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991.
Summary Phospholipase A2 (PLA2) produced slow dose dependent relaxation in intact and endothelium-deprived precontracted rabbit aortic strips. In endothelium-deprived preparations, relaxation induced by PLA2 is inhibited by hemoglobin, methylene blue and parabromophenacylbromide (PBPB), and is potentiated by superoxide dismutase (SOD). Indomethacin has no effect. Relaxation is accompanied by a rise in c-GMP. Phospholipase C causes a significant increase in tension, while Phospholipase D has no effects. In intact aortic strips PLA2 causes a biphasic response with no elevation in c-GMP. The results indicate several common features of the PLA2 released factor with endothelium-derived relaxing factor (EDRF). However PLA2 induced relaxation is not dependent on endothelial cells. Apparently in addition to nitric oxide which may be the endothelium-derived relaxing factor, a second smooth muscle relaxing factor exists which is initiated by PLA2 and is independent of endothelium. The production of the PLA2 produced relaxation is dependent on its specific hydrolytic activity. We call this relaxing factor the phospholipid-derived relaxing factor (PDRF). 相似文献
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Summary Zinc adsorption isotherms were constructed for three calcereous soils which varied in carbonate contents, texture, and past history of phosphate fertilization. The equilibrium conditions were 25°C, 0.01 M CaCl2 and 6 days.Higher phosphate fertilization of the soils reduced Zn adsorption. The effect of P was more in the soil with lower carbonate content which suggested that soil carbonates played a dominant role in the Zn adsorption characteristics of the soils.The adsorption data conformed to the Langmuir equation. Constants (k and b) calculated from the Langmuir isotherm showed that bonding energies (k) were inversely related to extractable P; i.e. higher Zn adsorption was associated with lower bonding energy. The Zn adsorption maxima (b) were higher for the soils with higher calcium carbonate equivalent.Adsorbed Zn was extracted with a single extraction of 0.005 M DTPA. The recovery was 91 percent for the Tandojam soil, 82 percent for the Tarnab soil, and 63 percent for the Kala shah Kaku soil, indicating that most of the adsorbed Zn is not irreversibly fixed by the soils and can be utilized by plant during growth.The results suggest that P-induced Zn deficiency could not be ascribed to precipitation of Zn as insoluble Zn-P compounds in soils. The increased Zn solubility with P fertilization is the evidence that P-Zn interaction does not reside in the growing medium external to plant.The work is part of Ph.D. thesis submitted to the University of Hawaii, Honolulu, U.S.A. 相似文献
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The inhibition of prostaglandin (PG) synthetase by nonsteroidal anti-inflammatory drugs (NSAID) is not well understood. Co-factors (glutathione and hydroquinone) are needed for maximum enzymatic activity in vitro, and we suggest that NSAID might inhibit PG synthetase partly by interfering with co-factor induced stimulation of the enzyme. This hypothesis was tested by: A) Examining the effect of glutathione, noradrenaline and hydroquinone on bull seminal vesicle (BSV) PG synthetase in vitro. The stimulatory effects were concentration-dependent. B) Three structurally distinct NSAID, indomethacin, aspirin and paracetamol, inhibited the stimulation by each co-factor in a concentration-related manner. Drug effectiveness also depended on the concentration of co-factor. 相似文献
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Jafari Samira Hossein Arani Asghar Mosleh Esfahani Saeed Tarkesh 《Journal of Plant Growth Regulation》2023,42(3):1472-1487
Journal of Plant Growth Regulation - Origanum vulgare L. is a valuable flavoring, mainly due to its important essential oils and is widely used in different industries. This study aimed to compare... 相似文献
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Arif Lodhi M Iqbal Choudhary M Malik A Ahmad S 《Journal of enzyme inhibition and medicinal chemistry》2008,23(3):400-405
The lignans (1-8) isolated from the roots of Vitex negundo Linn. were screened against the serine proteases alpha-chymotrypsin, thrombin and prolyl endopeptidase. Compounds 3 and 4 were found to be active only against alpha-chymotrypsin and were noncompetitive and competitive inhibitors of the enzyme, respectively. Ki values were found to be in the range 31.75-47.11 microM. 相似文献