Résumé : Les crevettes pénéides maintenues captives dans des cages posées sur le fond des bassins d'élevage subissent un stress dû au sédiment qui peut être évalué par la comparaison entre la valeur de la pression osmotique de leur hémolymphe et celle des crevettes libres du même bassin. Les objectifs des travaux réalisés à la station de Saint-Vincent (SASV, Nouvelle Calédonie) étaient de confirmer la variabilité spatiale de l'intensité du stress et de rechercher dans les sédiments un indicateur physique ou chimique corrélé à ce stress. Des lots de 25 à 30 crevettes de 13,2g, pêchées à l'épervier, ont été placés dans des cages de grillage métallique déposées en 12 points du bassin d'élevage. Les cages ont été relevées au bout de 24 heures et la pression osmotique des crevettes au stade d'inter-mue C comparée à celles d'individus libres pêchés le même jour. L'expérience ayant été renouvelée 4 fois, le plan expérimental était constitué de 4 blocs de 12 cages. Les caractéristiques du sédiment ont été étudiées sur deux séries de mesures in situ (pH de l'eau interstitielle, potentiel d'oxydoréduction) ou de prélèvements (matière sèche, taux de matière organique, teneur en azote ammoniacal) réalisés à proximité immédiate du point de dépôt des cages. L'étude révèle l'existence d'un gradient significatif d'intensité du stress chez les crevettes captives, elle a permis de détecter une corrélation linéaire très significative entre le pH de surface des sédiments et la capacité osmorégulatrice des crevettes. Ces observations ont été confirmées par une étude expérimentale réalisée à Tahiti au Centre Océanologique du Pacifique.

Droits : 1997 Ifremer
http://archimer.ifremer.fr/doc/00131/24265/22263.pdf
http://archimer.ifremer.fr/doc/00131/24265/

Éditeur(s) : Academic Press Ltd- Elsevier Science Ltd
Résumé : Antioxidant defences and induced oxidative stress tissue damage of the blue shrimp Litopenaeus stylirostris, under challenge with Vibrio nigriputchritudo, were investigated for a 72-h period. For this purpose, L stylirostris were first infected by immersion with pathogenic V. nigripulchritudo strain SFn1 and then antioxidant defences: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (Gpx), Total antioxidant status (TAS), glutathiones and induced tissue damage (MDA and carbonyl proteins) were determined in the digestive gland at 0, 12, 24, 48 and 72 h post-infection (h.p.i.). In the meantime, TAS was also measured in the blood. Infection level of the shrimps during the challenge was followed by determining V. nigripulchritudo prevalence and load in the haemolymph of the shrimps. Changes in all these parameters during the 72-h.p.i. period were recorded for control shrimps and shrimps previously fed for one month with probiotic Pediococcus aciditactici MA18/5M at 10(7) CFU g(-1) of feed. Our results showed that immersion with V nigripulchritudo led to maximal infection level in the haemolymph at 24 h.p.i. preceding the mortality peak recorded at 48 h.p.i. Significant decreases in the antioxidant defences were detected from 24 h.p.i. and beyond that time infection leaded to increases in oxidative stress level and tissue damage.. Compared to control group, shrimps fed the probiotic diet showed lower infection (20% instead of 45% at 24 h.p.i. in the control group) and mortality (25% instead of 41.7% in the control group) levels. Moreover, infected shrimp fed the probiotic compared to uninfected control shrimps exhibited very similar antioxidant status and oxidative stress level. Compared to the infected control group, shrimps fed the probiotic sustained higher antioxidant defences and lower oxidative stress level. This study shows that bacterial infection leads to oxidative stress in L. stylirostris and highlighted a beneficial effect of P. acidilactici, suggesting both a competitive exclusion effect leading to a reduction of the infection level and/or an enhancement of the antioxidant status of the shrimps. (C) 2010 Elsevier Ltd. All rights reserved.
Fish & Shellfish Immunology (1050-4648) (Academic Press Ltd- Elsevier Science Ltd), 2010-04 , Vol. 28 , N. 4 , P. 622-631

Droits : 2010 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/00003/11419/7984.pdf
DOI:10.1016/j.fsi.2009.12.024
http://archimer.ifremer.fr/doc/00003/11419/

