1,720,955 research outputs found
Evaluating the genotoxic potential of oligonucleotide pharmaceuticals
Get PDFAccording to regulatory guidelines, routine genotoxicity tests are not appropriate for biotechnology derived pharmaceuticals, including oligonucleotide based therapeutics, as they are not expected to interact with genomic DNA. However, reports of oligonucleotides capable of binding duplex DNA in a sequence specific manner to form triple-helix (triplex) or displacement-loop (D-loop) structures that in turn cause mutation have raised concern. The European Medicines Agency (EMA) has questioned the capability of antisense oligonucleotide (ASO) therapeutics to form such structures at genomic DNA.
Additionally, concern has been expressed regarding the fate of chemically modified ASO degradation products (nucleotide analogues). It is well established that non-canonical antiretroviral nucleoside analogues, employed in antiretroviral therapy, result in gross chromosome aberrations following incorporation into genomic DNA.
This study has addressed these concerns by evaluating the genotoxic potential of a triplex forming oligonucleotide (TFO) and a D-loop forming ASO targeting genomic DNA. Furthermore, the incorporation efficiency and genotoxicity of nucleotide analogues derived from ASO degradation was investigated.
Data presented here demonstrate a TFO targeting genomic DNA was not capable of inducing mutation above the detection limit of this assay. However, a biologically active ASO molecule induced sequence specific mutation ~4.4 fold above control in a system where RAD51 protein expression was induced. Additionally, DNA polymerase was capable of incorporating various ASO derived nucleotide analogues into a primed DNA template with reduced efficiency. Treatment with phosphorothioate nucleotide analogue, one of the most common chemical modifications used in ASO design, induced mutation ~100 fold above control.
To conclude, ASO and their putative degradation products appeared to be capable of off-target mutagenesis providing favourable conditions were met. However, as genotoxicity data has been presented for a single ASO and nucleotide analogue, it seems plausible to suggest this work can provide a foundation to test future ASO therapeutics and putative degradation products
Abstract 6: A triple-helix forming oligonucleotide targeting a genomic locus is capable of sequence specific mutagenesis in human lymphoblastoid TK6 cells
No full textAbstract
It has been reported that DNA triplex formation induces mutagenesis as determined using plasmid-based reporter constructs (Wang et al 1996, Science, 271, p802). Triplex mediated mutagenesis has been shown to include point mutations, deletions, small insertions and homologous recombination. To the best of our knowledge, no study has successfully examined the mutagenic potential of a non-conjugated triplex-forming oligonucleotide (TFO) targeting a genomic sequence. In this study, we have designed a TFO that targets the hemizygous hypoxanthine-guanine phosphoribosyltransferase (HPRT) locus, in the human lymphoblastoid TK6 cell line, and assessed mutagenicity through resistance to 6-thioguanine.
Our TFO, TFO27, has been designed to form a triplex with a purine tract in exon 3 of the HPRT gene. Triplex formation at the target motif was shown to occur at nanomolar concentrations, confirmed by Electrophoretic Mobility Shift Assays. A scrambled oligonucleotide, SCR27, failed to form a triplex at the target motif. A range of transfection reagents were evaluated for facilitated delivery of TFO27, and resulted in variable cellular toxicity. Transfection of high concentrations of oligonucleotide, with acceptable levels of cytotoxicity, resulted in HPRT mutation with TFO27 but not SCR27. Similar experiments failed to result in mutation at the non-targeted thymidine kinase (TK) locus, suggesting locus specificity for the mode of action of TFO27. The target specificity and sequence context of these mutagenic events is being determined to establish the mechanism of mutation.
Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 6.</jats:p
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
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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