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Biomedical subjects

M Isobe

Publications and source records attributed to M Isobe.

At least 361 records · Page 20Linked to original sources
PubMed1980

Studies on metabolism and toxicity of styrene: III. The effect of metabolic inactivation by rat-liver S9 on the mutagenicity of phenyloxirane toward Salmonella typhimurium.

A comparative study on enzymic factors influencing the metabolic inactivation of phenyloxirane (styrene oxide), a major mutagenic metabolite of styrene in the liver, was carried out with respect to soluble glutathione S-transferase and microsomal epoxide hydratase in the 9000 X g supernatant fraction (S9) from a rat-liver homogenate. The mutagenic activity of phenyloxirane to Salmonella typhimurium TA100 was markedly reduced by S9 in the presence of glutathione but to a smaller extent in its absence. The retarding effect of glutathione on the inherent mutagenic activity of phenyloxirane was exerted by the soluble supernatant of S9 but not by microsomes. A gas-liquid chromatographic study indicated that the effect of glutathione was attributable to the disappearance of the mutagen from the microbial assay system. The rate of the disappearance was 10-20 times as fast in the soluble supernatant fraction as in the microsomes when fortified with more than 4 mM glutathione. Our results strongly suggest that in hepatic cells of the rat, cytosol glutathione S-transferase plays a much more important role than microsomal epoxide hydratase in the detoxication of the metabolite, phenyloxirane.

Animals↗
PubMed1980

Cholesterol diet increases plasma and liver concentrations of cholesterol epoxides and cholestanetriol.

Cholesterol alpha-epoxide (5, 6 alpha-epoxy-5-alpha-cholestan-3 beta-ol), cholesterol beta-epoxide (5, 6 beta-epoxy-5 beta-cholestan-3 beta-ol), and cholestanetriol (5 alpha-cholestane-3 beta, 5, 6 beta-triol) were isolated from plasma and liver of rabbits by high performance liquid chromatography and identified by gas-chromatography-mass spectrometry. The 5, 6-oxygenated cholestanols in the plasma and liver of rabbits fed for two months on a diet supplemented with cholesterol wee elevated to 2-5 times and 5-8 times for normal level, respectively. Among the 5, 6-oxy-generated steroids, the beta-epoxide existed at the highest level in tissues of both control and cholesterol-fed rabbits. The ratios of the beta-epoxide to the alpha-epoxide were 2-3 in all the examined biological specimens just as the previously demonstrated ones in the vitro lipid peroxidation-mediated reaction of cholesterol. These results strongly suggest that the epoxidation of the cholesterol double bond in the animal may be mediated by lipid peroxidation. The elevated 5, 6-oxygenated cholestanol levels on long term cholesterol feeding will be discussed in relation to a possible physiological role of cholestanetriol in regulation of tissue cholesterol levels.

Animals↗
PubMed1977

Kallikrein inhibitors in rat plasma.

The kallikrein inhibitor contents of human and animal plasma were determined with glandular kallikreins [EC 3.4.21.8]. One ml of plasma could inactivate 20-700 kallikrein units (KU). Rat plasma was the most potent and inactivated 230-700 KU. However, no enzyme capable of inactivating kallikrein could be found in this plasma. Two fractions which inhibited hog pancreatic kallikrein, a fraction corresponding to alpha2-macroglobulin and a fraction which was eluted prior to albumin, were separated from rat plasma by Sephadex G-200 gel filtration. The former inhibitor could inhibit hog pancreatic kallikrein action on Nalpha-benzoyl-L-arginine ethyl ester (BAEE) as well as in the dog vasodilator assay. The other inhibitor was partially purified from rat plasma. One mg of the preparation inhibited 67 KU and the hydrolysis of 5.8 micronmoles/min of BAEE by hog pancreatic kallikrein [EC 3.4.21.8]. The inhibitor also inhibited other glandular and plasma kallikreins, trypsin [EC 3.4.21.4], alpha-chymotrypsin [EC 3.4.21.1], etc. The optimal pH of the inhibitor was 7.5-8. The inhibitor was unstable below pH 5, and was destroyed by heating at temperature above 60 degrees. The isoelectric point of the inhibitor was determined by Ampholine focusing to be 4.4, and its molecular weight was estimated to be 73,000 by Sephadex G-100 and G-150 filtrations. Several experimental results suggested that this inhibitor differed from alpha1-antitrypsin.

Animals↗
PubMed1976

High performance preparative column chromatography of lipids using a new porous silica, Iatrobeads. I. Separation of molecular species of sphingoglycolipids.

Good preparative separation of neutral glycolipids of human erythrocytes was achieved by column chromatography using the totally porous silica spheres, Iatrobeads. The solvent flow through the Iatrobeads column was rapid under atmospheric pressure, and so elution bands migrated with minimal diffusion in the column. Ceramide dihexoside and ceramide trihexoside were both separated into two fractions of different molecular species on the Iatrobeads column. Two ceramide tetrasaccharides, globoside I and paragloboside, were also clearly separated on the Iatrobeads column. Chemical analysis showed that separation of these molecular species was due to differences in their fatty acid and long chain base compositions. Sphingadienine and phytosphingosine were found as minor components of long chain bases in human erythrocyte glycolipids.

Erythrocytes↗
PubMed1976

Existence of glucosaminyl lactosyl ceramide (amino CTH-I) in human erythrocyte membranes as a possible precursor of blood group-active glycolipids.

A novel glycolipid containing N-acetylglucosamine (lacto-N-triose II ceramide, Amino CTH-I) was isolated as a minor component from the ceramide trihexoside fraction of human erythrocyte lipids. This glycolipid was purified by column chromatography and preparative high-speed liquid chromatography on Iatrobeads. Its structure was found to be N-acetylglucosaminyl(beta 1-3)galactosyl(beta 1-4)glucosyl-(beta 1-1)ceramide, so it is suggested that it may be a precursor of paragloboside and blood group-active glycolipids.

Amino Acids↗
PubMed1975

Studies on the mechanism of the lipase reaction. II. Comparative studies on the adsorption of lipases and various proteins at the air-water interface.

Adsorption of lipases (EC 3.1.1.3) and various proteins at the air-water interface has been investigated in relation to the mechanism of lipase reaction. Aqueous solutions of lipases and denaturated proteins show surface activity as strong as that of synthetic detergents. However, ths surface activity of esterases and various other proteins is little or none. By foam fractionation it was shown that lipases were adsorbed at the air-water interface and the adsorption followed the equation of Langmuir's adsorption isotherm. The properties of lipase at the interface are discussed in relation to the mechanism of lipase reaction and the differences from the esterase reaction.

Adsorption↗