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M Véron

Publications and source records attributed to M Véron.

At least 91 records · Page 5Linked to original sources
PubMed1987

Gene isolation by direct in situ cAMP binding.

The regulatory subunit of the cAMP-dependent protein kinase expressed in clones isolated by immunoscreening of a lambda gt11 cDNA library from Dictyostelium discoideum exhibits high affinity for cAMP [Mutzel et al., Proc. Natl. Acad. Sci. USA 84 (1987) 6-10]. Based on this property, we have developed a screening procedure to detect in situ cAMP-binding activity directly on phage plaques transferred to nitrocellulose filters. Highly radioactive cAMP was synthesized using [alpha-32P]ATP at 3000 Ci/mmol as the substrate of purified adenylate cyclase from Bordetella pertussis. Filter replicas of the library plated at 3 X 10(4) pfu/dish, were incubated in the presence of 2 nM [32P]cAMP and then washed thoroughly. Three clones out of 1.2 X 10(5) were detected, all of which coded for the regulatory subunit, as judged by hybridization with a specific DNA probe. The cAMP binding to the purified clones was characterized in situ by displacement with specific analogues. The ability to displace labelled cAMP was in accord with the affinities of the analogues previously reported for the regulatory subunit of the Dictyostelium cAMP-dependent protein kinase. We are able to detect fmol levels of regulatory subunit contained in phage plaques and therefore the method could be used to screen libraries from other organisms for proteins exhibiting high affinities for cyclic nucleotides.

Bacteriophages↗
PubMed1987

[Gas-liquid chromatography in microbiological diagnosis].

With gas-liquid chromatography, it is possible to detect chemical compounds which are specific of micro-organisms: either metabolic products, or structural components. This technique permits to simplify the diagnosis: it is the case for anaerobic bacteria, where the analysis of the fermentation acids produced in a 48 hours liquid culture enables to rapidly establish the diagnosis, at least as far as the genus is concerned. It may also increase the accuracy of the diagnosis by searching such or such metabolite or structural component which are specific of a species or a sub-species. Some authors have already determined automatic systems of bacterial identification; these systems are based on a computer analysis of the chromatographic profile of cellular fatty acids. Finally it is important to emphasize that liquid-gas chromatography may markedly shorten the delay of identification by allowing, in some cases, a direct diagnosis in pathological samples.

Bacteria↗
PubMed1986

Detection and developmental regulation of the mRNA for the regulatory subunit of the cAMP-dependent protein kinase of D. discoideum by cell-free translation.

cAMP is an important effector of the development of Dictyostelium discoideum amoebae and could exert its effects on gene expression through the cytosolic cAMP-dependent protein kinase (cAK). Antibodies, specific for the regulatory subunit (R) of the cAK, were used to investigate the developmental regulation of the corresponding mRNA (R-mRNA) by in vitro translation and immunoprecipitation. Under such conditions, a single polypeptide of the same mol. wt. as R (42 kd) is detected, showing that the protein is not synthesized as a large precursor. The level of the R-mRNA, which is low in vegetative cells, increases 10- to 20-fold during the first hours of development. Its expression is stimulated by the treatment of AX3 cells with cAMP either added to a concentration of 1 mM or given as 0.1 microM pulses every 5 min, whereas such treatments have little or no effect in cells of strain AX2. The R-mRNA remains highly expressed (0.01-0.03% of translatable mRNA) throughout post-aggregative development; it is not affected by mechanical disaggregation of the multicellular organism. The parallel developmental time courses of the translatable R-mRNA and the R protein produced in vivo suggest that the expression of this polypeptide is regulated at the level of mRNA synthesis.

Carrier Proteins↗
PubMed1985

Experimental infection of gnotobiotic mice with Campylobacter jejuni: colonisation of intestine and spread to lymphoid and reticulo-endothelial organs.