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
With the growing use of selective serotonin reuptake inhibitor medications (SSRIs) for the treatment of depression during the perinatal period, questions have been raised about the longterm impact of these medications on development. We aimed to investigate how developmental SSRI exposure may alter affect-related behaviors and associated molecular processes in offspring using a rodent model of maternal stress and depression. For this purpose, prenatally stressed or non-stressed male offspring were exposed to fluoxetine (5 mg/kg/day) or vehicle, via lactation, until weaning. Primary results show that postnatal fluoxetine exposure differentially altered anxiety-like behavior by increasing anxiety in non-stressed offspring and decreasing anxiety in prenatally stressed offspring. In the hippocampus, developmental fluoxetine exposure decreased BDNF IV and TrkB mRNA expression. Prenatal stress alone also decreased escape behaviors and decreased hippocampal BDNF IV mRNA expression. These data provide important evidence for the long-term programming effects of early-life exposure to SSRIs on brain and behavior.
ISSN: 0012-1630

hal-01305478
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01305478
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01305478/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01305478/file/Developmental%20SSRIs%2C%20anxiety%20and%20BDNF_accepted.pdf
DOI : 10.1002/dev.21385

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Maternal affective disorders are frequently treated with selective serotonin reuptake inhibitor medications (SSRIs); with up to 10% of women being prescribed these medications during pregnancy. Infant development depends on the early serotonergic environment, which is altered by perinatal SSRIs, raising concern about how these medications affect neural outcomes. While clinical and preclinical research suggests an impact of SSRIs on the developing brain, more research is needed to determine the effects on neuroplasticity, the serotonergic system, and the hypothalamic-pituitary-adrenal axis in neural regions mediating behavior. The current work investigated the effects of the SSRI, fluoxetine, on the serotonergic system in the prefrontal cortex (PFC) during pre-adolescence, and changes to synaptic markers and glucocorticoid receptor density in the cingulate cortex (medial PFC) of pre-adolescent and adult Sprague-Dawley male and female rats. To model aspects of Perinatal Depression and maternal anxiety, pre-gestational maternal stress was used resulting in male and female offspring from 4 groups: 1) control, 2) perinatal fluoxetine exposed, 3) pre-gestational maternal stress exposed, and 4) pre-gestational maternal stress + fluoxetine. Perinatal fluoxetine prevented the effects of maternal stress on 5-HT levels and 5-HT turnover ratio in the PFC of pre-adolescent offspring, particularly in females. However, pre-gestational stress reduced synaptophysin and PSD-95 densities in the cingulate cortex, effects that were more pronounced in males. Interestingly, perinatal fluoxetine exposure reduced GR density in adult males in this same brain area. Together, results show differential effects of perinatal SSRIs and pre-gestational maternal stress on neurodevelopment in the PFC of males and females.
ISSN: 0028-3908

hal-01647158
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01647158
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01647158/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01647158/file/Gemmel%20-%20Perinatal%20fluoxetine%20prevents%20the%20effect.pdf
DOI : 10.1016/j.neuropharm.2017.10.009

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
MR and MDHD contributed equally to this work. Summary Painful vaso-occlusive crisis, a hallmark of sickle cell anaemia, results from complex, incompletely understood mechanisms. Red blood cell (RBC) damage caused by continuous endogenous and exogenous oxidative stress may precipitate the occurrence of vaso-occlusive crises. In order to gain insight into the relevance of oxidative stress in vaso-occlusive crisis occurrence , we prospectively compared the expression levels of various oxidative markers in 32 adults with sickle cell anaemia during vaso-occlusive crisis and steady-state conditions. Compared to steady-state condition, plasma levels of free haem, advanced oxidation protein products and myeloperoxi-dase, RBC caspase-3 activity, as well as the concentrations of total, neutrophil-and RBC-derived microparticles were increased during vaso-occlusive crises, whereas the reduced glutathione content was decreased in RBCs. In addition, natural anti-band 3 autoantibodies levels decreased during crisis and were negatively correlated with the rise in plasma advanced oxidation protein products and RBC caspase-3 activity. These data showed an exacerbation of the oxidative stress during vaso-occlusive crises in sickle cell anaemia patients and strongly suggest that the higher concentration of harmful circulating RBC-derived microparticles and the reduced anti-band 3 autoantibodies levels may be both related to the recruitment of oxidized band 3 into membrane aggregates.
ISSN: 0007-1048

inserm-01476067
http://www.hal.inserm.fr/inserm-01476067
http://www.hal.inserm.fr/inserm-01476067/document
http://www.hal.inserm.fr/inserm-01476067/file/2016%2C%20Hierso%20-%20Exacerbation%20of%20oxidative%20stress%20during%20sickle%20vaso-occlusive%20crisis.pdf
DOI : 10.1111/bjh.14476

Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
Although magmatism may occur during the earliest stages of continental rifting, its role in strain accommodation remains weakly constrained by largely 2-D studies. We analyze seismicity data from a 13 month, 39-station broadband seismic array to determine the role of magma intrusion on state-of-stress and strain localization, and their along-strike variations. Precise earthquake locations using cluster analyses and a new 3-D velocity model reveal lower crustal earthquakes beneath the central basins and along projections of steep border faults that degas CO2. Seismicity forms several disks interpreted as sills at 6-10 km below a monogenetic cone field. The sills overlie a lower crustal magma chamber that may feed eruptions at Oldoinyo Lengai volcano. After determining a new ML scaling relation, we determine a b-value of 0.87±0.03. Focal mechanisms for 65 earthquakes, and 13 from a catalogue prior to our array reveal an along-axis stress rotation of ∼60° in the magmatically active zone. New and prior mechanisms show predominantly normal slip along steep nodal planes, with extension directions ∼N90°E north and south of an active volcanic chain consistent with geodetic data, and ∼N150°E in the volcanic chain. The stress rotation facilitates strain transfer from border fault systems, the locus of early-stage deformation, to the zone of magma intrusion in the central rift. Our seismic, structural, and geochemistry results indicate that frequent lower crustal earthquakes are promoted by elevated pore pressures from volatile degassing along border faults, and hydraulic fracture around the margins of magma bodies. Results indicate that earthquakes are largely driven by stress state around inflating magma bodies.
ISSN: 1525-2027

hal-01667198
https://hal.archives-ouvertes.fr/hal-01667198
DOI : 10.1002/2017GC007027

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A series of two-stage torsion experiments on Carrara marble were conducted to constrain the influence of known prior deformation on rheological response and microstructural evolution. Comparison with previous experimental data on Carrara marble flow and fabric evolution during single-stage torsion deformation experiments provided direct insights into the significance of initial deformation at various conditions. Our experiments were conducted at 727 degrees C temperature and 300 MPa confining pressure, while maintaining a constant strain rate of 3 x 10(-4) s(-1) on the periphery of the cylindrical samples. Under these conditions, the marble is known to deform in power-law (n = 6-10) ductile flow. All torsion experiments were performed with a Paterson type gas-medium testing machine equipped with a torsion actuator module.;Prior (D1) and subsequent (D2) deformation are accomplished by two torsion experiments in sequence on same sample segments. The effect of D1 strain history is investigated during D2 by applying counter-clockwise torsion to a sandwich sample consisting of three segments with different D1 rotation sense. D2 samples experienced continued, first and reversed shearing deformation in top, centre and bottom segments, respectively. D2 bulk strain was chosen equal to D1 strain in top and bottom segments.;D1 experiments followed the typical single-stage deformation behaviour of Carrara marble under the applied experimental conditions. Yielding was followed by strain hardening until a peak stress was reached at a shear strain around 1, after which work softening occurred. Weakening gradually evolved into a constant stress regime. During hardening, a shear microstructure and crystallographic preferred orientation (CPO) developed. Afterwards the volume fraction of smaller dynamic recrystallised grains increased continuously, resulting in a recrystallisation microstructure and CPO at shear strains of 5 and higher. The new D2 experiments displayed a strain variation between homogeneously deformed sample segments that increased with increasing D1 strain. The stress-strain behaviour of the D2 bulk sandwich samples showed less pronounced work-hardening and -softening when compared with single-stage deformation experiments. Furthermore, constant flow stress was attained at increasingly lower strain with increasing D1 strain. In most D2 segments, fabric development is equivalent to single-stage experiments at corresponding absolute strain. The fabrics differed markedly from those in single-stage experiments in the case of reversed two-stage deformation at moderate strain (D1 shear strain 1 and 2.6). Experiments show that grain shape by shearing of relict grains is defined by finite strain and thus affected by strain reversal. Recrystallisation is controlled by absolute strain and not influenced by strain reversal.
ISSN: 0040-1951

hal-00617686
https://hal.archives-ouvertes.fr/hal-00617686
DOI : 10.1016/j.tecto.2010.09.029

Éditeur(s) : Université des Antilles AREBio Groupe de recherche BIOSPHERES : BIOlogie, Sciences Physiques & Humaines pour les énergies Renouvelables, l
Extrait de : 1er colloque international BIOSPHERES, du 18 au 20 juin 2019. Université des Antilles
Description : Au-delà des pertes matérielles et humaines, les catastrophes naturelles peuvent générer des troubles psychiques importants, comme le syndrome de stress post-traumatique (TSPT), qui perdure plusieurs années et génère une grande souffrance. On s'est particulièrement intéressé à l'apparition de TSPT, en lien avec le soutien social et l'attachement au lieu, puisque ces facteurs sont susceptibles de médiatiser certains symptômes, comme l'évitement ou la reviviscence. Les résultats, obtenus auprès de sinistrés, mettent en évidence ces liens, notamment concernant l'attachement affectif au domicile et à la ville. Ils permettent ainsi de réfléchir d'une part à une prise en charge des victimes intégrant ces aspects, et d'autre part à l'information et à la communication, notamment en amont et au moment de l'alerte.

