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Literatura académica sobre el tema "Coraux – Physiologie"

Autor: Grafiati

Publicado: 25 de mayo de 2024

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Artículos de revistas sobre el tema "Coraux – Physiologie"

Mayfield, Anderson B. y Alexandra C. Dempsey. "Environmentally-Driven Variation in the Physiology of a New Caledonian Reef Coral". Oceans 3, n.º 1 (6 de enero de 2022): 15–29. http://dx.doi.org/10.3390/oceans3010002.

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Given the widespread threats to coral reefs, scientists have lost the opportunity to understand the basic biology of “pristine” corals whose physiologies have not been markedly perturbed by human activity. For instance, high temperature-induced bleaching has been occurring annually since 2014 in New Caledonia. Because most corals cannot withstand repeated years when bleaching occurs, an analysis was undertaken to showcase coral behavior in a period just before the onset of “annual severe bleaching” (ASB; November 2013) such that future generations might know how these corals functioned in their last bleaching-free year. Pocillopora damicornis colonies were sampled across a variety of environmental gradients, and a subset was sampled during both day and night to understand how their molecular biology changes upon cessation of dinoflagellate photosynthesis. Of the 13 environmental parameters tested, sampling time (i.e., light) most significantly affected coral molecular physiology, and expression levels of a number of both host and Symbiodiniaceae genes demonstrated significant diel variation; endosymbiont mRNA expression was more temporally variable than that of their anthozoan hosts. Furthermore, expression of all stress-targeted genes in both eukaryotic compartments of the holobiont was high, even in isolated, uninhabited, federally protected atolls of the country’s far northwest. Whether this degree of sub-cellular stress reflects cumulative climate change impacts or, instead, a stress-hardened phenotype, will be unveiled through assessing the fates of these corals in the wake of increasingly frequent marine heatwaves.

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Blanckaert, Alice C. A., Tom Biscéré, Renaud Grover y Christine Ferrier-Pagès. "Species-Specific Response of Corals to Imbalanced Ratios of Inorganic Nutrients". International Journal of Molecular Sciences 24, n.º 4 (4 de febrero de 2023): 3119. http://dx.doi.org/10.3390/ijms24043119.

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Dissolved inorganic phosphorus (DIP) is a limiting nutrient in the physiology of scleractinian corals. Anthropogenic addition of dissolved inorganic nitrogen (DIN) to coastal reefs increases the seawater DIN:DIP ratio and further increases P limitation, which is detrimental to coral health. The effects of imbalanced DIN:DIP ratios on coral physiology require further investigation in coral species other than the most studied branching corals. Here we investigated the nutrient uptake rates, elemental tissue composition and physiology of a foliose stony coral, Turbinaria reniformis, and a soft coral, Sarcophyton glaucum, exposed to four different DIN: DIP ratios (0.5:0.2, 0.5:1, 3:0.2, 3:1). The results show that T. reniformis had high uptake rates of DIN and DIP, proportional to the seawater nutrient concentrations. DIN enrichment alone led to an increase in tissue N content, shifting the tissue N:P ratio towards P limitation. However, S. glaucum had 5 times lower uptake rates and only took up DIN when the seawater was simultaneously enriched with DIP. This double uptake of N and P did not alter tissue stoichiometry. This study allows us to better understand the susceptibility of corals to changes in the DIN:DIP ratio and predict how coral species will respond under eutrophic conditions in the reef.

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Huffmyer, Ariana S., Colton J. Johnson, Ashleigh M. Epps, Judith D. Lemus y Ruth D. Gates. "Feeding and thermal conditioning enhance coral temperature tolerance in juvenile Pocillopora acuta". Royal Society Open Science 8, n.º 5 (mayo de 2021): 210644. http://dx.doi.org/10.1098/rsos.210644.

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Scleractinian corals form the foundation of coral reefs by acquiring autotrophic nutrition from photosynthetic endosymbionts (Symbiodiniaceae) and use feeding to obtain additional nutrition, especially when the symbiosis is compromised (i.e. bleaching). Juvenile corals are vulnerable to stress due to low energetic reserves and high demand for growth, which is compounded when additional stressors occur. Therefore, conditions that favour energy acquisition and storage may enhance survival under stressful conditions. To investigate the influence of feeding on thermal tolerance, we exposed Pocillopora acuta juveniles to temperature (ambient, 27.4°C versus cool, 25.9°C) and feeding treatments (fed versus unfed) for 30 days post-settlement and monitored growth and physiology, followed by tracking survival under thermal stress. Feeding increased growth and resulted in thicker tissues and elevated symbiont fluorescence. Under high-temperature stress (31–60 days post-settlement; ca 30.1°C), corals that were fed and previously exposed to cool temperature had 33% higher survival than other treatment groups. These corals demonstrated reduced symbiont fluorescence, which may have provided protective effects under thermal stress. These results highlight that the impacts of feeding on coral physiology and stress tolerance are dependent on temperature and as oceans continue to warm, early life stages may experience shifts in feeding strategies to survive.

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D'angelo, Cecilia y Jörg Wiedenmann. "An experimental mesocosm for long-term studies of reef corals". Journal of the Marine Biological Association of the United Kingdom 92, n.º 4 (9 de diciembre de 2011): 769–75. http://dx.doi.org/10.1017/s0025315411001883.

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Molecular biological methods including genomic and proteomic approaches hold a specific promise to provide new insights into the stress physiology of corals. However, to fully exploit the power of these techniques, aquarium setups are required that allow biological assays under tightly controlled laboratory conditions. Here, details are provided about the successful development of a closed coral mesocosm at the National Oceanography Centre, Southampton. The system can be operated without access to natural seawater and allows long-term observations and experimental studies of reef corals. The individual experimental tanks allow the corals to be exposed, for example, to different light and/or temperature conditions without the need to disconnect them from the system.

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Shahani, Kamran, Hong Song, Syed Raza Mehdi, Awakash Sharma, Ghulam Tunio, Junaidullah Qureshi, Noor Kalhoro y Nooruddin Khaskheli. "Design and Testing of an Underwater Microscope with Variable Objective Lens for the Study of Benthic Communities". Journal of Marine Science and Application 20, n.º 1 (marzo de 2021): 170–78. http://dx.doi.org/10.1007/s11804-020-00185-9.

