PubMed Health⌕ Search

Biomedical subjects

G Vincendon

Publications and source records attributed to G Vincendon.

At least 37 records · Page 2Linked to original sources
PubMed1991

Expression of plasma membrane and cell surface phospholipids and gangliosides of chick embryo neurons grown in primary cultures: developmental studies.

Plasma membranes isolated from chick embryo neurons after 2 days (division phase) and 5 days (maturation phase) in culture showed no differences in the phospholipid (PL) pattern or in the plasma membrane average fluidity. Significant ganglioside (Ggl) variations were only found in GM1 and GD3 which represent 35% of the total plasma membrane N-acetylneuraminic acid (NeuNac) content (1.8-fold GM1 NeuNac increase, 1.4-fold GD3 NeuNac reduction). Lactoperoxidase-catalyzed radioiodination (125I) under saturating conditions indicated that the hydrophobic core of cell surface Ggl was more exposed to the hydrophilic extracellular environment than that of PL. Nevertheless, when interneuronal contacts start to form, the 125I-labelling of both PL and Ggl dropped progressively throughout the maturation phase. Further analysis revealed that (1) plasma membrane GD3 was not accessible to the enzymatic labelling, and (2) surface phosphatidylethanolamine (PE) and GT1b became more accessible to the external medium during development, whereas the opposite was found for phosphatidylcholine (PC) and GM1. The overall profile of radioiodinated PL and Ggl was unaltered when poly-L-lysine was substituted for polyethyleneimine as culture substratum, except for an increase in GT1b labelling 24 h after plating. These results suggest the existence of a 'buffering' mechanism protecting the neuronal plasma membrane during cellular growth from marked changes in fluidity, polar lipid composition and relative localization of polar lipids with regard to the extracellular environment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[Is Cerebellar Soluble Lectin a major immunological target in multiple sclerosis?].

In a recent paper: (Zanetta J.P. et al., Lancet, 1990, 335, 1482-1484) the authors showed that antibodies against the mannose-binding protein Cerebellar Soluble Lectin (CSL) are present in the cerebrospinal fluid of most multiple sclerosis patients. Herein, the properties and roles of the molecule as they are currently understood are described; hypotheses suggested by the consistent presence of anti-CSL antibodies in multiple sclerosis patients are discussed.

Antibodies↗
PubMed1990

Antibodies to cerebellar soluble lectin CSL in multiple sclerosis.

Cerebrospinal fluid samples from 239 patients with various neurological disorders were tested for the presence of autoantibodies to an endogenous mannose-binding protein, the cerebellar soluble lectin CSL, by means of an immunoblotting test with rat CSL as antigen. 47 of 51 patients with multiple sclerosis were positive for anti-CSL compared with 30 of 188 patients with other neurological disorders. 14 of the 30 false-positive patients were over 60 years old, an age group not typical of multiple sclerosis patients. The specificity of the test for multiple sclerosis was 85% and the sensitivity 93.5%. The possibility that CSL is an important immunological target in multiple sclerosis allows new insights into the possible causes and development of this disorder.

Adult↗
PubMed1990

Rat liver nuclei protein kinase C is the isozyme type II.

Rat liver nuclei protein kinase C is identified as type II isozyme employing monospecific antibodies obtained against each three types of rat brain protein kinase C isozymes. (Yoshida, Y., Huang, F. L., Nakabayashi, H., and Huang, K-P. (1988) J. Biol. Chem. 263, 9868-9873). A major immunoreactive protein band at 80 kDa was revealed by type II isozyme antibodies at each step of purification, nuclear extract included. The nuclear protein kinase C has been purified to apparent homogeneity as revealed by silver nitrate staining on sodium dodecyl sulfate-polyacrylamide gel electrophoresis showing a single 80 kDa protein band. It does seem that 66 kDa protein (Masmoudi, A., Labourdette, G., Mersel, M., Huang, F. L., Huang, K.-P., Vincendon, G., and Malviya, A. N. (1989) J. Biol. Chem. 264, 1172-1179) is a major contaminant devoid of any protein kinase activity. The ratio obtained between protein kinase C enzymatic activity over phorbol dibutyrate bound, at various purification steps, indicates that the nuclear enzyme is a phorbol ester receptor. When isolated nuclei were incubated with 12-O-tetradecanoyl phorbol-13-acetate, endogenous protein kinase C activity was elevated about 8-10-fold suggesting the existence of phorbol ester signaling pathway at the level of nucleus. The role of nuclear protein kinase C is delineated in the regulation of inducible gene transcription

Animals↗
PubMed1990

An endogenous lectin and one of its neuronal glycoprotein ligands are involved in contact guidance of neuron migration.

