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H Wajcman

Publications and source records attributed to H Wajcman.

At least 127 records · Page 7Linked to original sources
PubMed1986

Isolation of human haemoglobin variants with altered Bohr effect. Application to haemoglobin Rainier.

Isoelectric focusing on polyacrylamide gel in the absence of haem ligands represents a useful, convenient and rapid procedure to isolate silent Hb variants in their native forms, provided that they exhibit an abnormal Bohr effect. The amount of material which is eluted is sufficient for both a limited functional study and a structural determination using microscale high-performance liquid chromatography. This is exemplified by the isolation and the study of Hb Rainier.

Chromatography, High Pressure Liquid↗
PubMed1986

Human beta-melanocyte-stimulating hormone revisited.

It is generally accepted that human beta-melanocyte-stimulating hormone (h beta MSH) does not normally exist in humans but was merely an artifactually generated 22-amino acid peptide corresponding to a lipotropin (LPH) fragment (residues 35-56). We examined whether the shorter 18-amino acid peptide h beta MSH-(5-22) could be detected in some human tissues. Normal human pituitaries and hypothalami as well as corticotropin-secreting pituitary and nonpituitary tumors were extracted and chromatographed on Sephadex G-50, and the fractions were measured with two radioimmunoassays using either a COOH-terminal human gamma LPH (h gamma LPH) antiserum that recognized equally h gamma LPH, h beta MSH, and h beta MSH-(5-22) or a mid-portion h gamma LPH antiserum that recognized h gamma LPH and h beta MSH but not h beta MSH-(5-22). Normal pituitaries and pituitary tumors contained a single immunoreactive material coeluting with h gamma LPH. The hypothalami and the nonpituitary tumors all contained h gamma LPH and a smaller molecular weight material that was only detected in the COOH-terminal h gamma LPH radioimmunoassay; its elution volume (Ve/V, 0.75) was identical to that of h beta MSH-(5-22) but different from that of h beta MSH (Ve/V, 0.60); on reversed-phase HPLC, it coeluted with synthetic h beta MSH-(5-22) with a retention time different from that of h beta MSH. It is concluded that h beta MSH-(5-22) that corresponds to the 18-amino acid peptide h beta LPH-(39-56), flanked by two pairs of basic amino acids within the h beta LPH molecule, is a normal maturation product of proopiomelanocortin in human nonpituitary tissues.

Amino Acid Sequence↗
PubMed1986

Heterogeneity of sickle cell disease as shown by density profiles: effects of fetal hemoglobin and alpha thalassemia.

Factors that modify the intraerythrocytic concentration of hemoglobin S may influence the clinical expression of the disease. Using the phthalate ester method, the red blood cell density has been studied as a function of the mean corpuscular hemoglobin concentration. Four parameters have been used to compare the density distribution of the erythrocytes: D50 (median cell density), R60 (density range in which the middle 60% of the cells are found), F4 and F5 (proportion of cells with density greater than 1.110 and 1.120 g/ml). Compared to normal controls the density distribution of sickle red cells is heterogeneous, reproducible for the same patient (except in case of crisis), while different from one to another. The R60 is correlated with the percentage of dense cells, and the highest values for both R60 and dense cells are found when hemoglobin F is less than 10%. The highest values for the median cell density and dense red cells, but not for R60 which is normal, are observed in S/C patients. In sickle cell anemia patients, the median cell density values are not very different from the normal ones. The highest levels of hemoglobin F are found in this median subpopulation of red cells, while they are very low in the densest cells. R60 and the percentage of dense cells are not affected by the association of sickle cell disease with the deletion of one alpha gene. Their values are very near the normal ones in the case of an association with beta thalassemia or homozygous alpha thalassemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Anemia, Sickle Cell↗
PubMed1985

Electrophoretic and chromatographic techniques for the differential diagnosis of a haemoglobin abnormality: Hb E heterozygosity.

A method is described for separating haemoglobin (Hb) E (beta 26 Gly----Lys) from Hb A2 (a normal minor Hb component in adult blood). The technique allows the distinction between subjects carrying beta-thalassaemia trait and patients who are simultaneously alpha-thalassaemic and heterozygous for Hb E, the standard electrophoretic pattern often being similar in these two circumstances. Complete separation between Hb E and Hb A2 (2 mm empty space in between) is obtained by isoelectric focusing in immobilized pH gradients in an ultra-narrow pH 7.55-7.65 gradient. The apparent pI values of the two species (at 10 degrees C and at an average ionic strength of 5.6 mequiv. l-1) have been calculated to be 7.603 for Hb E and 7.607 for Hb A2. Thus, the system reported here affords a resolution of at least 0.004 pH unit.

Chromatography, High Pressure Liquid↗
PubMed1985

Hematologically and genetically distinct forms of sickle cell anemia in Africa. The Senegal type and the Benin type.