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AbstractMonitoring the ecology and physiology of corals, sediments, planktons, and microplastic at a suitable spatial resolution is of great importance in oceanic scientific research. To meet this requirement, an underwater microscope with an electrically controlled variable lens was designed and tested. The captured microscopic images of corals, sediments, planktons, and microplastic revealed their physical, biological, and morphological characteristics. Further studies of the images also revealed the growth, degradation, and bleaching patterns of corals; the presence of plankton communities; and the types of microplastics. The imaging performance is majorly influenced by the choice of lenses, camera selection, and lighting method. Image dehazing, global saturation masks, and image histograms were used to extract the image features. Fundamental experimental proof was obtained with micro-scale images of corals, sediments, planktons, and microplastic at different magnifications. The designed underwater microscope can provide relevant new insights into the observation and detection of the future conditions of aquatic ecosystems.

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Bhagooli, Ranjeet, Mouneshwar Soondur, Sundy Ramah, Arvind Gopeechund, Sruti Jeetun y Deepeeka Kaullysing. "Photo-physiology of healthy and bleached corals from the Mascarene Plateau". Western Indian Ocean Journal of Marine Science, n.º 2/2021 (20 de julio de 2022): 109–20. http://dx.doi.org/10.4314/wiojms.si2021.2.8.

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This study presents the first report of variable photo-physiology of healthy-looking and bleached corals from the upper mesophotic waters of the Mascarene Plateau. In May 2018, during the FAO EAF-Nansen research expedition cruise, coral bleaching was visually observed. Five coral species from Saya de Malha Bank, namely Heliopora coerulea, Favites sp. and Porites sp. from 27 m and Acropora sp. and Lithophyllon repanda from 30 m, and three coral species from the Nazareth Bank, namely Acropora sp. and Galaxea fascicularis from 36 m and Stylophora-like species from 58 m were studied using the Video-Assisted Multi-Sampler (VAMS) and collected using a Van Veen grab. Chlorophyll a fluorescence parameters such as effective quantum yield at photosystem II (ΦPSII), relative maximum electron transport rate (rETRm), photosynthetic efficiency (α), photoinhibition (β), saturating light level (Ek), and maximum non-photochemical quenching (NPQm) were measured using a Diving-Pulse-Amplitude-Modulated (D-PAM) fluorometer to study variable photo-physiology in bleached and non-bleached corals. All photo-physiological parameters varied significantly among coral species tested and between coral conditions, except for β. The interaction between species and coral conditions was only significant in the case of β, but generally not significant. A two-way ANOVA indicated significant effects of depth and coral conditions in Acropora sp. on almost all photo-physiological parameters, except for β, and the effect of depth on rETRmax and α, and the effect of depth along with its interaction with coral conditions on Ek. ΦPSII did not differ in bleached and healthy-looking coral parts of Porites and Lithophyllon from 27 m, Galaxea and Acropora from 36 m while it decreased significantly in Heliopora and Favites at 27 m, Acropora from 30 m, and Stylophora-like at 58 m. NPQm did not change for Porites, Acropora (30 m) and Galaxea but it tended to increase for Heliopora, Acropora (36 m), Lithophyllon, Galaxea, and decrease for Favities, Acropora (30 m) and Stylophora-like. The thermally tolerant coral Porites exhibited normal photo-physiology even in bleached conditions while the bleached parts of Favites, Acropora (30 m) and Stylophora-like corals exhibited photo-physiological dysfunctioning. This study revealed that the seven studied corals from the upper mesophotic waters of the Mascarene Plateau are not spared from the bleaching phenomenon and exhibit variable photo-physiology in bleached and non-bleached conditions. Further studies are warranted to thoroughly understand the coral bleaching patterns and severity during summer periods at the Saya de Malha and Nazareth Banks.

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Rodolfo-Metalpa, R., S. Martin, C. Ferrier-Pagès y J. P. Gattuso. "Response of the temperate coral Cladocora caespitosa to mid- and long-term exposure to pCO2 and temperature levels projected in 2100". Biogeosciences Discussions 6, n.º 4 (16 de julio de 2009): 7103–31. http://dx.doi.org/10.5194/bgd-6-7103-2009.

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Abstract. Atmospheric CO2 partial pressure (pCO2) is expected to increase to 700 ppm or more by the end of the present century. Anthropogenic CO2 is absorbed by the oceans leading to decreases in pH and the CaCO3 saturation state (Ω) of the seawater. While pCO2 was shown to drastically decrease calcification rates in tropical, fast growing corals, here we show, using the Mediterranean symbiotic coral Cladocora caespitosa, that the conventional belief that an increase in pCO2, in the range predicted to 2100, reduces calcification rates may not be widespread in temperate corals. We found that the seasonal change in temperature was the predominant factor controlling the physiology and growth of C. caespitosa, while an increase in pCO2, alone or in combination with global warming, had no significant effect on photosynthesis, photosynthetic efficiency and calcification. This result differs from that obtained on reef-building corals, which exhibit lower rates of calcification at elevated pCO2. The lack of sensitivity of temperate corals to high-pCO2 levels might be due to its slow growth rates, which seem to be more dependent on temperature than on the saturation state of calcium carbonate in the range predicted for the end of the century.

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Gardner, Stephanie G., Daniel A. Nielsen, Olivier Laczka, Ronald Shimmon, Victor H. Beltran, Peter J. Ralph y Katherina Petrou. "Dimethylsulfoniopropionate, superoxide dismutase and glutathione as stress response indicators in three corals under short-term hyposalinity stress". Proceedings of the Royal Society B: Biological Sciences 283, n.º 1824 (10 de febrero de 2016): 20152418. http://dx.doi.org/10.1098/rspb.2015.2418.

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Corals are among the most active producers of dimethylsulfoniopropionate (DMSP), a key molecule in marine sulfur cycling, yet the specific physiological role of DMSP in corals remains elusive. Here, we examine the oxidative stress response of three coral species ( Acropora millepora , Stylophora pistillata and Pocillopora damicornis ) and explore the antioxidant role of DMSP and its breakdown products under short-term hyposalinity stress. Symbiont photosynthetic activity declined with hyposalinity exposure in all three reef-building corals. This corresponded with the upregulation of superoxide dismutase and glutathione in the animal host of all three species. For the symbiont component, there were differences in antioxidant regulation, demonstrating differential responses to oxidative stress between the Symbiodinium subclades. Of the three coral species investigated, only A. millepora provided any evidence of the role of DMSP in the oxidative stress response. Our study reveals variability in antioxidant regulation in corals and highlights the influence life-history traits, and the subcladal differences can have on coral physiology. Our data expand on the emerging understanding of the role of DMSP in coral stress regulation and emphasizes the importance of exploring both the host and symbiont responses for defining the threshold of the coral holobiont to hyposalinity stress.

