involved in adhesion between various normal or transformed cells since it participates in the formation of tight junctions. The glycoprotein ligands recognized with higher affinity by these two lectins seem to possess a special structure which defines a sub-class of oncofetal HNK-1 glycans. The over-expression of the glycoprotein ligands of these lectins in most transformed cells provides new tools for understanding the underlying mechanism of malignant transformation as well as the generation of signals through cell adhesion.

Animals↗
PubMed1992

Endogenous lectin cerebellar soluble lectin involved in myelination is absent from nonmyelinating Schwann cells.

In the sciatic nerve, two major classes of Schwann cells are present which differ in their capability to produce myelin. Myelinating Schwann cells surround most of the axons with the formation of a typical myelin sheath. Nonmyelinating Schwann cells serve to insulate individual axons without formation of myelin. These dissimilarities between the two types of Schwann cells provided an interesting model for studying mechanisms underlying myelination and the formation of contacts between axons and myelinating cells. It is demonstrated here that the endogenous lectin cerebellar soluble lectin (CSL), implicated in myelin stabilization and in formation of contact between axon and myelinating cells in the CNS and in the sciatic nerve, is undetectable in non-myelinating Schwann cells. In contrast, most axons surrounded by these cells contained the major axonal glycoprotein ligand of CSL, a 31-kDa glycoprotein which is present in large amounts. The possible relationship between the presence of CSL in Schwann cells and their capacity to interact with axons and to produce myelin are discussed.

Animals↗
PubMed1992

Detection of binding sites for biotinylated neoglycoproteins and heparin (endogenous lectins) during cerebellar ontogenesis in the rat: an ultrastructural study.

In a previous paper (Kuchler et al., Eur. J. Cell Biol. 52, 87-97 (1990)), endogenous carbohydrate-binding sites were studied at the optical level during rat cerebellar development on sections of fixed tissue using synthetic tools, biotinylated neoglycoproteins, in conjunction with subsequent avidin-peroxidase staining. It was shown that these tools were capable of revealing carbohydrate-binding sites during development of the rat cerebellum. The staining pattern with the individual probes disclosed variable developmental regulation and consequently suggested that recognition processes during cerebellar development may include several types of carbohydrate determinants. However, studies at the light microscope could not give information on potential membrane-bound localization of carbohydrate-binding sites and therefore discern the possible involvement of these molecules in cell adhesion processes. Furthermore, nuclear staining was suggested at the optical level. In order to elucidate these points, we examined the localization of mannose-, fucose- and heparin-binding sites at the electron microscopic level. Ultrastructural studies demonstrate that these tools are very efficient in detecting intracellular carbohydrate-binding sites, but failed to detect most of them expressed at the cell surface when using immunocytochemical techniques for known receptors, probably because of the interaction of these carbohydrate-binding sites with endogenous membrane-bound ligands. The significance of the nuclear staining and of part of the nucleolus found with fucose-containing neoglycoprotein and of the nuclear staining found with heparin are discussed.

Animals↗
PubMed1991

Malignant transformation in hepatocytes is associated with the general increase of glycoprotein ligands specifically binding to the endogenous lectin CSL.

Several hepatoma cell lines and hepatic ascite tumour cells were studied for the presence of glycoprotein ligands of an endogenous lectin, the "Cerebellar Soluble Lectin" (CSL). This lectin is also present in hepatocytes in vivo and in vitro and can be detected biochemically and immunologically. In transformed cells, the level of CSL glycoprotein ligands is increased 50-fold as compared to the control cells. Such an increase is not observed for the ligands of the plant lectin, concanavalin A, which is, as CSL, a D-mannose-binding lectin. These results indicated that the changes in glycans during malignant transformation, in these cells, is specifically important for minor glycans binding to CSL.

Animals↗
PubMed1991

Up-regulation of dopamine D2 receptor mRNA in rat striatum by chronic neuroleptic treatment.

