Biomedical subjects
Publications and source records attributed to M C Garel.
The amino acid residues involved in the areas of contact that stabilise the haemoglobin S polymer fibre seem to be the same ones that stabilise the basic unit of the deoxyhaemoglobin S crystal: the Wishner-Love double strand. The haemoglobin S fibre is probably formed by a unique packing of these double strands.
It has been demonstrated by numerous workers that variations in levels of glycolysed hemoglobins Hb Al (Alb, Alb, Alc) are an excellent means of control of the quality of diabetes control. The estimation of the main glycolysed hemoglobin (Hb Alc) is very difficult, and various chromatographic methods have been developed to permit rapid estimation of all these glycolysed hemoglobins. Our work consisted of testing the three microcolumn kits on the french market: Isolab, Helena and Biorad. The great thermo-dependency of the first two kits did not permit us to obtain results in correlation with those of our reference technic derived from Trivelli's method. On the other hand, the levels of Hb Al obtained with the Biorad kit were perfectly correlated with the levels of Hb Alc. The average normal of Hb Al was 6,45 +/- 0,66 p. cent, CV 10,2 p. cent; the average value of Hblc was 5,4 +/- 0,4 p. cent. CV 7,4 p. cent. The average levels of Hb A obtained in diabetic subjects was 12 p. cent, the levels of Hblc being 10 p. cent. Certain restrictions in the use of these microcolumns were demonstrated: presence of Hb F or abnormal Hb, hyperlipemia and presence of chylomicrons.
Normal red blood cells contain, in addition to the major hemoglobin (Hb A) some minor fractions as Hb A2 and glycosylated hemoglobins: Hb A1a, Hb A1b, Hb A1c. The study of the glycosylated hemoglobins has been greatly stimulated by the observation that their proportion was increased in diabetes mellitus. This paper sums up the more recent knowledge on the structure of the minor fractions, and mainly on Hb A1c. Biosynthesis of these hemoglobins is also considered. Since the glycosylated hemoglobins has raised a great interest, different techniques were designed for its assay: chemical, chromatographic and immunological techniques and isoelectric focusing. In this paper, these different methods are reviewed and compared.
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Isoelectric focusing on slabs of acrylamide gel was adapted for the screening of abnormal hemoglobins, the characterization of 70 human variants, and the study of minor fractions of normal hemoglobin. The screening method was as fast and inexpensive as conventional techniques, allowed the simultaneous analysis of some 50 samples of whole blood, and yielded resolution superior to that obtained by other methods with hemolysates. Among the 70 variants, 31 mutants could not be separated from HbS by cellulose acetate electrophoresis. The characterization technique of electrofocusing allowed us to distinguish between most variants. Only one mutant, Hb Galveston, could be confused with HbS. Hb Köln, the most frequent unstable mutant, exhibited a special pattern. HbA1C was separated from HbA. Preliminary results indicate that quantitation of HbA1C by gel scanning is feasible.
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Preliminary studies have suggested that in Hb Dakar, histidine alpha112 was substituted by a glutamine. A re-investigation on this hemoglobin is presented in this report. A structural study has been performed using a new approach to analyse the tryptic core region of the human hemoglobin alpha chain. After tryptic digestion of the aminoethylated alpha chain, a secondary digestion of the tryptic core was carried out with chymotrypsin and with another protease, thermolysin. Analyses of the chymotryptic and thermolytic peptides indicated that the structure of Hb Dakar was identical to that of Hb Grady previously described by Huisman et al. who showed the insertion of three amino acid residues in position alpha115 or alpha118. The insertion, which was localized near two residues involved in the alpha1beta1 contact, did not produce a dissociation into dimers. Functional studies demonstrated a a slightly increased oxygen affinity, a lowered cooperativity and a normal Bohr effect. The low amount of the abnormal hemoglobin (8%) may in part be explained by a slight instability of the molecule.
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The present report describes clinical, hematological and biochemical studies of a 27-year old Egyptian woman in whom a fast moving Hb variant was found. The abnormal Hb constituted 48% of the total erythrocyte Hb of the propositus and her father. Structural studies demonstrated that in the abnormal Hb lysine beta 65 is replaced by glutamine. The new Hb mutant is designated hemoglobin J Cairo beta 65 (E9) Lys leads to Gln. This substitution results in only a moderate decrease in cooperativity. No evidence of Hb instability was found. A slight anemic state has been observed in the propositus since she reached adolescence.
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