Éditeur(s) : HAL CCSD Springer Verlag (Germany)
Résumé : International audience
*Context: Tree orientation is controlled by asymmetric mechanical stresses set during wood maturation. The magnitude of maturation stress differs between longitudinal and tangential directions, and between normal and tension woods. * Aims: We aimed at evaluating patterns of maturation stress on eucalypt plantation trees and their relation with growth, with a focus on tangential stress evaluation. * Methods: Released maturation strains along longitudinal and tangential directions were measured around the circumference of 29 Eucalyptus nitens trees, including both straight and leaning trees. * Results: Most trees produced asymmetric patterns of longitudinal maturation strain but more than half of the maturation strain variability occurred between trees. Many trees produced high longitudinal tensile stress all around their circumference. High longitudinal tensile stress was not systematically associated with the presence of gelatinous layer. The average magnitude of released longitudinal maturation strain was found negatively correlated to the growth rate. A methodology is proposed to ensure reliable evaluation of released maturation strain in both longitudinal and tangential directions. Tangential strain evaluated with this method was lower than previously reported. * Conclusion: The stress was always tensile along longitudinal direction and compressive along tangential direction, and their respective magnitude was positively correlated. This correlation does not result from a Poisson effect but may be related to the mechanism of maturation stress generation.
Annals of Forest Science

hal-00913611
https://hal.archives-ouvertes.fr/hal-00913611
https://hal.archives-ouvertes.fr/hal-00913611/document
DOI : 10.1007/s13595-013-0318-4

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 Springer Verlag
Résumé : A hypothetical mechanism for the generation of maturation stress in wood was tested experimentally. The hypothesis was that the maturation stress could partly originate in a physical mechanism related to daily changes in water pressure and associated diurnal strains. The matrix of lignin and hemicellulose, deposited in the cell wall during the night, would be put in compression by the effect of water tension during the next day. The cellulose framework, crystallizing during the day, would be put in tension by the decrease in tension at night and subsequent cell-wall swelling. This was tested on young saplings of sugi and beech. Half of the saplings were submitted to continuous lighting, which canceled diurnal strains. Saplings were tilted 40 degrees, and their uprighting movement was measured. The uprighting movement is directly due to the production of reaction wood and the concomitant development of large longitudinal maturation stress. It occurred in the continuously lighted plants at least as much as in control plants. We conclude that the generation of longitudinal maturation stress in tension or compression wood is not directly related to variations in water pressure and diurnal strains.
ISSN: 1435-0211

hal-01031891
https://hal.archives-ouvertes.fr/hal-01031891
DOI : 10.1007/s10086-005-0788-6

Éditeur(s) : HAL CCSD Springer-Verlag Berlin Heidelberg
Résumé : International audience
The main biological function of reaction wood is to act as " muscle " for trees, enabling them to control their posture. The key property to achieve this function is the development of high mechanical stress during the formation of reaction wood cells, called " maturation strains ". Actually, reaction wood formation is basically the asymmetric formation of wood around the tree circumference, with higher maturation strains on the side where reaction wood is formed than on the opposite side. This asymmetry enables stems to bend upward or to compensate for the downward bending induced by gravity. At the cross section level, the performance in this biological function is linked not only to the magnitude of this asymmetry but also to an effect of the cross-sectional size (diameter) of the stem. Eccentric growth and variations in wood mechanical stiffness are second order effects that can modify this performance. Differences in maturation strains between reaction and non-reaction woods are related to their specific cell wall structure and composition. The swelling of the cell wall matrix during maturation and the effect of microfibril angle explain the differences in maturation strains between normal and compression wood. However, this mechanism fails in explaining the high maturation shrinkage of tension wood, and several hypotheses at the molecular levels are still under debate. How trees perceive their gravitational disequilibrium is also an open question for physiologists. Integrative biomechanical modelling (from the polymer level to the cell wall, cross section and whole tree levels) enables defining key variables that explain the performance of reaction wood as a system that insures the stem motricity. Maturation strains can be precisely measured only in recently formed wood at the tree surface, but their changes during the whole tree life can also be estimated by retrospective dendrochronological analysis through structural markers of reaction wood. Lastly, wood in living trees ensures general storage, defence, vascular and skeletal functions, that ask general questions about synergies and trade-offs as the structural characteristics of reaction wood can affect all these functions.
The Biology of Reaction Wood

