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Biomedical subjects

H Wajcman

Publications and source records attributed to H Wajcman.

At least 199 records · Page 11Linked to original sources
PubMedDate not supplied

Electrophoretically silent hemoglobin mutants as revealed by isoelectric focusing in immobilized pH gradients.

The applications of isoelectric focusing in immobilized pH gradients to the analysis of (i) human hemoglobin mutants, (ii) animal hemoglobin mutants (from cattle, sheep, dog and mouse), and (iii) tryptic digests of alpha and beta chains, are discussed and evaluated. Immobilized pH gradients appear to be an excellent tool for screening of genetic polymorphism and for detecting "silent mutants", i.e. those substitutions involving amino acids with nonionizable side chains. At present, not even capillary zone electrophoresis, claimed to have a resolving power equivalent to 1 million theoretical plates, has shown a resolution capability comparable to that of immobilized pH gradients, at least in the field of protein separation.

Animals↗
PubMedDate not supplied

Short insertion in a hemoglobin chain: Hb Esch, an unstable alpha1 variant with duplication of the sequence Ala65-Leu-Thr-Asn68.

Hemoglobin (Hb) Esch, is an alpha1 variant, expressed at less than 5%, resulting from the duplication of the 12 nucleotides corresponding to CD65 through 68. The effect of this insertion is the repetition of the sequence Ala-Leu-Thr-Asn, which corresponds to the last turn of helix E. In this variant the presence of a one-turn elongated helix E causes instability and increased ligand affinity. Hb Esch was characterized by DNA sequencing and confirmed by electrospray mass spectrometry. Functional studies were performed by flash photolysis measurements on a fraction isolated by flatbed isoelectric focusing, which was enriched in the abnormal hemoglobin. Similar to other alpha chain variants due to short insertion (or deletion), Hb Esch probably results from a slipped mispairing mechanism. The stability of such modified proteins depends upon the region which is added or deleted and usually is more stable when involving a flexible loop or complete helix turn(s) near by.

Adult↗
PubMedDate not supplied

Glucose-6-phosphate dehydrogenase deficiency and homozygous sickle cell disease in Congo.

G6PD genotypes were determined in Brazzaville (Congo) on 188 HbSS patients (109 females, 79 males) and 210 controls (115 females and 95 males) with HbAA. DNA samples were analyzed by the polymerase chain reaction (PCR). The frequencies of G6PD B, A+ and A- alleles were 56.9, 20.8 and, 22.2% in the patients versus 56.3, 21.2 and, 22.5% in the controls, respectively. The prevalence of G6PD genotypes in HbSS did not differ (p > 0.05) from that found in the controls. Prevalence of G6PD deficiency did not change when patients were stratified by age, suggesting that there is no advantage of the association of G6PD deficiency with HbSS. Red blood cell count, mean corpuscular volume and mean corpuscular hemoglobin were not modified by the G6PD genotypes, while Hb level was lower in HbSS with G6PD A-. Our study suggests that in Congo, G6PD deficiency does not offer any biological advantage to sicklers.

Adolescent↗
PubMedDate not supplied

Two fetal hemoglobin variants affecting the same residue: Hb F-Emirates [G gamma 59(E3)Lys-->Glu] and Hb F-Sacromonte [G gamma 59(E3)Lys-->Gln].

Two fast-moving fetal hemoglobin variants were discovered in hematologically normal newborn babies; the first originated in the United Arab Emirates and the second in France. The structural study, carried out by miniaturized techniques of protein chemistry, showed that these two mutations affected the same residue of the G gamma chain, the lysine at position 59(E3) was replaced by glutamic acid in Hb F-Emirates, and by glutamine in Hb F-Sacromonte.

Amino Acid Sequence↗
PubMedDate not supplied

Gamma chain heterogeneity: determination of Hb F composition by perfusion chromatography.

The Ggamma:Agamma ratio is around 70:30 at the time of birth and usually 40:60 in the trace amounts of Hb F found in the adult. Changes in this ratio are observed in several hemoglobin disorders providing insights on the genetics and molecular pathophysiology of these diseases. Several techniques have been proposed to measure the Ggamma:Agamma ratio. We here describe perfusion chromatography which is now in routine use in one of our laboratories. The method involves a high velocity flow of the mobile phase through a porous reversed phase chromatographic stationary bed and allows us to determine this parameter one order of magnitude faster than with conventional high performance liquid chromatography.

Chromatography↗