1,720,962 research outputs found
Cystine-mediated oxidative defence in Lactobacillus reuteri BR11
No full textLactobacillus reuteri BR11 possesses an abundant cystine uptake (Cyu) ABC-transporter that was previously found to be involved in a novel mechanism of oxidative defence mediated by cystine. The current study aimed to elucidate this mechanism with a focus on the role of the co-transcribed cystathionine ã-lyase (Cgl). Growth studies of wild-type L. reuteri BR11 and mutants inactivated in cgl and the cystine-binding protein encoding gene cyuC showed that in contrast to the Cyu transporter, whose inactivation led to growth arrest in aerated cultures, Cgl is not crucial for oxidative defence. However, the role of Cgl in oxidative defence became apparent in the presence of severe oxidative damage and cysteine deprivation. Cysteine was found to be protective against oxidative stress, and the action of Cgl in both cysteine biosynthesis and degradation poses a seemingly futile pathway that deprives the intracellular cysteine pool. To further characterise the relationship between Cgl activity and cysteine and their roles in oxidative defence, enzymatic assays were performed on purified Cgl, and intracellular concentrations of cysteine, cystathionine and methionine were determined. Cgl was highly active towards cystine and cystathionine and less active towards cysteine in vitro, suggesting the main function of Cgl to be cysteine biosynthesis. Cysteine was found at high concentrations in the cell, but the levels were not significantly affected by inactivation of cgl or growth under aerobic conditions. It was concluded that both anabolic and catabolic activities of Cgl towards cysteine contribute to oxidative defence, the former by maintaining an intracellular reservoir of thiol analogous to glutathione, and the latter by producing H2S which is readily secreted, thus creating a reducing extracellular environment. The significance of the Cyu transporter to the physiology of L. reuteri BR11 prompted a phylogenetic study to determine its presence in bacteria. Orthologs of the Cyu transporter that are closest matches to the Cyu transporter are only limited to several species of Lactobacillus and Leuconostoc. Outside the Lactobacillales order, the closest matching orthologs belong to Proteobacteria, and there are more orthologs in Proteobacteria than non-Lactobacillales Firmicutes, suggesting that the Cyu transporter locus was present in the ancestor of the Proteobacteria and Firmicutes, and over evolutionary time has been lost or diverged in many Firmicutes. The clustering of the Cyu transporter locus with a gene encoding a Cgl family protein is even rarer. It was only found in L. reuteri, Lactobacillus vaginalis, Weissella paramesenteroides, the Lactobacillus casei group, and several Campylobacter sp. An accompanying phylogenetic study of L. reuteri BR11 using multi-locus sequence analysis showed that L. reuteri BR11 had diverged from more than 100 strains of L. reuteri isolated from various hosts and geographical locations. However, comparison with other Lactobacillus species supported the current classification of BR11 as L. reuteri. The most closely related species to L. reuteri is L. vaginalis or Lactobacillus antri, depending on the housekeeping gene used for analysis. The close evolutionary relationship of L. vaginalis to L. reuteri and the high degree of sequence identity between the cgl-cyuABC loci in both species suggest that the Cyu system is highly likely to perform similar functions in L. vaginalis. In search of other genes that function in oxidative defence, a number of mutants which were inactivated in genes that confer increased resistance to oxidative stress in other bacteria were constructed. The genes targeted were ahpC (peroxidase component of the alkyl hydroperoxide reductase system), tpx (thiol peroxidase), osmC (osmotically induced protein C), mntH (Mn2+/Fe2+ transporter), gshA (ã-glutamylcysteine synthetase) and msrA (methionine sulfoxide reductase). The ahpC and mntH mutants had slightly lower minimum inhibitory concentrations of organic peroxides, suggesting these genes might be involved in resistance to organic peroxides in L. reuteri. However, none of the mutants exhibited growth defects in aerated cultures, in stark contrast to the cyuC mutant. This may be due to compensatory functions of other genes, a hypothesis which cannot be tested until a robust protocol for constructing markerless multiple gene deletion mutants in L. reuteri is developed. These results highlight the importance of the Cyu transporter in oxidative defence and provide a foundation for extending the research of this system in other bacteria
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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