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Biomedical subjects

O Bertrand

Publications and source records attributed to O Bertrand.

At least 127 records · Page 7Linked to original sources
PubMed1985

Protein precipitation induced by a textile dye. Precipitation of human plasminogen in the presence of Procion Red HE3B.

It was demonstrated that human purified plasminogen was precipitated in the presence of the textile dye Procion Red HE3B. The amount of precipitated plasminogen was dependent upon the molar ratio between the dye and protein and seemed to be independent of the protein concentration. A certain amount of dye was coprecipitated with the protein; this was shown also to be related to the dye-to-protein molar ratio. The precipitation of plasminogen induced by the dye was shown to have a pH optimum and to involve ionic and hydrophobic interactions. Procedures were devised which enabled the recovery of precipitated plasminogen in a soluble and non-denatured form totally free from dye. However, the precipitation of plasminogen by Procion Red HE3B could not be used as a single-step purification procedure from a heterogeneous starting material like plasma because of coprecipitation of other proteins. Nevertheless it is suggested that frequently there is a chance that a given protein will be precipitated by a given dye and therefore that protein precipitation by dyes could be a useful complementary method for the purification of proteins.

Aminocaproic Acid↗
PubMed1985

Interactions of the human red cell membrane tyrosine kinase with heparin.

Heparin interacts with protein kinases in various ways; the different patterns of behavior of heparin towards protein kinases contributes to the characterization of these enzymes. We studied the interactions between heparin and a new type of tyrosine kinase extracted from the normal human red cell membrane. We found that heparin inhibited kinase activity by competition with ATP. Furthermore the interaction of heparin with the red cell membrane tyrosine kinase allowed us to use heparin-agarose chromatography as a step towards tyrosine kinase purification.

Adenosine Triphosphate↗
PubMed1985

Sequential colour mapping system of brain potentials.

We present a colour mapping system for the visualization of both the spatial scalp distribution and the temporal evolution of brain potentials. The system is applicable to recordings of auditory, visual and somatosensory potentials. It uses a Tektronix 4113 colour terminal connected to a Solar 16 (SEMS) mini-computer. The brain potentials are recorded on up to 16 scalp electrodes. The gain and the baseline are corrected separately on each channel. At each point of the scalp the potential is reconstructed by a linear interpolation of the measured potentials of the four nearest electrodes. Simultaneously n2 (1 less than n less than 8) colour maps can be presented on the screen. This allows the study of the temporal evolution of full scalp evoked potentials. The user chooses the two extreme latencies defining the time window to be explored and the latencies of the maps are regularly time-spaced within this window. In a typical case, in which four maps are desired, the latencies of the maps can be chosen independently. The 16-colour palette is predetermined but the user has three possibilities to establish the correspondence between the electrical potential and the colours. Examples are shown in the visual and somatosensory stimulation modalities. The advantages and limitations of such a representation are discussed.

Brain↗
PubMed1985

Bicarbonate-stimulated ATPase activity of bovine liver alkaline phosphatase.

A commercial preparation of bovine hepatic alkaline phosphatase was found to have a Mg2+-stimulated ATPase activity. The pH optimum was 8.5, the Km for ATP was 4.2 X 10(-5) M and the Vmax was 88.3 mumol Pi . h-1 . mg-1. HCO3- had a stimulatory effect on Mg2+ -ATPase activity. Other anions had no effect or an inhibitory effect while Na+, K+ and ouabain had no effect. Purification of the commercial preparation by gel filtration and affinity chromatography yielded a fraction with alkaline phosphatase and (Mg2+ + HCO3-)ATPase activities that had been enriched respectively 27-fold and 23-fold; both activities were inhibited by levamisole (93.1% and 93.8%, respectively) and the purified fraction was found to be a single protein on sodium dodecyl sulfate polyacrylamide gel electrophoresis. These results suggest that alkaline phosphatase and (Mg2+ + HCO3-)ATPase may be properties of the same liver protein that might be involved in biliary HCO3- transport and bile secretion.

