1,720,958 research outputs found
Isolation of a new class of 'flat' revertants from ras-transformed NIH3T3 cells using cis-4-hydroxy-L-proline
No full textDifferential growth factor expression in transformed mouse NIH‐3T3 cells
No full textThe expression of growth factor‐specific mRNA transcripts and the presence of biologically active growth factors in the conditioned medium and in the cell extracts from mouse NIH‐3T3 cells transformed by different oncogences (Ki‐ras, mos, src, fms, fes, met, and trk), by DNA tumor virus (SV40), or by a chemical carcinogen (N‐nitrosomethylurea) were studied. In contrast to NIH‐3T3 cells or simain virus 40 (SV40)‐transformed 3T3 cells, all the other transformed NIH‐3T3 cell lines express a 4.5 kb transforming growth factor‐α (TGFα)‐specific mRNA transcript and secreted immunoreactive and biologically active TGFα ranging from 100 to 225 ng/108 cell/48 h. In addition, in the transformed cell lines that were secreting elevated levels of biologically active TGFα, there was a 75–95% reduction in the total number of epidermal growth factor receptors on these cells. A 2.6 kb TGFβ mRNA transcript and TGFβ protein in the conditioned medium (30–140ng/108 cells/48h) was also detected in those lines expressing TGFα. Basic fibroblast growth factor‐like activity (11–50 ng/108 cells) was detected in the cell lysates from NIH‐3T3 cells transformed with N‐nitrosomethylurea or with trk, where expression of specific 6.9 and 3.9 kb mRNA transcripts for basic fibroblast growth factor could also be found. B chain (c‐sis) expression of platelet‐derived growth factor was present only in trk‐transformed NIH‐3T3 cells in which specific c‐sis 6.5 and 4.6 kb transcripts were identified. In contrast, platelet‐derived growth factor A chain expression of 2.9 and 2.3 kb transcripts was found in ras‐, met‐, mos‐, and fms‐transformed NIH‐3T3 cells. These results suggest that the expression of different sets of growth factors is controlled in part by structurally distinct groups of transforming genes. Copyright © 1990 Wiley‐Liss, Inc
Effects of ouabain on NIH/3T3 cells transformed with retroviral oncogenes and on human tumor cell lines
No full textTransformation of an established mouse mammary epithelial cell line following transfection with a human transforming growth factor alpha cDNA
No full textDifferential growth sensitivity to 4-cis-hydroxy-L-proline of transformed rodent cell lines
Full text linkThe effect of 4-cis-hydroxy-L-proline (CHP), a proline analogue, on the anchorage-dependent and -independent growth of several transformed rodent cell lines was studied. Mouse NIH-3T3 fibroblasts transformed by a variety of different oncogenes (Ki-ras, mos, src, fms, fes, met, and trk) by a DNA tumor virus (SV40) or by a chemical carcinogen (N-methylnitrosourea) were all found to be more sensitive (50% inhibitory dose, 20 to 55 micrograms/ml) to the dose-dependent inhibitory effects of CHP on growth in monolayer culture than were NIH-3T3 cells (50% inhibitory dose, 120 micrograms/ml). CHP was generally found to be even more effective in inhibiting the growth of these transformed cells as colonies in soft agar than in monolayer cultures. In addition, rat embryo fibroblasts (CREF) and normal rat kidney fibroblasts (NRK) after transformation with a Ki-ras oncogene exhibit a similar increase in their sensitivity to CHP-induced growth inhibition. Treatment of NRK cells with transforming growth factor alpha (TGF-alpha) and beta (TGF-beta), which reversibly induces phenotypic transformation of these cells, increases their sensitivity to CHP to a level comparable with that observed in Ki-ras-transformed NRK cells (K-NRK). The growth inhibitory effects of CHP are reversible, since removal of CHP results in a normal resumption of cell growth. CHP uptake occurs primarily through the Na+- and energy-dependent neutral amino acid transport A system, which is 6- to 7-fold more elevated in K-NRK cells compared with NRK cells. Treatment of NRK cells with TGF-alpha and/or -beta increases the uptake of [3H]methylaminoisobutyric acid on the A system to a level that is similar to that found in K-NRK cells. The functions of the Na+/K+ and Na+/H+ exchange systems are apparently necessary for the enhanced A system activity, since ouabain and amiloride can inhibit the uptake of [3H]methylaminoisobutyric acid in K-NRK cells and in NRK cells treated with TGF-alpha and/or -beta. The activity of the A system is specifically increased in K-NRK and in TGF-alpha- and/or -beta-treated NRK cells, since the other two major neutral amino acid uptake systems, the ASC and the L systems, and the Ly+ system for basic amino acid uptake show no apparent changes in their activity in NRK cells after treatment with TGF-alpha and/or -beta or in these cells after transformation with the Ki-ras oncogene. These results suggest that the differential growth sensitivity to CHP of transformed rodent cells and of normal fibroblasts treated with TGF-alpha and/or -beta is due in part to an elevated uptake of this amino acid analogue on the neutral amino acid transport A system
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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