Luciferase expression and bioluminescence does not affect tumor cell growth in vitro or in vivo

Live animal imaging is becoming an increasingly common technique for accurate and quantitative assessment of tumor burden over time. Bioluminescence imaging systems rely on a bioluminescent signal from tumor cells, typically generated from expression of the firefly luciferase gene. However, previous reports have suggested that either a high level of luciferase or the resultant light reaction produced upon addition of D-luciferin substrate can have a negative influence on tumor cell growth. To address this issue, we designed an expression vector that allows simultaneous fluorescence and luminescence imaging. Using fluorescence activated cell sorting (FACS), we generated clonal cell populations from a human breast cancer (MCF-7) and a mouse melanoma (B16-F10) cell line that stably expressed different levels of luciferase. We then compared the growth capabilities of these clones in vitro by MTT proliferation assay and in vivo by bioluminescence imaging of tumor growth in live mice. Surprisingly, we found that neither the amount of luciferase nor biophotonic activity was sufficient to inhibit tumor cell growth, in vitro or in vivo. These results suggest that luciferase toxicity is not a necessary consideration when designing bioluminescence experiments, and therefore our approach can be used to rapidly generate high levels of luciferase expression for sensitive imaging experiments

Assets and domestic units: methodological challenges for longitudinal studies of poverty dynamics

Tracking change in assets access and ownership in longitudinal research is difficult. Assets are rarely assigned to individuals. Their benefit and management are spread across domestic units which morph over time. We review the challenges of using assets to understand poverty dynamics, and tracking the domestic units that own and manage assets. Using case studies from longitudinal research we demonstrate that assets can afford useful insights into important change

Exposing Politicians’ Peccadilloes in Comparative Context: Explaining the Frequency of Political Sex Scandals in Eight Democracies Using Fuzzy Set Qualitative Comparative Analysis

This article was published in the journal Political Communication [© Taylor & Francis Group]. The definitive version is available at: http://dx.doi.org/10.1080/10584609.2012.737434Political sex scandals are largely absent in some democracies but proliferate in others. However, there have so far been few if any comprehensive attempts to document the actual number of sex scandals that have occurred and to explain their presence (and, indeed, absence), and the one study that has (Barker's 1994 study) ended in the early 1990s and had numerous problems in relation to defining and documenting such scandals. Based on extensive research, this article documents the number of sex scandals in eight advanced industrial democracies and tries to explain their occurrence using Charles Ragin's fuzzy set qualitative comparative analysis. The article has three goals: to determine the number of sex scandals in different democracies, explain why this might be, and demonstrate the utility of fuzzy set qualitative case analysis for small- and medium-N comparative research

Not all news sources are equally informative : a cross-national analysis of political knowledge in Europe

Across a sample of twenty-seven European nations, we examine variation in the level of factual political knowledge in relation to self-reported exposure to news programs aired by public or commercial channels, and to broadsheet or tabloid newspapers. Unlike previous studies, we estimate the effects of exposure to these news outlets while controlling for self-selection into the audience. Our results show that the positive effects of exposure to broadsheets and public broadcasting on knowledge remain robust. Finally, we show that only exposure to broadsheets (and not to public broadcasting) narrows the knowledge gap within nations; relatively apathetic individuals who read broadsheet newspapers are able to “catch up” with their more attentive counterparts