Alkaline Phosphatase↗
PubMed1984

The temporal component of the auditory evoked potential: a reinterpretation.

The auditory evoked potentials in man cannot be explained by a single source even though a strong influence of the primary areas in the supra-temporal plane has been pointed out in different works. In 26 normal adults we mathematically extracted the greater part of the experimental AEPs explicable by such an origin. The residual part obtained by subtracting this first component from the experimental data is in agreement with an origin in the precentral motor cortex.

Brain Mapping↗
PubMed1984

A variant of erythrocyte membrane skeletal protein band 4.1 associated with hereditary elliptocytosis.

A family comprising three patients (a mother and two children) with mild hereditary elliptocytosis was studied. Each patient had prominent elliptocytosis, reduced red cell deformability, and normal erythrocyte thermal sensitivity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the erythrocyte membranes in each patient showed decreased levels of band 4.1 (approximately half of the normal value) and the presence of an additional band migrating below protein band 4.2. This additional band was shown to derive from protein 4.1. Comparative partial proteolytic mapping of protein 4.1 and the additional band revealed a number of common peptides. Enzyme-linked immunoelectrotransfer blots of the patients' erythrocyte membranes using a monoclonal antibody to protein 4.1 revealed that, in addition to protein 4.1, two other bands below protein 4.2 were stained; one of these bands migrated in the same position as the additional band detected in the Coomassie Blue-stained gels. Immunoblotting of the patients' whole cells using the antibody to protein 4.1 revealed that this altered band 4.1 occurred as such in the intact red cell. SDS-PAGE of protein 4.1 purified from one patient showed the presence of two lower molecular weight bands below protein 4.1; the lower band migrated in the same position as the additional band found on SDS-PAGE of the patients' erythrocyte membranes. The patient's purified protein 4.1 displayed a decrease of about 40% in the binding activity with crude spectrin extracted from normal controls. Spectrin-spectrin interactions were normal in the three patients. The additional band present in the patients' red cell membranes probably represents a proteolytic degradation product. This alteration, present both in whole cells and isolated membranes, might affect the intact cells in vivo. We suggest that the patients' erythrocyte membrane instability may be related to the presence of an abnormal protein 4.1 whose modulatory influence on the spectrin-actin interaction in the skeleton is defective.

Adult↗
PubMed1983

Plasminogen Paris I: congenital abnormal plasminogen and its incidence in thrombosis.

An abnormal plasminogen was discovered because of a decreased level of plasminogen activity in plasma contrasting with a normal level of plasminogen antigen concentration. The same discrepancy was found in the purified plasminogen. The molecular abnormality seems to be inherited. The patient is a heterozygote. The experimental findings can be explained by assuming that half of the plasminogen is normal, while the other half is an inactive mutant protein, without catalytic activity after SK or UK addition. There was no binding of labeled DFP and a decreased binding of TLCK to the abnormal plasminogen. The role of the abnormal plasminogen in thrombotic tendency is uncertain since the patient is the only one who has suffered a thrombotic accident, while her relatives who present the same defective plasminogen have not had thrombotic problems.

Blood Coagulation↗
PubMed1982

Molecular organization of human L' and L pyruvate kinases.

Extremities, peptide maps and phosphorylatable site localization of human erythrocyte L' and liver L pyruvate kinases (EC 2.7.1.40) were investigated. L' and L subunits seemed to have similar, blocked NH2 termini and differ in their sensitivity to carboxypeptidase A, that is to say in their C-terminal ends. After digestion by Staphylococcus aureus V8 protease, the phosphorylated sites of both L' and L subunits were located on those peptides which were different in L' and L, that is to say on the C-terminal sides. A mild proteolytic attack of the native tetrameric enzymes by trypsin partially degraded the phosphorylatable peptides without removing the phosphoserine residue; in the same conditions, chymotrypsin split off this phosphorylated residue and subtilisin totally degraded the phosphorylated peptides. From these results it appears, therefore, that age-dependent proteolytic degradation of L' subunits in old red cells involves the C-terminal side of the molecules, ultimately resulting in cleavage of the phosphorylated site. Since erythrocyte L' and liver L subunits are encoded by different species of messenger RNAs, our results indicate, in addition, that these messenger RNA species should differ by their 3' coding sequences.