ISBN : 978-3-642-10813-6
hal-01452085
https://hal.archives-ouvertes.fr/hal-01452085
https://hal.archives-ouvertes.fr/hal-01452085/document
https://hal.archives-ouvertes.fr/hal-01452085/file/Chap_Gril_al_Biomechanical_action_biological_functions_2014.pdf

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
In order to progress in the understanding of mechanical stress generation, the mesoporosity of the cell wall and its changes during maturation of poplar (Populus deltoides x P. nigra) tension wood (TW) and opposite wood (OW) were measured by nitrogen adsorption–desorption. Variations in the thickness of the gelatinous layer (G-layer) were also measured to clarify whether the mesoporosity change simultaneously with the deposition of the G-layer in TW. Results show that mesoporous structures of TW and OW were very similar in early development stages before the deposition of G-layers. With the formation of the S2 layer in OW and the G-layer in TW, the mesopore volume decreased steeply before lignification. However, in TW only, the decrease in mesopore volume occurred together with the pore shape change and a progressive increase in pore size. The different patterns observed in TW revealed that pores from G-layers appear with a different shape compared to those of the compound middle lamella, and their size increases duringthe maturation process until stabilising in mature wood. This observation strongly supports the hypothesis of the swelling of the G-layer matrix during maturation as the origin of maturation stress in poplar tension wood.
ISSN: 0028-646X

hal-01081834
https://hal.archives-ouvertes.fr/hal-01081834
https://hal.archives-ouvertes.fr/hal-01081834/document
https://hal.archives-ouvertes.fr/hal-01081834/file/Chang_al_Mesoporosity_changes_New-Phyto._2015.pdf
DOI : 10.1111/nph.13126

Résumé : Since 1993, the New Caledonian shrimp industry has been faced with cold season mortality outbreaks of multifactorial origin. This pathology called “Syndrome 93” affects as well animals in grow-out ponds as broodstock after their transfer in maturation room, with up to 35% of mortality in 48 hours. From literature data and physiological studies on Litopenaeus stylirostris, several combinations of three abiotic parameters (temperature, salinity and feeding) have been tested during the breeders stocking period. This research allowed us to lower stress factors impact and to propose a transfer protocol which leads to an optimal physiological comfort of the animal. Results showed that survival rate is improved and spawning rates are twice higher. These findings have come up with a routine protocol of carrying out any transfer in a tank with water at temperature of 26°C, salinity of 26 ppt and no food supply during 48 hours. The use of this protocol in a commercial hatchery led to a significant broodstock survival improvement.
Depuis 1993, la filière crevetticole calédonienne est confrontée aux mortalités de saison froide dont les causes sont multifactorielles. Cette pathologie appelé « Syndrome 93 » affecte non seulement les animaux dans les bassins de grossissement, mais elle touche également les géniteurs après leur transfert en salle de maturation, les pertes pouvant atteindre 35% en 48 heures. A partir de la littérature et d’études physiologiques de la Litopenaeus stylirostris, différentes combinaisons de trois paramètres abiotiques (température, salinité et alimentation) ont été testés lors de la stabulation des reproducteurs en salle de maturation. Ces recherches ont permis de diminuer l’impact des facteurs de stress et d’établir un protocole de transfert des animaux dans les conditions de confort physiologique optimale. Les résultats montrent que la survie est améliorée mais que le pourcentage de pontes est également doublé. Il est maintenant recommandé pour tout transfert, de prévoir des bacs de réception dans lesquels l’eau est à la température de 26°C, la salinité à 26 ppt et de ne fournir aucune alimentation pendant 48 heures. L’application de ce protocole dans une écloserie privée a démontré un gain substantiel sur la survie des géniteurs.

