This dissertation comprises three essays on theoretical and empirical issues in industrial organization. Chapter 1 outlines the issues explored in the subsequent chapters and briefly describes their conclusions. Chapter 2 explores how product differentiation impacts the incentive compatibility condition for firms to sustain implicit collusion in games of repeated interaction where, in contrast to previous studies, I focus on a market which is simultaneously vertically and horizontally differentiated. To achieve this objective, vertical differentiation is incorporated into an otherwise standard Hotelling framework. The ensuing mixed model of differentiation shows how the interrelationships between both forms of differentiation impact the incentives to collude, and is more general since it replicates previous findings throughout the literature. In Chapter 3, a multiproduct oligopoly model admitting product differentiation and a discrete choice demand model are proposed and estimated to determine if patterns of anti-competitiveness exist across distinct segments of the European car market. This chapter focuses on the evolution of price competition at a finer level than has been studied with a view to empirically challenge the notion that the European car market is wholly anti-competitive. Empirical results show that firm conduct varies due to the intensity of within-segment competition among rival firms. There is evidence of softer competition in the larger, mid- to full-sized segments and more aggressive competition in the smaller, entry-level subcompact segment. Chapter 4 represents a formal extension of the analysis in Chapter 3. In this chapter I examine the competitive structure of the U.S. automobile market using proprietary data comprising actual dealer-level transaction prices of several models of cars and light trucks sold in the domestic U.S. market between 2004 and 2007. The chapter is the first such study to employ consumer end-prices for automobiles in a structural New Empirical Industrial Organization (NEIO) framework. Empirical results reveal that there is more aggressive pricing in the light truck segments comprising minivans/SUVs and pickups, Bertrand pricing in the smaller, entry-level car segments, and softer competition in the full-size car segment. There is also a strong preference for domestically produced light trucks although consumers generally prefer to drive fuel efficient vehicles. / Ph. D.

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Indiana University-Purdue University Indianapolis (IUPUI) / SIRT1 (Sirtuin 1) is a founding member of a family of seven proteins and histone deacetylases. It is involved in cellular resistance to stress, metabolism, differentiation, aging, and tumor suppression. SIRT1-/- mice demonstrate embryonic and postnatal development defects. We examined hematopoietic and endothelial cell differentiation of SIRT1-/- mouse embryonic stem (mES) cells in vitro, and hematopoietic progenitors in SIRT1+/+, SIRT1+/-, and SIRT1-/- mice. SIRT1-/- ES cells exhibited markedly delayed/immature formation of blast colony-forming cells (BL-CFCs). When individual blast colonies were analyzed for hematopoietic and endothelial potential, replated SIRT1-/- BL-CFC possessed limited hematopoietic potential, whereas endothelial potential was essentially unaltered. The ability of SIRT1-/- ES cells to form primitive erythroid progenitors was not only delayed but greatly decreased. Moreover, after differentiation of SIRT1-/- mES cells, there were also significant decreases in granulocyte-macrophage (CFU-GM) and multipotential (CFU-GEMM) progenitor cells. Differentiation delay/defects were associated with delayed capacity to switch off Oct4, Nanog and Fgf5, decreased β-H1 globin, β-major globin, and Scl gene expression and reduced activation of the Erk1/2 pathway upon SIRT1-/- ES cell commitment. Reintroduction of WT SIRT1 into SIRT1-/- cells partially rescued the primitive erythroid progenitor formation of SIRT1-/- cells and the expression of hemoglobin genes, Hbb-bh1 and Hbb-b1, suggesting that the defect of hematopoietic commitment is due to deletion of SIRT1, and not to genetic drifting of SIRT1-/- cells. To confirm the requirement for SIRT1 for normal development of hematopoietic progenitor cells, we assessed embryonic and adult hematopoiesis in SIRT1+/+, SIRT1+/- and SIRT1-/- mice. Yolk sacs from SIRT1 mutant embryos generated fewer primitive erythroid precursors compared to wild-type (WT) and heterozygous mice. Moreover, knockout of SIRT1 decreased primary bone marrow hematopoietic progenitor cells (HPCs) in 5 week and 12 month old mice, which was especially notable at lower (5%) O2 tension. In addition these progenitors survived less well in vitro under conditions of delayed growth factor addition. Taken together, these results demonstrate that SIRT1 plays a role in ES cell hematopoietic differentiation and mouse hematopoiesis.

