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Biomedical subjects

M Veron

Publications and source records attributed to M Veron.

At least 55 records · Page 3Linked to original sources

Prospective multicenter study of vascular-catheter-related complications and risk factors for positive central-catheter cultures in intensive care unit patients.

To determine the incidence rate of complications associated with vascular catheters in intensive care unit patients and to analyze risk factors for a positive vascular culture, we performed a multicenter study of intensive care unit patients at eight French hospitals. During the study period, 865 intravenous catheters were inserted in 566 patients; 362 (41.8%) were peripheral catheters, and 503 (58.2%) were central catheters. Local complications (i.e., infiltration) occurred significantly more often with peripheral than with central catheters (P less than 0.001); in contrast, fever and bacteremia were significantly more often associated with central than with peripheral catheters (P less than 0.01 and P less than 0.05, respectively). The culture of the vascular-catheter tip was positive for 24% of central catheters (32 of 1,000 catheters days) and for 9% of peripheral catheters (21 of 1,000 catheters days). Staphylococcus epidermidis was the most common microorganism isolated from both peripheral and central catheters, followed by Staphylococcus aureus and Pseudomonas aeruginosa. No significant risk factor associated with positive cultures for peripheral catheters was found by univariate analysis. In contrast, the purpose of the cannula (nutrition and monitoring of central venous pressure), the insertion site (jugular), the dressing type (semipermeable transparent dressing), the antiseptic used to prepare the insertion site (povidone iodine), and routine changing of the intravenous administration set were significantly associated with positive cultures of central catheters. Three factors, duration of catheterization, use of a semipermeable transparent dressing, and the jugular insertion site, were found to be independently associated with positive cultures of central catheters by multivariate analysis.

Catheterization↗

[Activity of cefapirin against bacterial strains isolated from acute otitis media in children].

The antibacterial activity of cefapirin was tested against 210 strains isolated from the auricular exudate of childrens' acute otitis media. For 112 strains of Haemophilus studied (20% secreted a beta-lactamase), the MIC 50 and 90 of cefapirin were 2 and 4 mg/l respectively. Ten strains of Branhamella catarrhalis were tested (9 secreted a beta-lactamase) and the MIC ranged from 0.25 to 4 mg/l. Against Streptococcus pneumoniae, cefapirin has an extremely high activity with MIC 50 and 90 less than 0.06 mg/l. Of the strains of Staphylococcus aureus sensitive to meticillin, one had a MIC less than 0.06 mg/l, and 11 had a MIC = 0.25 mg/l. For 14 strains of Enterobacteriaceae studied, we obtained a MIC 50 of 8 mg/l and a MIC 90 of 32 mg/l. The results show that cefapirin is an antibiotic particularly suitable for the treatment of acute otitis media.

Anti-Bacterial Agents↗

[Activity of cefuroxime against bacterial strains isolated from acute otitis media].

The acute otitis media is a frequent infantile disease and, in 80% of cases, a bacterial strain can be isolated from the otorrhoea. Haemophilus influenzae and Streptococcus pneumoniae are the two major species isolated from auricular exudate, and represent two thirds of all isolated strains, with the others comprising Staphylococcus aureus, Branhamella catarrhalis, Pseudomonas aeruginosa, Enterobacteriaceae and corynebacteria. The treatment of this disease is based principally on beta-lactams (aminopenicillins, cephalosporins) administered by the oral route. Cefuroxime is a cephalosporin which is absorbed via the digestive tract in the form of cefuroxim-axetil. The activity of this compound was studied against 210 strains isolated from otorrhoea, collected from children who presented an acute otitis media during the first half of 1989. These strains were: 112 strains of H. influenzae, of which 23 produced a beta-lactamase; 21 strains of Streptococcus pneumoniae; 3 strains of Streptococcus pyogenes; 10 strains of Branhamella catarrhalis of which 9 produced a beta-lactamase; 18 strains of S. aureus; 14 strains of Enterobacteriaceae, and 32 strains of corynebacteria. The minimal inhibitory concentration (MIC) of cefuroxime-axetil was measured by dilution in agar. The MICs of cefuroxime against H. influenzae were low and similar (MIC 50 = 1 mg/l; MIC 90 = 1 mg/l) regardless of whether the strain secreted a beta-lactamase. Overall, 90% and 98% of the 210 strains tested here were inhibited by 1 and 4 mg/l of cefuroxime respectively. These results show that the antibacterial spectrum of cefuroxime-axetil appears to be ideally suited to the bacterial strains isolated from acute otitis media.