Droits : CC-BY-NC-ND - Attribution - Pas d'utilisation commerciale - Pas de modification
Permalien : http://www.manioc.org/fichiers/V19085
V19085

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : The paper focuses on investigation of the importance of nature and development of tourism in protected areas. Therefore, in this context a new challenge is emerging: the need to conserve and protect bio and geo diversity, as well as the economic valorisation of these areas based mainly on tourism and leisure. At EU level, Natura 2000 protected areas have developed, implemented and cultivated the need to practice sport and recreational activities in these areas both for spending leisure time and also as stress antidote. The recreational and sporting practices that can be undertaken within the ecological network Natura 2000 sites adapted to the specificity of each protected area, in close connection with the environmental conditions. For the preservation of the natural environment should develop and maintain a close collaboration with tourism and sports associations that organize such activities in those areas.
La réflexion est centrée sur l’importance de la nature et des enjeux du développement de tourisme dans les aires protégées. Un nouveau défi émerge dans le contexte actuel où il s'agit de concilier le besoin de conserver et de protéger la géodiversité et la biodiversité avec la valorisation économique de ces espaces naturels investis par les pratiques touristiques et récréatives. Au niveau de l'Union européenne, les espaces protégés Natura 2000 ont mis en œuvre des programmes permettant de répondre à l’accueil des activités sportives et de loisirs dans ces zones, tant pour passer du temps libre que comme antidote au stress. Ces pratiques entreprises dans le réseau écologique Natura 2000 sites sont adaptés à la spécificité de chaque secteur protégé, en relation avec les conditions environnementales. Pour favoriser la conservation du cadre naturel, il est important de maintenir une étroite collaboration avec les associations touristiques et sportives qui organisent des activités dans ces zones.
Bihor
Roumanie

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.11262
http://journals.openedition.org/etudescaribeennes/11262

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We review the evolution of concepts on and methods of estimating the state of stress from fault movements. Theories of failure in isotropic materials suggested a simple geometrical construction of optimal principal stress directions from a fault plane and its associated slip. These optimal directions align shear stress and slip directions and maximize the difference between shear stress and frictional resistance on the fault plane. Optimal stress directions for calcite twinning are obtained by a similar construction, with the difference that they maximize shear stress. Force representation of seismic sources independently introduced pressure, P, and tension, T, axes at positions that also maximize shear stress on both nodal planes. Frictional slip theory and the constraint that slip and shear stress directions be parallel allowed to address reactivation of pre-existing faults. This suggested that stress could also be inverted from reactivated fault and slip data or earthquake focal mechanisms. Early methods relied on geometrical constructions as a substitute for calculations, whereas later methods relied on software as these calculations became tractable with the help of computers. Similar methods were developed for the inversion of stress from crystal twin gliding with non-optimal geometry, with a different criterion that relies on a threshold of the component of shear stress along the gliding line. Even though these methods seek a common stress tensor compatible with fault and slip data, their main use is to separate polyphase data into homogeneous subsets and help deciphering complex tectonic histories. Fault and slip data can also be analyzed to constrain the strain rather than the stress tensor. In most cases this involves a summation and yields an average strain for the considered rock volume. Stress inversion thus appears better suited for differentiating heterogeneous data whereas strain analysis appears better suited for homogenizing them.
ISSN: 0040-1951

hal-00759043
https://hal.archives-ouvertes.fr/hal-00759043
DOI : 10.1016/j.tecto.2012.02.009

