A congestion model for cell migration

This paper deals with a class of macroscopic models for cell migration in a saturated medium for two-species mixtures. Those species tend to achieve some motion according to a desired velocity, and congestion forces them to adapt their velocity. This adaptation is modelled by a correction velocity which is chosen minimal in a least-square sense. We are especially interested in two situations: a single active species moves in a passive matrix (cell migration) with a given desired velocity, and a closed-loop Keller-Segel type model, where the desired velocity is the gradient of a self-emitted chemoattractant. We propose a theoretical framework for the open-loop model (desired velocities are defined as gradients of given functions) based on a formulation in the form of a gradient flow in the Wasserstein space. We propose a numerical strategy to discretize the model, and illustrate its behaviour in the case of a prescribed velocity, and for the saturated Keller-Segel model

Integrating pastoralism into policy process: Enhancing pastoral adaptation and sustainable development

This brief is based on analysis of how past and present policy processes affect the capacity of pastoralists to adapt to climate change in Senegal, using Ngnith Municipality in the delta of the Senegal River as a case study. Drawing on a combination of literature review and original fieldwork. Our conclusions lead us to provide some recommendations which need to be more integrated in future policy-making process in order to avoid maladaptation and social inequity

Pastoral adaptation and policy environment: How discourses shape knowledge, policy and adaptation

The purpose of this paper is to analyze how the policy environment in Senegal influences pastoral climate change adaptation. The analysis of the link between policy environment and pastoral adaptation is based on a case study in the Ngnith municipality of the Senegal River delta and other localities in the delta. We argue that past policies have both changed the ecological and social systems and also changed the viability of livelihoods, especially by integrating national and international markets supported by national policies and leading to land competition, increasing the pastoral vulnerability. The present policy environment shapes the pastoral adaptation because policy processes lead to new power relations that marginalized pastoralists. Changes in the stakeholders and their uneven distribution of power leads to inequalities in terms of land allocation opportunities and limitation of the flexible livelihoods access which is primordial of pastoralism resilience. In conclusion, we argue that unpacking the political dimension of social-environment interactions is helpful in understanding the evolution of pastoralists’ capacity to adapt to climate change

Environmentally induced functional shifts in phytoplankton and their potential consequences for ecosystem functioning

Phytoplanktonic organisms are particularly sensitive to environmental change, and, as they represent a direct link between abiotic and biotic compartments within the marine food web, changes in the functional structure of phytoplankton communities can result in profound impacts on ecosystem functioning. Using a trait-based approach, we examined changes in the functional structure of the southern North Sea phytoplankton over the past five decades in relation to environmental conditions. We identified a shift in functional structure between 1998 and 2004 which coincides with a pronounced increase in diatom and decrease in dinoflagellate abundances, and we provide a mechanistic explanation for this taxonomic change. Early in the 2000s, the phytoplankton functional structure shifted from slow growing, autumn blooming, mixotrophic organisms, towards earlier blooming and faster-growing microalgae. Warming and decreasing dissolved phosphorus concentrations were linked to this rapid reorganization of the functional structure. We identified a potential link between this shift and dissolved nutrient concentrations, and we hypothesise that organisms blooming early and displaying high growth rates efficiently take up nutrients which then are no longer available to late bloomers. Moreover, we identified that the above-mentioned functional change may have bottom-up consequences, through a food quality-driven negative influence on copepod abundances. Overall, our study highlights that, by altering the phytoplankton functional composition, global and regional changes may have profound long-term impacts on coastal ecosystems, impacting both food-web structure and biogeochemical cycles

An integrated multiple driver mesocosm experiment reveals the effect of global change on planktonic food web structure

AbstractGlobal change puts coastal marine systems under pressure, affecting community structure and functioning. Here, we conducted a mesocosm experiment with an integrated multiple driver design to assess the impact of future global change scenarios on plankton, a key component of marine food webs. The experimental treatments were based on the RCP 6.0 and 8.5 scenarios developed by the IPCC, which were Extended (ERCP) to integrate the future predicted changing nutrient inputs into coastal waters. We show that simultaneous influence of warming, acidification, and increased N:P ratios alter plankton dynamics, favours smaller phytoplankton species, benefits microzooplankton, and impairs mesozooplankton. We observed that future environmental conditions may lead to the rise of Emiliania huxleyi and demise of Noctiluca scintillans, key species for coastal planktonic food webs. In this study, we identified a tipping point between ERCP 6.0 and ERCP 8.5 scenarios, beyond which alterations of food web structure and dynamics are substantial.</jats:p

Autonomous Pareto Front Scanning using an Adaptive Multi-Agent System for Multidisciplinary Optimization

Multidisciplinary Design Optimization (MDO) problems can have a unique objective or be multi-objective. In this paper, we are interested in MDO problems having at least two conflicting objectives. This characteristic ensures the existence of a set of compromise solutions called Pareto front. We treat those MDO problems like Multi-Objective Optimization (MOO) problems. Actual MOO methods suffer from certain limitations, especially the necessity for their users to adjust various parameters. These adjustments can be challenging, requiering both disciplinary and optimization knowledge. We propose the use of the Adaptive Multi-Agent Systems technology in order to automatize the Pareto front obtention. ParetOMAS (Pareto Optimization Multi-Agent System) is designed to scan Pareto fronts efficiently, autonomously or interactively. Evaluations on several academic and industrial test cases are provided to validate our approach

