1,721,114 research outputs found
Fibroblast growth factor receptor-1 expression is required for hematopoietic but not endothelial cell development.
No full textObjective—The purpose of this study was to clarify the role of fibroblast growth factors (FGFs) and FGF receptors
(FGFRs) in hematopoietic/endothelial development.
Methods and Results—Using several different FGFR-1–specific antibodies and FGFR-1 promoter-driven LacZ activity,
we show that FGFR-1 is expressed and active as a tyrosine kinase in a subpopulation of endothelial cells (20% of the
endothelial pool) during development in embryoid bodies. In agreement, in stem cell-derived teratomas, expression of
FGFR-1 was detected in some but not all vessels. The FGFR-1 expressing endothelial cells were mitogenically active
in the absence and presence of vascular endothelial growth factor (VEGF). Expression of FGFR-1 in endothelial cell
precursors was not required for vascular development, and vascularization was enhanced in FGFR-1–deficient embryoid
bodies compared with wild-type stem cells. In contrast, hematopoietic development was severely disturbed, with
reduced expression of markers for primitive and definitive hematopoiesis.
Conclusions—Our data show that FGFR-1 is expressed in early hematopoietic/endothelial precursor cells, as well as in a
subpool of endothelial cells in tumor vessels, and that it is critical for hematopoietic but not for vascular development
A Role for All-Trans-Retinoic Acid in the Early Steps of Lymphatic Vasculature Development
Get PDFThe molecular mechanisms that regulate the earliest steps of lymphatic vascular system development are unknown. To identify regulators of lymphatic competence and commitment, we used an in vitro vascular assay with mouse embryonic stem cell-derived embryoid bodies (EBs). We found that incubation with retinoic acid (RA) and, more potently, with RA in combination with cAMP, induced the expression of the lymphatic competence marker LYVE-1 in the vascular structures of the EBs. This effect was dependent on RA receptor (RAR)-alpha and protein kinase A signaling. RA-cAMP incubation also promoted the development of CD31+/LYVE-1+/Prox1+ cell clusters. In situ studies revealed that RAR-alpha is expressed by endothelial cells of the cardinal vein in ED 9.5-11.5 mouse embryos. Timed exposure of mouse and Xenopus embryos to excess of RA upregulated LYVE-1 and VEGFR-3 on embryonic veins and increased formation of Prox1-positive lymphatic progenitors. These findings indicate that RA signaling mediates the earliest steps of lymphatic vasculature development. Copyright (C) 2010 S. Karger AG, Base
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
[Islet of Langerhans transplantation in type I diabetes. Regulation of neovascularization in the transplant is a key question]
No full textDispelling 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
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