The effect of prolonged administration of antagonists on rat striatal dopamine D2 receptor binding and mRNA content was examined. Both haloperidol (2 and 4 mg/kg) and sulpiride (10 mg/kg) induced a significant rise in total D2 and D2(444) mRNA level and in Bmax. Regulation of messenger RNA accumulation is thus an important determinant of dopamine D2 receptor density.

Animals↗
PubMed1991

Reduction of protein kinase C activity in the adult rat brain following transient forebrain ischemia.

Acute forebrain ischemia reduced protein kinase C (PKC) activity in the adult rat cortex, striatum and hippocampus by 60-70% after 20 min ischemia episodes, followed by 48 h of recirculation. Ischemia of 1 min, followed by recirculation, produced a less pronounced but significant decrease in PKC activity. The ischemia-induced decrease of PKC affected both the soluble and the membrane-bound kinase. Alterations of PKC predate neuronal death following ischemia.

Animals↗
PubMed1991

Expression and localization in the developing cerebellum of the carbohydrate epitopes revealed by Elec-39, an IgM monoclonal antibody related to HNK-1.

The immunochemical and immunocytochemical reactivity of an anti-carbohydrate monoclonal antibody (Elec-39), obtained against acetylcholinesterase from Electrophorus electricus electric organ, was followed during the postnatal development of the rat cerebellum. The specificity of this antibody resembles that of a family of anti-carbohydrate antibodies that includes HNK-1, L2, NC-1 and NSP-4, as well as IgMs that occur in some human neuropathies. As revealed by immunoblotting techniques, the reactivity of Elec-39 is maximum around postnatal days 10-12. At this age, the antibody reveals eight major proteins of mol. wt ranging between 14 and 150 kDa. Some of them (with mol. wts of 14, 18, 28 and 31 kDa) are transiently expressed. They correspond to previously identified glycoproteins binding to the plant lectin concanavalin A and binding also to the endogenous mannose-binding lectin CSL and endogenous membrane-bound mannose-binding lectin. In young animals, an important staining with the Elec-39 antibody can be observed on postmitotic precursors of granule cells, on astrocyte processes in the external granular layer, on newly formed parallel fibres and on unmyelinated axons of the white matter. In adult animals, the labelling is localized essentially in myelin and also in the cytoplasm of astrocytes. These results are discussed in relation to ontogenetic phenomena occurring during cerebellar development and the potential role of the carbohydrate epitope revealed with Elec-39 as a determinant in cell adhesion processes.

Acetylcholinesterase↗
PubMed1991

The endogenous lectin cerebellar soluble lectin and its ligands in central nervous system myelin of myelin-deficient (mld) mutant mice.

The myelin-deficient (mld) mutation is autosomal recessive mutation in the murine CNS exhibiting severe hypomyelination. The primary defect results in a drastic reduction of myelin basic protein synthesis caused by a duplication of the myelin basic protein gene with partial inversion of the upstream gene copy. The severe deficit of myelin basic protein is responsible for the absence of the major dense line but cannot explain the heterogeneity of myelin compaction found in mld. We have tested the hypothesis that the endogenous cerebellar soluble lectin (CSL) and/or its endogenous glycoprotein ligands could be involved in myelin abnormalities in the dysmyelinating mutant, mld. Immunocytochemical and immunoblotting techniques showed that the CSL level was not reduced significantly in the mld mutant. Furthermore, two ligands of CSL, the myelin-associated glycoprotein and an axonal glycoprotein, with a relative molecular mass of 31 kDa, were not decreased in level in the purified myelin fraction isolated from mld mice. In contrast, three minor glycoprotein ligands of CSL of relative molecular mass of 23, 18, and 16 kDa were greatly reduced in content. The reduced concentration of these low-molecular-mass glycoproteins in mld myelin suggests that they are constituents of compact myelin. Furthermore, the observation that CSL is specifically localized in vivo in regions where mld myelin is more compact and absent from regions devoid of myelin compaction may suggest that the endogenous CSL lectin, as well as its minor glycoprotein ligands, plays a role in the stabilization of the myelin sheath.

Animals↗