1,720,955 research outputs found
ENDOGENOUS NITRIC-OXIDE PROTECTS AGAINST PLATELET-AGGREGATION AND CYCLIC FLOW VARIATIONS IN STENOSED AND ENDOTHELIUM-INJURED ARTERIES
No full textBackground. This study was designed to test the hypothesis that endogenously produced nitric oxide protects against platelet aggregation and cyclic flow variations in stenosed and endothelium-injured arteries of mongrel dogs. Methods and Results. N(G)-Monomethyl-L-arginine (L-NMMA), an inhibitor of nitric oxide formation, was administered at 5 mg/kg to 15 dogs after the left anterior descending coronary artery was mechanically injured and narrowed by external constrictors and to nine dogs before endothelial injury of the femoral artery and after injury and moderate arterial constriction. Treatment with L-NMMA resulted in cyclic How variations (as detected by external Doppler flow probes) in the left anterior descending artery of seven of 15 dogs and in the femoral artery of four of nine dogs after endothelial injury. L-Arginine, the precursor for nitric oxide synthesis, was administered at 60 mg/kg and abolished cyclic flow variations in each of the 11 dogs. D-Arginine did not change the L-NMMA-induced cyclic flow variations. Saline infusion did not induce or change cyclic flow variations in any of the animals. Acetylcholine (1, 10, and 100 mug/min; n=9) was administered in the femoral artery of nine additional dogs before and after endothelial injury in moderately stenosed femoral arteries. Acetylcholine did not induce cyclic flow variations in any animal; however, it did increase the severity of cyclic flow variations that developed in severely stenosed arteries. The diameter of the femoral artery was measured by intravascular ultrasound imaging. L-NMMA caused vasoconstriction of normal arteries, but no change was detected in endothelium-injured arteries. In contraSt, L-arginine caused vasodilation of normal arteries, but, again, no change was noted in endothelium-injured arteries. Acetylcholine dilated normal femoral arteries but constricted arteries with endothelial injury. In both in vitro and ex vivo platelet studies, L-NMMA enhanced platelet aggregation, whereas L-arginine significantly reduced platelet aggregation. D-Arginine and acetylcholine showed no effect on platelet aggregation. Conclusions. Promotion of nitric oxide production decreases platelet aggregation and may eliminate cyclic flow variations, whereas a reduction in nitric oxide formation enhances platelet aggregation and may induce cyclic flow variations. Acetylcholine causes vasoconstriction at the femoral arterial site of endothelial injury and may increase the severity of cyclic flow variations
ENDOGENOUS AND EXOGENOUS NITRIC-OXIDE PROTECT AGAINST INTRACORONARY THROMBOSIS AND REOCCLUSION AFTER THROMBOLYSIS
No full textBackground Nitric oxide (NO), an endothelium-derived relaxing factor, plays an important role in regulating platelet activation. We evaluated the effect of NO in a canine model of intracoronary thrombosis, thrombolysis, and reocclusion. Methods and Results Before thrombosis was induced, 34 anesthetized dogs were treated with a continuous intracoronary infusion of saline (n=8); N-G-nitro-L-arginine (L-NNA, n=8), an inhibitor of NO synthetase; L-arginine (n=7), the precursor for NO; or sodium nitroprusside (SNP, n=11), an NO donor. Ten minutes after the infusion was begun, an electric current of 150 mu A was applied to the endothelium of coronary arteries to induce thrombosis. Occlusive thrombi developed in all dogs in the saline group (38+/-4 minutes) and the L-NNA group (30+/-6 minutes), in 6 of 7 dogs in the L-arginine group (81+/-18 minutes), and in 6 of 11 dogs in the SNP group (102+/-21 minutes) (P.05). After thrombolysis, coronary artery reocclusion developed in all reperfused dogs in the saline group (30+/-8 minutes) and in the L-NNA group (48+/-12 minutes), in 3 (of 4) reperfused dogs in the L-arginine group (123+/-26 minutes), and in 3 (of 4) reperfused dogs in the SNP group (128+/-19 minutes) (P<.01). The ex vivo platelet aggregation induced by collagen was inhibited after in vivo treatment with L-arginine or SNP. Conclusions Increasing NO production or giving an NO donor may inhibit platelet aggregation and delay intracoronary thrombus formation and reocclusion after thrombolysis
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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