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Biomedical subjects

S Okuno

Publications and source records attributed to S Okuno.

At least 235 records · Page 13Linked to original sources
PubMed1984

Urinary excretion rate of antithrombin III related antigen in cerebral stroke.

The urinary excretion rate of antithrombin III related antigen (AT III RA) was examined in cerebral stroke. The excretion rate of AT III RA in cerebral hemorrhage (CH) was 12.33 +/- 1.61 X 10(-4) ml/min. The patients with CH were further classified into two groups: in group CH-I, whose consciousness state was stupor or further deteriorated including coma on admission, the excretion rate of AT III RA was 18.08 +/- 2.50 X 10(-4) ml/min. In group CH-II, whose consciousness state was clear on admission, the excretion rate of AT III RA was significantly lower than that in CH-I (6.20 +/- 1.56 X 10(-4) ml/min). The excretion rate in cerebral thrombosis (CT) was 1.96 +/- 0.25 X 10(-4) ml/min, which was significantly lower than that in CH. The excretion rate of AT III RA in both CH and CT was significantly higher than that in the healthy control group (0.29 +/- 0.04 X 10(-4) ml/min). Thus, AT III may change dynamically in cerebral stroke.

Antigens↗
PubMed1984

The activity of tyrosine 3-monooxygenase is usually suppressed by an endogenous factor in brain.

Tyrosine 3-monooxygenase activity of the crude extract from rat striatum had a sharp pH optimum at pH 5.6 and showed almost no activity at pH 7 and higher. When the crude extract was adjusted to pH 5.2, the resulting precipitate showed high activity in the pH range of 6 to 7.5. Incubation of the acid-precipitated fraction with the acid-soluble fraction resulted in a remarkable decrease in the enzyme activity, as assayed at a neutral pH. These findings suggest that there is an endogenous factor inhibiting the activity of tyrosine 3-monooxygenase in rat brain.

Animals↗
PubMed1984

Purification and characterization of rat dopamine beta-monooxygenase and monoclonal antibodies to the enzyme.

Dopamine beta-monooxygenase was extensively purified from rat adrenal. The specific activity of the final preparation was approx. 1500 nmol/min per mg protein, which was much higher than the highest yet reported. As judged by gel filtration on Ultrogel AcA22, SDS-polyacrylamide gel electrophoresis, and cross-linking studies, the enzyme appeared to be composed of four identical subunits, each possessing a molecular weight of 88 000. The isoelectric point of the enzyme was estimated to be pH 6.6 in the presence of 8 M urea. Spleen cells from BALB/c mice immunized with rat dopamine beta-monooxygenase were fused to P3-X63-Ag8-653 mouse myeloma cells. From 55 hybrid cells, 10 stable clones secreting anti-dopamine beta-monooxygenase antibody were obtained. Antibody from one clone was coupled to CNBr-activated Sepharose 4B and the monoclonal antibody-Sepharose was shown to be very useful to isolate rat dopamine beta-monooxygenase from crude preparations.

Adrenal Medulla↗
PubMed1984

Role of calmodulin in neurotransmitter synthesis.

Tyrosine 3-monooxygenase (EC 1.14.16.2) and tryptophan 5-monooxygenase (EC 1.14.16.4) are generally believed to be the rate-limiting enzymes in the biosynthesis of the neurotransmitters, catecholamines and serotonin, respectively, and therefore the regulation of their activities is of particular importance. At least three calmodulin-dependent protein kinases differed in their molecular weights and substrate specificities, designated I, II, and III in the order of decreasing molecular weight, in rat brain cytosol. Among them, calmodulin-dependent protein kinase II with a molecular weight of about 540,000 appeared to occur only in the nervous tissues. Kinase II was found, on the one hand, to phosphorylate tyrosine 3-monooxygenase and tryptophan 5-monooxygenase, leading to the activation of these monooxygenases in the presence of activator protein and, on the other hand, to phosphorylate tubulin and microtubule-associated protein 2, which results in disassembly of the microtubules that had been assembled. These results suggest the possibility that both the secretion and biosynthesis of monoamine neurotransmitters stimulated by Ca2+ influx in the nervous system may be regulated by calmodulin-dependent protein kinase II via the phosphorylation of microtubule proteins and the phosphorylation of the monooxygenases that are the rate-limiting enzymes in the biosynthesis of the neurotransmitters.