Axenic and monoxenic C3H mice were used to develop an animal model for enteroinvasiveness and translocation of Campylobacter jejuni. After oral administration of 10(7)-10(8) viable cells of C. jejuni on day 0 (D0), bacterial colonisation was followed quantitatively during 23 days by counting free luminal bacteria and tissue-associated bacteria in the duodenum, ileum and colon. The kinetics of bacterial colonisation were the same in axenic and monoxenic mice; bacteria were more numerous in distal than in proximal intestinal segments. Electronmicroscope studies of axenic infected mice showed C. jejuni free in the intestinal lumen on D2 and D7, and adhering to microvilli or included in enterocyte vacuoles in the colon on D2 without inflammatory reaction; C. jejuni was isolated from mesenteric lymph nodes until D23, but from blood, spleen, liver and bile until D1 only. In monoxenic infected mice, C. jejuni was found from D1 to D4 in mesenteric lymph nodes and Peyer's patches, whereas the associated bacterium (Clostridium perenne) was never cultured from any organs. On the basis of our observations in this gnotobiotic model, C. jejuni appears to be an enteroinvasive bacterium with a particular affinity for lymphoid organs.

Animals↗
PubMed1984

Purification of S-adenosyl-L-homocysteine hydrolase from Dictyostelium discoideum: reversible inactivation by cAMP and 2'-deoxyadenosine.

S-Adenosyl-L-homocysteine hydrolase from Dictyostelium discoideum has been purified to homogeneity. It is composed of four subunits, each with a molecular mass of 47,000. In the hydrolysis direction, the enzyme has a pH optimum of 7.5, a Km for S-adenosyl-L-homocysteine (SAH) of 6 microM, and a Vmax of 0.22 mumol min-1 mg-1. In the synthesis direction, the pH optimum is 8.0, the Km for adenosine is 0.4 microM, and the Vmax is 0.30 mumol min-1 mg-1. Although the enzyme binds beta-nicotinamide adenine dinucleotide, as well as adenosine 3',5'-cyclic monophosphate and 2'-deoxyadenosine, these ligands have no effect on enzymatic activity when added to the assay mixture. However, preincubation of SAH hydrolase with NAD+ results in a 25% activation of the enzyme. In addition, this ligand has a striking effect on subunit-subunit interactions, as shown by stabilization of quaternary structure during polyacrylamide gel electrophoresis. Preincubation with cAMP or 2'-deoxyadenosine inactivates the enzyme. Although in both cases the activity is restored upon further incubation with NAD+, we show that inactivation by these two ligands proceeds by different mechanisms. NAD+-reversible inactivation by cAMP and 2'-deoxyadenosine was also observed with the SAH hydrolase from rabbit erythrocytes. Thus, these previously unreported properties of SAH hydrolase also occur with mammalian enzymes and are not restricted to D. discoideum.

Adenosylhomocysteinase↗
PubMed1983

A triglobular model for the polypeptide chain of aspartokinase I-homoserine dehydrogenase I of Escherichia coli.

Limited proteolysis of aspartokinase I-homoserine dehydrogenase I from Escherichia coli by type VI protease from Streptomyces griseus yields five proteolytic fragments, three of which are dimeric, the other two being monomeric. One of the monomeric fragments (27 kilodaltons) exhibits residual aspartokinase activity, while the second one (33 kilodaltons) possesses residual homoserine dehydrogenase activity. The smallest of the dimeric species (2 X 25 kilodaltons) is inactive; the two other dimers exhibit either only homoserine dehydrogenase activity (2 X 59 kilodaltons) or both activities (hybrid fragment, 89 + 59 kilodaltons). This characterization of the proteolytic species in terms of molecular weight, subunit structure, and activity leads to the proposal of a triglobular model for the native enzyme. In addition, the time course of the formation of the various fragments was followed by measuring enzymatic activity and performing gel electrophoretic analysis of the protein mixture at defined time intervals during proteolysis. On the basis of the results of these studies, a reaction scheme describing the succession of events during proteolysis is given.

