A role for glyceraldehyde-3-phosphate dehydrogenase in the development of thermotolerance in Xenopus laevis embryos

During heat shock, Xenopus laevis embryos exhibit an increase in the rate of accumulation of lactate and a loss of ATP relative to non-heat- shocked control embryos. These results suggest that heat shock stimulates a shift in energy metabolism to anaerobic glycolysis while at the same time causing an increase in the demand for ATP. We have evidence indicating that the embryo may meet such demands placed on it by increasing the levels of some glycolytic enzymes. In this report, we show that heat shock stimulates increases in the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase [( EC 1.2.1.12] GAPDH). The specific activity of GAPDH shows a significant increase after heat shock, which correlates with the accumulation of GAPDH in heat-shocked embryos as detected by immunoblotting. Increases in GAPDH-specific activity are variable, however, and are inversely proportional to the levels of specific activity in control embryos; i.e., constitutive enzyme activity. We further analyzed the heat-enhanced accumulation of GAPDH by electrophoretically separating GAPDH isozymes on nondenaturing polyacrylamide gels. Control embryos exhibit a single isozyme of GAPDH, whereas heat-shocked embryos exhibit two isozymes of GAPDH. When these isozymes are labeled with [35S]methionine, separated by nondenaturing gel electrophoresis, and analyzed by fluorography, a heat-shock protein is found to comigrate with the isozyme unique to the heat-shocked sample. Enzyme activity assays at different temperatures suggest that this isozyme has optimum enzymatic activity only at heat-shock temperatures. We have correlated a 35-kD heat-shock protein (hsp35) with GAPDH using the following evidence: this hsp comigrates with GAPDH on one-dimensional SDS polyacrylamide gels; heat-enhanced increases in GAPDH specific activity correlate with hsp35 synthesis; and hsp35 and GAPDH have similar peptide maps. This relationship also provides a compelling explanation for the restriction of hsp35 synthesis to the vegetal hemisphere cells of heat-shocked early gastrulae reported previously (Nickells, R. W., and L. W. Browder. 1985. Dev. Biol. 112:391-395)

Nonpathogenic Free-Living Amoebae in Arkansas Recreational Waters

Selected recreational waters of Arkansas were sampled for pathogenic free-living limax amoebae. Water quality parameters were determined for correlation with amoebic population densities and species diversity. Cultural criteria and animal inoculation revealed no pathogenic strains. The possibility of introduction and/or induction of pathogenic amoebic strains by environmental factors requires further ecological investigations

Local Zeta Functions for Non-degenerate Laurent Polynomials Over p-adic Fields

In this article, we study local zeta functions attached to Laurent polynomials over p-adic fields, which are non-degenerate with respect to their Newton polytopes at infinity. As an application we obtain asymptotic expansions for p-adic oscillatory integrals attached to Laurent polynomials. We show the existence of two different asymptotic expansions for p-adic oscillatory integrals, one when the absolute value of the parameter approaches infinity, the other when the absolute value of the parameter approaches zero. These two asymptotic expansions are controlled by the poles of twisted local zeta functions of Igusa type.Comment: The condition on the critical set on the mapping f considered in Section 2.5 of our article is not sufficient to assure the vanishing of the twisted local zeta functions (for almost all the characters) as we assert in Theorem 3.9. A new condition on the mapping f is provide

Efficient posterior simulation in cointegration models with priors on the cointegration space

A message coming out of the recent Bayesian literature on cointegration is that it is important to elicit a prior on the space spanned by the cointegrating vectors (as opposed to a particular identi…ed choice for these vectors). In this note, we discuss a sensible way of eliciting such a prior. Furthermore, we develop a collapsed Gibbs sampling algorithm to carry out e¢ cient posterior simulation in cointegration models. The computational advantages of our algorithm are most pronounced with our model, since the form of our prior precludes simple posterior simulation using conventional methods (e.g. a Gibbs sampler involves non-standard posterior conditionals). However, the theory we draw upon implies our algorithm will be more e¢ cient even than the posterior simulation methods which are used with identi…ed versions of cointegration models

Bayesian inference in the time varying cointegration model

There are both theoretical and empirical reasons for believing that the parameters of macroeconomic models may vary over time. However, work with time-varying parameter models has largely involved Vector autoregressions (VARs), ignoring cointegration. This is despite the fact that cointegration plays an important role in informing macroeconomists on a range of issues. In this paper we develop time varying parameter models which permit coin- tegration. Time-varying parameter VARs (TVP-VARs) typically use state space representations to model the evolution of parameters. In this paper, we show that it is not sensible to use straightforward extensions of TVP-VARs when allowing for cointegration. Instead we develop a speci…cation which allows for the cointegrating space to evolve over time in a manner comparable to the random walk variation used with TVP-VARs. The properties of our approach are investigated before developing a method of posterior simulation. We use our methods in an empirical investigation involving a permanent/transitory variance decomposition for inflation

Bayesian inference in a cointegrating panel data model

This paper develops methods of Bayesian inference in a cointegrating panel data model. This model involves each cross-sectional unit having a vector error correction representation. It is flexible in the sense that different cross-sectional units can have different cointegration ranks and cointegration spaces. Furthermore, the parameters which characterize short-run dynamics and deterministic components are allowed to vary over cross-sectional units. In addition to a noninformative prior, we introduce an informative prior which allows for information about the likely location of the cointegration space and about the degree of similarity in coefficients in different cross-sectional units. A collapsed Gibbs sampling algorithm is developed which allows for efficient posterior inference. Our methods are illustrated using real and artificial data

On the evolution of monetary policy

This paper investigates the evolution of monetary policy in the U.S. using a standard set of macroeconomic variables. Many recent papers have addressed the issue of whether the monetary transmission mechanism has changed (e.g. due to the Fed taking a more aggressive stance against in‡ation) or whether apparent changes are simply due to changes in the volatility of exogenous shocks. A subsidiary question is whether any such changes have been gradual or abrupt. In this paper, we shed light on these issues using a mixture innovation model which extends the class of time varying Vector Autoregressive models with stochastic volatility which have been used in the past. The advantage of our extension is that it allows us to estimate whether, where, when and how parameter change is occurring (as opposed to assuming a particular form of parameter change). Our empirical results strongly indicate that the transmission mechanism, the volatility of exogenous shocks and the correlations between exogenous shocks are all changing (albeit at different times and to di¤erent extents) Furthermore, evolution of parameters is gradual