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Search Results: 1 - 10 of 13233 matches for " Eric Auclair "
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A Bioenergetic-Redox Approach to the Effect of Live Yeast on Ruminal pH during Induced Acidosis in Dairy Cow  [PDF]
Jean Philippe Marden, Corine Bayourthe, Eric Auclair, Raymond Moncoulon
American Journal of Analytical Chemistry (AJAC) , 2013, DOI: 10.4236/ajac.2013.410A1008
Abstract: The objective of this study was to evaluate the capacity of the live yeast (LY) Saccharomyces cerevisiae in optimizing ruminal pH and in understanding its mode of action during induced acidosis in dairy cow. Two non-lactating cannulated cows were used and offered twice daily a control diet (CD) consisting of 51% corn silage and 49% concentrates or a LY diet (LYD) composed of CD supplemented with 4 g of LY per cow and per day. Measurements of pH and redox potential (Eh) were continuously made at 1 h interval during an experimental period of 9 h per day. Samples of ruminal fluid were also taken at 2 h intervals for analyses of volatile fatty acids (VFA) and lactic acid. Oxygen partial pressure (logPO2) in the ruminal milieu was calculated from the Nernst equation, using either O2-H2O or lactate-propionate redox couples. The results showed an increase of 0.2 unit in ruminal pH when LYD was fed, which was accompanied by a mean difference in Eh of -20 mV with respect to CD. The logPO2 decreased significantly by 0.8 log unit for LYD when compared to CD. Concentrations of VFA and proportion of propionate were higher with LYD (114.4 mM and 17.1% total VFA) compared to CD (102.4 mM and 15.4% total VFA). Proportion of butyrate
Interaction between Live Yeast and Dietary Rumen Degradable Protein Level: Effects on Diet Utilization in Early-Lactating Dairy Cows  [PDF]
Christine Julien, Jean Philippe Marden, Eric Auclair, Raymond Moncoulon, Laurent Cauquil, Jean Louis Peyraud, Corine Bayourthe
Agricultural Sciences (AS) , 2015, DOI: 10.4236/as.2015.61001
Abstract: Four early lactating Holstein cows were used to study the effect of live yeast (LY, Actisaf® CNCM I-4407, Lesaffre Feed Additives, Marcq en Baroeul, France) supplementation on diet digestive utilization of dairy cows receiving concentrated corn silage-based diets with two rumen-degradable protein (RDP) levels. For a 33 d period, cows were fed a total mixed ration (TMR) containing an adequate level (AL) of RDP or a low level (LL, 30% below AL) by using soybean meal or tanned soybean meal, respectively: for 21 d with no LY addition followed by 12 d during which LY was added to the diet. The pH and redox potential (Eh) were recorded and ruminal fluid samples were collected over 3 consecutive days. Feces were collected individually over 48 h and individual dry matter intake (DMI) was measured for determining apparent nutrient digestibility. The effective degradability of individual feed ingredients composing both diets was evaluated with nylon bags technique. Structure of the ruminal bacterial community was studied and diversity index was calculated. Digestibility of organic matter (OM) and crude protein (CP) were lower for LL than those for AL. With LY, digestibility of OM and CP was increased: +2.4 and +0.8 points, for AL, and +3.7 and +5.9 points for LL, respectively. Live yeast reduced dietary N ruminal degradation with both AL and LL. Ruminal pH and Eh were lower with AL compared to LL: 5.95 and –167 mV vs. 6.13 and –144 mV. Live yeast increased ruminal total volatile fatty acids (VFA) (+8.6%), C2 (+10%), and C4 (+35%) contents for LL and decreased that of C3 (?9.8%) for AL. Neither the structure of bacterial populations of the rumen nor the diversity index (Shannon) was altered by treatments. Those results suggested a specific interest in using LY in RDP deficient diets for early lactating cows.
Quantitative Analysis of the Relationship between Ruminal Redox Potential and pH in Dairy Cattle: Influence of Dietary Characteristics  [PDF]
Yayu Huang, Jean Philippe Marden, Chaouki Benchaar, Christine Julien, Eric Auclair, Corine Bayourthe
Agricultural Sciences (AS) , 2017, DOI: 10.4236/as.2017.87047
Abstract: The ruminal redox potential (Eh) can reflect the microbiological activity and dynamics of fermentation in the rumen. It might be an important indicator of rumen fermentation in combination with pH. However, the ruminal Eh has been rarely studied in dairy cows due to the difficulty of its measurement, and the relationship between ruminal Eh and pH is not clear. The objective of this study was to investigate the relationship between ruminal Eh and pH of dairy cows by meta-analysis of systematic measurements from different experiments. A database was constructed from 22 experiments on cannulated dairy cattle including 57 dietary treatments. The ruminal pH and Eh were measured without air contact between 0 and 8 h post-feeding. The results demonstrated a quadratic correlation between ruminal Eh and pH with a reliable within-animal variation (Eh = -1697 + 540.7 pH -47.7 pH2, nobservation = 70, nanimal = 26, P < 0.001, RMSE = 56, AIC = 597). The dietary characteristics (NDF, NDFf, OM, starch, degradable starch, soluble sugars contents, and the dietary ionic balance) influencing the ruminal pH also affected the ruminal Eh, but not always to the same extent. Some of them still influenced the relationship between ruminal Eh and pH. While the mechanism of the interaction between ruminal Eh and pH remains to be elucidated, it would be interesting to associate Eh to microbial profile, ruminal VFA concentration and milk production performance in future studies.
