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Biomedical subjects

K Oka

Publications and source records attributed to K Oka.

At least 523 records · Page 29Linked to original sources
PubMed1982

Programmed flow preparation of DNA-oligomers.

A new liquid phase preparation system for the phosphotriester method has been developed in which the usual batch process is carried out by flow manipulations. All processes including reactions, extraction and chromatography separation were performed in glass and PTFE tubing through which the solution was passed along a programmed course controlled by valves. A micro-computer programme was compiled for automatic control of the entire system.

Base Sequence↗
PubMed1981

Differential effects of the NADPH/NADP+ ratio on the activities of hexose-6-phosphate dehydrogenase and glucose-6-phosphate dehydrogenase.

The steady-state kinetics of rat liver hexose-6-phosphate dehydrogenase (beta-D-glucose: NAD(P)+ 1-oxidoreductase, EC 1.1.1.47) using glucose 6-phosphate and NADP+ as substrates is studied. NADPH has been found to inhibit the enzyme noncompetitively with respect to NADP+, and uncompetitively with respect to glucose 6-phosphate. At a given concentration of glucose 6-phosphate, the reaction follows the basic inhibition equation. This suggests the presence of the enzyme-NADP+-NADPH complex, and contrasts with the NADPH inhibition of glucose-6-phosphate dehydrogenase which is competitive with respect to NADP+. An attempt was made to estimate the in vivo activities of the two enzymes in rat liver in the presence of NADPH at various NADPH/NADP+ ratios. The results show that the two enzymes appear to be at about the same level of activity in normal rat liver where the coenzyme redox ratio is 110 and the glucose 6-phosphate concentration is 217 microM. Under the same conditions, but with 50 microM dehydroepiandrosterone, a potent inhibitor of glucose-6-phosphate dehydrogenase, but not of hexose-6-phosphate dehydrogenase, the latter enzyme is estimated to be 1.6-times as active as the former. Such differential effects of NADPH and steroids on the two enzymes may support our notion that hexose-6-phosphate dehydrogenase may have advantages over glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP+ 1-oxidoreductase, EC 1.1.1.49) in steroid-metabolizing tissues (the activity of hexose-6-phosphate dehydrogenase is not, or less, affected by steroids of NADPH).

Androgens↗
PubMed1981

Kinetic properties of tyrosine hydroxylase with natural tetrahydrobiopterin as cofactor.

A reproducible purification procedure of native tyrosine hydroxylase (L-tyrosine, tetrahydropteridine : oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2) from the soluble fraction of the bovine adrenal medulla has been established. This procedure accomplished a 90-fold purification with a recovery of 30% of the activity. This purified enzyme served for studying the kinetic properties of tyrosine hydroxylase using (6R)-L-erythro-1',2'-dihydroxypropyltetrahydropterin [(6R)-L-erythro-tetrahydrobiopterin] as cofactor, which is supposed to be a natural cofactor. Two different Km values for tyrosine, oxygen and natural (6R)-L-erythro-tetrahydrobiopterin itself were obtained depending on the concentration of the tetrahydrobiopterin cofactor. In contrast, when unnatural (6S)-L-erythro-tetrahydrobiopterin was used as cofactor, a single Km value for each tyrosine, oxygen and the cofactor was obtained independent of the cofactor concentration. The lower Km value for (6R)-L-erythro-tetrahydrobiopterin was close to the tetrahydrobiopterin concentration in tissue, indicating a high affinity of the enzyme to the natural cofactor under the in vivo conditions. Tyrosine was inhibitory at 100 microM with (6R)-L-erythro-tetrahydrobiopterin as cofactor, and the inhibition by tyrosine was dependent on the concentrations of both pterin cofactor and oxygen. Oxygen at concentrations higher than 4.8% was also inhibitory with (6R)-L-erythro-tetrahydrobiopterin as cofactor.

Adrenal Medulla↗
PubMed1981

An aberrant adenylate kinase isoenzyme from the serum of patients with Duchenne muscular dystrophy.

