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E C Abraham

Publications and source records attributed to E C Abraham.

At least 55 records · Page 3Linked to original sources
PubMed1987

Influence of gamma-chain amino-terminal acetylation on subunit assembly of human fetal hemoglobin.

A human hemoglobin F subunit recombination study was performed to determine the relative efficiency of recombination of amino-terminally acetylated gamma-chains and non-acetylated chains with alpha-chains. The results of this work suggested that the acetylated gamma Ic-chains combined more readily with the alpha-chains than the non-acetylated gamma o-chains. An important factor in the function and assembly of multi-subunit macromolecules is the interaction of the unlike subunits. A model system for the study of such interactions has been the protein hemoglobin. With respect to the hemoglobin molecule, it has been noted that relative affinities of normal and mutant subunits for the unlike subunits can have a significant influence on hemoglobin synthesis at the post-translation level, i.e., subunit assembly [1,2]. A similar mechanism may control the formation of human Hb FIc, a hemoglobin with NH2-terminally acetylated gamma- (gamma Ic)-chains. In this instance acetylation may occur on the ribosomes before subunit assembly. A previous report from our laboratory showed a slight increase in the relative proportion of Hb FIc in cord blood samples with over 5% Hb Bart's [3]. The data were interpreted to be due to an influence of alpha-chain deficiency (alpha-thalassemia) on the formation of Hb FIc and Hb Fo tetramers by a preference of alpha-chains for gamma Ic-chains over gamma o- (non-acetylated gamma)-chains. The present study involves an examination of the relative affinity of the gamma Ic- and gamma o-chains for the normal alpha-chains in an in vitro recombination system.

Acetylation↗
PubMed1987

A controlled investigation of propofol, thiopentone and methohexitone.

This was a randomized study of 180 ASA physical status I and II patients, 60 in each group who received propofol (PROP), 2.5 mg . kg-1, thiopentone (THIO), 4 mg . kg-1, or methohexitone (METH), 1.5 mg . kg-1. Control values, followed by changes after induction and during a 3-min delay before intubation were recorded for the following parameters: heart rate (HR), systolic and diastolic blood pressures (SBP, DBP), respiratory rate (RR), end-tidal CO2 (PETCO2), and induction time (IT). In addition, the incidence of adverse reactions and time for recovery from anaesthesia were noted. The IT (mean +/- SE) was 35 +/- 1 sec for propofol, 35 +/- 1.2 sec for thiopentone and 34 +/- 1.4 sec for methohexitone. Ninety-three per cent of the PROP group fell asleep with one dose and required no additional doses. Fifty per cent of each of the THIO and METH groups required additional agents (p less than 0.05). METH was associated with the highest elevation in HR, PROP the least (p less than 0.05). PROP was associated with the most decrease in SBP and DBP and in addition respiratory depression (p less than 0.05). The incidence of injection pain or excitatory activity was equal in the three groups with the exception that 14 patients who received METH developed hiccoughs while none did in the other groups. PROP was associated with the most rapid recovery, particularly with respect to the orientation time. We conclude that PROP is an effective alternative to barbiturate induction and that the published recommended doses of THIO and METH are often ineffective.

Adult↗
PubMed1987

Progressive changes in lens crystallin glycation and high-molecular-weight aggregate formation leading to cataract development in streptozotocin-diabetic rats.

Because of their remarkable longevity, lens crystallins undergo a substantial amount of glycation (non-enzymatic glycosylation) during diabetic hyperglycemia. These post-translational modifications have the potential to disrupt the structural and functional properties of the lens crystallins and contribute to the formation of cataracts. Streptozotocin-induced diabetic rats were used to study the relationship between glycation of lens proteins and the formation of insoluble high-molecular-weight (HMW) aggregates believed to be responsible for cataract formation. After the onset of diabetes, cataracts developed in about 12- to 13 weeks. The animals were followed in this manner until cataracts developed and for an additional 63 days. Five control and five diabetic rats were killed every 3 weeks and lenses removed. Levels of glycated protein and glycated amino acids in lenses from each animal were examined by affinity chromatography. In addition, the changes in crystallin composition and development of HMW aggregates were monitored by molecular-sieve HPLC techniques. As diabetic hyperglycemia continued there was a linear increase in glycated protein in both the soluble and insoluble fractions. This increase was paralleled by an increase in the soluble HMW and insoluble HMW aggregates. Other changes included a decrease in reactive sulfhydryls which indicates an increase in disulfide bond formation. The gamma-crystallin levels also decreased in a linear fashion during the hyperglycemic pre-cataract and cataract stages. It appears that the glycation of lens crystallin, the disappearance of reactive sulfhydryls and the formation of HMW aggregates are interrelated.

