1,721,016 research outputs found
Motility analysis of pancreatic adenocarcinoma cells reveals a role for the atypical zeta isoform of protein kinase C in cancer cell movement
No full textThe acquisition of an invasive and metastatic phenotype is accompanied by profound alterations of intracellular mechanisms controlling cell movement. Analysis of quantitative parameters of cell motility in cancer cells may help in the identification of intracellular signaling events determining invasion and metastasis. Here we developed a novel procedure of quantification of cell motility based on time-lapse video microscopy and digital image analysis. Three kinetic parameters, including area change, plasma membrane remodeling, and speed of linear movement, are quantified and combined in one single, time-normalized value we defined motility score (MS). Through calculation of the MS for various human pancreatic adenocarcinoma cell subclones, we identified clones characterized by low or high spontaneous motility in vitro. Analysis of the signaling mechanisms involved in the regulation of pancreatic adenocarcinoma cell motility showed that the atypical zeta isozyme of the serine-threonine protein kinase C (PKC) plays a critical role in maintaining a high MS in motile subclones, as demonstrated by the inhibitory effect of cell permeable peptides with sequence corresponding to the pseudosubstrate inhibitory region of the atypical zeta PKC. Other PKC isozymes, either classic or novel, seem not involved. Furthermore, biochemical analysis showed that in motile cells, zeta PKC is constitutively associated with the plasma membrane, whereas in nonmotile cells, zeta PKC is totally excluded from the plasma membrane. These data suggest that the disregulation of the function of atypical zeta PKC might be involved in the acquisition of an invasive and metastatic phenotype in pancreatic adenocarcinoma cells
Chemoattractant induces LFA-1 associated PI 3K activity and cell migration that are dependent on Fyn signaling.
No full textThe activation state of integrins on leukocytes is tightly controlled by the association of intracellular molecules to the cytoplasmic domain of the integrin. To identify signaling intermediates involved in chemoattractant receptor-induced integrin activation, we analyzed the ability of LFA-1 integrin to associate with members of Src tyrosine kinase and phosphatidylinositol 3Kinase (PI 3K) families following fMLP stimulation of a lymphoid T cell line stably expressing the fMLP receptor (fPR). fMLP- induced cell activation resulted in a rapid increase of integrin-associated PI 3Kinase activity in G protein and Src kinase dependent manner. We show, upon fMLP- stimulation, a rapid and transient association of the Src tyrosine kinase Fyn with LFA-1. Also, by transiently expressing mutant forms of this kinase, we demonstrated that Fyn is required for the integrin associated PI 3K activity. Furthermore, overexpression of the mutant form of Fyn resulted in a significant impairment of fMLP- induced cell migration through ICAM-1-coated filters, while ICAM-1 independent migration was not affected. Our observations indicate that chemoattractant receptor engagement induces Fyn-dependent PI 3K activation in association with LFA-1 and suggests that Fyn is necessary to initiate and/or to regulate chemoattractant-mediated LFA-1 activation to promote directional migration
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
Molecular mechanisms involved in lymphocyte recruitment in inflamed brain microvessels: critical roles for P-selectin glycoprotein ligand-1 and heterotrimeric G(i)-linked receptors.
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
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