1,721,077 research outputs found
Protein phosphatase 2A (PP2A) is required for the maintenance of Drosophila chromosome integrity
Full text linkCellular responses to DNA damage are based on signal-transduction pathways involving phosphorylation-dephosphorylation events. Recent literature has demonstrated that protein serine/threonine phosphatases have important functions in DNA damage response (DDR). In particular growing evidence indicate that the protein phosphatase 2A (PP2A) plays a crucial role in genome stability maintenance, acts as tumor suppressor and is mutated in some cancer types. However current knowledge on the mechanisms and the pathways linking PP2A to DDR is still rudimentary.
Although most of the roles of PP2A are evolutionarily conserved, there are at present very few data suggesting an involvement of Drosophila PP2A in DNA repair. In the course of a screening aimed at identifying new Drosophila genes involved in the maintenance of genome stability we found an allele of twins (tws) gene, encoding the regulatory PP2A B subunit, that caused frequent chromosome aberrations (CABs), suggesting that also in Drosophila this phosphatase is involved in DNA repair. We observed that all previously identified alleles at the tws locus also caused CABs and high frequency of spontaneous γ-H2Av foci. Moreover tws mutations determined γ-H2Av foci persistence in irradiated brain cells, indicating that Tws promotes foci regression by dephosphorylating γ-H2Av. We also demonstrated that mutants in the Pp4-19C gene, that encodes the PP4 catalytic subunit, affected γ-H2Av foci dissolution but not exhibited CABs suggesting that impaired foci regression is not sufficient to cause CABs.
PP2A and PP4 are also involved in the G2/M checkpoint. In irradiated tws mutant brains the mitotic index (MI) did not drop at 15 minutes (min) as in control cells, but remained similar to that of non-irradiated controls without significant variations over time. In contrast in Pp4-19C mutant cells MI dropped at 15 min after irradiation but the recovery was significantly delayed. These data indicate that PP2A and PP4 are both implicated in the G2/M checkpoint although with different roles.
To better understand the origin of CABs in tws mutants we tried to individuate Tws substrates by cytological examination of double mutants carrying tws mutation and mutations in genes involved in DDR pathway. This analysis revealed that mutations in the ATM-coding gene tefu and mutations in ku70 gene, encoding a component of NHEJ system, are both perfectly epistatic to tws mutations. From these data we deduced that Tws controls genome integrity through a pathway in which Ku70 is first phosphorylated by ATM and then dephosphorylated by Tws (that perhaps dephosphorylates also ATM itself) to allow DNA repair. Therefore, in tws mutants CABs are induced by the hyperphosphorylation status of Ku70
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
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