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The concept of negative externality is central to the teaching of environmental economics, but corrective taxes are almost always regressive. How exactly might governments return externality-correcting tax revenue to overcome regressivity and not alter marginal incentives? In addition, there is a desire to achieve a double dividend in the use of externality-correcting taxes, that is, to use the revenue to offset existing distortionary taxes, such as those on labor that produce a dead weight loss. In this article, the authors explain a classroom game that was developed for students to understand the theory of externalities, taxation dead weight loss, and regressivity. Then, the problem helps students explore the actual design of a policy that satisfies the double dividend hypothesis and corrects for regressivity.

In this article, the author first outlines the responsibilities of governors as explained by the Department for Children, Schools and Families (DCSF), Audit Commission and the Office for Standards in Education (Ofsted). Governors' work includes not just developing strategy and policy construction, but conflict resolution, too. Brief case studies of these are described. Owing to the increasing workload of governing bodies, members sometimes find it challenging to deal with unpleasant people pleasantly. Occasionally, governors, as representatives, are confused about how they should vote and act. They are caught between a rock and hard place by the stakeholder groups to which they belong on the one hand and the desire to promote the interests of the children at the school on the other. The article concludes by listing useful suggestions from governors that emerged at a workshop in which they participated.

Responsibilities placed on a governing body are profound--starting with governors' own performance and the achievement of the pupils. In recognition of the weight of duty placed upon them, every governing body has, by law, to appoint a clerk who is not a governor. Committees of the governing body may be clerked by governors, but the main meeting of the full governing body must be supported by someone who is apart from (and not a part of) it. In this article, the author describes the characteristics of an effective clerk.

The tumor necrosis factor-[alpha] (TNF[alpha])-mediated inhibition of myogenic differentiation is found to be dependent on p53 through a PW1-mediated pathway. The p53 plays a novel role in mediating muscle stem cell behavior and muscle atrophy, and has pointed towards new targets for the therapeutic treatment of muscle wasting (cachexia).

Optical coherence tomography (OCT) is a novel, high-resolution diagnostic tool that is capable of imaging the arterial-wall and plaques. The differentiation between different types of atherosclerotic plaque is based on qualitative differences in gray levels and structural appearance. We hypothesize that a quantitative data analysis of the OCT signal allows measurement of light attenuation by the local tissue components, which can facilitate quantitative spatial discrimination between plaque constituents. High-resolution OCT images (at 800 nm) of human atherosclerotic arterial segments obtained at autopsy were histologically validated. Using a new, simple analysis algorithm, which incorporates the confocal properties of the OCT system, the light attenuation coefficients for these constituents were determined: for diffuse intimal thickening (5.5 [- or -] 1.2 [mm.sup.-1]) and lipid-rich regions (3.2 [+ or -] 1.1 [mm.sup.-1]), the attenuation differed significantly from media (9.9 [+ or -] 1.8 [mm.sup.-1]), calcifications (11.1 [+ or -] 4.9 [mm.sup.-1]) and thrombi (11.2 [+ or -] 2.3 [mm.sup.-1]) (p < 0.01). These proof of principle studies show that simple quantitative analysis of the OCT signals allows spatial determination of the intrinsic optical attenuation coefficient of atherosclerotic tissue components within regions of interest. Combining morphological imaging by OCT with the observed differences in optical attenuation coefficients of the various regions may enhance discrimination between various plaque types. Index Terms--Attenuation measurement, cardiovascular system, imaging.

PW1 is a mediator of p53 and TNF[alpha] signaling pathways previously identified in a screen to isolate muscle stem cell regulators. We generated transgenic mice carrying a C-terminal deleted form of PW1 ([DELTA]PW1) which blocks p53-mediated cell death and TNF[alpha]-mediated NF[kappa]B activation fused to the myogenin promoter. Embryonic/fetal muscle development appears normal during transgene expression, however, postnatal transgenic pups display severe phenotypes including runtism, reduced muscle mass and fiber diameters resembling atrophy. Atrogin-1, a marker of skeletal muscle atrophy, is expressed postnatally in transgenic mice. Electron microscopic analyses of transgenic muscle reveal a marked decrease in quiescent muscle satellite cells suggesting a deregulation of postnatal stem cells. Furthermore, transgenic primary myoblasts show a resistance to the effects of TNF[alpha] upon differentiation. Taken together, our data support a role for PW1 and related stress pathways in mediating skeletal muscle stem cell behavior which in turn is critical for postnatal muscle growth and homeostasis. In addition, these data reveal that postnatal stem cell behavior is likely specified during early muscle development. Keywords: Satellite cells; Stem cells; Skeletal muscle; Development; Mouse; PW1/Peg3; p53; TNF; Atrophy

The differentiation of epithelial cells and fiber cells from the anterior and posterior compartments of the lens vesicle, respectively, give the mammalian lens its distinctive polarity. While much progress has been made in understanding the molecular basis of fiber differentiation, little is known about factors that govern the differentiation of the epithelium. Members of the Wnt growth factor family appear to be key regulators of epithelial differentiation in various organ systems. Wnts are ligands for Frizzled receptors and can activate several signaling pathways, of which the best understood is the Wnt/[beta]-catenin pathway. The presence of LDL-related protein coreceptors (LRPs) 5 or 6 has been shown to be a requirement for Wnt signaling through the [beta]-catenin pathway. To access the role of this signaling pathway in the lens, we analyzed mice with a null mutation of lrp6. These mice had small eyes and aberrant lenses, characterized by an incompletely formed anterior epithelium resulting in extrusion of the lens fibers into the overlying corneal stroma. We also showed that multiple Wnts, including 5a, 5b, 7a, 7b, 8a, 8b, and Frizzled receptors 1, 2, 3, 4, and 6, were detected in the lens. Expression of these molecules was generally present throughout the lens epithelium and extended into the transitional zone, where early fiber elongation occurs. In addition to both LRP5 and LRP6, we also showed the expression of other molecules involved in Wnt signaling and its regulation, including Dishevelleds, Dickkopfs, and secreted Frizzled-related proteins. Taken together, these results indicate a role for Wnt signaling in regulating the differentiation and behavior of lens cells. Keywords: Lens development; Wnt signaling; [beta]-Catenin; LRP6; Lens epithelium