Cefuroxime↗

[Comparison of the in vitro activity of amoxycillin + clavulanic acid and ampicillin + sulbactam combinations against 50 Haemophilus influenzae strains producing beta lactamase].

We compared the ability of two beta lactamase inhibitors, clavulanic acid and sulbactam, to reduce the minimal inhibitory concentrations (MICs) respectively of amoxycillin and ampicillin against fifty strains of Haemophilus influenzae producing a beta lactamase. The reduction of MICs of aminopenicillins was studied using low concentrations of beta lactamase inhibitors (0.125 to 0.5 mg/l). Moreover, the synergic effect of each association was evaluated against a heavy bacterial inoculum (10(8) cfu/ml). The combination of amoxycillin + clavulanic acid was more synergic on these strains than the association of ampicillin + sulbactam.

Amoxicillin↗

cAMP-dependent protein kinase from Dictyostelium discoideum.

The cAMP-dependent protein kinase (cAK) from Dictyostelium discoideum is an enzyme composed of one catalytic and one regulatory subunit. Upon binding of cAMP, the holoenzyme dissociates to liberate free active catalytic subunits. The cAK is developmentally regulated, ranging from very little activity in vegetative cells to maximal expression in postaggregative cells. Although there is no immunological cross-reaction between the subunits of cAKs from Dictyostelium and from other organisms, they share several biochemical properties. A complete cDNA for the regulatory subunit has been cloned and sequenced. Only one copy of the gene for the regulatory subunit is present per haploid genome. On the basis of the comparison of the structure of the cAK from Dictyostelium with its counterparts in yeast and higher eukaryotes, we propose a model for the evolution of cyclic-nucleotide-binding proteins.

Amino Acid Sequence↗

Cloning of a cDNA for the S-adenosyl-L-homocysteine hydrolase from Dictyostelium discoideum.

We screened a cDNA library of the primitive eukaryote Dictyostelium discoideum constructed in the expression vector lambda gt11 with a specific antiserum directed against S-adenosyl-L-homocysteine hydrolase (AdoHcy hydrolase) and isolated cDNA clones coding for fusion proteins with beta-galactosidase. The identity of the largest of these clones was further assessed by analysis of hybrid-selected in vitro translation products. Using the cDNA as a probe, we showed that only one gene coding for AdoHcy hydrolase is present per genome and that a single transcript of 1.6 kb could be detected at various stages of differentiation. The nucleotide sequence of the cDNA was determined. It corresponds to the carboxyterminal half of the protein whose primary structure is highly homologous to the AdoHcy hydrolase from rat liver. The significance of this strong conservation of AdoHcy hydrolase in the course of evolution is discussed.

Adenosylhomocysteinase↗

In vitro quantitative model of catheter infection during simulated parenteral nutrition.

We developed a quantitative in vitro model of catheter infection. Colonization was initiated by inoculating the catheter lumen with a small number of bacteria (approximately 5 x 10(3) viable organisms). Then the inoculated catheters were used for simulated total parenteral nutrition therapy consisting of infusions for 9 h a day, and bacteria were counted in the effluent fluid against time, enabling us to monitor catheter colonization quantitatively. Bacterial colonization of prosthetic devices is a progressive process, as evidenced by the slow day-to-day increase of bacterial release seen here. On the other hand, bacterial strains of various representative species exhibited significant differences in their ability to infect catheters. These results suggest that the in vitro model presented here is a reliable tool for monitoring the degree of catheter colonization under standardized conditions and could be used for further studying the main factors of catheter-related sepsis or the treatment of this information.

