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M Chevalier

Publications and source records attributed to M Chevalier.

At least 19 recordsLinked to original sources
PubMed2000

Interaction of murine BiP/GRP78 with the DnaJ homologue MTJ1.

The activity of Hsp70 proteins is regulated by accessory proteins, among which the most studied are the members of the DnaJ-like protein family. BiP/GRP78 chaperones the translocation and maturation of secreted and membrane proteins in the endoplasmic reticulum. No DnaJ-like partner has been described so far to regulate the function of mammalian BiP/GRP78. We show here that murine BiP/GRP78 interacts with the lumenal J domain of the murine transmembrane protein MTJ1 (J-MTJ1). J-MTJ1 stimulates the ATPase activity of BiP/GRP78 at stoichiometric concentrations. The C-terminal tail of BiP/GRP78 is not required for the interaction with J-MTJ1, leaving the function of this portion of the molecule still unclear. Physical interactions between J-MTJ1 and BiP/GRP78 are stable and can be abolished by a single histidine --> glutamine substitution in the highly conserved HPD motif shared by all DnaJ-like proteins. The J-MTJ1 fragment, but not the mutant J-MTJ1:H89Q fragment, stimulates the ATPase activity of Escherichia coli DnaK, although at a higher concentration than its genuine partner DnaJ. Full-length DnaJ does not stimulate BiP over the range of concentrations investigated. These results indicate that the J domain of MTJ1 is sufficient for its interaction with BiP/GRP78 and cannot be substituted by E. coli DnaJ.

Adenosine Triphosphatases↗
PubMed2000

One-step capillary isoelectric focusing for the separation of the recombinant human immunodeficiency virus envelope glycoprotein glycoforms.

One-step capillary isoelectric focusing was investigated as a rapid method to resolve the glycoforms of the heterogeneous recombinant human immunodeficiency virus (HIV) envelope glycoprotein (rgp 160sMN/LAI). The separation was performed in a poly(vinyl alcohol) (PVA) coated capillary using a mixture of ampholyte of narrow and wide pH range. A combination of saccaharose and 3-(cyclohexylamino)-1-propanesulfonic acid was shown to be the most efficient additive to avoid protein precipitation which occurs at a pH close to its pI. Although the calibration curve [isoelectric point (pI) vs. migration times] showed a non-linear relationship, an adequate linearity could be yielded for short pI ranges permitting to exhibit the acidic character of the different glycoforms of the rgp 160s MN/LAI (pI from 4.00 to 4.95). Reproducibility evaluated by comparing the performance of a polyacrylamide and a PVA coated capillary showed that low RSD values were obtained for intra-day (0.5 to 1.9%) and inter-day (1.6 to 7.6%) measurements using the PVA capillary. Moreover, the long term stability of the PVA capillary was demonstrated by measuring the variation of migration times of the protein markers for a long period of use. Finally, this method was able to differentiate the glycoform pattern of two close glycoproteins such as the rgp 160 of two sub-populations of the virus HIV-1.

Electrophoresis, Capillary↗
PubMed1999

Specificity of peptide-induced depolymerization of the recombinant carboxy-terminal fragment of BiP/GRP78.

In the present study, we have used a non-denaturing gel electrophoresis assay to characterize the specificity of the peptide-induced depolymerization process of the isolated recombinant C-terminal domain (C30) of the molecular chaperone BiP, in the presence of specific synthetic peptides and with the neuropeptide Substance P. In the absence of peptidic ligand, C30 self-associates readily into multiple oligomeric species. Upon peptide addition, C30 oligomers convert into dimers, then into monomers. Our data indicate that the algorithm we previously developed to predict putative BiP binding sites in any protein sequence is also a good indicator as to whether a peptide can efficiently induce depolymerization of the C-terminal peptide binding domain and stimulate the ATPase activity of the full-length protein.

Amino Acid Sequence↗
PubMed1998

Substrate binding induces depolymerization of the C-terminal peptide binding domain of murine GRP78/BiP.