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Camp, Emma F., David J. Smith, Chris Evenhuis, Ian Enochs, Derek Manzello, Stephen Woodcock y David J. Suggett. "Acclimatization to high-variance habitats does not enhance physiological tolerance of two key Caribbean corals to future temperature and pH". Proceedings of the Royal Society B: Biological Sciences 283, n.º 1831 (25 de mayo de 2016): 20160442. http://dx.doi.org/10.1098/rspb.2016.0442.

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Corals are acclimatized to populate dynamic habitats that neighbour coral reefs. Habitats such as seagrass beds exhibit broad diel changes in temperature and pH that routinely expose corals to conditions predicted for reefs over the next 50–100 years. However, whether such acclimatization effectively enhances physiological tolerance to, and hence provides refuge against, future climate scenarios remains unknown. Also, whether corals living in low-variance habitats can tolerate present-day high-variance conditions remains untested. We experimentally examined how pH and temperature predicted for the year 2100 affects the growth and physiology of two dominant Caribbean corals ( Acropora palmata and Porites astreoides ) native to habitats with intrinsically low (outer-reef terrace, LV) and/or high (neighbouring seagrass, HV) environmental variance. Under present-day temperature and pH, growth and metabolic rates (calcification, respiration and photosynthesis) were unchanged for HV versus LV populations. Superimposing future climate scenarios onto the HV and LV conditions did not result in any enhanced tolerance to colonies native to HV. Calcification rates were always lower for elevated temperature and/or reduced pH. Together, these results suggest that seagrass habitats may not serve as refugia against climate change if the magnitude of future temperature and pH changes is equivalent to neighbouring reef habitats.

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Gori, Andrea, Christine Ferrier-Pagès, Sebastian J. Hennige, Fiona Murray, Cécile Rottier, Laura C. Wicks y J. Murray Roberts. "Physiological response of the cold-water coralDesmophyllum dianthusto thermal stress and ocean acidification". PeerJ 4 (2 de febrero de 2016): e1606. http://dx.doi.org/10.7717/peerj.1606.

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Rising temperatures and ocean acidification driven by anthropogenic carbon emissions threaten both tropical and temperate corals. However, the synergistic effect of these stressors on coral physiology is still poorly understood, in particular for cold-water corals. This study assessed changes in key physiological parameters (calcification, respiration and ammonium excretion) of the widespread cold-water coralDesmophyllum dianthusmaintained for ∼8 months at two temperatures (ambient 12 °C and elevated 15 °C) and two pCO2conditions (ambient 390 ppm and elevated 750 ppm). At ambient temperatures no change in instantaneous calcification, respiration or ammonium excretion rates was observed at either pCO2levels. Conversely, elevated temperature (15 °C) significantly reduced calcification rates, and combined elevated temperature and pCO2significantly reduced respiration rates. Changes in the ratio of respired oxygen to excreted nitrogen (O:N), which provides information on the main sources of energy being metabolized, indicated a shift from mixed use of protein and carbohydrate/lipid as metabolic substrates under control conditions, to less efficient protein-dominated catabolism under both stressors. Overall, this study shows that the physiology ofD. dianthusis more sensitive to thermal than pCO2stress, and that the predicted combination of rising temperatures and ocean acidification in the coming decades may severely impact this cold-water coral species.

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Tesis sobre el tema "Coraux – Physiologie"

Bernardet, Coralie. "Physiologie des transports ioniques et moléculaires chez les coraux, implications environnementales". Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS496.pdf.

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Les coraux tropicaux constructeurs de récifs sont à l’origine d’écosystèmes extrêmement riches dont dépendent de nombreuses espèces, y compris l’Homme. Aujourd’hui, les changements climatiques représentent toutefois une menace pour la survie des coraux. Afin de comprendre la réponse de ces espèces aux modifications environnementales, il est essentiel d’avoir des informations sur la physiologie de ces espèces-clé. Les travaux conduits au cours de ma thèse ont ainsi permis de caractériser, au niveau mécanistique, les processus affectés par des changements de température chez l’espèce Stylophora pistillata. Pour cela, j’ai employé des approches multiples en partant de l’animal jusqu’au gène. Mes résultats ont montré : 1) que les taux de calcification, de photosynthèse et de respiration sont drastiquement réduits aux extrémités de la fenêtre thermique, 2) l’existence d’un phénomène de « light-enhanced calcification », excepté à basse température, 3) la sous-expression d’un groupe de gènes impliqué dans le transport du carbone inorganique lorsque les taux de calcification sont réduits (stress thermiques et la nuit), 4) la stabilité du pH dans le milieu extracellulaire calcifiant dans tous les traitements, et 5) l’augmentation de la perméabilité paracellulaire conjointement à l’augmentation de la calcification (25°C et le jour). En plus de leur intérêt en recherche fondamentale, ces informations peuvent constituer des outils utiles pour de futures recherches sur le terrain dans le but d’évaluer l’état de santé des coraux et prédire leur devenir dans un monde qui change
Tropical reef-building corals are at the basis of extremely biodiverse ecosystems on which many species depend, including human beings. Today, climate change represents a threat for the future survival of corals, and it is becoming crucial to better understand the physiology of these key species and the mechanisms underlying their responses to environmental change. The work conducted during my PhD focused on the characterization of the processes affected by temperature changes in Stylophora pistillata. For this purpose, I used multiple approaches from the animal to the gene. My results showed that: 1) calcification, photosynthesis and respiration declined drastically at the extremes of the thermal performance window, 2) light-enhanced calcification occurs across the thermal performance window except at low temperature, 3) a group of genes involved in inorganic carbon transport is under-expressed when calcification is reduced (thermal stress and during night), 4) pH in the extracellular calcifying medium remains stable at low and high temperatures, 5) paracellular permeability is highest when calcification increases (25°C and during the day). Information gained from this lab-based study will be useful in guiding further research in the field in order to evaluate coral health and predict the future of coral reefs in a changing world

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Blanckaert, Alice. "Effets de la disponibilité en macro- et micro-nutriments sur la physiologie des coraux tropicaux". Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS010.