Droits : 2008 Ifremer
http://archimer.ifremer.fr/doc/00118/22970/20800.pdf
http://archimer.ifremer.fr/doc/00118/22970/

Éditeur(s) : HAL CCSD
Résumé : International audience
A key element of the biomechanical design of trees is their ability to generate largemechanical stresses in wood at the stem periphery. This function is necessary for the tree tocontrol the orientation of its axes, and therefore to grow in height, maintain its branches at anoptimal angle or achieve adaptive reorientations (Fournier et al., 2013). This “maturationstress” appears in wood fibres during their cellular maturation when their secondary cell wallis thickening. In hardwoods, the stress asymmetry is generated by the formation of specificfibres with a very high tensile growth stress on the upper side of the inclined axis. Theresulting tension wood has microstructural features highly different from the normal wood.Tension wood in almost all temperate species has a specific gelatinous cell wall layer, calledG-layer, that is not lignified and highly mesoporous (Chang et al., 2015). It has been shownrecently, at the macroscopic scale, that cellulose tension appears during maturation and issynchronous with the development of this specific layer (Clair et al., 2011). Tropical species,like simarouba, are able to generate lignified tension wood fibres. The mechanisms of stressgeneration in tension wood fibres are not yet well known. The aim of our study is tounderstand these mechanisms and to know the spatial and temporal kinetics of the differentcell wall layers stiffening during maturation, in parallel with tensile stress generation.Contact-Resonance Atomic Force Microscopy, CR-AFM, was used here to address thisquestion on embedded samples (Arnould and Arinero, 2015) using dual resonance frequencytracking (DRFT, Rodriguez et al., 2007). Change in the contact modulus between, and within,each layer of the cell wall has been measured on several radial lines of developing fibres atdifferent steps. In order to understand the obtained results, and to estimate the sensitivity ofthe AFM indentation-like technique to the different cell wall components stiffness, an elasticanisotropic indentation model was used (Vlassak et al., 2003; Jäger et al., 2011). Finally,these mechanical measurements have been compared to topochemical data obtained on thesame fibres.
8th Plant Biomechanics International Conference
Nagoya, Japan

hal-01436113
https://hal.archives-ouvertes.fr/hal-01436113

Éditeur(s) : HAL CCSD Royal Society
Résumé : International audience
Trees control their posture by generating asymmetric mechanical stress around the periphery of the trunk or branches. This stress is produced in wood during the maturation of the cell wall. When the need for reaction is high, it is accompanied by strong changes in cell organization and composition called reaction wood, namely compression wood in gymnosperms and tension wood in angiosperms. The process by which stress is generated in the cell wall during its formation is not yet known, and various hypothetical mechanisms have been proposed in the literature. Here we aim at discriminating between these models. First, we summarize current knowledge about reaction wood structure, state and behaviour relevant to the understanding of maturation stress generation. Then, the mechanisms proposed in the literature are listed and discussed in order to identify which can be rejected based on their inconsistency with current knowledge at the frontier between plant science and mechanical engineering.
Journal of the Royal Society Interface

hal-01392832
https://hal.archives-ouvertes.fr/hal-01392832
https://hal.archives-ouvertes.fr/hal-01392832/document
https://hal.archives-ouvertes.fr/hal-01392832/file/AlmerasClair2016_JRSInterface_Critical%20review%20on%20the%20mechanisms%20of%20maturation%20stress%20generation%20in%20trees_HAL.pdf
DOI : 10.1098/rsif.2016.0550