Amino Acids↗
PubMed1987

Minor components of Hb Bart's.

The minor components of Hb Bart's were separated by CM-cellulose chromatography, reverse-phase HPLC, and DEAE-cellulose chromatography. These were characterized by amino acid analysis, tryptic peptide analysis by HPLC, electrophoresis, and carbohydrate and phosphate analysis. Acetylated and glycated components of Hb Bart's were present in cord blood red cells. The ratio of gamma Ic/total gamma in Hb Bart's was nearly the same as that of Hb FIc/Hb F which may indicate that the gamma chain after its release from the ribosome is not a better acetylation substrate than Hb Fo. Glycation of the free gamma-chains seems to take place in vivo as readily as the major Hb components.

Carboxymethylcellulose Sodium↗
PubMed1987

Glycosylated hemoglobins in a diabetic patient with sickle cell anemia.

Results of analysis of blood samples from a diabetic sickle cell anemia (SS) patient and 4 nondiabetic SS patients for glycosylated hemoglobins by Bio-Rex 70 chromatography, high-pressure liquid chromatography, and affinity chromatography are presented. Glycosylated components of Hb S and Hb A2 and total glycosylated hemoglobins were quantitated in this manner. The levels of the various glycosylated hemoglobins were increased twofold in the diabetic patient compared to nondiabetic SS patients. The glycosylated hemoglobin levels in the diabetic SS patient and in the nondiabetic SS patients, however, were significantly lower than the levels normally seen in nonsickle diabetics and normal adults, respectively. In contrast to a previously reported diabetic SS patient, the present case appears to be not severely affected by sickle cell disease.

Adult↗
PubMed1987

Lens protein composition, glycation and high molecular weight aggregation in aging rats.

Because of minimal or no turnover, lens proteins are subjected to substantial post-translational modifications which in turn disrupt lens architecture and change the optical properties leading to senile cataract formation. Progressive glycation is believed to have the potential to initiate the changes that are conducive to lens opacification. Fisher 344 rats were systematically followed from juvenile to older and aged phases of their life to study the relationship between lens glycation and high molecular weight (HMW) aggregate formation as well as quantitative and qualitative changes in lens crystallins. Levels of glycated proteins were quantified by affinity chromatography. Changes in lens crystallin composition and HMW aggregate formation were monitored by molecular sieve HPLC, further confirmed by SDS-PAGE and IEF techniques. As the age advances HMW and insoluble proteins increase with a concomitant disappearance of gamma-crystallins from soluble fraction. This disappearance of gamma-crystallins coincided with increased glycation (approximately 2-fold higher in insoluble fraction) and decreased sulfhydryl groups from soluble fraction. It appears that lens protein glycation, disappearance of gamma-crystallins and sulfhydryls from soluble fraction and increase of insoluble fraction and HMW aggregate are interrelated.

Aging↗
PubMed1986

Human fetal hemoglobin synthesis and its NH2-terminal acetylation in a rabbit reticulocyte lysate translational system.

The biosynthesis of the acetylated (Hb FIc) and the non-acetylated (Hb F0) human fetal hemoglobin components has been examined in a cell-free translational system. The poly(A)-RNA was isolated from umbilical cord blood samples and translated in the heterologous translational system derived from rabbit reticulocyte lysates in the presence of labeled amino acid(s) or acetyl-CoA. The amount of each hemoglobin or globin chain made in the system was determined by separating the synthesis products by cation-exchange chromatographic methods. The in vitro synthesis ratios were close to the FIc/Ftotal values of the respective hemolysates. The same conclusion could be reached by determining the specific activity ratios of Hb FIc/Hb F0. Co-migration of radioactivity peaks with absorbance peaks indicated the synthesis of that hemoglobin or globin chain. Confirmation of the synthesis of true gamma 0 and gamma Ic was accomplished by high-pressure liquid chromatographic separation of 3H-labeled tryptic peptides. Each peptide corresponded well with the radioactivity peak. Labeled acetyl-group incorporation into Hb FIc and gamma IcT-1 provided direct evidence for acetylation of gamma chains in Hb FIc. The data indicate that the mRNA itself dictates whether a protein is acetylated and, if so, to what extent. The control appears to be not unique to the human red cell system.

Acetylation↗
PubMed1986

High-performance liquid chromatographic separation and quantitation of glycosylated hemoglobin A2 as an alternate index of glycemic control.