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Les coraux tropicaux se sont adaptés à vivre dans des eaux pauvres en nutriments en établissant une relation symbiotique avec des dinoflagellés photosynthétiques (Symbiodiniaceae). En effet, les dinoflagellés utilisent les macronutriments (azote et phosphore inorganiques dissous, DIN et DIP) et métaux-traces de l’eau pour former des molécules organiques essentielles à la croissance du corail hôte. Cependant, pour une croissance et un fonctionnement optimal, l’association corail-dinoflagellé nécessite une qualité et des concentrations optimales de ces nutriments. Ce n’est pas le cas dans les récifs exposés à des perturbations anthropiques ou à des conditions environnementales particulières (upwellings par exemple). Dans ces récifs, où les concentrations en nutriments peuvent être particulièrement faibles ou élevées ou avec des rapports DIN:DIP déséquilibrés, il peut y avoir une rupture de la symbiose. L'objectif principal de cette thèse est d'étudier les effets de la disponibilité des nutriments et des changements dans le rapports DIN:DIP de l’eau de mer sur la physiologie des coraux. Cette thèse fournit de nouvelles informations sur la réponse de différentes espèces de coraux à des rapports DIN:DIP équilibrés et déséquilibrés. Globalement, les coraux restent en bonne santé tant qu’ils sont exposés à un rapport DIN:DIP équilibré dans l'eau de mer, même à des concentrations élevées de DIN et de DIP. Cependant, les résultats montrent une réponse complexe des coraux à des rapports DIN :DIP déséquilibrés, en fonction des facteurs environnementaux et des espèces étudiées. En effet, les octocoralliaires et les coraux scléractiniaires réagissent différemment à un rapport DIN:DIP déséquilibré. Les octocoralliaires ont des taux d'absorption de DIN et de DIP très faibles qui sont insuffisants pour modifier leur composition tissulaire en C:N:P et altérer la physiologie du corail. En revanche, chez les coraux scléractiniaires, les taux élevés d'absorption de DIN et de DIP induisent rapidement un apport important de nutriments dans le tissu corallien. Lorsque l'apport d'azote n'est pas équilibré par un apport proportionnel de phosphore, des modifications de la composition élémentaire et de la stœchiométrie des tissus sont observées, ce qui entraîne une dégradation de la physiologie du corail. De plus, les résultats montrent que l'azote a un impact différent sur les coraux selon sa forme, ammonium ou nitrate. L'ammonium favorise l'absorption du phosphore via l'hydrolyse du phosphore organique dissous (DOP) par les phosphatases, alors que le contraire est observé pour le nitrate. Enfin, les résultats indiquent également que les coraux peuvent être limités en métaux-traces, notamment en fer, ce qui peut réduire leur résilience au stress thermique. Cette thèse fournit des informations essentielles pour une meilleure gestion des récifs à l'ère du changement climatique. Les résultats obtenus montrent qu'il est important de maintenir un rapport DIN:DIP équilibré dans l'eau de mer pour assurer la bonne santé des coraux et soulignent l'importance de la disponibilité de métaux notamment le fer pour la résistance et la résilience des coraux au stress thermique
Tropical corals have adapted to life in nutrient-poor waters by establishing a symbiotic relationship with photosynthetic dinoflagellates (Symbiodiniaceae). Indeed, dinoflagellates use macronutrients (dissolved inorganic nitrogen and phosphorus, DIN and DIP) and trace metals from the seawater to form organic molecules essential for coral growth. However, for optimal growth and function, the coral-dinoflagellates association requires optimal quality and concentrations of these nutrients. This is not the case in reefs exposed to anthropogenic disturbances or specific environmental conditions (e.g. upwellings). In these reefs, particularly low or high nutrient concentrations or imbalanced DIN:DIP ratios may disrupt the symbiosis. The main objective of this thesis is to investigate the effects of nutrient availability and changes in seawater DIN:DIP ratios on coral physiology. In particular, this thesis provides new insights into the response of different coral species to balanced and imbalanced DIN:DIP ratios. Overall, corals remain healthy as long as they are exposed to a balanced DIN:DIP ratio in seawater, even at high DIN and DIP concentrations. In contrast, the results show a complex response to imbalanced DIN:DIP ratios that depends on environmental factors and coral species. Octocorals have very low uptake rates of DIN and DIP, which are not sufficient to alter their tissue composition and stoichiometry (C:N:P) and impair coral physiology. In contrast, in scleractinian corals, a high uptake rates of DIN and DIP rapidly induce a large supply of nutrients into the coral tissue. If nitrogen input is not balanced by a proportional input of phosphorus, changes in cellular elemental composition and stoichiometry are observed, leading to an impairment of coral physiology. In addition, nitrogen identity (ammonium or nitrate) impacts corals differently. Ammonium promotes phosphorus uptake via hydrolysis of dissolved organic phosphorus (DOP) by phosphatases, while the opposite is observed with nitrate. Finally, the results also suggest that corals may be limited in trace metals, particularly iron, which may reduce coral resilience to thermal stress. This thesis provides important information for better management of reefs in the era of climate change. The results show that maintaining a balanced DIN:DIP ratio in seawater is essential for coral health and highlight the importance of metal availability, particularly iron, for coral resistance and resilience to thermal stress

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Rollion-Bard, Claire. "Variabilité des isotopes de l'oxygène dans les coraux Porites : développement et implications des microanalyses d'isotopes stables (B, C ET O) par sonde ionique". Nancy 1, 2001. http://docnum.univ-lorraine.fr/public/INPL_T_2001_ROLLION-BARD_C.pdf.

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Des mesures des compositions isotopiques de bore, de carbone et d'oxygène par sonde ionique ont été développées sur des carbonates avec des reproductibilités internes de l'ordre 0,2 ‰ et des reproductibilités externes de l'ordre de 0,9 ‰ pour le bore, 0,65 ‰ pour le carbone et 0,4 ‰ pour l'oxygène. Les volumes analysés sont compris entre 3,5. 10-7 et 58,9. 1 0-7 mm³. Les coraux fournissent un enregistrement des conditions chimiques et physiques de l'eau de mer environnante au moment de la précipitation de leur squelette carbonaté. Leurs δ¹³C et δ¹⁸0 apparaissent en déséquilibre par rapport aux fractionnements isotopiques entre l'aragonite inorganique et l'eau. Cet écart est appelé effet "vital". Les mécanismes actuellement proposés pour expliquer cet effet "vital" sont, pour l'oxygène, une variation de pH dans le fluide de calcification (Adkins, 2000) ou un effet cinétique lors de la précipitation de l'aragonite du squelette (McConnaughey, 1989), et pour le carbone, un effet cinétique ou une forte contribution de C02 métabolique venant de la respiration du corail qui est appauvri en ¹³C. Les résultats pour les compositions isotopiques de bore, carbone et d'oxygène à l'échelle micrométrique ont plusieurs implications. Le déséquilibre des mesures de 8¹³C reflète sans doute le mélange des deux sources dont provient le CID (Carbone Inorganique Dissous) : le C02 métabolique issu de la respiration du corail et le CID venant directement de l'eau de mer. Les variations du δ¹⁸O à échelle micrométrique sont le résultat de plusieurs processus : (1) des variations de pH de l'ordre de 1 unité montrées par les données de δ¹¹ß; (2) un processus qui fractionnerait les isotopes de l'oxygène et qui s'exprimerait plus à pH basique qu'à pH acide ; (3) des changements biologiques liés à la mise en place des dissépiments ; (4) des hétérogénéités des δ¹⁸O au niveau des différentes parties du squelette avec notamment les synapticules avec un δ¹⁸O plus appauvri que les trabécules.