Éditeur(s) : HAL CCSD
Résumé : The ecological success of cnidarian-dinoflagellate symbiosis mainly relies on nutrient recycling. Environmental changes, such as global warming or pollution, often result to symbiosis breakdown, also called cnidarian bleaching. The understanding of mechanisms regulating the symbiosis establishment, maintenance and breakdown is essential to prevent massive bleaching phenomena. In this respect, my PhD project focused on the characterization of chemical mediators expressed in the sea anemone Anemonia viridis, their localization and their modulation by stress conditions. A comparative study was first conducted to characterize the chemical mediators and analyze their distribution within the symbiotic sea anemone. We described a great abundance and diversity of lipids in A. viridis tissues. From these results, we proposed possible transfers of FAs between the symbiotic partners. A thermal stress and a chemical stress have also been applied in laboratory-controlled conditions in order to induce symbiosis breakdown and bleaching of the sea anemones, in order to correlate A. viridis metabolome to its symbiotic status. A mapping of these metabolites has been performed by MALDI-MSI of tentacle cross-sections, as well as their evolution following stress. Some betaine lipids have thus been proposed as short-term indicators of stress. A. viridis stress response has also been evaluated with a lipidomic approach, and allowed to identify 3 lipid indicators of early stress response based on membrane fluidity markers. Overall, this study provides insight on key chemical mediators that may regulate the symbiosis maintenance, and may contribute to the symbiosis breakdown.
Le succès évolutif des Cnidaires symbiotiques réside en grande partie dans leurs échanges trophiques établis avec les Dinoflagellés du genre Symbiodinium. Cependant, le réchauffement climatique global ainsi que les pollutions ont un impact fort sur les écosystèmes coralliens, notamment en conduisant à la rupture de la symbiose, phénomène appelé blanchissement. La compréhension des mécanismes qui régissent l’établissement, le maintien et la rupture de la symbiose est essentielle à la prévention des épisodes de blanchissement massif. Dans ce contexte, les objectifs de mon projet de thèse sont de caractériser les médiateurs chimiques de l’anémone de mer Anemonia viridis, de les localiser, et d’analyser leur réponse face à un stress. Parmi les composés caractérisés, les lipides et les bétaïnes sont les plus abondants et présentent une grande diversité. Certains sont transférés des symbiotes vers l’hôte. Des anémones de mer ont ensuite été traitées en laboratoire afin de provoquer la rupture de la symbiose et le blanchissement des individus. Une étude cinétique a été menée par une approche globale comparative identique à celle réalisée sur l’anémone symbiotique. Par ailleurs, une cartographie de l’évolution de composés clé a été réalisée par MALDI-MSI. La réponse au stress a été évaluée et a permis d’identifier des lipides de bétaïne et trois indicateurs lipidiques comme marqueurs de réponse précoce au stress. L’ensemble de ces résultats apporte de nouveaux éléments de réponse concernant le rôle des médiateurs chimiques clés dans le maintien de la symbiose, ainsi que leur influence sur sa rupture.
https://tel.archives-ouvertes.fr/tel-01310668

NNT : 2015NICE4108
tel-01310668
https://tel.archives-ouvertes.fr/tel-01310668
https://tel.archives-ouvertes.fr/tel-01310668/document
https://tel.archives-ouvertes.fr/tel-01310668/file/2015NICE4108.pdf

Éditeur(s) : EDP Sciences
Résumé : During 84 days, the effects of density on juvenile sea bass (Dicentrarchus labrax) (76 +/- 16 g) were studied in an experimental tank-based flow through system. Performance, stress response and resistance to virus infection were analysed under five stabilized rearing densities: 10, 20, 40, 70 and 100 kg m(-3). Water quality parameters (CO2, total ammonia nitrogen and O-2) were measured and maintained close to the recommended values for farmed sea bass by adjusting water renewal exchange. No significant differences were observed between density treatments, neither on stress response (cortisol) nor susceptibility to nodavirus. With regards to biological performances, the daily feed intake and specific growth rate were significantly lower in fish reared at the 100 kg m(-3) density. Results on the effects of density in sea bass reared in flow through (present study) and in recirculating aquaculture systems (RAS) (Sammouth et al. 2009) were compared as a contribution to the identification of density not affecting health and welfare in farmed sea bass.
Aquatic Living Resources (0990-7440) (EDP Sciences), 2010-01 , Vol. 23 , N. 1 , P. 109-117

Droits : 2010 EDP Sciences, IFREMER, IRD
http://archimer.ifremer.fr/doc/00002/11287/7824.pdf
DOI:10.1051/alr/2009056
http://archimer.ifremer.fr/doc/00002/11287/

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Among the environmental threats to coral reef health, temperature and ultraviolet increases have been proposed as major agents, although the relative contribution of each in the cnidarian/zooxanthellae symbiosis breakdown has been poorly addressed. We have investigated the transcriptomic response to thermal stress, with and without ultraviolet radiation (UVR), in the symbiotic sea anemone Anemonia viridis. Using the Oligo2K A.similar to viridis microarray, dedicated to genes potentially involved in the symbiosis interaction, we monitored the gene expression profiles after 1, 2 and 5 days of stresses that further lead to massive losses of zooxanthellae. Each stress showed a specific gene expression profile with very little overlap. We showed that the major response to thermal stress is immediate (24 h) but returns to the baseline gene expression profile after 2 days. UVR alone has little effect but potentiates thermal stress, as a second response at 5 days was observed when the two stresses were coupled. Several pathways were highlighted, such as mesoglea loosening, cell death and calcium homeostasis and described in more details. Finally, we showed that the dermatopontin gene family, potentially involved in collagen fibrillogenesis, issued from actinarian-specific duplication events, with one member preferentially expressed in the gastroderm and specifically responding to stress.
ISSN: 0962-1083

hal-01546174
https://hal.archives-ouvertes.fr/hal-01546174
DOI : 10.1111/j.1365-294X.2012.05458.x

