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D Elbaum

Publications and source records attributed to D Elbaum.

29 records · Page 2Linked to original sources
PubMed1978

Hydergine and vincamine derivative LD 4298 exhibit no anti-sickling properties in vitro.

Amongst the treatments proposed for Sickle Cell disease Ergot derivatives and extracts from Pervinca have been proposed. We have studied in vitro the effect of Hydergine and LD 4298 on Sickle Cells and Sickle Hemoglobin according to the following four parameters : percentage of sickling, potassium leak, minimum gelation concentration and speed of gelation. In these studies no anti-sickling effect was detected. Moreover Hydergine at 50 microgram/ml increased spontaneous potassium loss without any anti-sickling effect. One can conclude that these two drugs have no effect on sickling.

Anemia, Sickle Cell↗
PubMed1977

Ligand kinetics of hemoglobin S containing erythrocytes.

Oxygen uptake of fully deoxygenated sickle (SS) erythrocytes is slower than that of normal (AA) erythrocytes, as demonstrated by the half-times of the overall oxygenation reactions: at 25 degrees in an isotonic phosphate buffer the normal red cells have a t1/2 = 82 +/- 4.7 msec, as compared to sickle red cells where t1/2 = 135 +/- 17.6 msec. The effects of temperature, extracellular osmolality, and the presence of an antisickling agent (n-butylurea) on the rate of red cell oxygenation strongly suggest that the differences in oxygenation rates encountered with sickle red cells is directly related to the intracellular polymerization of deoxyhemoglobin S.

Antisickling Agents↗
PubMed1977

Some properties of Hb G San Jose (beta7 glu replaced by gly): comparisons with Hb S.

Hb G San Jose (beta7 glu leads to gly) was studied with respect to oxygen affinity, Bohr effect, surface activity in dilute aqueous solutions, mechanical precipitability, heat stability and its ability to copolymerize in the deoxy form with Hb S. Oxygen affinity, Bohr effect, and polymerization with Hb S were found to be identical to those of Hb A when studied under the same conditions. However, surface activity and mechanical precipitation rates of the oxyconformers closely resembled those of oxyhemoglobin S. Hb G San Jose was also found to be slightly more unstable with heat than Hb A, although the instability was not detected by the usual incubation method of 1 hr at 50 degrees and higher temperatures were needed to elicit this difference. It is concluded that the ability to polymerize and the presence of increased surface activity are distinct and separable attributes of hemoglobin mutants. The finding that mixtures of Hb S and Hb G San Jose gel like mixtures of Hb S and Hb A supports the conclusion that only one beta 6 Val combining site per tetramer is required for polymer formation.

Adult↗
PubMed1976

Aggregation of deoxyhemoglobin S at low concentrations.

The self-association of deoxyhemoglobin S was measured in dilute solutions (0 to 5 g/dl) by Rayleigh light scattering at 630 nm and osmometry in 0.05 M potassium phosphate buffer (pH 7.35). Weight and number average molecular weights (Mw and Mn, respectively) and the second or higher virial coefficients, B' were determined. No experimentally significant differences were observed between oxy- and deoxy-Hb S up to the concentration of 2 g/dl; their apparent average molecular weights were within experimental error. Above that concentration, both Mn and Mw of deoxy-Hb S were significantly different from that of oxy-Hb S. The negative second viral coefficent of deoxy-Hb S, observed by both techniques, is consistent with the self-association of this protein. The lack of effect of 0.4 M propylurea on the state of aggregation and the significant influence of 0.1 M NaCl suggests that polar interactions are involved in formation of these aggregates.

Hemoglobin, Sickle↗
PubMed1976

Surface activity of hemoglobin S and other human hemoglobin variants.

The kinetics of surface pressure change (deltapi vs. t isotherms) were determined for several single point mutations of the human hemoglobin system. It was observed that hemoglobin S and hemoglobin CHarlem (both containing beta6 Glu leads to Val substitutions) have a specific behavior at the water-air interface: their extent of surface pressure change is larger than for hemoglobin A, hemoglobin C and hemoglobin Korle Bu (beta73 Asp leads to Asn). In addition, hemoglobin S seems to occupy a larger area per molecule than hemoglobin A. The conformational requirements for this property, in addition to the beta6 Val substitution, appear to be the liganded state of the betas chain in the tetramer. Electrostatic, hydrogen bonding and hydrophobic interactions are involved in determining the surface activity of a hemoglobin molecule. The differences between the surface activity of oxyhemoglobin S and oxyhemoglobin A could be the basis for their differences in mechanical precipitability, although other factors may play a role.

