Search PubMed⌕ Search

Biomedical subjects

J Pierre

Publications and source records attributed to J Pierre.

At least 37 records · Page 2Linked to original sources
PubMed1996

Structure of the low-affinity penicillin-binding protein 5 PBP5fm in wild-type and highly penicillin-resistant strains of Enterococcus faecium.

Among its penicillin-binding proteins (PBPs), Enterococcus faecium possesses a low-affinity PBP5, PBP5fm, which is the main target involved in beta-lactam resistance. A 7.7-kb EcoRI chromosomal fragment of E. faecium D63r containing the pbp5fm gene was cloned and sequenced. Two open reading frames (ORFs) were found. A 2,037-bp ORF encoded the deduced 73.8-kDa PBP5fm, the amino acid sequences of which were, respectively, 99.8, 78.5, and 62% homologous to those of the low-affinity plasmid-encoded PBP3r of Enterococcus hirae S185r and the chromosome-encoded PBP5 of E. hirae R40 and Enterococcus faecalis 56R. A second 597-bp ORF, designated psrfm, was found 2.3 kb upstream of pbp5fm. It appeared to be 285 bp shorter than and 74% homologous with the regulatory gene psr of E. hirae ATCC 9790. Different clinical isolates of E. faecium, for which a wide range of benzylpenicillin MICs were observed, showed that the increases in MICs were related to two mechanisms. For some strains of intermediate resistance (MICs of 16 to 64 micrograms/ml), the increased level of resistance could be explained by the presence of larger quantities of PBP5fm which had an affinity for benzylpenicillin (second-order rate constant of protein acylation [k+2/K] values of 17 to 25 M(-1) s(-1)) that remained unchanged. For the two most highly resistant strains, EFM-1 (MIC, 90 micrograms/ml) and H80721 (MIC, 512 micrograms/ml), the resistance was related to different amino acid substitutions yielding very-low-affinity PBP5fm variants (k+2/K < or = 1.5 M(-1) s(-1)) which were synthesized in small quantities. More specifically, it appeared, with a three-dimensional model of the C-terminal domain of PBP5fm, that the substitutions of Met-485, located in the third position after the conserved SDN triad, by Thr in EFM-1 and by Ala in H80721 were the most likely cause of the decreasing affinity of PBP5fm observed in these strains.

Amino Acid Sequence↗
PubMed1995

Nosocomial acquisition of multiresistant Acinetobacter baumannii: risk factors and prognosis.

To identify risk factors for and prognostic indicators of the nosocomial acquisition of multiresistant Acinetobacter baumannii in an intensive care unit, we prospectively studied 40 patients: 13 who were infected with this organism and 27 who were colonized. Isolates were identified by pulsed-field gel electrophoresis; the infected/colonized patients were compared with 348 noninfected, noncolonized patients by logistic regression analysis and with matched historical controls in a cohort study. The severity of illness (evaluated by the APACHE II score; P < .05) and previous infection (P < .001) were retained as independent risk factors for acquiring A. baumannii. Logistic regression analysis selected a high APACHE II score (P < .01) and the acquisition of A. baumannii (P < .01) as factors independently associated with death. The acquisition of A. baumannii was associated not only with high mortality but also with a length of stay on the intensive care unit in excess of that due to the underlying disease alone; specifically, the attributable mortality was 25%, with a risk ratio for death of 2.0 (95% confidence interval, 1.11-3.62), and the duration of stay for infected/colonized patients was 10.3 days longer than that for controls (P < .001).

APACHE↗
PubMed1995

Inducible and constitutive expression of resistance to glycopeptides and vancomycin dependence in glycopeptide-resistant Enterococcus avium.

A clinical isolate of Enterococcus avium, Ea1, which exhibited inducible, low-level resistance to vancomycin and teicoplanin, and two mutants selected from this strain, Ea3 and Ea31, were studied. Ea3 was vancomycin dependent and derived from Ea1, while Ea31 was not vancomycin dependent, was constitutively resistant, and was derived from Ea3. Hybridization studies revealed that vanA was present in Ea1 and suggested that it was located on a high-molecular-weight plasmid. In the absence of induction, Ea1 synthesized only the natural UDP-MurNAc-pentapeptide precursor, and after induction it synthesized an additional precursor identified as UDP-MurNAc-tetrapeptide-D-lactate. The latter was the only precursor found in Ea3 and Ea31, even after precursor accumulation. From these results, we infer that (i) the low level of resistance to glycopeptides in strain Ea1 may be in part due to the residual synthesis of the normal precursor and (ii) the vancomycin dependence of mutant Ea3 could be due to the fact that this strain does not produce any peptidoglycan precursor in the absence of induction.

