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Biomedical subjects

K Shibata

Publications and source records attributed to K Shibata.

At least 793 records · Page 44Linked to original sources
PubMed1977

Development of myogenic sarcomas in mice at the site of injection of 4-HAQO -- a study on the morphogenesis of tumor.

The morphological changes induced by a carcinogenic agent have been studied by serial histological examinations on the injection-sites in subcutaneous tissue of mice. As a carcinogen, 4-hydroxy-aminoquinoline-1-oxide was freshly suspended before use in olive oil (0.1 mg/0.1 ml) and injected subcutaneously into the right thigh of mice sixteen times at seven days intervals. Tumors were induced immediately after the sixteenth injection. Based on light and electron microscopic findings, these tumors were considered to be rhabdomyosarcomas. Morphologically, the course of the tumor induction was summarized as follows. The stage of inflammation (1-4 weeks), the stage of necrosis (4-8 weeks), the stage of the appearance of atypical cells (8-15 weeks), and the stage of tumor development (16 weeks and thereafter).

4-Hydroxyaminoquinoline-1-oxide↗
PubMed1977

[Influence of hexobendine, prenylamine and verapamil on the contractile response of isolated rabbit left atria and aortae to calcium (author's transl)].

In isolated rabbit left atria driven electrically at a frequency of 30/min, the contraction was abolished by increasing external K+ concentrations from 5.4 to 22mM. Addition of isoproterenol (10(-6)M) restored the atrial contraction and the magnitude of contractions increased by raising external concentrations of Ca++ to 4.4 and 6.6. mM. Hexobendine attenuated the magnitude of contractions restored by isoproterenol and excess Ca++ in a dose-dependent manner, as did prenylamine and verapamil. Hexobendine did not significantly influence the membrane depolarization induced by excess K+ and there was no evidence of a beta-adrenergic blocking action. In helical strips of rabbit aortae exposed to Ca++-free media and depolarized by excess K+, the addition of Ca++ caused a marked contraction. Hexobendine, prenylamine and verapamil caused a dose-related attenuation of the Ca++-induced contraction. Relative potencies of the inhibition by hexobendine, prenylamine and verapamil were 1:16.5:100. Inhibitory effects of these drugs were partially antagonized by excess Ca++. Greater attenuation of the contractile response to 25 mM K+ than the response to 2 X 10(-6)M noradrenaline was observed in preparations treated with hexobendine. It may be concluded that interference with the influx of Ca++ across cell membrane in atrial muscles and aortic smooth muscles participates in the inhibition of contractility by hexobendine.

Animals↗
PubMed1976

Light-dependent development of thermoluminescence, delayed emission and fluorescence variation in dark-grown spruce leaves.

Thermoluminescence profiles of spruce leaves grown under various light or dark conditions were measured after excitation at a low temperature (-70 to -20 degrees C) by 1-min illumination with red light, and the following results were obtained. Mature spruce leaves showed five thermoluminescence bands at -30, -5, +20, +40 (or +35) and +70 degrees C (denoted as Zv, A, B1, B2 and C bands, respectively), but dark-grown spruce leaves with a similar chlorophyll content showed only two bands, at -30 and +70 degrees C (the Zv and C bands) and were devoid of the three other bands (the A, B1, and B2 bands). On exposure of the dark-grown leaves to continuous red light, the A, B1and B2 bands were rapidly developed, and the development was accompanied by enhancement of delayed emission, fluorescence variation and the Hill activity (photoreduction of 2,6-dichlorophenolindophenol with water as electron donor). It was demonstrated that the dark-grown spruce leaves are devoid of the water-splitting system in Photosystem II, and that the latent water-splitting activity is rapidly photoactivated by exposure of the leaves to continuous red light. These results on the gymnosperm spruce leaves, in which greening proceeds in complete darkness, being independent of the development of the water-splitting system in light, were discussed in relation to previous observations on angiosperm leaves, in which both greening and the activity generation proceed in the light.

Chlorophyll↗
PubMed1976

Light-dependent inhibitory action of p-nitrothiophenol on photosystem II in relation to the redox state of electron carriers.

The photosystem-II activity of chloroplasts was inhibited by the treatment with p-nitrothiophenol (NphSH) in the light, and the inhibition was accompanied by a change of the fluorescence spectrum. Aromatic mercaptans examined were active in causing this inhibition and fluorescence change. These effects of p-nitrothiophenol were highly accelerated by blocking the electron transport of the oxidation side of photosystem II by carbonyl-cyanide-m-chlorophenylhydrazone (CCCP) or Tris-HC1 or heat pre-treatment, whereas these were suppressed by blocking the transport on the reduction side by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). It was deduced that the site of NphSH action in the electron transport chain is closer to the reaction center of photosystem II that the blocking site of CCCP or Tris-HC1 or heat, and that such a site in photosystem II is exposed to be modified with NphSH when electron carriers on the oxidation side of photosystem II are oxidized by illumination.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗
PubMed1976

Multiple-flash development of thermoluminescence bands in dark-grown spruce leaves.

Spruce leaves greened in darkness were devoid of three of the five thermoluminescence bands found for mature leaves. These bands were developed rapidly by exposure of the dark-grown leaves to continuous light. The development of these bands was studied by illumination with repetitive flashes at varied intervals. Flashes at intervals of 1 s were the most effective in inducing these bands. Those at shorter or longer intervals were less effective. It was deduced from these data that the development of these bands is a multiquantum process which involves at least two photo-events with a dark reaction between them.

Chloroplasts↗