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PH Model (ph + model)
Selected AbstractsComparison of models for genetic evaluation of survival traits in dairy cattle: a simulation studyJOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 2 2008J. Jamrozik Summary Three models for the analysis of functional survival data in dairy cattle were compared using stochastic simulation. The simulated phenotype for survival was defined as a month after the first calving (from 1 to 100) in which a cow was involuntarily removed from the herd. Parameters for simulation were based on survival data of the Canadian Jersey population. Three different levels of heritability of survival (0.100, 0.050 and 0.025) and two levels of numbers of females per generation (2000 or 4000) were considered in the simulation. Twenty generations of random mating and selection (on a second trait, uncorrelated with survival) with 20 replicates were simulated for each scenario. Sires were evaluated for survival of their daughters by three models: proportional hazard (PH), linear multiple-trait (MT), and random regression (RR) animal models. Different models gave different ranking of sires with respect to survival of their daughters. Correlations between true and estimated breeding values for survival to five different points in a cow's lifetime after the first calving (120 and 240 days in milk after first, second, third and fourth calving) favoured the PH model, followed by the RR model evaluations. Rankings of models were independent of the heritability level, female population size and sire progeny group size (20 or 100). The RR model, however, showed a slight superiority over MT and PH models in predicting the proportion of sire's daughters that survived to the five different end-points after the first calving. [source] Deceleration of Regenerative Response Improves the Outcome of Rat with Massive HepatectomyAMERICAN JOURNAL OF TRANSPLANTATION, Issue 7 2010M. Ninomiya Small residual liver volume after massive hepatectomy or partial liver transplantation is a major cause of subsequent liver dysfunction. We hypothesize that the abrupt regenerative response of small remnant liver is responsible for subsequent deleterious outcome. To slow down the regenerative speed, NS-398 (ERK1/2 inhibitor) or PD98059 (selective MEK inhibitor) was administered after 70% or 90% partial hepatectomy (PH). The effects of regenerative speed on liver morphology, portal pressure and survival were assessed. In the 70% PH model, NS-398 treatment suppressed the abrupt replicative response of hepatocytes during the early phase of regeneration, although liver volume on day 7 was not significantly different from that of the control group. Immunohistochemical analysis for CD31 (for sinusoids) and AGp110 (for bile canaliculi) revealed that lobular architectural disturbance was alleviated by NS-398 treatment. In the 90% PH model, administration of NS-398 or PD98059, but not hepatocyte growth factor, significantly enhanced survival. The abrupt regenerative response of small remnant liver is suggested to be responsible for intensive lobular derangement and subsequent liver dysfunction. The suppression of MEK/ERK signaling pathway during the early phase after hepatectomy makes the regenerative response linear, and improves the prognosis for animals bearing a small remnant liver. [source] Growth response of the bacterial community to pH in soils differing in pHFEMS MICROBIOLOGY ECOLOGY, Issue 1 2010David Fernández-Calviño Abstract The effect of pH on the instantaneous growth of soil bacterial communities was studied in five soils with different pH (4.5,7.8) using leucine (Leu) and thymidine (TdR) incorporation. The pH dependency of bacterial growth was modelled using three different unimodal functions, and the pHopt for growth and the pH range in which growth was >50% of the optimal growth were compared. Leu and TdR incorporation yielded very similar results. The best fits were obtained using a third-degree polynomial function and the cardinal pH model. However, a simple second-degree function was adequate in most cases, yielding very similar pHopt values to the other two models. Bacterial growth was highly influenced by pH, showing optimum growth at a pH related to the soil pH. The lowest pHopt was found in the most acidic soil and the highest pHopt in the soil with the highest pH. The pHopt for bacterial growth was close to the soil pH measured in water, but higher (0.7,2.1 units) than the pH measured with 0.1 M KCl. The pH range in which bacterial growth was >50% of that at optimum was, on average, 1.7 units below and above the optimum pH. [source] Scale-up from shake flasks to fermenters in batch and continuous mode with Corynebacterium glutamicum on lactic acid based on oxygen transfer and pHBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2007Juri M. Seletzky Abstract Scale-up from shake flasks to fermenters has been hampered by the lack of knowledge concerning the influence of operating conditions on mass transfer, hydromechanics, and power input. However, in recent years the properties of shake flasks have been described with empirical models. A practical scale-up strategy for everyday use is introduced for the scale-up of aerobic cultures from shake flasks to fermenters in batch and continuous mode. The strategy is based on empirical correlations of the volumetric mass transfer coefficient (kLa) and the pH. The accuracy of the empirical kLa correlations and the assumptions required to use these correlations for an arbitrary biological medium are discussed. To determine the optimal pH of the culture medium a simple laboratory method based on titration curves of the medium and a mechanistic pH model, which is solely based on the medium composition, is applied. The effectiveness of the scale-up strategy is demonstrated by comparing the behavior of Corynebacterium glutamicum on lactic acid in shake flasks and fermenters in batch and continuous mode. The maximum growth rate (µmax,=,0.32 h,1) and the oxygen substrate coefficient (,=,0.0174 mol/l) of C. glutamicum on lactic acid were equal for shake flask, fermenter, batch, and continuous cultures. The biomass substrate yield was independent of the scale, but was lower in batch cultures (YX/S,=,0.36 g/g) than in continuous cultures (YX/S,=,0.45 g/g). The experimental data (biomass, respiration, pH) could be described with a simple biological model combined with a mechanistic pH model. Biotechnol. Bioeng. 2007; 98: 800,811. © 2007 Wiley Periodicals, Inc. [source] | |||||||||||||