By a combination of DEAE-cellulose chromatography and cation-exchange high-performance liquid chromatography glycosylated components of hemoglobin (Hb) A2 were separated and quantitated from persons with diabetes and some common hemoglobinopathies. Hb A2Ic values correlated well with total glycosylated Hb levels assayed by affinity chromatography, and Hb AIc, Hb SIc and Hb CIc levels, determined by high-performance liquid chromatography. The results indicate that Hb A2Ic may serve as an alternate index of glycemic control.

Blood Glucose↗
PubMed1986

Non-enzymatic glycosylation influences Hb S polymerization.

In vivo glycosylated components of Hb S were isolated from red cell hemolysates of sickle cell anemia patients by application of affinity chromatographic and cation exchange chromatographic techniques. The total glycosylated fraction (GHb) of the whole hemolysate, Hb SIc, Hb So-glycosylated (formed mostly by glycosylation epsilon-NH2 groups of lysyl residues), and Hb So-nonglycosylated fractions were isolated in this manner. GHb contained about 33% Hb SIc and 42% Hb So (Hb So-glycosylated) and the rest was glycosylated Hb F and Hb A2. As expected, the binding of 2,3-DPG was affected only in Hb SIc and not in Hb So-glycosylated. Hb SIc and Hb So-glycosylated had higher solubility in concentrated phosphate solutions and had higher minimum gelling concentrations than the non-glycosylated form of Hb So. These effects are interpreted to be due to modification by glycosylation of specific sites that are directly or indirectly involved in the intermolecular contacts.

Anemia, Sickle Cell↗
PubMed1986

Glycosylated hemoglobin and protein levels in normal and diabetic pregnancies: relation to birth weight.

Glycosylated hemoglobin and protein were measured in maternal and cord blood of 24 normal, 19 class A, and ten insulin-treated diabetics using an affinity chromatographic technique. Maternal (intrapartum) glycohemoglobin and glycoprotein levels in the diabetics were not significantly different from those in normal controls, suggesting "tight" metabolic control in these patients. Compared with controls, cord blood glycohemoglobin and glycoprotein levels were significantly higher in insulin-treated, but not in class A, diabetics. The birth weight ratio correlated significantly only with maternal glycohemoglobin in insulin-treated diabetics. The results suggest that: even in well-controlled insulin-treated diabetics, the fetuses are hyperglycemic; maternal glycohemoglobin correlates with birth weight in insulin-treated diabetics; maternal glycoprotein determinations cannot be used to predict birth weight; hyperglycemia cannot be the sole determinant of fetal overgrowth in diabetic pregnancies; factors influencing fetal overgrowth in class A and insulin-treated diabetics may be different.

Adult↗
PubMed1985

New less temperature-sensitive microchromatographic method for the separation and quantitation of glycosylated hemoglobins using a non-cyanide buffer system.

This paper describes a new microchromatographic method on Bio-Rex 70 ion-exchanger, which enables the isolation and quantitation of the minor components hemoglobin AIa+b and hemoglobin AIc. The method relies on the equilibration of the resin in a polyphosphate buffer with a pH closer to the pKa of the carboxylic group of the resin, and on the adjustment of the sample pH at 5. This induces linear pH and ionic strength gradient during the elution of the hemoglobin components. The method is little affected by temperature between 20 and 30 degrees C, by the presence of the aldimine Schiff base, and is not expected to be greatly influenced by moderate fluctuations in pH and ionic strength of the buffers used. There was good correlation between the values obtained by the new micromethod and four procedures currently used, namely high-performance liquid chromatography (r = 0.96), and Trivelli Bio-Rex 70 macromethod (r = 0.99), bioaffinity chromatography (r = 0.98), and Isolab hemoglobin AI kit (r = 0.91). The method is reproducible, the interassay and the intra-assay correlation coefficients did not exceed 4.2%. The mean value for hemoglobin AIc was 4.6 +/- 0.35% for eleven non-diabetics and 8.9 +/- 2.6% for twenty-one diabetics.

Buffers↗
PubMed1985

Heterogeneity in the globin chain composition of a human minor fetal hemoglobin component.

The first hemoglobin found to contain an acetyl blocking group was the minor human fetal hemoglobin, Hb FI, present as 10-15% of the total fetal hemoglobin in umbilical cord blood red cells. Acetylation occurs at the amino-terminal glycine of the gamma-globin chain. Assays for the acetyl group by two different methods gave values less than the 2 per tetramer expected for a fully acetylated hemoglobin. We have purified acetylated fetal hemoglobin FIc to homogeneity. The globin chain composition of Hb FIc has been examined by both globin chain separation on CM-cellulose and by tryptic peptide mapping by HPLC. The identities of the gamma globin chains and of the gamma T-1 peptides were confirmed by amino acid analysis. Globin chain separation profiles showed the presence of 22.3 +/- 7.0% of gamma 0 globin (of the total gamma globin) in Hb FIc. Accordingly, the tryptic peptide maps of Hb FIc tetramers also showed the presence of a similar amount of gamma 0T-1 peptide. The gamma 0T-1 peptide was not present in the maps of isolated gamma Ic globin. It is evident that column purified Hb FIc contains a certain percentage of non-acetylated gamma-globin chains, thus indicating a hybrid globin chain composition for this minor fetal hemoglobin component.