Éditeur(s) : HAL CCSD
Résumé : Inorganic arsenic is an environmental human carcinogen, but is also studied these days because of its potential effectiveness in curing chronic inflammatory disease. Indeed, this metalloid possesses immunosuppressive properties which can dysregulate physiological mechanisms involved in immune defense, or reduce inflammation associated with those inflammatory diseases. Inorganic arsenic is known mainly to alter functions of T cells and macrophages. However, it is unknown whether arsenic targets dendritic cells (DCs). Yet, this antigen presenting cells plays a major role in the immunosurveillance, and is involved in the physiopathology of chronic inflammatory diseases. So, the aim of my thesis work was to study the effects of inorganic arsenic on in vitro differenciation and maturation of dendritic cells from human monocytes. Our results mainly shows that concentrations corresponding to those measured in environmentally exposed people, inhibits DCs secretion of proinflammatory cytokines, which plays a major role in activation and polarization of T cells. Particularly, arsenic strongly impairs expression and secretion of interleukine 12 (IL-12) by an underlying molecular mechanism involving Nrf2. Finally, this work shows that inorganic arsenic has immunosuppressive properties on the physiology in vitro of human dendritic cells. Immunotoxicity may then contribute to the metalloid toxicity in environmentally exposed people. This element could be taken into account when determining arsenic effects in curing some chronic inflammatory diseases.
L’arsenic inorganique est un contaminant environnemental, cancérogène pour l’homme, mais également un métalloïde étudié, aujourd’hui, dans le traitement de maladies inflammatoires chroniques. Il possède des propriétés immunosuppressives pouvant déréguler les mécanismes physiologiques de défense ou bloquer l’exacerbation de réponses inflammatoires chroniques. L’arsenic inorganique altère principalement les fonctions des lymphocytes T et des macrophages. En revanche, l’impact du métalloïde sur la physiologie des cellules dendritiques (DCs) est peu connu. Pourtant, ces cellules présentatrices d’antigène jouent un rôle fondamental dans les processus d’immunosurveillance et sont très impliquées dans la physiopathologie des maladies inflammatoires chroniques. Dans ce contexte, les objectifs de mon travail de thèse étaient d’étudier les effets de l’arsenic inorganique sur la différenciation et la maturation in vitro de DCs générées à partir de monocytes humains. Nos résultats démontrent principalement que des concentrations de métalloïde, compatibles avec les taux plasmatiques d’arsenic mesurés chez les individus exposés, répriment la capacité des DCs à sécréter différentes cytokines pro-inflammatoires jouant un rôle essentiel dans l’activation et la polarisation des lymphocytes T. En particulier, l’arsenic inhibe l’expression et la sécrétion de l’interleukine-12 par un mécanisme moléculaire impliquant le facteur de transcription Nrf2. Au total, ces travaux de thèse démontrent que l’arsenic inorganique possède des propriétés immunosuppressives sur la physiologie in vitro des DCs humaines. Cette immunotoxicité pourrait contribuer à la toxicité du métalloïde chez l’homme exposé par voie environnementale, et être prise en compte pour déterminer les effets de l’arsenic dans le traitement de certaines maladies inflammatoires chroniques
https://tel.archives-ouvertes.fr/tel-01135887

NNT : 2013REN1B013
tel-01135887
https://tel.archives-ouvertes.fr/tel-01135887
https://tel.archives-ouvertes.fr/tel-01135887/document
https://tel.archives-ouvertes.fr/tel-01135887/file/pdf2star-1392896105-Th--se-M--linda-Macoch2.pdf

Éditeur(s) : HAL CCSD Oxford University Press (OUP): Policy B - Oxford Open Option B
Résumé : International audience
To recover verticality after disturbance, angiosperm trees produce " tension wood " allowing them to bend actively. The driving force of the tension has been shown to take place in the G-layer, a specific unlignified layer of the cell wall observed in most temperate species. However, in tropical rain forests, the G-layer is often absent and the mechanism generating the forces to reorient trees remains unclear. A study was carried out on tilted seedlings, saplings and adult Simarouba amara trees – a species known to not produce a G-layer. Microscopic observations were done on sections of normal and tension wood after staining or observed under UV light to assess the presence/absence of lignin. We showed that S. amara produces a cell-wall layer with all of the characteristics typical of G-layers, but that this G-layer can be observed only as a temporary stage of the cell-wall development because it is masked by a late lignification. Being thin and lignified, tension wood fibres cannot be distinguished from normal wood fibres in the mature wood of adult trees. These observations indicate that the mechanism generating the high tensile stress in tension wood is likely to be the same as that in species with a typical G-layer and also in species where the G-layer cannot be observed in mature cells.
ISSN: 0829-318X

