Reproducción del atún rojo Thunnus thynnus en jaulas flotantes obtención de puestas masivas mediante implantes hormonales

In the frame of the SELFDOTT project (From capture based to SELF-sustained aquaculture and Domestication Of bluefin tuna, Thunnus thynnus) captive-reared Atlantic bluefin tuna (Thunnus thynnus) (n=15, estimated body weight=90 Kg) maintained for 3 years in captivity in El Gorguel (Cartagena, Spain) were administered a gonadotrophin releasing hormone agonist (GnRHa) implant underwater, during the natural spawning period for this species in the Mediterranean Sea (June). Beginning 48-72 h later, massive spawnings occurred everyday for 17 days, with a daily maximum fecundity of 34 million eggs. Egg collection was accomplished by placing a special curtain around the perimeter of the cage and at 6 m allowed the floating eggs to be maintained within the cage and be collected at night and sunrise with 500 ìm mesh size nets from the surface of the water.Proyecto SELFDOTT. UE

NADPH-sulfite reductase from Escherichia coli. A flavin reductase participating in the generation of the free radical of ribonucleotide reductase.

International audienceProtein R2, the small subunit of ribonucleotide reductase of Escherichia coli, contains an essential free radical localized to tyrosine 122 of its polypeptide chain. When this radical is scavenged by hydroxyurea, the enzyme is transformed into an inactive form, metR2. E. coli contains a NAD(P)H:flavin oxidoreductase, named Fre, absolutely required for the regeneration of the radical and the activation of metR2 into R2. Consequently, an E. coli mutant strain lacking an active fre gene is more sensitive to hydroxyurea during growth, demonstrating the physiological protective function of Fre from the loss of the radical. However, this gene is not essential, and we found that E. coli contains a second tyrosyl radical generating activity, also residing in a flavin reductase. The enzyme has been purified 200-fold to homogeneity and found to be identical to sulfite reductase. Pure sulfite reductase has the ability to catalyze the reduction of free riboflavin, FMN, or FAD by NADPH and thus, as Fre, to transfer electrons to the iron center of metR2, a key step during the activation reaction

Effect of chronic exposure to ammonia on growth, food utilisation and metabolism of the European sea bass (Dicentrarchus labrax)

