Selection genetique sur la reponse au stress et stress a l'abattage: consequences sur le proteome musculaire et lien avec la qualite de la chair chez la truite arc-en-ciel.

L'origine génétique des animaux est un des facteurs déterminants des caractéristiques des poissons en élevage (croissance, morphologie…) et de la qualité de leur chair. Une sélection divergente, basée sur la réponse individuelle de truite, en terme de niveau plasmatique de cortisol, suite à un stress aigu de confinement, a permis de montrer que ce paramètre est héritable, et d'obtenir des familles de truites présentant des niveaux de réponse à un stress aigu bien distincts (Pottinger et Carrick, 1999). Les animaux de ces familles divergentes ont été caractérisés pour leur croissance, qui s'avère meilleure pour les poissons répondant faiblement au stress, leur morphologie, et la qualité de leur chair. Les poissons répondant faiblement au stress présentent une chair moins lumineuse, plus jaune, et une résistance mécanique moindre associée à des fibres musculaires plus grosses et une teneur en lipides plus importante (Lefèvre et al., 2008a). Un stress au moment de l'abattage modifie le métabolisme post-mortem et conduit, la plupart du temps chez les salmonidés, à une chair moins ferme et plus pale (Lefèvre et al., 2008b). Un tel effet a été confirmé dans cette expérimentation de façon similaire pour les deux souches sélectionnées. Les protéines permettant d’expliquer potentiellement ces différences de qualité ne sont pas connues. L'objectif de ce travail était d'identifier les protéines différentiellement exprimées entre les deux souches sélectionnées et ayant subies ou non un stress de confinement juste avant l'abattage et de faire le lien avec les paramètres de qualité déjà mesurés

Investigation of the potential effects of transportation and lairage on the contamination of pig carcasses with Yersinia enterocolitica

Pathogenic Yersinia enterocolitica is frequently isolated from pig tonsils, but can also be found in the feces and lymph nodes of infected animals; which represent potential sources for the surface carcass contamination during slaughter. The aim of the study was to investigate the respective effects of the transportation and lairage steps on the overall contamination of the carcass, taking also into account the contamination of their environment. Each Trial was conducted in two abattoirs, whose environmental contamination was assessed. In each abattoir, 6 trucks and 6 lairage pens were sampled in duplicate at the end of the day, for 5 consecutive days, in spring and autumn. Four groups of 8 pigs from the Anses Specific Pathogen-Free herd (SPF) were mixed with conventional pigs for different contact times during transportation (1h) or lairage (2, 4 or 8h) prior to slaughter, and one group had no contact with other pigs. Each group of SPF pigs was sampled at the end of the slaughter line for the presence of pathogenic Y. enterocolitica for internal (tonsils, caecal content, mesenteric lymph nodes) and external (carcass surface) contamination. Samples were placed in ITC broth for enrichment at 25°C for 48h. Broth was streaked on CIN plates. After 24H at 30°C, typical colonies were streaked on YeCM plates. Biochemical tests were done to confirm Y. enterocolitica and to identify the biotype. The environmental contamination of trucks and lairage was very low. Y. enterocolitica was only detected in 11/240 lairage swabs. All internal and external samples from SPF pigs mixed with conventional pigs during transportation or lairage were negative after slaughter. Four tonsils of the SPF pigs slaughtered directly on the slaughter line after 4 hours of activity, with no prior contact with conventional pigs, and one of the corresponding surface carcasses, were found positive in one abattoir. In our experimental conditions with SPF pigs, we were not able to demonstrate contamination by contact with conventional pigs during transportation and lairage steps, whose environmental contamination appeared to be scarce. Limited cross contaminations were observed during the slaughter process, which emphasizes the importance of good hygiene procedures to limit carcass contamination by pathogenic Y. enterocolitica

Mapping the dynamical regimes of a SESAM mode-locked VECSEL with long cavity using time series analysis

The different dynamical regions of an optically-pumped SESAM mode-locked, long-cavity VECSEL system with a fundamental pulse repetition frequency of ~200 MHz are investigated. The output power, captured as 250 μs long time series using a sampling rate of 200 GSa/s, for each operating condition of the system, is analyzed to determine the dynamical state. A wavelength range of 985-995 nm and optical pump powers of 10 W-16.3 W is studied. The system produces high quality fundamental passive mode-locking (FML) over an extensive part of the parameter space, but the different dynamical regions outside of FML are the primary focus of this study. We report five types of output: CW emission, FML, modelocking of a few modes, double pulsing, and, semi-stable 4th harmonic mode-locking. The high sampling rate of the oscilloscope, combined with the long duration of the time series analyzed, enables insight into how the structure and substructure of pulses vary systematically over thousands of round trips of the laser cavity. Higher average output power is obtained in regions characterized by semi-stable 4th harmonic mode-locking than observed for FML, raising whether such average powers might be achieved for FML. The observed dynamical transitions from fundamental mode-locking provide insights into instability challenges in developing a stable, widely tunable, low repetition rate, turn-key system; and to inform future modelling of the system

Zoom sur les interfaces fluides

National audienc

Myopathie de Duchenne/Becker : apport de la microscopie à force atomique

International audienc

Air/liquid interface: relevance of Langmuir film as biological membrane model

National audienc

Comparison of interfacial activity of low density proteins (LDL) and high density proteins (HDL) obtained from normal and hypercholesterolemic patients

International audienc

Interfacial Behavior of LDL (Low density lipoproteins) and HDL (High density lioproteins): links with cardiovascular risk?

International audienc

[Invited Seminar] BioMolécules aux interfaces fluides

International audienc