1,720,981 research outputs found
Determination of Muscarinic Agonist Potencies at M1 and M2 Muscarinic Receptors in a Modified Pithed Rat
No full textThe agonistic potencies of (±)muscarine, (±)cis-2-methyl-5-[(dimethylamino)methyl]-1,3 -oxathiolane methiodide (cis-oxathiolane) and its two enantiomers were determined at muscarinic M1 and M2 receptors in the pithed rat. In non-pretreated animals, i.v. administration of these agents produced bradycardic effects mediated by cardiac M2 receptors followed by increases in heart rate mediated by M1 receptors in sympathetic ganglia. As these responses have been shown to partly overlap, "true" M1 and M2 potencies were determined after selective blockade of M1 and M2 receptors by pirenzepine and methoctramine, respectively. A similar rank order of agonist potencies was obtained at M1 and M2 receptors: (+)cis-oxathiolane > (±)cis-oxathiolane > (±)muscarine > (-)cis-oxathiolane. At both receptor subtypes, (+)cis-oxathiolane was considerably more potent (ca. 30-lold) than its corresponding (-) enantiomer indicating that the agonist binding sites of the two receptor subtypes may have similar stereochemical properties. While (±)muscarine showed similar potencies at M1 and M2 receptors, racemic cis-oxathiolane and its two enantiomers showed a slight selectivity (3 - 7 fold) for M1 receptors indicating the potential usefulness of these compounds in the development of selective M1 receptor agonists
Fluoronorepinephrines: further pharmacological evaluation in vitro and inpithed rats
No full textThe effect of 6F-, 5F- and 2F-norepinephrine (6F-, 5F- and 2F-NE) in rat vas deferens, guinea-pig ileum and pithed rats was compared to that of norepinephrine (NE). The rank order of potency on postsynaptic alpha1-adrenoreceptors, determined from the isometric contraction of vas deferens, was 6F-NE = 5F-NE = NE > 2F-NE. A similar pattern was found for presynaptic alpha2-adrenoreceptor activity in both noradrenergic nerve terminals of vas deferens and cholinergic nerve terminals of the ileum, determined from the inhibition of contraction elicited by electrical field stimulation. The only exception was the 5F isomer which was 7 times less active than NE to activate the alpha2-adrenoreceptors of vas deferens. Thus, ring fluorination markedly alters both alpha1- and alpha2-agonist properties of NE. Moreover, selectivity, at least as far as rat vas deferens is concerned, is not significantly influenced by the introduction of a fluorine atom in the NE molecule. 6F-NE was about 3–4 times more active than NE in pithed rats. In turn, NE was equiactive with 5F-NE. 2F-NE was the least active isomer, being 30- and 100-fold less active than NE and 6F-NE, respectively
Determination of Muscarinic Agonist Potencies at M1 and M2 Receptors in Pithed Rat
No full textThe agonist potency of 2-cia-methyl-5-dimethylaminomethyl-1,3-oxathiolane-3-traqns-oxide methiodide and its two enantiomers were detemined in vivo at muscarinic M1 and M2 receptors. The results indicate a selectivity of 5-8 fold for M1 receptors, confirming the M1 profile of the oxathiolane nucleus
Possible influence of tachykinins on body fluid homeostasis in the rat
No full textThe effect on water intake, urine flow and vasopressin release of intracranial injections of substance P, physalaemin and eledoisin was studied in Wistar and Brattleboro, homozygous and heterozygous, rats. The tachykinins strongly inhibited water intake both in Wistar and in Brattleboro, homozygous and heterozygous, rats. Physalaemin and eledoisin reduced urine flow in Wistar and heterozygous, but not in homozygous, Brattleboro rats. Substance P never affected urine elimination. Physalaemin and eledoisin produced a dose-dependent, long lasting release of vasopressin in Wistar rats. Substance P did not affect the release of vasopressin. The results suggest that both substance P and physalaemin could influence brain mechanisms which control water intake, acting as thirst inhibitors, and that physalaemin could also participate in body fluid control by conserving water through vasopressin release
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
POSTNATAL DEVELOPMENT OF DOPAMINE RECEPTOR EXPRESSION IN RAT PERIPHERAL BLOOD LYMPHOCYTES.
No full textIF.2.866
Geriatrics and Gerontology
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