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Moulin, Laure. "Impact de l'acidification des océans sur l'oursin Echinometra mathaei et son activité bioérosive des récifs coralliens: étude en mésocosmes artificiels". Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209248.

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Depuis le début de la période industrielle, les activités humaines ont généré une augmentation importante de la concentration atmosphérique en CO2. Une partie de ce CO2 s’accumule dans l’atmosphère, entraînant une augmentation de l’effet de serre naturel et de la température à la surface du globe. Ce processus est plus connu sous le terme réchauffement climatique ou global. De plus, environ 25 % du CO2 produit sont absorbés par les océans. La dissolution du CO2 dans l’eau de mer, entraîne une augmentation de la concentration en protons et en ions bicarbonates (HCO3-) et une diminution de la concentration en ions carbonates (CO32-). Il en résulte une diminution du pH et du taux de saturation de l’eau de mer vis-à-vis du carbonate de calcium. L’ensemble de ces processus est appelé acidification des océans (AO). Le pH des eaux de surface océaniques a déjà diminué de 0,1 unité depuis le début de l’ère industrielle. Ce phénomène devrait s’intensifier au cours du siècle. Selon les prévisions moyennes d’émissions futures de gaz à effet de serre de l’IPCC, la température moyenne des eaux de surface devrait augmenter de 2 à 4 °C et son pH devrait diminuer de 0,3 à 0,4 unité d’ici 2100.

Au cours des deux dernières décennies, de nombreuses études ont mis en évidence l’impact négatif de l’AO sur les organismes marins. Les premières études ont été menées principalement en milieu artificiel et ont mis en évidence des conséquences majeures sur la physiologie des organismes, principalement au niveau individuel. Cependant, les dernières études menées dans le domaine ont souligné l'importance de mettre en place des expériences à long terme, à l'échelle de l'écosystème, et dans des conditions plus proches du milieu naturel. Ce type d’étude permet de prendre en compte les interactions écosystémiques et les processus d’acclimatation afin de mieux prévoir les effets directs mais aussi indirects de la diminution du pH dans les océans.

L’existence des récifs coralliens tropicaux dépend de la vitesse de formation du socle récifal qui les façonnent (principalement via la calcification des coraux hermatypiques) qui doit rester supérieure à sa (bio)érosion. D’une part, plusieurs études ont montré que le taux de calcification des coraux hermatypiques diminue lorsque la pCO2 augmente. D’autre part, les oursins sont d’importants bioérodeurs des récifs et contribuent donc à la perte de masse calcaire récifale. Cependant, les oursins empêchent également, par leur broutage, le recouvrement des coraux par les algues favorisées par l’AO. Dès lors l’effet de l’élévation de la pCO2 sur les oursins et leur capacité bioérosive peut être déterminant pour l'avenir des récifs coralliens tropicaux au cours du siècle, particulièrement ceux où la densité de ces bioérodeurs est importante. Une telle prédiction est d’autant plus complexe si l’on prend en compte la possible acclimatation des différents acteurs à long terme.

Dès lors, le but du présent travail fut d'évaluer l'effet à long terme de l’élévation de la pCO2 prévue en 2100 sur la physiologie et l’activité érosive d’un oursin clé de certains récifs coralliens, Echinometra mathaei, dans un dispositif artificiel reproduisant l’écosystème corallien.

La première étape a été la mise en place un outil expérimental permettant de maintenir à long terme un écosystème de récifs coralliens simplifié en condition contrôle et au pH prévu en 2100 tout en maintenant les autres paramètres physico-chimiques identiques et proches du milieu naturel (y compris dans leurs variations journalières). Le système mis en place est composé de scléractiniaires hermatypiques comme constructeurs de récif, d’oursins (E. mathaei) comme bioérodeurs et brouteurs et un substrat calcaire de récif avec ses communautés d’algues, bactéries, archae, champignons et méiofaune. Les variations journalières de pH et de température reproduisent celles mesurées in situ dans le site de La Saline, Ile de La Réunion, d’où proviennent une partie des organismes. Le pH moyen des aquariums contrôles a été maintenu avec succès à une moyenne de 8,09 ± 0,04, celui des aquariums à pCO2 élevée à 7,63 ± 0,02. L’alcalinité totale du système a pu être maintenue entre 2350 et 2450 µmol.kg-1.

L’impact de l’AO prévue en 2100 (pH 7,7) sur la physiologie d’E. mathaei été étudié à court terme (sept semaines). La principale source de nourriture des oursins fut la communauté algale se développant sur le substrat, comme en conditions naturelles. Cette étude a permis de mettre en évidence, à court terme, la capacité de résistance de cet oursin à une AO modérée. En effet, la croissance et le métabolisme ne furent pas affectés significativement. Ces observations ont été associées au maintien de la balance acide-base du fluide extracellulaire, le liquide cœlomique, par accumulation de bicarbonates dans celui-ci.

Une même expérience a ensuite été réalisée à long terme. La diminution du pH a été induite progressivement durant six mois jusqu'à atteindre un pH moyen de 7,65 qui fut ensuite maintenu à cette valeur pendant sept mois supplémentaires. La capacité de régulation de la balance acide-base du liquide cœlomique et la résistance d’E. mathaei à l’AO a été confirmée à long terme. Tant la croissance que le métabolisme et les propriétés mécaniques du squelette ne furent pas affectés. Cette résistance apparaît liée aux capacités de régulation acide-base d’E. mathaei, un trait apparemment d’origine génétique. Cette résistance pourrait également dépendre de la quantité et de la qualité de la nourriture disponible (calcaire ou non). Il est suggéré que les ions bicarbonates impliqués dans la régulation acide-base proviendraient en partie de la nourriture.