To investigate the role of each domain in BiP/GRP78 function, we have used a full-length recombinant BiP engineered to contain two enterokinase sites; one site is located after an N-terminal FLAG epitope, and a second site has been inserted at the junction between the N- and C-terminal domains (FLAG-BiP.ent). FLAG-BiP.ent oligomerizes into multiple species that interconvert with each other in a slow, concentration- and temperature-dependent equilibrium. Binding of ATP or AMP-PNP (adenosine 5'-(beta, gamma-imino)triphosphate), but not ADP, or of a peptidic substrate induces depolymerization of FLAG-BiP.ent and stabilization of monomeric species. Enterokinase cleavage of monomeric, nucleotide-free BiP.ent results in the physical dissociation of the 44-kDa N-terminal ATPase fragment (N44.ent) from the 30-kDa C-terminal substrate binding domain (C30.ent). Upon dissociation, the freed C-terminal substrate binding domain readily undergoes self-association while N44.ent remains monomeric. Enterokinase cleavage performed in the presence of a synthetic peptide prevents oligomerization of the freed C30.ent domain. Addition of ATP during enterokinase cleavage has no effect on C30.ent oligomerization. Our data clearly indicate that binding of a specific peptide onto the C-terminal domain, or ATP onto the N-terminal domain, induces internal conformational change(s) within the C30 domain that result(s) in BiP depolymerization.

Adenosine Triphosphate↗
PubMed1997

[Helicobacter infections of man and of domestic carnivores: comparative data].

The role of Helicobacter pylori in generating of the chronic gastritis and in the maintaining of the gastroduodenal ulcerous disease, has been a major medical discovery of these past years in human gastroenterology. More recently in Man, studies have showed that the gastric tumours (adenocarcinoma, lymphoma) are epidemiologically associated with the H. pylori infection. Although the H. pylori infection is the one of the most frequent in the word, the epidemiologic and ecologic aspects of this infections are still not very well known. Thanks to phylogenic studies using the new molecular biology techniques and to fundamental experimental studies, we know more about helicobacteria in domestic carnivores as well as their morphologic characteristic, their taxonomia and more importantly details concerning their ecological niche. Few clinical studies have been made to this day, but the ones that have been undertaken are interesting in confirming the extensive prevalence of Helicobacter infections in domestic carnivores and in underlining their role in the genesis of the inflammatory gastropathies observed in these species. Recent observations have demonstrated the ubiquitous character of these helicobacteria by showing their presence in the stomach of man, dogs and cats. This ubiquitous character has led some scientists to consider the potential zoonotic risk of the human infection by Helicobacter heilmannii, felis or pylori. Finally, the Helicobacter infection of animals seems to be an interesting model not only in the study of the affections caused by these bacteria, but also in the elaboration of a future vaccine against the H. pylori infection in man.

Animals↗
PubMed1996

Comparative study of dose values and image quality in mammography in the Madrid area.

During 1990-1992 a study of dose and image quality in mammography was carried out in the Madrid area. Values of air kerma and mean glandular dose per film estimated at 14 public and private centres (17 X-ray units) by means of the Leeds TOR(MAX) mammographic phantom and from a sample of patients were reported in a previous paper. This second paper describes image quality results obtained by the same Leeds TOR(MAX) phantom. Inferior image quality was found for units without a grid (most of them older systems) and/or using aluminium filtration. In units with a grid, inferior image quality was due to the low optical density of the images, the use of inadequate image receptors and the use of an aluminium filter. Image quality results were compared with the standards of the UK Breast Screening Programme and proposed European Guidelines. It is concluded that mammography image quality might be considered as acceptable when TOR(MAX) phantom films achieved at least 10 lp mm-1 and 1.2% for high contrast resolution and threshold contrast visibility (6 mm details) respectively.

Humans↗
PubMed1995

Purification and renaturation of Japanese encephalitis virus nonstructural glycoprotein NS1 overproduced by insect cells.

The nonstructural protein NS1 of Japanese encephalitis virus is a major immunogen produced during flavivirus infection. However, the function of this protein has not been identified. To analyze its biochemical properties and evaluate its potential activity in the virus life cycle, the protein was produced in Spodoptera frugiperda insect cells (Sf9), using a recombinant baculovirus, and purified. As described previously by M. Flamand, V. Deubel, and M. Girard (1992, Virology 191, 826-836), a small fraction of the synthesized recombinant protein could mature into a dimer, whereas the major part was retained in intracellular aggregates. This insolubility was used to recover the protein in a purified form using a two-step procedure. Isolated inclusion bodies, in which NS1 constituted over 60% of the protein, were solubilized in 8 M urea. NS1 was further purified by reverse-phase HPLC and recovered at over 90% purity with an overall yield of over 60%. Conditions promoting reoxidation-renaturation of the purified protein were then investigated at a concentration of 100 micrograms/ml at pH 8. The presence of 8 M urea during reoxidation of NS1 with oxidized glutathione was essential prior to renaturation by dialysis to avoid reaggregation, the main side pathway of refolding in vitro. Three major species, all monomeric, were resolved by nonreducing SDS-PAGE. The form showing the lowest apparent molecular weight comigrated with native unreduced NS1 and was recognized by a monoclonal antibody directed against a conformational epitope strictly dependent on the native structure of the protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Comparative study of dose values and image quality in mammography in the area of Madrid.

