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Biomedical subjects

O Bertrand

Publications and source records attributed to O Bertrand.

At least 73 records · Page 4Linked to original sources
PubMed1994

Two auditory components in the 130-230 ms range disclosed by their stimulus frequency dependence.

The auditory P2 wave has been studied by means of scalp potential and scalp current density (SCD) mapping. Two components were described. One, peaking around 150 ms, probably reflects a major activity in both supra temporal planes as revealed by SCD maps (P150). The other is a bilateral temporo-parietal component peaking around 220 ms (P220). These two components were functionally disclosed by their stimulus frequency dependence. The P150 potential and SCD amplitudes significantly decrease with increasing frequencies. Whereas this could be interpreted as a modulation of the neural activity, it may also be related to a tonotopical organization of the underlying generators distinct from that previously found for the N100. No frequency effect was found on P220.

Adult↗
PubMed1994

Chromatography of human immunoglobulin G on immobilized drimarene rubine R/K-5BL. Study of mild, efficient elution procedures.

A range of substances were screened to find eluents for human immunoglobulin G (IgG) which are retained with a strong affinity by immobilized Drimarene Rubine R/K-5BL. The strong affinity of IgG for the dye is partly due to the presence of copper in the dye. This was suggested by the effect of substances able to make coordination bonds with metals that elute the IgG and also the effect of metal stripping from the immobilized dye. Several mobile phase conditions were found that allowed desorption of retained IgG on immobilized Drimarene Rubine R/K-5BL without using a protein denaturant. A procedure was also devised for separating IgG2 from other IgG subclasses using chromatography on immobilized Rubine R/K-5BL and column development with an AMP gradient.

Amines↗
PubMed1994

Aspergillus fumigatus metalloproteinase that hydrolyses native collagen: purification by dye-binding chromatography.

A proteinase was purified from the human pathogenic fungus Aspergillus fumigatus. The four chromatographic steps, a "negative" dye column, a "positive" dye column, hydroxyapatite Ultrogel, and modified TSK gel (HW 55), gave a 14% overall yield. The protein migrated as a single band on SDS-PAGE and isoelectric focusing, with an M(r) of 82,000 and a pI of 5.6. Inhibitor studies suggested that the enzyme was a metalloproteinase. It hydrolyzed phenylazobenzyloxycarbonyl-Pro-Leu-Gly-Pro-Arg and cleaved native rat type I collagen.

Amino Acid Sequence↗
PubMed1994

Toxicity studies on native Procion Red HE-3B and released dye from affinity material exposed to degradative chemical conditions.

Leached ligands from chromatographic packing material submitted to drastic regeneration conditions can contaminate pure biological preparations. These contaminants could have adverse effects from a toxicology point of view that are very poorly documented in liquid chromatography for protein separation. Investigations on toxicity level have been made on released material from immobilized Procion Red HE-3B, after formal identification of the nature of the leached chemical material. Toxicity investigations in vitro involved a number of tests on living cells (eucaryotic and procaryotic) covering different aspects. Behaviour of cells in regular cultures, polyploïdia induction, genotoxicity as well as mechanisms of endocytosis have been studied. Results showed no toxic effects within the range of concentration of dye and dye derivatives studied. Genotoxicity studies in particular did not show any toxic effect over a range of concentration much higher than the regular level of dye leakage from the sorbent.

Cell Division↗
PubMed1994

Influence of the size of the polar head of non-ionic detergents on membrane proteins immunoaffinity purification.

Nonionic polyoxyethylene type detergents (CxEy) are widely used to solubilize and purify membrane proteins. The detergent hydrophobic moiety (Cx) replaces phospholipids at exposed hydrophobic regions of the membrane proteins. During chromatography on an immobilized anti-Kell antibody to purify Kell protein (an integral erythrocyte protein), it was observed that the size of the polar head of an non ionic detergent added to the mobile phase appeared to influence the interaction of the detergent-protein complex with the immobilized antibody. Further studies were performed using another erythrocyte membrane protein, Glycophorin C and three anti-GPC monoclonal antibodies directed against three epitopes of the extracytoplasmic domain of the protein. The interaction of GPC with the three Protein A-coupled monoclonal antibodies was studied in the presence of three detergents C12E<9>, C13E<15> and C12E<23>. It was observed in batch mode and in column chromatography experiments that the adsorption of GPC to the immunoaffinity supports decreased as the size of the detergent polar head increased. Thus, the polyoxyethylene chain of a detergent might prevent the interaction of the detergent-protein complex with the immobilized antibody.