Amines↗
PubMed1983

Accurate assay of dopa decarboxylase by preventing nonenzymatic decarboxylation of dopa.

The nonenzymatic decarboxylation of dopa was completely blocked by both 2-mercaptoethanol and EDTA together over the wide range of pH. This finding made it possible to measure the activity of dopa decarboxylase precisely even at an alkaline pH value. The pH optimum of dopa decarboxylase was found to be pH 7.0 and the Km value for dopa was determined to be 4 X 10(-5) M.

Animals↗
PubMed1982

Determination of alpha 2-plasmin inhibitor in body fluids.

A sensitive method was developed to determine alpha 2 PI at very low concentrations. The minimal measurable concentration of alpha 2 PI was 0.5 ng/assay tube. Using this method, the alpha 2 PI in plasma, urine, amniotic fluid and cerebrospinal fluid was estimated. The mean values and standard deviation for plasma were 5.63 +/- 1.34 mg/dl in 25 males, and 5.29 +/- 1.62 mg/dl in 8 females; in the urine, 0.46 +/- 0.41 microgram/dl in 82 male samples, and 0.69 +/- 0.27 microgram/dl in 8 female samples; in amniotic fluid, 4.13 +/- 2.38 micrograms/dl in 16 samples; and in cerebrospinal fluid, 24.4 +/- 6.6 microgram/dl in 9 samples. The alpha 2 PI level in amniotic fluid was not correlated with the state of the pregnant mother, with that of the baby, or with the protein content or pH of the amniotic fluid.

Amniotic Fluid↗
PubMed1982

Purification and some properties of tyrosine 3-monooxygenase from rat adrenal.

Tyrosine 3-monooxygenase was purified to homogeneity, as judged by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, from rat adrenal. The specific activity of the final preparation was approximately 1,600 nmol min-1 mg protein-1, which was much higher than the highest yet reported. The enzyme was markedly stabilized in the presence of glycerol, Tween 80 and EDTA. As judged by gel filtration on Ultrogel AcA 34, sodium dodecyl sulfate/polyacrylamide gel electrophoresis and cross-linking studies, the enzyme appeared to be composed of four identical subunits, each possessing a molecular weight of 59,000. The isoelectric point of the enzyme was estimated to be 6.7 in the presence of 8 M urea and 6.6 in its absence. Amino acid analysis of the enzyme revealed a fairly high content of serine residues in this protein. Purification of the enzyme caused changes in the kinetic properties of the enzyme. The Km for 2-amino-4-hydroxy-6-methyl-5,6,7,8-tetrahydropteridine decreased from 220 microM to 58 microM. The pH profile for the enzyme activity became more broad and the pH optimum was changed from an acid pH to a neutral pH. Although polyanions, such as heparin and dextran sulfate, markedly stimulated the activity of crude enzyme by increasing the V, they were much less effective in the activation of purified enzyme. A marked stimulation of the enzyme activity by phospholipids, such as phosphatidylserine, phosphatidylinositol, phosphatidylcholine and phosphatidylethanolamine, were not observed in both pure and crude preparations even at low concentrations of the pterin cofactor.

Adrenal Medulla↗
PubMed1981

Inactivation of tyrosine 3-monooxygenase by acetone precipitation and its restoration by incubation with a sulfhydryl agent and iron.

The acetone precipitation of a partially purified tyrosine 3-monooxygenase (L-tyrosine, tetrahydropteridine: oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2) resulted in the complete loss of enzymatic activity. The enzymatic activity was restored by incubation with iron and dithiothreitol. The restoration of the activity was a pH-, temperature- and time-dependent reaction. Since cobalt, nickel, copper, zinc, manganese, cadmium, magnesium calcium and barium ions were all ineffective in restoring activity, iron ion appeared to be specifically required in the restoration of the enzyme activity. Dithiothreitol could be partially replaced in the restoration step by glutathione, 2-mercaptoethanol or cysteine.

Acetone↗