Impact of sympathetic nervous system activity on post-exercise flow-mediated dilatation in humans

Transient reduction in vascular function following systemic large muscle group exercise has previously been reported in humans. The mechanisms responsible are currently unknown. We hypothesised that sympathetic nervous system activation, induced by cycle ergometer exercise, would contribute to post-exercise reductions in flow-mediated dilatation (FMD). Ten healthy male subjects (28 ± 5 years) undertook two 30 min sessions of cycle exercise at 75% HRmax. Prior to exercise, individuals ingested either a placebo or an α1-adrenoreceptor blocker (prazosin; 0.05 mg kg−1). Central haemodynamics, brachial artery shear rate (SR) and blood flow profiles were assessed throughout each exercise bout and in response to brachial artery FMD, measured prior to, immediately after and 60 min after exercise. Cycle exercise increased both mean and antegrade SR (P < 0.001) with retrograde SR also elevated under both conditions (P < 0.001). Pre-exercise FMD was similar on both occasions, and was significantly reduced (27%) immediately following exercise in the placebo condition (t-test, P = 0.03). In contrast, FMD increased (37%) immediately following exercise in the prazosin condition (t-test, P = 0.004, interaction effect P = 0.01). Post-exercise FMD remained different between conditions after correction for baseline diameters preceding cuff deflation and also post-deflation SR. No differences in FMD or other variables were evident 60 min following recovery. Our results indicate that sympathetic vasoconstriction competes with endothelium-dependent dilator activity to determine post-exercise arterial function. These findings have implications for understanding the chronic impacts of interventions, such as exercise training, which affect both sympathetic activity and arterial shear stress

Muscle Sympathetic Nerve Activity Is Related to a Surrogate Marker of Endothelial Function in Healthy Individuals

BACKGROUND: Evidence from animal studies indicates the importance of an interaction between the sympathetic nervous system and the endothelium for cardiovascular regulation. However the interaction between these two systems remains largely unexplored in humans. The aim of this study was to investigate whether directly recorded sympathetic vasoconstrictor outflow is related to a surrogate marker of endothelial function in healthy individuals. METHODS AND RESULTS: In 10 healthy normotensive subjects (3 f/7 m), (age 37+/-11 yrs), (BMI 24+/-3 kg/m(2)) direct recordings of sympathetic action potentials to the muscle vascular bed (MSNA) were performed and endothelial function estimated with the Reactive Hyperaemia- Peripheral Arterial Tonometry (RH-PAT) technique. Blood samples were taken and time spent on leisure-time physical activities was estimated. In all subjects the rate between resting flow and the maximum flow, the Reactive Hyperemic index (RH-PAT index), was within the normal range (1.9-3.3) and MSNA was as expected for age and gender (13-44 burst/minute). RH-PAT index was inversely related to MSNA (r = -0.8, p = 0.005). RH-PAT index and MSNA were reciprocally related to time (h/week) spent on physical activity (p = 0.005 and p = 0.006 respectively) and platelet concentration (PLT) (p = 0.02 and p = 0.004 respectively). CONCLUSIONS: Our results show that sympathetic nerve activity is related to a surrogate marker of endothelial function in healthy normotensive individuals, indicating that sympathetic outflow may be modulated by changes in endothelial function. In this study time spent on physical activity is identified as a predictor of sympathetic nerve activity and endothelial function in a group of healthy individuals. The results are of importance in understanding mechanisms underlying sympathetic activation in conditions associated with endothelial dysfunction and emphasise the importance of a daily exercise routine for maintenance of cardiovascular health

Phenotypic and transcriptomic characterization of canine myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) are key players in immune evasion, tumor progression and metastasis. MDSCs accumulate under various pathological states and fall into two functionally and phenotypically distinct subsets that have been identified in humans and mice: polymorphonuclear (PMN)-MDSCs and monocytic (M)-MDSCs. As dogs are an excellent model for human tumor development and progression, we set out to identify PMN-MDSCs and M-MDSCs in clinical canine oncology patients. Canine hypodense MHC class II-CD5-CD21-CD11b+ cells can be subdivided into polymorphonuclear (CADO48A+CD14-) and monocytic (CADO48A-CD14+) MDSC subsets. The transcriptomic signatures of PMN-MDSCs and M-MDSCs are distinct, and moreover reveal a statistically significant similarity between canine and previously published human PMN-MDSC gene expression patterns. As in humans, peripheral blood frequencies of canine PMN-MDSCs and M-MDSCs are significantly higher in dogs with cancer compared to healthy control dogs (PMN-MDSCs: p < 0.001; M-MDSCs: p < 0.01). By leveraging the power of evolution, we also identified additional conserved genes in PMN-MDSCs of multiple species that may play a role in MDSC function. Our findings therefore validate the dog as a model for studying MDSCs in the context of cancer

Performance des géosynthétiques bentonitiques en couverture d'installations de stockage de déchets : état des connaissances et proposition de méthodologie

