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Biomedical subjects

K Hosaka

Publications and source records attributed to K Hosaka.

123 records · Page 7Linked to original sources
PubMed1980

Choline transport in Saccharomyces cerevisiae.

Choline transport of Saccharomyces cerevisiae was measured by the filtration method with the use of glass microfiber paper. The uptake was time and temperature dependent. The kinetics of choline transport showed Michaelis behavior; an appearent Km for choline was 0.56 microM. N-Methylethanolamine, N,N-dimethylethanolamine, and beta-methylcholine were competitive inhibitors of choline transport, with Ki values of 40.1, 3.1, and 6.9 microM, respectively. Ethanolamine, phosphorylcholine, and various amino acids examined had no effect. Choline transport required metabolic energy; removal of glucose resulted in a great loss of transport activity, and the remaining activity was abolished by 2,4-dinitrophenol, carbonyl cyanide p-trifluoromethoxyphenyl hydrazone, arsenate, and cyanide. External Na+ was not required, and the transport was not effected by ionophores, valinomycin, and gramicidin D. These results indicate that S. cerevisiae possess an active choline transport system mediated by a specific carrier. This view is further supported by the isolation and characterization of a choline transport mutant. The choline transport activity in this mutant was very low, whereas the transport of L-leucine, L-methionine, D-glucose, and myo-inositol was normal. Together with the choline transport mutant, mutants defective in choline kinase were also isolated.

Biological Transport, Active↗
PubMed1979

Acyl-coenzyme-A synthetase I from Candida lipolytica. Purification, properties and immunochemical studies.

Acyl-coenzyme-A synthetase I from Candida lipolytica has been purified to homogeneity as evidenced by polyacrylamide gel electrophoresis in the presence and absence of dodecylsulfate as well as by Ouchterlony double-diffusion analysis. The purification procedure involves resolution of cellular particles with Triton X-100 and chromatography on phosphocellulose, Blue-Sepharose and Sephadex G-100. The purified enzyme exhibits a specific activity of 20--24 U/mg protein at 25 degree C, which is about 100-fold higher than those of long-chain acyl-CoA synthetases hitherto reported. The molecular weight of the enzyme has been estimated by polyacrylamide gel electrophoresis in the presence of dodecylsulfate to be approximately 84 000. The enzyme is specific for fatty acids with 14--18 carbon atoms regardless of the degree of unsaturation. Studies with the use of specific antibody to acyl-CoA synthetase I have indicated that this enzyme is immunochemically distinguishable from acyl-CoA synthetase II.

Candida↗
PubMed1977

Diacylglycerol acyltransferase from rat liver microsomes. Separation and acyl-donor specificity.

1. Diacylglycerol acyltransferase was resolved from rat liver microsomes and separated from glycerolphosphate acyltransferase and 1-acylglycerolphosphate acyltransferase. The separation was achieved by sucrose-density-gradient centrifugation of the enzyme preparation which was obtained by molecular-sieve chromatography of microsomes solubilized with a nonionic detergent, Triton X-100. 2. Although diacylglycerol acyltransferase and 1-acylglycerolphosphorylcholine acyltransferase were not separated from each other, the two acyltransferases were distinguishable with respect to heat stability and sensitivity to sulfhydryl-binding reagents. 3. Studies with the diacylglycerol acyltransferase preparation obtained have shown that this enzyme possesses a broad acyl-donor specificity, utilizing saturated, monoenoic, dienoic and tetraenoic fatty acyl-CoA thioesters efficiently. 4. A simplified assay method for diacylglycerol acyltransferase is described.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1975

Partial purification, properties, and subcellulsr distribution of rat liver phosphatidate phosphatase.

Phosphatidate phosphatase (EC 3.1.3.4Y was purified 15- to 20-fold from the soluble fraction of rat liver. The purification procedure involved calcium phosphate gel adsorption and elution, ammonium sulfact precipitation, and molecular-sieve chromatography. For the enzyme assay, and aqueous dispersion of phosphatidate, rather than "membrane-bound" phosphatidate, was used as substrate. The partially purified enzyme depends almost entirely on the presence of Mg2+ for its activity. Morover, the activity of the enzyme is stimulated by phosphatidylcholine. The enzyme exhibits a high substrate specificity for phosphatidate. The apparent Km for phosphatidate is approximately 0.05 mM. The optimum pH is between 7.4 and 7.6. The enzyme is inhibited by fluoride and by p-chloromercuribenzoate. The subcellular distribution of phosphatidate phosphatase in rat liver was studied by assaying the activity of the enzyme in the presence of Mg2+ and phosphatidylcholine. In contrast ot the results of previous studies, most of the enzyme activity was found in the soluble fraction.

Adsorption↗
PubMed1972

Resolution and reconstitution of the phosphatidate-synthesizing system of rat-liver microsomes.

The phosphatidate-synthesizing system of rat-liver microsomes was resolved into two component enzymes, glycerolphosphate acyltransferase and 1-acylglycerolphosphate acyltransferase. The resolution is effected by sucrose density gradient centrifugation in the presence of a nonionic detergent, Triton X-100. Combination of both enzymes results in reconstitution of the phosphatidate-synthesizing system. These results establish that two distinct enzymes, glycerolphosphate acyltransferase and 1-acylglycerolphosphate acyltransferase, are required for synthesis of phosphatidic acid from sn-glycerol 3-phosphate.Furthermore, the 1-acylglycerolphosphate acyltransferase preparation efficiently uses unsaturated (or saturated) fatty acyl-CoA as acyl donor. Our previous studies showed that the glycerolphosphate acyltransferase preparation catalyzes formation of 1-acylglycerol 3-phosphate, using preferentially saturated fatty acyl-CoA as acyl donor. These findings indicate that the reconstituted system is capable of yielding phosphatidic acid with an asymmetric fatty acid distribution.

Acetyltransferases↗
PubMedDate not supplied

Hypoxemia due to inserting a bite block in severely handicapped patients.

In severely handicapped patients with severe cerebral palsy, stridor can be caused by a bite block in the mouth. So that dental treatment can be performed safely for these patients, the effect of a bite block on the respiratory function of 30 severely handicapped patients was investigated with two pulse oximeters. Of the 30 subjects examined, 96.7% showed SpO2 values above 95% in the resting state, and 26.7% showed SpO2 values under 94% after insertion of a small or middle-sized bite block. Patients who did not show SpO2 decrease while using a small bite block did have deterioration of SpO2 values when a middle-sized bite block was used. According to analysis by AIC, patients whose weight was less tha 20 kg, who were shorter than 130 cm, and who were more severely handicapped tended to have a deterioration of breathing function when using a bite block

Adolescent↗
PubMedDate not supplied

Effects of 2,3-dibenzylbutane-1,4-diol on vascular smooth muscle of rabbit aorta.

We investigated the effects of 2,3-dibenzylbutane-1,4-diol (DBB), a mammalian lignan derived from human urine, on the contractile response and the 45Ca2+ uptake in the vascular smooth muscle of rabbit aorta. In resting state, DBB did not influence the tension and the 45Ca2+ uptake. DBB inhibited the high KCl- and the CaCl2-induced contraction in the partially depolarized muscle strip. DBB inhibited the noradrenaline- and the angiotensin II-induced contraction, but not the transient contraction evoked by noradrenaline in Ca2+-free solution. DBB completely inhibited the 45Ca2+ uptake induced by high KCl or noradrenaline. These results indicate that DBB inhibits the Ca2+ influx but not the Ca2+ release from the Ca2+ stores.

Angiotensin II↗