1,720,961 research outputs found
Effetto del desametasone, impiegato come promotore della crescita, sull'espressione di geni glucocorticoido-responsivi nel fegato e nel testicolo di bovino
No full textNegli ultimi anni particolare importanza ha assunto la tossicogenomica, cioè lo studio delle correlazioni tra la struttura e l’attività del genoma e gli effetti tossici degli xenobiotici [1].
Il bovino, rappresenta una delle specie di interesse veterinario economicamente più importanti. Proprio per questo l’incremento delle performance zootecniche tramite la somministrazione di promotori della crescita (PC) resta uno dei temi più impegnativi da affrontare nell’ambito della Sanità Pubblica. A livello di Unione Europea l’uso dei PC è vietato (Dir. CEE 96/22 e 96/23); ciononostante, risultati ottenuti a seguito di controlli ufficiali sembrano indicare un uso continuo di sostanze quali ormoni anabolizzanti, β-agonisti e corticosteroidi come il desametasone (DEX) [2]. Da qui la necessità di chiarire gli effetti dei PC sulla specie bovina nonché, eventualmente, individuare potenziali biomarcatori molecolari di trattamento illecito tramite metodiche diagnostiche specifiche e sensibili.
Nel corso del presente studio sono state condotte prove sperimentali in cui il DEX è stato somministrato, nel bovino, utilizzando protocolli di trattamento illecito presumibilmente utilizzati nell’allevamento intensivo del bovino da carne. In particolare, il DEX è stato somministrato a basse dosi e per almeno tre settimane durante la fase di finissaggio (quella che precede la macellazione). Al termine della fase sperimentale, gli animali sono stati macellati e aliquote di fegato e testicolo sono state prelevate, poste in RNA-later e congelate a -80°C sino al momento dell’analisi. Gli effetti del corticosteroide sono stati indagati su geni notoriamente classificati come DEX-responsivi nell’uomo e nelle specie da laboratorio, quali il recettore per i glucocorticoidi (GR), il fattore di trascrizione pregnane X receptor (PXR), la tirosina aminotransferasi (TAT) ed il citocromo P450 3A4-like (CYP3A4-like). Le eventuali variazioni dei profili di espressione genica imputabili al trattamento con PC sono state determinate ricorrendo alla tecnica della RT-real time PCR ed utilizzando la chimica/fluoroforo del Sybr Green.
Entrambe le matrici considerate hanno in primis palesato lo stesso pattern di modulazione a seguito della somministrazione di DEX. In particolare, e sorprendentemente, si è riscontrata una generale riduzione delle quantità di RNA messaggero che, nel caso del CYP3A4-like, è risultata essere significativa (p<0.01) a livello testicolare.
Tali risultati sembrano apparentemente in contrasto con quanto riportato in letteratura. Il desametasone, infatti, è in grado di indurre l’espressione del CYP3A4 in epatociti umani in coltura primaria mediante l’attivazione di GR e PXR secondo un processo bifasico: a basse concentrazioni (10-7 M) il CYP3A4 viene indotto indipendentemente dallo xenobiotico grazie all’attivazione GR-mediata di PXR; a concentrazioni maggiori (10-5 M), invece, il DEX lega e attiva il PXR, che a sua volta induce il CYP3A4 per la presenza di alte concentrazioni del ligando specifico [3]. I risultati ottenuti nel corso del presente studio e relativi a GR e PXR sarebbero confermati anche dalla TAT, un gene considerato un ottimo modello per la valutazione degli effetti degli xenobiotici sull’espressione del GR [4], sebbene risultati contraddittori siano stati già riportati in letteratura [5-6].
Pertanto, l’effetto riscontrato nel bovino a seguito del trattamento con DEX potrebbe essere imputato: a) alle basse dosi impiegate; b) ad un diverso meccanismo d’azione di questa molecola nella specie bovina, analogamente a quanto è già stato riscontrato tra coniglio e ratto [7]. Infatti, indagini filogenetiche sulla famiglia del CYP3A hanno evidenziato differenze di sequenza dell’isoforma proteica tali per cui il CYP3A4-like di bovino dovrebbe essere più correttamente denominato CYP3A28, indice di un potenziale diverso comportamento biochimico tra bovino e altre specie (Giantin et al., dati personali). Infine, uno studio recente ha dimostrato la presenza di differenze di specie nel ligand binding domain di PXR e di conseguenza nell’affinità di ligandi specifici nei confronti di questo stesso recettore [8].
Nel complesso rimangono aperti più spunti di ricerca e le prospettive future saranno dunque quelle di approfondire i risultati preliminari ottenuti e di chiarire alcuni degli aspetti di difficile interpretazione qui riscontrati, nel tentativo di apportare nuove conoscenze sugli effetti dei PC sul trascrittoma del bovino
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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