1,720,972 research outputs found
P53-DEPENDENT AND P53-INDEPENDENT ACTIVATION OF APOPTOSIS IN MAMMARY EPITHELIAL-CELLS REVEALS A SURVIVAL FUNCTION OF EGF AND INSULIN
No full textThe p53 tumor suppressor protein has been implicated as a mediator of programmed cell death (PCD). A series of nontransformed mammary epithelial cell (MEG) lines were used to correlate p53 function with activation of PCD. Treatment of MECs expressing mutant, inactive, or no p53 with DNA-damaging agents did not induce apoptosis. Upon introduction of temperature-sensitive p53 into HC11 cells, which lack wild-type (wt) p53, PCD was observed after mitomycin treatment at 32 degrees, when the ts p53 protein is in wt conformation. Thus, wt p53 mediates activation of PCD in response to mitomycin in HC11 cells. Treatment of the MCF10-A cells, which express wt p53, with various DNAdamaging agents led to nuclear accumulation of p53. Only mitomycin treatment led to an increase in the number of apoptotic nuclei. ErbB-2-transformed MCF10-A cells responded to mitomycin, cisplatin, and 5-Fl-uracil, suggesting that signaling from activated ErbB-2 enhances the cells ability to respond to DNA damage. A combination of high cell density and serum-free medium induces apoptosis in all MECs tested, irrespective of their p53 status. Under these conditions, EGF or insulin act as survival factors in preventing PCD. These data might elucidate some aspects of breast involution and tumorigenesis
In mammary epithelial cells p53-mediated apoptosis in response to DNA damage is dependent on the agent and can be influenced by growth factors
No full textIn mammary epithelial cells there are al least two pathways which promote apoptosis: one is activated by DNA damage and requires p53, the other which is p53-independent is induced in confluent cultures by growth factor withdrawal. In this publication we have examined p53-mediated, DNA damage-induced apoptosis in MCF10A human mammary epithelial cells which express wild-type p53. In cells treated with the DNA damage-inducing agents, mitomycin C, 5-Fluorouracil, cisplatin and u.v. irradiation, there is an increase in the levels of the p53 protein and the p21(CIP1/WAF1) cyclin-dependent kinase inhibitor. However, the ability of the agents to induce a cell cycle arrest or an apoptotic response varied considerably. Treatment with u.v. induced the highest level of apoptosis without an apparent effect on the cell cycle, whereas 5-Fluorouracil-treated cells showed a G1 arrest with no apoptosis. Mitomycin C treatment led to a moderate G1 arrest and a moderate level of apoptosis which could be increased in growth factor-starved cells. MCF10A cells expressed high levels of Bax, a death-promoting member of the Bcl-2 family. Bax expression was not influenced by treatments which promoted apoptosis. The results showed that the response of mammary epithelial cells to DNA damage is complex, dependent upon the inducing agent and can be influenced by culture conditions
Expression of int-2 mRNA in human tumors amplified at the int-2 locus.
No full textGene amplification is a relatively frequent event in human malignant tumors and is believed to have an important function in neoplastic transformation and tumor progression. Our attention has been focused on the amplification and the expression of the int-2 gene for several reasons: (1) In the mouse mammary tumorigenesis int-2 is frequently activated by MMTV proviral integration. (2) The human homolog of int-2, located on chromosome 11q13, is frequently amplified in human primary tumors and is comprised in an amplification unit encompassing the hst gene, which is often coamplified; the amplification at the 11q13 locus in breast carcinomas correlates with a poor outcome of the disease. (3) int-2 and hst belong to the basic FGF gene family. All these observations raise the possibility that the human int-2 gene plays an active role in the neoplastic process, but this will prove to be true only if int-2 is expressed in human tumors. In the present study we used RNA:RNA in situ hybridization and Northern blot analysis to show that int-2 gene is expressed in a number of human carcinomas amplified at the same locus
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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