1,720,980 research outputs found
Mutations upstream of fabI in triclosan resistant Staphylococcus aureus strains are associated with elevated fabI gene expression
No full textBackground: The enoyl-acyl carrier protein (ACP) reductase enzyme (FabI) is the target for a series of antimicrobial agents including novel compounds in clinical trial and the biocide triclosan. Mutations in fabI and heterodiploidy for fabI have been shown to confer resistance in S. aureus strains in a previous study. Here we further determined the fabI upstream sequence of a selection of these strains and the gene expression levels in strains with promoter region mutations.
Results: Mutations in the fabI promoter were found in 18% of triclosan resistant clinical isolates, regardless the previously identified molecular mechanism conferring resistance. Although not significant, a higher rate of promoter mutations were found in strains without previously described mechanisms of resistance. Some of the mutations identified in the clinical isolates were also detected in a series of laboratory mutants. Microarray analysis of selected laboratory mutants with fabI promoter region mutations, grown in the absence of triclosan, revealed increased fabI expression in three out of four tested strains. In two of these strains, only few genes other than fabI were upregulated. Consistently with these data, whole genome sequencing of in vitro selected mutants identified only few mutations except the upstream and coding regions of fabI, with the promoter mutation as the most probable cause of fabI overexpression. Importantly the gene expression profiling of clinical isolates containing similar mutations in the fabI promoter also showed, when compared to unrelated non-mutated isolates, a significant up-regulation of fabI.
Conclusions: In conclusion, we have demonstrated the presence of C34T, T109G, and A101C mutations in the fabI promoter region of strains with fabI up-regulation, both in clinical isolates and/or laboratory mutants. These data provide further observations linking mutations upstream fabI with up-regulated expression of the fabI gene
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
Pathogenic differences of type 1 restriction-modification allele variants in experimental Listeria monocytogenes meningitis
Full text linkBackground: L. monocytogenes meningoencephalitis has a mortality rate of up to
50% and neurofunctional sequelae are common. Type I restriction-modification systems
(RMS) are capable of adding methyl groups to the host genome. Some contain multiple
sequence recognition (hsdS) genes that recombine, resulting in distinct DNA methylation
patterns and patterns of gene expression. These phenotypic switches have been linked
to virulence and have recently been discovered in multiple clonal complexes of L.
monocytogenes. In the present study, we investigated the significant of RMS on L.
monocytogenes virulence during the acute phase of experimental meningitis.
Methods: L. monocytogenes strains containing RMS systems were identified, and
purified clones enriched for single hsdS alleles were isolated. In vivo, 11-day old Wistar
rats were infected with an inoculum containing (a) one of 4 single RMS allele variants
(A, B, C, D) treated with amoxicillin (AMX 50 mg/kg/dosis, q8h), (b) a mixture of all 4
variants with or without AMX treatment, or (c) differentmixtures of 2 RMS allele variants. At
selected time points after infection, clinical and inflammatory parameters, bacterial titers
and brain damage were determined. Changes in the relative frequency of the occurring
RMS alleles in the inoculum and in CSF or cerebellum of infected animals were analyzed
by capillary electrophoresis.
Results: We have identified a phase variable RMS locus within L. monocytogenes
CC4 and generated stocks that stably expressed each of the possible hsdS genes
within that loci. Generation of these allele variants (A, B, C, D) allowed us to determine
the methylation pattern associated with each hsdS through SMRT sequencing. In vivo
infections with these single allele variants revealed differences in disease severity in that
C induced the worst clinical outcome and more pronounced hippocampal apoptosis;
D showed the most pronounced weight loss and the highest bacterial titer in the
cerebellum. A caused the least severe disease.
Conclusion: We identified that L. monocytogenes expressing hsdS (A) causes less
damage than when other hsdS genes are expressed. While expression of hsdSC and
D worsened the outcome in L. monocytogenes meningitis. We also demonstrate a
competitive advantage of variants C and B over variant A in this model. Phenotypical
switching may therefore represent a mechanism of virulence regulation during the acute
phase of CNS infections with L. monocytogenes
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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