In the central nervous system, postmitotic neurons migrate along astrocytic processes to reach their adult position. The molecular mechanisms of this guided migration are not clearly defined, although some steps have been shown to involve proteases and cell adhesion molecules. We report that monovalent antibodies (Fab fragments) raised against an endogenous cerebellar soluble lectin (CSL) completely inhibit neuronal migration in cultures of cerebellar explants at concentrations as low as 50 micrograms/ml. A similar inhibition pattern was obtained with Fab fragments prepared against one of the endogenous glycoprotein ligands of CSL, the 31-kDa glycoprotein (this glycoprotein is a membrane-bound glycoprotein specifically occurring, in the cerebellum, at the surface of immature neurons). We propose that this lectin-glycoprotein interaction supports the adhesion between neurons and the astrocyte guide during the migration of cerebellar immature neurons.

Animals↗
PubMed1990

Stereospecific inositol 1,4,5-[32P]trisphosphate binding to isolated rat liver nuclei: evidence for inositol trisphosphate receptor-mediated calcium release from the nucleus.

It is well known that inositol 1,4,5-trisphosphate binding and release of calcium are mediated by the same protein. Several reports have indicated the location of the inositol 1,4,5-trisphosphate receptor in organelles other than endoplasmic reticulum. Immunocytochemical studies on the subcellular localization of 1,4,5-trisphosphate receptor in the Purkinje cells from two laboratories have given contradictory results regarding the nuclear location of this receptor. In this paper, a high-affinity inositol 1,4,5-[32P]trisphosphate binding site (Kd = 0.11 nM) on nuclei isolated from rat liver and devoid of any microsomal, mitochondrial, or plasma membrane constituents is documented. Furthermore, we present data demonstrating that inositol 1,4,5-trisphosphate is capable of releasing 45Ca2+ from the intact isolated liver nuclei. A rapid and transient release of calcium that was taken up by nuclei in the presence of ATP is observed. The role of inositol 1,4,5-trisphosphate in the coupling between cytoplasmic second messengers and nuclear events activated during signal transduction is postulated.

Animals↗
PubMed1990

Normal composition of the major lipids and the distribution of their fatty acids in central nervous system myelin further discriminate mld from shiverer mice.

The primary defect in myelin deficiency (mld), an autosomal recessive mutation in mice with severe hypomyelination of the central nervous system (CNS), is a reduction in the synthesis of myelin basic protein (MBP) due to reduced amounts of MBP-specific mRNA. The present study was performed to determine whether alterations of myelin lipid composition might be associated with this defect. Although a 20-fold reduction of myelin was found in mld brain, the lipid/protein and the phospholipid/sulfatide ratios of purified myelin were unchanged. The analysis of polar lipids demonstrated no striking difference. However, phosphatidylethanolamine (including plasmalogens of the ethanolamine type) was decreased by 7.7% in mld. Fatty acids of total and polar lipids (phospholipids + glycolipids) exhibited a slight decrease in 20:1(n-11) and 20:1(n-9). In conclusion, these results further differentiate mld from its allele shiverer, which shares with mld a dramatic reduction of MBP and absence of major dense line but, in contrast, presents other important biochemical differences in CNS myelin.

Animals↗
PubMed1990

Endogenous cerebellar soluble lectin and its ligands in central nervous system myelin of quaking and jimpy mutant mice.

The presence of an endogenous 'cerebellar soluble lectin' (CSL) involved in myelin compaction and myelination was analyzed in the dysmyelinating mutant mice quaking and jimpy. The primary defect in these mutations with severe hypomyelination is still unknown in the quaking mutant but results from a single mutation in the proteolipid protein gene in the jimpy mutant. Both immunocytochemical and immunoblotting techniques showed that CSL was not considerably reduced in its expression in the myelin fraction purified from adult quaking mutants. Furthermore, the myelin-associated glycoprotein and an axonal glycoprotein with a relative molecular weight (Mr) of 31 kilodaltons (kDa) were not decreased in quaking mice. This contrasted with several glycoproteins of Mr 23, 18, 16 and 12 kDa which were absent from the purified quaking myelin. In myelin preparations obtained from the jimpy mutant the CSL level was considerably reduced. This defect did not result from a deficient synthesis of CSL. However, as in the quaking mutation low-Mr glycoproteins were lacking. The nature of the low-Mr glycoproteins absent in quaking and jimpy mice is discussed in relation to previous reports on myelin glycoproteins. In the various mutants, due to different primary mutations, a similar absence of myelin compaction was observed, which could be associated with a deficient level of low-Mr glycoproteins. It is thus postulated that these molecules are essential for ensuring myelin compaction as ligands for the endogenous CSL.