Éditeur(s) : HAL CCSD
Résumé : International audience
In most rock mechanical testing devices, the texture developed during deformation is only observed after the failure, and the detailed mapping of cracks and pore structure evolution, just before or after rupture, remains speculative. Computerized X-ray tomography (CT X-ray) offers a way to observe 'in vivo' some characteristics of a tested sample in the course of its deformation. Therefore we developed an X-ray transparent tri-axial cell that was included in a medical purpose X-ray scanner with a volumetric resolution of the order of 1 mm3. This technique is described and applied to a porous calcarenite, which is regularly scanned for porosity evolution during mechanical testing. The experiment is performed at low confining pressure (2-10 MPa). During testing, an axial load is applied until failure and is then progressively decreased. In these experiments, the peak stress is preceded by phase of diffuse dilatancy. After failure localization, the axial stress is unloaded until the stress reaches isotropy. During this unloading phase, the previous diffuse dilatancy is lost due to an elastic relaxation. Then, the stress is completely relaxed. At this moment the dilatancy increases again and the residual dilatancy is larger than that reached at the peak stress. When observed "post mortem" at microscopic scale, the dilatant structures are comprised of cataclastic deformation bands and cracks in some larger crystals.
International Journal of Rock Mechanics and Mining Science

hal-00767563
https://hal.archives-ouvertes.fr/hal-00767563
DOI : 10.1016/j.ijrmms.2012.07.020

Éditeur(s) : Edp Sciences S A
Résumé : Reared sea bass were submitted to six stressful situations: hyperoxia with or without hypercapnia, increased stocking density in an open flow or recirculating system, transfer to another tank and nodavirus injection. The potentially negative impact of these factors on the lives of sea bass was investigated by measuring 9 water parameters and 19 fish parameters including total serum protein (TSP). TSP has already been used to evaluate stress. The present study investigates data of previous and new experiments, concentrating on the potential use of TSP as a routine indicator to assess welfare in sea bass reared on fish farms. In the current experiment, oxygen and carbon dioxide were seen to affect levels of TSP, but alterations were too erratic to enable proper comparison, probably because they are normal components of the fish environment and become toxic only by dose increase. TSP decreased when stocking density increased. After transfer to another tank, TSP decreased to 14% for three weeks and then increased during the fourth week through compensative overproduction, before returning to normal levels after 2 months. The results confirmed that transfer is an important stress factor for fish, with cumulative effects for successive transfers. TSP alteration of nodavirus-injected fish depends on the type of symptoms, which can be divided into 3 groups: (i) dying fish, in which TSP increased sharply due to over-production of protein involved in non-specific defences and inflammation, then decreased dramatically before death; (ii) whirling fish, a group that included both fish that later died, in which TSP decreased, and fish that subsequently survived, in which TSP increased due to development of specific immunity; and (iii) asymptomatic fish, in which TPS was similar to control levels and which were probably insensitive to nodavirus and/or had developed defences. In this paper, different mechanisms of TSP alteration are proposed and the interest of TSP as a field parameter is discussed. TSP is a non-destructive parameter that is robust, easy to measure everywhere and cheap, representing a suitable way of monitoring the overall welfare of fish by its regular increase. It can be used only as a "warning" of poor rearing conditions, however, and further investigations would be needed to identify the specific stress or health disorder.
Aquatic Living Resources (0990-7440) (Edp Sciences S A), 2011-04 , Vol. 24 , N. 2 , P. 121-127

Droits : EDP Sciences, IFREMER, IRD 2011
http://archimer.ifremer.fr/doc/00043/15382/12740.pdf
DOI:10.1051/alr/2011130
http://archimer.ifremer.fr/doc/00043/15382/

Éditeur(s) : HAL CCSD
Résumé : International audience
Trees can control their shape and resist gravity thanks to their ability to produce wood under tensile stress. This stress is known to be produced during the maturation of wood fibres but the mechanism of its generation remains unclear. This study focuses on the formation of the secondary wall in tension wood produced in artificially tilted poplar saplings. Thickness of secondary wall layer (SL) and gelatinous layer (GL) were measured from cambium to mature wood in several trees sampled at different times after tilting. Measurements on wood fibres produced before tilting show the progressive increase of secondary wall thickness during the growing season. After the tilting date, SL thickness decreased markedly from normal wood to tension wood while the total thickness increased compared to normal wood, with the development of a thick GL. However, even after GL formation, SL thickness continues to increase during the growing season. GL thickening was observed to be faster than SL thickening. The development of the unlignified GL is proposed to be a low cost, efficient strategy for a fast generation of tensile stress in broadleaved trees.
IAWA journal / International Association of Wood Anatomists.

