The characteristics of host lipid body biogenesis during coral-dinoflagellate endosymbiosis

Intracellular lipid body (LB) biogenesis depends on the symbiosis between coral hosts and their Symbiodinaceae. Therefore, understanding the mechanism(s) behind LB biosynthesis in corals can portentially elucide the drivers of cellular regulation during endosymbiosis. This study assessed LB formation in the gastrodermal tissue layer of the hermatypic coral Euphyllia glabrescens. Diel rhythmicity in LB size and distribution was observed; solar irradiation onset at sunrise initiated an increase in LB formation, which continued throughout the day and peaked after sunset at 18:00. The LBs migrated from the area near the mesoglea to the gastrodermal cell border near the coelenteron. Micro-LB biogenesis occurred in the endoplasmic reticulum (ER) of the host gastrodermal cells. A transcriptomic analysis of genes related to lipogenesis indicated that binding immunoglobulin protein (BiP) plays a key role in metabolic signaling pathways. The diel rhythmicity of LB biogenesis was correlated with ER-localized BiP expression. BiP expression peaked during the period with the largest increase in LB formation, thereby indicating that the chaperoning reaction of abnormal protein folding inside the host ER is likely involved in LB biosynthesis. These findings suggest that the host ER, central to LB formation, potentially facilitates the regulation of endosymbiosis between coral hosts and Symbiodiniaceae

Rosetta FunFolDes - A general framework for the computational design of functional proteins

The robust computational design of functional proteins has the potential to deeply impact translational research and broaden our understanding of the determinants of protein function and stability. The low success rates of computational design protocols and the extensive in vitro optimization often required, highlight the challenge of designing proteins that perform essential biochemical functions, such as binding or catalysis. One of the most simplistic approaches for the design of function is to adopt functional motifs in naturally occurring proteins and transplant them to computationally designed proteins. The structural complexity of the functional motif largely determines how readily one can find host protein structures that are "designable", meaning that are likely to present the functional motif in the desired conformation. One promising route to enhance the "designability" of protein structures is to allow backbone flexibility. Here, we present a computational approach that couples conformational folding with sequence design to embed functional motifs into heterologous proteins-Rosetta Functional Folding and Design (FunFolDes). We performed extensive computational benchmarks, where we observed that the enforcement of functional requirements resulted in designs distant from the global energetic minimum of the protein. An observation consistent with several experimental studies that have revealed function-stability tradeoffs. To test the design capabilities of FunFolDes we transplanted two viral epitopes into distant structural templates including one de novo "functionless" fold, which represent two typical challenges where the designability problem arises. The designed proteins were experimentally characterized showing high binding affinities to monoclonal antibodies, making them valuable candidates for vaccine design endeavors. Overall, we present an accessible strategy to repurpose old protein folds for new functions. This may lead to important improvements on the computational design of proteins, with structurally complex functional sites, that can perform elaborate biochemical functions related to binding and catalysis

Plasticity & adaptations of the coral-zooxanthellae symbiosis: responses to nutrient availability & insight into inherent thermal tolerance

Sustaining an environment which conveys a high resilience to reef corals is critical in order to mitigate the immediate threat of climate change to reef ecosystems. The nutrient environment plays a significant role in sustaining the stability of the coral-zooxanthellae symbiosis, making anthropogenic nutrient pollution as well as the climate change driven nutrient impoverishment of oceanic waters pressing threats to coral reef persistence. Yet, many aspects of coral nutrient biology remain poorly understood, impeding science driven management strategies. This thesis aimed to advance our knowledge on how different nutrient environments affect the functioning of the coral-algal symbiosis by teasing apart the interacting effects of two principal nutrient sources (dissolved inorganic nutrient uptake and heterotrophic feeding), as well as of the two essential nutrients, nitrogen and phosphorus, both in dissolved inorganic and particulate organic forms. This was achieved through long-term exposure (up to 1.5 years) of the Euphyllia paradivisa-clade C1 Symbiodinium association to replete (+N+P), limited (-N-P), or imbalanced (+N-P/-N+P) dissolved inorganic nutrient availabilities in combination with targeted host feeding with balanced or nitrogen enriched prey items. Thereby, this work stood apart from past investigations by yielding definitive phenotypes representative of different nutrient availabilities. Moreover, the importance of food quality when considering the benefit of heterotrophy to reef corals had previously been overlooked. Findings suggest that heterotrophy provides a greater benefit to the coral host than to the symbiont and is unable to compensate for diminished dissolved inorganic nutrient availability, demonstrating a significantly greater dependence of the symbiosis to the latter nutrient source. A balanced N/P ratio, both in dissolved inorganic and particulate organic form, was shown to be essential for the stability of the symbiosis and for the nutritional benefit provided by heterotrophy. Particularly nitrogen enrichment resulted in severe nutrient stress and compromised thermal stress resilience, implying a vital reliance on a continued supply of phosphorus and emphasising the necessity of managing nitrogen pollution and monitoring N/P ratios. Zooxanthellae ultrastructural biomarkers established in this thesis (cell size, lipid body, starch granule and uric acid crystal accumulation, accumulation body fragmentation) hold potential for the aid in the identification of, and discrimination between different forms of nutrient stress in reef corals. Yet, ultimately corals need to adapt to warmer oceans. Diverse Symbiodinium genotypes convey varied thermal tolerance to their coral host. Yet, the mechanisms underpinning their thermal sensitivity remain largely elusive. The second aim of this thesis was to examine the role played by the algal membrane composition. The intact polar lipid biochemistry of a thermally-sensitive (clade C) and -tolerant (clade D) type were characterised by HPLC-ESI tandem mass spectrometry. Distinctions in chloroplast membrane composition could be related to differential inherent thermal tolerance. Moreover, vast differences in the lipid biochemistry of extraplastidic membranes were identified, exemplifying unprecedented metabolic differences among Symbiodinium clades. Biochemical markers of a thermally tolerant phenotype (MGDG/DGDG ratio, glycolipid saturation) could advance our understanding and projections of the potential of reef corals to acclimate and adapt to future climate change scenarios

