Macrophages promote epithelial repair through hepatocyte growth factor secretion.

Macrophages play a critical role in intestinal wound repair. However, the mechanisms of macrophage-assisted wound repair remain poorly understood. We aimed to characterize more clearly the repair activities of murine and human macrophages. Murine macrophages were differentiated from bone marrow cells and human macrophages from monocytes isolated from peripheral blood mononuclear cells of healthy donors (HD) or Crohn's disease (CD) patients or isolated from the intestinal mucosa of HD. In-vitro models were used to study the repair activities of macrophages. We found that murine and human macrophages were both able to promote epithelial repair in vitro. This function was mainly cell contact-independent and relied upon the production of soluble factors such as the hepatocyte growth factor (HGF). Indeed, HGF-silenced macrophages were less capable of promoting epithelial repair than control macrophages. Remarkably, macrophages from CD patients produced less HGF than their HD counterparts (HGF level: 84âeuro0/00±âeuro0/0027âeuro0/00pg/mg of protein and 45âeuro0/00±âeuro0/0034âeuro0/00pg/mg of protein, respectively, for HD and CD macrophages, Pâeuro0/00<âeuro0/000·009) and were deficient in promoting epithelial repair (repairing activity: 90·1âeuro0/00±âeuro0/004·6 and 75·8âeuro0/00±âeuro0/008·3, respectively, for HD and CD macrophages, Pâeuro0/00<âeuro0/000·0005). In conclusion, we provide evidence that macrophages act on wounded epithelial cells to promote epithelial repair through the secretion of HGF. The deficiency of CD macrophages to secrete HGF and to promote epithelial repair might contribute to the impaired intestinal mucosal healing in CD patients.

Effects of uncertain lifetime and annuity insurance on capital accumulation and growth

This paper studies the effects of uncertain lifetime on capitalaccumulation and growth and also the sensitivity of thoseeffects to the existence of a perfect annuities market. Themodel is an overlapping generations model with uncertainlifetimes. The technology is convex and such that the marginalproduct of capital is bounded away from zero. A contribution ofthis paper is to show that the existence of accidental bequestsmay lead the economy to an equilibrium that exhibits asymptoticgrowth, which is impossible in an economy with a perfect annuitiesmarket or with certain lifetimes. This paper also shows that ifindividuals face a positive probability of surviving in everyperiod, they may be willing to save at any age. This effect ofuncertain lifetime on savings may also lead the economy to anequilibrium exhibiting asymptotic growth even if there exists aperfect annuities market.

Externalities and interdependent growth: Theory and evidence

I formulate and estimate a model of externalities within countriesand technological interdependence across countries. I find that externalreturns to scale to physical capital within countries are 8 percent; thata 10 percent increase of total factor productivity of a country's neighborsraises its total factor productivity by 6 percent; and that a 2 percentannual growth rate of labor productivity can be explained as an endogenousresponse to an exogenous 0.2 percent annual growth rate of total factorproductivity in the steady--state.

Book production and the onset of modern economic growth

Endogenous growth theory suggests that human capital formation plays a significant role for the wealth and poverty of nations. In contrast to previous studies which denied the role of human capital as a crucial determinant of for really long-term growth, we confirm its importance. Indicators of human capital like literacy rates are lacking for the period of 1450-1913; hence, we use per capita book production as a proxy for advanced literacy skills. This study explains how, and to what extent, growth disparities are a function of human capital formation.

Growth accounting in items of turbulence and death: efficiency, technology, capital accumulation and human capital 1929-1950

We employ a non-parametrical approach to growth accounting (Data Envelopment Analysis,DEA) to disentangle the proximate sources of labour productivity growth in 41 nationsbetween 1929 and 1950 by decomposing productivity growth into four components:technological change; efficiency catch-up (movements towards the production frontier),capital accumulation and human capital accumulation. We show that efficiency catch-upgenerally explains productivity growth, whereas technological change and factoraccumulation were limited and distorted by the effects of war. War clearly hamperedefficiency. Moreover, an unbalanced ratio of human capital to physical capital (a gap to thetechnological leader) was crucial for efficiency catching-up.

Trade, extent of the market and economic growth 1960-1996

We find that trade and domestic market size are robust determinants of economic growth overthe 1960-1996 period when trade openness is measured as the US dollar value of imports andexports relative to GDP in PPP US$ ('real openness'). When trade openness is measured asthe US dollar value of imports and exports relative to GDP in exchange rate US$ ('nominalopenness') however, trade and the size of domestic markets are often non-robust determinantsof growth. We argue that real openness is the more appropriate measure of trade and that ourempirical results should be seen as evidence in favor of the extent-of-the-market hypothesis.

The growth and diffusion of knowlegde and the theory of the firm

We analyze the implications of a market imperfection related to the inability to establish intellectual property rights, that we label {\it unverifiable communication}. Employees are able to collude with external parties selling ``knowledge capital'' of the firm. The firm organizer engages in strategic interaction simultaneously with employees and competitors, as she introduces endogenous transaction costs in the market for information between those agents. Incentive schemes and communication costs are the key strategic variables used by the firm to induce frictions in collusive markets. Unverifiable communication introduces severe allocative distortions, both at internal product development and at intended sale of information (technology transfer). We derive implications of the model for observable decisions like characteristics of the employment relationship (full employment, incompatibility with other jobs), firms' preferences over cluster characteristics for location decisions, optimal size at entry, in--house development vs sale strategies for innovations and industry evolution.

Adjustment to target capital, finance and growth

Does financial development result in capital being reallocated more rapidly to industries where it is most productive? We argue that if this was the case, financially developed countries should see faster growth in industries with investment opportunities due to global demand and productivity shifts. Testing this cross-industry cross-country growth implication requires proxies for (latent) global industry investment opportunities. We show that tests relying only on data from specific (benchmark) countries may yield spurious evidence for or against the hypothesis. We therefore develop an alternative approach that combines benchmark-country proxies with a proxy that does not reflect opportunities specific to a country or level of financial development. Our empirical results yield clear support for the capital reallocation hypothesis.