1,720,989 research outputs found
“Potential biological meaning and origin of cardiac progenitor cells isolated as Cardiospheres"
Full text linkSeveral populations of progenitor cells have been identified in the adult heart, based on the expression of specific surface markers (c-kit, Sca1), or on functional properties, such as the ability to spontaneously migrate from tissue explants and grow in three dimensional structures, called cardiospheres (CSs). CSs represent a niche-like microtissue with a cardiogenic gradient of differentiation towards the periphery. It is not clear which is the origin of these endogenous progenitor populations and how they function in vivo, given the limited regenerative capacity of the heart. Several possibilities can be envisioned. These cells could be remnants of the embryonic development, or derive from the de-differentiation of cardiomyocytes. To test this hypothesis we used a double transgenic mouse expressing the recombinase MerCreMer under the cardiomyocyte-specific αMyosin-Heavy-Chain promoter. After a pulse with 4OH-tamoxifen (TAM) the activated Cre removes a stop signal between two LoxP sequences, allowing the expression of the reporter gene LacZ, in a spatial and temporal regulated manner. Ideally with this system all the differentiated cardiomyocytes should be irreversibly labeled after TAM treatment, even if they subsequently undergo de-differentiation. B-gal positive cells were very rare in culture, as shown by x-gal staining and real time PCR, suggesting that cardiomyocytes de-differentiation is not the main mechanism underlying CSs formation. However, given the limited sensibility of this method (the efficiency of recombination in the cardiomyocytes is 80% at maximum), we cannot conclusively exclude the occurrence of this phenomenon. Using another transgenic mouse strain, in which epicardial and epicardial-derived cells are labeled, we observed a large number of positive cells at all culture stages. Our hypothesis, supported by RT-PCR data, is that epicardial-derived cells undergo mesenchyma-to-epithelium (MET) transition during cardiospheres formation. This is consistent with a recent report presenting MET as a crucial mechanism in cell reprogramming.Pasteur Institute- Cenci Bolognetti Foundatio
Biochemistry and biology. Heart-to-heart to investigate cardiac progenitor cells
No full textBackground: Cardiac regenerative medicine is a rapidly evolving field, with promising future developments for effective personalized treatments. Several stem/progenitor cells are candidates for cardiac cell therapy, and emerging evidence suggests how multiple metabolic and biochemical pathways strictly regulate their fate and renewal. Scope of review: In this review, we will explore a selection of areas of common interest for biology and biochemistry concerning stem/progenitor cells, and in particular cardiac progenitor cells. Numerous regulatory mechanisms have been identified that link stem cell signaling and functions to the modulation of metabolic pathways, and vice versa. Pharmacological treatments and culture requirements may be exploited to modulate stem cell pluripotency and self-renewal, possibly boosting their regenerative potential for cell therapy. Major conclusions: Mitochondria and their many related metabolites and messengers, such as oxygen, ROS, calcium and glucose, have a crucial role in regulating stem cell fate and the balance of their functions, together with many metabolic enzymes. Furthermore, protein biochemistry and proteomics can provide precious clues on the definition of different progenitor cell populations, their physiology and their autocrine/paracrine regulatory/signaling networks. General significance: Interdisciplinary approaches between biology and biochemistry can provide productive insights on stem/progenitor cells, allowing the development of novel strategies and protocols for effective cardiac cell therapy clinical translation. This article is part of a Special Issue entitled Biochemistry of Stem Cells. © 2012 Elsevier B.V
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
A chemical biology approach to myocardial regeneration
No full textHeart failure is one of the major causes of death in the Western world because cardiac muscle loss is largely irreversible and can lead to a relentless decline in cardiac function. Novel therapies are needed since the only therapy to effectively replace lost myocytes today is transplantation of the entire heart. The advent of embryonic and induced pluripotent stem cell (ESC/iPSC) technologies offers the unprecedented possibility of devising cell replacement therapies for numerous degenerative disorders. Not only are ESCs and iPSCs a plausible source of cardiomyocytes in vitro for transplantation, they are also useful tools to elucidate the biology of stem cells that reside in the adult heart and define signaling molecules that might enhance the limited regenerative capability of the adult human heart. Here, we review the extracellular factors that control stem cell cardiomyogenesis and describe new approaches that combine embryology with stem cell biology to discover drug-like small molecules that stimulate cardiogenesis and potentially contribute to the development of pharmaceutical strategies for heart muscle regeneration. © Springer Science+Business Media, LLC 2011
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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