Reactive oxygen species (ROS) production is one of the main mechanisms used to kill microbes during innate immune response. D-lactic acid, which is augmented during acute ruminal acidosis, reduces platelet activating factor (PAF)-induced ROS production and L-selectin shedding in bovine neutrophils in vitro. This study was conducted to investigate whether acute ruminal acidosis induced by acute oligofructose overload in heifers interferes with ROS production and L-selectin shedding in blood neutrophils. Blood neutrophils and plasma were obtained by jugular venipuncture, while ruminal samples were collected using rumenocentesis. Lactic acid from plasma and ruminal samples was measured by HPLC. PAF-induced ROS production and L-selectin shedding were measured in vitro in bovine neutrophils by a luminol chemiluminescence assay and flow cytometry, respectively. A significant increase in ruminal and plasma lactic acid was recorded in these animals. Specifically, a decrease in PAF-induced ROS production was observed 8 h after oligofructose overload, and this was sustained until 48 h post oligofructose overload. A reduction in PAF-induced L-selectin shedding was observed at 16 h and 32 h post oligofructose overload. Overall, the results indicated that neutrophil PAF responses were altered in heifers with ruminal acidosis, suggesting a potential dysfunction of the innate immune response.

No abstract

Copula models have become increasingly popular for modelling the dependence structure in multivariate survival data. The two-parameter Archimedean family of Power Variance Function (PVF) copulas includes the Clayton, Positive Stable (Gumbel) and Inverse Gaussian copulas as special or limiting cases, thus offers a unified approach to fitting these important copulas. Two-stage frequentist procedures for estimating the marginal distributions and the PVF copula have been suggested by Andersen (Lifetime Data Anal 11:333-350, 2005), Massonnet et al. (J Stat Plann Inference 139(11):3865-3877, 2009) and Prenen et al. (J R Stat Soc Ser B 79(2):483-505, 2017) which first estimate the marginal distributions and conditional on these in a second step to estimate the PVF copula parameters. Here we explore an one-stage Bayesian approach that simultaneously estimates the marginal and the PVF copula parameters. For the marginal distributions, we consider both parametric as well as semiparametric models. We propose a new method to simulate uniform pairs with PVF dependence structure based on conditional sampling for copulas and on numerical approximation to solve a target equation. In a simulation study, small sample properties of the Bayesian estimators are explored. We illustrate the usefulness of the methodology using data on times to appendectomy for adult twins in the Australian NH&MRC Twin registry. Parameters of the marginal distributions and the PVF copula are simultaneously estimated in a parametric as well as a semiparametric approach where the marginal distributions are modelled using Weibull and piecewise exponential distributions, respectively.

Whale-watching is one of the fastest growing ecotourism industries and involves the observation of endangered wild cetacean species. However, this growth has raised concerns because of the negative effects this activity may have on the behavior and survival of focal species. Hence, detecting the effects of this activity requires sensitive analytical methods allowing the implementation of regulations to protect cetacean welfare. We compared the performance of different hypothesis tests from classical and Bayesian approaches to detect whale-watching effects on humpback whale (Megaptera novaeangliae) behavior. From a cliff located 31 m above sea level in northern Peru, we measured breathing frequency, surface time, long dive duration, directness index (i.e., path linearity), and swimming speed of humpback whales before, during, and after encounters with whale-watching boats. During 167 hours of observation, we tracked 180 humpback whale groups; 43% of groups had calves and 57% did not. Inference by null-hypothesis testing indicated significant changes only in directness index after boat encounters in groups with a calf. Other methods of inference detected moderate behavior responses as increments in the number of adult breaths, swimming speed, and dive intervals for adults and calves. Whale-watching regulations must be implemented in Peru to regulate number of boats, distance to whales, approximate speed, and time observing humpback whales. Whale-watching of humpback whales with calves should be avoided. Ó 2018 The Wildlife Society.

In this paper, an algorithm is developed to compute estimates for parameters in destructive weighted Poisson cure rate models. It is shown, analytically, the robustness of the procedure with respect to the maximization of the observed likelihood function. The approach allows a simple implementation of different distributions for non-destroyed concurrent causes. The performance of the method is evaluated through simulation studies and by analysing a real data set related to patients with malignant melanoma.