1,720,972 research outputs found
Relaxant effects of Hydrastis canadensis L. and its major alkaloids on guinea pig isolated trachea
No full textHydrastis or goldenseal, one of the most popular medicinal herbs in the U.S.A., is used in mild pathological conditions Like cold and flu, based on the pharmacological properties of its active components, berberine (anticholinergic, antisecretory, and antimicrobial) and Beta-hydrastine (astringent). We previously reported the relaxant effect of a total ethanolic extract of hydrastis on carbachol precontracted isolated guinea pig trachea, and with the present study, using the same experimental model, we aimed at evaluating the contribution of its major alkaloids, berberine, Beta-hydrastine, canadine and; canadaline to the total effect. Furthermore, using specific pharmacological tools, like timolol and xanthine amine congener, we attempted to elucidate its mechanism of action. The ECS, of berberine, beta -hydrastine, canadine and canadaline, went 34.2+/-0.6, 72.8+/-0.6, 11.9+/-1.2 and 2.4+/-0.8 mug/ml, respectively. Timolol effectively antagonized the effect of canadine (EC50=19.7+/-3.0 mug/ml) and canadaline (EC50=17.1+/-1.2 mug/ml) but not that of berberine and Beta-hydrastine, while xanthine amine congener antagonized the effect of beta -hydrastine (EC50=149.9+/-35.3 mug/ml) and canadaline (EC50=26.1+/-3.0 mug/ml) but not that of berberine and canadine. Besides, the hydrastis extract, at concentrations between 0.01 and 0.1 mug/ml, potentiated the relaxant effect of isoprenaline on carbachol-precontracted isolated guinea pig trachea. These data, which are insufficient to draw definite mechanistic conclusions, indicate that the aforementioned alkaloids may act by interacting with adrenergic and adenosinic receptors
In vitro relaxant and spasmolytic effects of constituents from Viburnum prunifolium and HPLC quantification of the bioactive isolated iridoids
No full textEthnopharmacological relevance: Viburnum prunifolium is a North America shrub used in ethnomedicine because of its spasmolytic, sedative, and anti-asthmatic properties. Aim of the study: Contrasting results were reported in past literature about the active principles of this plant. Our aim was to clarify this matter by evaluating the relaxant and spasmolytic activities of the main constituents obtained from the drug. Materials and methods: The pharmacological assays were carried out on rabbit jejunum spontaneous contractions and on guinea-pig carbachol-precontracted trachea. Results: Cumulative concentration (1-100 μg/ml) of Viburnum prunifolium methanolic extract (MeOH extract), its purified fractions soluble in ethylacetate (EtOAc fraction) and in n-butanol (BuOH fraction), and the iridoid glucosides (2 × 10-5 to 4 × 10-4 M): 2′-O-acetyldihydropenstemide (1), 2′-O-trans-p-coumaroyldihydropenstemide (2), 2′-O-acetylpatrinoside (3), and patrinoside (4), isolated from EtOAc fraction (1 and 2) and BuOH fraction (3 and 4), induced both relaxant effect of rabbit jejunum spontaneous contractions and spasmolytic effect on guinea-pig carbachol (5.5 × 10-7 M)-precontracted trachea. Propranolol (10-6 M) antagonised all Viburnum prunifolium tested components relaxant and spasmolytic effects. At non-relaxing concentrations (0.5 μg/ml), MeOH extract and its fractions induced a potentiating effect of isoprenaline cumulative concentrations also in both isolated tissues. Conclusion: In both tissues, the order of potency was EtOAc fraction > BuOH fraction > MeOH extract and 1 > 2 > 3 > 4 suggesting that the major iridoids of EtOAc fraction may be considered among the most active compounds. HPLC analysis of the bioactive iridoids indicates that 1 and 2 are present for 7.38% and 14.90% in EtOAc fraction, and 3 and 4 for 18.47% and 8.86% in BuOH fraction. By comparing the values of EC50 of the fractions and compounds isolated from them, we may assume that the iridoids play a significant role in the biological activity of the corresponding fractions. © 2009 Elsevier Ireland Ltd. All rights reserved
New cholinesterase inhibiting bisbenzylisoquinoline alkaloids from Abuta grandifolia
No full textThe phytochemical study of the stem bark and wood of Abuta grandifolia (Mart.) Sandwith led to the identification of four bisbenzylisoquinoline alkaloids (BBIQs), namely (R,S)-2 N-norberbamunine (1), (R,R)-isochondodendrine (2), (S-S)-O4 ''-methyl, Nb-nor-O6 '-demethyl-(+)-curine (3), and (S-S)-O4 ''-methyl, O6 '-demethyl-(+)-curine (4), together with the aporphine alkaloid R-nomuciferine (5), all obtained by countercurrent distribution separation (CCD) and identified on the basis of their spectroscopic data. Alkaloids 3 and 4 were new. All the isolated compounds were tested for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities. 1 was the most active against AChE, whereas 3 and 4 were the most potent against BChE. interestingly, all tested alkaloids are more potent against BChE than against AChE. This selectivity of cholinesterase (ChE) inhibition could be important in order to speculate on their potential therapeutic relevance. (C) 2012 Elsevier B.V. All rights reserved
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
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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