1,720,957 research outputs found
Genetically Separable Functions of the MEC-17 Tubulin Acetyltransferase Affect Microtubule Organization
No full textSummaryBackgroundMicrotubules (MTs) are formed from the lateral association of 11–16 protofilament chains of tubulin dimers, with most cells containing 13-protofilament (13-p) MTs. How these different MTs are formed is unknown, although the number of protofilaments may depend on the nature of the α- and β-tubulins.ResultsHere we show that the enzymatic activity of the Caenorhabiditis elegans α-tubulin acetyltransferase (α-TAT) MEC-17 allows the production of 15-p MTs in the touch receptor neurons (TRNs) MTs. Without MEC-17, MTs with between 11 and 15 protofilaments are seen. Loss of this enzymatic activity also changes the number and organization of the TRN MTs and affects TRN axonal morphology. In contrast, enzymatically inactive MEC-17 is sufficient for touch sensitivity and proper process outgrowth without correcting the MT defects. Thus, in addition to demonstrating that MEC-17 is required for MT structure and organization, our results suggest that the large number of 15-p MTs, normally found in the TRNs, is not essential for mechanosensation.ConclusionThese experiments reveal a specific role for α-TAT in the formation of MTs and in the production of higher order MTs arrays. In addition, our results indicate that the α-TAT protein has functions that require acetyltransferase activity (such as the determination of protofilament number) and others that do not (presence of internal MT structures)
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
Recruitment and function of transcriptional protein complexes
No full textRegulation of gene expression opperates mainly at the level of transcription and results as a consequence of the co-ordinated activity of two categories of regulatory elements, promoters and activators. In this study the in vivo role of both these elements in the recruitment and function of transcriptional complexes was examined. Firstly, the contribution of the promoter architecture in such phenomena was studied. It was revealed that the quality of the TATA element plays a role in nucleosome modifications and selection of coactivators. More importantly this study revealed the existence of a co-transcriptional mechanism that determines the levels of Gcn5-dependent histone acetylation within promoter nucleosomes. Secondly, studies on the contribution of the activator for the recruitment and function of transcriptional complexes revealed a role of the activation domains in determining the transcriptional requirement for specific SAGA components. In addition, a novel function of the Spt3 component of SAGA and of the Mot1 ATPase in nucleosome remodeling was demonstrated. In the last part the study of the contribution of cis-elements revealed the ability of activators to associate in vivo with non promoter euhromatic sites. This association was shown to result in the functional recruitement of SAGA and Swi2/Snf2 complexes. This assemblage of coactivator complexes was proven not to be productive because of the absence of core promoter elements other than the TATA box that are required for stable recruitement of the Mediator.Η ρύθμιση της γονιδιακής έκφρασης επιτελείται κυρίως στο επίπεδο της μεταγραφής των γονιδίων και είναι αποτέλεσμα της συνδυαστικής σχέσης των ρυθμιστικών στοιχείων cis και trans, δηλαδή των υποκινητών και ενεργοποιητών αντίστοιχα. Στη συγκεκριμένη εργασία διερευνήθηκε ο ρόλος των στοιχείων αυτών στη στρατολόγηση και δράση μεταγραφικών συμπλόκων in vivo. Αρχικά αντιμετωπίστηκε το ερώτημα της συνεισφοράς της αρχιτεκτονικής του υποκινητή σε τέτοια φαινόμενα. Προέκυψαν συμπεράσματα σε σχέση με την πιθανότητα συμμετοχής της ποιότητας του στοιχείου ΤΑΤΑ σε θέματα νουκλεοσωμικής αναδιαμόρφωσης, τροποποίησης των ιστονών αλλά και επιλογής για μεταγραφικούς συνενεργοποιητές. Από τέτοιες παρατηρήσεις αναδείχθηκε η ύπαρξη ενός συν-μεταγραφικού μηχανισμού που καθορίζει τα επίπεδα της Gcn5-εξαρτόμενης ακετυλίωσης των υποκινητών. Σε ένα δεύτερο επίπεδο αντιμετωπίστηκε το ακριβώς αντίστροφο ερώτημα της συνεισφοράς του ενεργοποιητή σε θέματα στρατολόγησης και δράσης μεταγραφικών συμπλόκων. Προέκυψαν συμπεράσματα σε σχέση με το ρόλο της θέσης ενεργοποίησης των ενεργοποιητών στον καθορισμό της απαίτησης και του τρόπου δράσης συστατικών του συμπλόκου SAGA ενώ αποκαλύφθηκε ένας μηχανισμός δράσης της υπομονάδας Spt3 του συμπλόκου αυτού, καθώς και της ΑΤΡάσης Μot1, στη νουκλεοσωμική αναδιαμόρφωση. Τέλος, η μελέτη του ρόλου των cis στοιχείων των υποκινητών αποκάλυψε τη δυνατότητα πρόσδεσης ενεργοποιητών σε ευχρωματινικές θέσεις μη υποκινητών μέσα στο γένωμα. Η πρόσδεση αυτή έχει σαν αποτέλεσμα τη στρατολόγηση λειτουργικών συμπλόκων SAGA και Swi2/Snf2 ενώ η συγκρότηση των μεταγραφικών αυτών συμπλόκων δείχθηκε ότι δεν είναι παραγωγική λόγω της απουσίας από τις θέσεις αυτές cis στοιχείων των υποκινητών, ανεξάρτητων του στοιχείου ΤΑΤΑ, που χρειάζονται για τη στρατολόγηση του συμπλόκου του Μediator
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
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