1,720,982 research outputs found
Mycobacteria and dendritic cell differentiation: Escape or control of immunity
No full textHuman monocytes can differentiate into dendritic cells (DC) according to the nature of environmental signals. Pathogenic mycobacteria have been demonstrated interfere with this process to generate a not fully competent DC population. This mechanism is not common to non-pathogenic mycobacteria and could be correlated with bacterial virulence. However, it could represents a new mechanism of immune escape by persistent pathogens or a control mechanism of immune system to preserve the life of the organ against persistent infections. © 2005 Elsevier B.V. All rights reserved
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
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
Modulation of phenotype and function of human CD4+CD25+ T regulatory lymphocytes mediated by cAMP-elevating agents
No full textWe have shown that cholera toxin (CT) and other cyclic AMP (cAMP)-elevating agents induce upregulation of the inhibitory molecule CTLA-4 in human resting CD4+ T lymphocytes, which following the treatment acquired suppressive functions. In this study, we evaluated the effect of cAMP-elevating agents on human CD4+CD25+ T cells, which include the T regulatory cells (Tregs) that play a pivotal role in the maintenance of immunological tolerance. We found that cAMP-elevating agents induce upregulation of CTLA-4 in CD4+CD25- and further enhance its expression in CD4+CD25+ T cells. We observed an increase of two isoforms of mRNA coding for the membrane and the soluble CTLA-4 molecules, suggesting that the regulation of CTLA-4 expression by cAMP is at the transcriptional level. In addition, we found that the increase of cAMP in CD4+CD25+ T cells converts the CD4+CD25+Foxp3- T cells in CD4+CD25+Foxp3+ T cells, whereas the increase of cAMP in CD4+CD25- T cells did not upregulate Foxp3 in the absence of activation stimuli. To investigate the function of these cells, we performed an in vitro suppression assay by culturing CD4+CD25+ T cells untreated or pre-treated with CT with anti-CD3 mAbs-stimulated autologous peripheral blood mononuclear cell. We found that CT enhances the inhibitory function of CD4+CD25+ T cells, CD4+, and CD8+ T cell proliferation and IFNγ production are strongly inhibited by CD4+CD25+ T cells pre-treated with cAMP-elevating agents. Furthermore, we found that CD4+CD25+ T lymphocytes pre-treated with cAMP-elevating agents induce the upregulation of CD80 and CD86 co-stimulatory molecules on immature dendritic cells (DCs) in the absence of antigenic stimulation, however without leading to full DC maturation. These data show that the increase of intracellular cAMP modulates the phenotype and function of human CD4+CD25+ T cells
Inhibition of T cell proliferation by cholera toxin involves the modulation of costimulatory molecules CTLA-4 and CD28
No full textCholera toxin (CT) is known to inhibit the proliferation of murine and human T lymphocytes. In this study we have analysed the mechanisms underlying the inhibitory effect of CT on subpopulations of human CD4+ and CD8+ T lymphocytes. We show that CT dramatically prevents the activation of resting T lymphocytes, whereas it has a minor effect on cells that have been previously activated. Analysis of DNA content of the CT-treated T cells showed an arrest in the G0/G1 phase and this correlated with high expression of the cyclin-dependent kinase inhibitor p27kip. Moreover, we show that CT up-regulates the expression of the inhibitory molecule CTLA-4 in naïve, effector and memory resting CD4+ T cells and in resting CD8+ T lymphocytes. The regulation of CTLA-4 expression by CT is at the transcriptional level. Indeed, in cells treated with CT we observed an increase of two mRNA variants coding for the membrane and the soluble CTLA-4 molecules. In parallel with the up-regulation of the inhibitory CTLA-4, CT down-modulates the costimulatory molecule CD28 on CD4+ and CD8+ resting T cells. The increased expression of CTLA-4 played a role in controlling T cell activation and function as blocking anti-CTLA-4 F(ab′)2 mAbs partially inhibited anti-CD3 mAbs induced proliferation. These findings show that the inhibition of T cell proliferation by CT affects early stages of the T cell activation and involves the modulation of costimulatory molecules CTLA-4 and CD28 on resting T cells. © 2007 Elsevier B.V. All rights reserved
Cyclic adenosine 5′-monophosphate and calcium induce CD152 (CTLA-4) up-regulation in resting CD4+ T lymphocytes
No full textThe CTLA-4 (CD152) molecule is up-regulated upon T cell activation and proliferation, and plays a critical role in the inhibition of immune responses. We show in this study that cAMP induces up-regulation of CD152 in human CD4+ T lymphocytes. This effect occurs in the absence of the up-regulation of CD69 and CD25 activation markers and T cell proliferation. In addition, we found that the Ca2+ ionophore ionomycin also up-regulates CD152, and that the combination of a cAMP analog or cAMP inducers with ionomycin further enhances the expression of CD152 in resting CD4+ T lymphocytes. However, cyclosporin A, which inhibits Ca2+/calcineurin signaling pathway, fully prevented the ionomycin- but not the cAMP-induced up-regulation of CD152. The effects of cAMP and ionomycin involve increase of both CD152 mRNA transcripts, coding for the membrane and the soluble forms of CD152. Furthermore, we show that CD152 molecules are translocated to the membrane and are functional, as their engagement by specific mAbs prevented NF-κB activation by anti-CD3/CD28 stimulation. These findings demonstrate that at least two novel signal pathways regulate CTLA-4 gene expression and CD152 molecule up-regulation in human CD4+ T lymphocytes, in the absence of full T cell activation
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