Essays on investment, growth and income distribution

In this dissertation, I examine both theoretically and empirically the relationship between stock prices and income distribution using an endogenous growth model with social status impatience.^ The theoretical part looks into how status impatience and current economic status jointly determine time preference, savings, future economic status, stock prices, growth and wealth distribution in the steady state. This work builds on Burgstaller and Karayalcin (1996).^ More specifically, I look at (i) the effects of the distribution of status impatience levels on the distribution of steady state assets, incomes and consumption and (ii) the effects of changes in relative levels of status impatience on stock prices. Therefore, from (i) and (ii), I derive the correlation between stock prices, incomes and asset distribution. Also, the analysis of the stack market is undertaken in the presence of adjustment costs to investments.^ The empirical chapter looks at (i) the correlation between income inequality and long run economic growth on the one hand and (ii) the correlation between stock market prices and income inequality on the other. The role of stock prices and social status is examined to better understand the forces that enable a country to grow overtime and to determine why output per capita varies across countries. The data are from Summers and Heston (1988), Barro and Wolf (1989), Alesina and Rodrik (1994), Global financial Database (1997) and the World Bank. Data for social status are collected through a primary sample survey on the internet. Twenty-five developed and developing countries are included in the sample.^ The model developed in this study was specified as a system of simultaneous equations, in which per capita growth rate and income inequality were endogenous variables. Additionally, stock price index and social status measures were also incorporated. The results indicate that income inequality is inversely related to economic growth. In addition, increase in income inequality arising from higher stock prices constrains growth. Moreover, where social status is determined by income levels, it influences long run growth. Therefore, these results support findings of Persson and Tabellini (1994) and Alesina and Rodrik (1994). ^

Investigation of molecular mechanisms of LKB1 function in Dictyostelium development and stress responses and the function of superoxide dismutase C (SodC) in chemotaxis

The serine/threonine kinase LKB1 is a regulator of critical events including development and stress responses in metazoans. The current study was undertaken to determine the function of LKB1 in Dictyostelium . During multicellular development and in response to stress insult, an apparent increase in the DdLKB1 kinase activity was observed. Depletion of DdLKB1 with a knockdown construct led to aberrant development; a severe reduction in prespore cell differentiation and a precocious induction of prestalk cells, which were reminiscent of cells lacking GSK3, a well known cell-fate switch. Furthermore, DdLKB1 depleted cells displayed lower GSK3 activity than wild type cells in response to cAMP stimulation during development and failed to activate AMPK, a well known LKB1 target in mammals, in response to cAMP and stress insults. These results suggest that DdLKB1 positively regulates both GSK3 and AMPK during Dictyostelium development, and DdLKB1 is necessary for AMPK activation during stress response regulation. No apparent GSK3 activation was observed in response to stress insults. Spatial and temporal regulation of phosphatidylinositol-(3,4,5)-triphosphate (PIP3) along the membrane of polarized cells is important for efficient chemotaxis. A REMI screen for PIP3 suppressors in the absence of stimulation led to the identification of SodC as PIP3 regulator. Consistent with their higher PIP3 levels, sodC− cells showed defects in chemotaxis and exhibited higher intra-cellular superoxide levels. Protein localization studies along with observations from GPI specific PI-PLC treatment of wild-type cells suggested that SodC is a GPI anchored outer-membrane protein. SodC showed superoxide dismutase activity in vitro, and motility defects of sodC− cells can be rescued by expressing the intact SodC but not by the mutant SodC, which has point mutations that affect its dismutase function. Treatment of sodC− cells with LY294002, a pharmacological inhibitor of PI3K, partially rescued the polarization and chemoattractant sensing defects but not motility defects. Consistent with increased intracellular superoxide levels, sodC − cells also exhibited higher basal Ras activity, an upstream regulator of PI3K, which can be suppressed by a cell permeable superoxide scavenger, XTT, indicating that SodC is important in regulation of intracellular superoxide levels thereby regulating the Ras activity and PIP3 levels at the membrane.

