1,720,973 research outputs found
Tumor formation by a murine macrophage cell line immortalized in vitro by v-raf and v-myc oncogenes
No full textMurine bone marrow cells immortalized in vitro by the J2 recombinant retrovirus bearing the v-raf and v-myc oncogenes have the functional and phenotypic characteristics of macrophages. The present study was designed to determine whether these cells are tumorigenic in athymic or euthymic mice. One cloned cell line (GG2EE), that had been previously derived and characterized was used for this purpose. The results demonstrated that GG2EE cells were tumorigenic in allogeneic athymic BALB/c mice at doses of 1×104 to 1×107 cells per mouse regardless of the route administration. All mice utlimately died of progressive tumor growth. Conversely, the GG2EE cells were nontumorigenic or transiently tumorigenic in syngeneic euthymic C3H/HeJ mice. Further studies in BALB/c athymic mice demonstrated that the GG2EE cells were directly tumorigenic since ascites tumors (GG2EE-V) that developed expressed the H-2k surface phenotype of the injected GG2EE cells, excluding the possibility that the J2 virus constitutively produced by GG2EE cells caused in vivo transformation and therefore tumors of host cell origin. The in vivo passaged cells continued to express the M1/69, MAC-1, MAC-2, F4/80, Fc receptor and Ly5.1 antigens characterically expressed on the parental line. Biological properties including interferon-γ-induced Ia expression, phagocytosis, and activation for cytotoxicity were also retained following in vivo passage. These results demonstrated that J2 virus-immortalized GG2EE cells were directly tumorigenic in athymic mice in vivo and that the macrophage phenotype was maintained in these neoplastic cells. These observations suggest that this tumor model may be valuable for the study of macrophage function as well as therapeutic approaches to oncogen-expressing retrovirus-induced tumors. © 1988 Springer-Verlag
Inhibition of proliferation of retrovirus-immortalized macrophages by LPS and IFN-γ: Possible autocrine down-regulation of cell growth by induction of IL1 and TNF
No full textThe GG2EE macrophage tumor cell line was previously established by immortalization of C3H/HeJ mouse bone marrow cells with the J2 retrovirus which contains the v-myc and v-raf oncogenes. Studies on the control of GGZEE cell proliferation in vitro have recently been performed. We observed that the combination of 5-25 U/ml recombinant mouse interferon-γ (rmIFN-γ) plus 0.03 - 0.3 μg/ml lipopolysaccharide (LPS) markedly inhibited the proliferation of GG2EE cells (by >95%)in vitro, while either agent alone inhibited only by <40% and 0-10%, respectively. Subsequent studies established that biologically active ILI-like (2-4 U/ml) and TNF α-like (50-100 U/ml) activities were released into the supernatants of LPS-treated GG2EE cells. The combination of IFN-γ + LPS induced more (6-8 U/ml) ILI release. These results suggested that the inhibition of proliferation of GG2EE cells by IFN-γ + LPS could have been mediated in part by cytokines produced by the cells themselves. rhIL1 α at a concentration of 10 U/ml inhibited GG2EE proliferation by 25-30%, while rmIFN-γ (25 U/ml) + rhIL1 α (10 U/ml) inhibited proliferation by 98%. Thus, 10 U/ml rhIL1 α could completely replace LPS in the LPS + rmIFN-γ combination. Further, the combination of low doses of rhIL1 α (0.1 to 1 U/ml) plus rmTNF α (250 U/ml), which together inhibited proliferation by <20% synergized with doses of 5 to 25 U/ml rmIFN-γ to inhibit proliferation of GG2EE cells by 98-99%. These results suggest that cytokines produced by the cells themselves can synergize with rmIFN-γ to inhibit the oncogene-driven proliferation of GG2EE cells. © 1992 Kluwer Academic Publishers
Potent Activation of Mouse Macrophages by Recombinant lnterferon-γ
No full textThe ability of recombinant interferon-γ (IFN-γ ) to activate mouse macrophages was investigated. The use of recombinant IFN-γ has the advantage of being devoid of contaminating lymphokines. Two preparations of IFN-7 were utilized, one which was not glycosylated and which was highly purified from Escherichia coli and another which was glycosylated and which was from transfected COS-7 monkey cells. Both preparations of recombinant IFN-γ activated murine macrophages to kill lymphoma and melanoma tumor targets, suggesting that glycosylate of the protein or the presence of other mammalian proteins is not essential for activation. Significant levels of cytolytic activity were induced from IFN-γ (1 to 10 units/ml). This activity was undiminished by treatment of the IFN-γ preparations with poly-mixin B at doses which neutralized endotoxin (50 μ g/ml). Similarly, IFN-γ, at low concentrations, induced an inhibition of migration by macrophages. Based on antiviral activity, IFN-γ was shown to be 100 to 1000 times more potent than was IFN-β as a macrophage-activating agent. Taken together, these results demonstrate that murine IFN-γ is a macrophage-activating factor which is effective at physiological concentrations. Of particular interest is the observation that the nonglycosylated E. coli-derived IFN-γ is active and therefore may be of value for therapeutic studies, since it can be easily produced in large amounts. © 1984, American Association for Cancer Research. 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
Gradual Loss of T-Helper-1 Population in Spleen of Mice During Progressive Tumor Growth.
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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