Vasodilator factors in the systemic and local adaptations to pregnancy

We postulate that an orchestrated network composed of various vasodilatory systems participates in the systemic and local hemodynamic adaptations in pregnancy. The temporal patterns of increase in the circulating and urinary levels of five vasodilator factors/systems, prostacyclin, nitric oxide, kallikrein, angiotensin-(1–7) and VEGF, in normal pregnant women and animals, as well as the changes observed in preeclamptic pregnancies support their functional role in maintaining normotension by opposing the vasoconstrictor systems. In addition, the expression of these vasodilators in the different trophoblastic subtypes in various species supports their role in the transformation of the uterine arteries. Moreover, their expression in the fetal endothelium and in the syncytiotrophoblast in humans, rats and guinea-pigs, favour their participation in maintaining the uteroplacental circulation. The findings that sustain the functional associations of the various vasodilators, and their participation by endocrine, paracrine and autocrine regulation of the systemic and local vasoactive changes of pregnancy are abundant and compelling. However, further elucidation of the role of the various players is hampered by methodological problems. Among these difficulties is the complexity of the interactions between the different factors, the likelihood that experimental alterations induced in one system may be compensated by the other players of the network, and the possibility that data obtained by manipulating single factors in vitro or in animal studies may be difficult to translate to the human. In addition, the impossibility of sampling the uteroplacental interface along normal pregnancy precludes obtaining longitudinal profiles of the various players. Nevertheless, the possibility of improving maternal blood pressure regulation, trophoblast invasion and uteroplacental flow by enhancing vasodilation (e.g. L-arginine, NO donors, VEGF transfection) deserves unravelling the intricate association of vasoactive factors and the systemic and local adaptations to pregnancy

Entry Cost, Financial Friction, and Cross-Country Differences in Income and TFP

This paper develops a model to assess the quantitative effect of entry cost and financial friction on cross-country income and total factor productivity (TFP) differences. The main focus is on the interaction between entry cost and financial friction. The model is calibrated to match establishment-level statistics for the U.S. economy assuming a perfect financial market. The quantitative analysis shows that entry costs and financial frictions together can generate a factor ten of the differences in income per capita and a factor five of the differences in TFP, and a large part of the differences are accounted for by the interaction between entry cost and financial friction. The main mechanism is that financial friction amplifies the effect of entry cost by boosting the effective entry cost

Efficient Expropriation: Sustainable Fiscal Policy in a Small Open Economy

We study a small open economy characterized by two empirically important frictions- incomplete financial markets and an inability of the government to commit to policy. We characterize the best sustainable fiscal policy and show that it can amplify and prolong shocks to output. In particular, even when the government is completely benevolent, the government's credibility not to expropriate capital varies endogenously with the state of the economy and may be scarcest during recessions. This increased threat of expropriation depresses investment, prolonging downturns. It is the incompleteness of financial markets and the lack of commitment that generate investment cycles even in an environment where first-best capital stock is constant

Entry Barriers, Competition, and Technology Adoption

There are large differences in income per capita across countries. Growth accounting finds that a large part of the differences comes from the differences in total factor productivity (TFP). This paper explores whether barrier to entry is an important factor for the cross-country differences in TFP. The paper develops a new model to link entry barriers and technology adoption. In the model, higher barriers to entry effectively reduce entry threat, and lower entry threat leads to adoption of less productive technologies. The paper demonstrates that technology adopted in the economy with entry threats is at least as good as the technology adopted in the economy without entry threats. Moreover, the paper presents numerical simulations that suggest entry barriers could be a quantitatively important reason for cross-country differences in TFP and are more harmful to productivity in the countries with monopolists facing inelastic demand