hal-01229277
https://hal.archives-ouvertes.fr/hal-01229277
https://hal.archives-ouvertes.fr/hal-01229277/document
https://hal.archives-ouvertes.fr/hal-01229277/file/AbediniClair-Iawa-TensionCellWallThickening_preprint_HAL.pdf
DOI : 10.1163/22941932-00000084

Éditeur(s) : HAL CCSD MDPI
Résumé : International audience
The future of tropical managed forests is threatened by climate change. In anticipation of the increase in the frequency of drought episodes predicted by climatic models for intertropical regions, it is essential to study commercial trees' resilience and vulnerability to water stress by identifying potential interaction effects between selective logging and stress due to a lack of water. Focusing on 14 species representing a potential or acknowledged commercial interest for wood production in the Guiana Shield, a joint model coupling growth and mortality for each species was parametrized, including a climatic variable related to water stress and the quantity of aboveground biomass lost after logging. For the vast majority of the species, water stress had a negative impact on growth rate, while the impact of logging was positive. The opposite results were observed for the mortality. Combining results from growth and mortality models, we generate vulnerability profiles and ranking from species apparently quite resistant to water stress (Chrysophyllum spp., Goupia glabra Aubl., Qualea rosea Aubl.), even under logging pressure, to highly vulnerable species (Sterculia spp.). In light of our results, forest managers in the Guiana Shield may want to conduct (i) a conservation strategy of the most vulnerable species and (ii) a diversification of the logged species. Conservation of the already-adapted species may also be considered as the most certain way to protect the tropical forests under future climates.
ISSN: 1999-4907

hal-01315432
https://hal-sde.archives-ouvertes.fr/hal-01315432
DOI : 10.3390/f7050105

Éditeur(s) : Innotermer, Brest, Novembre 1982
Résumé : Les échanges de Matériels vivants apparaissent comme une caractéristique constante de toute aquaculture, y compris de la conchyliculture traditionnelle. Ils interviennent par exemple sous forme d'animaux adultes mis sur le marché pour être consommés vivants, ou sous forme de naissain ou d'alevins d'importation, ou encore lors des essais d'acclimatation d'une espèce étrangère en vue de sa culture. A cela s'ajoutent les transferts au cours du développement : c'est ce dernier aspect qui retiendra surtout notre attention. Dans la mesure où l'aquaculture nouvelle cherche à maîtriser tous les stades du développement de l'œuf à l'adulte, les échanges ou transferts d'animaux vivants deviennent obligatoires : en effet, on ne saurait réaliser au même endroit l'élevage de larves pélagiques et celui des adultes. Ces échanges constituent le plus souvent une pierre d'achoppement car ils nécessitent des passages soit hors d'eau, soit dans des enceintes de taille réduite, ce qui provoque un stress sur les animaux manipulés. Mais inversement, la réussite technique de ces échanges est un gage de progrès en aquaculture. Pour illustrer ce problème, nous examinerons deux produits de caractéristiques différentes : les mollusques et les poissons.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00049/16001/13446.pdf
http://archimer.ifremer.fr/doc/00049/16001/

