Market Competition and the Health Composition of Manufactured Food.

There has been surprisingly little research to date on the supply-side role of food manufacturers on equilibrium health outcomes for consumers. In this letter we consider an oligopoly model in which food processors choose the health composition of manufactured food. We show that price competition between food processors leads to unhealthy food composition in the market equilibrium, even under circumstances in which consumers know food composition is unhealthy. Taxes on manufactured food decrease the healthiness of manufactured foods whenever improved consumer health increases the price elasticity of food demand. Copyright © 2016 John Wiley & Sons, Ltd.

On the 4-H Study of Positive Youth Development.

The research reported in this issue advances our understanding of the multiple interactive influences on young people's development. The study invokes Relational Developmental Systems Theory to show, among other findings, how the impact of out-of-school time depends on the number and range of different types of activities young people engage in. The study also demonstrates that developmental assets (the 5 Cs) can co-exist with problem behavior, an important contribution to the positive youth development perspective. Readers will also find in these articles diverse strategies of data analysis and exemplars of research that informs practice as well as theory.

Development in youth enterprises.

Business enterprises run by youth can create jobs and teach the principles of free enterprise but also convey skills that can be used by employees in large companies, as well as political activists and entrepreneurs. Research is needed to test the efficacy of this approach and identify its key components.

Building mentoring relationships.

This article is the first of three brief commentaries on this volume. The authors are highly influential pioneers in the study of youth mentoring relationships, and their contributions helped shape the focus of the conceptual framework featured in the opening article by Karcher and Nakkula. Their commentary sheds light on the history of key issues presented in this volume, including the origins of their early work on instrumentality--goal-focused orientation--and relationship building in youth mentoring, and links those efforts to the contributions presented in this special issue.

Why mentoring in the workplace works.

Workplaces are ideal contexts for mentoring relationships between adults and older youth. To teach the competencies required in contemporary workplaces (many of which are equally useful in other settings), mentors need to use sophisticated teaching behaviors, which the authors characterize as reflective questioning and problem solving.

Glycoprotein IIb/IIIa inhibitors increase COAT-platelet production in vitro.

Platelets activated simultaneously with thrombin and collagen reveal a subpopulation of cells that express on their surfaces high levels of several alpha-granule proteins, including factor V and fibrinogen; these COAT platelets (collagen and thrombin-activated platelets) represent roughly 30% of the total population. Evidence of enhanced stability of proteins on the COAT-platelet surface was provided by the observation that PAC-1, a mAB recognizing the activated form of glycoprotein (GP) IIb/IIIa, did not inhibit fibrinogen binding to COAT-platelets. We therefore undertook a systematic evaluation of the effects of other GP IIb/IIIa inhibitors on the production of COAT platelets. Not only did GP IIb/IIIa antagonists fail to inhibit the retention of fibrinogen on COAT-platelets, but several actually increased the absolute percentage of COAT platelets produced. The increases over control values in the presence of eptifibatide, tirofiban, and DMP-802 were 1.36-, 1.20-, and 1.05-fold, respectively (P <.01 for each comparison). COAT-platelet production in the presence of abciximab was not significantly affected. However, platelet activation with thrombin plus ALB6, an Fc-receptor agonist, produces a product, referred to as FcRT platelets, that is indistinguishable from COAT platelets; all 4 GP IIb/IIIa antagonists tested potentiated formation of FcRT platelets. These findings indicate that fibrinogen binding to COAT platelets and FcRT platelets is not affected by available GP IIb/IIIa inhibitors. More importantly, our study demonstrates a potentiation of COAT-platelet production by some GP IIb/IIIa antagonists that may be relevant to the observation that long-term administration of orally available GP IIb/IIIa inhibitors not only failed to protect patients but actually increased the frequency of acute coronary events.

Stimulated platelets use serotonin to enhance their retention of procoagulant proteins on the cell surface.

Activated platelets bind numerous adhesive and procoagulant proteins by receptor-mediated processes. Although there is little evidence to suggest that these processes are heterogeneous in platelets, we previously found that platelets co-stimulated with collagen and thrombin express functional alpha-granule factor V only on a subpopulation of cells. Here we show that these cells, referred to as 'COAT-platelets', bind additional alpha-granule proteins, including fibrinogen, von Willebrand factor, thrombospondin, fibronectin and alpha2-antiplasmin. These proteins are all transglutaminase substrates, and inhibitors of transglutaminase prevent the production of COAT-platelets. A synthetic transglutaminase substrate (CP15) also binds to COAT-platelets, and analysis by high performance liquid chromatography/mass spectrometry shows that a product is formed with a relative molecular mass (Mr) equal to CP15 plus 176. Serotonin, an abundant component of platelet-dense granules, has an Mr of 176, and fibrinogen isolated from COAT-platelets contains covalently linked serotonin. Synthetic bovine serum albumin-(serotonin)6 binds selectively to COAT-platelets and also inhibits the retention of procoagulant proteins on COAT-platelets. These data indicate that COAT-platelets use serotonin conjugation to augment the retention of procoagulant proteins on their cell surface through an as yet unidentified serotonin receptor.