The Effects of a Probiotic Yeast on the Bacterial Diversity and Population Structure in the Rumen of Cattle
Eric Pinloche, Neil McEwan, Jean-Philippe Marden, Corinne Bayourthe, Eric Auclair, C. Jamie Newbold
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0067824
Abstract: It has been suggested that the ability of live yeast to improve milk yield and weight gain in cattle is because the yeast stimulates bacterial activity within the rumen. However it remains unclear if this is a general stimulation of all species or a specific stimulation of certain species. Here we characterised the change in the bacterial population within the rumen of cattle fed supplemental live yeast. Three cannulated lactating cows received a daily ration (24 kg/d) of corn silage (61% of DM), concentrates (30% of DM), dehydrated alfalfa (9% of DM) and a minerals and vitamins mix (1% of DM). The effect of yeast (BIOSAF SC 47, Lesaffre Feed Additives, France; 0.5 or 5 g/d) was compared to a control (no additive) in a 3×3 Latin square design. The variation in the rumen bacterial community between treatments was assessed using Serial Analysis of V1 Ribosomal Sequence Tag (SARST-V1) and 454 pyrosequencing based on analysis of the 16S rRNA gene. Compared to the control diet supplementation of probiotic yeast maintained a healthy fermentation in the rumen of lactating cattle (higher VFA concentration [high yeast dose only], higher rumen pH, and lower Eh and lactate). These improvements were accompanied with a shift in the main fibrolytic group (Fibrobacter and Ruminococcus) and lactate utilising bacteria (Megasphaera and Selenomonas). In addition we have shown that the analysis of short V1 region of 16s rRNA gene (50–60 bp) could give as much phylogenetic information as a longer read (454 pyrosequencing of 250 bp). This study also highlights the difficulty of drawing conclusions on composition and diversity of complex microbiota because of the variation caused by the use of different methods (sequencing technology and/or analysis).
Problem formulation by medical students: an observation study
Francois Auclair
BMC Medical Education , 2007, DOI: 10.1186/1472-6920-7-16
Abstract: 32 third year medical students were presented with a complex case of endocarditis. They were asked to synthesize the case and give the best formulation of the problem. They were then asked to provide a diagnosis. A subsequent group of 25 students were presented with the problem already formulated and were also asked for the diagnosis. We analyzed the student's problem formulations using the presence or absence of essential elements of the case, the use of higher-order concepts and the use of relations between concepts.12/32 students presented with the case made the correct diagnosis. Diagnostic accuracy was significantly associated with the use of higher-order concepts and relations between concepts. Establishing explicit relations was particularly important. Almost all students who missed the diagnosis could not elicit any relations between concepts but only reported factual observations. When presented with an already formulated problem, 19/25 students made the correct diagnosis. (p < 0.05)When faced with a complex new case, students may not have the structured knowledge to recognize the nature of the problem. They have to build new schema or problem representation. Our observations suggest that this process involves using higher-order concepts and establishing new relations between concepts. The fact that students could recognize the disease when presented with a formulated problem but had more difficulty when presented with the original complex case indicates that knowledge of the clinical features may be necessary but not sufficient for problem formulation. Our hypothesis is that problem formulation represents a distinct ability.Problem formulation is necessary because the world we experience is complex. The problems we face are often ill-structured. One or several elements of the problem may be unknown, the same elements may be different in different context, there is uncertainty about the concepts necessary for a solution, the relationship between concepts an
Indicadores Urbanos, impactos en la conferencia de Estambul+5 y sus direcciones futuras
Christine Auclair
Revista INVI , 2002,
Revenir vers les habitants, revenir sur les territoires
élizabeth Auclair
Développement Durable et Territoires , 2011,
Abstract: Le développement durable se voulait un projet de civilisation, mais le concept a vite été fragilisé par la suprématie des intérêts économiques, et par l’enfermement dans des préoccupations d’ordre environnemental. Dans la période de crise actuelle, on s’interroge : comment veut-on vivre ? avec quelles valeurs ? dans quelles villes et dans quels territoires? Il s’agit ici de voir comment les arts et la culture peuvent contribuer à cet objectif du vivre ensemble . Au-delà de positionnements opportunistes, on observe qu’une meilleure prise en compte de la culture, dans ses différentes acceptions, peut promouvoir des approches transversales, reposant sur les valeurs de solidarité, de respect de la diversité culturelle, de démocratie locale et de citoyenneté, et remettre ainsi les habitants au c ur des politiques et des projets de territoires. La recomposition du paysage culturel que l’on observe en France, notamment autour des agendas 21 de la culture et des nouveaux territoires de l’art, témoigne de la part d’artistes, élus et autres professionnels de la culture d’une volonté de travailler au plus près de la population afin de monter des projets qui remettent la culture au c ur des politiques locales. Sustainable development was supposed to be a “civilization” concept, but the power of the economic interests and the pressure of the environmental issues have fragilized the concept. With the recent world crisis, many questions now arise: we must change our model, but how do we want to live, with which values and indicators, in what kind of towns and territories? In this article we propose to analyse how cultural development can help to reach the aim of “living together”. Indeed, taking into account cultural diversity and initiating local activities enables to develop new kinds of projects with the inhabitants, and to promote essential values such as local democracy, solidarity, tolerance, proximity… The changes in the French cultural policies seem to show that things are moving that way.