Animals↗
PubMed1990

Phosphorylation by protein kinase C modulates agonist binding to striatal dopamine D2 receptors.

The effect of purified protein kinase C (PKC) on dopamine D2 receptor binding was studied. Saturation binding with [3H]spiperone was not affected. In competition experiments using agonists PKC-treated membranes showed a significant reduction in the proportion of high affinity sites, and the influence of GTP gamma S was abolished. These results suggest that PKC-dependent mechanisms can regulate the coupling between the dopamine D2 receptor and its G-protein.

Animals↗
PubMed1990

Phosphorylation of an inositol phosphate-stimulated protein phosphatase by protein kinase C.

It is shown that the catalytic subunit of an inositol phosphate-stimulated protein phosphatase (a member of the type-1 protein phosphatase family) purified from bovine brain membranes is phosphorylated in vitro by protein kinase C, but not by protein kinase A or by Ca2+/calmodulin-dependent protein kinase II. The phosphorylation of the protein phosphatase by protein kinase C induces an increased sensitivity to stimulation by Ins (1,4,5)P3, Ins(1,3,4,5,6)P5 and heparin.

Animals↗
PubMed1990

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

Endogenous carbohydrate-binding sites were studied during rat cerebellar development on sections of fixed tissue using synthetic tools, biotinylated neoglycoproteins, in conjunction with subsequent avidinperoxidase staining. Neoglycoproteins were constructed by chemically coupling the histochemically pivotal carbohydrate moieties to an inert carrier protein. The sugar part of the neoglycoproteins included common constituents of the carbohydrate part of cellular glycoconjugates, namely mannose, galactose, fucose, N-acetyl-glucosamine, N-acetylgalactosamine and N-acetyl-neuraminic acid to probe for the presence of respective endogenous receptors. Heparin was biotinylated after mild cyanogen bromide activation and aminoalkylation. Specific positive reactions were obtained for all neoglycoproteins and heparin. The staining pattern with the individual probes disclosed variable developmental regulation. Consequently, these results suggest that recognition processes during cerebellar development may include several types of carbohydrate determinants. In two instances, the binding of neoglycoproteins could be compared to endogenous lectin-specific antibodies. Despite a significant extent of accordance the comparison revealed notable differences. These differences were attributed primarily to fixation and the presence of physiological ligands that can mask the active endogenous carbohydrate-binding proteins. In any case, histochemical application of labeled neoglycoproteins is valuable to discern the presence, localization and developmental pattern of binding sites for the carbohydrate part of glycoconjugates, on which further biochemical and cell biological studies can consequently be based.

Acetylgalactosamine↗
PubMed1989

Effect of 7 beta-hydroxycholesterol on astrocyte primary cultures and derived spontaneously transformed cell lines: cytotoxicity and metabolism.

The lethal effect of 7 beta-hydroxycholesterol (7 beta-OHC) on neonatal rat astrocyte primary cultures and spontaneously transformed cell lines derived from them was investigated. Confluent astrocyte primary cultures were not affected by 30 microM 7 beta-OHC over a period of 72 h. In contrast, spontaneously transformed cells were killed by 20 microM 7 beta-OHC within the first 48 h. Further studies indicated that the cell lines metabolized 7 beta-OHC to a product the polarity of which was less than that of 7 beta-OHC. The metabolite was identified as 7 beta-OHC esterified on C-3 by naturally occurring fatty acids. Incubation of the cell lines with 0.5 microM metabolite markedly affected the cells within 24 h. These observations suggest that the 7 beta-OHC metabolite is implicated in the mechanism of action of 7 beta-OHC cytotoxicity on spontaneously transformed cells.

Animals↗
PubMed1989

Protein kinase C located in rat liver nuclei. Partial purification and biochemical and immunochemical characterization.

