Biomedical subjects

C Prehu

Publications and source records attributed to C Prehu.

11 recordsLinked to original sources

PubMed2000

Two new variants with the same substitution at position beta122: Hb Bushey [beta122(GH5)Phe-->Leu] and Hb Casablanca [beta65(E9)lys-->Met; beta122(GH5)Phe-->Leu].

Hb Bushey, found in a Chinese baby and his father, is a new variant with a point mutation leading to the substitution Phe-->Leu at position beta122. Hb Casablanca, found in a family from Morocco, is a further example of a hemoglobin variant that carries two abnormalities in the same chain; the first is identical to that of Hb Bushey and the second to that of Hb J-Antakya [beta65 (E9)Lys-->Met]. Structural abnormalities of both Hbs were determined by protein chemistry methods including electrospray and tandem mass spectrometry. Their stability and oxygen binding properties were found to be identical to those of Hb A. Various mechanisms that may lead to two point mutations in the same chain are reviewed briefly.

2,3-Diphosphoglycerate↗

PubMed1998

Hemoglobins in Togolese newborns: Hb S, Hb C, Hb Bart's, and alpha-globin gene status.

The gene frequency of the most important hemoglobin (Hb) abnormalities is reported in a population of 171 Togolese newborns. Hb phenotypes, hematological parameters, and the more frequently described alpha-gene deletions were analyzed. Structural abnormalities of beta-globin were observed in 35.7% of the children with a gene frequency of 0.105 for beta(S) and 0.091 for beta(C). The frequency of the different alpha-globin genotypes was alpha alpha/ = 0.71, -alpha/ = 0.28, and alpha alpha alpha/ = 0.01. All of the individuals homozygous for the -alpha genotypes, and most of the heterozygous individuals, carried Hb Bart's. Within the alpha alpha/alpha alpha and the -alpha/alpha alpha groups, several individuals with or without Hb Bart's were found; they did not differ from the others by their red blood cell (RBC) parameters but by their levels of fetal hemoglobin (Hb F). The African alpha2 polymorphism marker, characterized by the replacement of G by TCGGCCC at position 7238 (EMBL HSHBA4, 1993) and of T 7174 by G, was found in 21 newborns. The mean value of Hb F was calculated for each genotype, the mean (G)gamma percentage was 69.4 +/- 4.0%, and the gene frequency of the AgammaT marker was 0.10; this marker was linked to the normal beta-globin cluster.

Blood Cell Count↗

PubMed1996

Perfusion chromatography on reversed-phase column allows fast analysis of human globin chains.

Human globin chain analysis provides important information on the genetics and molecular pathophysiology of hemoglobinopathies. We propose using perfusion chromatography on the reversed-phase stationary phase to perform these studies. The technique, herein described, involves a high-velocity flow of the mobile phase through a porous chromatographic stationary phase made of microspheres of poly(styrene-divinylbenzene) having throughpores of 6000-8000 A diameter with short diffusive pores of 500-1000 A diameter connected to them. The composition of fetal hemoglobin (Ggamma:Agamma ratio) is determined, using this method, as an order of magnitude faster than with conventional HPLC. Elution is performed by developing a linear gradient of acetonitrile at a flow rate of 3 ml/min (or more), easily obtained on any HPLC machine. Analyses may be done on samples containing as low as 3.0% Hb F. Results are similar to those obtained with the reference HPLC technique, which uses a C4 column. In addition, reversed-phase perfusion chromatography, using a shallow curvilinear gradient, may help in the characterization of Hb variants. This technique allowed us to discriminate several alpha and beta chain mutants from variants that have closely similar patterns of electrophoretic mobilities.

Chromatography↗

PubMed1988

[Home thrombolysis for myocardial infarction. A multicenter study of the feasibility and evaluation of short-term prognosis].

