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J P Chauvet

Publications and source records attributed to J P Chauvet.

13 recordsLinked to original sources
PubMed2005

Effect of the polar headgroup of phospholipids on their interaction with actin.

It is generally admitted that actin filaments are anchored to a membrane by membranar actin-binding-proteins. However, we found that actin may also interact directly with membrane phospholipids. The actin-phospholipid complex has been investigated at the air-water interface using a film balance technique. In order to probe the effect of the phospholipid headgroup on the actin-phospholipid interaction, we focus mainly on phospholipids that have the same acyl chain length but different headgroups. For all the phospholipids, the apparent area per molecule (the total surface divided by the number of lipid molecules) increases after the injection of the protein into the subphase, which suggests an intercalation of actin between the phospholipid molecules. This effect seems to be more important for DMPE and DMPS than for DMPG, suggesting that the headgroup plays an important role in this intercalation. The critical surface pressure associated to the liquid expanded-liquid condensed (LE-LC) phospholipid transition increases with the concentration of G-actin and thus suggests that G-actin acts as an impurity, simply competing as a surfactant at the air-water interface. On the other hand, F-actin affects the LE to LC transition of phospholipids differently. In this case, the LE to LC transition is broader and F-actin slightly decreases the critical surface pressure, which suggests that electrostatic interactions are involved.

Actin Cytoskeleton↗
PubMed2004

Optimisation of a silicon/silicon dioxide substrate for a fluorescence DNA microarray.

This paper presents a comprehensive theory and experimental characterisation of the modulation of the fluorescence intensity by the construction of optical interferences on oxidised silicon substrates used for DNA microarrays. The model predicts a 90-fold variation of the fluorescence signal depending on the oxide thickness. For a Cy3 dye, the signal is maximal for a 90 nm oxide thickness corresponding to a 7.5-fold enhancement with respect to a standard glass substrate. For experimental validation of the model, we have prepared Si/SiO2 substrates with different parallel steps of decreasing oxide thicknesses on the same sample using a buffered oxide etch (BOE) etching process after thermal oxidation. The SiO2 surface has been functionalized by a silane monolayer before in situ synthesis of L185 oligonucleotide probes. After hybridisation with complementary targets, the variations of the fluorescence intensity versus oxide thickness are in very good accordance with the theoretical model. The experimental comparison against a glass substrate shows a 10-fold enhancement of the detection sensitivity. Our results demonstrate that a Si/SiO2 substrate is an attractive alternative to standard glass slides for the realisation of fluorescence DNA microarrays whenever detection sensitivity is an important issue.

Coated Materials, Biocompatible↗
PubMed1998

Interaction between G-actin and various types of liposomes: A 19F, 31P, and 2H nuclear magnetic resonance study.

We have investigated in the present study the interaction between G-actin and various types of liposomes, zwitterionic, positively charged, and negatively charged. To investigate at the molecular level the conformation of actin in the presence of lipids, we have selectively attached a fluorinated probe, 3-bromo-1,1,1-trifluoropropanone, to the actin cysteine residues 10, 285, and 374 and used high-resolution 19F nuclear magnetic resonance spectroscopy to investigate the probe resonances. The results indicate a change in the mobility of the 19F labels when G-actin is in the presence of positively charged liposomes made of DMPC and stearylamine and in the presence of DMPG, a negatively charged lipid. No conformational change was observed in the actin molecule in the presence of neutral liposomes. Electron micrographs of these systems reveal the formation of paracrystalline arrays of actin filaments at the surface of the positively charged liposomes, while no evidence of actin polymerization or paracrystallization was observed in the presence of DMPG. The interaction between actin and the lipid polar headgroup has also been investigated using solid-state phosphorus and deuterium NMR. The results indicate no evidence of interaction between actin and zwitterionic liposomes but show an interaction between the positively charged liposomes and a negative charge on the actin molecules. Interestingly, the negatively charged liposomes interact with a positive charge, which is most likely associated with the three residues (His-Arg-Lys) preceding the cysteine 374 residue in the protein.

Acetone↗
PubMed1988

Cardiac arrhythmias during the combined use of intravenous aminophylline and terbutaline in status asthmaticus.

The purpose of this study was to evaluate prospectively the occurrence of cardiac arrhythmias during the combined therapy with intravenous aminophylline and terbutaline in 29 consecutive patients with status asthmaticus. The 24-hour Holter recordings were performed during continuous intravenous infusions of aminophylline (0.56 +/- 0.20 mg/kg/h) and terbutaline (0.034 +/- 0.014 microgram/kg/min). Serum theophylline concentration was 12.1 +/- 3.8 micrograms/ml and never reached the toxic level (greater than 20 micrograms/ml). Premature ventricular contractions (PVCs) were absent in 35 percent of patients and 48 percent had rare unifocal PVCs (less than 10/h). Only 17 percent of patients (five of 29) exhibited severe ventricular arrhythmias: PVCs greater than 10/h (n = 3), multifocal PVCs (n = 1); and a short run of ventricular tachycardia (n = 1). Serious supraventricular arrhythmias occurred in only 7 percent of patients (two of 29) who developed sustained runs of atrial tachycardia. These arrhythmias were always clinically well tolerated and spontaneously resolved without any antiarrhythmic treatment. We conclude that severe arrhythmias are rarely observed during combined therapy with aminophylline and terbutaline in status asthmaticus.

Adult↗
PubMedDate not supplied

[Acute myocarditis disclosing leptospirosis].

A 44 year old patient presents with acute myocarditis and cardiogenic shock. The evolution is progressively favorable at the price of a residual involvement of the left ventricular function, evolving to a dilated cardiopathy, within three years. The responsibility of an advanced ictero-hemorrhagic leptospirosis is established. The severity of this myocarditis and the revealing characteristics of the leptospirosis are peculiar to this observation which is discussed in terms of data from the literature.

Acute Disease↗