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Biomedical subjects

A Renault

Publications and source records attributed to A Renault.

At least 19 recordsLinked to original sources
PubMed2005

Prevention of venous thrombosis in patients with acute intracerebral hemorrhage.

OBJECTIVE: To assess intermittent pneumatic compression (IPC) in the prevention of venous thromboembolism (VTE). METHODS: The authors randomly allocated patients with a documented intracerebral hemorrhage (ICH) to elastic stockings (ES) alone or combined with IPC. The primary outcome was a combined criteria assessed at day 10: a symptomatic and well-documented VTE, or a death arising before day 10 and related to pulmonary embolism (PE), or an asymptomatic deep vein thrombosis (DVT) of the lower limbs detected by compression ultrasonography (CUS). Outcome assessment was blinded. RESULTS: One hundred fifty-one patients were randomized; 133 (88%) patients were evaluated at day 10. No clinical suspicion of VTE arose before day 10. Fourteen patients died before having a CUS but no death was definitely related to PE. Fourteen asymptomatic DVT were detected by CUS: three (4.7%) in the ES + IPC group (all distal) and 11 (15.9%) in the ES group (three proximal and eight distal). ES combined with IPC is associated with a reduced risk of asymptomatic DVT compared to ES alone: relative risk, 0.29 (95% CI 0.08 to 1.00). CONCLUSIONS: Asymptomatic deep vein thrombosis (DVT) was detected at day 10 in 15.9% of patients wearing elastic stockings alone. Intermittent pneumatic compression significantly decreased the occurrence of asymptomatic DVT for patients with intracerebral hemorrhage.

Acute Disease↗
PubMed2005

The conserved N-terminal region of the mitotic checkpoint protein BUBR1: a putative TPR motif of high surface activity.

BUBR1, a key component of the mitotic spindle checkpoint, is a multidomain protein kinase that is activated in response to kinetochore tension. Although BUB1 and BUBR1 play an important role in cell division, very little is known about their structural characteristics. We show that the conserved N-terminal region of BUBR1, comprising residues 1-204, is a globular domain of high alpha-helical content ( approximately 60%), stable in the pH range 4-9 and probably organized as a tetratricopeptide motif repeat (TPR), most closely resembling residues 16-181 of protein phosphatase 5. Because the latter presents a continuous amphipathic groove and is regulated by binding certain fatty acids, we compared the properties of BUBR1(1-204) and TPR-PP5(16-181) at air/water interfaces and found that both proteins exhibited a similar surface activity and formed stable, rigid monolayers. The deletion of a region that probably comprises several alpha-helices of BUBR1 indicates that long-range interactions are essential for the stability of the N-terminal domain. The presence of the putative TPR motif strongly suggests that the N-terminal domain of BUBR1 is involved in direct protein-protein interactions and/or protein-lipid interactions.

Amino Acid Motifs↗
PubMed2004

Organization and orientation of amphiphilic push-pull chromophores deposited in Langmuir-Blodgett monolayers studied by second harmonic generation and atomic force microscopy.

Orientation and organization of two amphiphilic push-pull chromophores mixed with two phospholipids (dipalmitoylphosphatidylcholine and dioleoylphosphatidylcholine) in Langmuir-Blodgett (LB) monolayers are investigated by second harmonic generation. The LB monolayers have also been characterized by atomic force microscopy and UV-vis spectroscopy. The effective molecular orientations and hyperpolarizabilities of the chromophores are studied as a function of the phospholipid concentrations. The experimental results are discussed within the frame of a model of orientational distribution of the chromophores which gives the orientational mean angle and bounds on the orientational disorder. The mean orientation of the chromophores is found to be within 45-55 degrees whereas their hyperpolarizability coefficients, measured with respect to quartz, are estimated to be in the range (0.3-0.7) x 10(-27) esu taking account of the maximal orientational disorder.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2003

[Acute colonic pseudo-obstruction (Ogilvie's syndrome) in pneumococcal meningo-encephalitis treated with neostigmine].

We report the case of a 71-year-old man with acute colonic pseudo-obstruction that complicates a pneumococcal meningo-encephalitis. After 48 h of conservative management with nothing by mouth, nasogastric suction, fluid and electrolyte correction, withdrawal of any anticholinergic agents, a pharmacological approach with 2 mg of neostigmine was successful in intensive care unit. This treatment was effective in over 80% of patients of recent reports. Neostigmine might be considered as first-line therapy in patients who do not have major contraindications to its use, because of less frequent iatrogenic risk than colonoscopic decompression or surgery.

