The role of calcium and calmodulin in the response of roots to gravity

There is general agreement that, in roots, the primary detection of the gravitropic signal occurs in the columella cells of the cap and that this results in the generation of a signal that moves into the elongation zone causing the asymmetric growth that leads to downward curvature. Recent work has generated considerable evidence that indicates that auxin is the ultimate mediator of differential growth during root (and shoot) gravitropism. Our studies of the time course of curvature, auxin redistribution and/or adaptation, and electrical potential changes in maize roots have led to the following generalizations: (1) downward curvature begins 18 to 32 min following gravistimulation; (2) asymmetric auxin redistribution across the root cap begins at about the same time as curvature or perhaps slight earlier; (3) there is a lag of approx. 15 min in the response of roots to applied auxin; and (4) gravi-induced changes in intracellular potentials of cortical cells within the elongation zone occur within 30 s following stimulation

Labor Productivity During the Great Depression

In a recent paper, Bemanke and Parkinson (1991) studied interwar U.S. manufacturing data with the objective of assessing competing theories of the business cycle. An important finding was that short-run increasing returns to Labor (SRIRL), or procyclical labor productivity, was at least as strong during the Great Depression as in the postwar period. The authors conclude that this information casts further doubt on the real business cycle explanation of economic fluctuations. The purpose of this note is to point out that, within the data set analyzed by Bemanke and Parkinson (20% of the manufacturing sector), labor productivity during the Great Depression (1928:III to 1933:1) was procyclical in some industries and countercyclical in others. Furthermore, our measure of labor productivity for the entire manufacturing sector during this period was countercyclical. We conclude that the evidence is not favorable toward the hypothesis that large, negative aggregate demand shocks pushed the 1929-33 economy down a static, neoclassical production function. Another possibility is that firms which typically hoarded labor during recessions chose not to do so during the 1929-33 period.

Money, sticky wages, and the Great Depression

This paper examines the ability of a simple stylized general equilibrium model that incorporates nominal wage rigidity to explain the magnitude and persistence of the Great Depression in the United States. The impulses to our analysis are money supply shocks. The Taylor contracts model is surprisingly successful in accounting for the behavior of major macroaggregates and real wages during the downturn phase of the Depression, i.e., from 1929:3 through mid-1933. Our analysis provides support for the hypothesis that a monetary contraction operating through a sticky wage channel played a significant role in accounting for the downturn, and also provides an interesting refinement to this explanation. In particular, both the absolute severity of the Depression's downturn and its relative severity compared to the 1920-21 recession are likely attributable to the price decline having a much larger unanticipated component during the Depression, as well as less flexible wage-setting practices during this latter period. Another finding casts doubt on explanations for the 1933-36 recovery that rely heavily on the substantial remonetization that began in 1933.Money supply ; Wages ; Depressions

Genetic parameters for animal mortality in pasture-based, seasonal-calving dairy and beef herds

peer-reviewedIn the absence of informative health and welfare phenotypes, breeding for reduced animal mortality could improve overall health and welfare, provided genetic variability in animal mortality exists. The objective of the present study was to estimate genetic (and other) variance components for animal mortality in pasture-based, seasonal-calving dairy and beef herds across multiple life stages as well as to quantify the genetic relationship in mortality among life stages. National mortality records were available for all cattle born in the Republic of Ireland. Cattle were grouped into three life stages based on age (0 to 30 days, 31 to 365 days, 366 to 1095 days) whereas females with ≥1 calving event were also grouped into five life stages, based on parity number (1, 2, 3, 4, and 5), considering both the initial 60 days of lactation and a cow's entire lactation period, separately. The mean mortality prevalence ranged from 0.70 to 5.79% in young animals and from 0.53 to 3.86% in cows. Variance components and genetic correlations were estimated using linear mixed models using 21,637 to 100,993 records. Where heritability estimates were different from zero, direct heritability estimates for mortality in young animals (≤1095 days) ranged from 0.006 to 0.040, whereas the genetic standard deviation ranged from 0.015 to 0.034. The contribution of a maternal genetic effect to mortality in young animals was evident up to 30 days of age in dairy herds, but this was only the case in preliminary analysis of stillbirths in beef herds. Based on the estimated genetic standard deviation in the present study, the incidence of mortality in young animals could be reduced through breeding by up to 3.4 percentage units per generation. For cows, direct heritability estimates for mortality, where different from zero, ranged from 0.003 to 0.049. The genetic standard deviation for mortality in cows ranged from 0.005 to 0.016 during the initial 60 days of lactation and ranged from 0.011 to 0.032 during the cow's entire lactation. Genetic correlations among the age groups as well as between the age groups and cow parities had high standard errors. Genetic correlations among the cow parities were moderate to strongly positive (ranging from 0.66 to 0.99) and mostly different from zero. Results from the present study can be used to inform genetic evaluations for mortality in young animals and in cows as well as the potential genetic gain achievable

