1,721,092 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Investigation of apoptosis-related gene expression in multi-drug resistant cells
Get PDFThe RNase protection assay (RPA) was used to identify changes in gene expression accompanying alterations in drug resistance levels in lung carcinoma cells. Based on this analysis, mcl-1 and bax were selected for transfection into drug sensitive cells to establish whether or not their expression influences drug resistance levels. The RPA was also used to investigate alterations in expression of bcl family genes as a consequence of transfection of a bcl-xL ribozyme.
Previous research in this laboratory, as well as results of the RPA analysis, indicated that caspase-3 levels were reduced in more resistant cell lines. To investigate the role of caspase-3 in drug resistant cells, the first reported ribozyme to human caspase-3 was designed and transfected into a drug-resistant variant (DLKP-A5F) of a human lung carcinoma cell line (DLKP). By both in vitro cleavage and stable and transient transfection in drug resistant DLKP-A5F cells, this ribozyme was shown to be effective at down-regulating human caspase-3 mRNA and protein levels. Initial results in stable transfectants indicated an increase in drug resistance, but on repeated subculture, these resistance levels reverted back to those of parent cells. Analysis of the multi-drug resistance protein, P-gp, revealed that its level had also decreased in some of the clones. These results indicate the importance of analysing P-gp levels in transfection studies where drug resistance is being monitored and suggest the possibility that caspase-3 expression may somehow regulate P-gp protein level.
DNA microarray technology was used to investigate differences in gene expression between two resistant variants (one high-level, one low-level) of doxorubicin-treated DLKP cells. Results indicated changes in the gene expression of some ABC transporter proteins, multi-drug resistance gene (mdr-1), apoptosis-related genes (galectin-1, apoptosis-associated protein kinase), calpain-1, retinoic acid receptor-a as well as metastases-related genes.
Finally, the expression of apoptosis-related genes was examined in a panel of archival breast tumour biopsies. The expression of these genes (bcl-1, bax, mcl-1 and bag-1) was correlated with clinicopathological parameters with the aim of identifying their prognostic significance. Bcl-2 correlated with ER status, bag-1 expression and five-year relapse-free and overall survival. Bax expression did not associate with any other parameter. Mcl-1 correlated with tumour grade and had borderline significance with lymph node status and survivin 83 expression
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
In vitro models of human lung cell differentiation
Get PDFPrevious studies in this laboratory have demonstrated that BrdU induces differentiation in the lung epithelial cell lines DLKP (derived from a poorly differentiated carcinoma of the lung) and A549 (derived from an adenocarcinoma of the lung). This differentiation involves the induction of epithelial specific proteins, e.g. cytokeratins-8 and -18, and epithelial related adhesion molecules e.g. (X2P1 integrin. This thesis investigated the effects BrdU has on the expression of Ep-CAM, a non-calcium dependent, homophilic cell-cell adhesion protein, in these cell lines. BrdU treatment induced Ep-CAM protein expression in DLKP after 7 days, with this induction reaching a plateau after 14 days of 10(iM BrdU treatment. Similarly, in A549, Ep-CAM was induced following 7 days of BrdU treatment and the level of induction also plateaued after 14 days of exposure to 10(.iM BrdU. RT-PCR analysis revealed that the effect of BrdU on Ep-CAM expression appears to be at the post-transcriptional/translational level, with no increase in mRNA levels compared to significant increase in protein levels in both cell lines.
Ep-CAM is believed to interfere with the functioning of the Ca2+-dependent cell-cell adhesion molecule E-cadherin, by causing alterations in focal adhesion proteins. Analysis of two these proteins, a-actinin and a-catenin, showed that BrdU down-regulated their expression following Ep-CAM induction.
RT-PCR analysis of the Ep-CAM homologue GA733-1 revealed that, following BrdU treatment, mRNA expression is induced in DLKP. However, no induction is observed in A549.
The ability of other halogenated thymidine analogues to induce differentiation was also investigated. Three halogenated thymidine analogues were selected, each possessing a different mechanism of biological activity, CdU (which incorporates into DNA), 5,5'- FdU (which inhibits DNA synthesis) and 5-BUr (which incorporates into RNA). The ability of CdU to induce the expression of cytokeratin-8, cytokeratin-18, cytokeratin-19, Ep-CAM and (31 -integrin was demonstrated in both A549 and DLKP. RT-PCR analysis of A549 revealed that although the protein expression was induced, the mRNA level remained unchanged indicating that CdU was altering expression at a posttranscriptional/ translational level. A significant up-regulation of cytokeratin-8, cytokeratin-18, cytokeratin-19, Ep-CAM and |31 integrin also occurred in DLKP and A549 following 5,5'-FdU treatment. Analysis of mRNA levels following treatment with 5,5'-FdU indicated that expression was being altered at a post-transcriptional/translational level. Treatment of DLKP and A549 with 5-BUr did not produce any obvious alterations in protein expression or mRNA levels.
To develop models reflecting in vivo differentiation, DLKP and A549 were grown in a hormone supplemented medium (HSM) which contained a number of physiologically relevant factors e.g. oestrogen and insulin. Growth in this medium induced expression of cytokeratin-8, cytokeratin-18, cytokeratin-19, and Ep-CAM in DLKP and A549. Experiments to identify the importance o f specific components in HSM revealed that the deletion of hydrocortisone, and cholera toxin from HSM cause an increase in induction of cytokeratin-19 and Ep-CAM. In contrast the removal of insulin from HSM, reduced the ability to induce expression of cytokeratin-19 and Ep-CAM in A549.
To further develop in vitro models reflecting in vivo differentiation, methods were established to generate primary cultures of lung tumour cells and normal lung epithelial cells. The assessment of a variety of methods for the isolation of lung carcinoma cells from lung tumour samples did not reveal any advantages between the methods. Preliminary studies on isolated normal rat type II pneumocytes revealed morphological and antigenic changes during in vitro cultivation. These changes were consistent with the terminal differentiation of type II pneumocytes into type I pneumocytes. During the isolation of lung tumour cells cultures of fibroblasts were often established and these expressed the unusual feature of cytokeratin protein expression, which is usually epithelial- specific
Investigation of substitutes for foetal calf serum in animal cell culture media
Get PDFThe purpose of this thesis was to develop a serum-free medium which would support the growth of a human tumour cell line, RPMI 2650. Serum is used almost universally as a medium supplement to support growth of cells in culture, but investigators in the field have long recognised the problems associated with the undefined, complex and variable composition of serum whereas serum-free media permit growth of cells in a precisely-defined environment.
In order to gain experience in the techniques used to grow cells in culture in the absence of serum, initial work was carried out on a canine kidney cell line (MDCK), for which a serum-free medium had already been developed. Growth of RPMI 2650 was initially examined in reduced serum conditions at clonal cell densities and the effect of various growth factors, hormones and other nutritional factors was examined. Significant growth stimulation was observed due to the addition of a number of factors (transferrin, insulin, EGF and selenium).
Growth occurred in dishes precoated with DEAE dextran in the absence of any serum supplement following addition of medium containing six components (transferrin, insulin, epidermal growth factor, selenium, ascorbic acid and a commerciallyavailable amino acid mixture, MEM non-essential amino acids)
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