Aged↗
PubMed2003

Aggregation of puroindoline in phospholipid monolayers spread at the air-liquid interface.

Puroindolines, cationic and cystine-rich low molecular weight lipid binding proteins from wheat seeds, display unique foaming properties and antimicrobial activity. To unravel the mechanism involved in these properties, the interaction of puroindoline-a (PIN-a) with dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) monolayers was studied by coupling Langmuir-Blodgett and imaging techniques. Compression isotherms of PIN-a/phospholipid monolayers and adsorption of PIN-a to lipid monolayers showed that the protein interacted strongly with phospholipids, especially with the anionic DPPG. The electrostatic contribution led to the formation of a highly stable lipoprotein monolayer. Confocal laser scanning microscopy and atomic force microscopy showed that PIN-a was mainly inserted in the liquid-expanded phase of the DPPC, where it formed an aggregated protein network and induced the fusion of liquid-condensed domains. For DPPG, the protein partitioned in both the liquid-expanded and liquid-condensed phases, where it was aggregated. The extent of protein aggregation was related both to the physical state of phospholipids, i.e., condensed or expanded, and to the electrostatic interactions between lipids and PIN-a. Aggregation of PIN-a at air-liquid and lipid interfaces could account for the biological and technological properties of this wheat lipid binding protein.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2003

Elasticity and plasticity of two-dimensional amorphous solid layers of beta-lactoglobulin.

We investigate the mechanical properties of a two-dimensional amorphous solid. It is formed spontaneously by the adsorption of a protein (the beta-lactoglobulin) at the surface of water. We measure its mechanical response in both elastic and plastic regimes by applying a point-like force (using a glass fiber). We compare our results with previous measurements of shear moduli using a floating torsion device.

Computer Simulation↗
PubMed2001

Two-dimensional crystallization of a membrane protein on a detergent-resistant lipid monolayer.

Two-dimensional crystals of a membrane protein, the proton ATPase from plant plasma membranes, have been obtained by a new strategy based on the use of functionalized, fluorinated lipids spread at the air-water interface. Monolayers of the fluorinated lipids are stable even in the presence of high concentrations of various detergents as was established by ellipsometry measurements. A nickel functionalized fluorinated lipid was spread into a monolayer at the air-water interface. The overexpressed His-tagged ATPase solubilized by detergents was added to the subphase. 2D crystals of the membrane protein, embedded in a lipid bilayer, formed as the detergent was removed by adsorption. Electron microscopy indicated that the 2D crystals were single layers with dimensions of 10 microm or more. Image processing yielded a projection map at 9 A resolution, showing three well-separated domains of the membrane-embedded proton ATPase.

Adsorption↗
PubMed2001

Use of buserelin to induce ovulation in the cyclic mare.

Inducing ovulation in a cyclic mare is often necessary. For this purpose, hCG has been used commonly, but the response can be reduced after successive administrations. The aims of this study were to test the effectiveness of buserelin in hastening ovulation in estrus mares, and its influence on fertility; and to investigate the effect of treatment on LH secretion. Five crossover trials were designed to compare the effect of two treatments: buserelin (40 microg in 4 doses i.v. at 12 h intervals) vs placebo (Experiments 1 and 2); buserelin 40 microg (in 4 doses i.v.) vs 20 microg (Experiment 3); buserelin (4 doses of 20 microg i.v.) vs hCG (1 dose of 2,500 IU i.v.) (Experiment 4); or buserelin (3 doses of 13.3 microg at 6 h interval) vs hCG (Experiment 5). In Experiment 2, blood samples were taken hourly until ovulation, for LH measurements. In Experiment 1, buserelin treatment significantly hastened ovulation. Reduction of the dose by half (Experiment 3) did not alter the effectiveness. In Experiments 4 and 5, buserelin was as effective as hCG in inducing ovulation between 24 and 48 h after initiation of treatment. Buserelin treatment induced a rise in LH concentration during the 48 h period of the experiment, and LH concentrations before ovulation were significantly higher in buserelin treated cycles than in placebo cycles. These experiments demonstrated the usefulness of two new protocols of administration of buserelin, as an alternative to hCG for induction of ovulation. One hypothesis explaining the mechanism of action is that the persistant rise in LH concentration could modify the ratio of biological/immunological LH, as it occurs physiologically, thereby hastening ovulation.

Animals↗
PubMed2001

Modification of bovine beta-lactoglobulin by glycation in a powdered state or in aqueous solution: adsorption at the air-water interface.

