1,721,119 research outputs found
Satellite cells, myoblasts and other occasional myogenic progenitors : possible origin, phenotypic traits and role in muscle regeneration
No full textIn the vertebrate embryo, skeletal muscle originates from somites and is formed in discrete steps by different classes of progenitor cells. After myotome formation, embryonic myoblasts give rise to primary fibers in the embryo, while fetal myoblasts give rise to secondary fibers, initially smaller and surrounding primary fibers. Satellite cells appear underneath the newly formed basal lamina that develops around each fiber, and contribute to post-natal growth and regeneration of muscle fibers. Recently, different types of non somitic stem-progenitor cells have been shown to contribute to muscle regeneration. The origin of these different cell types and their possible lineage relationships with
other myogenic cells as well as their possible role in muscle regeneration will be discussed. Finally, possible use of different myogenic cells in experimental protocols of cell therapy will be briefly outlined
REDUCED ACETYLCHOLINE-INDUCED CHANNEL ACTIVITY IN DYSTROPHIC MOUSE MYOTUBES
No full textSingle channel recording patch-clamp technique was used in the mouse to compare the acetylcholine (ACh)-induced channel behaviour between normal and dystrophic myotubes. While open time and slope conductance were equivalent, ACh-induced channel opening frequency was more than 4-fold reduced in dystrophic compared to normal myotubes. In addition, the steady-state phosphorylation of the ACh receptor (AChR), tested by immunoprecipitation of 32P-labeled cells, indicated that the α-subunit was more heavily phosphorylated in the dystrophic myotubes. We propose that the degree of α-subunit phosphorylation of the AChR, which parallels the reduced AChR-channel opening probability, determines desensitization of the AChR in dystrophic myotubes
Pharmacological activation and reprogramming of muscle cells to acquire an earlier, pluripotent, circulating "stem-like" behaviour, suitable for therapeutical applications
No full textGary Coulton, Giulio Cossu, Roberto Bottinell
Acetylcholine receptor channels are present in undifferentiated satellite cells but not in embryonic myoblasts in culture
No full textThe expression and the physiological properties of acetylcholine receptors (AChRs) of mononucleated myogenic cells, isolated from either embryonic or adult muscle of the mouse, have been investigated using the gigaohm seal patch-clamp technique in combination with immunocytochemistry (with an anti-myosin antibody) and alpha-bungarotoxin binding techniques. Undifferentiated (myosin-negative) embryonic myoblasts, grown either in mass culture or under clonal conditions, were found to be unresponsive to ACh and did not bind alpha-bungarotoxin. On the contrary, undifferentiated satellite cells (from adult muscle) exhibited channels activated by ACh and alpha-bungarotoxin binding sites similar to those observed in differentiated (myosin-positive) embryonic myoblasts and myotubes. Two classes of ACh-activated channels with different opening frequencies were identified. The major class of channels had a conductance of about 42 pS and mean open time of 3.1-8.2 msec. The minor class of channels had smaller conductance (about 17 pS) and similar open time. During differentiation, the conductance of the two channels did not change significantly, while channel lifetime became shorter in myotubes derived from satellite cells but not in myotubes derived from embryonic myoblasts. The relative proportion of small over large channels was significantly larger in embryonic than in adult myogenic cells
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
Sphingosine 1-phosphate mediates proliferation and survival of mesoangioblasts
No full textMesoangioblasts are stem cells capable of differentiating in various mesodermal tissues and are presently regarded as suitable candidates for cell therapy of muscle degenerative diseases, as well as myocardial infarction. The enhancement of their proliferation and survival after injection in vivo could greatly improve their ability to repopulate damaged tissues. In this study, we show that the bioactive sphingolipid sphingosine 1-phosphate (S1P) regulates critical functions of mesoangioblast cell biology. S1P evoked a full mitogenic response in mesoangioblasts, measured by labeled thymidine incorporation and cell counting. Moreover, S1P strongly counteracted the apoptotic process triggered by stimuli as diverse as serum deprivation, C2-ceramide treatment, or staurosporine treatment, as assessed by cell counting, as well as histone-associated fragments and caspase-3 activity determinations. S1P acts both as an intracellular messenger and through specific membrane receptors. Real-time polymerase chain reaction analysis revealed that mesoangioblasts express the S1P-specific receptor S1P3 and, to a minor extent, S1P1 and S1P2. By using S1P receptor subtype-specific agonists and antagonists, we found that the proliferative response to S1P was mediated mainly by S1P2. By contrast, the antiapoptotic effect did not implicate S1P receptors. These findings demonstrate an important role of S1P in mesoangioblast proliferation and survival and indicate that targeting modulation of S1P-dependent signaling pathways may be used to improve the efficiency of muscle repair by these cells. Disclosure of potential conflicts of interest is found at the end of this article
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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