Bacteria↗

Cloning and cDNA sequence of the regulatory subunit of cAMP-dependent protein kinase from Dictyostelium discoideum.

cDNA clones encoding the regulatory subunit of the cAMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) from Dictyostelium discoideum were isolated by immunoscreening of a cDNA library constructed in the expression vector lambda gt11. High-affinity cAMP-binding activity was detected in extracts from bacteria lysogenized with these clones. Nucleotide sequence analysis of three overlapping clones allowed the determination of a 1195-base-pair cDNA sequence coding for the entire regulatory subunit and containing nontranslated 5' and 3' sequences. The open reading frame codes for a protein of 327 amino acids, with molecular weight 36,794. The regulatory subunit from Dictyostelium shares a high degree of homology with its mammalian counterparts, but is lacking the NH2-terminal domain required for the association of regulatory subunits into dimers in other eukaryotes. On the basis of the comparison of the regulatory subunits from Dictyostelium, yeast, and bovine tissues, a model for the evolution of these proteins is proposed.

Amino Acid Sequence↗

Comparison of the regulatory and catalytic subunits of cAMP dependent protein kinase from Dictyostelium discoideum and bovine heart using polyclonal antibodies.

The purified regulatory (R) and catalytic (C) subunits of cAMP dependent protein kinase (cAK) from the primitive eukaryote Dictyostelium discoideum have been compared with the homologous proteins from bovine heart by SDS-PAGE followed by Western blotting using polyclonal antibodies. No cross-reaction could be demonstrated by this technique although the slime mold subunits share several functional properties with their mammalian counterparts and are able to form functional hybrid holoenzymes.

Animals↗

Association with HeLa cells of Campylobacter jejuni and Campylobacter coli isolated from human feces.

We developed a rapid in vitro test for determining the association of Campylobacter jejuni and C. coli with HeLa cells. Association was expressed as a weighted mean of the number of bacteria associated with one cell in an association index (AI). The reproducibility of the AI was checked by repeating the test six times, using four strains chosen at random. Means and standard deviations of the means were 7.3 +/- 1.2, 6.8 +/- 0.9, 1.8 +/- 1.2, and 0.1 +/- 0.2. The experimental conditions for which the results are reliable have been standardized. Among 42 strains from human feces, two groups appeared: for 22 nonassociative strains (52%), AI values ranged from 0.0 to 2.1 (mean +/- SD, 0.5 +/- 0.6); for 20 associative strains (48%), AI values ranged from 3.5 to 8.3 (mean +/- SD, 6.2 +/- 1.4). Of these 42 strains, 17 were clinically documented. Diarrhea occurred more frequently in patients infected with associative strains than in those infected with noninvasive strains (7/7 versus 3/10, P = 0.01). Fever also occurred more frequently in patients infected with associative strains (6/7 versus 2/10, P = 0.03). Transmission electron microscopy and viable counts made after killing of extracellular bacteria by gentamicin support the fact that associated Campylobacter spp. are adherent to the cell membrane and are internalized into cytoplasmic vacuoles. The described test seems to be a convenient and rapid method for estimating the pathogenicity of a given strain.

Bacterial Adhesion↗

Reversible dissociation of aspartokinase I/homoserine dehydrogenase I from Escherichia coli K 12. The active species is the tetramer.

Dimers of aspartokinase I/homoserine dehydrogenase I from Escherichia coli K 12 have been isolated under very mild conditions. The dimers which cannot be distinguished from the tetramers by their kinetic properties, reassociate in the presence of potassium ions or L-aspartate. The selective sensitivity of aspartokinase I/homoserine dehydrogenase I to mild proteolytic digestion of dimers has been used to probe the reassociation reaction under the conditions of aspartokinase assay. We demonstrate that rapid reassociation occurs and that the protein species present in the assay when dimers are used to test the activity is tetrameric. These results confirm the previously proposed model for the subunit association of aspartokinase I/homoserine dehydrogenase I.