The adsorption at the air-water interface of native and various glycated forms of beta-Lactoglobulin B (beta-LG), prepared under two different experimental conditions, was investigated by ellipsometry, surface tension and shear elastic constant measurements. The measurements were performed in 0.1 M phosphate buffer, 0.1 M NaCl, pH 6.8. It was found that the interfacial properties of beta-LG were more affected when the glycation was performed in solution than in the dry-way system. Dry-way glycated beta-LG, despite a higher glycation extent, affected slightly its interfacial behaviour. Solution glycated beta-LG exhibited a higher adsorption and more rigid interface as expressed by shear elastic constant measurement at saturation (16.5 mN/m against 8.7 and 11.5 mN/m for native and control treated beta-LG, respectively). These results were attributed to the specific molecular species induced during glycation in solution, which includes monomers and unfolded covalent homodimers of beta-LG molecules with a high tendency to self-association via non-covalent interactions.

Journal Article↗
PubMed2001

Biphasic-flow induced ventilation allows simultaneous ventilation in several animals, using a single multiple output ventilator--a preliminary report.

Biphasic-flow induced ventilation (BiFIV) is a variable time-cycled tracheal gas insufflation mode, using a specific multiluminal endotracheal tube. Some recent studies have reported efficiency of this new ventilatory mode in experimental in vitro and in vivo settings. We hypothesized that this ventilatory mode could be able to deliver simultaneous efficient ventilation for several animals, using a single ventilator prototype. The study was performed in three groups of three domestic pigs with a normal lung compliance. Each pig was initially anaesthetized, intubated with the specific endotracheal tube, and ventilated with a conventional ventilatory device. The animals were then simultaneously ventilated under BiFIV, using a single ventilator prototype, for each group of three animals. Physiological parameters and arterial blood gases were recorded at each study phase. All animals but one survived the experiment. We did not observe any significant differences in arterial gas exchange, under both ventilatory modes. Oxygenation was as efficient for each three animals ventilated under BiFIV, using a single ventilator device, as under conventional ventilation, using three separate ventilators (PaO2 = 112+/-17 mmHg under conventional ventilation versus 115+/-16 mmHg under BiFIV). In conclusion, variable time-cycled tracheal gas insufflation may allow an efficient multiple ventilation on several animals, using a single multiple output ventilatory device, in a normal lung animal model. If validated on subsequent pathological models, it could thus be interesting in laboratory and/or mass casualty situations.

Animals↗
PubMed2000

Interaction of the third helix of Antennapedia homeodomain and a phospholipid monolayer, studied by ellipsometry and PM-IRRAS at the air-water interface.

The penetratin peptide, a 16 amino acid sequence extracted from Antennapedia homeodomain, is able to translocate across a neural cell membrane through an unknown mechanism, most likely a non-specific interaction with membrane lipids. Beyond its potential application as vector targeting small hydrophilic molecules and enabling them to reach a cell nucleus, this observation raises intriguing questions concerning the physico-chemistry of peptide-lipid interactions. Here we present a study of the role of lipid surface pressure and head charge on the mechanism of interaction. This was performed using optical techniques: surface infrared spectroscopy and ellipsometry, applied to a monolayer of phospholipids deposited at the air-water interface. Determination of the structure and orientation of peptides and lipids (separately or together) evidenced that electrostatic rather than amphiphilic interactions determine the peptide adsorption and its action on lipids.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2000

Synchrotron radiation diffraction from two-dimensional protein crystals at the air/water interface.

Protein structure determination by classical x-ray crystallography requires three-dimensional crystals that are difficult to obtain for most proteins and especially for membrane proteins. An alternative is to grow two-dimensional (2D) crystals by adsorbing proteins to ligand-lipid monolayers at the surface of water. This confined geometry requires only small amounts of material and offers numerous advantages: self-assembly and ordering over micrometer scales is easier to obtain in two dimensions; although fully hydrated, the crystals are sufficiently rigid to be investigated by various techniques, such as electron crystallography or micromechanical measurements. Here we report structural studies, using grazing incidence synchrotron x-ray diffraction, of three different 2D protein crystals at the air-water interface, namely streptavidine, annexin V, and the transcription factor HupR. Using a set-up of high angular resolution, we observe narrow Bragg reflections showing long-range crystalline order in two dimensions. In the case of streptavidin the angular range of the observed diffraction corresponds to a resolution of 10 A in plane and 14 A normal to the plane. We show that this approach is complementary to electron crystallography but without the need for transfer of the monolayer onto a grid. Moreover, as the 2D crystals are accessible from the buffer solution, the formation and structure of protein complexes can be investigated in situ.