Carboxypeptidases↗
PubMed1982

Automated purification of human erythrocytic 6-phosphogluconate dehydrogenase.

Human 6-phosphogluconate dehydrogenase (6PGD) was purified from hemolyzate by group affinity chromatography on 2',5'-ADP-Sepharose, followed by buffer exchange chromatography on Sephadex G-25 and finally salting-out chromatography on Sepharose 6B. An apparatus was assembled from commercially available elements, in which the purification procedure can proceed and be completed unattended and under fully automatic control. The weekly production of the set-up is at present 10 mg of pure 6PGD. The choice of the purification of procedure and the advantages of automation are discussed.

Chromatography↗
PubMed1982

The amidolytic activity of the SK-plasminogen complex is enhanced by a potentiator which is generated in the presence of vascular plasminogen activator--role of fibrin degradation products.

In the presence of an excess of streptokinase (SK) the amidolytic activity of the plasminogen-SK complex on chromogenic substrates is 12% lower in serum than in the corresponding plasma. However, in subjects in whom venous stasis lead to a shortening of the euglobulin lysis time to less than 60 min (high responders), the amidolytic activity of the plasminogen-SK complex in serum was 60% higher than in the corresponding plasma. Attempts to find alterations of the plasminogen molecule itself which would account for the enhanced activity in high responder serum were negative. No free plasmin was present and the plasminogens isolated from plasma and serum before and after venous stasis had the same amidolytic activity as gluplasminogen in the presence of an excess of SK. N-terminal analysis of these four plasminogens revealed in each instance glutamic acid. The enhancement of the amidolytic activity of the SK-plasminogen complex in serum of high responders (potentiator activity) could be reproduced by adding purified tissue plasminogen activator (TA) to native blood before clotting, but not if TA was added to plasma or to prestasis serum. Removal of fibrin degradation products from poststasis serum resulted in the disappearance of potentiator activity. These experiments suggest that fibrin degradation products, generated during clotting in the presence of vascular or tissular plasminogen activator act as a potentiator of the amidolytic activity of the plasminogen SK-complex.

Amides↗
PubMed1981

Mechanism of allosteric activation of glycogen phosphorylase probed by the reactivity of essential arginine residues. Identification of an arginine residue involved in the binding of glucose 1-phosphate.

We have previously reported the physicochemical and kinetic properties of glycogen phosphorylase modified by arginine-specific reagent under different conditions [Dreyfus, M., Vandenbunder, B., & Buc, H. (1980) Biochemistry 19, 3634-3642]. The properties of the modified enzyme depend upon the conformation adopted by the enzyme during the modification reaction. In this paper, we report the localization of the crucial modified arginine residues on the primary structure. The chymotryptic peptide extending from residue Asp-563 to residue Tyr-572 was shown to contain one arginine residue (Arg-568) which is chemically modified by phenylglyoxal in phosphorylase a and in activated phosphorlase b. Inclusion of glucose 1-phosphate in the modification medium protects this residue from modification, with a concomitant protection of the enzyme activity. Furthermore, this residue is not reactive toward phenylglyoxal in phosphorylase b in the absence of any effector. Addition of the AMP analogue 2'dAMP, which is not an activator of the enzyme, does not increase Arg-568 reactivity but protects from modification several arginine residues located between Arg-242 and Leu-348. The location and the role of Arg-568 in phosphorylase are discussed with reference to recent data from X-ray crystallography.

Allosteric Regulation↗