Patients with sickle cell anemia vary in the hematologic and clinical features of their disease, in part because of variability in the presence of linked and unlinked genes that modify the expression of the disease. The hemoglobin S gene is strongly linked to three different haplotypes of polymorphic endonuclease-restriction sites of the beta-like gene cluster (genes in the vicinity of the beta-globin gene)--one prevalent in Atlantic West Africa, another in central West Africa, and yet another in Bantu-speaking Africa (equatorial, East, and southern Africa). We have studied the differences in the hematologic characteristics of patients with sickle cell anemia from the first two geographical areas. We find that the Senegalese (Atlantic West Africa) patients have higher levels of hemoglobin F, a preponderance of G gamma chains in hemoglobin F, a lower proportion of very dense red cells, and a lower percentage of irreversibly sickled cells than those from Benin (central West Africa). We interpret these data to mean that the gamma-chain composition and the hemoglobin F level are haplotype linked and that the decrease in the percentage of dense cells and irreversibly sickled cells is secondary to the elevation in the hemoglobin F level. Patients with sickle cell anemia in the New World probably correspond to various combinations of these types, in addition to the still hematologically undefined haplotype associated with sickle cell anemia in the Bantu-speaking areas of Africa.

Adult↗
PubMed1985

Membrane expansion as a mechanism explaining the antisickling action of ticlopidine observed in vitro.

Ticlopidine, a platelet antiaggregant, has shown some efficacity in a clinical trial in patients with sickle cell disease. We have studied this agent in vitro to evaluate its effects on sickle erythrocyte. Ticlopidine effects sickling in vitro not by direct interaction with hemoglobin, but via strong binding to the red cell membrane. The density of the whole cell population is decreased when cells are treated with 0.1 mM ticlopidine, which is higher than the concentrations of 1 microM potentially achievable in vivo. Since hemoglobin concentration influences the delay time for gelling, its decrease in the red cell could have a beneficial effect. Such a partial inhibition of the polymerization is shown by oxygen equilibrium studies at various ionic strengths.

Anemia, Sickle Cell↗
PubMed1985

Common haplotype dependency of high G gamma-globin gene expression and high Hb F levels in beta-thalassemia and sickle cell anemia patients.

We have studied 42 homozygous beta-thalassemia patients from Algeria and 34 sickle cell anemia patients from Senegal and Benin, determining the relationship between haplotypes, Hb F, and G gamma-globin/A gamma-globin ratios. Populations selected have a high frequency of haplotype homozygotes because of consanguinity (Algeria) and geographic homogeneity (West Africa). We find in beta-thalassemia patients, that haplotype IX in haplotypic homozygotes and heterozygotes, haplotype III in heterozygotes, and the Senegal haplotype in sickle cell anemia patients are all linked to high G gamma-globin expression. In addition, haplotypes IX and Senegal, but not haplotype III, have high Hb F levels. All of these haplotype have a common subhaplotype (+- ) in the gamma-globin gene region. In addition, haplotypes IX, III, and Senegalese sickle cell anemia patients exhibit hematological amelioration of their disease. Conversely, haplotypes I, V, and A in thalassemia patients, which also have a common subhaplotype (-----), and the Benin subhaplotype (--++-) in sickle cell anemia patients are all associated with low G gamma-globin and low Hb F levels. Low G gamma-globin expression in the adult is associated with two haplotypes that are not common between thalassemia and sickle cell anemia patients. We conclude that the determinant for high G gamma-globin expression is haplotype-linked to common and genetically dominant subhaplotypes in the two diseases. The total Hb F level, unlike the high G gamma-globin expression, however, is linked to haplotypes but not to subhaplotypes, thus dissociating the two genetic effects.

Anemia, Sickle Cell↗
PubMed1985

[Genetic polymorphism of drepanocytosis].

The pathophysiological mechanism of sickle cell anemia has been thoroughly studied and is now well understood, in contrast to the extreme clinical heterogeneity of the disease. A possible genetic explanation for this diversity arose from the discovery of an HpaI restriction polymorphism 3' to the beta globin gene, in linkage disequilibrium with the Hb S mutation. This linkage is unequally distributed among ethnic groups in Africa and predominantly found in Central West Africa. A multipolymorphic analysis spanning 60 Kb of the beta globin gene cluster demonstrated that the sickle mutation arose at least 3 times in 3 different geographical areas (Atlantic West Africa, Central West Africa and Equatorial Central Africa) and expanded by malaria selection. Two genetic factors seem to have epistatic effects which differ when comparing the two first groups. The alpha thalassemia gene (-alpha) is distributed equally among African Black control populations (0.10). The frequency is significantly higher in the SS patients of the Benin area (Central West Africa), whereas it is unmodified in the patients of Senegal (Atlantic West Africa). Alpha thalassemia does not seem therefore to have exercised the same selective effect in this latter group. Secondly, fetal hemoglobin is quantitatively and qualitatively different in both groups. A high G gamma phenotype (greater than 60%) is found in Senegal, whereas a low G gamma phenotype is constant in Benin, without overlap between the two series. The total production of fetal hemoglobin is statistically higher, although only moderately, so in the first group.(ABSTRACT TRUNCATED AT 250 WORDS)

Africa, Central↗
PubMed1984

Structure and function of Hb Saint-Jacques (alpha 2 beta 2 140 (H18) Ala----Thr): a new high-oxygen-affinity variant with altered bisphosphoglycerate binding.