Clover calculus for homology 3-spheres via basic algebraic topology
Emmanuel Auclair,Christine Lescop
Mathematics , 2004, DOI: 10.2140/agt.2005.5.71
Abstract: We present an alternative definition for the Goussarov--Habiro filtration of the Z-module freely generated by oriented integral homology 3-spheres, by means of Lagrangian-preserving homology handlebody replacements (LP-surgeries). Garoufalidis, Goussarov and Polyak proved that the graded space (G_n)_n associated to this filtration is generated by Jacobi diagrams. Here, we express elements associated to LP-surgeries as explicit combinations of these Jacobi diagrams in (G_n)_n. The obtained coefficient in front of a Jacobi diagram is computed like its weight system with respect to a Lie algebra equipped with a non-degenerate invariant bilinear form, where cup products in 3-manifolds play the role of the Lie bracket and the linking number replaces the invariant form. In particular, this article provides an algebraic version of the graphical clover calculus developed by Garoufalidis, Goussarov, Habiro and Polyak. This version induces splitting formulae for all finite type invariants of homology 3-spheres.
Allosteric Communication across the Native and Mutated KIT Receptor Tyrosine Kinase
Elodie Laine,Christian Auclair,Luba Tchertanov
PLOS Computational Biology , 2012, DOI: 10.1371/journal.pcbi.1002661
Abstract: A fundamental goal in cellular signaling is to understand allosteric communication, the process by which signals originated at one site in a protein propagate dependably to affect remote functional sites. Here, we describe the allosteric regulation of the receptor tyrosine kinase KIT. Our analysis evidenced that communication routes established between the activation loop (A-loop) and the distant juxtamembrane region (JMR) in the native protein were disrupted by the oncogenic mutation D816V positioned in the A-loop. In silico mutagenesis provided a plausible way of restoring the protein communication detected in the native KIT by introducing a counter-balancing second mutation D792E. The communication patterns observed in the native and mutated KIT correlate perfectly with the structural and dynamical features of these proteins. Particularly, a long-distance effect of the D816V mutation manifested as an important structural re-organization of the JMR in the oncogenic mutant was completely vanished in the double mutant D816V/D792E. This detailed characterization of the allosteric communication in the different forms of KIT, native and mutants, was performed by using a modular network representation composed of communication pathways and independent dynamic segments. Such representation permits to enrich a purely mechanistic interaction-based model of protein communication by the introduction of concerted local atomic fluctuations. This method, validated on KIT receptor, may guide a rational modulation of the physiopathological activities of other receptor tyrosine kinases.
Patrimony for Resilience: Evidence from the Forest Agdal in the Moroccan High Atlas Mountains
Laurent Auclair,Patrick Baudot,Didier Genin,Bruno Romagny
Ecology and Society , 2011, DOI: 10.5751/es-04429-160424
Abstract: Patrimony and resilience appear today as key concepts for understanding the dynamics of systems confronted with natural hazards. Nevertheless, the theoretical comparison between these concepts drawn from different epistemic approaches is lacking. Our aim is to interrelate resilience and patrimony concepts on the basis of a real example: the Agdal, a traditional forest management system in the Moroccan High Atlas. The role played by the Agdal in safeguarding the patterns of forest resource use by village communities from both external and internal conflicts, from natural hazards, and by securing a long-term supply of resource diversity is highlighted. This role shows the patrimonial character of the forest Agdal for the village communities and suggests an adaptive perspective. The patrimonial construction of the forest gives rise to management systems that allow a major place to experience social and environmental feedback, contributing to strengthened social-ecological system resilience and adaptability in the High Atlas Mountains. The notion of patrimony as a tool of resilience opens up a new interdisciplinary line of research.
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