73 research outputs found
Lithosphere tearing along STEP faults and synkinematic formation of lherzolite and wehrlite in the shallow subcontinental mantle
Subduction-transform edge propagator (STEP)
faults are the locus of continual lithospheric tearing at slab
edges, resulting in sharp changes in the lithospheric and
crustal thickness and triggering lateral and/or near-vertical
mantle flow. However, the mechanisms at the lithospheric
mantle scale are still poorly understood. Here, we present
the microstructural study of olivine-rich lherzolite, harzburgite
and wehrlite mantle xenoliths from the Oran volcanic
field (Tell Atlas, northwest Algeria). This alkali volcanic
field occurs along a major STEP fault responsible for the
Miocene westward slab retreat in the westernmost Mediterranean.
Mantle xenoliths provide a unique opportunity to investigate
the microstructures in the mantle section of a STEP
fault system.
The microstructures of mantle xenoliths show a variable
grain size ranging from coarse granular to fine-grained
equigranular textures uncorrelated with lithology. The major
element composition of the mantle peridotites provides temperature
estimates in a wide range (790â1165 ÂșC) but in general,
the coarse-grained and fine-grained peridotites suggest
deeper and shallower provenance depth, respectively. Olivine
grain size in the fine-grained peridotites depends on the size
and volume fraction of the pyroxene grains, which is consistent
with pinning of olivine grain growth by pyroxenes
as second-phase particles. In the coarse-grained peridotites,
well-developed olivine crystal-preferred orientation (CPO) is
characterized by orthorhombic and [100]-fiber symmetries,
and orthopyroxene has a coherent CPO with that of olivine,
suggesting their coeval deformation by dislocation creep at
high temperature. In the fine-grained microstructures, along
with the weakening of the fabric strength, olivine CPO symmetry
exhibits a shift towards [010] fiber and the [010] and
[001] axes of orthopyroxene are generally distributed subparallel
to those of olivine. These data are consistent with deformation
of olivine in the presence of low amounts of melts
and the precipitation of orthopyroxenes from a melt phase.
The bulk CPO of clinopyroxene mimics that of orthopyroxene
via a topotaxial relationship of the two pyroxenes. This
observation points to a melt-related origin of most clinopyroxenes
in the Oran mantle xenoliths.This research has been supported by the
Agencia Estatal de InvestigaciĂłn (grant nos. CGL2016-75224-R,
CGL2016-81085-R and CGL2015-67130-C2-1-R), the Junta de
AndalucĂa research groups RNM-131 and RNM-148, and the International
Lithosphere Program (grant no. CC4-MEDYNA)
Food allergy enhances allergic asthma in mice
BackgroundAtopic march refers to the typical transition from a food allergy in early childhood to allergic asthma in older children and adults. However the precise interplay of events involving gut, skin and pulmonary inflammation in this process is not completely understood.ObjectivesTo develop a mouse model of mixed food and respiratory allergy mimicking the atopic march and better understand the impact of food allergies on asthma.MethodsFood allergy to ovalbumin (OVA) was induced through intra-peritoneal sensitization and intra-gastric challenge, and/or a respiratory allergy to house dust mite (HDM) was obtained through percutaneous sensitization and intra-nasal challenges with dermatophagoides farinae (Der f) extract. Digestive, respiratory and systemic parameters were analyzed.ResultsOVA-mediated gut allergy was associated with an increase in jejunum permeability, and a worsening of Der f-induced asthma with stronger airway hyperresponsiveness and pulmonary cell infiltration, notably eosinophils. There was overproduction of the pro-eosinophil chemokine RANTES in broncho-alveolar lavages associated with an enhanced Th2 cytokine secretion and increased total and Der f-specific IgE when the two allergies were present. Both AHR and lung inflammation increased after a second pulmonary challenge.ConclusionGut sensitization to OVA amplifies Der f-induced asthma in mice
Les sociétés populaires à travers leurs procÚs-verbaux
Sous la RĂ©volution française, les sociĂ©tĂ©s populaires ont crĂ©Ă© et animĂ© des rĂ©seaux de sociabilitĂ© politique dont leurs procĂšs-verbaux sont des tĂ©moins. Ces dĂ©libĂ©rations sont des sources remarquables que la collection des "Documents inĂ©dits sur lâhistoire de France", publiĂ©e sous lâĂ©gide du ComitĂ© des travaux historiques et scientifiques, permet de redĂ©couvrir. Les Ă©tudes rĂ©unies dans cet ouvrage nous invitent Ă mieux comprendre le fonctionnement des sociĂ©tĂ©s populaires et Ă mesurer lâimportance de leurs archives pour lâhistoire politique et sociale
Maternal prebiotic supplementation impacts colitis development in offspring mice
