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Biomedical subjects

T Asakura

Publications and source records attributed to T Asakura.

At least 361 records · Page 20Linked to original sources
PubMed1983

Effect of chloride ion on the oxygen affinity of hemoglobin York (alpha 2 beta 2(146)Pro) and S-York hybrid hemoglobin (alpha 2 beta S beta York). Role of the beta 82 lysyl and beta 146 histydyl residues in chloride binding to hemoglobin.

We estimated the relative role of various chloride binding sites in determining the oxygen affinity of hemoglobin using abnormal hemoglobins such as Hb York (Hb Y) (alpha 2 beta 2(146)Pro), Hb Malmö (Hb M) (alpha 2 beta 2(97)Gln), and Hb S and chemically modified hemoglobins such as cross-linked Hb S, Hb Y, and asymmetrical SY hemoglobin with bis(3,5-dibromosalicyl)fumarate. The chloride effect on the p50 values of Hb S and Hb M was identical to that of Hb A. In contrast, the effect of chloride on the p50 values of Hb Y was only 20% of that of Hb A. Cross-linking between the two beta 82 lysyl residues with fumarate decreased the chloride effect by 40%. The effect of chloride on cross-linked Hb Y, in which both beta 82 lysyl and beta 146 histidyl residues were modified, was unchanged from that on Hb Y (20% of Hb A). The effect of chloride on the p50 value of SY asymmetrical hybrid hemoglobin was 40% of that of Hb A or Hb S, which is midway between the values obtained for cross-linked Hb S and Hb Y. From these results, the contribution of beta 146 His and beta 82 Lys on oxygen affinity by binding of chloride was calculated to be 40% each; the remaining 20% chloride effect was attributed to alpha 1 Val.

Chlorides↗
PubMed1983

Dielectric constant of sickle cell hemoglobin. Dielectric properties of sickle cell hemoglobin in solution and gel.

The dielectric constants of sickle cell hemoglobin were determined before and after gelation. The dielectric properties of oxy and deoxy sickle cell hemoglobin in solution are nearly identical to those of oxy and deoxy hemoglobin A. Only in the gel state did deoxy sickle cell hemoglobin display dielectric behavior different from that in solution. Upon gelation of deoxy sickle cell hemoglobin, the dielectric constant showed a marked decrease, and the relaxation frequency shifted towards higher frequencies. This result suggests that dielectric constant measurement can be used for the investigation of the kinetics of polymerization of sickle cell hemoglobin molecules. Despite the marked decrease in the dielectric constant, deoxy sickle cell hemoglobin still showed a well-defined dielectric dispersion even in the gel state. This indicates that individual molecules have considerable freedom of rotation in gels. It was observed that the dielectric properties of gelled deoxy sickle cell hemoglobin were affected by electrical fields at the level of 10 to 20 V/cm. This observation suggests that electrical fields of moderate strengths are able to perturb the gel structure if the system is near the transition region. The non-linear electrical behavior of gelled sickle cell hemoglobin will be discussed further in subsequent papers.

Electric Conductivity↗
PubMed1983

Desickling of sickled erythrocytes by pulsed radio-frequency field.

Electric fields were found to deform sickled erythrocytes. When the intensity of applied fields exceeded a threshold value, sickled erythrocytes transformed into a spherical shape. Prolonged application of the field usually caused hemolysis of erythrocytes. Deformation of red blood cells could be partly reversed if the field was turned off at an early stage. The cause of desickling may be the interaction of the field with the erythrocyte membrane and also with gelled intracellular hemoglobin S molecules.

Anemia, Sickle Cell↗
PubMed1983

Multiple nature of polymers of deoxyhemoglobin S prepared by different methods.

Studies on the aggregation of deoxy-Hb S in concentrated phosphate buffer revealed the formation of three types of polymers, the difference depending on the method employed for polymerization: 1) random or linear polymers without birefringence, 2) helical polymers with birefringence, and 3) crystals. Random or linear polymers were formed when oversaturated deoxy-Hb S was polymerized by the so-called salting out or isothermal method. Helical polymers were formed when oversaturated deoxy-Hb S (120% of the solubility) was polymerized by the temperature jump method. Crystals were formed preferentially by agitation of the sample during the polymerization below 12 degrees C. The solubilities of deoxy-Hb S measured after preparation of these three types of polymers were different, as were the activation energies for the formation of the three polymers. When a mixture of deoxy- and CO-Hb S was crystallized, the crystalline phase did not contain CO-Hb S molecules. To study the relationship among these three types of polymers and red cell sickling, the morphology of erythrocytes was studied after deoxygenation by several different methods. When erythrocytes were prepared by deoxygenation with 2% sodium dithionite at 30 degrees C, a condition similar to that for the isothermal method, red cells did not form the typical sickle shape but rather an irregular shape. In contrast, with the same experiments carried out by using the temperature jump method, typical sickle-shaped cells were formed. These data suggest that the morphological difference may be attributed to the different types of polymers formed inside erythrocytes.

