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T Asakura

Publications and source records attributed to T Asakura.

At least 379 records · Page 21Linked to original sources
PubMed1982

Polymerization of carbamylated deoxyhemoglobin S in concentrated phosphate buffer.

To study the effect of carbamylation on the polymerization of deoxyhemoglobin (HB) S, three types of NH2-terminal-carbamylated Hb S specifically modified at the NH2 termini at the alpha, beta, or all four subunit chains, alpha c2 beta sc2, and alpha 2 beta sc2, and epsilon-lysine-carbamylated Hb S were prepared by reacting Hb S with cyanate. The solubility of deoxy-Hb S in concentrated phosphate buffer was increased by carbamylation of the NH2-terminal residues of beta chains. Kinetic studies on the polymerization of purified carbamylated deoxy-Hb S showed that the length of the delay time prior to polymerization is related to solubility; carbamylated Hb S with higher solubilities exhibited longer delay times than those with lower solubilities. The delay times for alpha 2 beta sc2 and alpha c2 beta sc2 were prolonged 2-3- and 3-6-fold, respectively, as compared to those of native deoxy-Hb S in 1.8 M phosphate buffer. The logarithmic plot of reciprocal delay time versus hemoglobin concentration of alpha c2 beta s2, alpha 2 beta sc2, and epsilon-lysine-carbamylated deoxy-Hb S showed straight lines with slopes (n values) of 4.0, 3.8, 3.6, and 3.5, respectively. These values are slightly higher than the n value of native deoxy-Hb S (n = 2.7), suggesting that nuclei of carbamylated Hb S are larger than those of native deoxy-Hb S.

Buffers↗
PubMed1982

Effect of liganded hemoglobin S and hemoglobin A on the aggregation of deoxy-hemoglobin S.

The effect of the carbonmonoxy forms of Hb S and Hb A on the solubility and kinetics of the aggregation of deoxy-Hb S in concentrated phosphate buffer was studied. The delay time was prolonged exponentially when the ratios of CO-Hb S and CO-Hb A to deoxy-Hb S were increased. This increase in the delay time prior to aggregation can be explained by the decrease in the concentration of deoxy-Hb S. As with deoxy-Hb A, the n value for the delay time prior to the aggregation of deoxy Hb S was unaffected by CO-Hb S and CO-Hb A. Electrophoretic and spectrophotometric analyses of the composition of CO- and deoxy-Hbs A and S in the solution before and after aggregation showed that CO-Hb S co-polymerized with deoxy-Hb S but that CO-Hb A did not. The amount of CO-Hb S in the polymer phase depended on the initial fraction of the CO form of Hb S. The participation of CO-Hb S in the polymer phase was further confirmed by direct measurement of the absorption spectra of the polymer phase after it was dissolved in deoxygenated phosphate buffer. From these results, we concluded that nuclei are formed only from deoxy-Hb S, but that once nuclei are formed, CO-Hb S and deoxy-Hb A co-polymerize with deoxy-Hb S.

Carbon Monoxide↗
PubMed1982

Effect of calcium ion on the release of gamma-aminobutyric acid from synaptosomal fraction.

Brain synaptosomes released endogenous gamma-aminobutyric acid (GABA) in response to Ca2+. The release of GABA in response to 2.5 mM Ca2+ increased linearly with log[K+]0, showing that a membrane potential-dependent Ca2+ channel limits the GABA release. In the presence of Ca2+ ionophore, A23187, GABA release increased linearly with log[Ca2+]0 without altering the membrane potential of synaptosomes.

Animals↗
PubMed1982

Effect of cetiedil on cation and water movements in erythrocytes.

