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S Gaillard

Publications and source records attributed to S Gaillard.

At least 19 recordsLinked to original sources
PubMed1992

Dantrolene inhibits halothane-induced membrane reorganization. A study using 31P-NMR and differential scanning calorimetry.

The action of the relaxing agent dantrolene on dipalmitoylphosphatidylcholine (DPPC) model membranes in the presence and absence of the general anesthetic halothane has been investigated by DSC and 31P-NMR. Dantrolene has a weak effect on both the thermodynamic and NMR parameters of the pure model membrane. When halothane is present in the system, the relaxing agent acts to counterbalance the strong anesthetic-induced membrane perturbation. This is reflected in DSC experiments by a change of the enthalpy variation (delta H) and of the main gel-to-fluid phase transition temperature (Tc) towards the values of the pure lipid system. The amount of halothane-induced small tumbling vesicles, as detected by 31P-NMR by the superposition of an isotropic line on a lamellar-type powder spectrum, is considerably reduced upon dantrolene addition. This means that the relaxing agent "cures" the membrane de-structuring action promoted by halothane. Membranes first treated with dantrolene are also protected from the halothane perturbation. So, the relaxing agent is both "curative" and "preventative" against halothane. The optimum effect is obtained for 1 dantrolene molecule per ca 34 halothane molecules. The mechanisms of action were discussed in relation to membrane fluidity.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

31P NMR and freeze fracture studies of sarcoplasmic reticulum membranes from normal and malignant hyperthermic pigs: effect of halothane and dantrolene.

The effects of halothane and dantrolene on sarcoplasmic reticulum membranes isolated from normal and malignant hyperthermia pig muscle have been investigated using 31P NMR and freeze fracture electron microscopy. The dynamical and structural changes are estimated from the second moment, as calculated from 31P NMR spectra. For both membranes, addition of halothane induces a similar decrease in the spectral second moment. At high concentration of halothane, freeze fracture replicas show small unilamellar vesicles or mixed micelles, uniformly sprayed in the case of malignant hyperthermia membranes but mainly aggregated for the normal ones. The effect of halothane on both membranes is partially inhibited by adding dantrolene. These results suggest that (i) the malignant hyperthermia syndrome is not directly related to the polar heads of phospholipids and (ii) dantrolene counteracts unspecifically the disturbing effect of halothane at the lipid level.

Animals↗
PubMed1991

Halothane-induced membrane reorganization monitored by DSC, freeze fracture electron microscopy and 31P-NMR techniques.

The effect of the volatile anaesthetic halothane on the structure and dynamics of lipid multilayers (dimyristoyl- and dipalmitoylphosphatidylcholine, DM- and DP-PC, aqueous dispersions) was studied using Differential Scanning Calorimetry (DSC), Freeze Fracture Electron Microscopy and solid state phosphorus-31 Nuclear Magnetic Resonance (31P-NMR). The action of the drug depends upon the halothane-to-lipid molar ratio, Ri, and temperature. With DPPC lipids, three main regions can be distinguished: i) 0 less than Ri less than 0.7, ii) 0.7 less than Ri less than 2 and iii) Ri greater than 2. As Ri increases in the first region, a linear decrease in the main gel-to-fluid phase transition temperature (Tc), a broadening in the DSC transition peak and a lowering in the enthalpy variation (delta H), are observed. A minimum in delta H is reached at Ri = 0.7. In this region, 31P-NMR spectra indicate that the multibilayer structure is maintained. In the second region, Tc still decreases with the same slope, but delta H increases up to a plateau value for Ri = 2. In the lipid fluid phase, an isotropic NMR line appears superimposed on the powder pattern that corresponds to a lamellar phase. For Ri greater than 2, Tc and delta H remain almost constant. At values of temperature that are greater than Tc, a growing isotropic line occurs in 31P-NMR spectra. This means a new supramolecular structure made of lipids and halothane is stabilized. This structure has been characterized as small vesicles of about 400 A to 600 A diameter by Freeze Fracture electron microscopy observations. With DMPC and low ratios (Ri less than or equal to 2), DSC and NMR results are similar to those obtained for DPPC. However, the minimum delta H is reached at Ri = 0.2 and the decrease in Tc is faster than for DPPC when Ri increases from 0. For Ri greater than 2, while Tc and delta H remain constant as in the case of DPPC, 31P-NMR spectra of DMPC systems show a superimposition of an isotropic line and two powder patterns, which correspond to small tumbling vesicles, a possible hexagonal phase and a lamellar phase respectively. Halothane, thus acts on model membranes in two different steps: at low Ri the bilayer is disturbed but keeps its structure. Whereas for higher drug concentrations, a new organization of lipids seems to be stabilized for T greater than Tc.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1991

[Pulmonary hemosiderosis. Hemodynamic or idiopathic origin? Diagnostic contribution of imaging and review of the literature].

