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Biomedical subjects

K Oba

Publications and source records attributed to K Oba.

At least 73 records · Page 4Linked to original sources
PubMed1989

Effect of route of administration in the micronucleus test with potassium bromate.

The effect of intraperitoneal injection (i.p.) versus oral gavage administration (p.o.) of potassium bromate was examined using the micronucleus test in 2 strains of male mice (MS/Ae and CD-1). First, a small acute toxicity test and a pilot micronucleus experiment were performed to determine the appropriate dose range and sampling time for the full-scale micronucleus test. The full-scale test was carried out using doses of 18.8, 37.5, 75, and 150 mg/kg in the i.p. test and of 37.5, 75, 150, and 300 mg/kg in the p.o. test. The sampling time was 24 h for both mouse strains. Potassium bromate induced micronucleated polychromatic erythrocytes (MNPCEs) dose-dependently by both routes of administration in both mouse strains. No distinct difference in route of administration was observed in the test with MS/Ae mice. In CD-1 mice more MNPCEs were induced by the i.p. route than by the p.o. route.

Administration, Oral↗
PubMed1986

Purification and characterization of 3-hydroxy-3-methylglutaryl CoA reductase from potato tubers.

3-Hydroxy-3-methylglutaryl coenzyme A reductase (NADPH) was solubilized by trypsin digestion from sliced potato tuber microsomes, and purified to apparent homogeneity in the absence of detergent with a recovery of 1.8%. The enzyme had a specific activity of 7,910 nmol of mevalonate formed per min per mg of protein. On molecular-sieving high-performance liquid chromatography, the activity was coincident with the single protein peak corresponding to a molecular weight of approximately 110 kDa. On SDS-polyacrylamide gel electrophoresis, the purified enzyme showed only one protein staining band corresponding to a molecular weight of approximately 55 kDa. The apparent Km value for S-HMG-CoA was 6.4 microM and that for NADPH was 25 microM.

Hydroxymethylglutaryl CoA Reductases↗
PubMed1984

Isolation of furanoterpene-containing particles from Ceratocystis fimbriata-infected sweet potato root tissue.

Furanoterpene-containing particles were isolated by centrifugation on a discontinuous Ficoll density gradient from a homogenate of the non-infected tissue adjacent to the infected region of Ceratocystis fimbriata-infected sweet potato root tissue. The particles were recovered at a relatively high ratio in the 2% Ficoll fraction, in which there was no contamination by mitochondria and only little by endoplasmic reticulum judging from the distribution of the activities of their marker enzymes and electron micrographs. Each particle was enveloped in a single membrane, 7-10 nm thick.

Ascomycota↗
PubMed1982

Properties of a Mixed Function Oxygenase Catalyzing Ipomeamarone 15-Hydroxylation in Microsomes from Cut-Injured and Ceratocystis fimbriata-Infected Sweet Potato Root Tissues.

Ipomeamarone 15-hydroxylase activity was found in a microsomal fraction from cut-injured and Ceratocystis fimbriata-infected sweet potato (Ipomoea batatas Lam. cv. Norin No. 1) root tissues and its optimum pH was 8.0. The enzyme reaction required O(2) and NADPH. The K(m) values calculated for ipomeamarone and NADH were approximately 60 and 2 micromolar, respectively. NADPH alone had little effect on enzyme activity but activated the reaction in the presence of low concentrations of NADPH. Ipomeamarone 15-hydroxylase activity was strongly inhibited by p-chloromercuribenzoic acid and markedly suppressed by cytochrome c and p-benzoquinone. KCN was an activator rather than an inhibitor for the reaction. CO inhibited the activity strongly and its inhibition was partially reversed by light. CO difference spectra of the reduced microsomal fraction showed two absorption maxima at 423 and 453 nm; the latter maximum may be due to a cytochrome P-450. These results suggest that ipomeamarone 15-hydroxylase is a cytochrome P-450-dependent, mixed-function oxygenase.Ipomeamarone 15-hydroxylase activity was not found in fresh tissue of sweet potato roots. However, the activity appeared and increased markedly in response to cut-injury or infection by Ceratocystis fimbriata, and reached a maximum after 24 to 36 hours of incubation. The increase in activity in the latter case was 3- to 5-fold higher than in the former. The time course patterns of development and successive decline in ipomeamarone hydroxylase activities were similar to those for cinnamic acid 4-hydroxylase activity, which had been described as a cytochrome P-450-dependent, mixed-function oxygenase. However, little substrate competition was found between ipomeamarone 15-hydroxylase and cinnamic acid 4-hydroxylase in our preparations.