Effet de la technique d'endartériectomie carotidienne sur l'équilibre tensionnel (désobstruction par retournement versus désobstruction avec fermeture sur patch)

L'hypertension artérielle après chirurgie carotidienne est un facteur de risque non négligeable de complications post-opératoires. L'objectif de notre étude était de comparer l'incidence de l'hypertension artérielle post-opératoire, définie comme une pression artérielle systolique supérieure ou égale à 160 mmHg et/ou l'utilisation d'agents vasodilatateurs post-opératoires, entre 2 techniques d'endartériectomie carotidienne : la désobstruction par retournement et la désobstruction avec fermeture sur patch. Dans notre étude prospective réalisée entre janvier 2009 et juin 2010, 443 patients (72.5% d'hommes et 27.5% de femmes) ont bénéficié de 560 endartériectomies carotidiennes, dont 340 avec fermeture sur patch (groupe patch) et 220 par éversion (groupe éversion), pour traiter 119 lésions symptomatiques et 442 lésions asymptomatiques. Toutes les interventions ont été réalisées sous anesthésie générale. parmi les facteurs de risque cardiovasculaire, 81% avaient une hypertension artérielle, 29% un diabète et 84% une dyslipémie, 19% un tabagisme actif et 44% étaient sevrés. Le traitement anti-hypertenseurs a été maintenu jusqu'au matin de l'intervention pour 57% des hypertendus, il s'agissait majoritairement de bétabloquants (96.7%). Les mesures de pressions artérielles et de fréquence cardiaque effectuées en pré-opératoire (en consultation d'anesthésie et au bloc opératoire avant l'induction), puis au clampage et au déclampage, à H1, H2, H3, H4, H6, H12, H24, H48, J3, J4, J5 et J6, l'infiltration du glomus carotidien, les traitements anti-hypertenseurs post-opératoires, les complications post-opératoires et les décès ont été comparés entre les 2 groupes. Il n'y a pas eu de différence significative entre les 2 groupes en termes d'hypertension artérielle post-opératoire (p=0.06). La moyenne des pressions artérielles systoliques a été significativement plus élevée dans le groupe éversion de H2 à H12, mais sans atteindre 160 mmHg. Par ailleurs, dans le groupe patch, il existe une tendance à l'hypotension artérielle par rapport aux valeurs des pressions artérielles systoliques préopératoires. Nous avons identifié 2 facteurs de risque indépendants d'hypertension artérielle après la 24ème heure post-opératoire : l'hypertension artérielle pré-existante et l'utilisation d'agents vasodilatateurs dans les 24 premières heures post-opératoires. Le groupe éversion a eu significativement plus d'infiltration du glomus. Les 2 groupes ont été comparables en termes d'accidents vasculaires cérébraux, d'infractus du myocarde et de décès. Le TCCM global a été de 2.1% soit 1.7% dans le groupe éversion versus 2.4% dans le groupe patch (p=0.54). L'endartériectomie carotidienne par éversion n'apparaît pas être un facteur de risque d'hypertension artérielle post-opératoire, telle que nous l'avons définie. Cependant, les variations tensionnelles ont tendance à être moins importantes après éversion carotidienne. Cette technique d'endartériectomie pourrait protéger d'une hypotension artérielle relative. Mais, il existe un biais représenté par l'infiltration du glomus dont le rôle protecteur contre l'hypertension artérielle reste encore à démontrer. Une surveillance particulière de la tension artérielle doit être réalisée chez les patients hypertendus et ceux qui ont nécessité l'administration d'un agent vasodilatateur dans les 24 premières heures.CLERMONT FD-BCIU-Santé (631132104) / SudocSudocFranceF

