1,721,065 research outputs found
Influence of subinhibitory concentrations of protein-synthesis-inhibiting antibiotics on production and release of the pneumococcal virulence factor pneumolysin in vitro
No full textOBJECTIVE: Pneumolysin is an important virulence factor of Streptococcus pneumoniae with cytotoxic and proinflammatory activities released during growth and autolysis. At concentrations above the minimal inhibitory concentration, the protein-synthesis-inhibiting antibiotics erythromycin, clindamycin and rifampicin inhibit the production and/or release of virulence factors in various bacterial species. We investigated the influence of subinhibitory concentrations of these antibiotics on production and release of pneumolysin by S. pneumoniae strain D39.METHODS: The pneumococcal strain D39 was grown in broth and treated with antibiotics at a concentration of 1/32 of the respective minimal inhibitory concentration. Cytoplasmic and extracellular pneumolysin was measured by quantitative immunoblotting with recombinant pneumolysin as standard.RESULTS: The subinhibitory antibiotic concentrations evaluated did not affect bacterial growth. During logarithmic growth, production of pneumolysin was decreased by clindamycin, erythromycin and rifampicin by approximately 50% compared with untreated controls. The release of pneumolysin was decreased to a similar extent.CONCLUSION: A decrease in pneumolysin production by 50% probably has a moderate biological effect. We do not advocate the use of subinhibitory concentrations of antibiotics to modulate the expression of virulence factors during pneumococcal disease, particularly with regard to the risk of development of antibiotic resistance.</p
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
Genetic analysis of diverse disease-causing pneumococci indicates high levels of diversity within serotypes and capsule switching
No full textWe have used multilocus sequence typing (MLST) and serotyping to build a phylogenetic framework for pneumococcal disease isolates in Scotland that provides a snapshot of the relationships between capsular type and genotype. The results show that while the MLST type correlates with the serotype, isolates within a serotype can belong to a number of individual clonal complexes or sequence types (STs). We also show that isolates of the same ST can express different capsular polysaccharides, i.e., display capsular switching, and that this phenomenon is observed both for capsular types commonly isolated from patients with invasive disease and for serogroups less commonly isolated from patients with invasive disease but which may commonly be carried asymptomatically in the human nasopharynx.</p
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
Dose-dependent activation of microglial cells by Toll-like receptor agonists alone and in combination
No full textMicroglial cells express Toll-like receptors (TLRs) recognising exogenous and endogenous ligands. Upon stimulation with agonists of TLR2, TLR4, and TLR9, nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) were released by primary mouse microglial cell cultures. Endotoxin was most potent in stimulating microglia followed by pneumolysin, cytosine-guanosine (CpG) oligodesoxynucleotide (ODN), and Tripalmitoyl-S-glyceryl-cysteine. Maximum stimulation of TLR2, TLR4, and TLR9 resulted in approximately equal amounts of nitric oxide release. Pneumolysin was a potent activator of microglial cells; at high concentrations, it reduced cell viability. No cytotoxicity was noted with the other TLR agonists. Costimulation with maximum concentrations of two TLR agonists did not further increase nitric oxide release. Costimulation with submaximum concentrations was additive or supraadditive, suggesting that even low concentrations of products of infectious agents can lead to microglial activation via TLRs.</p
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