The sera from patients with human Duchenne (X-linked) progressive muscular dystrophy contain elevated adenylate kinase (ATP: AMP phosphotransferase, EC 2.7.4.3) activities, in addition to their characteristically high creatine kinase (ATP; creatine N-phosphotransferase, EC 2.7.3.2) activities. By agarose gel electrophoresis of human Duchenne dystrophic serum, the presence of an apparently normal human serum adenylate kinase together with a variant species of adenylate kinase was detected. The latter enzyme species appeared, in its mobility, to be similar to that of the normal human liver-type adenylate kinase. The presence of this aberrant liver-type adenylate kinase could also be demonstrated by characteristic (for the liver type) inhibition patterns with P1,P5-di-(adenosine-5')pentaphosphate, 5,5'-dithiobis(2-nitrobenzoate) and phosphoenolpyruvate. On the other hand, by inhibition titrations with an anti-muscle-type adenylate kinase, hemolysates from the erythrocytes of several Duchenne and Becker's dystrophics were found to contain approx. 96% muscle-type adenylate kinase and their serum approx. 97% muscle-type adenylate kinase. These same patients contained approx. 89% M-M type creatine kinase in their serum (by inhibition against anti-human muscle-type creatine kinase) indicative of the presence also of M-B plus B-B type active isoenzymes. All of these data can best be explained by the presence of a variant or mutant adenylate kinase isoenzyme in the dystrophic serum. This isoenzyme appears to resemble the liver type in its inhibition patterns with P1,P5-di(adenosine-5')pentaphosphate, 5,5'-dithiobis(2-nitrobenzoate) and phosphoenolpyruvate, and in its heat stability (compare also the agarose gel electrophoresis pattern); but structurally, it is a muscle type, or derived from a muscle type, as shown immunologically by inhibition reactions with anti-muscle-type adenylate kinase. Whether this is a fetal-type isoenzyme of adenylate kinase will require further investigation.

Adenine Nucleotides↗
PubMed1981

Cerebral haemorrhage in Moyamoya disease at autopsy.

Nineteen fatal cases of occlusion of the circle of Willis, so-called Moyamoya disease, were examined clinicopathologically. Fresh and massive cerebral haemorrhage was confirmed in 14 and cerebral infarcts of 4 of 19 patients. Among these 14 patients, massive haemorrhage was found in the basal ganglia, thalamus and hypothalamus of 9, and in the thalamus, cerebral peduncle and midbrain of 5. Pathologically, fibrosing stenoses or occlusions involved the circle of Willis and its major branches in all cases. In 13 of 17 patients numerous collateral channels, muscular in type, paralleled the circle, bypassing the occluded natural passages, Rupture of dilated small muscular collateral arteries was demonstrated in fresh and old haemorrhagic lesions in 3 of the 14 patients. Saccular aneurysm of cerebral arteries in the subarachnoid spaces was present in two of the 19. No rupture involved the perforating arteries in the subarachnoid space. These findings strongly suggest that in patients with Moyamoya disease rupture of overgrown perforating arteries as collaterals in brain may be main cause of single or repeated cerebral haemorrhage. Stenoses or occlusions of these perforators are presumably an important factor in the occurrence of cerebral infarcts.

Adolescent↗
PubMed1981

Type 1 glycogenosis with contracted kidneys and liver cell adenoma.

A 22-year-old man with type 1 glycogenosis died of renal and respiratory failure. Postmortem examination revealed deposition of glycogen in liver cells, a liver cell adenoma, bilateral contracted kidneys with scent glycogen deposition, and pulmonary edema. The development of liver cell adenoma was thought to be related to underlying metabolic disorder and contracted kidneys were considered to be the sequel of massive glycogen deposition in the renal tubular epithelium.

Adult↗
PubMed1981

Fibrinolysis-inhibitory activity of cultured human cancer cell lines.

Fibrinolysis-inhibitory activity was estimated in the lysates of 21 lines of cultured human cancer cells, from which plasminogen activator activity had veen effectively eliminated by affinity chromatography. Inhibitory activity against urokinase varied from one line to another. Three lines of lung cancer and 1 line of urinary bladder cancer showed high inhibitory activity against urokinase. Two lines of lung cancer, 3 lines of gastric cancer, 1 line of renal cancer and 1 line of renal pelvic cancer showed moderate inhibitory activity. Since inhibitory activity against plasmin was not apparent in all the cell lines tested, this activity seemed to be directed selectively towards urokinase. No inhibitory activity against urokinase was detected in 4 lines of lung cancer, 5 lines of gastric cancer and 1 line of renal cancer. There was no specific correlation between the degree of inhibitory activity against urokinase and the histological cell types of the original tumors of the cultured cell lines.

