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A Renault

Publications and source records attributed to A Renault.

34 records · Page 2Linked to original sources
PubMed1998

Characterization of the growth of 2D protein crystals on a lipid monolayer by ellipsometry and rigidity measurements coupled to electron microscopy.

We present here some sensitive optical and mechanical experiments for monitoring the process of formation and growth of two-dimensional (2D) crystals of proteins on a lipid monolayer at an air-water interface. The adsorption of proteins on the lipid monolayer was monitored by ellipsometry measurements. An instrument was developed to measure the shear elastic constant (in plane rigidity) of the monolayer. These experiments have been done using cholera toxin B subunit (CTB) and annexin V as model proteins interacting with a monosialoganglioside (GM1) and dioleoylphosphatidylserine (DOPS), respectively. Electron microscopy observations of the protein-lipid layer transferred to grids were systematically used as a control. We found a good correlation between the measured in-plane rigidity of the monolayer and the presence of large crystalline domains observed by electron microscopy grids. Our interpretation of these data is that the crystallization process of proteins on a lipid monolayer passes through at least three successive stages: 1) molecular recognition between protein and lipid-ligand, i.e., adsorption of the protein on the lipid layer; 2) nucleation and growth of crystalline patches whose percolation is detected by the appearance of a non-zero in-plane rigidity; and 3) annealing of the layer producing a slower increase of the lateral or in-plane rigidity.

Annexin A5↗
PubMed1998

Non-invasive continuous positive airway pressure in acute hypoxaemic respiratory failure--experience of an emergency department.

Non-invasive continuous positive airway pressure (CPAP) seems to decrease the need for intubation in patients with severe cardiogenic pulmonary oedema (CPO) in the intensive care unit. The goals of our study were to delineate indications for CPAP in the emergency department, and to confirm its usefulness in such a setting. We retrospectively assess the evolution of all patients ventilated under CPAP for an acute hypoxaemic respiratory failure over a 1-year period (n = 64 patients). Hypercarbia and respiratory acidosis were present in most patients with CPO (PaCO2 = 54.4+/-22.3 mmHg; pH = 7.27+/-0.13), according to respiratory exhaustion, although initial PaCO2 was low in the pneumonia group. There was a significant improvement of arterial blood gases after 1 hour of ventilation in the CPO group (PaO2 = 254.1+/-121.0 mmHg; PaCO2 = 44.0+/-12.6 mmHg; pH = 7.34+/-0.08; p < 0.0001 for both parameters). In the pneumonia group, oxygenation was also improved but with the persistence of a significant shunt (PaO2 = 157.6+/-84.4 mmHg). Fifty-four patients (84%) were considered as successfully ventilated under CPAP, with no need for intubation and a favourable evolution, mainly in the CPO group. No side effects were reported. In conclusion, CPAP is a useful and easy-to-use ventilatory device in the emergency department. It is now one of our first line treatments during prehospital and emergency care of patients with CPO.

Acute Disease↗
PubMed1997

[Use of helium-oxygen gas mixtures in acute obstructive respiratory insufficiencies].

Therapeutic use of helium has been described since 1930. Its main action is to reduce bronchial resistances and consequently overall respiratory work. Helium is substituted for nitrogen. The effects of inhaling a helium-oxygen mixture result exclusively from the physicochemical properties of helium: very low density, high kinetic viscosity. With the advent of selective bronchodilators, use of helium was rapidly abandoned until recently with new interest for the treatment of severe acute asthma. We review the literature on the physical properties of helium-oxygen mixtures and propose an analysis of their therapeutic use in severe acute asthma as well as other indications such as acute episodes of obstructive bronchopneumonia and obstruction of the upper airways. Due to the non-invasive nature of this technique, its easy use with spontaneous ventilation and the large body of theoretical data emphasizing its adaptation for therapeutic use, helium-oxygen gas mixtures offer an important therapeutic option for treating severe diseases with poor prognosis. A multicentric national study is under way to validate its use early by emergency ambulatory units for the treatment of severe acute asthma.

Acute Disease↗
PubMed1976

[Abnormal pulmonary venous return from the right lung into the inferior vena cava or scimitar syndrome. 2 cases: hemodynamic study and surgical correction].

Two cases of abnormal venous return from the right lung into the inferior vena cava, or the scimitar syndrome, have been studied. The essential features of this condition are given, emphasis being laid on the haemodynamic findings. Surgical correction of the abnormal pulmonary venous return seems to be a logical solution when the left-right shunt is of significant size.

Adult↗