Acetylation↗
PubMed1984

The relationship between fetal hemoglobin level and glycosylation in sickle cell disease.

Glycosylated hemoglobin (glyco Hb) was determined by affinity chromatography and Hb S1 and Hb F by Bio-Rex 70 chromatography in patients with sickle cell anemia, SC disease, S beta+-thalassemia, and S beta 0-thalassemia. SC and S beta-thalassemia patients had normal levels of glyco Hb whereas SS patients had significantly lower levels. Within each group of patients a direct correlation existed between Hb F and glyco Hb or Hb S1 levels. A similar relationship was noticed when glyco Hb and Hb F levels were compared in red cell populations of various densities (ages). Hb F seems to influence glycosylation through its effect on red cell survival.

Anemia, Sickle Cell↗
PubMed1984

Glycosylated hemoglobin and plasma protein in newborns of normal and diabetic women.

The glycosylated hemoglobin (glyco Hb) and the glycoprotein of the plasma were determined using affinity chromatographic techniques in cord blood and maternal blood of normal (Group I), White's Class A diabetic (Group II), and insulin-dependent diabetic (Group III) mothers. The results revealed significant increase of glyco Hb (P less than 0.005) and glycoprotein (P less than 0.005) in the newborns of Group III mothers in comparison to those of Group I. The glyco Hb of maternal blood in this group also showed significant increase (P less than 0.005) while the increase in Hb A1 and plasma glycoprotein were nonsignificant. All values for cord blood and maternal blood of White's Class A diabetics revealed no significant change from the normal group. We conclude that the fetuses of insulin-dependent diabetic mothers are hyperglycemic in utero.

Blood Glucose↗
PubMed1984

Glycosylated and acetylated hemoglobins in relation to gestational age and red cell age.

Cord blood samples were obtained at delivery from women at gestational periods of 30 to 36 weeks (preterm) and from a control group at 40 weeks of gestational age (term). Total glycosylated hemoglobin (GHb) was determined by affinity chromatography and the percentages of the minor Hbs FIa+b and FIc (of total Hb F) were determined by Bio-Rex 70 chromatography in whole blood samples and in red cell populations separated by Dextran 40 density gradient centrifugation. The absolute levels and the increase due to red cell aging of GHb, Hb FIa+b and Hb FIc were significantly reduced in the preterm samples compared to the term samples indicating decreased glycosylation in preterm fetus. When the nonglycosylated Hbs from term and preterm newborns were separated by Bio-Rex 70 chromatography after removal of the GHb by affinity chromatography, the acetylated form of Hb FIc also showed an increase with red cell aging indicating posttranslational enzymatic or nonenzymatic acetylation of Hb F during the entire life span of red cells. Moreover, as with GHb, the acetylated Hb was also decreased in the preterm newborns.

Cation Exchange Resins↗
PubMed1984

High-pressure liquid chromatographic separation of glycosylated and acetylated minor hemoglobins in newborn infants and in patients with sickle cell disease.

High-pressure liquid chromatography on a synchropak CM-300 column was used for separation and quantitation of glycosylated and acetylated minor hemoglobins and major hemoglobins in 15 newborn infants, 17 patients with sickle cell anemia and one each with SC condition, CC disease, Hb S heterozygosity, and Hb C heterozygosity. Hemoglobin Bart's, Fla1, Fla2, Flb, Flc, FO, Ald, AO, and A2 have been separated from newborn infants. Similarly, hemoglobins Fla, Flb, Flc, FO, Sla+b, Slc, A2, Sld, and SO were separated from patients with SS condition. Minor hemoglobins in all the samples were also separated by conventional Bio-Rex 70 chromatographic methods. The percentages of the various hemoglobin components determined by high-pressure liquid chromatography agreed rather well with those obtained by Bio-Rex 70 chromatography. However, the quality of the resolutions and the sharpness of the peaks were, in general, superior with the high-pressure liquid chromatography approach, which is much faster, requires significantly less sample than Bio-Rex 70 chromatography, and is particularly suitable for fast analytical chromatography of minor and major hemoglobins.

Acetylation↗