1,720,976 research outputs found
Mechanisms, obstacles and opportunities of artificially enveloped adenovirus for safe and efficient gene delivery
Full text linkGene therapy with human adenovirus type S (AdS) has been extensively explored for the treatment of diseases resistant to traditional therapies. Following intravenous administration, Ad is rapidly cleared from systemic blood circulation with a half life of 2 minutes, and more than 99 % of the injected dose is sequestered in the liver. The resulting innate and adaptive immune responses dramatically affect the kinetics and toxicity profile of the vector. These issues currently restrict the use of Ad-based vectors, particularly for clinical gene therapy protocols that involve systemic administration. We propose that such limitations can be improved by engineering artificial lipid envelopes around Ad. We previously designed a variety of artificial lipid bilayer envelopes around the viral capsid. Zwitterionic and cationic lipid formulations can efficiently envelop Ad, however this resulted in a significant reduction of gene expression in vitro due to the inadequate escape of the enveloped virus from the endosomal compartment. In this thesis, pH-sensitive lipid-envelopes to enhance the virus release from the endosome following endocytosis were explored. Also, different viral envelopment methodologies (sonication and extrusion) were compared in terms of percentage of virion envelopment and efficiency of gene expression. The artificially enveloped Ad were characterised physicochemically by dot blots, dynamic light scattering and atomic force microscopy. Biologically, the gene expression of enveloped Ad in different pH-sensitive enveloped Ad was studied in vitro and in vivo. The critical role of blood components during systemic administration of Ad was investigated by looking at the interaction of enveloped Ad in cationic, non-pH-sensitive (DOTAP:Chol) or anionic, pH-sensitive (DOPE:CHEMS) lipid bilayers with several different blood components. When Ad was enveloped by cationic bilayers, significantly high levels of viral uptake in HepG2 cells were achieved, independent of any blood coagulation factor, whereas, the levels of cellular uptake and gene expression were similar to naked Ad vectors when an anionic lipid envelope was used. In vitro experiments also showed that artificial envelopment of Ad completely altered the affinity towards both human and murine red blood cells. After intravenous administration into mice, real-time PCR and transgene expression studies indicated that cationic lipid envelopes significantly reduced hepatocyte transduction compared to anionic envelopes. AL T / AST serum levels and liver histology showed that envelopment also improved hepatotoxicity profiles compared to naked Ad. Furthermore, envelopment in DOTAP:Chollipid bilayers significantly increased lung accumulation compared to DOPE:CHEMS enveloped or naked Ad. These results suggest that artificial envelopes for Ad significantly alter the interactions with blood components and divert viral particles from their natural liver tropism resulting in reduced hepatotoxicity. Finally, we sought to explore further opportunities that the artificially enveloped virus constructs could offer, by designing a previously unreported gene therapy vector by simultaneous envelopment of Ad and siRNA within lipid bilayers. Such a dual-activity vector can possibly offer efficacious therapy for different genetic disorders where both turning on and switching off genes would be needed. Dynamic light scattering, transmission electron microscopy and atomic force microscopy were used to characterize these vectors. Agarose gel electrophoresis, ribo-green assays and dot blots showed that siRNA and Ad can be enveloped together within lipid bilayers at high envelopment efficiency. Cellular uptake and in vitro transfection experiments were carried out to show the feasibility of combining siRNA-mediated gene silencing with viral gene transfer using these newly designed dual-activity vectors. In summary, the studies in this thesis contribute to greater understanding of the mechanisms, obstacles and opportunities offered by artificial lipid envelopment of Ad and how these affect the biological activity of these promissing gene therapy vectors in vitro and in vivo.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
New surprises from an old favourite: The emergence of telomerase as a key player in the regulation of cancer stemness
No full textIt has been well established that the upregulation/reactivation of telomerase is a prerequisite for cellular immortalisation and malignant transformation. More significantly, perhaps, telomerase stands at the crossroads of multiple signalling pathways and its upregulation/reactivation leads to the modulation of critical cellular processes, including gene expression and metabolism. In recent years, this multifaceted ribonucleoprotein particle has become increasingly associated with the cancer stem cell (CSC) phenotype in various human cancers. Cancer stemess is a major contributor to therapy resistance and hence tumour recurrence. Here, we discuss new findings about the telomere-independent tumour-promoting functions of telomerase and provide a mechanistic explanation for its regulatory role in CSC biology. It is striking that there is a positive feedback loop between a number of gene products targeting telomerase's reverse transcriptase subunit (TERT) and TERT expression itself. This plausibly amplifies the effects of central oncogenes and oncogenic pathways related to cancer sternness in a cell-autonomous fashion. A more complete elucidation of these regulatory mechanisms affords the opportunity to develop telomerase-focused therapies that differentiate or kill CSCs effectively. (C) 2015 Elsevier B.V. and Societe Francaise de Biochimie et Biologie Moleculaire (SFBBM). All rights reserved
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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