hal-01229280
https://hal.archives-ouvertes.fr/hal-01229280
https://hal.archives-ouvertes.fr/hal-01229280/document
https://hal.archives-ouvertes.fr/hal-01229280/file/Roussel-Clair-2015-TreePhysiol-LateLignifGLayerSimarouba_preprintHAL.pdf
DOI : 10.1093/treephys/tpv082

Éditeur(s) : HAL CCSD
Résumé : International audience
The main biological function of reaction wood is to act as “muscle” for trees, enabling them to control their posture and right stems when they are permanently disturbed from their set-point inclination by gravity or winds. The key property to achieve this function is the development of high mechanical stress during the formation of reaction wood cells, called “maturation strains”. Moreover, this function is basically performed through the asymmetric formation of wood (in quantity or quality) around the tree circumference. This asymmetry enables stems to bend upward or to compensate for the downward bending induced by gravity, as an asymmetric force associated to maturation strains creates a bending moment (i.e. one side of the stem “pulls” the other one). We will discuss the traits (cross sectional size and shape, wood features as G fibers or microfibril angle, eccentric growth even in usual or extreme cases as buttresses, total biomass growth and height of center of mass, stem lean and set-point angle) involved to understand how the posture control works. We will give simple formulas to estimate a “muscle efficiency” from biomechanical modeling. We will give practical methods to estimate all the involved traits, especially maturation strains from direct and indirect measurements, in peripheral functional wood or by retrospective dendrochronological analysis. Then, we will illustrate how tree stem tropisms and especially gravitropism, widely studied by physiologists, are key processes in natural ecosystems, through practical examples from tropical rainforest tree communities and regeneration of European mixed beech forests. Using the previous definition of postural control efficiency, we will show that the cross section size is rapidly a limiting factor, opposing the extreme strategies of flexible small stems, which bend easily but also right themselves quickly, to stiff big stems. Lastly, as wood in living trees ensures general storage, defence, vascular and skeletal functions, we will ask general questions about synergies and trade-offs between posture control and other functions.
Botany 2014 : new frontiers in botany
Boise, United States

hal-01627031
https://hal.archives-ouvertes.fr/hal-01627031

Éditeur(s) : HAL CCSD Springer-Verlag Berlin Heidelberg
Résumé : International audience
Reaction wood produces very peculiar maturation stresses at the tree periphery i.e. compressive stress or very high tensile stress, for compression and tension wood respectively, as compared to moderately high tensile stress for normal wood. This means that both its mechanical state and its mechanical and physical properties differ from normal wood. Compression wood shows big differences from normal wood in conifers, for all physical and mechanical properties: higher density and axial crushing strength (MOR) but lower modulus of elasticity (MOE), far higher axial (longitudinal) shrinkage but lower radial and tangential shrinkage, sometimes even lower than the axial shrinkage. For tension wood things are less simple and can vary a lot from hardwood species to species. Globally there are no systematic differences in density and transverse shrinkage, MOE tends to be a little higher while MOR is slightly lower. However, axial shrinkage is much higher for tension wood with a gelatinous layer (G layer) than normal wood due to the specific gel like organization of cellulose microfibrils in the G layer. For tension wood without a G layer(which is rather frequent) axial shrinkage in the first drying operation is around two times higher than in normal wood mainly because of a kind of hygro-thermal release of locked in maturation stress. Overall the very high tensile stress and stored elastic energy in tension wood lead to problemsin wood processing (end splitting and board warping), which is far less the case for compression wood. But due to the large difference in properties relative to normal wood, compression wood occurrence is always a big problem for the in service behaviour of timber, which is seldom the case for tension wood.
The biology of reaction wood