Ultrastructural biomarkers in symbiotic algae reflect the availability of dissolved inorganic nutrients and particulate food to the reef coral holobiont

Reef building corals associated with symbiotic algae (zooxanthellae) can access environmental nutrients from different sources, most significantly via the uptake of dissolved inorganic nutrients by the algal symbiont and heterotrophic feeding of the coral host. Climate change is expected to alter the nutrient environment in coral reefs with the potential to benefit or disturb coral reef resilience. At present, the relative importance of the two major nutrient sources is not well understood, making predictions of the responses of corals to changes in their nutrient environment difficult. Therefore, we have examined the long-term effects of the availability of different concentrations of dissolved inorganic nutrients and of nutrients in particulate organic form on the model coral Euphyllia paradivisa. Coral and algal biomass showed a significantly stronger increase in response to elevated levels of dissolved inorganic nutrients as compared to the supply with particulate food. Also, changes in the zooxanthellae ultrastructure, determined by transmission electron microscopy (TEM), were mostly driven by the availability of dissolved inorganic nutrients under the present experimental conditions. The larger size of symbiont cells, their increased accumulation of lipid bodies, a higher number of starch granules and the fragmentation of their accumulation body could be established as reliable biomarkers of low availability of dissolved inorganic nutrients to the coral holobiont

Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates

Enrichment of reef environments with dissolved inorganic nutrients is considered a major threat to the survival of corals living in symbiosis with dinoflagellates (Symbiodinium sp.). We argue, however, that the direct negative effects on the symbiosis are not necessarily caused by the nutrient enrichment itself but by the phosphorus starvation of the algal symbionts that can be caused by skewed nitrogen (N) to phosphorus (P) ratios. We exposed corals to imbalanced N:P ratios in long-term experiments and found that the undersupply of phosphate severely disturbed the symbiosis, indicated by the loss of coral biomass, malfunctioning of algal photosynthesis and bleaching of the corals. In contrast, the corals tolerated an undersupply with nitrogen at high phosphate concentrations without negative effects on symbiont photosynthesis, suggesting a better adaptation to nitrogen limitation. Transmission electron microscopy analysis revealed that the signatures of ultrastructural biomarkers represent versatile tools for the classification of nutrient stress in symbiotic algae. Notably, high N:P ratios in the water were clearly identified by the accumulation of uric acid crystals

Prédictions of autogenous arteriovenous hemodialysis access thrombosis after renal transplantation

We conducted a monocentric retrospective review of prospective clinical records of 145 patients with a functional aAVF who had a RT between January 2004 and December 2009 in the University Hospital of Clermont-Ferrand. Our primary endpoint was the thrombosis of the aAVF. Univariate and multiple logistic regression analyses were used to identify risk factors associated to aAVF thrombosis after RT.ResultsThere were 105 men (72 %) and 40 women (28 %), mean age 52 years (range: 18.4-74.7 years). The aAVF was created on average 40 months (range: 2-169) before the RT. The aAVF was distal, in 96 cases (66 %) and proximal in 49 cases (34%). Nineteen aAVF (13.1%) were complicated and required an endovascular or surgical repair before RT. Forty-nine patients (34%) required multiple aAVF (>2). Mean follow-up from RT was 58 months (0.03-123) and from aAVF creation 97 months (5-262). At the end of the follow-up, 81 aAVFs (59%) were patent, 42 (29%) were thrombosed and 22 (15%) were surgically closed. Patients that had multiple fistulas before RT and active smokers were significantly at risk to thrombose their aAVF after the RT in univariate (respectively, P=0.03 and P=0.02) and multiple logistic regression analyses (respectively, P=0.03 and P=0.047).ConclusionsThrombosis is a part of the natural history of the aAVF after RT. A history of multiple aAVF creations before RT and active smoking were associated to significant increased risk for fistula thrombosis. Because hemodialysis may be needed after RT, the aAVF patency should be preserved, excepted when the aAVF resulted in complications. Follow-up of the aAVF after RT is important to detect and treat complications before thrombosis occurs

CFD Analyses of Different Parameters Influencing the Hemodynamic Outcomes of Complex Aortic Endovascular Repair

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