1,720,997 research outputs found
ENKEPHALIN MODULATION OF NEURAL TRANSMISSION IN THE CAT STELLATE GANGLION - PHARMACOLOGICAL ACTIONS OF EXOGENOUS OPIATES
No full textNeural ganglionic transmission was studied in vivo in the cat, using closed chest anesthetized preparations. The right stellate ganglion and its branches were exposed retropleurally and prepared for electrical stimulation of pre- and postganglionic nerve fibers. The axillary artery was cannulated allowing direct administration of drugs in the arterial blood supplying the ganglion. Stimulation of postjunctional receptors could thus be obtained by local administration of selective agents. Local administration of nicotinic, muscarinic or histaminergic agents increased heart rate and blood pressure. Opiates were given either i.v. or locally through the axillary artery: we tested the effects of morphine, Leu-enkephalin (Leu-enk), Met-enkephalin (Met-enk), [d-ala2]-Met-enkephalinamide (DAME) and etorphine. When given locally, Leu-enk (from 10 μg). Met-enk (from 20 μg), DAME (from 5 μg) and etorphine (from 0.2 μg) inhibited tachycardia induced by preganglionic stimulation and reduced the amplitude of the compound action potential recorded from the postganglionic nerve. Morphine (10-200 μg) had no effect. On the other hand, tachycardia induced by postganglionic nerve stimulation was unaffected by opiates in the same experimental conditions. Intravenous administration of similar doses of opiates had no effect on ganglionic transmission. When tachycardia was induced by chemical stimulation of nicotinic (DMPP), muscarinic (McN-A-343-1 l) or histamine receptors in the stellate ganglia, opiates were still active in reducing the effect of these chemicals. These data provide evidence that exogenous opiates exert a depressing action on postsynaptic responses of sympathetic ganglia tested in vivo, although an additional action on presynaptic terminals is not excluded. As endogenous opiates are normally present in various sympathetic ganglia, including the stellate ganglion of the cat, it is possible that they play some modulatory role on ganglionic transmission in physiological conditions
THE ACTION OF AD6 ON EXPERIMENTAL ARRHYTHMIAS AND ON ACTION-POTENTIALS OF CARDIAC FIBERS
No full textACTION OF AD6 (8-MONOCHLORO-3-BETA-DIETHYLAMINOETHYL-4-METHYL-7-ETHOXYCARBONYLMETHOXY COUMARIN) ON HUMAN-PLATELETS INVITRO
No full textThe action of AD6 was tested in vitro on human platelets by measuring beta-thromboglobulin (BTG), platelet factor 4 (PF4) and thromboxane B2 (TXB2) release as well as aggregation. BTG and PF4 release from blood anticoagulated with sodium citrate was inhibited by AD6 during a 3 h incubation. Platelet rich plasma (PRP) was stimulated with ADP, collagen, sodium arachidonate, PAF, A23187 and epinephrine, while resuspended washed platelets (WP) were stimulated by thrombin. AD6 (5-100 μM) inhibited dose dependently aggregation, BTG, PF4 and TXB2 release induced by threshold concentration of all the tested aggregating agents; however AD6 action could be overcome by increasing the concentration of the stimulating agents. After cyclo-oxygenase blockade by acetylsalicylic acid (ASA), PRP was stimulated by a supramaximal concentration of PAF. Under these circumstances we could observe a reversible aggregation and a partial release of BTG and PF4, AD6 was able to further reduce aggregation and release. Cyclic AMP accumulation induced in WP by prostacyclin was not modified by AD6 (100 μM), while theophylline greatly potentiated prostacyclin action. We conclude that AD6 is an inhibitor of platelet activation in vitro. Its mode of action is different from cyclo-oxygenase blockade and provides inhibition of platelet activation by a number of different stimuli
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
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Full text linkWe 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
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