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排序方式: 共有1083条查询结果,搜索用时 15 毫秒
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Gza dm Ferenc Jo Pter Temesvri Ern Dux Pter Szerdahelyi 《Neurochemistry international》1987,10(4):529-532
Kinetic parameters of the albumin transport were measured during and after an acute hypoxic insult evoked in newborn piglets by experimental bilateral pneumothorax. Adenylate cyclase activity was determined in the cerebral microvessels isolated by ultracentrifugation from different stages of brain damage. A decrease of the adenylate cyclase activity was observed in the cerebral microvessels of animals with acute hypoxic condition. However, the adenylate cyclase activity was found to be increased significantly in the microvessels during recirculation.
The activation of adenylate cyclase in the microvessel wall may be of pathogenetic importance in the development of vasogenic brain oedema. 相似文献
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The effects of palmitoyl-lysophosphatidylcholine (LPC) were studied on the cellular electrical activity of rabbit heart preparations. LPC (100 mumol/l) caused a considerable enhancement of the automaticity of the SA nodal and Purkinje fibers and frequently induced irregular firing in both supraventricular (SA node, atrium, AV junction) and ventricular (Purkinje fibers, papillary muscle) myocardial regions. The 'automatotropic' and arrhythmogenic effects of LPC were accompanied by a lengthening of the atrioventricular conduction time. In ventricular muscle fibers LPC (100 mumol/l) decreased the resting potential (RP), the maximum rate of depolarization (Vmax) and the amplitude (APA) and duration (APD) of the action potential, and often evoked action potentials of 'slow response' type. In atrial muscle cells, 100 mumol/l LPC was capable of inducing hyperpolarization, with concomitant increases in RP, Vmax, APA and APD; higher concentrations (300 and 600 mumol/l) of LPC resulted in decreases in RP, Vmax, APA and APD, i.e. phenomena similar to those observed with 100 mumol/l LPC in the ventricular myocardium. The results seem to support the assumption that lysolipids accumulating in the ischaemic myocardium may play a pathogenetic role in the development of both supraventricular and ventricular dysrhythmias accompanying coronary artery occlusion. 相似文献
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Data in the literature suggest that exogenous L-carnitine improves the metabolic function of ischaemic heart cells: it enhances the transport of long-chain fatty acids into the mitochondria, stimulates the slowed beta-oxidation, and moderates the accumulation of amphiphilic acyl esters. A study has therefore been made of the cardiac effects of L-carnitine in dog experiments (n = 8). The left anterior descending coronary artery (LAD) was isolated in anaesthetized, thoracotomized animals in situ. After a control occlusion and equilibration period, the LAD was again ligated at the time of L-carnitine infusion (100 mg/kg iv. during 10 min). The agent diminished the maximal conduction delay and the degree of epicardial ST-segment elevation in the ischaemic myocardial region, and the free fatty acid concentration of the arterial blood, but it did not influence the frequency of ventricular extrasystoles. The anti-ischaemic effect of L-carnitine was manifest only during the infusion, and its discontinuation was immediately followed by an enhanced ST-segment elevation. In the dose applied, the substance did not affect the heart rate, systemic mean arterial pressure, left ventricular end-diastolic pressure (LVEDP), or left ventricular contractility (LV dP/dtmax). In the canine myocardial infarction model employed it was observed that the duration of the anti-ischaemic effect of L-carnitine (100 mg/kg iv.) is very short, and it has no significant antiarrhythmic action. 相似文献
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Gudrun Borchert Sabine Bartel Inge Beyerdörfer Irmgard Küttner Laszlo Szekeres Ernst-Georg Krause 《Molecular and cellular biochemistry》1994,132(1):57-67
Evidence is accumulating that 7-oxo-prostacyclin (7-oxo-PGI2) induces a delayed indirect anti-adrenergic and cytoprotective effect on the myocardium, the mechanism of which is still unclear. To demonstrate that a single application of 7-oxo-PGI2 (50 g/kg i.m.) 48 h prior to starting experiments attenuates the isoprenaline inducible inotropic response and accumulation of cAMP, isolated hearts of pretreated animals were perfused in the Langendorff mode with and without isoprenaline (1 to 100 nM). The late anti-adrenergic effect of the drug was manifested by a significant attenuation in the elevation of cAMP levels as well as in contractile force development. This effect was not due to changes in cAMP generation as there were identical 1-adrenoceptor densities and affinities (as calculated from [3H]-CGP binding studies), Gi and Gs protein patterns (as taken from Western blots) as well as adenylyl cyclase activity measurements in the hearts studied. The anti-adrenergic potency of 7-oxo-PGI2, however, was found to be related to a significant rise in cyclic nucleotide hydrolysis by phosphodiesterase (PDE). Using the fast-performance liquid chromatographic separation for PDE isoforms, a significant increase in the activity of PDE isoforms I and IV (260±28 vs 110±12 pmol cGMP/min x enzyme fraction and 77±11 vs 34±3 pmol cAMP/min x enzyme fraction, respectively) was found in the solubilized fraction of cardiac membranes in comparison to untreated controls; PDE IV activity was also increased in the cytosolic fraction (106±14 vs 65±6 pmol cAMP/min x enzyme fraction). The hypothesis that the delayed anti-adrenergic effect of 7-oxo-PGI2 is initiated by an induction and accelerated synthesis of PDE I and IV in the heart is underlined by the fact that cycloheximide suppresses completely both the rise in PDE activities and the anti-adrenergic effects studied. It is suggested that an inducible predominance of cAMP degradation over its generation may be of relevance in processes related to heart protection. 相似文献
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In vivo definition of the functional origin of replication (ori(+ )) of the promiscuous plasmid pLS1
The nocR gene of Agrobacterium tumefaciens Ti plasmid pTiT37 is the regulatory gene of the nopaline catabolism (noc) operon of pTiT37. We have cloned and sequenced nocR, which encodes a DNA-binding protein. The deduced amino acid sequence is similar to those of members of the LysR family of prokaryotic activator proteins. Gel retardation experiments demonstrated that the NocR protein binds to the nocR promoter in both the presence and absence of nopaline. The increased mobility of the complex and alterations in the DNase I footprints revealed a nopaline-induced conformational change in the NocR-DNA complex. Sequence analysis of the NocR binding site indicated the presence immediately downstream of the –10 sequence of the nocR promoter of a 12 by putative operator overlapping a consensus gyrase recognition sequence and an 18 by long alternating purine-pyrimidine sequence. These results suggest that nopaline-induced alterations in the NocR protein-nocR promoter complex might control gene expression in the noc operon. 相似文献
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István Papp László Dorgai Péter Papp Erzsébet Jónás Ferenc Olasz László Orosz 《Molecular & general genetics : MGG》1993,240(2):258-264
Bacteriophage 16-3 inserts its genome into the chromosome of Rhizobium meliloti strain 41 (Rm41) by site-specific recombination. The DNA regions around the bacterial attachment site (attB) and one of the hybrid attachment sites bordering the integrated prophage (attL) were cloned and their nucleotide sequences determined. We demonstrated that the 51 by region, where the phage and bacterial DNA sequences are identical, is active as a target site for phage integration. Furthermore it overlaps the 3 end of a putative proline tRNA gene. This gene shows 79% similartiy to the corresponding proline tRNA-like genomic target sequence of certain integrative plasmids in Actinomycetes. 相似文献
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