1,720,981 research outputs found
Epidermal growth factor induces, in the ELα4-2 cell line, herpes simplex virus-1 α4 gene transcription in the absence of the viral trans-activator VP16
No full textWe have constructed a fibroblast cell line (ELα4-2) which constitutively expresses the α4 gene of herpes simplex virus type 1. We studied the induction of the α4 gene, in the absence of the viral activator VP16, by stimulating ELα4-2 cells with different growth factors. Here we report that a rapid, transient induction of the α4 gene occurs only when ELα4-2 fibroblasts are stimulated with purified epidermal growth factor (EGF). Such an induction does not require de novo protein synthesis. The role of cellular factors on the EGF-mediated induction of the α4 gene has been analyzed by gel mobility shift assays using nuclear extracts from ELα4-2 cells stimulated or not with EGF. The results obtained show that two factors bind to TAATGARAT (R = purine) regardless of EGF-stimulation. We conclude that a mechanism, different from the one involving VP16, is responsible for α4 gene activation in ELα4-2 cells and that the DNA-protein architecture is maintained at the TAATGARAT regulatory site regardless of changes in the transcriptional state induced by EGF. © 1991
T Lymphocytes transduced with a lentiviral vector expressing F12-Vif are protected from HIV-1 infection in an APOBEC3G-independent manner
Full text linkThe viral infectivity factor (Vif) is an essential component of the HIV-1 infectious cycle. Vif counteracts the action of the cytidine deaminase APOBEC3G (AP3G), which confers nonimmune antiviral defense against HIV-1 to T lymphocytes. Disabling or interfering with the function of Vif could represent an alternative therapeutic approach to AIDS. We have expressed a natural mutant of Vif, F12-Vif, in a VSV-G-pseudotyped lentiviral vector under the Tat-inducible control of the HIV-1 LTR. Conditional expression of F12-Vif prevents replication and spreading of both CXCR4 and CCR5 strains of HIV-1 in human primary T lymphocyte and T cell lines. T cells transduced with F12-Vif release few HIV-1 virions and with reduced infectivity. Several lines of evidence indicate that HIV-1 interference requires the presence of both wild-type and F12-Vif proteins, suggesting a dominant-negative feature of the F12-Vif mutant. Surprisingly, however, the F12-Vif-mediated inhibition does not depend on the reestablishment of the AP3G function
Double doors and gatekeepers: HIV co-receptors and chemokines
No full textThe identification of CD4 as the HIV receptor immediately triggered a search for the development of novel therapeutic agents aimed at blocking receptor binding. Initial experimental approaches to this problem failed, but led to the observation that one or more other receptors for HIV, or co-receptors, must be involved in the entry of the virus in cells. In 1996 evidence was reported of a second viral receptor, already known under several names and renamed "fusin." Shortly thereafter the CCR5 molecule was identified as a cc-receptor for the second type of HIV strain. This second discovery left no doubts: the second receptor for the virus encompassed at least two members of the chemokine receptor family. The identification of these co-receptors has led to several important new observations about HIV, including the fact that chemokines are potent in vitro inhibitors of viral replication, at least in T lymphocytes; however, there is still little information on their role lit vivo. Nevertheless, unlike chemokines, the role of chemokine receptors in vivo has already emerged as being of substantial importance. (C) 1998 Prous Science. All rights reserved
High affinity receptor for IgG (Fc gamma RI/CD64) gene and STAT protein binding to the IFN-gamma response region (GRR) are regulated differentially in human neutrophils and monocytes by IL-10
No full textSince IL-10 has been shown to up-regulate the expression of the high affinity receptor for IgG (FcgammaRI/CD64) in human monocytes, we examined whether the cytokine exerts a similar action toward polymorphonuclear neutrophils (PMN). Unexpectedly, we found that in neutrophils, IL-10 failed to induce either the mRNA accumulation or the surface expression of FcgammaRI. Consistent with these findings, stimulation of PMN with IFN-gamma, but not with IL-10, resulted in the induction of specific DNA-binding activities to the IFN-gamma response region (GRR), a regulatory element located in the FcgammaRI gene promoter, required for transcriptional activation. In electrophoretic mobility shift assays (EMSAs), we confirmed that in PBMC, IL-10 induces the binding to the GRR of both STAT1 and STAT3, two members of the STAT family. In neutrophils, however, these activators did not bind to the GRR in response to IL-10, despite the fact that both STAT1 and STAT3 are expressed in these cells. On the other hand, IFN-gamm
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
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