It has been proven since 1986 that in myocardial infarction the sooner thrombolysis is performed the better. Forty-four patients were selected to enter a double-blind randomized trial in which they received either an acylated plasminogen streptokinase activator complex or a placebo. The injections were given intravenously at home within the first 3 hours (within the first 2 hours in 26 of them), by doctors from Mobile care units. This home treatment in the acute phase made it possible to gain 75 minutes on average, and up to 90 minutes when it was performed by an anaesthetist trained in emergency management. No serious complication, such as haemorrhagic or allergic reaction, occurred, and arrhythmia was no more frequent in the treated group than in the placebo group. Home thrombolysis did not delay admission to a cardiology Intensive Care unit (66 min. versus 64 min). Mean coronary patency was 75 per cent, and up to 82 per cent, in patients treated within 2 hours of the first symptoms. There was no significant difference between areas of reperfused or not reperfused patients in relation to time (P less than 0.08). Diagnosis sensitivity was 100 per cent. Thus, home thrombolysis is feasible and safe when performed by trained emergency medical teams and when criteria for inclusion and exclusion are fulfilled.

Double-Blind Method↗

PubMed1988

Rabbit M type phosphoglyceromutase: comparative effects of two thiol reagents antibody reaction and hybridization studies.

1. Treatment of purified rabbit phosphoglyceromutase (M type) with N-ethylmaleimide or with iodoacetamide produces the concurrent loss of phosphoglyceromutase activity with its collateral glycerate-2,3-P2 phosphatase activity. 2. Differences are observed in the protective effect of glycerate-2,3-P2 and of glycolate-2-P against N-ethylmaleimide and iodoacetamide treatments. 3. Specific chicken antibodies obtained by injection of the purified rabbit M type phosphoglyceromutase do not cross-react with the B type but neutralize both rabbit and human M type phosphoglyceromutase. 4. Purified rabbit M type phosphoglyceromutase can hybridize in vitro with the purified human B type or with purified human glycerate-2,3-P2 synthase. 5. Its ability to hybridize with glycerate-2,3-P2 synthase is unchanged after iodoacetamide treatment.

Animals↗

PubMed1986

Contact inhibition within hemoglobin S polymer by thiol reagents.

N-Ethylmaleimide, a thiol reagent, increases the solubility of deoxyhemoglobin S. We investigated which of the two reacted beta 93 cysteine residues of the Hb tetramer was responsible for the inhibition of Hb S polymerization. Accordingly we compared the solubility of equal mixtures of HbA + HbS, HbA NEM + HbS and HbA + HbS NEM. Upon deoxygenation these mixtures contain about 50% a stable and asymmetrical hybrid alpha 2A beta A beta S, alpha 2A beta A,NEM beta S or alpha 2A beta A beta S,NEM respectively and 25% parental molecules as confirmed by ion-exchange HPLC performed in anaerobic conditions. Within the hybrid molecule, beta A or beta A,NEM chain has to be present in the alpha beta dimer located in trans to the dimer which contains the only beta 6 valine residue participating in intermolecular contacts (dimer in cis), while beta S or beta S,NEM must be in cis position in the hybrid molecule. The solubility of mixtures increases 4% for HbA NEM + HbS and 20% for HbA + HbS NEM mixtures compared to HbA + HbS mixture, indicating that the inhibitory effect of N-ethylmaleimide is more effective in cis than in trans position. The absence of a major role played by N-ethylmaleimide located in trans was supported by the solubility study of a mixture of HbS + Hb Créteil beta 89 Ser----Asn. The beta 89 residue in trans next to the cysteine beta 93 modified the T structure similarly to N-ethylmaleimide, and did not affect intermolecular contacts. Crystallographic studies of molecular contacts within deoxyHbS crystals suggest that the cis inhibitory effect of N-ethylmaleimide can be explained by direct inhibition of 'external' contacts between double strands involving the CD corner of the alpha chains.

Centrifugation↗

PubMed1986

Covalent binding of glutathione to hemoglobin. I. Inhibition of hemoglobin S polymerization.