Background and aimsMaternal diet plays a key role in preventing or contributing to the development of chronic diseases, such as obesity, allergy, and brain disorders. Supplementation of maternal diet with prebiotics has been shown to reduce the risk of food allergies and affect the intestinal permeability in offspring later in life. However, its role in modulating the development of other intestinal disorders, such as colitis, remains unknown. Therefore, we investigated the effects of prebiotic supplementation in pregnant mice on the occurrence of colitis in their offspring.Materials and methodsOffspring from mothers, who were administered prebiotic galacto-oligosaccharides and inulin during gestation or fed a control diet, were subjected to three cycles of dextran sulphate sodium (DSS) treatment to induce chronic colitis, and their intestinal function and disease activity were evaluated. Colonic remodelling, gut microbiota composition, and lipidomic and transcriptomic profiles were also assessed.ResultsDSS-treated offspring from prebiotic-fed mothers presented a higher disease score, increased weight loss, and increased faecal humidity than those from standard diet-fed mothers. DSS-treated offspring from prebiotic-fed mothers also showed increased number of colonic mucosal lymphocytes and macrophages than the control group, associated with the increased colonic concentrations of resolvin D5, protectin DX, and 14-hydroxydocosahexaenoic acid, and modulation of colonic gene expression. In addition, maternal prebiotic supplementation induced an overabundance of eight bacterial families and a decrease in the butyrate caecal concentration in DSS-treated offspring.ConclusionMaternal prebiotic exposure modified the microbiota composition and function, lipid content, and transcriptome of the colon of the offspring. These modifications did not protect against colitis, but rather sensitised the mice to colitis development
DNA methylation signature of chronic low-grade inflammation and its role in cardio-respiratory diseases
We performed a multi-ethnic Epigenome Wide Association study on 22,774 individuals to describe the DNA methylation signature of chronic low-grade inflammation as measured by C-Reactive protein (CRP). We find 1,511 independent differentially methylated loci associated with CRP. These CpG sites show correlation structures across chromosomes, and are primarily situated in euchromatin, depleted in CpG islands. These genomic loci are predominantly situated in transcription factor binding sites and genomic enhancer regions. Mendelian randomization analysis suggests altered CpG methylation is a consequence of increased blood CRP levels. Mediation analysis reveals obesity and smoking as important underlying driving factors for changed CpG methylation. Finally, we find that an activated CpG signature significantly increases the risk for cardiometabolic diseases and COPD.publishedVersionPeer reviewe
ETUDE DE LA CONTRIBUTION RELATIVE DU TCR, DU CD8 ET DES MOLECULES ACCESSOIRES DANS L'ACTIVATION ET LA SELECTION DES LYMPHOCYTES T CYTOTOXIQUES HUMAINS (DOCTORAT IMMUNOLOGIE)
NANTES-BU MĂ©decine pharmacie (441092101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF
Immunomodulation of B Lymphocytes by Prebiotics, Probiotics and Synbiotics: Application in Pathologies
Introduction: Prebiotics, probiotics and synbiotics are known to have major beneficial effects on human health due to their ability to modify the composition and the function of the gut mucosa, the gut microbiota and the immune system. These components largely function in a healthy population throughout different periods of life to confer homeostasis. Indeed, they can modulate the composition of the gut microbiota by increasing bacteria strands that are beneficial for health, such as Firmicute and Bifidobacteria, and decreasing harmful bacteria, such as Enteroccocus. Their immunomodulation properties have been extensively studied in different innate cells (dendritic cells, macrophages, monocytes) and adaptive cells (Th, Treg, B cells). They can confer a protolerogenic environment but also modulate pro-inflammatory responses. Due to all these beneficial effects, these compounds have been investigated to prevent or to treat different diseases, such as cancer, diabetes, allergies, autoimmune diseases, etc. Regarding the literature, the effects of these components on dendritic cells, monocytes and T cells have been studied and presented in a number of reviews, but their impact on B-cell response has been less widely discussed. Conclusions: For the first time, we propose here a review of the literature on the immunomodulation of B-lymphocytes response by prebiotics, probiotics and synbiotics, both in healthy conditions and in pathologies. Discussion: Promising studies have been performed in animal models, highlighting the potential of prebiotics, probiotics and synbiotics intake to treat or to prevent diseases associated with B-cell immunomodulation, but this needs to be validated in humans with a full characterization of B-cell subsets and not only the humoral response
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