Chromatography, Affinity↗
PubMed1980

Inhibition of tyrosine hydroxylase, a Fe(II)-stimulated monooxygenase, by bleomycin.

Tyrosine hydroxylase was shown to be inhibited in vitro by bleomycin. At a concentration of 1 X 10(-4) M, copper-free BLM-A2 inhibited tyrosine hydroxylase activity by 50%, and all other bleomycins investigated including copper-bound BLM-A2 showed similar degrees of inhibition of tyrosine hydroxylase. The kinetic data have shown that the inhibition by BLM-A2 is competitive with a tetrahydropterin cofactor (6-methyl-tetrahydropterin) and uncompetitive with tyrosine. The inhibition of tyrosine hydroxylase by bleomycin was not reversed by Fe(II) or superoxide dismutase. These results suggest that the inhibition may be neither due to the chelating action of bleomycin with ferrous ion nor due to the production of superoxide and hydroxyl radicals by the formation of an oxygen-labile Fe(II)-bleomycin complex.

Adrenal Glands↗
PubMed1979

Intravascular coagulation in autopsy cases with liver diseases.

184 autopsy cases with liver diseases were examined clinicopathologically with special reference to the incidence and distribution of microthrombi and classic thrombi in various organs. Microthrombi and/or classic thrombi were found in one or more organs in 50.0% to 59.4% of the patients with various liver diseases. But only 4 among 184 patients had many microthrombi in more than three organs and the incidence of disseminated intravascular coagulation seemed to be low in autopsy cases with liver diseases. Incidence of microthrombi showed no significant difference in the groups with and without portal vein thrombosis. Hemorrhage in the upper alimentary tracts of the patients with liver cirrhosis did not seem to develop by disseminated intravascular coagulation. Consumption of clotting factors in liver diseases seemed to occur by thrombus formation in portal vein and esophageal varices and by hemorrhage in various organs.

Autopsy↗
PubMed1979

Highly sensitive assay for tyrosine hydroxylase activity by high-performance liquid chromatography.

A highly sensitive assay for tyrosine hydroxylase (TH) activity by high-performance liquid chromatography (HPLC) with amperometric detection was devised based on the rapid isolation of enzymatically formed DOPA by a double-column procedure, the columns fitted together sequentially (the top column of Amberlite CG-50 and the bottom column of aluminium oxide). DOPA was adsorbed on the second aluminium oxide column, then eluted with 0.5 M hydrochloric acid, and assayed by HPLC with amperometric detection. D-Tyrosine was used for the control. alpha-Methyldopa was added to the incubation mixture as an internal standard after incubation. This assay was more sensitive than radioassays and 5 pmol of DOPA formed enzymatically could be measured in the presence of saturating concentrations of tyrosine and 6-methyltetrahydropterin. The TH activity in 2 mg of human putamen could be easily measured, and this method was found to be particularly suitable for the assay of TH activity in a small number of nuclei from animal and human brain.

Animals↗
PubMed1979

Thromboplastic and fibrinolytic activities of cultured human cancer cell lines.

Thromboplastic and fibrinolytic activities of 14 lines of cultured human cancer cells were estimated by modified Astrup's methods. High tissue thromboplastic activity was found in one line of urinary-bladder cancer, 2 lines of gastric cancer and one line of lung cancer, but no activity was found in 6 lines of lung cancer. High fibrinolytic activity was noted in one line of gastric cancer and 2 lines of lung cancer, but no activity was seen in 6 lines of lung cancer and one line of gastric cancer. No plasmin activity was found. The tumour cell lines could be classified into 3 groups on the basis of the 2 activities. Cancer cell lines could also be classified into 2 groups: with high or low release of thromboplastin into culture media. Fibrinolytic activity was found in the culture media of all cell lines with high fibrinolytic activity. Fibrinolytic activity, but not thromboplastic activity, seemed to be influenced by the constituents of culture media. No definite correlation was found between the 2 activities and the histological types of the parent tumours of the cultured cells.

Blood Coagulation↗