Root gravitropism in maize and Arabidopsis

Research during the period 1 March 1992 to 30 November 1993 focused on improvements in a video digitizer system designed to automate the recording of surface extension in plants responding to gravistimulation. The improvements included modification of software to allow detailed analysis of localized extension patterns in roots of Arabidopsis. We used the system to analyze the role of the postmitotic isodiametric growth zone (a region between the meristem and the elongation zone) in the response of maize roots to auxin, calcium, touch and gravity. We also used the system to analyze short-term auxin and gravitropic responses in mutants of Arabidopsis with reduced auxin sensitivity. In a related project, we studied the relationship between growth rate and surface electrical currents in roots by examining the effects of gravity and thigmostimulation on surface potentials in maize roots

Historical perspective on astrophysical MHD simulations

This contribution contains the introductory remarks that I presented at IAU Symposium 270 on ``Computational Star Formation" held in Barcelona, Spain, May 31 -- June 4, 2010. I discuss the historical development of numerical MHD methods in astrophysics from a personal perspective. The recent advent of robust, higher order-accurate MHD algorithms and adaptive mesh refinement numerical simulations promises to greatly improve our understanding of the role of magnetic fields in star formation.Comment: 11 pages, 5 figures, in "Computational Star Formation" held in Barcelona, Spain, May 31 - June 4, 2010", Eds. J. Alves, B. G. Elmegreen, J. M. Girart, V. Trimbl

Nutrients, Eutrophic Response, and Fish Anomalies in the Little Miami River, Ohio

Author Institution: Dept of Biological Sciences, Northern Kentucky University, Highland Heights, KYAuthor Institution: University of Cincinnati, Dept of Biological Sciences, Cincinnati, OHWe documented the eutrophic and chemical environment in the Little Miami River (LMR) to better understand the interaction between eutrophication, eutrophic response variables, and the health of aquatic organisms. Total phosphorus (TP) and soluble reactive phosphorus (SRP), nitrogen, dissolved oxygen (DO), benthic and sestonic algal biomass, benthic phosphorus storage, aqueous trace metals (Cd, Cr, Cu, Se, Zn), heavy metals (Al, Fe, Mn) and major cations (Ca, K, Mg, Na, Si) were analyzed at twelve sites over two summers. Results showed excess TP (>70 ug/L, p <0.05) and SRP (≥62.5 ug/L, p <0.05), borderline nuisance benthic algal biomass (mg/L chlorophyll a/m2) (periphyton: mean = 73.8 +/- 74.2, n = 125; Cladophora: mean = 216.7 +/- 380.7, n = 54), excess benthic phosphorus storage (mg P/m2) (periphyton: mean = 45.5 +/- 23.2, n = 64; Cladophora: mean = 129.3 +/- 224, n = 52), and high daytime DO (mean = 9.1 +/- 1.5 mg/L, n = 132). Previous studies showed aqueous phosphorus concentration and diurnal DO swings were positively correlated with fish anomalies (OEPA 1995, 2000). In this study, however, periphyton phosphorus (P) was the only eutrophic response variable to correlate with the distribution of fish anomalies reported by OEPA in 1995 and 2000, and the association was negative (R2 = 0.143, p = 0.002, m = -1.634, df = 1, 62). We concluded that aqueous nutrients, eutrophic response variables, and/or water chemistry alone did not explain the occurrence of fish anomalies in the LMR