Aspartokinase Homoserine Dehydrogenase↗
PubMed1981

[Evaluation of ready-to-use media for blood cultures based on 1580 specimens (author's transl)].

We have compared the performance of two types of manufactured media, by making 1580 blood cultures from 250 hospitalized people with bacteremia. The results showed that, within the limits of this present study, the Bacto Tryptic Soy Broth w/SPS and Bacto Thiol Broth w/SPS (DIFCO) are better than the brain heart broth and Schaedler broth (Hemoline, BioMérieux). There was no difference in the microbial growth rate and the type of isolated bacteria with the two brands of media. The superior results obtained with the used media from Difco, as compared to the ones from BioMérieux, could be due to a difference of sensitivity of these broths.

Bacteriological Techniques↗
PubMed1980

Non-michaelian kinetics of adenylate cyclase in Dictyostelium discoideum.

Dependance of adenylate cyclase activity from "aggregation-component" Dictyostelium discoideum cells on ATP concentration has been examined. The enzyme exhibits on-Michaelian kinetics towards its substrate, from which two apparent Km values of 17 micro M and 0.4 mM can be calculated. Several experiments were performed in order to test for a difference between adenylate cyclase activities measured at ATP concentrations corresponding to each Km. Activities were associated with the particulate fraction of the extracts; however attempts have failed to recover them from purified plasma membranes. Loss of activity in cellular extracts, its stimulation by Mn2+ ions, and the increase in basal specific activity during differentiation were identical whether the enzyme was tested at either of the ATP concentrations. Although these experiments do not exclude the possible existence of two distinct molecular entities, they rather favour the hypothesis of an adenylate cyclase exhibiting anti-cooperative kinetics towards ATP.

Adenosine Triphosphate↗
PubMed1980

[Search for homologous antibodies during urinary infections in patients with or without renal allografts (author's transl)].

We studied the immune response during urinary infections, firstly in 20 patients with a renal allograft and receiving immunosuppressive agents, secondly in 55 patients consulting on a renal unit. Homologous antibodies were sought in the urine (test for antibodies fixed on urinary bacteria AFBU) and in the serum (seroagglutination, indirect immunofluorescence) using an antigens strains isolated from patients' urine. Comparative statistical analysis of the results given by the 3 methods reveals a good correlation between these tests in non-transplanted patients. On the other hand, there is no statistical link between seroagglutination and the AFBU test in transplanted patients, whereas the results of indirect immunofluorescence and the AFBU test remain strongly correlated. The interest of the 3 methods is discussed.

Antibodies, Bacterial↗
PubMed1979

Effect of antibiotics on mucoid strains of Pseudomonas aeruginosa.

A study of the susceptibility to 18 antibiotics has been performed on 47 mucoid strains comparatively to 71 fried-egg strains of Pseudomonas aeruginosa. The minimal inhibitory concentration was determinated by agar dilution method. On the whole, the mucoid strains were more sensitive to antibiotics than the fried-egg strains. The more effective antibiotics were carbenicillins, aminosids, colistin and tetracyclines. However, this drug susceptibility of mucoid strains were heterogeneous. The results of a statistical analysis demonstrated that the strains of P. aeruginosa were distributed into two classes: a first class clustered very sensitive strains to most antibiotics and a second class clustered more resistant strains. The mucoid strains were included almost equally into the two classes (respectively 45% and 55%). The fried-egg strains were more homogeneous, since 89% of these strains were in the resistant class. The antibiotics which distinguished the best between the two classes were: tobramycin, netilmicin, amikacin, colistin and tetracyclines. A study of the phenotypes and associations of resistances has been equally performed.

Anti-Bacterial Agents↗
PubMed1978

[Physiological study and taxonomy of Alcaligenes species: A denitrificans, A. odorans and A faecalis].

