1,720,976 research outputs found
Effects of quercetin and rutin on vascular preparations: a comparison between mechanical and electrophysiological phenomena.
No full textBackground: Several studies have indicated that quercetin promotes relaxation of vascular smooth muscle both in vivo and in vitro. However, Saponara et al. [(2002) Br J Pharmacol 135:1819-1827] have demonstrated that quercetin is an activator of vascular L-type Ca2+ channels. Aim of the study: We investigated the mechanical and electrophysiological properties of quercetin and its rutoside, rutin, in an attempt to clarify how Ca2+ channel activation might be related to the myorelaxing activity. Methods: Aorta ring preparations and single tail artery myocytes were employed for functional and patch-clamp experiments, respectively. Results: Rutin was found to relax intact rat aorta rings, which had been precontracted with phenylephrine (pIC50 = 5.65±0.3 1) but in contrast had no effect on depolarised (60 mM K+) preparations or on those from which the endothelium had been removed. Furthermore, rutin did not affect L-type Ca2+ current recorded in rat tail artery myocytes. The quercetin-induced relaxation of intact rings precontracted with phenylephrine exhibited two components characterised by 6.23±0.38 and 4.66±0.09 pIC50, respectively. Removal of the endothelium abolished the first component, leaving the second unaltered. Moreover, quercetin was found to relax 60 mM K+ depolarised rings with a pIC50 of 4.59±0.03. The application of quercetin in isolated smooth muscle cells brought about a marked increase of L-type Ca2+ current (pEC50= 5.09±0.05). Unlike quercetin, Bay K 8644 contracted aorta rings preincubated with 10, 20 or 30 mM K+. The myotonic effect of Bay K 8644 was observed both in the absence or presence of 30 μM quercetin. The application of Bay K 8644 (10-100 nM) caused a further significant increase in L-type Ca2+ current in rat tail artery myocytes stimulated with 30 μM quercetin. Conclusions: Quercetin is a naturally occurring L-type Ca2+ channel agonist. This effect, however, is overwhelmed by quercetin-induced vasorelaxation taking place via pathways which are more relevant than L-type Ca2+ influx in the hierarchy of functional competencies
Freeze-dried red wine effects on cardiac function and ECG of the Langendorff-perfused rat heart
No full textThe effect of freeze-dried red wine (FDRW) on cardiac function and electrocardiogram (ECG) in Langendorff-isolated rat hearts was investigated. FDRW significantly decreased left ventricular pressure and coronary perfusion pressure, the latter being dependent on the activation of both phosphatidylinositol 3-kinase and eNOS. FDRW did not affect the QRS and QT interval in the ECG, although at 56 μg of gallic acid equivalents/mL, it prolonged PQ interval and induced a second-degree atrioventricular block in 3 out of 6 hearts. This is the first study demonstrating that at concentrations resembling a moderate consumption of red wine, FDRW exhibited negative inotropic and coronary vasodilating activity leaving unaltered ECG, whereas at very high concentrations, it induced arrhythmogenic effects
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Calcium antagonist and antiperoxidant properties of some hindered phenols
No full text1. The calcium antagonist and antioxidant activities of certain synthetic and natural phenols, related to BHA (2-t-butyl-4-methoxyphenol), were evaluated in rat ileal longitudinal muscle and in lipid peroxidation models respectively. 2. Compounds with a phenol or a phenol derivative moiety, with the exception of 2,2'-dihydroxy-3,-3'-di-t-butyl-5,5'-dimethoxydiphenyl (di-BHA), inhibited in a concentration-dependent manner the BaCl 2-induced contraction of muscle incubated in a Ca 2+-free medium. Calculated pIC 50 (M) values ranged between 3.32 (probucol) and 4.96 [3,5-di-t-butyl-4-hydroxyanisole (di-t-BHA)], with intermediate activity shown by khellin < gossypol < guercetin < 3-t-butylanisole < BHA < nordihydroguaiaretic acid (NDGA) < 2,6-di-t-butyl-4-methylphenol (BHT) and papaverine. 