Anemia, Sickle Cell↗
PubMed1983

Aggregation of hemoglobin S modified by bifunctional imidoesters.

Sickle hemoglobin (Hb S) was cross-linked by two types of bifunctional imidoesters, dimethyladipimidate (DMA) and dimethyl-3,3'-dithiobispropionimidate (DTBP). These modified hemoglobins were separated into monomer, dimer and polymer fractions by gel filtration. All of these modified hemoglobins showed extremely left-shifted oxygen equilibrium curves with no cooperativity. The stabilities of these hemoglobins were also decreased. The solubilities of these modified hemoglobins in high-phosphate buffers were lower than those of native Hb S. Studies on the kinetics of the aggregation of these modified hemoglobins showed that intracross-linked Hb S with DMA and DTBP (DMA- and DTBP-modified monomeric Hb S) still retained the capability of aggregation with a delay time, while intercross-linked Hb S with DMA and DTBP (DMA- and DTBP-modified oligomeric Hb S) aggregated without a delay time. When the kinetics of aggregation was measured for mixtures of modified and native deoxy-Hb S, DMA-modified monomeric deoxy-Hb S shortened the delay time prior to aggregation of native deoxy-Hb S. The other modified deoxy-Hb S did not affect the delay time, suggesting that these modified oligomeric hemoglobins neither participate in the formation of nuclei nor copolymerize with native deoxy-Hb S.

Cross-Linking Reagents↗
PubMed1983

4-Aminobutyraldehyde as a substance convertible in vivo to GABA.

[2,3-3H]4-Aminobutyraldehyde ([3H]ABAL) was injected subcutaneously into mice, which were sacrificed at various intervals following injection. [3H] gamma-Aminobutyric acid ([3H]GABA) synthesized in vivo from [3H]ABAL was extracted from the brains, separated, and quantitated. The results showed that in the brain, injected [3HABAL was rapidly transformed into [3H]GABA. [3H]ABAL may penetrate the blood--brain barrier into the central nervous system and then be oxidized to [3H]GABA.

Aldehydes↗
PubMed1983

Formation of cross-linked asymmetrical hybrid hemoglobins by double-headed aspirin.

Double-headed aspirin [bis(3,5-dibromosalicyl)fumarate] selectively cross-links hemoglobin molecules between Lys 82 beta 1 and Lys 82 beta 2 and increases solubility of deoxy-Hb S (Walder et al., J. Mol. Biol., 141:195, 1980 and Kikugawa et al., J. Biol. Chem., 257:7525, 1982). We reacted this reagent with the mixture of Hb A and Hb S and the mixture of Hb S and Hb York (beta 146His replaced by Pro). Cross-linked asymmetrical hybrid hemoglobins (alpha 2 beta - beta S and alpha 2 beta Y - beta S) were produced in high yields in addition to the cross-linked parent hemoglobin molecules. Results on electrophoresis, gel electrofocusing, ion exchange column chromatography, mechanical stability and oxygen binding properties showed that the cross-linked asymmetrical hybrid hemoglobins had properties intermediate between those of the cross-linked parent hemoglobins. Oxygen affinities of the cross-linked asymmetrical hybrids were not affected by the addition of 2,3-diphosphoglycerate (DPG) or inositol hexaphosphate, probably due to the presence of a fumaryl group at the DPG binding site.

Aspirin↗
PubMed1983

Characterization and properties of Hb York (beta 146 His leads to Pro).

A second case of Hb York (beta 146 His leads to Pro), was discovered in a patient with polycythemia. The oxygen equilibrium curves (OEC) of red cell suspensions in a buffer (pH 7.4) at 37 degrees C revealed a biphasic curve with a P50 of only 12.5 mm Hg (normal value: 26.5 +/- 1.0 mm Hg). The purified Hb York had an extremely high affinity for oxygen with diminished cooperativity and decreased Bohr effect. The oxygen affinity was significantly reduced by inositol hexaphosphate. Molecular stability studies by mechanical shaking of various liganded forms of Hb York revealed stabilities between those of Hb A and Hb S. Isolated beta Y-subunits were more unstable than beta A-subunits at every pH examined. Hb York was 1.4 times more unstable than Hb A in 18.9% isopropanol.

Chemical Phenomena↗