We have studied 43 strains of the species Alcaligenes dentrificans, A. odorans, and A. faecalis. Twenty-five of them were isolated by enrichment culture on minimal medium containing an organic acid (L-malate, succinate, tartrate, adipate, or itaconate) and N2O as a respiratory electron acceptor. These constitute a single phenon with the A. dentrificans strain type and 9 other strains isolated from clinical specimens. However, strain 4 differs from the other 34 strains in 12 nutritional characters, in its ability to effect a meta cleavage of diphenols, and by the absence of tetrathionate reductase. The percentages of G + C are the following: strains isolated from soil, 66.4 +/- 1.1; collection strains, 67.0 +/- 1.3. The 5 strains of A. odorans differ from the 34 strains of A. denitrificans (not including strain 4) in their inability to denitrify nitrate and use D-saccharate, adipate, pimelate, suberate, beta-hydroxy-beta-methylglutarate meso-tartrate, azelate, and itaconate. Their percentage of G + C is much lower: 56.1 +/- 0.4. From the nutritional point of view the 3 strains of A. faecalis resemble A. dentrificans. However, they differ from the latter by their inability to grow anaerobically on NO3-, NO2-, N2O, and by a slightly lower percentage of G+ C: 64.3 +/- 0.0. The 43 strains synthesize poly-beta-hydroxybutyric acid. None of them is chemolithotrophic.

Alcaligenes↗
PubMed1978

[Duodenal bacterial flora in the child during post-surgical stasis].

The bacterial flora of the small bowel was studied in infants with stasis after surgery. Samples were obtained, with radiological assistance, by duodenal aspiration and then immediately analysed by the laboratory in blind tests, both qualitatively and quantitatively. There were two groups of patients: one receiving parenteral nutrition and a second on enteral elementary diet; patients without any gastro-intestinal tract disease formed the control group. Pseudomonas aeruginosa and Enterobacteria were isolated significantly more often in both groups of patients compared to the control group. Quantitatively, the predominant flora -- and not total flora -- was different in the three groups. When considering bacteriological species, only P. aeruginosa (greater than 10(6)/ml) differed significantly in numbers in both groups compared to the control group. With these bacteriological investigations, the "contaminated proximal small bowel syndrome" is better defined and a group of high-risk patients may be identified.

Child↗
PubMed1978

[The bacterial flora of the appendix in children].

Qualitative bacterial samples were taken from 53 appendices which were purulent, or had lymphoid hyperplasia or were normal. The results did not demonstrate a specific bacterial flora responsible for appendicular disease in childhood.

Appendicitis↗
PubMed1977

[An acellular vaccine from Pseudomonas aeruginosa. II. -- Estimate of immuneserum protective effect by measure of bacterial clearance (author's transl)].

The protective antibodies obtained in mice with an acellular vaccine P2 from Pseudomonas aeruginosa have been titered in vivo by a bacterial clearance technique. The kinetics of the bacterial disappearance from the circulating blood were compared in mice which had been vaccinated or had received injection of specific serum, and in normal mice. The following results were obtained; (a) the disappearance of the bacteria from the blood is quicker in immunized animals; (b) the rate of bacteria in the blood depends on doses of injected serum; (c) the titers of protective antibodies expressed by 99% clearance dose is directly in relation with the vaccinating dose.

Animals↗
PubMed1976

A taxonomic study of the Aeromonas hydrophila-Aeromonas punctata group.

A total of 203 characters has been determined for 68 strains of Aeromonas belonging to the Aeromonas hydrophila-A. punctata group. The results have been subjected to computer analysis using the coefficient of Jaccard-Sneath and the strains clustered by the method of aggregation according to the variance. The 68 strains can be divided into two well-segregated classes on the basis of 59 variable characters, of which seven are of diagnostic value. The two classes are considered as two separate species. The first one (42 strains) is assigned to the type species of the genus, A. hydrophila, and it appears that the species name, A. punctata, is an illegitimate synonym for A. hydrophila. The second (26 strains) constitutes a new species for which the name A. sobria sp. nov. is proposed. The type strain of this new species has been deposited under the reference CIP7433 (our strain 208).

Aeromonas↗