The chronic effects of exposing sea bass (average initial weight 100 g) to ammonia in water at 22 degreesC were first evaluated over a 61-day period (period 1, P1) during which nine different groups were submitted to nine ambient ammonia levels ranging from 0.014 to 0.493 mg 1(-1) NH3-N (0.53-16.11 mg 1(-1) total ammonia nitrogen (TA-N)) and fed using self-feeders. At the end of P1, the fish were starved for 10 days (P2). Their recovery capacity was tested over 43 days (P3) after which the exogenous ammonia supply was stopped in all treatments and the fish were allowed to feed. After 20 days of exposure a highly significant effect of ammonia was evident from the decrease in feeding activity, voluntary feed intake (VFI) and specific growth rate (SGR), and the increase in the feed conversion ratio (FCR). Ammonia exposure had no effect on circadian feeding rhythm or hourly actuation profiles. At the end of PI, the fish seemed to have adapted to all ambient ammonia concentrations tested since feeding and growth parameters were independent of ammonia levels. But they were unable to compensate for growth losses. Physiological adjustments were observed: plasma TA-N concentrations were positively related to ambient TA-N while there was no major disturbance in plasma urea. Plasma tri-iodo-thyronine concentrations were affected by ambient ammonia concentrations and there were no significant changes in hydromineral balance. During P2, oxygen consumption and urea excretion did appear to have been affected by ambient ammonia. When the exogenous supply of ammonia was stopped (M), fish exhibited hyperphagia and compensatory growth. In fish previously exposed to the highest ammonia levels, SGR and VFI were highest, and their FCR was improved. At the end of the experiment the final average weights were similar in all of the treatments (range 337-396 g). Depending on the concentrations used, ammonia exposure may enhance subsequent fish appetite and growth rate and have a similar effect on growth performances as restricting feeding level. Within the range tested, no detrimental effect of ammonia on the metabolic capacity of the fish, measured by oxygen consumption and urea excretion, or on their physiological status was recorded, and the fish had a good recovery capacity. In the conditions of the experiment, the non-observable effect concentration (NOEC) was 6 mg 1(-1).Les effets d'une exposition prolongée à l'ammoniaque, sur des bars (poids moyen 140 g) dans de l'eau à 22 °C, ont été évalués dans un premier temps durant une période de 61 jours (période 1, P1). Les poissons, nourris par des distributeurs « self-service », étaient alors répartis en neuf groupes soumis à neuf niveaux différents de concentration d'ammoniaque, de 0,014 à 0,493 mg l¿1 de NH3-N (0,53 à 16,11 mg l¿1 d'azote ammoniacal total (TA-N)). À la fin de P1, les animaux ont été mis à jeun pendant dix jours (P2). Leur capacité de récupération a été ensuite testée durant 43 jours (P3) après que l'alimentation en ammoniaque eût été supprimée et que les animaux aient pu de nouveau s'alimenter. Après 20 jours d'exposition, l'activité alimentaire, les aliments ingérés volontairement (VFI) et le taux de croissance spécifique (SGR) ont diminué significativement sous l'effet de l'ammoniaque, pendant que le taux de transformation de l'aliment (FCR) a augmenté. L'exposition à l'ammoniaque n'a pas eu d'effet sur les activités circadiennes d'alimentation, ni sur les rythmes horaires de demande alimentaire. À la fin de P1, tous les poissons ont semblé s'être adaptés aux concentrations testées. En effet, les paramètres de croissance et d'alimentation étaient revenus à la normale. Cependant, les poissons n'avaient pas compensé leur retard de croissance. Quelques ajustements physiologiques ont pu être observés : le taux de TA-N du plasma était positivement corrélé au taux d'ammoniaque ambiant, mais pas celui de l'urée. Le taux de tri-iodo-thyronine du plasma a été modifié, mais pas l'équilibre hydrominéral. Durant P2, la consommation d'oxygène et l'excrétion d'urée n'ont pas été affectées. Quand l'apport d'ammoniaque a pris fin (P3), les poissons ont montré de l'hyperphagie et ont manifesté une croissance compensatrice. Les poissons préalablement soumis aux plus fortes concentrations présentent les meilleurs SGR et VFI. À la fin de l'expérimentation, les poids moyens des poissons étaient comparables dans tous les traitements (entre 337 et 396 g). Selon sa concentration, l'ammoniaque peut entraîner une augmentation de l'appétit et du taux de croissance, ultérieurement, similaires à ceux d'un rationnement alimentaire. Dans la gamme testée, aucun effet préjudiciable de l'ammoniaque n'a été observé, ni sur les capacités métaboliques de l'animal, mesurées par sa consommation d'oxygène et l'excrétion d'urée, ni sur ses caractéristiques physiologiques. Les animaux ont montré une très bonne capacité de récupération. Dans les conditions de l'expérience, la concentration, pour laquelle aucun effet n'a pu être observé, était de 6 mg l¿1

Postmortem degradation of white fish skeletal muscle (Sea bass, Dicentrarchus labrax) : fat diet effects on in situ dystrophin proteolysis during the prerigor stage

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Structural and functional studies of the metalloregulator Fur identify a promoter-binding mechanism and its role in Francisella tularensis virulence.

International audienceFrancisella tularensis is a Gram-negative bacterium causing tularaemia. Classified as possible bioterrorism agent, it may be transmitted to humans via animal infection or inhalation leading to severe pneumonia. Its virulence is related to iron homeostasis involving siderophore biosynthesis directly controlled at the transcription level by the ferric uptake regulator Fur, as presented here together with the first crystal structure of the tetrameric F. tularensis Fur in the presence of its physiological cofactor, Fe2+. Through structural, biophysical, biochemical and modelling studies, we show that promoter sequences of F. tularensis containing Fur boxes enable this tetrameric protein to bind them by splitting it into two dimers. Furthermore, the critical role of F. tularensis Fur in virulence and pathogenesis is demonstrated with a fur-deleted mutant showing an attenuated virulence in macrophage-like cells and mice. Together, our study suggests that Fur is an attractive target of new antibiotics that attenuate the virulence of F. tularensis

Mechanisms of metal(loïd)s accumulation and detoxification in bacteria and plants using synchrotron techniques

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