Animals↗
PubMed1994

Time-frequency digital filtering based on an invertible wavelet transform: an application to evoked potentials.

This paper presents a method to analyze and filter digital signals of finite duration by means of a time-frequency representation. This is done by defining a purely invertible discrete transform, representing a signal either in the time or in the time-frequency domain, as simply as possible with the conventional discrete Fourier transform between the time and the frequency domains. The wavelet concept has been used to build this transform. To get a correct invertibility of this procedure, we have proposed orthogonal and periodic basic discrete wavelets. The properties of such a transform are described, and examples on brain-evoked potential signals are given to illustrate the time-frequency filtering possibilities.

Brain↗
PubMed1994

Effects of glucose-to-lipid ratio and type of lipid on substrate oxidation rate in patients.

This study is an investigation into the effects of different carbohydrate-to-lipid ratios on CO2 production in postoperative patients and the determination of the substrate oxidation rates induced by long-chain triglycerides (LCT) or a mixture of long- and medium-chain triglycerides (MCT/LCT) at various carbohydrate-to-lipid ratios. Two groups of eight patients randomly received either LCT or MCT/LCT emulsions. Total caloric intake was set at the measured energy expenditure provided at three different glucose-to-lipid ratios (70:30, 50:50, 30:70). We used long-term indirect calorimetry with a mass spectrometer system and measurement of natural enrichment in 13C of expired CO2 and plasma glucose. The carbon dioxide production and minute ventilation were not different among the different glucose-to-lipid ratios, whatever the type of lipid. Increasing the lipid supply up to 70% of nonprotein caloric intake led to an only minor increase in lipid oxidation rate and thus to a net fat deposit. We conclude that large amounts of lipid (LCT or MCT/LCT) were not of interest in such patients.

Aged↗
PubMed1994

Toxicity studies on Reactive Blue-2 leached from affinity material exposed to extreme chemical conditions.

Toxicity effects related to leached ligands from affinity sorbents that can contaminate biological preparations were investigated in the particular case of immobilized Reactive Blue-2. Initially, identification of the real chemical structure of leached dye has been done by HPLC after incubation in extreme conditions. Toxicity investigations in vitro involving several well known tests showed no toxic effects within the studied range of dye concentration. Cell cultures behaved normally when the adhesion phase was successful; polyploidy induction in human cells by the native dye and its derivatives identified as possible leached material was very similar to standard cultures. Genotoxicity studies did not evidence any toxic effect in E. Coli cultures of dyes themselves or of the same dyes after metabolic activation.

Cell Adhesion↗
PubMed1993

Evaluation of several affinity chromatographic supports for the purification of maltose-binding protein from Escherichia coli.

To obtain affinity adsorbents with good mechanical resistance, suitable for the purification of maltose-binding protein (MBP) from Escherichia coli and genetically engineered proteins fused to MBP, a series of supports were prepared by grafting amylose on to agarose by different chemistries. Their capacities for MBP and their abilities to be used at relatively high flow-rates were examined. Efficient supports were most conveniently prepared by coupling amylose to epoxy-activated agarose in an aqueous-organic mixture.

ATP-Binding Cassette Transporters↗
PubMed1993

[Acetabulum without cement. Short-term results of a series of 112 threaded cups].

Between January 1982 and December 1987 we used 112 threaded acetabular cups in 102 patients undergoing total hip replacement. The clinical and radiographic results of 107 implants are reported in this survey. Using the functional grading of the hip advocated by Merle d'Aubigné and Postel, 62% can be classified as excellent, very good or good. On x-ray only 35% of the cups show neither radiolucency at the bone-implant interface nor migration of the component. There is a statistically significant correlation between a radiolucency in 2 of the 3 areas at the bone-implant interface and the clinical result. The revision rate for failure of the cup is 11.6% (13 implants). The actuarial survival of the threaded cup decreased from 0.95 in the 1st year to 0.75 in the 5th year after implantation. Analysis of our failures and of published data suggest that the problem lies in the lack of primary bone integration. We describe our difficulties in assessing risk factors, in interpreting the radiographs and in the intraoperative determination of component instability. The disappointing short term results have prompted us to abandon the use of threaded cups.

Acetabulum↗
PubMed1993

Metabolic effects of hemodialysis with and without glucose in the dialysate.