We report two cases of Pulmonary Hemosiderosis. The first patient (adult male) had an angiosarcoma of the left auricle and developed pulmonary arterial hypertension, was treated by surgery and chemotherapy. The other patient (adult female) suffered from Idiopathic Pulmonary Hemosiderosis (IPH) and had been treated by corticosteroids for fifteen years, with one acute episode during this period. We discuss the etiological diagnosis and the contribution of chest radiographs, CT-scan and MR Imaging in this rare illness according to literature. IPH occurs mostly in childhood with acute and fatal issue, whereas presents as a chronic form in adults. Assessment of IPH requires large investigations to eliminate hemodynamic, hemato-, immuno-, carcinological disorders, and infectious agents as well. Review.

Adult↗
PubMed1990

Ionic control of intracellular pH in rat cerebellar Purkinje cells maintained in culture.

1. Intracellular pH (pHi) was measured in single rat cerebellar Purkinje cells maintained in primary culture using microspectrofluorescence analysis of the intracellularly trapped pH-sensitive dye 2',7'-bis-(2-carboxyethyl)-5 (and -6)-carboxyfluorescein (BCECF). 2. The ratio of the fluorescence signals measured at 530 nm in response to an alternating excitation at 450 and 490 nm was calibrated using the K(+)-H+ ionophore nigericin. This calibration gave a steady-state pHi of 7.06 +/- 0.02 (S.E.M., n = 17) when cells were perfused by a 5% CO2-25 mM-HCO3(-)-buffered solution at an external pH of 7.40 at 37 degrees C. 3. Replacement of external chloride with gluconate in the presence of bicarbonate induced a cytoplasmic alkalinization of about 0.3 pH unit. This alkalinization was independent of external sodium and was greatly reduced by 0.5 mM-DIDS, indicating the presence of a chloride-bicarbonate exchange. 4. In bicarbonate-free (HEPES-buffered) solution the steady-state pHi was 7.37 +/- 0.02 (n = 19), significantly higher than in bicarbonate-buffered solution. Recovery from an intracellular acid load brought about by the ammonium chloride pre-pulse technique was blocked by the removal of external sodium or the addition of 1.5 mM-amiloride, indicating the presence of a sodium-hydrogen exchange. 5. In bicarbonate-buffered solution pHi recovery after an acid load was also completely blocked by addition of 1.5 mM-amiloride indicating the absence of a bicarbonate-dependent acid extrusion mechanism. 6. Addition of 12-O-tetradecanoylphorbol-13-acetate (TPA, 100 nM) induced an amiloride-sensitive alkalinization of about 0.3 pH unit in bicarbonate-buffered solution but had no effect in HEPES-buffered solution. This observation suggests that in cultured Purkinje cells the sodium-hydrogen exchanger could be activated through a protein kinase C pathway only when pHi is maintained at a low physiological value by the activity of the chloride-bicarbonate exchange.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1990

[Congenital anomaly of the inferior vena cava with hemiazygos continuation. Ultrasonic diagnosis].

Congenital anomaly of the inferior vena cava with hemiazygos continuation: ultrasonic diagnosis. We report a case of agenesis of the retro-hepatic segment of the inferior vena cava in an asymptomatic 18 year old woman, found on a routine chest-ray. This rare illness was suspected on the findings of conventional radiology and was assessed by ultrasonography that shows direct termination of hepatic veins in the right auricle, and the hemi-azygos vein behind the aorta. Our radiological and ultrasonographic findings are confirmed by the literature. In the absence of any clinical signs, CT-scan and MR Imaging were note used in investigations. Nevertheless their usefulness has been extensively reported by many authors. Cavography remains useful before surgery.

Adolescent↗
PubMed1990

[Radiologic aspect of benign pleural fibrous mesothelioma. Reports of 4 cases].

Solitary fibrous tumor or pleural fibroma is a rare tumor. It grows slowly and has a good prognosis after surgical resection. Pleural features, staging and even the fibrous nature are analysed by radiological findings. Ultrasonic diagnosis, CT-Scan and MR Imaging are very useful but non specific: the differential diagnosis between benign and malignant tissue is still based on histological study of the whole surgical specimen. Review of the literature.

Adult↗
PubMed1989

Ehlers-Danlos syndrome, clotting disorders and muscular dystrophy.

Ehlers-Danlos syndrome includes 11 distinct entities. The diversity of this collagen dysplasia and its combination with other abnormalities make it difficult to understand physiopathologically. A case of Ehlers-Danlos syndrome is reported, which is novel owing to its combination with clotting abnormalities and especially with muscular dystrophy. To our knowledge this has not previously been reported. The patient was a young man aged 16 years who presented with Ehlers-Danlos syndrome satisfying Perelman's diagnostic criteria. His father and two brothers had comparable clinical symptoms, but his mother and sister were healthy. The four male subjects had an increased cephalin-kaolin time, reduced levels of factor VIII and Willebrand's factor (but without haemophilia A or Willebrand's disease), and, especially, an abnormal platelet ATP secretion. The proband alone had muscular disease with bilateral quadriceps fatigability and amyotrophy. The muscle enzyme levels were greatly increased, the electromyographic trace was myogenic, and the biopsy showed severe muscular dystrophy. This new observation poses the problem of the relation between clotting abnormalities and collagen abnormalities in the Ehlers-Danlos syndrome. It is difficult to classify this case within any of the 11 known types because of its muscular manifestations. It may perhaps be a fortuitous combination or an extension of the nosological framework of this syndrome.