Parallèlement à ces mesures physiologiques, l’activité érosive d’E. mathaei a été mesurée. Les résultats indiquent que le taux de bioérosion triple en conditions acidifiées (pH 7,65). Cette augmentation serait liée à l’augmentation de l'activité de broutage des oursins et à la dissolution biologique du substrat, les propriétés mécaniques des dents des oursins et du squelette des coraux ne semblant pas affectés significativement. Nous suggérons que cette activité érosive accrue pourrait avoir un impact sur l'équilibre dynamique entre bioerosion et bioaccrétion des coraux et pourrait déterminer l'avenir des récifs coralliens où E. mathaei est le principal bioérodeur. Il faut toutefois noter que l’activité érosive de cet oursin est liée à une consommation accrue des macro-algues en compétition avec les coraux et algues corallines, favorisant ainsi ces derniers.

Les résultats obtenus, associés à ceux provenant de la littérature, indiquent que les changements globaux pourraient provoquer un changement profond des écosystèmes coralliens tropicaux. En effet, l’ensemble des bioérodeurs principaux étudiés jusqu’à présent semblent résistants aux changements climatiques globaux et montrent une augmentation de leur activité érosive. Dans le cas des récifs ayant déjà à l’heure actuelle une faible calcification nette, l’augmentation de la bioérosion pourrait mener à l’érosion nette et à la réduction puis à la disparition du récif. La prédiction du devenir des récifs coralliens tropicaux à l’échelle planétaire doit toutefois prendre en compte de nombreux paramètres :acclimatation, résistance/sensibilité et interactions des différents acteurs des récifs. D’autres études comparables à celles menées dans le présent travail devraient être mises en place afin de tester ces différents facteurs. Les données obtenues pourraient dès lors être utilisées dans la construction d’un modèle mécanistique permettant de mettre en place localement des mesures de conservation du récif, en complément de l’indispensable réduction massive de l’émission de CO2 atmosphérique à l’échelle mondiale.

Doctorat en Sciences
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Gómez, Cabrera María del Carmen. "Some aspects of the physiology and ecology of the Acropora longicyathus multi-cladal symbiosis /". [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18706.pdf.

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Oser-Grote, Carolin M. "Aristoteles und das "Corpus Hippocraticum" : die Anatomie und Physiologie des Menschen /". Stuttgart : F. Steiner, 2004. http://catalogue.bnf.fr/ark:/12148/cb39943824x.

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Duret, Margaux. "Organisation spatiale et temporelle de l'activité neuronale du cortex moteur chez le singe macaque dans une tâche d'atteinte et de saisie manuelle". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0408/document.

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Il est classiquement admis que le cortex moteur des primates est organisé topographiquement en lien avec le contrôle des différentes parties du corps. Il a également été suggéré que différentes zones de cette aires corticales pourraient être impliquées dans différents processus de préparation motrice. Suivant cette dernière hypothèse, cette thèse a pour objectif d’étudier les modulations spatiales et temporelles de l’activité neuronale du cortex moteur au cours de la préparation et de l’exécution de mouvements de saisie manuelle. Trois singes ont été entraînés à réaliser une tâche pré-indicée de saisie manuelle. Chez chaque animal, une matrice d’électrodes a été implantée chroniquement dans le cortex moteur. Dans une première étude, nous avons démontré que les modulations d’activité associées à différents processus préparatoires sont localisées dans différentes zones du cortex moteur. Ces zones seraient activées séquentiellement au cours de la préparation motrice suivant une alternance de phases de traitement stationnaire et de propagation dynamique. Dans une seconde étude, nous avons exploré les interactions neuronales par l’utilisation de la mesure de corrélation de variabilité (rsc) entre paires de neurones. Cette deuxième étude a fait ressortir 3 résultats principaux. Les valeurs de rsc sont plus élevées au cours de la préparation du mouvement que lors de son exécution. Elles diminuent avec la distance qui sépare les neurones. Elles sont plus importantes entre interneurones qu’entre neurones supposés pyramidaux. L’ensemble de ces observations ont été discutées en lien avec différentes modèles d’organisation spatiale des aires motrices corticales
The motor cortex follows a somatotopic organization in which the different body parts are controlled by distinct cortical zones. It has also been proposed that different spatial zones of this cortical area could be involed in distinct processes of motor preparation. Following this latter hypothesis, the objective of this thesis is to study the spatio-temporal modulations of motor cortex activity during movement preparation and execution. Three monkeys have been trained in an instructed delayed reach-to-grasp task. In each animal, a multielectrode Utah array was chronically implanted in the motor cortex to explore the dynamic modulations of neural activity during task performance. In a first study, we demonstrated that the modulations of neural activity related to distinct processes of motor preparation occur at different cortical locations. These locations are activated sequentially during motor preparation through alternating phases of stationary processing and dynamic propagation. In a second study, we analysed the neural interactions using a measure of spike count correlation (rsc) between pair of neurons. We reported 3 main results. Correlations are higher during movement preparation than during execution. They decrease with the distance between neurons. Finally, they are higher bewteen putative interneurons than bewteen putative pyramidal neurones. All these observations are discussed in relation to several models of the spatial organization the motor cortex

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Tarczy-Hornoch, Kristina. "Physiology of synaptic inputs to layer IV of cat visual cortex". Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337608.

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Levas, Stephen J. "Biogeochemistry and physiology of bleached and recoverying Hawaiian and Caribbean corals". The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1345229577.

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Fisher, Rebecca Jane. "Inhibition and oscillatory activity in human motor cortex". Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272397.

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Libros sobre el tema "Coraux – Physiologie"

R, Romand, ed. Le Système auditif central: Anatomie et physiologie. Paris: INSERM/SFA, 1992.

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1960-, König Reinhard, ed. The auditory cortex: A synthesis of human and animal research. Mahwah, N.J: Lawrence Erlbaum Associates, 2005.

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Franco, Leporé, Ptito Maurice y Jasper Herbert H. 1906-, eds. Two hemispheres, one brain: Functions of the corpus callosum : proceedings of the Sixth International Symposium of the Centre de recherche en sciences neurologiques of the Université de Montréal, held in Montréal, Canada, May 16-18, 1984. New York: Liss, 1986.

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1947-, Kolb Bryan y Tees Richard C, eds. The Cerebral cortex of the rat. Cambridge, Mass: MIT Press, 1990.

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1943-, Thierry A. M., ed. Motor and cognitive functions of the prefrontal cortex. Berlin: Springer-Verlag, 1994.

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Cortex cerebri: Performance, structural, and functional organization of the cortex. Oxford: Oxford University Press, 1995.

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The motor cortex. New York: Raven Press, 1989.

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Korkovye mekhanizmy proizvolʹnykh dvizheniĭ u cheloveka. Moskva: "Nauka", 1991.

