Neonate Intestinal Immune Response to CpG Oligodeoxynucleotide Stimulation

Background: The development of mucosal vaccines is crucial to efficiently control infectious agents for which mucosae are the primary site of entry. Major drawbacks of these protective strategies are the lack of effective mucosal adjuvant. Synthetic oligodeoxynucleotides that contain several unmethylated cytosine-guanine dinucleotide (CpG-ODN) motifs are now recognized as promising adjuvants displaying mucosal adjuvant activity through direct activation of TLR9-expressing cells. However, little is known about the efficacy of these molecules in stimulating the intestinal immune system in neonates. Methodology/Principal Findings: First, newborn mice received CpG-ODN orally, and the intestinal cytokine and chemokine response was measured. We observed that oral administration of CpG-ODN induces CXC and CC chemokine responses and a cellular infiltration in the intestine of neonates as detected by immunohistochemistry. We next compared the efficiency of the oral route to intraperitoneal administration in stimulating the intestinal immune responses of both adults and neonates. Neonates were more responsive to TLR9-stimulation than adults whatever the CpG-ODN administration route. Their intestinal epithelial cells (IECs) indirectly responded to TLR9 stimulation and contributed to the CXC chemokine response, whereas other TLR9-bearing cells of the lamina-propria produced CC chemokines and Th1-type cytokines. Moreover, we showed that the intestine of adult exhibited a significantly higher level of IL10 at homeostasis than neonates, which might be responsible for the unresponsiveness to TLR9-stimulation, as confirmed by our findings in IL10-deficient mice. Conclusions/Significance: This is the first report that deciphers the role played by CpG-ODN in the intestine of neonates. This work clearly demonstrates that an intraperitoneal administration of CpG-ODN is more efficient in neonates than in adults to stimulate an intestinal chemokine response due to their lower IL-10 intestinal level. In addition we report the efficiency of the oral route at inducing intestinal chemokine responses in neonate that might be taken into consideration for further vaccine development against neonatal diseases

Terranimo® – ein webbasiertes Modell zur Abschätzung des Bodenverdichtungsrisikos

Um die Druckverhältnisse unter Landmaschinen zu simulieren und das Bodenverdichtungsrisiko einschätzen zu können, wurde das webbasierte Modell Terranimo® entwickelt. Darin kann mithilfe von verfügbaren Reifenkennwerten und in Abhängigkeit von der Oberbodenfestigkeit die Kontaktfläche und die Druckverteilung zwischen Reifen und Boden beschrieben werden. Mithilfe von Pedotransferfunktionen wird die Bodenfestigkeit (Vorbelastung) vom Tongehalt und der Saugspannung im Boden abgeleitet. Das Verdichtungsrisiko wird durch den Vergleich von Bodenfestigkeit und ausgeübtem Bodendruck abgeschätzt: Bleibt der durch die Landmaschine ausgeübte Bodendruck unterhalb der aktuellen Bodenfestigkeit, so können das Verdichtungsrisiko minimiert und negative Veränderungen der Bodenstruktur – und somit der Bodenfunktionen – vermieden werden.Based on experimental data from wheeling experiments, a web-based model for the simulation of stress and the evaluation of the soil compaction risk under agricultural machinery named Terranimo® has been developed. Terranimo® incorporates a model for prediction of contact area, shape and stress distribution in the tyre soil interface from wheel load and readily-available tyre parameters and the topsoil strength. In Terranimo® pedotransfer functions are used to estimate soil strength from clay content and matric potential. Principally, by limiting the imposed stress to below soil strength, the risk of soil compaction and undesirable changes of soil structure – and hence soil functions – can be minimized

An interdisciplinary approach towards improved understanding of soil deformation during compaction