This study was conducted in eight acute renal failure patients undergoing mechanical ventilation to test if the addition of glucose in the dialysate prevents metabolic and hormonal changes induced by hemodialysis. Hemodialysis was performed with a bicarbonate dialysate, a polyacrilonitrile membrane and a continuous heparinization. Two four-hour hemodialysis sessions were performed in each patient: one without glucose (GFD) and one with glucose (GD) in the dialysate at a concentration close to each patient's initial plasma glucose concentration. Oxygen consumption and carbon dioxide elimination, glucose insulin, aceto-acetate and free fatty acids were measured before, during and after the sessions. Oxygen consumption and carbon dioxide elimination were measured with a system using a mass spectrometer. Hemodynamic state and temperature remained constant. Before hemodialysis, respiratory quotient (RQ) values were the same in both groups. There was no change in RQ during GD. There was a decrease in RQ during GFD. Glucose and insulin concentrations decreased during GFD and remained unchanged during GD. Aceto-acetate concentration remained constant under both conditions. Free fatty acids concentration increased to the same extent during GD and GFD. The authors conclude that the addition of glucose in the dialysate prevents the decrease in RQ induced by hemodialysis. This effect is most likely related to a decreased mobilization of non-glucidic fuels.

Acute Kidney Injury↗
PubMed1992

High-performance hydrophobic interaction chromatography of proteins on reversed-phase supports coated with non-ionic surfactants of polyoxyethylene type. Purification of a fungal aspartic proteinase.

On coating reversed-phase supports with polyoxyethylene-type non-ionic surfactants, proteins are no longer retained on such supports at moderate or low ionic strength, but they are retained at high ionic strength and can be desorbed by a decreasing ionic strength gradient. These reversibly modified supports were used for hydrophobic interaction chromatography (HIC). The proteins probably interact with the polyoxyethylene tail of the non-ionic surfactant while the hydrophobic part of the surfactant anchors the surfactant to the reversed-phase support by interactions with its alkane coverage. Although the interactions between non-ionic surfactant and reversed-phase support are non-covalent and the HIC mobile phases contained no surfactant, the modified columns were stable and could be used repeatedly. A surfactant-modified reversed-phase column provided a rapid, efficient, one-step purification of a fungal aspartic proteinase from a commercial crude preparation.

Aspartic Acid Endopeptidases↗
PubMed1992

Role of activator protein-1 and methylation function in 12-O-tetradecanoylphorbol-13-acetate--mediated inhibition of differentiation of Friend erythroleukemia cells.

Friend erythroleukemia cells (FELCs) differentiate after hexamethylene-bis-acetamide treatment. This differentiation is characterized by an increase in beta-globin gene expression that is followed by appearance of the hemoglobin. Phorbol-ester tumor promoters, such as 12-O-tetradecanoylphorbol-13-acetate (TPA), inhibit differentiation of TPA-sensitive cells but not TPA-resistant cells. We have shown that the increase in beta-globin expression is inhibited by TPA in a TPA-sensitive clone but not in a TPA-resistant clone. To study the molecular mechanisms of regulation of gene expression by TPA, we examined the possible involvement of gene methylation and the TPA-responsive element (TRE). Both clones showed similar patterns of methylation around the beta-globin gene. Moreover, TPA-induced TRE binding and TRE enhancer activity were similar in both variants. These results suggest that the TPA inhibition of induced differentiation may not be explained by regulation of the methylation state. The activator protein-1 also does not play a crucial role in the sensitivity of FELCs to TPA.

Animals↗
PubMed1992

Purification of erythrocyte protein 4.1 by selective interaction with inositol hexaphosphate.

Protein 4.1 is a multifunctional structural protein occupying a strategic position in the erythrocyte membrane. It is present in the erythrocyte membrane skeleton and in many nonerythroid cells. This report describes a novel method for purifying this protein based on its selective interaction with inositol hexaphosphate dimagnesium tetrapotassium salt. This interaction was discovered in the course of chromatography of high-salt extract of inside-out membrane vesicles on Procion orange MX-2R-Sepharose. The new procedure is simple and selective and produces protein 4.1 with better yield than that obtained with a previously published procedure. The purified protein 4.1 has the same immunoreactivity and the same alpha-chymotryptic digest profile as protein 4.1 purified by published methods and is fully functional in enhancing the interaction between F-actin and spectrin dimers.

Chemical Precipitation↗