1,720,996 research outputs found
Role of the alpha 5 beta 1 integrin receptor in the proliferative response of quiescent human melanoma cells to fibronectin.
No full textThe possible mitogenic activity of fibronectin (FN) in human primary and metastatic melanoma lines and clones and the involvement of integrins in mediating this effect were evaluated. Quiescent human melanoma cells cultured in serum-free medium proliferated in a dose- and time-dependent fashion to immobilized FN as indicated by [H-3]thymidine incorporation, increment of cell number, and cell cycle analysis. This response to FN was observed with tumor clones isolated from a subcutaneous metastasis and with primary or metastatic melanomas from different patients, but only when tumor cells expressed the alpha-5 subunit of the FN receptor (i.e., VLA-5). Proliferation to FN by a primary tumor (Me4405) expressing all FN receptors and by a tumor clone (2/60) lacking only the alpha-4 subunit was inhibited by monoclonal antibodies to the alpha-5 and beta-1 but not by monoclonal antibodies to other subunits of FN receptors. Mapping of FN regions responsible for the proliferative signal was performed by stimulating melanoma cells with different FN proteolytic fragments and indicated that a significant mitogenic signal was provided by the M(r) 120,000 alpha-chymotrypsin fragment containing the Arg-Gly-Asp sequence. The proliferation of melanoma cells to FN and to FN fragments was also significantly inhibited by peptides containing the Arg-Gly-Asp sequence. These data indicate that FN can stimulate the proliferation of quiescent melanoma cells and that integrins as alpha-5-beta-1 are involved in the response of tumor cells to this extracellular matrix protein
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
Monocyte-derived dendritic cells and monocytes migrate to HIV-Tat RGD and basic peptides
No full textDispelling 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
Mitogenic activity of laminin on human melanoma and melanocytes: different signal requirements and role of beta 1 integrins.
No full textThe possible mitogenic activity of laminin (LN) on normal and neoplastic cells of the melanocyte Lineage was tested by culturing growth-arrested human melanoma cells and neonatal foreskin melanocytes on LN. Serum-deprived, quiescent melanoma cells proliferated, in serum-free medium, in a dose-dependent fashion to immobilized LN as determined by [H-3]thymidine incorporation, cell cycle analysis, and change in cell number. The mitogenic activity of LN on melanoma cells was not mediated through autocrine release of growth factors and was observed with primary or metastatic melanoma cells and with clones isolated from the same metastasis but only on cells expressing very late antigen (VLA)-3 and VLA-6 laminin receptors. Proliferation of melanoma cells to LN was significantly inhibited by a mAb to the beta 1 subunit of VLA integrins and by a combination of mAbs to the alpha subunits of VLA-3 and VLA-6. By contrast, LN did not act as a mitogen on human melanocytes expressing VLA-3 and VLA-6 and cultured in serum-free medium. However, a costimulatory activity of immobilized LN for proliferation of melanocytes was observed in the presence of a second signal provided by a set of different growth factors. The costimulatory activity of LN on melanocytes could be significantly inhibited by mAbs directed to the alpha and beta chain of VLA-6 but not to VLA-3. These data suggest that LN itself, and not growth factors possibly associated with it, can exert a mitogenic activity on quiescent human melanoma cells and that a change in the signal requirements for response to LN occurs upon neoplastic transformation in the melanocyte lineage. Furthermore, beta 1 integrins are differentially involved in the response of the normal and the neoplastic cells to LN, since VLA-3 and VLA-6 cooperate in the proliferation of neoplastic cells, while VLA-6 is relevant for the response of melanocytes
- …
