1,720,966 research outputs found
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
Protean agonism at the muscarinic M2 receptor
No full textProtean agonism at the muscarinic M2 receptor
De Min A. (1), Matera C. (2), Messerer R. (3), Dallanoce C. (2), Holzgrabe U. (3), Mohr K. (1)
(1) University of Bonn Pharmacology and Toxicology - Bonn, Deutschland
(2) University of Milan Pharmaceutical Sciences - Milan, Italien
(3) University of Würzburg Pharmaceutical and Medicinal Chemistry - Würzburg, Deutschland
Muscarinic acetylcholine receptors, with their five different subtypes, belong to the class A of GPCRs and have been extensively studied with the purpose of finding selective ligands for their modulation. In this respect, in the last years a new strategy was developed, i.e. the synthesis of so-called dualsteric ligands that bind simultaneously to both the highly conserved orthosteric site and the less conserved allosteric site of the M2 receptor subtype [1].
Recently, we found out that one dualsteric ligand, a hybrid derived from the orthosteric superagonist iperoxo and the negative allosteric modulator naphmethonium, showed a peculiar behavior known as “protean agonism”. Given that protean agonism has not been described so far for muscarinic receptors, additional studies were performed, in order to gain better insight into structure/activity-relationships. Therefore, a series of compounds of different middle chain length and iperoxo-related orthosteric agonist moieties were chosen for testing.
[35S]GTPγS binding assays were carried out in order to study the effect of the hybrids in the Gi signaling pathway. Experiments were performed in Tris buffer either with low sodium concentration, that assured a stable spontaneously active M2 receptor system, or in Tris buffer supplemented with 200 mM NaCl, that abolished M2 constitutive activity.
The results revealed a great variety of activities of the structurally related hybrids, including inverse agonism, partial agonism and protean agonism. The tested compounds had similar potencies (pEC50) in this assay, ranging between 7.5-8.5, except for two protean agonists and one inverse agonist. The former two revealed significantly lower potencies and efficacies in Tris buffer with “low sodium” concentration. These results might suggest that in this buffer the ligands adopt a purely allosteric pose rather than a dualsteric pose. Concerning the inverse agonist, it had a low pEC50 in both buffers. This result might indicate that the hybrid adopts a purely allosteric binding pose in both conditions, thus inactivating the receptor through the negative allosteric fragment.
Taken together, linker length and nature of orthosteric moiety are both relevant in determining the intensity and the direction of the effect. Two protean agonists were identified for the muscarinic M2 receptor.
Antony, J. et al.: FASEB J. 2009, 23: 442-50
Selective activation of different pathways by dualsteric compounds in muscarinic M1 acetylcholine receptors
No full textG protein-coupled receptors (GPCRs) respond to a broad range of different extracellular stimuli, thereby evoking intracellular signaling. Dualsteric compounds bind simultaneously to the receptor’s orthosteric transmitter binding site and its allosteric vestibule [1]. In the muscarinic acetylcholine M2 receptor (M2 mAChR) these dualsteric compounds were shown to impair the activation-related conformational change of the receptor protein by spatial restriction. This can eventually control the signaling pattern of a GPCR that promiscuously activates a variety of different signaling pathways [2]. In the present work, we checked whether this concept could be transferred to the M1-subtype of muscarinic receptors (M1 mAChR) which preferentially signals into Gq/11-dependent pathways, but can also activate Gs and Gi proteins [3]. Therefore, M1 receptor-mediated signaling induced by the orthosteric full agonist iperoxo and several dualsteric compounds were investigated. The latter consist of iperoxo as the orthosteric building block linked to an allosteric phthalimide (phth) or naphthalimide (naph) moiety via alkyl chains of different length. To distinguish between Gq/11- and Gs-dependent signaling pathways, CHO cells stably transfected with the human M1 muscarinic receptor were applied in IP1 and cAMP accumulation assays, respectively. Our findings show that the bulky allosteric naph residue impaired both signaling pathways to a greater extent than the smaller substituent phth. In particular, the hybrid iper-6-naph completely lost intrinsic activity at the M1 mAChR, although M2 mAChR activation by this compound had been demonstrated in a previous study [2]. In contrast to iper-6-naph, the less spacious congener iper-6-phth only lost intrinsic activity for Gs-activation, while it was still a partial agonist for Gq/11-dependent signaling. All other hybrids tested were able to activate both the Gq/11 protein and the Gs protein. Remarkably, iper-7-phth had a significantly higher efficacy for Gs protein activation than all the other compounds under investigation. However, there was no significant difference between iper-7-phth and iper-8-phth for Gq/11-dependent signaling. Furthermore, iper-7-naph and iper-8-naph showed no significant differences in both Gq/11- and Gsassays. Our data indicate that it might be possible to gain subtype selectivity by exploiting the allosteric moiety or the length of the linker chain. In particular, the bitopic derivative iper-6-naph was shown to be a partial agonist at the M2 mAChR, but was not able to activate the M1 mAChR [2]. Taken together, these data demonstrate that, in comparison to Gq/11- mediated signaling, activation of the Gs protein in M1 mAChR is more sensitive to spatial restriction in the allosteric vestibule. Thus, it is possible to control signaling of the M1 mAChR by allosteric constraint of the conformational flexibility.
1. Antony, J. et al.: FASEB J. 2009, 23:442-450.
2. Bock, A. et al.: Nat. Commun. 2012, 3:1044 doi: 10.1038/ncomms2028.
3. Gregory, K.J.; Sexton P.M.; Christopoulos A.: Curr. Neuropharmacol. 2007, 5:157-167
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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