ISBN : 978-3-642-10813-6
hal-01135273
https://hal.archives-ouvertes.fr/hal-01135273

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Studies on tree biomechanical design usually focus on stem stiffness, resistance to breakage or uprooting, and elastic stability. Here we consider another biomechanical constraint related to the interaction between growth and gravity. Because stems are slender structures and are never perfectly symmetric, the increase in tree mass always causes bending movements. Given the current mechanical design of trees, integration of these movements over time would ultimately lead to a weeping habit unless some gravitropic correction occurs. This correction is achieved by asymmetric internal forces induced during the maturation of new wood. The long-term stability of a growing stem therefore depends on how the gravitropic correction that is generated by diameter growth balances the disturbance due to increasing self weight. General mechanical formulations based on beam theory are proposed to model these phenomena. The rates of disturbance and correction associated with a growth increment are deduced and expressed as a function of elementary traits of stem morphology, cross-section anatomy and wood properties. Evaluation of these traits using previously published data shows that the balance between the correction and the disturbance strongly depends on the efficiency of the gravitropic correction, which depends on the asymmetry of wood maturation strain, eccentric growth, and gradients in wood stiffness. By combining disturbance and correction rates, the gravitropic performance indicates the dynamics of stem bending during growth. It depends on stem biomechanical traits and dimensions. By analyzing dimensional effects, we show that the necessity for gravitropic correction might constrain stem allometric growth in the long-term. This constraint is compared to the requirement for elastic stability, showing that gravitropic performance limits the increase in height of tilted stem and branches. The performance of this function may thus limit the slenderness and lean of stems, and therefore the ability of the tree to capture light in a heterogeneous environment.
ISSN: 0022-5193

hal-00534316
https://hal.archives-ouvertes.fr/hal-00534316
DOI : 10.1016/j.jtbi.2008.10.011

Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
The 2004 Aceh and 2005 Nias events are the two greatest earthquakes of the past 40 years with a total rupture of 1700 km long and a coseismic slip reaching up to 25 m. These two earthquakes have caused large stress perturbations which significantly altered seismic activity in the Sumatra-Andaman region. Using both detailed mapping of failure planes and various slip distributions, we calculate this stress change along the Sumatra-Andaman-Sagaing fault system from central Sumatra to southern Myanmar. The static Coulomb stress change Delta CFF and the observed seismic activity are in very good agreement with a Coulomb index similar to 20% greater than the one obtained for random events. Compared to previous studies, this high Coulomb Index confirms two important issues on the use of static stress change criterion: unsuited to study near-field aftershocks and only relevant for aftershocks analysis on large and mature faults at a time scale of several months. The calculated Delta CFF distribution suggests that the 2004 and 2005 earthquakes inhibit failure on the North Andaman rift and on the Sagaing fault, while failure is encouraged along the transform Andaman zone, the central Andaman rift, the West Andaman fault, the Sumatra fault system, and the offshore thrust faults west of Sumatra Island. The maximum value of similar to 15-20 bar (1.5-2 MPa) for Delta CFF is reached in the northern part of the Sumatra fault system. This high value together with the lack of major earthquake in the last 170 years result in a high seismic hazard for this region. Our results are also consistent with temporal evolution of both earthquakes' location and focal mechanism prior to and after the events. In particular, we explain the occurrence and the mechanism of seismic swarms observed in the central Andaman rift and along the west Andaman fault. Finally, our calculations reveal that the seismicity in the Andaman rift zone can only be explained if mu' > 0.5. This result leads to two end-member models: one with a constant and high fault friction and one with spatial variations, for which friction may depend on either the nature of the lithosphere (oceanic versus continental) or the fault type.
ISSN: 1525-2027

hal-00456027
https://hal.archives-ouvertes.fr/hal-00456027
DOI : 10.1029/2008GC002167