Thiol reagents react with cysteine beta 93 of hemoglobin and as a result increase the oxygen affinity of hemoglobin. In the present studies we have used a thiol-disulfide exchange between mixed disulfides of hemoglobin and reduced glutathione to attach intracellular glutathione to hemoglobin and to study its antisickling properties. The rates of production of glutathionyl hemoglobin (G-Hb) depend on the structure of the thiol reagent linked to cysteine beta 93. Up to 25% G-Hb can be produced in normal and sickle red cells because of the high intracellular concentration of reduced glutathione. This high level of G-Hb in normal cells increases the oxygen affinity by about 35% and reduces heme-heme interactions. In sickle cells the increased oxygen affinity is associated with an inhibition of sickling of about 70% at 21 mm Hg. Inhibition of polymerization of deoxy HbS is also due to a direct inhibition of intermolecular contacts in the fibers as demonstrated by the increased solubility and the increased delay time of G-HbS compared to deoxy HbS.

Binding Sites↗

PubMed1986

Purification of the M-type phosphoglyceromutase from rabbit muscle.

A new method for the purification of M-type phosphoglyceromutase from rabbit muscle involving affinity chromatography on dye ligand media in the presence of 2,3-diphosphoglycerate is described. The method is rapid and technically simple. The purity of the enzyme was verified by electrophoresis in polyacrylamide gel in the presence of sodium dodecyl sulphate and by Cellogel electrophoresis. Immunological techniques showed that the anti-M antibodies are specific and do not cross-react with the B isozyme.

Animals↗

PubMed1985

Kinetics of water transport in sickle cells.

This paper reports the results of stopped-flow studies on differences in the kinetics of osmotic water transport of sickle and normal erythrocytes. The kinetics of inward osmotic water permeability are similar in sickle and normal red blood cells. In contrast, the kinetics of outward water flux are significantly (approx. 38%) decreased in sickle cells. Deoxygenation does not modify the water influx kinetics in either type of cells, but accelerates considerably the rate of water efflux in sickle cells. No significant variation of water transport kinetics was observed in density-separated cell fractions of either type. The results suggest that membrane-associated hemoglobin may decrease the outward water permeability and that in deoxygenated sickle cells the fraction of hemoglobin S near the lipid bilayer is lower than in oxygenated conditions.

Anemia, Sickle Cell↗

PubMed1984

Decrease of transport of some polyols in sickle cells.

This paper reports the results of kinetic studies on the inward net-flux of small non-electrolytes (ethylene glycol, glycerol and erythritol) in sickle cells as compared to normal erythrocytes. Net transport rates were evaluated by turbidimetric measurements for ethylene glycol and glycerol and by hematocrit monitoring for erythritol. A 2-fold and 4-fold reduction in the permeability coefficient for ethylene glycol and glycerol, respectively, were found in sickle cells as compared to normal erythrocytes. In contrast, no significant changes in erythritol transport kinetics were observed. The dependence of glycerol permeability on temperature, pH and oxygenation is the same in both types of cells. A significant correlation was observed between glycerol permeability and cell density only for sickle cells. The results indicate that irreversible modifications of membrane proteins, responsible for the glycerol and ethylene glycol transport, do occur in sickle cells.

Anemia, Sickle Cell↗

PubMed1984

Biochemical and immunological arguments for homology between red cell and liver phosphoglyceromutase isozymes.

Phosphoglyceromutase (2,3-bisphospho-D-glycerate:2- phospho-D-glycerate phosphotransferase, EC 2.7.5.3) from the red cell is compared with the muscle and the liver forms of the enzyme obtained from rabbits. Partially purified samples were used for this study. The electrophoretic mobility of red cell phosphoglyceromutase is completely different from that of muscle and similar to that of liver. The muscle isozyme can hybridize with liver or red blood cell phosphoglyceromutase. N-Ethylmaleimide, an SH group reagent, completely inhibits muscle phosphoglyceromutase activity and slightly inhibits the activity of the enzyme from liver and from red cells. Both liver and red cell isozymes are completely inactivated by heating at 60 degrees C for 15 min, whereas a 25% decrease in inactivity is noted for the muscle enzyme. Finally, chicken antibody directed against human red cell phosphoglyceromutase reacts with the enzyme isolated from rabbit red cells and liver, but not with that obtained from muscle.

Animals↗