1,720,967 research outputs found
Le vescicole extracellulari come nuovi mediatori di segnali muscolari
Get PDFIl muscolo scheletrico produce e secerne fattori solubili, chiamati miochine in grado di svolgere un‟azione a livello autocrino, paracrino, ed endocrino contribuendo alla riparazione o rigenerazione muscolare. Molte di queste proteine vengono secrete durante l'esercizio fisico e sembrano in parte responsabili dei benefici dell‟attività fisica sulla salute. Quindi, queste evidenze sperimentali hanno dimostrato che il muscolo possiede anche un‟importante attività endocrina. Recentemente, è stato proposto che anche le vescicole extracellulari (EV) possano mediare il cross-talk intercellulare sia in condizioni normali che patologiche attraverso il trasferimento di miRNA specifici. Studi precedenti hanno riportato che mioblasti e miotubi rilasciano EV nell'ambiente extracellulare durante il processo di differenziamento miogenico. Nella prima parte di questa tesi è stato indagato se le cellule C2C12 rilasciano tipologie diverse di EV durante le prime fasi del processo di differenziamento miogenico e se queste possiedono funzioni biologiche. Nella seconda parte, sono stati studiati gli effetti dell‟esercizio fisico sul rilascio di EV da parte del muscolo. In particolare, è stato valutato se l'applicazione di impulsi elettrici (EPS) in miotubi cresciuti in vitro induce la secrezione di EV e infine se il tessuto muscolare rilascia EV nel circolo ematico in seguito ad attività fisica. I dati ottenuti dimostrano che durante le prime fasi del processo di differenziamento miogenico, i miociti rilasciano due tipi di vescicole extracellulari: le microvescicole con un diametro medio di 200 nm, contenenti materiale elettron-denso, e vescicole con caratteristiche esosomiali, caratterizzate da un diametro di circa 50-100 nm contenenti materiale elettron-trasparente. Queste due popolazioni di vescicole presentano anche un diverso contenuto di acidi nucleici, in particolare, quelle caratterizzate da una minor densità hanno elevati livelli di RNA, mentre le vescicole più pesanti mostrano livelli di DNA più abbondanti. Inoltre è stato evidenziato che il rapporto relativo tra queste sub-popolazioni di vescicole cambia nel corso del processo di differenziamento miogenico. Quando utilizzate nel trattamento di cellule target, le EV hanno evidenziato la capacità di influenzare l‟attività delle cellule bersaglio, come miociti e macrofagi, in termini di regolazione genica. Per quel che riguarda l‟effetto della contrazione muscolare sul rilascio di vescicole, è stato dimostrato che la stimolazione mediante EPS induce la secrezione di EV, principalmente esosomi, da parte dei miotubi coltivati in vitro. Inoltre, è stato
ipotizzato che il muscolo possa rilasciare EV anche in vivo. I dati riportati mostrano infatti la presenza, nel plasma, di EV positive all‟alfa-sarcoglicano (SGCA) e arricchite in miR-206, caratteristiche che ne suggeriscono l‟origine muscolare. Infine, è stata trovata una correlazione positiva tra la capacità aerobica, misurata come VO2max e i livelli dei miRNA muscolo-specifici (MyomiRNAs) contenuti nelle EV, e una induzione di miR-133b e miR-181a-5p vescicolari dopo esercizio aerobico acuto. Nel loro insieme, i dati riportati in questa tesi suggeriscono che il muscolo rilascia, nell‟ambiente extracellulare, EV potenzialmente coinvolte nella riparazione, rigenerazione, e rimodellamento muscolare e nel cross-talk con altri organi. Ulteriori studi saranno necessari al fine di definire il contenuto e le funzioni delle EV muscolari, sia in condizioni fisiologiche che patologiche. Tali informazioni permetteranno di comprendere il ruolo delle EV rilasciate dal muscolo nella regolazione dell'omeostasi energetica e potrebbero portare allo sviluppo di nuovi biomarcatori.Myokines are peptides produced and secreted by skeletal muscle, with autocrine, paracrine and endocrine actions that are involved in the regulation of muscle repair or regeneration. Moreover, myokines are overexpressed during physical exercise and appear to contribute to the benefits of exercise to metabolic homeostasis, suggesting that muscle is able to send specific messages in response to various stimuli. It has recently been established that extracellular vesicles (EVs) can mediate intercellular cross-talk under normal and pathological conditions through the transfer of specific miRNAs, which can be taken up by targeting cells changing their biological behavior. In addition, it has been found that myoblasts and myotubes release EVs in the extracellular environment during myogenic differentiation. The aim of this study was to investigate the type of EVs released by C2C12 cells in the early phases of myogenic differentiation process. Furthermore, we tested if the application of an in vitro exercise stimulus, such as electric pulse stimulation (EPS) to myotubes, can modify EV secretion. Finally, we evaluated whether muscle tissue releases EVs in the bloodstream and if physical exercise modulates the levels of MyomiRNAs into EVs. Our data represent new evidence that during the early phase of the myogenic differentiation process, myocytes release two types of extracellular vesicles: microvesicles with a mean diameter of 200 nm containing electron-dense material, and exosome-like vesicles showing a diameter of about 50-100 nm containing electron-transparent material. Moreover, we identify two sub-populations of exosome-like vesicles: one characterized by lower density values and high levels of RNA, and the other showing heavier floating values and abundant DNA. The results obtained also highlight that the relative ratio of these different vesicles changes during the myogenic differentiation process. It is noteworthy that treatments of recipient cells with purified vesicles highlighted that EVs are biologically active entities able to affect the activity of target cells such as myocytes and macrophages. Concerning the effects of exercise on the release of EVs, our data show that myotubes subjected to EPS increase EV secretion compared to control cells. Using Nanoparticles Tracking Analysis (NTA), we demonstrated that contracting cells release EVs that have a diameter falling in the range of exosomes. These
data suggest that muscle fibers could release EVs in response to contracting activity in addition to myokines. Interestingly, we demonstrated that muscle tissue releases EV also in vivo; in fact the presence of EVs with exosomal characteristics in the bloodstream was highlighted, these EVs were positive for alpha-sarcoglycan (SGCA) and enriched for miR-206 confirming their muscle origin. Finally, a significant positive correlation was found between the aerobic fitness, measured as VO2max, and muscle-specific miRNA (MyomiRNA) expression in EVs; moreover, miR-133b and -181a-5p contained in EVs were significantly up-regulated after acute aerobic exercise. Future studies may be designed to deeply explore the content of muscle extracellular vesicles in physiological (e.g. exercise) or pathological (e.g. inactivity, atrophy, diabetes, etc.) conditions. Such efforts could provide insight into the role of EVs not only as useful biomarkers, but also as regulators of the body’s homeostasis. Taken together, this evidence suggest that muscle can release EVs in the extracellular environment which mediate cell-to-cell communication potentially involved in muscle repair, regeneration and remodeling and/or in muscle cross-talk with other organs
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
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
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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