1,720,958 research outputs found
Involvement of epigenetic factors and metabolism in pluripotency maintenance in C. elegans
Get PDFDuring the development of multi-cellular organisms, cells undergo differentiation into
distinct cell types. Acquisition of different fates is a consequence of intermingled
multiple external stimuli (non cell autonomous) and internal events (cell autonomous).
The external stimuli include metabolism (in the sense of feeding) and contacts with
neighbouring cells which impact the cell context and modify its life history. This leads
to changes in chromatin organization and the accessibility of target genes to
transcription factors. Cell fate acquisition or differentiation is often a one-way path:
differentiated cells do not change fate. Recently however, the setup of the induction
of pluripotent stem cells (iPSCs) showed that differentiated cells can be
reprogrammed, based on the expression of specific transcription factors. IPSCs
formation correlates with heterochromatin loss.
In C. elegans, the absence of MES-2, the enzymatic core of the Polycomb complex
responsible for histone 3 lysine 27 (H3K27) methylation in heterochromatin, leads to
increased cell fate plasticity during embryonic development, measured as the
capacity to convert embryos into specific tissues by the ectopic expression of cell-fate
specifying transcription factors (cell fate challenge). Here we describe a controlled
cell fate challenge system using single copy transgenes, tractable in both embryonic
and larval stages. In embryos, similar results were obtained as for previous multicopy
arrays, with an extension of the plasticity window in the absence of H3K27
methylation. When muscle differentiation was induced in the first larval stage, worms
lacking H3K27me arrested their development, while an increased number of cells
expressing the muscle marker. Numerous non terminally differentiated lineages were
perturbed, including the V, M and P ones, mostly with unscheduled cell division.
Furthermore, ectopic muscle induction led to the division of bona fide muscle cells.
These organismal and cellular phenotypes could be rescued by knock-down of
multiple components of the Notch pathway, a cell-cell signalling pathway implicated
in asymmetric fate decisions. Interestingly, another regulator of plasticity appears to
be food availability, as starved animals are resistant to cell fate challenge. I showed
that the presence of food leads to visible reorganization of chromatin, potentially
rendering target sites accessible to the specifying transcription factors. The
presence/absence of food appear to be sensed and transduced by the insulin/insulinlike
pathway, as a daf-2 reduction of function mutation ablates the starvation-induced
cell fate challenge resistance. Although I cannot exclude the involvement of other
pathways, this work provides evidence for the function of external stimuli on cell
plasticity determination
Molecular Cloning And Testicular Expression Of VIP In Different Phases Of The Reproductive Cycle Of The Wall Lizard Podarcis sicula
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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
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