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Biomedical subjects

O Bertrand

Publications and source records attributed to O Bertrand.

At least 19 recordsLinked to original sources
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↗
PubMed1992

Plasminogen receptors on rat colon carcinoma cells.

Cells from rat carcinoma cell lines PROb (giving progressive tumours) and REGb (giving regressive tumours) have cell surface receptors which bind specifically rat plasminogen and plasmin. Affinity for Pg was found to be higher in PROb (Kd = 10(-7) M) than in REGb cells (Kd = 5.10(-7) M) but with a concomitant decrease in the number of binding sites, 0.9 x 10(6)/cell (range from 0.6 to 1.2 x 10(6)) in PROb vs 3.6 x 10(6)/cell (range 1.2 to 6 x 10(6)) in REGb cells. The number and the affinity of binding sites varied in an opposite way in PROb and REGb cells. The difference in affinity parameters was unrelated to the degree of invasiveness of tumour cells in syngenetic rats. Bound plasmin retained its enzymatic activity, which indicates that its binding does not involve the catalytic active site. In cell solubilisates plasminogen receptor appeared as one major band situated in the area of 50-60 kDa.

Animals↗
PubMed1992

The combined monitoring of brain stem auditory evoked potentials and intracranial pressure in coma. A study of 57 patients.

Continuous monitoring of brainstem auditory evoked potentials (BAEPs) was carried out in 57 comatose patients for periods ranging from 5 hours to 13 days. In 53 cases intracranial pressure (ICP) was also simultaneously monitored. The study of relative changes of evoked potentials over time proved more relevant to prognosis than the mere consideration of "statistical normality" of waveforms; thus progressive degradation of the BAEPs was associated with a bad outcome even if the responses remained within normal limits. Contrary to previous reports, a normal BAEP obtained during the second week of coma did not necessarily indicate a good vital outcome; it could, however, do so in cases with a low probability of secondary insults. The simultaneous study of BAEPs and ICP showed that apparently significant (greater than 40 mm Hg) acute rises in ICP were not always followed by BAEP changes. The stability of BAEP's despite "significant" ICP rises was associated in our patients with a high probability of survival, while prolongation of central latency of BAEPs in response to ICP modifications was almost invariably followed by brain death. Continuous monitoring of brainstem responses provided a useful physiological counterpart to physical parameters such as ICP. Serial recording of cortical EPs should be added to BAEP monitoring to permit the early detection of rostrocaudal deterioration.

Adolescent↗
PubMed1992

Inhibitory effect of platelet factor 4 (PF4) on the growth of human erythroleukemia cells: proposed mechanism of action of PF4.

The effect of platelet factor 4 (PF4) on the growth of human erythroleukemia cell line (HEL) and the binding characteristics of iodine 125-labeled PF4 to cells were studied to determine the mechanism of action of PF4. HEL cells were cocultured with various doses of PF4 in either a plasma clot system for colony assay or a liquid system for tritiated thymidine incorporation. A significant inhibition of HEL colony growth and tritiated thymidine incorporation was seen at PF4 doses of 1 microgram/ml and 0.5 microgram/ml, respectively. The inhibitory effect of PF4 could be abrogated by the addition of heparin (5 to 10 micrograms/ml). Enzyme-linked immunosorbent assay showed that PF4 had no obvious effect on the expression of platelet glycoprotein IIb/IIIa of HEL cells. Binding of 125I-PF4 to HEL cells reached equilibrium within 20 to 30 minutes with dissociation constant of 1.3 x 10(-10)M and Bmax of 6.3 pmol/10(5) cells and was inhibited by an excess of unlabeled PF4, beta TG, and heparin but was not affected by PMA, IL-3, IL-6, GM-CSF, and interferon-alpha. PF4 did not affect the binding of 125I-IL-3 and 125I-IL-6 to HEL cells. These data demonstrate that PF4 inhibits the growth of HEL cells by specific binding to HEL cells and suggest that the action of PF4 may be associated with the heparin-binding sites of the molecule.

Cell Division↗
PubMed1991

The finite element method for a realistic head model of electrical brain activities: preliminary results.

In order to model the brain's electrical activity realistically, the finite element method has been used to compute the potential distribution due to a current dipole. This approach has the advantage over the boundary element method of being able to consider anisotropies of the different conducting sub-volumes. The forward solution has been evaluated in the particular case of a three-layer concentric sphere isotropic head model of the head where an analytical formula is known. The errors on the dipole position and orientation have been estimated in the inverse problem procedure.

Brain↗
PubMed1991

Abnormal vasomotor changes early after coronary angioplasty. A quantitative arteriographic study of their time course.

BACKGROUND: To study the impact of percutaneous transluminal coronary angioplasty (PTCA) on coronary vasomotion, we prospectively analyzed spontaneous changes in coronary diameter and the response to the cold pressor test and intracoronary nitroglycerin in 11 patients subjected to successful single-vessel PTCA. METHODS AND RESULTS: All antianginal medications were stopped 48 hours before each study. The minimum diameter of the PTCA segment and the diameter of a distal segment in the angioplastied vessel and of a segment in a control vessel not manipulated by the balloon catheter or guide wire were measured by computerized edge detection immediately before PTCA and 5 minutes after, 4 hours after, and 8 days after PTCA. At 4 hours, PTCA and distal segments were constricted by 38 +/- 9% and 16 +/- 5%, respectively, compared with the values at 5 minutes (p less than 0.01). Before angioplasty, the cold pressor test caused vasoconstriction of PTCA and distal segments by 23 +/- 6% (p less than 0.0001) and 15 +/- 4% (p less than 0.008), respectively, but no constrictor response was elicited at 5 minutes or 4 hours after angioplasty. Eight days after PTCA, the basal coronary diameters were similar to those observed 5 minutes after PTCA and the response to the cold pressor test was similar to that observed before PTCA. All segments dilated significantly with nitroglycerin at all times, and no vasoconstriction changes were found in the control segments. CONCLUSIONS: Four hours after PTCA, transient spontaneous vasoconstriction of the PTCA and distal segments occurs, which is so intense that the cold pressor test does not cause any further constriction. These abnormalities resolve within 8 days of PTCA.

