1,720,976 research outputs found
Role of mismatch repair in the induction of chromosomal aberrations and sister chromatid exchanges in cells treated with different chemotherapeutic agents
No full textPurpose: The mismatch repair (MMR) system plays a major role in mediating the cytotoxicity and clastogenicity of agents generating O 6-methylguanine in DNA. Loss of MMR has also been associated with tumor cell resistance to the cytotoxic effects of 6-thio-guanine and cisplatin and with hypersensitivity to N-(2-chloroethyl)-N′ -cyclohexyl-N-nitrosourea (CCNU). The aim of the present investigation was to elucidate the role played by the MMR system in the generation of chromosomal damage in cells exposed to 6-thioguanine, cisplatin or CCNU. Methods: The MMR-proficient cell lines TK6 and HCT116/3-6, and their MMR-deficient counterparts MT1 and HCT116, were treated with 6-thioguanine, cisplatin or CCNU, and analyzed for cell growth inhibition and chromosomal damage. As a control, similar experiments were performed with the methylating agent temozolomide. Results: Cytotoxicity, chromosomal aberrations and sister chromatid exchanges induced by 6-thioguanine and temozolomide were significantly reduced in the MMR-deficient cell lines with respect to their MMR-proficient counterparts. In contrast, although conferring some protection against cytotoxicity, the loss of MMR did not affect cytogenetic damage induced by cisplatin. CCNU produced comparable levels of cytotoxicity, chromosomal aberrations and sister chromatid exchanges in both MMR-proficient and MMR-deficient cell lines. Conclusions: The MMR system is involved in the generation of chromosomal damage in cells exposed to 6-thioguanine. The system does not play a relevant role in the generation of chromosomal damage in cells treated with CDDP and does not confer protection against the clastogenic effects of CCNU, at least in the cell lines investigated
Effects of diheptyldiselenide (DDS) on human tumor cell lines and on peripheral blood mononuclear cells
No full textIn vitro effects of graded concentrations of diheptyldiselenide (DDS) on human tumor cell proliferation, and on the poliferative responses and immunological functions of peripheral blood mononuclear cells (MNC) were investigated. The agent significantly decreased tumor cell proliferation in a dose and time dependent manner. Proliferative responses of MNC to phytohemagglutinin (PHA) and interleukin-2 (IL-2) were also significantly depressed when MNCs were exposed to DDS at the onset of the culture. Pretreatment of MNCs with DDS (250 mu M for 18 h) led to a significant increase in NK activity only in MNC samples showing very limited baseline NK function. On the other hand, generation of LAK cells was significantly inhibited by DDS. However, when the agent was added to the effector and target cell mixture during the 4 h Cr-51 release cytotoxicity assay, no influence was found on NK and LAK-mediated target cell lysis. These studies show that high concentrations of DDS inhibit tumor cell proliferation and could also impair certain proliferative-dependent immune functions, without directly affecting cell-mediated cytolytic activity of effector cells
Role of mismatch repair in the induction of chromosomal aberrations and sister chromatid exchanges in cells treated with different chemotherapeutic agents
No full textThe mismatch repair (MMR) system plays a major role in mediating the cytotoxicity and clastogenicity of agents generating O(6)-methylguanine in DNA. Loss of MMR has also been associated with tumor cell resistance to the cytotoxic effects of 6-thioguanine and cisplatin and with hypersensitivity to N-(2-chloroethyl)- N'-cyclohexyl- N-nitrosourea (CCNU). The aim of the present investigation was to elucidate the role played by the MMR system in the generation of chromosomal damage in cells exposed to 6-thioguanine, cisplatin or CCNU
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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