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C, Roberts A., Robbins Trevor W, Weiskrantz Lawrence y Royal Society (Great Britain). Discussion Meeting., eds. The prefrontal cortex: Executive and cognitive functions. Oxford: Oxford University Press, 1998.

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W, Guillery R. y Sherman S. Murray, eds. Exploring the thalamus and its role in cortical function. 2^a ed. Cambridge, Mass: MIT Press, 2006.

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Capítulos de libros sobre el tema "Coraux – Physiologie"

Sapriel, Marc y Patrick Stoltz. "Corpus théorique, physiologie". En Une introduction à la médecine traditionnelle chinoise, 45–190. Paris: Springer Paris, 2006. http://dx.doi.org/10.1007/978-2-287-34692-7_2.

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Armstrong-James, Michael y Kevin Fox. "The Physiology of Developing Cortical Neurons". En Cerebral Cortex, 237–72. Boston, MA: Springer US, 1988. http://dx.doi.org/10.1007/978-1-4615-6619-9_8.

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Amitai, Yael y Barry W. Connors. "Intrinsic Physiology and Morphology of Single Neurons in Neocortex". En Cerebral Cortex, 299–331. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4757-9616-2_7.

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Al-Horani, Fuad A. "Physiology of Skeletogenesis in Scleractinian Coral". En Diseases of Coral, 192–205. Hoboken, NJ: John Wiley & Sons, Inc, 2015. http://dx.doi.org/10.1002/9781118828502.ch12.

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Sorokin, Yuri I. "Morphology and Ecological Physiology of Corals". En Ecological Studies, 296–325. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-80046-7_9.

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Shivambu, Cavin T., Ndivhuwo Shivambu y Colleen T. Downs. "House Crow (Corvus splendens Vieillot, 1817)." En Invasive birds: global trends and impacts, 175–82. Wallingford: CABI, 2020. http://dx.doi.org/10.1079/9781789242065.0175.

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Abstract This chapter describes the common terminologies, taxonomy, morphology, geographical distribution, physiology, diet, behaviour, reproduction, habitats, ecology, invasion pathways, environmental impact, control and human use of the house crow (Corvus splendens).

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Jones, E. G. "Anatomy, Development, and Physiology of the Corpus Callosum". En Epilepsy and the Corpus Callosum, 3–20. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4613-2419-5_1.

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Dove, Sophie G. y Ove Hoegh-Guldberg. "The cell physiology of coral bleaching". En Coral Reefs and Climate Change: Science and Management, 55–71. Washington, D. C.: American Geophysical Union, 2006. http://dx.doi.org/10.1029/61ce05.

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Rueda, Bo R., Debora L. Hamernik, Patricia B. Hoyer y Jonathan L. Tilly. "Potential Regulators of Physiological Cell Death in the Corpus Luteum". En Cell Death in Reproductive Physiology, 161–81. New York, NY: Springer New York, 1997. http://dx.doi.org/10.1007/978-1-4612-1944-6_14.

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Fine, Maoz y Yossi Loya. "Coral Bleaching in a Temperate Sea: From Colony Physiology to Population Ecology". En Coral Health and Disease, 143–56. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-06414-6_6.

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Actas de conferencias sobre el tema "Coraux – Physiologie"

Heeger, David J. y Edward H. Adelson. "Nonlinear model of cat striate physiology". En OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1989. http://dx.doi.org/10.1364/oam.1989.tut2.

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Linear subband image transforms, composed of banks of linear filters tuned to various spatiotemporal frequencies, have been proposed as models of simple cells in striate cortex. Energy measures, composed of the squared sum of the outputs of quadrature pairs of linear filters, have been proposed as models of complex cells. However, given that neurons have a limited dynamic range, the squaring nonlinearity is unreasonable. Thus, we (and others) have proposed that automatic gain control (AGC), mediated by nonlinear (multiplicative) feedback of the contrast signal, plays an important role in striate physiology.

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D'Antonio, Michael P. y C. Kevin Boyce. "THE PHYSIOLOGY OF ARBORESCENT LYCOPSID CORTEX: INSIGHTS FROM COMPARATIVE ANATOMY AND TAPHONOMY". En GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-334407.

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Watanuki, Keiichi, Kenta Hirayama y Kazunori Kaede. "A Near-Infrared Spectroscopy Study of Horizontal Vibration and Comfortableness of a Ride". En ASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/detc2013-13589.

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Comfortableness of a ride is an important issue to passengers and drivers in an automobile. It is difficult to quantify comfortableness of a ride because it is affected by the rider’s emotions and physiology. In this paper, we measure brain activity using near-infrared spectroscopy (NIRS) to examine the features of brain activity that occur when a person is feeling vibration. The results obtained in this study may be used to quantify subjective evaluations of comfortableness of a ride. We measured brain activity during vibrations that are uncomfortable and during vibrations that are not uncomfortable. Uncomfortable vibration and vibrations that were not uncomfortable were determined based on sensory evaluations. Results reveal that oxygenated hemoglobin (oxy-Hb) levels in the prefrontal cortex change when feeling vibration. With uncomfortable vibration oxy-Hb levels declined more than with vibration that was not uncomfortable. In addition, we measured brain activity of riders feeling vibration which evaluation vary among subjects. We found that oxy-Hb of the subjects that feel uncomfortable vibration declined in the prefrontal cortex. Therefore, we inferred that the decline of oxy-Hb in the prefrontal cortex is related to feelings of discomfort.

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Sodre, Maria Eduarda Japyassu, Maria Izabel Wanderley Bezerra, Juliana Oliveira Costa, Diego Shelman de souza Rosado Amaral, Vinicius Guedes Lima Bahia y Maria Isabel Dantas Bezerra Lyra. "Association between religious practices impact on cerebral neurophysiology and radiological expression: a systematic review". En XIII Congresso Paulista de Neurologia. Zeppelini Editorial e Comunicação, 2021. http://dx.doi.org/10.5327/1516-3180.667.

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Introduction: Debates around the correlation between neurophysiological processes and religious habits have gained ground in the research in neuroscience. Objective: To evaluate the impact of religious practices on brain physiology and correlate such behaviors and neuroimaging. Design and setting: It’s a systematic review without metanalysis in PUBMED database. Method: Data carried out in the period 2009 and 2020. Descriptors used: “neural correlates of religious, mystical experience” and “religious belief and neuroimaging”, combined with the Boolean operator “and”. Results: It was noted that the belief is associated with a greater signal in the ventromedial prefrontal cortex, important place for self-representation, emotional associations, reward and goal-directed behavior. Neuroimaging indicated regions associated with these behaviors: pre-cuneiform, anterior insula, ventral striatum, anterior cingulate cortex and posterior medial cortex; nonreligious belief, conversely, registers more signs of memory in the left cerebral hemisphere. Additionally, there is an association between absence of religious practices and depression, anxiety, psychosis, pain disorders; it may have a beneficial impact on the pathogenesis and treatment of these conditions. Conclusion: Although it can be said that the impact exists, more research on the topic is necessary for interventions to have scientific plausibility. The results suggest brain regions involved in religious experience and the phenomenon must be perceived from a multidimensional perspective.