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During embryo development, extracellular matrix (ECM) remodeling by matrix metalloproteinases (MMPs) and promotes downstream cell specifications. Pluripotent stem cell (PSC) aggregates can recapitulate various aspects of embryogenesis in vitro, and incorporation of biomaterial microparticles also provides an ideal platform to study cell-biomaterial interactions. Stem cell interactions with ECM-based biomaterials can impact tissue remodeling and differentiation propensity via modulation of MMP activity. This work investigated the MMP activity and subsequent mesenchymal differentiation of embryonic stem cell (ESC) aggregates with incorporated gelatin methacrylate (GMA) MPs with either low (20%) or high (90%) cross-linking densities, corresponding to faster or slower degradation rate, respectively. GMA MP incorporation increased total MMP and MMP-2 levels within 3D ESC aggregates in a substrate-dependent manner. GMA MP-incorporated aggregates also expressed higher levels of epithelial-to-mesenchymal transition markers and displayed enhanced mesenchymal morphogenesis than aggregates without MPs, and the MP-mediated effects were completely abrogated with MMP inhibitor treatment. This work predicts that control of proteolytic responses via introducing ECM-based MPs may offer a novel avenue to engineer the ECM microenvironment to modulate stem cell differentiation.

published_or_final_version / Medicine / Master / Master of Philosophy

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This study elucidates the temporal expression and regulation of transglutaminase (TGase) and ornithine decarboxylase (ODCase) during cell proliferation and differentiation. In synchronized CHO cells, there were two peaks of TGase activity expressed in G₁ and a smaller peak of activity in mid S phase. ODCase exhibited a single peak of expression in mid G₁ which was inhibited by the administration of both cycloheximide and actinomycin D. In contrast, the increase in TGase activity was not inhibited at any time measured by administration of either cycloheximide or actinomycin D to these cells. TGase activity in CHO cells was not affected by the addition of analogs of cyclic AMP, whereas ODCase activity was increased at all times measured. Retinol administration increased TGase activity 1 hr after release in CHO cells and the activity remained elevated for 4 hr. Retinol administration resulted in the inhibition of ODCase expression in these cells. The administration of α-melanocyte-stimulating hormone (MSH) to mouse melanoma cells resulted in a biphasic increase of TGase activity and a single peak of ODCase activity within 7 hr. In melanoma cells, addition of cycloheximide abolished the first peak of TGase activity but not the second peak. Actinomycin D did not inhibit either peak of TGase expression. The administration of both cycloheximide and actinomycin D inhibited ODCase activity after MSH stimulation. Analogs of cyclic AMP, when added to log phase mouse melanoma cells, increased ODCase but not TGase activity at all points measured. In these cells, retinoic acid plus MSH markedly enhanced the activity of the initial TGase peak compared to MSH alone. ODCase expression was attenuated with retinoic acid plus MSH. Dexamethasone (DEX) induced the first peak of TGase activity but not the second peak seen with MSH administration alone. Administration of DEX resulted in a peak expression of ODCase activity approximately 30% of that seen with MSH alone. In general, chelation of extracellular calcium with EGTA totally blocked ODCase expression with MSH, retinoic acid or DEX. Partial or total ablation of TGase expression was seen with addition of MSH or retinoic acid, but very little inhibition of this enzyme was evident when EGTA was added with DEX or DEX plus MSH. Addition of calcium after all CA⁺⁺-blocks restored the expression of both enzymes.