Areal and vertical distribution of total soil mercury and total phosphorusin the southern half of water conservation area 3-A, Everglades, Southern Florida

Total soil-mercury and phosphorus concentrations were determined in 64 sites in the southern half of Water Conservation Area 3A, an area of approximately 500 km2 . Surface soil-Hg concentrations ranged from 117 to 300 ng-g-1;total phosphorus concentrations range from 350 to 850 pg~g-1. No consistent north-south or east-west trends are found in the mercury or phosphorus surface concentrations when they are normalized to soil bulk density. Nine sites were used for the determination of the vertical distribution of soilmercury. Vertical profiles of soil-Hg revealed decreasing concentrations with depth and correlated well with phosphorus in soil profiles. Mercury concentrations in soil profiles may be interpreted as an increase in the rate of deposition of mercury in the region in recent decades and/or as postdepositionalmobilization of mercury to surface layers.

Investigation of molecular mechanisms of lkb1 function in dictyostelium development and stress responses and the function of superoxide dismutase c (sodc) in chemotaxis

The serine/threonine kinase LKB1 is a regulator of critical events including development and stress responses in metazoans. The current study was undertaken to determine the function of LKB1 in Dictyostelium. During multicellular development and in response to stress insult, an apparent increase in the DdLKB1 kinase activity was observed. Depletion of DdLKB1 with a knockdown construct led to aberrant development; a severe reduction in prespore cell differentiation and a precocious induction of prestalk cells, which were reminiscent of cells lacking GSK3, a well known cell-fate switch. Furthermore, DdLKB1 depleted cells displayed lower GSK3 activity than wild type cells in response to cAMP stimulation during development and failed to activate AMPK, a well known LKB1 target in mammals, in response to cAMP and stress insults. These results suggest that DdLKB1 positively regulates both GSK3 and AMPK during Dictyostelium development, and DdLKB1 is necessary for AMPK activation during stress response regulation. No apparent GSK3 activation was observed in response to stress insults. Spatial and temporal regulation of phosphatidylinositol-(3,4,5)-triphosphate (PIP3) along the membrane of polarized cells is important for efficient chemotaxis. A REMI screen for PIP3 suppressors in the absence of stimulation led to the identification of SodC as PIP3 regulator. Consistent with their higher PIP3 levels, sodC- cells showed defects in chemotaxis and exhibited higher intra-cellular superoxide levels. Protein localization studies along with observations from GPI specific PI-PLC treatment of wild-type cells suggested that SodC is a GPI anchored outer-membrane protein. SodC showed superoxide dismutase activity in vitro, and motility defects of sodC- cells can be rescued by expressing the intact SodC but not by the mutant SodC, which has point mutations that affect its dismutase function. Treatment of sodC- cells with LY294002, a pharmacological inhibitor of PI3K, partially rescued the polarization and chemoattractant sensing defects but not motility defects. Consistent with increased intracellular superoxide levels, sodC- cells also exhibited higher basal Ras activity, an upstream regulator of PI3K, which can be suppressed by a cell permeable superoxide scavenger, XTT, indicating that SodC is important in regulation of intracellular superoxide levels thereby regulating the Ras activity and PIP3 levels at the membrane.

Effects of Increased Levels of Prenatal Mesotocin on Postnatal Individual Recognition and Stress Responsiveness in Northern bobwhite quail (Colinus Virginianus)

Oxytocin (OT) plays a key role in the mediation of social and stress behaviors across many species; however, the mechanism is still unclear. The present study investigated the influence of prenatal levels of mesotocin (MT; avian homologue of OT) on postnatal social and stress behavior in Northern bobwhite quail. Experiment one determined endogenous levels of MT during prenatal development using an enzyme-linked immunoassay kit. Experiment two examined the influence of increased MT during prenatal development on chicks' individual recognition ability and stress response to a novel environment. Experiment one showed MT levels increased significantly throughout embryonic development. Experiment two showed significant differences in stress behavior for chicks with increased MT during prenatal development; however, no significant differences were found for social behavior. This study suggests MT serves different functions depending on the stage of embryonic development and that increasing MT levels affects postnatal stress behavior, but not social behavior.