Adult↗
PubMed1994

Inhibition by two lavendustins of the tyrosine kinase activity of pp60F527 in vitro and in intact cells.

The mutant pp60F527 protein possesses an activated protein-tyrosine kinase (PTK) activity correlated with a transforming activity. We have studied the inhibition of the pp60F527 PTK activity by two EGF-R tyrosine kinase inhibitors, lavendustin A and one of its derivatives, lavendustin C6. In vitro, both molecules were non-competitive inhibitors for the ATP binding site and uncompetitive inhibitors for the peptide binding site. The determined IC50S of the inhibition of pp60F527 kinase activity were 18 microM for lavendustin A and 5 microM for lavendustin C6, as determined on the exogenous substrate enolase, showing that lavendustin C6 was more potent than lavendustin A. Lavendustin C6, but not lavendustin A, inhibited the tyrosine phosphorylation of pp60F527 cellular substrates (the GAP-associated p190, pp125FAK and cortactin) in intact cells. However, this in situ inhibitory effect did not result in a reversion of the morphological changes induced by pp60F527 in cells. On the other hand, lavendustin C6 and lavendustin A exerted antiproliferative effects on cells, suggesting that inhibition of cellular targets related or not to the kinase was also possible.

3T3 Cells↗
PubMed1994

Activation of the mitogen-activated protein kinase cascade by tyrphostin (RG 50864).

Tyrphostins are synthetic compounds which have been described as in vitro inhibitors of epidermal growth factor (EGF)-receptor tyrosine kinase activity. In NIH3T3 cells, stimulation of EGF-receptor tyrosine kinase leads to an increase of intracellular protein phosphorylations, among them the phosphorylation of mitogen-activated protein (MAP) kinase and the S6 kinases p90rsk and p70S6K. Phosphorylation of these proteins, either on tyrosine or serine/threonine residues or on both residues increases their protein kinase activity. Unexpectedly, treatment of NIH3T3 cells with both tyrphostin (RG 50864) and EGF results in an increase in the level of tyrosine phosphorylation of the MAP kinase. During this treatment, we also observed an increase in MAP kinase and S6 kinase p90rsk activities. Tyrphostin treatment diminishes the level of c-fos mRNA but has no effect on c-myc mRNA expression nor on S6 kinase p70S6K activity. Mitogenic signalling induced by EGF in NIH3T3 cells was blocked by tyrphostin, suggesting that the target(s) for this event may be elements downstream from the MAP kinase or independent of this signal transduction.

3T3 Cells↗
PubMed1994

Effects of tyrphostins on the activated c-src protein in NIH/3T3 cells.

Tyrphostins are synthetic compounds that have been described as in vitro and in vivo inhibitors of epidermal growth factor receptor tyrosine kinase activity. In NIH/3T3 cells transfected with the c-src/F527 gene, an increase in the level of tyrosine phosphorylation of several proteins, including pp125FAK, within a group of proteins of 120 kDa, of p85 (cortactin), and of p62 is observed, which is due to the elevated kinase activity of the resulting encoded pp60F527 protein. In the transfected cells, we showed that the tyrphostins we used, i.e., AG18, AG34, and AG82, strongly diminished the tyrosine phosphorylation of these proteins. Analysis of the steady state level of pp60F527 in tyr-phostin-treated cells revealed that AG34 and AG82, the two most potent compounds, also induced 30 and 48% decreases, respectively, in the amount of pp60F527, while having no action on the levels of other proteins, especially the pp60F527 kinase substrates. Measurement of the rates of pp60F527 synthesis and degradation showed that this decreased level was due to a slower rate of synthesis in the presence of AG34 and AG82. Tyrphostins also reversed the pp60F527-induced transformed morphology of NIH/3T3 cells and also inhibited the pp60F527 kinase activity in vitro. We conclude that the effects elicited by the tyrphostins occurred not only through the inhibition of the pp60F527 protein kinase activity but also through a selective reduction of the Src protein steady state level in the cases of AG34 and AG82. This is a novel mode of action for these two tyrphostins, which were the most active compounds in this system.

3T3 Cells↗
PubMed1994

Immunoreactivity to glial fibrillary acid protein (GFAP) in the brain and spinal cord of the lamprey (Lampetra fluviatilis).

In contradiction to previous results, under certain conditions, it is possible to demonstrate GFAP immunoreactivity in the brain and spinal cord of a jawless vertebrate. The critical parameters appear to be (1) fixation with 4% paraformaldehyde at pH 7.4, (2) a very short period (2-6 hr) of postfixation, and (3) immunovisualization by the avidin/biotin/peroxidase technique rather than immunofluorescence or PAP techniques. Immunoreactivity appears throughout the brain and spinal cord, most frequently as fine prolongations normal to the pial surface, which can on occasion be traced to cell bodies near the ventricles or in the ependymal layer. The evolutionary implications of the presence of glial fibrillary acidic protein in a member of the Agnatha are discussed.