A low P50 value in a fresh red blood cell suspension was discovered in a polycythemic patient (Hb 19 g X dl-1). Routine acid and alkaline electrophoreses of the hemolysate were identical to normal hemolysate. Isoelectrofocusing (pH gradient 6-8) did not reveal any abnormal band whether performed with the fully liganded or deoxygenated samples. Precise analyses of the oxygen dissociation curves of the propositus' red cells demonstrated a biphasic Hill plot, a normal Bohr effect and low interaction with 2,3-bisphosphoglycerate (2,3-DPG). Studies on the unfractionated hemolysate confirmed these observations and the inhibition of the effect of organic phosphates. Structural studies were carried out on the mixture of beta A + beta X chains and revealed the presence of two beta Tp14 peptides. Sequencing the abnormal beta Tp14 peptide showed the substitution Ala----Thr of the beta 140 (H18) residue. This new variant was named Hb Saint-Jacques. Examination of the three dimensional model of HbAo indicates that the substitution beta 140 (H18) Ala----Thr induces van der Waals interactions with the nearby lysine-82 (EF6) and leucine-81 (EF5) and a displacement of the EF corner of the beta chains. This is likely to change the normal position of the lysine-82 (EF6), a major anionic binding site in the central cavity between the two beta chains. Functional studies confirm the interpretation of a steric hindrance inhibiting the binding of large organic phosphates to Hb Saint-Jacques.

2,3-Diphosphoglycerate↗
PubMed1984

Immobilized pH gradients and reversed-phase high-performance liquid chromatography: a strategy for characterization of haemoglobin variants with electrophoretic mobility identical to that of Hb A. The case of Hb San Diego.

The preparative aspects of immobilized pH gradients applied to abnormal haemoglobins (Hb) is described. As shown with the example of Hb San Diego, this method is successful even with as small a difference in pHi as 0.01 pH unit. For characterization of such neutral variants, reversed-phase high-performance liquid chromatography is demonstrated to be a very efficient tool.

Amino Acids↗
PubMed1984

A new hemoglobin variant altering the alpha 1 beta 2 contact: Hb Chemilly alpha 2 beta 2 99(G1)Asp leads to Val.

Hemoglobin Chemilly (alpha 2 beta 2 99(G1)Asp leads to Val), a high oxygen affinity variant, was uncovered in the red blood cells of a polycythemic patient who reported to the hospital concerning periodic headaches. We describe the molecular abnormality and functional studies of this new abnormal Hb. beta 99(G1)Asp, an invariant residue of hemoglobin, is considered a key amino acid for conformational changes between the R in equilibrium T quaternary structures responsible for the allosteric behavior of hemoglobin. Hb Chemilly exhibits a high O2 affinity, very low cooperativity and reduced Bohr effect. Its functional abnormalities are compared to the 5 other Hb variants at site beta 99(G1) described up to now of the 7 single base substitutions predictable from the genetic code.

Adult↗
PubMed1984

[Erythrocytosis due to a high-affinity hemoglobulin: mutant hemoglobin Saint-Jacques beta 140 (H18) Ala----Thr with a change in the 2,3-diphosphoglycerate binding site].

All the high oxygen affinity variants have substitutions in regions that are crucial to hemoglobin function: mainly the alpha 1 beta 2 interface, the C-terminal end of the beta chain and the aminoacid residues involved in the 2,3 disphophoglycerate (2,3 DPG) binding site. In this report we describe a new variant with familial erythrocytosis: hemoglobin Saint-Jacques beta 140 (H18) Ala----Thr, whose main abnormality is a defect in organic phosphate binding in the central cavity between to two beta chains. This variant could not be separated from hemoglobin A by standard electrophoretic methods or by isoelectric focusing. The abnormal peptide was isolated by reverse-phase high performance liquid chromatography and the structural modification determined by manual sequencing micro-method. Functional studies on red blood cells as well as on stripped lysate showed increased oxygen affinity, normal Bohr effect, decreased heme-heme interaction and loss of the 2,3 DPG regulatory effect.

2,3-Diphosphoglycerate↗