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Biomedical subjects

S Hama

Publications and source records attributed to S Hama.

At least 55 records · Page 3Linked to original sources
PubMed1991

Inhibition of mitochondrial respiratory chain by alkylthiolated 2,3-dicyano-1,4-benzoquinones.

A series of alkylthiolated 2,3-dicyano-1,4-benzoquinones was synthesized and tested for the effects on the respiratory chain in beef heart mitochondria as an antimetabolite of ubiquinones (coenzyme Q). It was proved that these analogs are among the best inhibitors of both succinate oxidase and NADH oxidase systems. The introduction of a 2,3-dicyano group to the quinone ring was found to be more favorable for inhibitory activity than 2,3-dimethoxy, 2,3-dimethyl groups and bicyclic quinones such as 2,3-ethylenedioxy-1,4-benzoquinones and 1,4-naphthoquinones. The inhibitory activity was minimally sensitive to the length of the alkylthio side-chain. On the other hand, the difference spectra of reduced minus oxidized forms of cytochromes were investigated to identify the inhibitory site, suggesting that alkylthiolated 2,3-dicyano-1,4-benzoquinones inhibit at sites between the substrates (succinate and NADH) and cytochrome b, and at the site after cytochrome a + a3 in the respiratory chain.

Animals↗
PubMed1990

Inhibition of mitochondrial respiratory chain by arylthiolated 2,3-ethylenedioxy-1,4-benzoquinones.

A series of arylthiolated 2,3-ethylenedioxy-1,4-benzoquinones as a coenzyme Q (CoQ) antagonist was tested for inhibition of succinate oxidase and reduced nicotinamide adenine dinucleotide (NADH) oxidase systems in the mitochondrial respiratory chain. The following characteristics were revealed: (1) 2,3-ethylenedioxy, 5-arylthio and 5,6-diarylthio groups were confirmed to be favorable for inhibition of both systems; (2) these analogs were more effective in the succinate oxidase system than in the NADH oxidase system; (3) 4' substituents on the benzene side ring had little effect on inhibitory activity; (4) the acting sites of these analogs had no strict stereospecificity. The reduced minus oxidized difference spectra revealed that these analogs inhibited the succinate oxidase system at the site between succinate and CoQ, and the NADH oxidase system at the site after cytochrome a + a3, suggesting these analogs might act as antagonists of CoQ in the succinate oxidase system. However, 5-(4'-nitrophenylthio)-2,3-ethylenedioxy-1,4-benzoquinone (If) strongly inhibited only the succinate oxidase system at the site after cytochrome a + a3.

Animals↗
PubMed1989

[A shortened method for the assay with Centocor radioimmunoassay kit].

We have conducted a series of basic studies about Centocor's CA125 RIA Kit, especially for the conditions of the incubation. The standard curve and the outcome of recovery test gained through the standard method and the shortened method are quite decent. As for the incubation time, it took longer than 20 hours and 6-18 hours inthe standard method and shortened one respectively. As our conclusion, these results suggest that the shortened method can be adopted as a practical one as well as the standard method, provided that careful attention is paid to several peripheral conditions in the assay.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1988

An improved method for the detection of HIV antigen in the blood of carriers.

The measurement of HIV antigen levels in sera or plasma of HIV-infected individuals is critical for determining the existence of antigen or infectious virus before seroconversion and for prognosis. Pretreatment of sera or plasma of HIV carriers by heating at 70 degrees C for 10 min at an acidic pH enabled us to estimate antigens efficiently in immune complexes. This procedure will also be useful in determining antigen levels in HIV carriers more precisely.

Acquired Immunodeficiency Syndrome↗