Requirement for Pdx1 in specification of latent endocrine progenitors in zebrafish

<p>Abstract</p> <p>Background</p> <p>Insulin-producing beta cells emerge during pancreas development in two sequential waves. Recently described later-forming beta cells in zebrafish show high similarity to second wave mammalian beta cells in developmental capacity. Loss-of-function studies in mouse and zebrafish demonstrated that the homeobox transcription factors Pdx1 and Hb9 are both critical for pancreas and beta cell development and discrete stage-specific requirements for these genes have been uncovered. Previously, exocrine and endocrine cell recovery was shown to follow loss of <it>pdx1 </it>in zebrafish, but the progenitor cells and molecular mechanisms responsible have not been clearly defined. In addition, interactions of <it>pdx1 </it>and <it>hb9 </it>in beta cell formation have not been addressed.</p> <p>Results</p> <p>To learn more about endocrine progenitor specification, we examined beta cell formation following morpholino-mediated depletion of <it>pdx1 </it>and <it>hb9</it>. We find that after early beta cell reduction, recovery occurs following loss of either <it>pdx1 </it>or <it>hb9 </it>function. Unexpectedly, simultaneous knockdown of both <it>hb9 </it>and <it>pdx1 </it>leads to virtually complete and persistent beta cell deficiency. We used a <it>NeuroD:EGFP </it>transgenic line to examine endocrine cell behavior <it>in vivo </it>and developed a novel live-imaging technique to document emergence and migration of late-forming endocrine precursors in real time. Our data show that Notch-responsive progenitors for late-arising endocrine cells are predominantly post mitotic and depend on <it>pdx1</it>. By contrast, early-arising endocrine cells are specified and differentiate independent of <it>pdx1</it>.</p> <p>Conclusions</p> <p>The nearly complete beta cell deficiency after combined loss of <it>hb9 </it>and <it>pdx1 </it>suggests functional cooperation, which we clarify as distinct roles in early and late endocrine cell formation. A novel imaging approach permitted visualization of the emergence of late endocrine cells within developing embryos for the first time. We demonstrate a <it>pdx1</it>-dependent progenitor population essential for the formation of duct-associated, second wave endocrine cells. We further reveal an unexpectedly low mitotic activity in these progenitor cells, indicating that they are set aside early in development.</p

CDK4 regulation by TNFR1 and JNK is required for NF-κB–mediated epidermal growth control

Nuclear factor κB (NF-κB) mediates homeostatic growth inhibition in the epidermis, and a loss of NF-κB function promotes proliferation and oncogenesis. To identify mechanisms responsible for these effects, we impaired NF-κB action in the epidermis by three different genetic approaches, including conditional NF-κB blockade. In each case, epidermal hyperplasia was accompanied by an increase in both protein levels and tissue distribution of the G1 cell cycle kinase, CDK4. CDK4 up-regulation required intact TNFR1 and c-Jun NH2-terminal kinase (JNK) function. Cdk4 gene deletion concomitant with conditional NF-κB blockade demonstrated that CDK4 is required for growth deregulation. Therefore, epidermal homeostasis depends on antagonist regulation of CDK4 expression by NF-κB and TNFR1/JNK

Measuring and modeling of melt viscosity for drug polymer mixtures

Melt viscosity is an essential property in pharmaceutical processes such as mixing, extrusion, fused deposition modeling, and melt coating. Measuring and modeling of the melt viscosity for drug/polymer mixtures is essential for optimization of the manufacturing process. In this work, the melt viscosity of nine formulations containing the drug substances acetaminophen, itraconazole, and griseofulvin, as well as the pharmaceutical polymers Eudragit EPO, Soluplus, and Plasdone S-630, were analyzed with a rotational and oscillatory rheometer. The shear rate, temperature, and drug fraction were varied systematically to investigate their influence on viscosity. The results for the pure polymers showed typical shear-thinning behavior and are fundamental for modeling with the Carreau and Arrhenius approaches. The investigations of the viscosity of the drug/polymer mixtures resulted in a plasticizing or a filler effect, depending on the type of drug and the phase behavior. A drug shift factor was proposed to model the change in viscosity as a function of the drug fraction. On this basis, a universal model to describe the melt viscosity of drug/polymer mixtures was developed, considering shear rate, temperature, and drug fraction

Reckoning up: sexual harassment and violence in the neoliberal university

This paper situates sexual harassment and violence in the neoliberal university. Using data from a ‘composite ethnography’ representing twelve years of research, I argue that institutional inaction on these issues reflects how they are ‘reckoned up’ in the context of gender and other structures. The impact of disclosure is projected in market terms: this produces institutional airbrushing which protects both the institution and those (usually privileged men) whose welfare is bound up with its success. Staff and students are differentiated by power/value relations, which interact with gender and intersecting categories. Survivors are often left with few alternatives to speaking out in the ‘outrage economy’ of the corporate media: however, this can support institutional airbrushing and bolster punitive technologies. I propose the method of Grounded Action Inquiry, implemented with attention to Lorde’s work on anger, as a parrhesiastic practice of ‘speaking in’ to the neoliberal institution

Reconstruction of cell population dynamics using CFSE

Background: Quantifying cell division and death is central to many studies in the biological sciences. The fluorescent dye CFSE allows the tracking of cell division in vitro and in vivo and provides a rich source of information with which to test models of cell kinetics. Cell division and death have a stochastic component at the single-cell level, and the probabilities of these occurring in any given time interval may also undergo systematic variation at a population level. This gives rise to heterogeneity in proliferating cell populations. Branching processes provide a natural means of describing this behaviour. Results: We present a likelihood-based method for estimating the parameters of branching process models of cell kinetics using CFSE-labeling experiments, and demonstrate its validity using synthetic and experimental datasets. Performing inference and model comparison with real CFSE data presents some statistical problems and we suggest methods of dealing with them. Conclusion: The approach we describe here can be used to recover the (potentially variable) division and death rates of any cell population for which division tracking information is available

STrengthening the REporting of Genetic Association Studies (STREGA)— An Extension of the STROBE Statement

Julian Little and colleagues present the STREGA recommendations, which are aimed at improving the reporting of genetic association studies