Dose values and image quality in mammography resulting from a study carried out in the area of Madrid during 1990-1991 are presented in a two-part sequence. In this paper are reported the values of air kerma and mean glandular dose per film estimated at 14 centres by means of the Leeds TOR(MAX) mammographic phantom and from patient samples. The results obtained from patient measurements allow us to deduce that the TOR(MAX) phantom assembly used (4.5 cm thick) is equivalent to an average 5 cm thick compressed breast from the population in the area of Madrid. Approximately 75% of the air kerma values resulting from phantom estimations are below 6.6 and 12.2 mGy for X-ray units with and without grid, respectively. The mean glandular doses per film for 75% of the units with and without grid are below 1.5 and 1.7 mGy, respectively. The results showed that the higher values of both air kerma and mean glandular dose obtained for the units without grid result from the use of slow speed recording systems. On the other hand, the quality control programme carried out shows important faults in the performance of the X-ray units which have an important impact on both dose and image quality. Finally, the third quartile values of the air kerma and mean glandular dose per film (10.4 and 1.7 mGy, respectively), deduced by considering all the units (with and without grid), are proposed to be the reference values of the mammographic examinations during the aforementioned period. In a second paper, the image quality is analysed by using the same Leeds TOR(MAX) phantom. Results for each test object included in the phantom are discussed as a function of the X-ray unit characteristics. Subsequently, the phantom images obtained with each X-ray system are scored and the resulting values are compared with the corresponding dose values, so that the dose-image quality relationship for each unit is obtained.

Breast↗
PubMed1994

[Ultrastructural study of host-parasite relations: early phases of Venturia inaequalis installation on susceptible and resistance apple leaves].

The penetration mechanism study of Venturia inaequalis is undertaken on leaves of scab-susceptible and scab-resistant apple cultivars. The penetration through the cuticle occurs whatever the host phenotype. The resistance will be expressed when the infectious hyphae is in contact with the epidermal cell wall. The epidermal cell of susceptible variety does not show any modification. The resistant variety reaction is very fast, since twenty hours after penetration many wall appositions are setting, the cytoplasm strongly degenerates and the parasite hyphae are already necrotic. The contact between the host and the parasite is always very complex in the case of resistant host. The rapidity and the important cytological modifications of the host parasite interaction connect this reaction to an hypersensitive reaction.

Ascomycota↗
PubMed1993

Continuous intercostal analgesia with 0.5% bupivacaine after thoracotomy: a randomized study.

This study was undertaken to evaluate the effectiveness of 0.5% bupivacaine (360 mg/day) as a continuous infusion through an indwelling intercostal catheter inserted intraoperatively in the management of pain after thoracotomy. Eighty-six patients were randomized into three groups: group 1 = intercostal bupivacaine, group 2 = intercostal saline solution, and group 3 = fixed-schedule intramuscular buprenorphine. Supplementary buprenorphine was given as required. Pain and pulmonary function were assessed throughout the first 5 days after operation. Pain score was lower in group 1 than in group 2 for the first 8 hours after operation (p < 0.02). During the first 3 postoperative days, mean postoperative pain scores of 5 or more were recorded in 9% of group 1 patients versus 40% of group 2 patients (p < 0.05) and 13% of group 3 patients (not significant). Total doses of buprenorphine were lower in groups 1 and 2 than in group 3 (p < 0.001). No between-group differences in pulmonary function were observed. Respiratory complications occurred in no patients in groups 1 and 3 versus 5 in group 2 (p < 0.05). Continuous intercostal bupivacaine provided similar early pain control as compared with fixed-schedule narcotics but induced better analgesia with fewer complications than on-demand narcotics alone (group 2).

Analgesia↗
PubMed1992

In vitro androgenic induction of a major protein in epithelial cell subcultures from mouse vas deferens.

