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T Okayasu

Publications and source records attributed to T Okayasu.

At least 73 records · Page 4Linked to original sources
PubMed1981

[Purification and characterization of Linoleoyl-CoA desaturase from rat liver microsomes (author's transl)].

Rat liver microsomes catalyzed the oxidative delta 6-desaturation of linoleoyl-CoA (C18: 2, delta 9.12.) to gamma-linolenoyl-CoA (c18: 3, delta 6.9.12.) by using molecular oxygen and NADH or NADPH as the electron donors. The antibodies against cytochrome b5 inhibited markedly the delta 6-desaturation in the intact microsomes of the rat liver, suggesting that cytochrome b5 participated in the delta 6-desaturation. These experimental results led us to the hypothesis that the delta 6-desaturation of linoleoyl-CoA followed the scheme. (See formula in text). Terminal "delta 6-desaturase" was purified from rat liver microsomes for the first time by Triton X-100 solubilization, DEAE-cellulose, CM-Sephadex and cytochrome b5-Sepharose chromatography using its high affinity for cytochrome b5. The final enzyme preparation was homogeneous when applied to sodium dodecyl sulfate disc gel electrophoresis. delta 6-desaturase appeared as a single polypeptide of 66,000 daltons containing 49% nonpolar amino acid residues and one atom of non-heme iron. We confirmed that delta 6-desaturase differed from delta 9-desaturase, which converted stearoyl-CoA to oleoyl-CoA. The delta 6-desaturase activity required NADH (or NADPH), linoleoyl-CoA, oxygen, lipid or detergent and three enzymes, such as NADH-cytochrome b5 reductase (or NADPH-cytochrome P -450 reductase), cytochrome b5, and delta 6-desaturase. The reconstituted system of these components also confirmed the electron flow represented in Scheme 1. The delta 6-desaturase activity was inhibited by iron chelators, cyanine and p-chloromercuriphenyl sulfonate. In the reconstituted system of Km value for linoleoyl-CoA was 47 micro M, the maximal velocity was 83nmol/min/mg protein of delta 6-desaturase and the optimal pH was 7.0. Catalase, superoxide dismutase and t-butanol showed supportive effects on the delta 6-desaturation of the reconstituted system when purified enzymes were employed.

Acyl Coenzyme A↗
PubMed1981

Subcellular distribution of alkyl dihydroxyacetone phosphate synthase in rat liver.

Most alkyl dihydroxyacetone phosphate (DHAP) synthase of rat liver was found distributed in the light mitochondrial fraction which was enriched with lysosomes and peroxisomes. Further separation of the lysosomes and peroxisomes in the liver light mitochondrial fraction of the rats injected with Triton WR-1339 was carried out by centrifugation in the sucrose density gradient. After the centrifugation, the enzyme distribution was compared with that of the different marker enzymes which revealed that alkyl-DHAP synthase was primarily localized in the peroxisomes. When the rats were fed a diet supplemented with clofibrate, which is known to induce the proliferation of peroxisomes, the synthase activity of the liver increased about 1.5 to 1.7 times more than that of the control. These results supplied further evidence for the localization of synthase in peroxisomes.

Alkyl and Aryl Transferases↗
PubMed1981

[Augmentation of specific anti-tumor immunity by immunization with xenogenized tumor cells and its application to the experimental cancer treatment (author's transl)].

It is already known that immunization with viable tumor cells which had been artificially infected with Friend virus (xenogenized tumor cells), one of murine leukemia viruses, produced a strong anti-tumor immunity against the identical non-infected tumor in comparison with that with mitomycin C-treated or irradiated non-infected tumor cells. Lethal tumor dose which could kill 50% of rats (LTD50) was increased up to 1,000 times by the immunization with the viable xenogenized tumor cells. In this presentation, procedure how to augment immunogenicity of the xenogenized tumor cells was examined. Intradermal single immunization with the xenogenized tumor cells (third passage generation through Friend virus-tolerant rats) inhibited most strongly the subcutaneous growth of non-xenogenized tumor; LTD50 was markedly increased more than 10,000 times. In addition, the intradermal active immunization with the viable xenogenized tumor cells followed by the irradiated non-xenogenized tumor cells resulted in 30.8% of complete regression of the tumor subcutaneously transplanted.

Animals↗
PubMed1980

Immunological depression in spontaneously hypertensive rats.

Cell-mediated immunity was investigated in spontaneously hypertensive rats (SHR). The thymuses of young SHR rats before developing hypertension had reduced numbers of immature T lymphocytes which were detected by the rosette formation test with guinea-pig erythrocytes in the presence of foetal bovine serum, whereas the thymuses of eight other rat strains tested contained about 60% of rosetting cells. The number of rosetting cells decreased progressively with age. The blastogenic responses to PHA and Con A of the SHR rats' lymphocytes was depressed to less than one-fifth when compared to those of othe rat strains including W/7k rats, the original colony of the SHR rats. Eight-month-old SHR rats showed fewer mitogenic responses than those of 2-month-old SHR rats. Other cell-mediated immune responses, including delayed hypersensitivity, allograft rejections, and a co-operation of T and B lymphocytes to produce humoral antibody formation were depressed significantly when compared to those of other rat strains. Possible mechanisms of immunological depression in the SHR rats in relation to the devleopment of hypertension are discussed.

Aging↗
PubMed1977

Effects of dietary vitamin B-2 and vitamin E on the delta9-desaturase and catalase activities in the rat liver microsomes.

The effects of dietary vitamin B-2 and vitamin E on delta9-desaturation of stearoyl-CoA, catalase, glutathione peroxidase, superoxide dismutase and electron transport components in rat liver microsomes have been investigated. delta9-desaturase activities were decreased on diets deficient of vitamin B-2, E and supplemented with E. Among the peroxide-scavenging enzymes, only the catalase activity in microsomes correlates significantly with delta9-desaturase activity. In vitro addition of bovine catalase had no effect on microsomal delta9-desaturase activity on control diet. However, it enhanced the delta9-desaturation in microsomes on vitamin B-2-deficient diet which contained low catalase and high superoxide dismutase activities, compared to those in microsomes of control diet. It is suggested that the hydrogen peroxide-generating and -decomposing systems may play an important role on the delta9-desaturase activity in microsomes.

Animals↗
PubMed1977

Involvement of cytochrome b5 in the oxidative desaturation of linoleic acid to gamma-linolenic acid in rat liver microsomes.

The effects of antibodies against microsomal electron-transport components on the in vitro activity of delta6-desaturation of linoleic acid to gamma-linolenic acid have been studied in intact microsomal membranes of rat liver. Reduced nicotinamide adenine dinucleotide (NADH) or reduced nicotinamide adenine dinucleotide phosphate (NADPH) (0.87 mM) served as electron donors, and effectively prompted the delta6-desaturase activities with yields of about 1.1 to 1.3 nmol per mg of protein in 10 min. Of the two antibodies studied under the same in vitro conditions, i.e., rabbit antisera preparations against rat liver microsomal hydrophilic parts of cytochrome b5 and NADPH-cytochrome c reductase, only the antibody against cytochrome b5 demonstrated a marked ability to inhibit the delta6-desaturase activity. This evidence supports a participation of cytochrome b5 in the delta6-desaturation of linoleic acid and suggests a pathway analogous to the delta9-desaturation of stearyl-CoA.

Animals↗