Cetiedil is a potential antisickling agent whose major effect appears to be at the erythrocyte membrane. To test the hypothesis that cetiedil alters cation transport, we studied the effect of the drug in promoting changes in cell water (Wc), cell sodium (Nac), and cell potassium (Kc). Results are quite different depending on the presence or near absence of intracellular ATP. With fresh cells, 100 microM cetiedil causes little in the net cation or water movements compared with control cells incubated for 2 h. At cetiedil concentrations greater than 100 microM, however, net movements of sodium and potassium increase considerably, and cell swelling results from a net Nac gain that exceeds a net Kc loss. All water movements can be accounted for by cetiedil-induced net cation movements. When 100 microM ouabain is added along with cetiedil, net Nac gain, net Kc loss, and net Wc gain are all increased compared with results obtained with cetiedil alone. External calcium inhibits cetiedil-induced changes in cation transport. With cells depleted of their ATP, cetiedil inhibits the typical potassium loss that occurs in the presence of external calcium; net sodium uptake changes little under these conditions, regardless of the presence or absence of external calcium. Our findings indicate a complex mode of action for cetiedil on the erythrocyte membrane, and support the hypothesis that the erythrocyte membrane, and support the hypothesis that the antisickling effect of the drug observed in vitro results from dilution of intracellular hemoglobin secondary to net salt and water gain.

Adenosine Triphosphate↗
PubMed1982

Kinetics of the polymerization of hemoglobin in high and low phosphate buffers.

Diluted solutions of deoxyhemoglobin S in concentrated phosphate buffer form aggregates or gels with a clear exhibition of a delay time. The aggregates can be liquified by cooling, bubbling with O2 or CO gas, or the dilution of phosphate buffer with water. These properties can be used as a simple method for studying the mechanism of polymerization and depolymerization of hemoglobins. The advantages of this method are: 1) The amount of hemoglobin sample required is only 1% to 5% of that required for the gelation of deoxy-Hb S in low phosphate buffer. 2) The kinetics can be measured turbidimetrically using an ordinary spectrophotometer. 3) The solubility of hemoglobin can be directly determined by taking the absorption spectrum of the supernatant solution after polymerization. 4) The polymer phase can be easily separated from the solution so that the amount and composition of the polymers can be analyzed. 5) The volume of the polymer phase is so small that excluded volume effect can be neglected. 6) The method can be applied to the study of polymerization of non-sickle hemoglobins and that of mixtures of sickle and non-sickle hemoglobins. The major question is whether the polymerization of hemoglobin in concentrated phosphate buffer is the same as that of deoxy-Hb S in low phosphate buffer. To answer this question, we studied the polymerization of Hb S, Hb A, Hb C Harlem, and Hb C in phosphate buffers of different molarities. We also studied the mechanism of the conversion of gels of these hemoglobins into crystals.

Buffers↗
PubMed1982

[A giant chondromyxoid fibroma originated from the right orbital roof.--A case report--].

The authors reported a case of giant chondromyxoid fibroma of the right anterior cranial fossa, arising from the right orbital lamina of frontal bone. A fifteen-year-old boy was admitted because of a recent history of the right exophthalmus and headache. Neurological examination was essentially negative except papilledema in the both optic fundi and the right olfactory disturbance. Skull plain x-ray films showed the bony destruction of the right supraorbital bone and the some of abnormal calcification in the right anterior cranial fossa. CT scan showed cystic low density spots surrounded by irregular ring-like high density areas in the right anterior cranial fossa. Operation was performed on two stages and the tumor was removed totally. The tumor was arising from the orbital lamina of the frontal bone. The size of resected tumor was 7x5x4 cm. The pathological examination confirmed the diagnosis of chondromyxoid fibroma. Postoperatively, the patient is fully schooling without any disturbance 2 years and 7 months after the discharge. In Japan, two cases of intracranial chondromyxoid fibroma have been reported in literature. The authors discussed the histology of chondromyxoid fibroma and the genesis of the membraneous bone origin of the intracranial chondromatous tumor.

Adolescent↗
PubMed1982

[Problems on recurrence after removal of teratoma in pineal region--an experience of recurrence of pineal teratoma 4 years after tumor removal].