Pure epithelial cell cultures, obtained from primary culture of vas deferens tissue collected from 20- to 30-day-old mice, were amplified by subculturing the cells over 3T3 feeder layer in a serum-free defined medium. Adhesion and proliferation of epithelial cells did not require androgens, but a minimal concentration of 5.10(-7) M hydrocortisone. In that system, epithelial cells expressed cytokeratin but failed to produce the tissue specific mouse vas deferens protein (MVDP) in response to androgens. Various culture procedures and medium compositions were assayed for induction of MVDP expression. Culture onto microporous membrane inserts, which allow polarization of cells, is absolutely required for androgenic induction of MVDP. Androgen action did not require the presence of hydrocortisone, insulin, triiodothyronine, pituitary extracts, epidermal growth factor and acetylcholine. A minimal supplemented medium was then defined in which the expression of MVDP by epithelial cells in response to androgens was dose dependent. It has also been shown that this response at each concentration of dihydrotestosterone was heterogeneous at individual cell level. Highly reproducible results were obtained from epithelial cell cultures between 8th to 16th passages, showing that subcultured cells have maintained their ability to differentiate and express specialized functions.

Acetylcholine↗
PubMed1990

Hydrogen peroxide mediates the oxidative inactivation of enzymes following the switch from anaerobic to aerobic metabolism in Klebsiella pneumoniae.

Klebsiella pneumoniae utilizes distinct pathways for the anaerobic and aerobic metabolism of glycerol. During anaerobic growth, glycerol is first converted to dihydroxyacetone by glycerol dehydrogenase; subsequent phosphorylation yields dihydroxyacetone phosphate. During aerobic growth, glycerol is initially phosphorylated to yield glycerol 3-phosphate; subsequent reduction then gives dihydroxyacetone phosphate. A coordinated response occurs when anaerobically growing cells are switched to aerobic conditions. Synthesis of glycerol dehydrogenase is repressed, glycerol dehydrogenase is inactivated, and the protein is degraded. Ethanol dehydrogenase and propanediol oxidoreductase are also inactivated when cells are exposed to oxygen (Johnson, E. A., Levine, R. L., and Lin, E. C. C. (1985) J. Bacteriol. 164, 479-483). Exposure of anaerobically growing cells to low concentrations of hydrogen peroxide also inactivated these three enzymes and led to rapid degradation of glycerol dehydrogenase. Glycerol dehydrogenase was purified and characterized after in vivo oxidative modification initiated by hydrogen peroxide. No differences in molecular weight, amino acid composition, or Km were detected between the native and oxidatively modified forms, although the modified enzyme had only 10% of the catalytic activity of the native form. The oxidatively modified enzyme was very susceptible to degradation by subtilisin while the native enzyme was resistant. Chloramphenicol prevented the inactivation and degradation of glycerol dehydrogenase caused by exposure to oxygen but did not block that caused by hydrogen peroxide. Thus, protein synthesis appears necessary for in vivo oxidative modification caused by exposure to oxygen but is not necessary when the process is initiated by exposure to hydrogen peroxide. The newly synthesized protein(s) presumably catalyzes the production of hydrogen peroxide which is required for the metal-catalyzed oxidative modification of susceptible enzymes.

Aerobiosis↗
PubMed1990

Histoautoradiographic study of rRNA and mRNA transcription activity related to secretory function in lizard epididymis.

The lizard epididymis is an androgen-dependent organ whose epithelial cells undergo marked changes in structure and secretory activity during the annual cycle. These changes are connected to fluctuations of testosterone levels. During the breeding season, the epididymis produces a major protein secretion, the L-proteins. In the present work we studied the fluctuations of RNA synthesis and accumulation during the annual cycle by means of histoautoradiographic methods. Total RNA synthesis was determined by uridine incorporation; accumulation of rRNAs and L-protein mRNAs were determined by in situ hybridization. Total RNA synthesis began during reorganization (Phase I), then increased gradually during differentiation and growth (Phase II). The synthesis peaked during maturation (Phase III), but stopped abruptly during hypersecretory activity (Phase IV). The rRNAs were very abundant from Phase II to Phase IV, which is related to the presence of many ribosomes as revealed by electron microscopy. The mRNAs of L-proteins were detected only during Phases III and IV in all epithelial cells. For every phase of the sexual cycle there exists a strong correspondence between the changes in transcriptional activity (rRNA and specific mRNA) of the epithelial cells and changes in the testosterone levels.

Animals↗
PubMed1990

[Long-term clinical course after second laparotomy in ovarian cancer].

