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11.
D de Prost V Ollivier J Hakim 《Comptes rendus des séances de la Société de biologie et de ses filiales》1992,186(3):186-192
When appropriately stimulated, monocytes are able to initiate blood coagulation through the membrane expression of tissue factor. This procoagulant activity is thought to play a role in activating coagulation in response to inflammatory stimuli in vivo. We found that pentoxifylline, a methylxanthine derivative already reported to regulate some monocyte functions, inhibits the procoagulant activity developed by monocytes in vitro in response to endotoxin. This effect was accompanied by an early increase in intracellular levels of cyclic AMP and was mimicked by compounds that induce an increase in cyclic AMP levels. These results suggest that the suppressive effect of pentoxifylline occurs at least in part via an increase in intracellular cyclic AMP levels. 相似文献
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M Torres C Auclair J Hakim 《Biochemical and biophysical research communications》1979,88(3):1003-1009
The granule rich-fraction isolated from human resting polymorphonuclear leukocytes is capable of CN-insensitive NADH oxidation and O2-uptake, accompanied by production of superoxide anion, hydroxyl radicals and H2O2. We showed that H2O2 initiates and maintains NADH oxidation and O2-uptake but is also necessary for the formation of superoxide anion and hydroxyl radicals. It acts as a primary substrate for CN-insensitive protein-mediated formation of hydroxyl radicals, which in turn produce superoxide anions, probably through univalent oxidation of NADH as an intermediary. 相似文献
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Hemodynamic responses of dog lung lobe to lobar venous occlusion 总被引:1,自引:0,他引:1
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Various factor affecting NADPH-oxidation by resting human leucocyte granules (LG) at acid pH, have been investigated. It was found that: 1) oxidation of NADPH by LG was increasingly inhibited by increased cyanide concentrations in the medium and was abolished by 4 mM cyanide. 2) with or without cyanide in the incubation medium, LG omitted, Mn++ in the presence of NADPH induced superoxide anion (O- WITH 2) production, as evidenced by oxygen consumption and H2O2 production, which were abolished (in the absence of cyanide) by cytochrome C (a potent O- with 2 scavenger). 3) Both NADPH oxidation in the presence of 2 mM cyanide (cyanide-resistant) and in its absence (cyanide-sensitive) by LG occurred only in the presence of Mn++, and both were inhibited by superoxide dismutase. 4) Cyanide-resistant NADPH oxidation by LG generated H2O2, was inhibited by H2O2 and was not modified by "active" catalase. The ratio of cyanide-resistant NADPH oxidation/O2 uptake was 1 up to 1.25 mM NADPH, and increased above this concentration. 5) Cyanide-sensitive NADPH oxidation was inhibited by catalase and increased upon addition of H2O2. The ratio of cyanide-sensitive NADPH oxidation/O2 uptake was 2. It was concluded that after initiation by O - with 2, produced independently of LG, two sequential types of LG dependent NADPH oxidations occur. First, an O - with 2-dependent protein mediated NADPH oxidation (cyanide-resistant) which generates H2O2 and O - with 2 occurs. Second, NADPH peroxidation (cyanide-sensitive) which utilizes H2O2 takes place. 相似文献
18.
Emond S André I Jaziri K Potocki-Véronèse G Mondon P Bouayadi K Kharrat H Monsan P Remaud-Simeon M 《Protein science : a publication of the Protein Society》2008,17(6):967-976
Amylosucrase is a transglucosidase that catalyzes amylose-like polymer synthesis from sucrose substrate. About 60,000 amylosucrase variants from two libraries generated by the MutaGen random mutagenesis method were submitted to an in vivo selection procedure leading to the isolation of more than 7000 active variants. These clones were then screened for increased thermostability using an automated screening process. This experiment yielded three improved variants (two double mutants and one single mutant) showing 3.5- to 10-fold increased half-lives at 50 degrees C compared to the wild-type enzyme. Structural analysis revealed that the main differences between wild-type amylosucrase and the most improved variant (R20C/A451T) might reside in the reorganization of salt bridges involving the surface residue R20 and the introduction of a hydrogen-bonding interaction between T451 of the B' domain and D488 of flexible loop 8. This double mutant is the most thermostable amylosucrase known to date and the only one usable at 50 degrees C. At this temperature, amylose synthesis by this variant using high sucrose concentration (600 mM) led to the production of amylose chains twice as long as those obtained by the wild-type enzyme at 30 degrees C. 相似文献
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Attenuation of pulmonary and systemic vasoconstriction with pentoxifylline and aminophylline 总被引:1,自引:0,他引:1
The effects of acute administration of therapeutic doses (1-10 mg/kg) of pentoxifylline and aminophylline on the resistance of the systemic and pulmonary circuits in anaesthetized dogs and pigs were tested. During room air breathing, neither of the two substances caused a significant change in systemic vascular resistance (SVR) or pulmonary vascular resistance (PVR). During hypoxia (10% O2 and nitrogen), however, both substances caused a significant reduction in PVR (p less than 0.05) without affecting SVR. The largest dose of pentoxifylline decreased PVR from 7.8 +/- 2.8 to 4.4 +/- 1.5 in dogs and from 9.9 +/- 1.4 to 5.8 +/- 0.6 mmHg.L-1.min in pigs. Aminophylline was equally effective and selective in lowering PVR but not SVR during hypoxia. When SVR was elevated in dogs by continuous infusion of angiotensin, pentoxifylline lowered SVR from 139 +/- 27 to 83 +/- 20 mmHg.L-1.min (p less than 0.05). The simultaneous small elevation in PVR during angiotensin infusion was also attenuated to base-line value by pentoxifylline injection. These results suggest that xanthines, in therapeutic doses, can have a profound vasodilator effect on either the systemic or on the pulmonary circuit, only wherever the vessels are constricted. The vasodilatory effect of pentoxifylline is viewed as a second beneficial effect besides the benefit derived from its action on erythrocyte deformability. 相似文献
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