3. The Ca 2+ channel activator Bay K 8644 overcame the inhibition sustained by nifedipine, BHA and BHT, while only partially reversing that of papaverine. 4. BHA, BHT, nifedipine and papaverine also inhibited in a concentration-dependent fashion CaCl 2 contractions of muscle depolarized by a K +-rich medium. This inhibition appeared to be inversely affected by the Ca 2+-concentration used. 5. The inhibitory effects of nifedipine, papaverine, BHA and BHT were no longer present when muscle contraction was elicited in skinned fibres by 5 μM Ca 2+ or 500 μM Ba 2+, suggesting a plasmalemmal involvement of target sites in spasmolysis. 6. Comparative antioxidant capability was assessed in two peroxyl radical scavenging assay systems. These were based either on the oxidation of linoleic and initiated by a heat labile azo compound or on lipid peroxidation of rat liver microsomes promoted by Fe 2+ ions. Across both model systems, di-t-BHA, NDGA, BHT, di-BHA,BHA and quercetin ranked as the most potent inhibitors of lipid oxidation, with calculated pIC 50 (M) values ranging between 7.4 and 5.7. 7. Of the 32 compounds studied only 15 phenolic derivatives exhibited both antispasmogenic and antioxidant activity. Within this subgroup a linear and significant correlation was found between antispasmogenic activity and antioxidation. These bifunctional compounds were characterized by the presence of at least one hydroxyl group on the aromatic ring and a highly lipophilic area in the molecule. 8. Di-t-BHA is proposed as a lead reference compound for future synthesis of new antioxidants combining two potentially useful properties in the prevention of tissue damage after ischaemia-reperfusion injury
Neuroprotezione farmacologica del danno da ischemia-riperfusione nella vescica urinaria: approcci sperimentali
No full textThe novel potent multidrug resistance inhibitors N,N-bis(cyclohexanol)amine aryl esters are devoid of vascular effects
No full textThe aim of this study was to investigate the effects of the four isomers (3a, 3b, 3c and 3d) of a novel multidrug resistance-reverting agent - 3,4,5-trimethoxybenzoic acid 4-(methyl-{4-[3-(3,4,5-trimethoxyphenyl)acryloyloxy]cyclohexyl}amino)cyclohexyl ester - on vascular functions in vitro. A comparison of their mechanical and electrophysiological actions in rat aorta rings and single rat tail artery myocytes, respectively, was performed. In rat aorta rings, 3a-d antagonized both 60 mmol/l K(+)- and phenylephrine-induced contraction in a concentration-dependent manner, with maximal relaxation values averaging 50% of controls, 3d being the most effective of the series. The vasorelaxing effect was similar either in presence or absence of intact endothelium. In rat tail artery myocytes, out of the four isomers, only 3a consistently inhibited Ba(2+) current through Ca(v)1.2 channels. Our results provide functional evidence that 3a-d are weak vasorelaxing agents, although at concentrations much higher than those effective for multidrug resistance reversion in cancer cells
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
HPLC determination of inorganic cation levels in CSF and plasma of conscious rabbits
No full textAn HPLC method is described using conductimetric detection for the quantitative determination of sodium, potassium, magnesium, and calcium in cerebrospinal fluid (CSF) and plasma of conscious rabbits. This method enabled the four cations to be estimated with rapidity, sensitivity, accuracy, and precision. The mean millimolar concentrations +/- SD found in CSF and (plasma) of 15 untreated animals were as follows: sodium, 146.96 +/- 17.84 (135.06 +/- 20.11); potassium, 3.32 +/- 0.56 (4.57 +/- 1.03); magnesium, 0.90 +/- 0.20 (0.72 +/- 0.13); and calcium, 1.47 +/- 0.19 (3.32 +/- 0.59)
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