A series of thirty consecutive epithelial ovarian cancer patients were reviewed after long-term follow-up (more than 5 y) since their second-look operation (SLO). All patients had advanced tumors (stages IIb-IV). Primary chemotherapy consisted of a cisplatin-associated regimen. For all patients adjuvant treatment had been planned after completion of the SLO. Mean follow-up after SLO was 68 months (47-103 months). Tumor status at SLO divided the patients in 2 subgroups: Group A = 13 patients (43%), with no evidence of histologically proved disease at time of operation (NED); Group B = 17 patients (57%), with macroscopic persistence of tumor. Survival was significantly better in the first group than in the second (77% at 5 yr vs less than 25%). Recurrence rate in the NED group was 7.7% (1 recurrence at 32 months). Eight of 17 patients with gross tumor at SLO underwent satisfactory resection. However, recurrence rate was high (75%) and survival rate was low (25% at 5 yrs). This result was not significantly better than that of patients with no optimal resection at SLO (9 patients, survival 22%). Second effort resection at SLO does not seem to be beneficial in these patients after partial failure of initial chemotherapy with cisplatin. The usefulness of systematic second look operations is discussed. Controlled randomized trials should be made to determine the exact role of SLO in ovarian cancer treatment.

Adult↗
PubMed1989

Randomized controlled trial of adenine arabinoside 5'-monophosphate in chronic active hepatitis B: comparison of the efficacy in heterosexual and homosexual patients.

Twenty-two heterosexuals and 21 homosexuals with chronic active hepatitis B and who had HBsAg, HBeAg and hepatitis B virus DNA in serum were randomized separately to receive adenine arabinoside monophosphate or placebo. In the 10 heterosexuals and nine homosexuals who received placebo, no change in hepatitis B virus DNA level and HBeAg was observed. Among the patients who received adenine arabinoside monophosphate, seven of the 12 heterosexuals and five of the 12 homosexuals lost hepatitis B virus DNA; five heterosexuals and three homosexuals also lost HBeAg; one homosexual lost HBsAg. There was no significant differences in response between heterosexual and homosexual patients. When results were pooled, there was a significant effect of adenine arabinoside monophosphate on hepatitis B virus replication. None of the 19 patients who received placebo but 50% of the 24 patients who received adenine arabinoside monophosphate were negative for serum hepatitis B virus DNA at 10 months after treatment (p less than 0.001) and none of the 19 patients who received placebo and 33% of the 24 patients who received adenine arabinoside monophosphate were negative for HBeAg in serum (p less than 0.005). Retrospective analysis showed that disappearance of hepatitis B virus DNA after administration of adenine arabinoside monophosphate was more common (i) in patients with a low pretreatment hepatitis B virus DNA level than in patients with a high pretreatment hepatitis B virus DNA level (8/11 vs. 4/13, p less than 0.05); (ii) in patients with a high pretreatment ALT level than in patients with a low pretreatment ALT level (10/14 vs. 2/10, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Lectin activity and distribution of chicken lactose lectin I in the extracellular matrix of the chick developing kidney.

A lectin activity inhibitable by thiodigalactose, N-acetyllactosamine, lactulose, lactose and by an antibody raised against CLL I (chicken-lactose lectin I) has been investigated in the chick embryo developing kidney. At post-induction stages this activity was found in both mesonephros and metanephros. In immunofluorescence and immunoelectron microscopy, the extracellular distribution of CLL I was similar in the mesonephros and the metanephros. The lectin was never found intracellularly; cultured kidney cells did not express any endogenous lectin but were rich in lectin-receptor sites, which led to the hyphothesis that CLL I is not produced in situ but could be adsorbed on renal cells. Potential physiological roles for embryonic lectins are discussed.

Animals↗
PubMed1987

[Determination of chloramphenicol residues with reverse-phase high pressure liquid chromatography. Use in a pharmacokinetic study in rainbow trout with confirmation by mass spectrometry].

A simple and rapid high-performance liquid chromatography (HPLC) method for the determination of chloramphenicol (CAP) residues in trout muscle tissue is described. After an acetonitrile-sodium chloride extraction followed by washing with hexane and purification through a Sep-Pak C18 cartridge, analysis is performed by reversed-phase HPLC on Spherisorb ODS-II (5 microgram) using water-methanol (1:1) as the mobile phase. The detection limit of the method is 5 micrograms/kg. The mean recovery from spiked muscle samples at the 10-micrograms/kg level is 56 +/- 7.4%. CAP residues are confirmed by gas chromatography-mass spectrometry at concentrations as low as 1 micrograms/kg. Residues were detected in trout muscle after oral administration during 15 days. On the tenth day after treatment, an average of CAP of less than 5 micrograms/kg was measured. No residues were detected after the twentieth day.

Animals↗