1,720,962 research outputs found
Toxicity profiles and solvent-toxicant interference in the planarian Schmidtea mediterranea after dimethylsulfoxide (DMSO) exposure
No full textTo investigate hydrophobic test compounds in toxicological studies, solvents like dimethylsulfoxide (DMSO) are inevitable. However, using these solvents, the interpretation of test compound-induced responses can be biased. DMSO concentration guidelines are available, but are mostly based on acute exposures involving one specific toxicity endpoint. Hence, to avoid solvent–toxicant interference, we use multiple chronic test endpoints for additional interpretation of DMSO concentrations and propose a statistical model to assess possible synergistic, antagonistic or additive effects of test compounds and their solvents. In this study, the effects of both short- (1 day) and long-term (2 weeks) exposures to low DMSO concentrations (up to 1000 µl l−1) were studied in the planarian Schmidtea mediterranea. We measured different biological levels in both fully developed and developing animals. In a long-term exposure set-up, a concentration of 500 µl l−1 DMSO interfered with processes on different biological levels, e.g. behaviour, stem cell proliferation and gene expression profiles. After short exposure times, 500 µl l−1 DMSO only affected motility, whereas the most significant changes on different parameters were observed at a concentration of 1000 µl l−1 DMSO. As small sensitivity differences exist between biological levels and developmental stages, we advise the use of this solvent in concentrations below 500 µl l−1 in this organism. In the second part of our study, we propose a statistical approach to account for solvent–toxicant interactions and discuss full-scale solvent toxicity studies. In conclusion, we reassessed DMSO concentration limits for different experimental endpoints in the planarian S. mediterranea. Copyright © 2014 John Wiley & Sons, Ltd.This work was supported by a PhD grant for An-Sofie Stevens from IWT (Agentschap voor Innovatie door Wetenschap en Technologie) (no. 101442). Experiments were financed by Hasselt University BOF-financing (Bijzonder Onderzoeksfonds: BOF08G01) and Hasselt University tUL-impulsfinancing (IMPF2PR). Maxime Willems was funded by an OZM grant by IWT (no. 100631)
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
Redox-Related Mechanisms to Rebalance Cancer-Deregulated Cell Growth
No full textA delicate balance exists between the process of carcinogenesis and tissue regeneration. A number of malignant tumours are considered the outcome of an impaired or incomplete regeneration process, resulting in persistently dividing cells. Regeneration-competent tissues and animals are able to prevent and counteract growth abnormalities and seem to have a low vulnerability to chemical carcinogenesis. Cancer cell survival depends, among other things, on various redox-related mechanisms, which are targets of currently developed therapies. Disadvantages of these therapies are a lack of specificity and drug resistance. As the majority of these redox-related mechanisms also play an important role in successful and coordinated cell functioning and reproduction, the regeneration process offers a unique parallel context for modern cancer research. This review focuses on the interconnections between regeneration and carcinogenesis and how an understanding of regenerative forces and redox-controlled mechanisms could contribute to the identification of new therapeutic targets to block the growth and survival of cancer cells.</p
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
Short and long range signalling during brain regeneration in the planarian Schmidtea mediterranea and the involvement of the nou-darake (ndk) genes
No full textPlanaria beschikken over de mogelijkheid om een volledig organisme te regenereren uit slechts enkele cellen door het bezit van een populatie pluripotente stamcellen. Tijdens de regeneratie dient een correcte polariteit behouden te worden. In dit project werden vier homologen van ndk geïdentificeerd in de platworm S. mediterranea. Ook communicatie via gap junctions speelt een belangrijke rol in het behoud van een correcte polariteit. Ndk en ndk2 vertonen expressie in de hersenganglia en de pharynx. Ndk(RNAi) resulteert in de vorming van ectopische hersenganglia en uitbreiding van de hersenen. In tegenstelling tot ndk(RNAi) veroorzaakt de inhibitie van de overige ndk genen geen fenotypische afwijkingen. Toenames in het aantal mitoses werden waargenomen in intacte en regenererende ndk(RNAi) organismen. Octanol-blootstellingen werden gebruikt om GJ communicatie in drie planaria soorten te bestuderen. Bipolaire hoofdvorming werd echter enkel waargenomen in D. japonica
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
Short and long range signalling during brain regeneration in the planarian Schmidtea mediterranea and the involvement of the nou-darake (ndk) genes
No full textPlanaria beschikken over de mogelijkheid om een volledig organisme te regenereren uit slechts enkele cellen door het bezit van een populatie pluripotente stamcellen. Tijdens de regeneratie dient een correcte polariteit behouden te worden. In dit project werden vier homologen van ndk geïdentificeerd in de platworm S. mediterranea. Ook communicatie via gap junctions speelt een belangrijke rol in het behoud van een correcte polariteit. Ndk en ndk2 vertonen expressie in de hersenganglia en de pharynx. Ndk(RNAi) resulteert in de vorming van ectopische hersenganglia en uitbreiding van de hersenen. In tegenstelling tot ndk(RNAi) veroorzaakt de inhibitie van de overige ndk genen geen fenotypische afwijkingen. Toenames in het aantal mitoses werden waargenomen in intacte en regenererende ndk(RNAi) organismen. Octanol-blootstellingen werden gebruikt om GJ communicatie in drie planaria soorten te bestuderen. Bipolaire hoofdvorming werd echter enkel waargenomen in D. japonica
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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