Éditeur(s) : Agro Paris Tech
Résumé : P. acidilactici MA 18/5M is a dietary probiotic (BACTOCELL®) which has shown its efficiency on several terrestrial and aquatic species. The present thesis aimed to investigate more fully the effects of this probiotic on cultured penaeid shrimps. For this study, we chose a global approach by replacing the problem studied in a model of interactions between three compartments: the shrimp, its intestinal microflora and the probiotic. Having first defined how the probiotic should be administrated, we studied its effects under controlled laboratory conditions at several levels of Litopenaeus stylirostris biology: (i) Nutritional status and growth, (ii) associated bacterial microflora, and (iii) health status with respect to oxidative stress. Then the probiotic improves the growth of the shrimps and the feed conversion ratio. Our study shows that these effects are partially due to a better use of the feed, particularly of dietary carbohydrates, but also suggest an action on the metabolism, andor on the growth via a contribution of essential nutrients. On the other hand, although the intestinal bacterial communities seems little affected, we show an antagonism effect of the probiotic toward total and vibrionacea intestinal flora, as well as a decrease in the level of infection of shrimps during challenge with pathogenic V. nigripulchritudo. Beside, our works highlight that infection by this pathogen, led to a reduction in antioxidant defences, to a rise in oxidative damages, and to a release of mortalities within 48 hours. This oxidative stress following bacterial infection was better controlled by animals receiving the probiotic diet, and resistance of the shrimps to infection was significant improved. A nutritional hypothesis is proposed to explain such result, hypothesis based on a link between carbohydrate metabolism and antioxidant status. As a conclusion of these works, we can propose a first explanatory scenario for the effects of P. acidilactici on a penaeid shrimp. Finally probiotic's effects were assessed under a pilot scale in a commercial farm from New Caledonia currently affected by the "summer syndrome ". We confirm the improvements brought in term of zootechnical results, with in particular, a better resistance to this syndrome. This work was made possible thanks to a breeding method in floating cages, developed during this thesis, and therefore transferred, as an experimental tool, to the shrimp industry of New Caledonia.
Pediococcus acidilacticii MA18/5M est un probiotique bactérien (BACTOCELL®) qui a démontré son efficacité chez plusieurs espèces d'animaux terrestres et aquatiques. Cette thèse avait pour objectif d'investiguer plus en détails les effets de ce probiotique chez les crevettes pénéides d'élevage. Pour cette étude, nous avons choisi une approche globale replaçant la problématique dans un modèle d'interactions entre trois compartiments : la crevette, sa microflore intestinale et le probiotique. Après avoir défini les modalités d'administration, l'effet de P. acicilactici a été étudié, en conditions de laboratoire, chez la crevette Litopenaeus stylirostris, à différents niveaux: (i) statut nutritionnel et croissance, (ii) microflore bactérienne associée, et (iii) santé de l'animal à travers son statut antioxydant et son niveau de stress oxydant. Ainsi, le probiotique améliore la croissance des crevettes et l'indice de conversion de l'aliment. Notre étude montre que ces effets sont en partie liés à une meilleure utilisation de l'aliment, notamment des carbohydrates alimentaires, mais suggèrent aussi une action sur le métabolisme, et/ou sur la croissance via un apport de nutriments essentiels. D'autre part, bien que les communautés bactériennes intestinales semblent peu affectées, un effet d'antagonisme du probiotique vis-à-vis de la flore intestinale totale et vibrionacée a été montré, ainsi qu'une réduction du niveau d'infection des crevettes au cours de challenge avec le pathogène V. nigripulchritudo. Par ailleurs, nous mettons en évidence que l'infection par ce pathogène, conduit à un abaissement des défenses antioxydantes, à une élévation des dégâts oxydatifs, et au déclenchement de mortalités dans les 48 heures. Le probiotique atténue le niveau de ce stress oxydant, et améliore significativement la résistance des crevettes à l'infection. Une hypothèse nutritionnelle est proposée afin d'expliquer ce résultat, hypothèse reposant sur un lien entre le métabolisme des carbohydrates et le statut antioxydant. A l'issue de ces travaux, nous pouvons alors proposer un premier scénario explicatif des effets de P. acidilactici chez une crevette pénéide. Finalement le probiotique a été éprouvé à l'échelle pilote sur une ferme commerciale de Nouvelle-Calédonie affectée par le « syndrome d'été ». Nous confirmons les améliorations apportées en termes de résultats zootechniques, avec notamment une meilleure résistance au syndrome. Ce travail a été réalisé grâce une méthode d'élevage en cages flottantes, mis au point au cours de cette thèse, et qui a dés lors été transférée, comme outil expérimental, à la filière crevetticole Calédonienne.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2009/these-6814.pdf
http://archimer.ifremer.fr/doc/00000/6814/

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Assessing seismic hazards remains one of the most challenging scientific issues in Earthsciences. Deep tectonic processes are classically considered as the only persistentmechanism driving the stress loading of active faults over a seismic cycle. Here we show via amechanical model that erosion also significantly influences the stress loading of thrust faultsat the timescale of a seismic cycle. Indeed, erosion rates of about B0.1–20mmyr1, asdocumented in Taiwan and in other active compressional orogens, can raise the Coulombstress by B0.1–10 bar on the nearby thrust faults over the inter-seismic phase. Masstransfers induced by surface processes in general, during continuous or short-lived andintense events, represent a prominent mechanism for inter-seismic stress loading offaults near the surface. Such stresses are probably sufficient to trigger shallow seismicity orpromote the rupture of deep continental earthquakes up to the surface.
ISSN: 2041-1723

insu-01087103
https://hal-insu.archives-ouvertes.fr/insu-01087103
https://hal-insu.archives-ouvertes.fr/insu-01087103/document
https://hal-insu.archives-ouvertes.fr/insu-01087103/file/Steer2014_NatureComm_accepted.pdf
DOI : 10.1038/ncomms6564