A case of teratoma in the pineal region which recurred 4 years after the first tumor removal was reported in this paper. When the patient was 5 years old, she, complained of headache and vomiting, and visited our hospital. As a heterogeneous mass with no enhancement effect was found in the pineal region by CT scan, she was admitted on November 9, 1976. There was no abnormalities on physical examination but neurological examination revealed slight disturbance of conjugate upward gaze (Parinaud's sign). Left vertebral angiogram demonstrated posterior superior displacement of posterior choroidal artery and downward displacement of Rosenthal vein, but early venous filling and tumor stain were not seen. Under preoperative diagnosis of a teratoma in the pineal region, the first operation (left occipital craniotomy and total removal of the tumor) was performed on November 24, 1975. Microscopic examinations revealed that the removed tumor was a mature teratoma in the pineal region. Postoperative course was uneventful and discharged on December 20, 1975. The follow-up study was continued at outside clinic after discharge. There was no signs of recurrence until 3 years after the first operation, but on January, 1981 (4 years after the first operation), she suffered from severe headache and vomiting again and re-admitted to our hospital on February 3, 1981. There was no remarkable neurological deficits except for the mild intracranial hypertensive sign and no changes of findings on angiogram. But CT findings were markedly characteristic. It revealed a heterogenous mass with remarkable enhancement effect in the pineal region and ventricular enlargement. Because a mixed type (teratomatous and germinomatous) of pineal tumors was suspected from the CT findings, irradiation was done after V-P shunt. The tumor was reduced to half size after the first course of 2000 rads irradiation, but there is no more reduction of the size of the tumor following the second course of 2000 rads (total 4000 rads) irradiation. Against the residual tumor, tumor removal was performed on June 2, 1981. Microscopically, the most part of the resected tumor showed fibrous changes caused by irradiation and partially teratomatous compartment. From this result (radiosensitivity and histology) the authors assumed that the recurred tumor could be a mixed type (germinoma and teratoma) of pineal tumor. Postoperative course was uneventful except for a transient disturbance of conjugate upward gaze and she was discharged on June 25, 1981. And now, there is no signs of recurrence 12 months after the second operation. Conclusively, it will be stressed that we should continue follow-up study the case even after total removal of teratoma, especially in the pineal region. Moreover, it was considered that there is a possibility of the changes of the histological features on recurrence of the pineal teratoma. When germinomatous compartment is suspected, irradiation is the first choice and then microsurgical operation should be done against residual tumor.

Brain Neoplasms↗
PubMed1982

The effect of cetiedil on red cell membrane permeability.

We report the effects of cetiedil, a new antisickling agent, on red cell membrane permeability. With fresh red cells containing normal levels of intracellular ATP, cetiedil increases membrane permeability to both sodium and potassium. With drug concentrations from 100 to 500 microM, net sodium gain exceeds net potassium loss, and the cells quickly swell. Changes are identical with normal and sickle red cells. Membrane permeability returns to normal after washing the cells in buffer free of cetiedil. In the absence of phosphate, ouabain potentiates the cetiedil effect. With external phosphate present, the effect of cetiedil is also enhanced, but ouabain is without effect. Our findings support the idea that the antisickling effect of cetiedil observed in vitro is secondary to cell swelling.

Adenosine Triphosphate↗
PubMed1981

Effect of piracetam on sickle erythrocytes and sickle hemoglobin.

Piracetam, 2-oxo-1-pyrrolidine acetamide, inhibits sickling of red cells containing sickle hemoglobin (Hb S). The concentration required for 50% inhibition is about 300 mM. Addition of piracetam into the supersaturated Hb S solution in concentrated phosphate buffer prolongs the delay time prior to gelation. Piracetam shifts the oxygen equilibrium curves of blood toward the right, with a stronger effect at higher piracetam concentrations. Piracetam increases the viscosity of oxygenated cells but reduces the relative viscosity of deoxygenated sickle cells. The mechanism for the antisickling effect of piracetam will be discussed.

Anemia, Sickle Cell↗
PubMed1981

Aggregation and crystallization of hemoglobins A, S, and C. Probable formation of different nuclei for gelation and crystallization.