Asparagine↗
PubMed1976

The conformational requirements for the mechanical precipitation of hemoglobin S and other mutants.

The mechanical stability of human hemoglobin mutants was studied for the specific effects of single and double amino acid substitutions, the ligand state of each chain, and the effect of hybrids between oxy and cyanmet partners on precipitability. It was found that the beta6Glu leads to Val and the beta73 Asp leads to Asn mutations increased the degree of mechanical precipitation in the liganded but not in the deoxy form. When these mutations occurred on the same chain, the effects were approximately additive. Heat labile mutants such as Hb Gun Hill and Hb Leiden exhibited mechanical instability, but probably through a different mechanism, as very little dependence on ligand state was apparent. Studies with valency hybrids of HbS(alpha2 betas2-and-alpha2 betas2 where = cyanmet) revealed that instability was primarily determined by the state of the betas chain, which must be liganded to confer instability on the tetramer. A good agreement between surface activity and mechanical precipitability of these mutants has been found.

Chemical Precipitation↗
PubMed1976

Molecular and cellular effects of antisickling concentrations of alkylureas.

Alkylureas are capable of inhibiting sickling in vitro and the gelation of solutions of hemoglobin S at concentrations between 0.05 and 0.1 M with increasing effectiveness that is directly proportional to the length of the alkyl chain (butyl greater than propyl greater than ethyl greater than methyl). 6The inhibitory effect is independent of pH between 6.5 and 7.5 and is a process driven by entropy. The alkylureas at concentrations of 0.1 M have minimal effects on several erythrocyte functions. Oxygen equilibria, osmotic fragility, reduced glutathione content, and glutathione reductase activity are totally unaffected, while pyruvic kinase activity is decreased only by butylurea by about 20%, and glucose-6-phosphate dehydrogenase activity is decreased progressively to a maximum of 30% in direct proportion to the length of the alkyl chain. Alkylureas not only inhibit sickling but are also capable of desickling erythrocytes that have been maintained in the deoxygenated state. They have little effect on several erythrocyte functions at antisickling concentrations, but their toxicity must be evaluated before they can be examined as potential therapeutic agents for the treatment or prevention of acute episodes in sickle cell anemia.

Erythrocytes, Abnormal↗
PubMed1975

Observations on the mechanical precipitation of oxy Hb S and other mutants.

Oxyhemoglobin S exhibits greater mechanical instability than oxyhemoglobin A. The rate of precipitation of Hb S when agitated by vortexing depends upon the geometry of the tube, the volume of the hemoglobin solution, and the concentration of hemoglobin. The rate of precipitation is inversely related to concentration. Precipitation is inhibited by temperatures near 4 degrees C and alkylureas whose protective capacity is approximately proportional to the carbon chain length of the alkyl group. Blocking the beta93 -SH group with parahydroxymercuribenzoate has only a small enhancing effect on the precipitation rate. Other mutants such as Hb Gun Hill, Leiden, (both heat unstable), and C-HARLEM are also unstable. In the case of C-HARLEM, the precipitation rate is greater than that for Hb S. The heat-unstable mutants are not as well protected by cold temperatures or alkyl ureas. D2O has only a minor stabilizing effect on hemoglobin S, but NaCl and related salts markedly enhance precipitation at concentrations of 0.5 M. It is concluded that mechanical instability of oxyhemoglobins is a multifactorial process involving surface denaturation, pH, ionic strength, hydrophobic interactions, protein conformation, and primary protein structure. This phenomenon will require more extensive investigation.

Carbon Radioisotopes↗
PubMed1974

Effect of alkylureas on the polymerization of hemoglobin S.

Alkylureas (methyl-, ethyl-, propyl-, and butyl-) can inhibit both the gelation of deoxyhemoglobin S and red cell sickling without denaturation of the hemoglobin or intrinsic alteration of its oxygen affinity. This effect is directly proportional to the length of the alkyl chain and substantiates the importance of hydrophobic interactions in the polymerization of hemoglobin S. In addition, it opens the possibility that further systematic investigations with these compounds will help quantitate the role of hydrophobic interactions in this system so as to further our understanding of the polymerization of deoxyhemoglobin S.

Chemical Phenomena↗