Angioplasty, Balloon, Coronary↗
PubMed1990

Fibrin degradation products generation and fibrinopeptide A release in normal plasma incubated with thrombolytic agents: proposed mechanisms.

Clinical data have shown that the evaluation of fibrin degradation products (FbDP) does not reflect the efficiency of thrombolytic therapy in vivo. In this study, we found that the addition of plasminogen activators to normal plasma resulted in generation of FbDP and release of fibrinopeptide A (FpA) as shown by ELISA and HPLC. This FpA release was concomitant with fibrinogen degradation, and was not inhibited by thrombin inhibition or by prothrombin depletion in plasma. Thus, the increase in FpA did not result from coagulation activation and may result from the plasmin-induced release of FpA from fibrinogen degradation product E1. The generation of cross-linked FbDP after tPA addition occurred in normal plasma as well as in factor-XIII-deficient plasma and quickly reached a plateau. It was not inhibited by hirudin. Therefore FbDP in these plasmas probably derived from the plasmin degradation of cellular transglutaminase cross-linked fibrin/fibrinogen derivatives present in plasma.

Aprotinin↗
PubMed1990

Precautions in topographic mapping and in evoked potential map reading.

First, we consider the main points that must be addressed when constructing topographic maps: types of projection, methods of interpolation, number and locations of recording electrodes, and color scales. Data integrity and precautions in map interpretation are then examined for the case of evoked potential data.

Brain↗
PubMed1989

Spherical splines for scalp potential and current density mapping.

Description of mapping methods using spherical splines, both to interpolate scalp potentials (SPs), and to approximate scalp current densities (SCDs). Compared to a previously published method using thin plate splines, the advantages are a very simple derivation of the SCD approximation, faster computing times, and greater accuracy in areas with few electrodes.

Computer Simulation↗
PubMed1989

An efficient laboratory made apparatus for DNA amplification.

DNA amplification by the polymerase chain reaction (PCR) is a method capable of producing a selective and very high enrichment of a specific DNA sequence. Hence it seems to be useful in various fields from basic research to clinical applications. In order to automatize PCR we assembled for a very low cost a mechanical system designed to carry a test tube holder successively in three thermal baths set at the required temperatures for the reaction. Two examples of the use of this machine are given: (i) amplification of DNA of a particular subtype of acute intermittent porphyria; (ii) the detection of the chimeric c-abl/bcr message found in chronic myelogenous leukemia cells.

Base Sequence↗
PubMed1989

Effects of protein intake on pulmonary gas exchange and ventilatory drive in postoperative patients.

The effects of different protein regimens on pulmonary gas exchange and ventilatory drive were examined in eight postoperative patients receiving inspiratory pressure support ventilation. They were studied during 60 consecutive hours, which included two 12-h periods of high protein intake (33%) of total caloric intake provided as protein), each of them being preceded and followed by a 12-h period of standard protein intake (14% of total caloric intake provided as protein). Throughout the study, total caloric intake was 1.5 times the predicted resting energy expenditure. Nitrogen was provided as a 24% branched chain amino acid (BCAA) solution during the period of standard protein intake. During the periods of high protein intake, it was provided as a 24% and a 41% BCAA solution. Pulmonary gas exchange was continuously measured during the second half of each period, with the use of a mass spectrometer system. Measurements of the ventilatory response to CO2 (FICO2 0, 1.5, and 3%) were achieved at the end of each dietary regimen. O2 consumption, CO2 production, respiratory quotient, minute ventilation, and PaCO2 were the same for the three protein regimens. Changing protein intake failed to affect the ventilatory response to CO2. The authors conclude that, in postoperative patients having inspiratory pressure support ventilation, the administration of a high protein intake does not affect the ventilatory drive and the pulmonary gas exchange.

Carbon Dioxide↗
PubMed1988

New strategies for the screening of a large number of immobilized dyes for the purification of enzymes. Application to the purification of enzymes from human haemolysate.

A method is presented for screening immobilized dyes applicable to the purification of enzymes from haemolysate (haemolysate can be considered as a nearly pure solution of haemoglobin containing only marginal amounts of enzymes). Haemolysate is loaded on immobilized dye mini-columns until haemoglobin and the studied enzymes are found in the column eluate at the same concentrations as those present in the haemolysate. Such a frontal mode of screening allows those dyes to be selected which, displaying a higher affinity for the enzyme of interest than for haemoglobin, can be used to displace the unwanted protein (haemoglobin) from the column by the enzyme of interest (present at a much lower concentration).

Coloring Agents↗
PubMed1988

Purification of human 6-phosphogluconate dehydrogenase from human haemolysate with chromatography on an immobilized dye as the essential step and use of automation. Simultaneous purification of lactate dehydrogenase.

The screening procedure described in the preceding paper allowed a practical purification procedure to be devised that was automated for human 6-phosphogluconate dehydrogenase. The purification needed only two chromatographic steps, first on immobilized Procion Blue HE-GN and then on Phenyl-Sepharose. This technique also gave purified lactate dehydrogenase. Both enzymes showed single bands in SDS polyacrylamide gel electrophoresis.

Buffers↗