1,721,058 research outputs found
Apprendere le differenze funzionali del microbiota intestinale umano in normali condizioni di salute e in presenza di patologie.
No full textGli argomenti di questo progetto di tesi hanno riguardato il rapporto fra il microbiota intestinale e funzioni associate allo stato di salute dell’uomo.
In un sistema modello in vitro di microbiota intestinale di un neonato di 2 mesi affetto da coliche è stata determinata l’inibizione della crescita delle Enterobacteriaceae da parte di Bifidobacterium breve B632, precedentemente selezionato per specifiche attività probiotiche. Sono state confrontate le quantità dei diversi gruppi microbici mediante FISH e qPCR in colture fecali condotte in parallelo addizionate o meno del ceppo probiotico.
Sulla base delle analisi di RAPD-PCR sui bifidobatteri isolati su terreno selettivo RB, B. breve B632 ha colonizzato le colture di microbiota intestinale rappresentando il 64% dei bifidobatteri totali allo stato stazionario. La concentrazione di Enterobacteriaceae dopo 18 ore di fermentazione, determinata mediante FISH e qPCR, era di 0.42 e 0.44 ordini di grandezza più bassa nelle colture addizionate del ceppo probiotico rispetto ai controlli (p < 0.05). Questi risultati sono estremamente promettenti e indicano la possibilità di proseguire la validazione del probiotico in vivo.
La seconda parte del progetto ha riguardato la caratterizzazione della popolazione batterica proteolitica di soggetti sani adulti. La fermentazione delle proteine produce, oltre ad ammonio ed acidi organici, alcuni metaboliti tossici noti come tossine uremiche: indolo e p-cresolo. In questo studio è stato impiegato un sistema modello in vitro nel quale sono state condotte fermentazioni fecali in un mezzo colturale nel quale erano disponibili proteine e peptidi come fonte di carbonio. L’attività proteolitica è stata confermata dall’accumulo in coltura di ammonio, indolo e p-cresolo, e dal profilo degli acidi organici prodotti. L’identificazione della componente proteolitica è stata determinata mediante sequenziamento degli amplificati del gene codificante l’RNA 16S. I processi fermentativi sono stati condotti utilizzando concentrazioni diverse di inoculo iniziale, onde conferire un vantaggio competitivo ai batteri presenti in quantità più elevate, o a quelli presenti alle concentrazioni più basse. Confrontando l’abbondanza relativa della coltura all’inizio del processo, dopo 6 e 12 ore è stato osservato un aumento in particolare di batteri appartenenti all’ordine dei Clostridiales e alla classe dei Alphaproteobacteria, Deltaproteobacteria e Gammaproteobacteria. E’ bene considerare che la maggior parte dei gruppi microbici identificati è a livello di genere o di cluster. Questo studio necessita quindi di una ulteriore validazione funzionale condotta su colture singole riferibili a specie ben precise.
Nell’ultima parte di questo progetto di tesi è stata studiata la composizione chimica e microbiologica delle feci di due coorti composte da 10 soggetti sani ed 8 pazienti affetti da insufficienza renale cronica. Il pH era significativamente più alto nei pazienti rispetto ai volontari sani, mentre per ammonio, indolo e p-cresolo non è stata osservata alcuna differenza. Le concentrazioni dei carboidrati sono risultate più alte nelle feci dei pazienti rispetto ai sani. Sui medesimi campioni relativi alla coorte dei volontari sani sono state condotte prove di trasformazione di indolo e p-cresolo e verso indolo e p-cresolo (a partire dai precursori triptofano e tirosina) mediante esperimenti con resting cells. Il p-cresolo è molto recalcitrante e viene scarsamente degradato, mentre la trasformazione dell’indolo sembra indotta dalla presenza di elevate concentrazioni dello stesso. Entrambi i metaboliti si accumulano velocemente in presenza dei precursori triptofano e tirosina.The main topics of this thesis project concerned the relationship between the intestinal microbiota and the functions associated to the human health status.
In an in vitro model system of intestinal microbiota it was determined the inhibition of the Enterobacteriaceae growth caused by the Bifidobacterium breve B632 strain, previously selected for its specific probiotic activities. Two groups of fecal cultures were carried out in parallel. One of them is composed by the fermentative processes employing the fecal sample of a 2 months old newborn as inoculum. The second one was performed adding to the fecal culture the probiotic strain.
The concentrations of the different microbial groups have been compared through FISH and qPCR.
Based on the RAPD-PCR results concerning the bifidobacteria isolated on RB selective medium, B. breve B632 colonized the intestinal microbiota cultures representing the 64% of the total bifidobacteria at the steady state. After 18 h of fermentation the Enterobacteriaceae concentration, determined through FISH and qPCR, was of 0.42 and 0.44 order of magnitude lower into the cultures supplemented with the probiotic than the controls ones (p < 0.05). This results are promising and suggest the possibility to proceed to the probiotic validation in vivo.
The second part of the project regarded the characterization of the proteolytic bacterial population in healthy adults. The proteins fermentation produces, in addition to ammonium and organic acids, also some toxic metabolites known as uremic toxins: indole and p-cresol. In this study, in an in vitro model system, fecal fermentations have been carried out in a medium containing only proteins and peptides as carbon source. The proteolytic activity has been confirmed by the accumulation of the ammonium, indole and p-cresol and by the organic acid profile produced. The identification of the proteolytic component of the microbiota has been determined through the sequencing of the amplicones of the gene encoding for the 16S RNA. The fermentations have been carried out using different concentrations of the initial inoculum in order to give a competitive advantage to the bacteria present in higher concentration or to those present at lower concentration. Comparing the culture relative abundances at the beginning of the process and after 6 and 12 h it was observed an increase of the bacteria belonging to the Clostridiales order and to the Alphaproteobacteria, Deltaproteobacteria and Gammaproteobacteria class particularly. It is important to observe that the majority of the bacterial groups is identified at genus or cluster level. For this reason this study needs further functional validation carried out on pure cultures that can be reported to precise species.
In the last part of this project it was studied the chemical and microbiological composition of the feces of two cohorts composed of 10 healthy subjects and 8 patients affected by chronic kidney disease. The pH was significantly higher into the patients groups than the healthy ones, while for the ammonium, indole and p-cresol differences were not observed. The carbohydrates concentrations were higher in the feces of the patients than in those of the volunteers. On the same samples related to the healthy volunteers cohort, the transformation of the indole and p-cresol and the transformation of their precursors (tryptophan and tyrosine) into indole and p-cresol through experiments with resting cells have been carried out. The p-cresol is recalcitrant and it is barely degraded, while the indole transformation seems to be induced by the presence of the higher concentrations of the same metabolite. Both metabolites were quickly accumulated in the presence of the precursors tryptophan and tyrosine
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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