Éditeur(s) : Elsevier
Résumé : The consequences of handling stress (fishing, transfer, eyestalk ablation) on shrimp broodstock are poorly documented. The weakness of farmed shrimp, Litopenaeus stylirostris, during winter is a major problem in New Caledonia, because of seasonal climate (tropical-sub-temperate). The transfer of broodstock in winter from earthen outdoor ponds to indoor maturation tanks in the hatchery (T=20 degrees C, Salinity=35 parts per thousand, fed shrimp) usually leads, after 48 h, to high mortality (up to 70%). Eyestalk ablation to induce ovarian maturation in females leads to further mortality. Starting from a background analysis of physiological disturbances (initial osmoregulatory imbalance) associated with handling stress (Wabete, N., Chim, L., Lernaire, P., Massabuau, J.-C., 2004. Caracterisation de problemes de physiologie respiratoire et d'echanges ioniques associes A la manipulation chez la crevette peneide Litopenaeus stylirostris a 20 degrees C. Styli 2003. Trente ans de crevetticulture en Nouvelle-Caledonie. Ed. Ifremer. Actes Colloq. 38, 75-84.), we developed aprotocol using a soft technology, based on modifications of water salinity, temperature and feeding regime. The aim was to minimize problems of osmoregulatory imbalance and associated mortalities. The protocol we developed, called the LSD OT protocol (Low Salinity and Diet, Optimal Temperature), was first evaluated on sub-adult shrimp (20-25 g) and then applied to broodstock. Survival after transfer and following eyestalk ablation, as well as reproductive achievement (spawning rate, nauplii number) was considerably improved when shrimps were transferred under "physiological comfort" i.e. warmed isosmotic water (26 degrees C and 26 parts per thousand) and unfed for 3 d. This new handling protocol, based on a better control of salinity, temperature and feeding conditions, has been transferred successfully to private hatcheries and already contributes to an increased profitability of New-Caledonian shrimp industry. (c) 2006 Elsevier B.V. All rights reserved.
Aquaculture (0044-8486) (Elsevier), 2006-09 , Vol. 260 , N. 1-4 , P. 181-193

Droits : 2006 Elsevier
http://archimer.ifremer.fr/doc/2006/publication-1880.pdf
DOI:10.1016/j.aquaculture.2006.06.041
http://archimer.ifremer.fr/doc/00000/1880/

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Cnidarian-dinoflagellate symbiosis disruption and subsequent bleaching are major concerns, especially regarding their ecological consequences on coral reefs and temperate coralligenous communities. Cnidarian bleaching is caused by a variety of environmental stressors, such as elevated seawater temperature associated with global climate change, and by pollutants, such as herbicides and metals. Several cellular events have been described to explain symbiosis dysfunction and bleaching. Excess or damaged Symbiodinium symbionts are removed through a variety of mechanisms, including exocytosis, apoptosis, necrosis and autophagy. However, few studies have compared in the same species the relative involvement of these mechanisms, according to the stress inducing the bleaching. In this study, we used two different treatments —temperature and menthol— to induce bleaching in the sea anemone Anemonia viridis. By monitoring the ultrastructural tissue modifications, in control specimens we observed a basal rate of in situ symbiont digestion —or symbiophagy— induced by starvation. Symbiophagy was strongly induced in menthol-treated specimens and was the main cellular process of bleaching, whereas apoptosis and necrosis predominated in hyperthermal-induced bleaching. These results suggested a host effect through autophagy in menthol-treated specimens. These observations also suggested that symbiont removal may result from reengagement of the phagosomal maturation process in the host. These overall data demonstrate that several Symbiodinium cell removal mechanisms coexist and that stressors can activate one or more of these pathways, depending on the stress type, intensity or duration.
ISSN: 0334-5114

hal-01546908
http://hal.upmc.fr/hal-01546908
DOI : 10.1007/s13199-016-0406-y

Éditeur(s) : HAL CCSD Walter de Gruyter
Résumé : absent
Holzforschung

hal-01031939
https://hal.archives-ouvertes.fr/hal-01031939
DOI : 10.1515/HF.2005.057