In the rat liver homogenate, maximal protein kinase C activity was found at two calcium concentrations (1.75 and 3.5 mM). Subcellular fractionation of the liver homogenate revealed that the protein kinase C activity requiring 1.75 mM calcium was present only in the cytosolic and particulate subcellular fractions. The protein kinase C activity requiring 3.5 mM calcium concentration was mainly located in the rat liver nuclei preparation. About 19% of the liver homogenate protein kinase C activity requiring 3.5 mM calcium was present in the nuclei. Goat anti-rat brain protein kinase C antibodies revealed a single immunoreactive band at 80-82 kDa in the rat liver nuclear, particulate, or cytosolic fractions. Based on the ratio of plasma membrane marker enzyme activity determined in the nuclear preparation, the purity of the isolated nuclei was ascertained. Rat liver nuclear protein kinase C activity has been partially purified. The purification steps sequentially employed were Triton X-100 extraction of isolated nuclei, DEAE-cellulose chromatography, Phenyl-Superose, and Mono Q (fast protein liquid) chromatography. The final purification step revealed, by silver nitrate staining on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, two protein bands at 80 and 66 kDa, respectively. These findings provide definitive data regarding the nuclear location of protein kinase C. The nuclear location of protein kinase C may lead to an understanding of the molecular pathway involved in signal transduction from the plasma membrane to the nucleus.

Animals↗
PubMed1989

An endogenous lectin found in rat astrocyte cultures has a role in cell adhesion but not in cell proliferation.

The presence of an endogenous cerebellar soluble lectin (CSL) has been demonstrated in cultured rat astrocytes by using immunocytochemical techniques. In these cells, the location of lectin CSL was found intracellularly as well as on the external surface of the plasma membrane of the cell bodies and processes, especially in the zones of contact between cells. This suggested that CSL could have a role in adhesion of astrocytes to sister cells. Kinetics of adhesion of astrocytes to culture dishes precoated with CSL showed a rapid binding of these cells. In confluent astrocyte cultures, anti-CSL Fab fragments affected the shape and organization of astrocytes (retraction of the cytoplasm), but they did not detach cells from the substratum. These results indicated that CSL has adhesive properties for astroglial cells and is probably involved 1) in adhesion of astrocytes to sister cells; 2) in binding of protoplasmic regions of astrocyte membrane to the substratum. Further support for these roles came from demonstration of the presence in cultures of glycoprotein ligands recognized by this lectin. The problem of the mitogenic properties of the lectin was also questioned. The addition of CSL to confluent astroglial cultures was able to stimulate only by 40% the proliferation of these cells at an optimal concentration of 5 micrograms CSL lectin/ml of culture medium. This indicated that CSL is not a powerful growth factor for astrocytes.

Animals↗
PubMed1989

Antidepressant effect of lithium: a neurochemical study on neuronal uptake of norepinephrine and serotonin.

1. The effect of lithium chloride on neuronal uptake of norepinephrine and serotonin was explored on a pure culture of chicken neurons. While an acute lithium treatment (25 minutes) proves ineffective, a long-term treatment (7 days) decreases the uptake of serotonin and increases the uptake of norepinephrine. 2. The combined administration of lithium (7 days) and clomipramine (25 minutes) appears to have a greater effect on the uptake of serotonin than a treatment limited to only one of the two products. 3. The clinical implications of these results are discussed while emphasizing the interest of lithium in the treatment of depression.

Animals↗
PubMed1989

Carbohydrate and glycoprotein specificity of two endogenous cerebellar lectins.

Two endogenous cerebellar mannose binding lectins have been isolated in an active form by immunoaffinity chromatography employing their respective immobilized antibodies. One of them, termed cerebellar soluble lectin (CSL), was extracted in the absence of detergents, whereas the other, called Receptor 1 (R1), was soluble only in the presence of detergents. Tests of inhibition of agglutination of erythrocytes were performed with mono-, oligo and polysaccharides, as well as glycoconjugates of known structures. On the basis of agglutinating activities these 2 lectins are different from the previously reported lectins in brain, since they were not inhibited by galactosides and lactosides and were only marginally inhibited by glycosaminoglycans. CSL and R1 were better inhibited by mannose-rich glycopeptides as compared to the corresponding oligosaccharides. The different inhibition patterns obtained with glycans of known structures indicated that these lectins are very discriminative. Although CSL and R1 have similar specificities, they differed in their binding properties towards glycopeptides of ovalbumin. Both lectins showed considerable affinity for endogenous cerebellar glycopeptides, also rich in mannose. These glycopeptides belong to a few endogenous Con A-binding cerebellar glycoprotein subunits and are not present on other endogenous Con A-binding glycoproteins. In the forebrain, where CSL and R1 were also present, at least some of the glycoproteins interacting with the lectins were different from that observed in the cerebellum. Our data overall suggest that specific cell recognition in the nervous system could be invoked via the interactions between widely distributed lectins and cell-specific glycoproteins.

Animals↗