Animals↗
PubMed1992

Susceptibility of Xanthomonas maltophilia to six quinolones and study of outer membrane proteins in resistant mutants selected in vitro.

The in vitro susceptibilities of 75 clinical isolates of Xanthomonas maltophilia to nalidixic acid, five fluoroquinolones, latamoxef, and doxycycline were determined. Spontaneous mutants were selected, at a frequency of about 10(-5) to 10(-7) from four strains by culturing the strains in the presence of each quinolone. Selection in the presence of nalidixic acid provided mutants that were either resistant only to that compound or that exhibited cross-resistance to all the fluoroquinolones tested. Cross-resistance was always observed for mutants selected on any of the five fluoroquinolones. It was always associated with chloramphenicol resistance and, frequently, with doxycycline resistance. The electrophoretic alterations of the outer membrane proteins of the mutants suggest that different mechanisms may be involved in quinolone resistance in X. maltophilia.

4-Quinolones↗
PubMed1992

[GABA-immunoreactive structures in the lumbar spinal cord of the frog].

The distribution of GABA-immunoreactive (GABA-I) structures has been studied in the frontal sections of the lumbar spinal cord of the lake frog using PAP-method. GABA-I was revealed as labeled cell bodies, fragments of fibres and small point-like structures assumed to be in most cases synaptic contacts of GABA-I axons. Labeled fragments of fibres and point-like structures were found in gray and white matter of the spinal cord. The GABA-I cell bodies were revealed in the dorsal horn, intermediate zone and ventral part of the gray matter. Labeled cells were found in the cavity of the central canal. The findings are discussed in relation to the modern data on the GABA-ergic control of the spinal cord functions.

Animals↗
PubMed1991

Early effect of BCNU on rat astrocytes. Inhibition of S6 kinase activation by growth factors.

In primary cultures of astrocytes, methylmethane, 2-N-methyl 9-hydroxy-ellepticinium acetate, ditercalinium, 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea and 1,3 bis (2-chloroethyl)-1-nitrosourea (BCNU) blocked to various extents the activation of S6 kinase by acidic fibroblast growth factor and insulin [or insulin-like growth factor 1 (IGF1)]. The effects of the most active agent, BCNU, were time and concentration dependent. Pretreatment of cells with 50 microM BCNU for 1 hr completely prevented S6 kinase activation by growth factors for at least 2 days. The S6 kinase activity of unstimulated cells was slightly affected. S6 kinase activation by 12-O-tetradecanoylphorbol 13 acetate was also strongly impaired by treating cells with BCNU whereas activation by 8-bromo-cyclic AMP was slightly reduced. Cyclic AMP-dependent protein kinase and phospholipid and Ca(2+)-dependent protein kinase were unaffected. BCNU had no direct effect on IGF1 binding to cell surface receptors or on the S6 kinase activity of cell cytosols.

Animals↗
PubMed1990

Mechanisms of action in NIH-3T3 cells of genistein, an inhibitor of EGF receptor tyrosine kinase activity.

Genistein has been shown to inhibit specifically in vitro the epidermal growth factor (EGF)-receptor tyrosine protein kinase activity (Akiyama et al., J Biol Chem 262: 5592-5597, 1987). When the effects of genistein on NIH-3T3 cells were studied, a cytostatic effect was observed at low concentration (less than 40 microM) and a cytotoxic effect at higher concentration (greater than 40 microM). Genistein was able to block the mitogenic effect mediated by EGF on NIH-3T3 cells (IC50 = 12 microM) or by insulin (IC50 = 19 microM). Genistein was also able to block the mitogenic effect mediated by thrombin (IC50 = 20 microM) although the thrombin receptor does not involve a protein tyrosine kinase activity. Genistein at cytostatic concentration (less than 40 microM) did not prevent the induction of c-myc mRNA synthesis caused by the activation of EGF receptor by EGF. Therefore the cytostatic effect of genistein on NIH-3T3 cells did not appear to be mediated by EGF receptor tyrosine kinase inhibition. This hypothesis was also supported by the absence of effect of genistein on the EGF-stimulated phosphorylation of several proteins and particularly of a cytosolic 80 kD protein. The stimulation of S6 kinase activity of cells treated by EGF was prevented by genistein. The stimulation by EGF of in situ S6 phosphorylation was also prevented by genistein. In addition, S6 kinase extracted from cells treated by EGF was inhibited by genistein. These effects occur at similar doses and maximal inhibition of S6 kinase was obtained at about 15 microM.

Animals↗