1,721,019 research outputs found
CALCIUM HANDLING IN MYOGENIC PROGENITORS AND SKELETAL MYOBLASTS: THE ROLE OF CD20
Full text linkThe calcium ion plays an essential role in the physiology of all living cells. Accordingly, multiple mechanisms contribute to the precise control of its intracellular concentration ([Ca2+]i). Particularly in skeletal muscle, the efficient regulation of cytosolic Ca2+ is crucial for tissue functionality and impairment of Ca2+ homeostasis has been shown to contribute to the etiology of muscular disorders such as Duchenne muscular dystrophy (DMD). Although the impairment of Ca2+ homeostasis affecting dystrophic muscular cells has been extensively reported, the pathways involved in calcium-release and the role of store-operated Ca2+ channels in dystrophic myogenic progenitors were not investigated before. Among the heterogeneous population of circulating hematopoietic and endothelial progenitors, we identified a subpopulation of CD133+ cells displaying myogenic properties. Interestingly, expression of the B-cell marker CD20 was observed in blood-derived CD133+ stem cells. Among the scarce available data about the biological role of the membrane protein CD20, there are some evidences of its involvement in the regulation of intracellular calcium concentration ([Ca2+]i). Here, we show that a CD20-related pathway leading to an increase of cytosolic calcium is differently activated in normal and dystrophic blood-derived CD133+ stem cells, supporting the assumption of a CD20-related calcium impairment affecting dystrophic cells. Although CD20 can modulate cytosolic calcium through a specific signaling pathway, other studies demonstrated its association with lipid raft domains of the plasma membrane, where it probably functions directly as a store-operated Ca2+ channel. Recent works indicated that store-operated Ca2+ entry (SOCE) plays a central role in skeletal muscle physiology and development, but there remain a number of unresolved issues relating to SOCE modulation in this tissue. That being so, and considering that blood and muscle share common mesodermic origins, we were prompted to investigate whether CD20 contributes to calcium handling in committed muscular cells. Expression of CD20 was observed in skeletal muscle, displaying a membrane localization in myoblasts and adult muscle fibers. Additionally, we showed that inhibition of CD20 resulted in specific impairment of SOCE in C2C12 myoblasts. Together, reported findings contributed to identify deregulated pathways affecting dystrophic stem cells and potentially involved in DMD pathology. Moreover, our results suggested that functional CD20 is required for SOCE to consistently occur in C2C12 myoblasts, providing a novel insight to improve the understanding of store-operated Ca2+ entry regulation in skeletal muscle
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
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