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Pedrigi, Ryan M. y Jay D. Humphrey. "Biomechanics of the Human Anterior Lens Capsule". En ASME 2008 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2008. http://dx.doi.org/10.1115/sbc2008-192073.

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The primary function of the lens of the eye, termed accommodation, is to precisely focus light onto the retina by changing curvature and corresponding refractive power. Investigators have long sought to understand the mechanism of accommodation in terms of interactions of the constituent tissues, which recently has been aided by biomechanical modeling. Such models depend heavily on accurate measurements of tissue mechanical properties and seek to predict stresses and strains. A critical component of the accommodative apparatus is the lens capsule, a bag-like membrane that encapsulates the lens nucleus and cortex and mediates tractions imposed onto this structure by the ciliary body. In addition to this physiologic process during normalcy, the lens capsule also plays a fundamental role in cataract surgery; a procedure that involves three basic steps: a quarter of the anterior lens capsule is removed via the introduction of a continuous circular capsulorhexis (CCC), the lens is broken up and suctioned out, and an artificial intraocular lens (IOL) is placed within the remnant capsular bag. Although novel IOL designs have decreased post-surgical complications, they currently lack the important feature of accommodation. Therefore, mechanical analysis of the lens capsule will allow for an understanding of its interaction with an implant that may further assist in the design of future accommodating IOLs (AIOLs). Here, we report a novel experimental approach to study in situ the regional, multiaxial mechanical behavior of both normal and diabetic human anterior lens capsules. Furthermore, we use these data to calculate material parameters in a nonlinear stress-strain relation via a custom sub-domain inverse finite element method (FEM). These parameters are then used to predict capsular stresses in response to imposed loads using a forward FEM model.

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Nierenberger, Mathieu, Daniel George, Daniel Baumgartner, Yves Rémond, Saïd Ahzi, Renée Wolfram, Jean-Luc Kahn y Rania Abdel Rahman. "Towards Building a Multiscale Mechanical Model for the Prediction of Acute Subdural Hematomas". En ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/esda2012-82457.

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Acute subdural hematoma (ASDH) is a potentially devastating, yet curable, extra axial fluid collection within the subdural space situated between the skull and the cortex. It is often due to rupture of bridging veins crossing this subdural space, caused by the brain-skull relative motion. To be able to predict ASDH, a numerical model reflecting the mechanical properties of vascular walls is attractive. With this in mind, a suitable approach consists in modeling the material microstructure at different scales. In a former work [1, 2], R. Abdel Rahman studied the mechanical properties of the bridging veins – superior sagittal sinus junction when a human head is submitted to shock. This work showed the apparition of ASDH over a given value of head rotational acceleration. But lacks in the knowledge of microstructure and of the constituents mechanical properties were put forward in understanding the relations between material mechanical behavior and the apparition of ASDH. Therefore we chose to adopt a multiscale approach to model ASDH apparition. In the current work, several experimental observations have been set up to obtain a sufficient knowledge of the vein wall microstructure which was imprecisely documented to date. Stained thin slices of human brain were observed by optical microscopy. In addition, microtomography was used to assess the collagen fibers orientations. These observations allowed the identification of the different scales needed for modeling the microstructure. Many authors [3–6] deal with the mechanical behavior of vascular walls and of their various constituents but none of them consider multiple scales for modeling [7]. The next step of this work consists in improving the predictive capabilities of the existing model by going down the scales and taking microstructure into account. This methodology enabled the introduction of only physical parameters into the model, which is essential for future predictive capabilities. Finally, a failure criterion for the bridging veins taking into account the different scales has been created and is still being improved. It allows the evaluation of specific disease influence like collagen damage due to physiology. Besides it provides a prediction tool for ASDH useable for optimization of various shock absorbers.

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Informes sobre el tema "Coraux – Physiologie"

Bazer, Fuller W., Arieh Gertler y Elisha Gootwine. Role of Placental Lactogen in Sheep. United States Department of Agriculture, enero de 2001. http://dx.doi.org/10.32747/2001.7574339.bard.

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Central problems in sheep and dairy cattle production are reproductive failure due to embryonic/fetal mortality and low birth weights, especially in prolific breeds, and reduced milk yields which adversely affect neonatal survival and economy of production. The sheep placenta expresses lactogenic (ovine placental lactogen, oPL) and somatogenic (ovine placental growth hormone, oGH) hormones. Our research has focused on the biological roles of oPL and oGH in function of the uterine endometrium during gestation and the mammary gland during pregnancy and lactation. Major conclusions were that: ( 1 ) immunization of prepubertal ewes against oPL resulted in increased birth weights of their lambs and their milk production during lactation; (2) neither oPL nor oGH had an antiluteolytic effect on uterine endometrium to affect lifespan of the corpus luteum; (3) only sequential exposure of the progesterone stimulated uterus to oIFNt and oPL or oGH increased endometrial gland proliferation and secretory protein gene expression; (4) oPL signals through a homodimer of ovine prolactin receptor (PRL-R) and heterodimer of oPRL-R and growth hormone receptor (GH-R); (5) exogenous recombinant oPL and oGH stimulated mammogenesis and milk yield during lactation; and (6) mutation of oPL and oGH was used to define specific biological effects and a rational basis for design of a specific receptor agonists or antagonists. This project was very productive in elucidating basic biological effects of oPL and oGH on intracellular signal transduction pathways, uterine development and secretory function, as well as mammogenesis and lactogenesis. We determined that immunization of prepubertal ewes against roPL increased birth weights of their lambs, especially those born as twins and triplets, as well as enhanced lactational performance. These studies significantly extended our knowledge of uterine and fetal-placental physiology and provided a foundation for new strategies to enhance reproductive and lactation efficiency. Based on these results, the major achievements were: 1) creation of a practical and cost effective management tool for producers to increase reproductive performance, neonatal survival, and milk yield of ewes in commercial flocks; and 2) define, for the first time, biological effects of oPL on endometrial functions and gene expression by uterine gland epithelium.

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