National audienceClay geosynthetic barriers (GBR-Cs) used in landfill covers must ensure lining on the long term. The primary mode of ageing of bentonite GBR-Cs in covers is the coupling of cation exchange and hydration-desiccation cycles. The objective of this paper is to synthesize the optimal conditions to prevent a loss of performance of GBR-Cs in covers with time, based on a literature review. Various parameters will be discussed. The literature review will put in light the lack of consistent information from study to study. This enforces the need for a list of information to collect in future excavations. Such a list is proposed in the third section of this paper followed by the presentation of results from recent excavations performed by the first author.Les géosynthétiques bentonitiques (GSB) utilisés en couverture d'installations de stockage de déchets (ISD) doivent apporter un niveau d'étanchéité suffisant sur le long terme. La dessiccation possible de la bentonite couplée à des phénomènes d'échanges cationiques a été identifiée comme le principal mode de vieillissement. L'objectif de cet article est, à partir d'une synthèse bibliographique, de déterminer les conditions optimales pour prévenir les baisses de performance des GSB. Différents paramètres seront discutés. Cette synthèse bibliographique met en évidence le manque de données cohérentes d'étude à étude. C'est pourquoi une liste d'informations à collecter au cours des prochaines excavations est également proposée à la fin de l'article avant la présentation de résultats d'excavations récentes de GSB

Performance des Géosynthétiques bentonitiques dans les couvertures d'installations de stockage de déchets

International audienceClay geosynthetic barriers (GBR-Cs) used in landfill covers must ensure lining on the long term. The primary mode of ageing of bentonite GBR-Cs in covers is the coupling of cation exchange and hydrationdesiccation cycles. The objective of this paper is to synthesize the optimal conditions to prevent a loss of performance of GBR-Cs in covers with time, based on a literature review. Various parameters will be discussed. The literature review will put in light the lack of consistent information from study to study. This enforces the need for a list of information to collect in future excavations. Such a list is proposed in the third section of this paper followed by the presentation of results from recent excavations performed by the first author

Performance des Géosynthétiques bentonitiques dans les couvertures d'installations de stockage de déchets

International audienceClay geosynthetic barriers (GBR-Cs) used in landfill covers must ensure lining on the long term. The primary mode of ageing of bentonite GBR-Cs in covers is the coupling of cation exchange and hydrationdesiccation cycles. The objective of this paper is to synthesize the optimal conditions to prevent a loss of performance of GBR-Cs in covers with time, based on a literature review. Various parameters will be discussed. The literature review will put in light the lack of consistent information from study to study. This enforces the need for a list of information to collect in future excavations. Such a list is proposed in the third section of this paper followed by the presentation of results from recent excavations performed by the first author

Etanchéité des géomembrane - Expérience en matière d'essai

International audienceLa propriété principale des géomemembranes est l'étanchéité. Cette propriété doit donc être mesurée. Une méthode a été développée pour évaluer le niveau d'étanchéité des géomembranes. Elle fait maintenant l'objet d'une norme européenne. L'objectif de l'article est de montrer les résultats d'une campagne de comparaison interlaboratoire. Les essais ont porté sur différentes natures de géomembranes vierges. Les mesures effectuées indiquent des niveaux d'étanchéité inférieurs, la plupart du temps, à 10-6 m3/m²/j

3ème symposium international sur les géosynthtéiques bentonitiques

International audienceThis Symposium is part of a series of International Symposia on Geosynthetic Clay Liners (GCL's) held in Germany every eight years. It is organized under the auspices of the International Geosynthetics Society (IGS). The first two symposia were held in Nuremberg in 1994 and in 2002. This will be the third in the series to be held in Würzburg. The aim is to exchange the latest knowledge on GCLs and to bring GCL experts from all parts of the world together. GCL's were developed in the mid 1980s in the USA and they were further developed in Germany in the late 1980s. Nowadays, GCL's are manufactured all over the world. In 2000 a new term was proposed for standardization in international usage. Since 2005 the term Clay Geosynthetic Barrier (GBR-C) has been suggested to replace the term GCL. In practice, however, both terms (GCL and GBR-C) are used interchangeably. It should be noted that several other special conferences have been held on GCL's. Two conferences were held in the USA, namely, Testing and Acceptance Criteria on Geosynthetic Clay Liners in 1996, and Advances in Geosynthetic Clay Liner Technology in 2004. Also, a conference was held in France GEO-BENTO 98 in 1998. All have proceedings available. In addition to the above symposia and conferences, the general technical literature has seen many researchers and investigators publish their findings regarding GCL's. From the variety of numerous publications on topics related to GCL's it can be seen that GCL's are very versatile products which are of interest for many disciplines ranging from geotechnical engineering, soil mechanics, soil science, physics, chemistry, mineralogy, textile engineering, plastic engineering, material science and beyond. In the USA and South Africa, generic specifications have been developed for GCL's. For landfill covers in Germany approvals have been established provided that the product can demonstrate a lifetime of more than 100 years. In Europe, a CE certification is required for all uses of GCL's. This third GCL symposium will discuss the challenging topics for this segment of geosynthetic materials in an open and interactive forum