International audienceSoil compaction not only reduces available pore volume in which fluids are stored, but it alters the arrangement of soil constituents and pore geometry, thereby adversely impacting fluid transport and a range of soil ecological functions. Quantitative understanding of stress transmission and deformation processes in arable soils remains limited. Yet such knowledge is essential for better predictions of effects of soil management practices such as agricultural field traffic on soil functioning. Concepts and theory used in agricultural soil mechanics (soil compaction and soil tillage) are often adopted from conventional soil mechanics (e.g. foundation engineering). However, in contrast with standard geotechnical applications, undesired stresses applied by agricultural tyres/tracks are highly dynamic and last for very short times. Moreover, arable soils are typically unsaturated and contain important secondary structures (e.g. aggregates), factors important for affecting their soil mechanical behaviour. Mechanical processes in porous media are not only of concern in soil mechanics, but also in other fields including geophysics and granular material science. Despite similarity of basic mechanical processes, theoretical frameworks often differ and reflect disciplinary focus. We review concepts from different but complementary fields concerned with porous media mechanics and highlight opportunities for synergistic advances in understanding deformation and compaction of arable soils. We highlight the important role of technological advances in non-destructive measurement methods at pore (X-ray tomography) and soil profile (seismic) scales that not only offer new insights into soil architecture and enable visualization of soil deformation, but are becoming instrumental in the development and validation of new soil compaction models. The integration of concepts underlying dynamic processes that modify soil pore spaces and bulk properties will improve the understanding of how soil management affect vital soil mechanical, hydraulic and ecological functions supporting plant growth

DEM simulation of stress transmission under agricultural traffic part 2 : shear stress at the tyre-soil interface

Although it has been proven to be of considerable importance, it remains unclear how to model the effect of traction on soil compaction. This study used multiple approaches to simulate the stress under an active wheel with the pseudo-continuous Sohne model, and compared it to a discrete element method (DEM) model of the same scenario. It was found that the differences in normal horizontal stress (sigma(y)) due to these different boundary conditions in the Sohne model were limited. According to these simulations, the effect on normal vertical stress (sigma(z)) was negligible. This was in contrast with the DEM simulations, where the impact of traction on sigma(y) was also stronger and less shallow. Advanced numerical models can be used to gain insight in the importance of traction, and could be used to improve the boundary condition of the Sohne model. However, further experimental validation is needed

Caractérisation morphologique en 3 dimensions des réseaux naturels de galeries lombriciennes et influence sur les transferts hydriques

Poste

Relation between 3D morphological characteristics of natural earthworm burrows and water transferts in soil

Communication invité

Root traits of crop species contributing to soil shear strength

International audienceRoots of annual species would be able to conserve soil properties during traffic induced compaction. The objective of this study was to determine and compare root traits and soil shear strength for three crop species with contrasted root types and morphological traits to see if roots of annual species are able to increase soil shear strength and thus explain the soil properties conservation. The experiment was performed under controlled conditions in steel cylinders containing a repacked loamy sand, with initial dry bulk density of 1.2 g cm-3 and that was kept moist. Soil shear strength parameters, i.e. cohesion and angle of internal friction, were determined from direct shear tests for soil cores at a soil matric potential of-10 kPa (i.e. water content at field capacity). The direct shear tests were performed with six external normal stress levels (25, 34, 44, 63, 83 and 93 kPa) and at a constant shear rate of 3 mm.min-1 , and applying Mohr Coulomb equation. The difference of root type, root length density, root density, specific root length and root dry matter content among crop species was not related to a difference in soil shear strength. The root volume density was the main trait involved in both soil cohesion and the angle of internal friction. This study highlights the effect of roots of annual crop species on soil shear strength by comparing their root traits to the apparent cohesion of soil core where they grow. Vicia faba would be a good candidate to improve soil shear strength for soil conservation. This study constitutes a step towards improving the understanding of plants' effects on soil shear strength with regards to selecting species and designing cropping systems for soil conservation

DEM simulation of stress transmission under agricultural traffic part 3 : evaluation with field experiment

In a concurrent paper, we compared a continuum model and a discrete element method (DEM) model in simulating stress transmission in soil under a wheel. Here, those models are evaluated with measurements of vertical normal stress (sigma(z)) under the wheels of a tractor-slurry spreader setup. It was found that the variation in the measured sigma(z) could be explained by the heterogeneous stress distribution in our structured soil, similar to what is observed in the DEM simulation. Furthermore, comparison of the continuum and DEM model showed that the lack of horizontal forces and dynamic load transfer at the boundary condition in the continuum model lead to a systematic underestimation of the measured sigma(z). Traction and drawbar forces have a significant impact on the stress state under a wheel. The continuum model and its boundary conditions should be modified to include these forces accurately