Air↗
PubMed2000

Acute metobromuron poisoning with severe associated methemoglobinemia. Identification of four metabolites in plasma and urine by LC-DAD, LC-ESI-MS, and LC-ESI-MS-MS.

A case of self poisoning with metobromuron, a urea derivative used as a herbicide, is reported. Severe methemoglobinemia observed at the admission (80%) disappeared only at day 11, and hemolysis appeared at day 4 and decreased slowly to day 12. Metobromuron was analyzed by liquid chromatography with diode-array detection. Initial plasma concentration and elimination half-life were 4.9 mg/L and 5 h, respectively. Several metabolites were also detected, and four of those were identified by liquid chromatography-electrospray mass spectrometry. Normetobromuron, bromophenylurea, and bromoacetanilide were detected in plasma, but only N-methyl bromophenylurea was detected in urine. Bromoacetanilide probably results from acetylation of the intermediate bromoaniline. Methemoglobinemia could result from metabolization of metobromuron to bromoaniline and bromoacetanilide.

Acetanilides↗
PubMed1999

Surface-induced polymerization of actin.

Living cells contain a very large amount of membrane surface area, which potentially influences the direction, the kinetics, and the localization of biochemical reactions. This paper quantitatively evaluates the possibility that a lipid monolayer can adsorb actin from a nonpolymerizing solution, induce its polymerization, and form a 2D network of individual actin filaments, in conditions that forbid bulk polymerization. G- and F-actin solutions were studied beneath saturated Langmuir monolayers containing phosphatidylcholine (PC, neutral) and stearylamine (SA, a positively charged surfactant) at PC:SA = 3:1 molar ratio. Ellipsometry, tensiometry, shear elastic measurements, electron microscopy, and dark-field light microscopy were used to characterize the adsorption kinetics and the interfacial polymerization of actin. In all cases studied, actin follows a monoexponential reaction-limited adsorption with similar time constants (approximately 10(3) s). At a longer time scale the shear elasticity of the monomeric actin adsorbate increases only in the presence of lipids, to a 2D shear elastic modulus of mu approximately 30 mN/m, indicating the formation of a structure coupled to the monolayer. Electron microscopy shows the formation of a 2D network of actin filaments at the PC:SA surface, and several arguments strongly suggest that this network is indeed causing the observed elasticity. Adsorption of F-actin to PC:SA leads more quickly to a slightly more rigid interface with a modulus of mu approximately 50 mN/m.

Actins↗
PubMed1998

[Spontaneous positive end-expiratory pressure ventilation in elderly patients with cardiogenic pulmonary edema. Assessment in an emergency admissions unit].

OBJECTIVES: Intubation and ventilatory assistance are often required in patients presenting severe hypoxemic respiratory distress, but may be contraindicated in elderly subjects due to an underlying condition. The aim of this study was to assess the feasibility, acceptability and contribution of early assistance with spontaneous positive end-expiratory pressure ventilation for elderly subjects admitted to an emergency unit for acute respiratory distress due to cardiogenic pulmonary edema. PATIENTS AND METHODS: In our emergency admission unit, all patients with life-threatening hypoxemic respiratory distress are initially assisted with noninvasive spontaneous positive end-expiratory pressure ventilation using a standardized commercial device. We retrospectively analyzed the the files of all patients aged over 70 years who were treated with this standard protocol for cardiogenic pulmonary edema from April 1996 through September 1997. RESULTS: During the study period, 36 patients aged over 70 years required ventilatory assistance according to the standard protocol. Intubation was not reasonable in most of the patients (n = 30). After 1 hour of ventilation, none of the patients developed clinical signs of life-threatening distress. Blood gases demonstrated improved oxygenation (AEPO2 = +184.9 +/- 105.4 mmHg; p < 0.000001). Thirty-two patients were considered to be cured (88.9%) and were discharged; the cardiovascular condition was fatal in 4 patients (11.1%). CONCLUSION: The rapid improvement in clinical signs and blood gases as well as the final outcome suggests that early assistance with spontaneous positive end-expiratory pressure ventilation is warranted at admission for elderly patients with respiratory distress due to cardiogenic pulmonary edema. Compared with a control group of hospitalized patients cared for during the preceding year and who were not treated with the standard protocol, we also demonstrated a clear improvement in mortality (11% versus 20%).

Admitting Department, Hospital↗