Adenosine Triphosphate↗
PubMed1988

Survey of the folding pathway of a two-domain protein phosphoglycerate kinase.

The role of structural domains as folding units in the folding process which generates an active enzyme, is considered through several studies on phosphoglycerate kinase, a two-domain enzyme which catalyzes the first step of ATP production in glycolysis. The folding pathway was found to be a complex multi-step process, the C-terminal domain being more stable folding first. Inactive species originating from an intermediate in the folding pathway have been identified. Isolated domains recently obtained using genetic engineering are under investigation in our laboratory; this might probably allow to understand the way by which the N-terminal domain reaches its final native conformation and interacts with the other domain.

Animals↗
PubMed1985

[Hemorrheological changes in 50 monoclonal dysglobulinemias treated by plasma exchange].

Rheological examinations were performed before and after plasma exchanges in 50 patients with monoclonal dysglobulinaemia. The parameters investigated were blood and plasma viscosity, erythrocyte filtrability, erythrocyte aggregation and kinetics of agglutination. The results showed reduction of blood and plasma viscosity and improvement in agglutination kinetics under plasma exchanges. Rheological examinations therefore seem to be useful to follow up blood disorders, notably the hyperviscosity syndrome. They can be performed prophylactically, leading to early plasma exchanges to prevent clinical deterioration.

Blood Viscosity↗
PubMed1984

[Blood T lymphocyte populations in the hemophiliac].

We have studied a group of 31 hemophiliac patients (hemophilia A: 26 patients, hemophilia B: 5 patients); 29 healthy men were used as controls. Hemophiliac patients had increased percentages of suppressor T-lymphocytes and depressed T4/T8 ratios. These abnormalities were found to be significantly correlated with the amount of F VIII used per year.

Adolescent↗
PubMed1984

Experimental approach to rouleau formation. Comparison of three methods.

From a clinical point of view, the approach to erythrocyte aggregate or rouleau formation and cohesion is undeniably of great interest. A large number of methods have been suggested for studying this parameter such as: back-scattering of light, nephelometry, ultrasound, etc... In this paper the authors have compared three methods to approach rouleau formation: direct observation of rouleau formation (rheoscope); 'erythrocyte aggregometer': with this technique, the light transmitted by the sample is integrated over a period of time and provides an index (IA); laser reflectometer based on studying the light that is back-scattered by the blood sheared in the gap of a viscometer. The results show that the indexes measured by both reflexion and transmission vary according to hematocrit and reach a maximum value at hematocrit levels of between 30 and 40%. In contrast, observation using the rheoscope did not provide qualitative evidence of this phenomenon.

Blood Viscosity↗
PubMed1984

Investigation of human blood platelets with fluorescence spectroscopy.

Intramolecular excimer formation of dipyrenylpropane was investigated in human blood platelets. The ratio of the emission intensities of excimer to monomer (IE/IM) is sensitive to changes in lipidic membrane structure, induced by external perturbations, such as cholesteryl hemisuccinate introduction and temperature. Lack of reliable "microviscosities" determinations could be due to poor solubility of the probe in aqueous cells suspensions. Results were compared to those obtained with the fluorescence polarization technique.

Blood Platelets↗
PubMed1982

[Atypical osteodystrophy of visceral origin (author's transl)].

The authors report a case of atypical osteodystrophy of visceral origin (uretero-sigmoid by-pass for bladder exstrophy) which was characterized by the association of osteocondensation and looser-Milkman lines. They emphasize the rareness of osteodystrophy after uro-digestive by-pass and the exceptional character of the osteocondensation.

Acidosis↗
PubMed1982

Hemorheological and biochemical parameters in the "fatty" rat.

The essential part played by rheological factors in genesis of thrombosis and atherosclerosis has often been mentioned. Thus the authors have carried out a study of rheological and biochemical parameters on a genetic animal model with modifications in plasma lipids (homozygous obese "Fatty" rat) compared to the non obese heterozygous animal. The results obtained for the evolution of biochemical parameters (blood glucose, cholesterol, triglycerides) over a 16 months period confirm those published earlier. Further, a significant increase in fibrinogen level was observed in homozygous animals, and correlated with plasma viscosity. There results are also connected with changes in apparent blood viscosity which is considerably increased in homozygous rats, particularly at low shear rates (gamma less than 20 s-1). These results show the value of this animal model and the authors suggest the application of such a genetic animal model and of its heterozygous control population to both theoretical rheological and pharmacological studies on atherogenesis and hyperlipoproteinaemia.

Animals↗