1,720,954 research outputs found
Characterization of SfPgdA, a Shigella flexneri peptidoglycan deacetylase required for bacterial persistence within polymorphonuclear neutrophils
No full textPeptidoglycan deacetylases protect the Gram-positive bacteria cell wall from host lysozymes by deacetylating peptidoglycan. Sequence analysis of the genome of Shigella flexneri predicts a putative polysaccharide deacetylase encoded by the plasmidic gene orf185, renamed here SfpgdA. We demonstrated a peptidoglycan deacetylase (PGD) activity with the purified SfPgdA in vitro. To investigate the role SfPgdA in virulence, we constructed a SfpgdA mutant and studied its phenotype in vitro. The mutant showed an increased sensitivity to lysozyme compared to the parental strain. Moreover, the mutant was rapidly killed by polymorphonuclear neutrophils (PMNs). Specific substitution of histidines residues 120 and 125, located within the PGD catalytic domain, by phenylalanine abolished SfPgdA function. SfPgdA expression is controlled by PhoP. Mutation of phoP increases sensitivity to lysozyme compared to the SfpgdA mutant. Here, we confirmed that SfPgdA expression is enhanced under low magnesium concentration and not produced by the phoP mutant. Ectopic expression of SfPgdA in the phoP mutant restored lysozyme resistance and parental bacterial persistence within PMNs. Together our results indicate that PG deacetylation mechanism likely contributes to Shigella persistence by subverting detection by the host immune system.info:eu-repo/semantics/publishe
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
Inactivation of the sfgtr4 gene of shigella flexneri induces biofilm formation and affects bacterial pathogenicity
No full textBiofilm formation is a significant cause for the environmental persistence of foodborne pathogens. This phenomenon remains misunderstood in Shigella flexneri whose pathogenicity is mainly associated with the virulence plasmid pWR100. Sequence analysis of the latter predicts a putative lipopolysaccharides (LPS) glycosyltransferase (Gtr) encoded by Sfgtr4, which is the second gene of the SfpgdA-orf186-virK-msbB2 locus. We demonstrated here that purified SfGtr4 exhibited a Gtr activity in vitro by transferring glucose to lipid A. To establish the role of SfGtr4 in virulence, we generated a Sfgtr4 mutant and assessed its phenotype in vitro. Sfgtr4 mutant significantly reduced HeLa cells invasion without impairing type III effectors secretion, increased susceptibility to lysozyme degradation, and enhanced bacterial killing by polymorphonuclear neutrophils (PMNs). SfGtr4 is related to proteins required in biofilm formation. We established conditions whereby wild-type Shigella formed biofilm and revealed that its appearance was accelerated by the Sfgtr4 mutant. Additional phenotypical analysis revealed that single SfpdgA and double SfpgdA-Sfgtr4 mutants behaved similarly to Sfgtr4 mutant. Furthermore, a molecular interaction between SfGtr4 and SfPgdA was identified. In summary, the dual contribution of SfGtr4 and SfPgdA to the pathogenicity and the regulation biofilm formation by S. flexneri was demonstrated here.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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