The oxy and carbonmonoxy forms of Hb A and Hb S formed aggregates or gels when dissolved in phosphate buffers at concentrations above their solubility and warmed rapidly to 30 degrees C from 0 degrees C. Kinetic studies showed that although deoxy-Hb A and deoxy-Hb S aggregated with a clear exhibition of a delay time, the oxy and carbonmonoxy forms of Hb A and Hb S did not show a delay time. These results suggest that the deoxy forms of Hb A and Hb S aggregate according to the nucleation-controlled mechanism, while oxy- and carbonmonoxyhemoglobins aggregate by the simple linear aggregation mechanism. It was also found that the gels or aggregates of deoxy-Hb A and carbonmonoxy-Hb S could be converted to crystals by further incubation. The rate of crystallization depended upon the concentration of hemoglobin in the supernatant, with faster crystallization at higher concentrations. Similar experiments with deoxy-Hb C (beta 6 Glu leads to Lys) showed that this hemoglobin also crystallized after aggregation, with both reactions accompanied by a delay time. The activation energy for the crystallization reaction of deoxy-Hb C (100 approximately 150 kcal/mol) was much higher than that for the aggregation reaction (20 kcal/mol). These results suggest that deoxy-Hb A, deoxy-Hb S, and deoxy-Hb C form two types of nuclei that are specific to the formation of gels (or aggregates) or crystals. The concentration of hemoglobin measured after completion of crystallization was much lower than that measured after gelation (or aggregation) and was independent of the initial hemoglobin concentration. This concentration is assumed to be the real solubility of hemoglobin.

Crystallization↗
PubMed1981

Investigations on epileptogenic lesions in relation between ages of the patients and seizure manifestation.

The purpose of this report is to extract the age factor from multiple contributing factors to seizure manifestations in 357 cases of the various intracranial lesions, of which the locations and the pathological types had already been proven. The age distribution of the intracranial lesions depended largely upon their biological properties. Nevertheless, it had been proven that the seizure manifestation differed by ages of the patients even in the identical lesions. The younger patients were apt to lapse into seizures which became more frequent than in the older patients. The types of seizures seemed to be converted from the generalized to the partial, as the patients go through a transition from childhood to adulthood. Recognition of such a seizure manifestation is especially important in order to detect as soon as possible epileptogenic lesions as a surgically treatable cause of chronic epilepsy.

Adolescent↗
PubMed1981

Precipitation of oxyhemoglobins A and S by isopropanol.

The isopropanol precipitation test is widely used for the detection of unstable hemoglobins. A method for accurately and easily determining the amount of hemoglobin precipitated is described. This study demonstrates that changes in incubation time, pH, temperature, and isopropanol and hemoglobin concentrations affect the precipitation of oxy Hb A and oxy Hb S. Hb S shows greater precipitation than Hb A with increasing time, temperature, and isopropanol concentrations. Both hemoglobins show equal increases in precipitation, with increases and decreases in pH and decreases in hemoglobin concentration. Comparison of the isopropanol precipitation test with the mechanical shake and heat denaturation tests reveals that the mechanical shake test is the easiest method to study the stability of Hbs A and S. Each of the tests may measure different parameters of stability. The use of all three tests in the evaluation of unstable hemoglobins should be considered.

1-Propanol↗
PubMed1981

Molecular stability of Hb Philly (alpha 2 beta 2 35(Cl) Tyr leads to Phe). Rhe relationship of hemoglobin stability to ligand state as defined by heat and mechanical shaking tests.

The molecular stability of Hb Philly (alpha 2 beta 2 35(Cl) Tyr leads to Phe) with different ligand states was compared with that of Hb A and Hb S using mechanical shaking and heat stability tests. The rates of mechanical denaturation of the oxy-forms of these hemoglobins decreased in the order of Hb S, Hb Philly, and Hb A, with relative ratios of 9.5: 5.6: 1.0. Upon oxidation to the met-forms, Hb Philly became mechanically most unstable, with ratios of 13.3: 23.0: 1.8, respectively. The deoxy-forms, of Hb A and Hb S were very stable, while that of Hb Philly was as unstable as the oxy-form. The addition of inositol hexaphosphate (IHP) to deoxy-Hb Philly stabilized the molecules. Since IHP restores the cooperative oxygen binding of Hp Philly, deoxy-Hb Philly appears to combine with IHP to change the quaternary structure required for cooperative oxygen binding and for stabilization of the molecule.

Drug Stability↗