Viral sequence variation in chronic carriers of hepatitis C virus has a low impact on liver steatosis.: HCV variability and steatosis

International audienceMost clinical studies suggest that the prevalence and severity of liver steatosis are higher in patients infected with hepatitis C virus (HCV) genotype 3 than in patients infected with other genotypes. This may reflect the diversity and specific intrinsic properties of genotype 3 virus proteins. We analyzed the possible association of particular residues of the HCV core and NS5A proteins known to dysregulate lipid metabolism with steatosis severity in the livers of patients chronically infected with HCV. We used transmission electron microscopy to quantify liver steatosis precisely in a group of 27 patients, 12 of whom were infected with a genotype 3 virus, the other 15 being infected with viruses of other genotypes. We determined the area covered by lipid droplets in liver tissues and analyzed the diversity of the core and NS5A regions encoded by the viral variants circulating in these patients. The area covered by lipid droplets did not differ significantly between patients infected with genotype 3 viruses and those infected with other genotypes. The core and NS5A protein sequences of the viral variants circulating in patients with mild or severe steatosis were evenly distributed throughout the phylogenic trees established from all the collected sequences. Thus, individual host factors seem to play a much greater role than viral factors in the development of severe steatosis in patients chronically infected with HCV, including those infected with genotype 3 viruses

Type-3 Secretion System-induced pyroptosis protects Pseudomonas against cell-autonomous immunity

Inflammasome-induced pyroptosis comprises a key cell-autonomous immune process against intracellular bacteria, namely the generation of dying cell structures. These so-called pore-induced intracellular traps (PITs) entrap and weaken intracellular microbes. However, the immune importance of pyroptosis against extracellular pathogens remains unclear. Here, we report that Type-3 secretion system (T3SS)-expressing Pseudomonas aeruginosa ( P. aeruginosa ) escaped PIT immunity by inducing a NLRC4 inflammasome-dependent macrophage pyroptosis response in the extracellular environment. To the contrary, phagocytosis of Salmonella Typhimurium promoted NLRC4-dependent PIT formation and the subsequent bacterial caging. Remarkably, T3SS-deficient Pseudomonas were efficiently sequestered within PIT-dependent caging, which favored exposure to neutrophils. Conversely, both NLRC4 and caspase-11 deficient mice presented increased susceptibility to T3SS-deficient P. aeruginosa challenge, but not to T3SS-expressing P. aeruginosa. Overall, our results uncovered that P. aeruginosa uses its T3SS to overcome inflammasome-triggered pyroptosis, which is primarily effective against intracellular invaders. Importance Although innate immune components confer host protection against infections, the opportunistic bacterial pathogen Pseudomonas aeruginosa ( P. aeruginosa ) exploits the inflammatory reaction to thrive. Specifically the NLRC4 inflammasome, a crucial immune complex, triggers an Interleukin (IL)-1β and -18 deleterious host response to P. aeruginosa . Here, we provide evidence that, in addition to IL-1 cytokines, P. aeruginosa also exploits the NLRC4 inflammasome-induced pro-inflammatory cell death, namely pyroptosis, to avoid efficient uptake and killing by macrophages. Therefore, our study reveals that pyroptosis-driven immune effectiveness mainly depends on P. aeruginosa localization. This paves the way toward our comprehension of the mechanistic requirements for pyroptosis effectiveness upon microbial infections and may initiate targeted approaches in order to ameliorate the innate immune functions to infections. Graphical abstract Macrophages infected with T3SS-expressing P. aeruginosa die in a NLRC4-dependent manner, which allows bacterial escape from PIT-mediated cell-autonomous immunity and neutrophil efferocytosis. However, T3SS-deficient P. aeruginosa is detected by both NLRC4 and caspase-11 inflammasomes, which promotes bacterial trapping and subsequent efferocytosis of P. aeruginosa -containing-PITs by neutrophils

Identification of a novel PPARβ/δ/miR-21-3p axis in UV-induced skin inflammation.

Although excessive exposure to UV is widely recognized as a major factor leading to skin perturbations and cancer, the complex mechanisms underlying inflammatory skin disorders resulting from UV exposure remain incompletely characterized. The nuclear hormone receptor PPARβ/δ is known to control mouse cutaneous repair and UV-induced skin cancer development. Here, we describe a novel PPARβ/δ-dependent molecular cascade involving TGFβ1 and miR-21-3p, which is activated in the epidermis in response to UV exposure. We establish that the passenger miRNA miR-21-3p, that we identify as a novel UV-induced miRNA in the epidermis, plays a pro-inflammatory function in keratinocytes and that its high level of expression in human skin is associated with psoriasis and squamous cell carcinomas. Finally, we provide evidence that inhibition of miR-21-3p reduces UV-induced cutaneous inflammation in ex vivo human skin biopsies, thereby underlining the clinical relevance of miRNA-based topical therapies for cutaneous disorders