Éditeur(s) : HAL CCSD
Résumé : The spectrin-based skeleton is an essential scaffold underlying different lipid bilayers in all animal cells. Spectrins (Sp), as giant extended flexible heterotetramers (αβ)2, constitute the filaments of this network, the nodes of which are cross-linked by actin filaments. The functions of the Sp-based skeleton, which are well defined in red blood cells (required for shape, resistance to shear stress and deformability) are less well understood in non-erythroid cells.The non-erythroid Sp might participate in the establishment and/or the maintenance of specialized membrane subdomains by accumulating integral membrane proteins (such as ionic channels, ionic pumps, receptors and cell adhesion molecules) as revealed by loss of the main non-erythroid β-Sp. However the effect of non-erythroid α-Sp are less well established. In mammals, α-Sp are encoded by two genes: one for αI-Sp mainly expressed in mature erythrocyte, the second one for αII-Sp which is expressed in all nucleated cells.In the pursuit of αII-Sp functions, we have checked the effect of αII-Sp knock down by siRNA melanoma human cell line. Our data revealed that spectrin depletion is associated with i) an arrest of cell cycle at G1 state ii) a loss of cell adhesion in spite of increase in some integrins iii) some modifications of actin organisation.
Le squelette dépendant de la spectrine, localisé sous la bicouche lipidique, est un échafaudage essentiel de toutes les cellules animales. La Spectrine (Sp), structure géante, robuste mais flexible d'hétéro tétramères (αβ)2, constitue les filaments de ce réseau, dont chaque nœud interagit avec des filaments d'actine. Les fonctions du squelette de Sp, qui sont bien définies dans le globule rouge (rôle dans sa forme, dans sa résistance aux forces de cisaillement et dans sa déformabilité) sont moins bien connues dans les cellules non-érythroïdes. La Sp non-érythroïde pourrait participer à l'établissement et/ou au maintien de sous-domaines membranaires spécialisés dans l'accumulation de protéines de membrane (telles que les canaux ioniques, les pompes ioniques, les récepteurs et les molécules d'adhérence) comme nous le font penser les invalidations de la Sp-β non-érythroïde. Cependant le rôle de la Sp-α non-érythroïde est moins bien établi. Chez les mammifères, la Sp-α est codée par deux gènes: un pour Sp-αI, principalement exprimée dans l'érythrocyte mature, le second pour Sp-αII qui est exprimée dans toutes les cellules nucléées. Pour étudier les fonctions de la Sp-αII, nous avons utilisé une approche de SiRNA sur des cellules de mélanome humain. Nos données montrent que la diminution de Sp-αII est associée à I) un arrêt en G1 du cycle cellulaire II) une perte d'adhérence des cellules malgré l'augmentation de quelques intégrines III) des modifications dans l'organisation du réseau d'actine.
https://tel.archives-ouvertes.fr/tel-00377569

Droits : info:eu-repo/semantics/OpenAccess
tel-00377569
https://tel.archives-ouvertes.fr/tel-00377569
https://tel.archives-ouvertes.fr/tel-00377569/document
https://tel.archives-ouvertes.fr/tel-00377569/file/these_210409_entiere.pdf
https://tel.archives-ouvertes.fr/tel-00377569/file/II-Spectrin_Is_Critical_for_Cell_Adhesion_and_Cell_Cycle.PDF

Éditeur(s) : HAL CCSD
COST E50 Workshop: Reaction wood formation at stand, tree and cellular level

hal-00797326
https://hal.archives-ouvertes.fr/hal-00797326

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : International audience
This observation perfectly illustrates the main epidemiological, clinical and biological peculiarities of this parasitic disease. Particularly, as it concerns a tourist who travelled across Africa for a short period of time it is possible to assess the time of exposure to infecting mosquito bites, the maturation period of time as well as the time of clinical incubation. On the other hand the value of the immunological techniques to make the diagnosis of loaiasis as well as the difficulties to treat this affection are stressed upon.
ISSN: 0181-5512

hal-00715439
https://hal.univ-antilles.fr/hal-00715439
PUBMED : 6939746