Journal Article↗
PubMed1981

Subcellular Localization of 2-(beta-d-Glucosyloxy)-Cinnamic Acids and the Related beta-glucosidase in Leaves of Melilotus alba Desr.

The distribution of the glucosides of trans- and cis-2-hydroxy cinnamic acid and of the beta-glucosidase which hydrolyzes the latter glucoside was examined in preparations of epidermal and mesophyll tissue obtained from leaves of sweet clover (Melilotus alba Desr.). The concentrations of glucosides in the two tissues were about equal when compared on the basis of fresh or dry weight. Inasmuch as the epidermal layers account for no more than 10% of the leaf volume, the mesophyll tissue contains 90% or more of the glucosides. Vacuoles isolated from mesophyll protoplasts contained all of the glucosides present initially in the protoplasts.The specific activities of the beta-glucosidase in the two tissues were also similar; thus, most of the enzyme is contained in mesophyll tissue. However, the amount of enzyme in mesophyll protoplast extracts amounts to only 1 to 2% of the activity present in leaf homogenates when chlorophyll was the basis for comparison. (This small amount of coumarin-beta-glucosidase present in protoplasts is not associated with chlorophyll-containing fractions.) In contrast, 90% of the uridine diphosphate glucose-o-coumaric acid glucosyl transferase activity present in leaf homogenate was recoverable in protoplasts prepared from intact leaves. Such results indicate that most of the coumarin-beta-glucosidase in M. alba leaves is located in the extracytoplasmic space. Only a small fraction (7%) of this extra cytoplasmic beta-glucosidase was associated with individual cells or cell clusters isolated from clover leaves.

Journal Article↗
PubMed1980

Post-traumatic aortic rupture of the thoracoabdominal junction: a case report.

Twenty-five years after a blunt chest trauma, sudden expansion of a traumatic aortic aneurysm induced a dysphagia and chest pain in a 57-year-old man. Resection of the aneurysm and patch repair of the rupture site utilizing a thoracoabdominal temporary bypass was successful. The location of aortic laceration at the thoracoabdominal junction was most unusual as compared with traumatic aneurysms usually seen in the thoracic aorta.

Aorta, Abdominal↗
PubMed1980

Effects of vitamin A deficiency on thyroid function and serum thyroxine levels in the rat.

The effects of vitamin A deficiency, which results in a substantial decrease in the level of serum retinol binding protein, on the existent state of serum thyroxine and thyroid function were examined. In the vitamin A-deficient rats, the thyroid weight increased and the level of serum thyroxine decreased to one half that of the control rats. Normal thyroid weight and serum thyroxine levels were recovered by the replenishment of retinyl palmitate in the vitamin A-deficient rats. In addition, decreased hormone synthesis was observed in the thyroid glands of the vitamin A-deficient rats. The determination of thyroxine distribution in rat serum proteins in vivo showed that thyroxine-binding prealbumin (TBPA) is a major thyroxine transport protein in the control rats, whereas in the deficient rats the amount of thyroxine bound to TBPA decreased and the thyroxine bound to thyroxine-binding globulin (TBG) increased significantly as compared with observations in control rats. These findings suggest that the existent state of serum thyroxine and thyroid function is affected by the serum level of vitamin A.

Amino Acids↗