Type IV Secretion-Dependent Activation of Host MAP Kinases Induces an Increased Proinflammatory Cytokine Response to Legionella pneumophila

The immune system must discriminate between pathogenic and nonpathogenic microbes in order to initiate an appropriate response. Toll-like receptors (TLRs) detect microbial components common to both pathogenic and nonpathogenic bacteria, whereas Nod-like receptors (NLRs) sense microbial components introduced into the host cytosol by the specialized secretion systems or pore-forming toxins of bacterial pathogens. The host signaling pathways that respond to bacterial secretion systems remain poorly understood. Infection with the pathogen Legionella pneumophila, which utilizes a type IV secretion system (T4SS), induced an increased proinflammatory cytokine response compared to avirulent bacteria in which the T4SS was inactivated. This enhanced response involved NF-κB activation by TLR signaling as well as Nod1 and Nod2 detection of type IV secretion. Furthermore, a TLR- and RIP2-independent pathway leading to p38 and SAPK/JNK MAPK activation was found to play an equally important role in the host response to virulent L. pneumophila. Activation of this MAPK pathway was T4SS-dependent and coordinated with TLR signaling to mount a robust proinflammatory cytokine response to virulent L. pneumophila. These findings define a previously uncharacterized host response to bacterial type IV secretion that activates MAPK signaling and demonstrate that coincident detection of multiple bacterial components enables immune discrimination between virulent and avirulent bacteria

Evaluación de la calidad del adn espermático en camélidos sudamericanos y otras especies domésticas

Abnormalities in sperm genetic material can be expressed as maturation or nuclear condensation defects, DNA damage or breakdown and chromosomal abnormalities. Routine semen evaluation (sperm motility, concentration, viability, membrane function and morphology) does not reflect sperm DNA quality. This becomes important when applying assisted reproductive techniques, especially intracytoplasmic sperm injection, in which sperm with abnormal genomes can reach the oocyte’s genetic material. Three factors have been suggested to be involved in the etiology of DNA damage: oxidative stress, chromatin packaging anomalies and apoptosis. Various techniques have been used to study DNA defects. In general, DNA evaluation techniques can be divided into two groups: those that evaluate the degree of chromatin condensation or compactation and those that measure the degree of DNA fragmentation. Many of these techniques are laborious, costly and some depend on enzymes whose activity and accessibility to DNA fragments can be irregular. In this article, the development and setting up of various techniques to evaluate sperm chromatin in South American Camelids (SACs) and other domestic species is commented on

Analysis of the effect of trees on block propagation using a DEM model: implications for rockfall modelling

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVINInternational audienceThe objective of this research was to use numerical models based on mechanical approaches to improve the integration of the protective role of forests against rockfall into block propagation models. A model based on the Discrete Element Method (DEM) was developed to take into account the complex mechanical processes involved during the impact of a block on a tree. This modelling approach requires the definition of many input parameters and cannot be directly integrated into block propagation models. A global sensitivity analysis identified the leading parameters of the block kinematics after impact (i.e. block energy reduction, trajectory changes and rotational velocity): the impact velocity, the tree diameter and the impact point horizontal location (i.e. eccentricity). Comparisons with the previous experimental and numerical studies of block impacts on trees demonstrated the applicability of the DEM model and showed some of the limitations of earlier approaches. Our sensitivity analysis highlights the significant influence of the impact velocity on the reduction of the block's kinetic energy. Previous approaches usually also focus on parameters such as impact height, impact vertical incidence and tree species, whose importance is only minor according to the present results. This suggests that the integration of forest effects into block propagation models could be both improved and simplified. The DEM model can also be used as an alternative to classical approaches for the integration of forest effects by directly coupling it with block propagation models. This direct coupling only requires the additional definition of the location and the diameter of each tree. Indeed, the input parameters related to the mechanical properties of the stem and the block/stem interaction in the DEM model can be set to average values because they are not leading parameters. The other input parameters are already defined or calculated in the block propagation model