Aspartokinase Homoserine Dehydrogenase↗

Isolation of the aspartokinase domain of bifunctional aspartokinase I-homoserine dehydrogenase I from E.coli K12.

A proteolytic fragment (Mr approximately 25 000) carrying only the aspartokinase activity has been purified by chromatofocusing after limited proteolysis of aspartokinase I-homoserine dehydrogenase I from E.coli K12. The NH2-terminal sequence shows that it corresponds to the amino terminal peptide of the native enzyme. The results confirm a previous hypothesis about the organization of native aspartokinase I-homoserine dehydrogenase I.

Amino Acid Sequence↗

The regulatory subunit of cAMP-dependent protein kinase from Dictyostelium discoideum: cellular localization and developmental regulation analyzed by immunoblotting.

The level of the regulatory subunit of the cAMP-dependent protein kinase from Dictyostelium discoideum was analyzed in subcellular fractions of cells at various stages of development by Western blotting. The protein was found only in the cytosolic fraction. A small amount of regulatory subunit was present in vegetative cells, and its level increased sharply during the first hours of aggregation; a further increase also occurred during culmination. Analysis of mature spores and of the stalky mutant HL 65 revealed that the protein is present only in prespore cells.

Dictyostelium↗

Inactivation of S-adenosyl-L-homocysteine hydrolase by cAMP results from dissociation of enzyme-bound NAD+.

S-Adenosyl-L-homocysteine hydrolase (EC 3.3.1.1) is inactivated by cAMP and also by 2'-deoxyadenosine, and in both cases, activity is restored by incubating the inactivated enzyme with NAD+. We have previously presented evidence that, despite these similarities, inactivation by these two ligands proceeds by different mechanisms. We have now used a fluorescence technique to quantitate enzyme-bound NAD+ and NADH on S-adenosyl-L-homocysteine hydrolase from Dictyostelium discoideum, and we have confirmed that cAMP and 2'-deoxyadenosine inactivate by different mechanisms. Whereas inactivation by 2'-deoxyadenosine is due to reduction of the enzyme-bound NAD+ to NADH, incubation of S-adenosyl-L-homocysteine hydrolase with cAMP results in dissociation of the enzyme-bound NAD+. The dissociation is reversible, and reactivation likely occurs by restoration of the initial NAD+ content. This reversible inactivation by cAMP may be a mechanism of controlling biological methylation reactions by adjusting intracellular concentrations of S-adenosyl-L-homocysteine through action of S-adenosyl-L-homocysteine hydrolase.

Adenosylhomocysteinase↗

Protection against Yersinia infection induced by non-virulence-plasmid-encoded antigens.

Specific immunity against Yersinia was induced by plasmid-encoded antigens not associated with virulence. Mice were immunised with viable bacteria from a virulence-plasmid-cured strain of Y. pseudotuberculosis. This antigenic stimulation generated specific protection against virulence-plasmid-harbouring strains of Y. pseudotuberculosis and Y. pestis, demonstrating that protection can be generated by organisms lacking plasmid-encoded virulence antigens.

Animals↗

S-adenosyl-L-homocysteine hydrolase from Dictyostelium discoideum is inactivated by cAMP and reactivated by NAD+.

Purified S-adenosyl-L-homocysteine hydrolase from Dictyostelium discoideum is inactivated when incubated at 25 degrees C with cAMP. Half maximal velocity of the inactivation process occurs at 10 microM cAMP. Catalytic activity is fully restored by further incubation with NAD+, but not with NADP+ or NADH. The enzyme must be preincubated with cAMP or NAD+ to induce inactivation or reactivation, respectively, since neither of these ligands has an effect on the active or inactive enzyme when added directly to the assay. These results suggest a role for cAMP and NAD+ in the regulation of cellular methylation reactions by altering the level of S-adenosyl-L-homocysteine via S-adenosyl-L-homocysteine hydrolase.

Adenosylhomocysteinase↗