Effects of Oxygen During Long-term Hypothermic Machine Perfusion in a Porcine Model of Kidney Donation After Circulatory Death

International audienceBackground:Hypothermic machine perfusion (HMP) has become standard care in many center’s to preserve kidneys donated after circulatory death (DCD). Despite a significant reduction in metabolism at low temperatures, remaining cellular activity requires oxygen. Since the role and safety of oxygen during HMP has not been fully clarified, its supply during HMP is not standard yet. This study investigates the effect of administering oxygen during HMP on renal function in a porcine DCD model.Methods: After 30 minutes of warm ischemia, porcine slaughterhouse kidneys were preserved for 24 hours by means of cold storage (CS), or HMP with Belzer Machine Perfusion Solution (UW- MPS) supplemented with no oxygen, 21% or 100% oxygen. Next, kidneys were reperfused for 4 hours in a normothermic machine perfusion (NMP) setup.Results:HMP resulted in significantly better kidney function during NMP. Thiobarbituric acid-reactive substances (TBARS), markers of oxidative stress, were significantly lower in HMP preserved kidneys. HMP preserved kidneys showed significantly lower ASAT and LDH levels compared to kidneys preserved by CS. No differences were found between the HMP groups subjected to different oxygen concentrations. ATP levels significantly improved during HMP when active oxygenation was applied.Conclusion:This study showed that preservation of DCD kidneys with HMP is superior to CS. Although the addition of oxygen to HMP did not result in significantly improved renal function, beneficial effects were found in terms of reduced oxidative stress and energy status. Oxygen addition proofed to be safe and did not show detrimental effects

Impact of Red Blood Cells on Function and Metabolism of Porcine Deceased Donor Kidneys During Normothermic Machine Perfusion

Background. Normothermic machine perfusion (NMP) protocols using blood-based solutions are commonly used in the assessment of kidneys before transplantation. This procedure is, nevertheless, limited by blood availability and warrants the search for alternatives. We compared a blood-based solution with a serum-like preservation solution (Aqix) enriched with colloids with and without red blood cells (RBCs). Methods. Porcine kidneys retrieved from an abattoir were subjected to 30min of warm ischemia, followed by 3h of hypothermic oxygenated machine perfusion at 4 degrees C. Subsequently, kidneys (n=6 per group) were evaluated with NMP for 4h with 5 different solutions: diluted blood, Aqix with BSARBCs, or Aqix with dextran 40RBCs. Results. Throughout NMP, markers of renal function and tubular metabolism were favorable in groups with RBCs. The addition of RBCs resulted in 4- to 6-fold higher oxygen consumption rates. Controls had significantly higher ATP levels post-NMP, exhibited decreased production of oxidative stress markers, and had the highest creatinine clearance. In conclusion, this study shows that the addition of RBCs during NMP reduced renal injury, improved function, and was associated with increased renal metabolism. Conclusions. Although the RBC-BSA-supplemented Aqix solution was also able to support metabolism and renal function, a blood-based perfusion solution remains superior

SAPHIR - a multi-scale, multi-resolution modeling environment targeting blood pressure regulation and fluid homeostasis.

International audienceWe present progress on a comprehensive, modular, interactive modeling environment centered on overall regulation of blood pressure and body fluid homeostasis. We call the project SAPHIR, for "a Systems Approach for PHysiological Integration of Renal, cardiac, and respiratory functions". The project uses state-of-the-art multi-scale simulation methods. The basic core model will give succinct input-output (reduced-dimension) descriptions of all relevant organ systems and regulatory processes, and it will be modular, multi-resolution, and extensible, in the sense that detailed submodules of any process(es) can be "plugged-in" to the basic model in order to explore, eg. system-level implications of local perturbations. The goal is to keep the basic core model compact enough to insure fast execution time (in view of eventual use in the clinic) and yet to allow elaborate detailed modules of target tissues or organs in order to focus on the problem area while maintaining the system-level regulatory compensations

CMS physics technical design report : Addendum on high density QCD with heavy ions

Peer reviewe

The streamlined genome of Phytomonas spp. relative to human pathogenic kinetoplastids reveals a parasite tailored for plants

Members of the family Trypanosomatidae infect many organisms, including animals, plants and humans. Plant-infecting trypanosomes are grouped under the single genus Phytomonas, failing to reflect the wide biological and pathological diversity of these protists. While some Phytomonas spp. multiply in the latex of plants, or in fruit or seeds without apparent pathogenicity, others colonize the phloem sap and afflict plants of substantial economic value, including the coffee tree, coconut and oil palms. Plant trypanosomes have not been studied extensively at the genome level, a major gap in understanding and controlling pathogenesis. We describe the genome sequences of two plant trypanosomatids, one pathogenic isolate from a Guianan coconut and one non-symptomatic isolate from Euphorbia collected in France. Although these parasites have extremely distinct pathogenic impacts, very few genes are unique to either, with the vast majority of genes shared by both isolates. Significantly, both Phytomonas spp. genomes consist essentially of single copy genes for the bulk of their metabolic enzymes, whereas other trypanosomatids e.g. Leishmania and Trypanosoma possess multiple paralogous genes or families. Indeed, comparison with other trypanosomatid genomes revealed a highly streamlined genome, encoding for a minimized metabolic system while conserving the major pathways, and with retention of a full complement of endomembrane organelles, but with no evidence for functional complexity. Identification of the metabolic genes of Phytomonas provides opportunities for establishing in vitro culturing of these fastidious parasites and new tools for the control of agricultural plant disease. © 2014 Porcel et al

Modélisation du système rénine-angiotensine endocrine et intégration au sein d'un modèle de la régulation des fluides et de la pression artérielle

POITIERS-BU Médecine pharmacie (861942103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

A Computational Model of the Circulating Renin-Angiotensin System and Blood Pressure Regulation

International audienceThe renin-angiotensin system (RAS) is critical in sodium and blood pressure (BP) regulation, and in cardiovascular-renal (CVR) diseases and therapeutics. As a contribution to SAPHIR project, we present a realistic computer model of renin production and circulating RAS, integrated into Guyton's circulatory model (GCM). Juxtaglomerular apparatus, JGA, and Plasma modules were implemented in C ++/M2SL (Multi-formalism Multi-resolution Simulation Library) for fusion with GCM. Matlab optimization toolboxes were used for parameter identification. In JGA, renin production and granular cells recruitment (GCR) are controlled by perfusion pressure (PP), macula densa (MD), angiotensin II (Ang II), and renal sympathetic activity (RSNA). In Plasma, renin and ACE (angiotensin-converting enzyme) activities are integrated to yield Ang I and II. Model vs. data deviation is given as normalized root mean squared error (nRMSE; n points)

Modélisation mathématique et simulation numérique de la polymérisation de l'hémoglobine drépanocytaire

La drépanocytose, ou anémie falciforme, présente une variabilité interindividuelle considérable, conditionnée par de multiples facteurs, dynamiques et interactifs, depuis le niveau moléculaire jusqu au niveau du patient. L hémoglobine drépanocytaire, ou hémoglobine S (HbS, tétramère a2bS 2), est un mutant de l hémoglobine A (a2b2) : elle possède à sa surface une valine (hydrophobe) substituant un acide glutamique natif (négativement chargé). Cette mutation entraîne l agrégation de l HbS désoxygénée en polymères, ainsi que l altération des propriétés de l érythrocyte -dont sa rhéologie et ses interactions avec les différentes cellules vasculaires. C est pourquoi la polymérisation de l HbS constitue un facteur étiologique clef, sinon le primum movens, de la drépanocytose, et une hypothèse thérapeutique (étayée par l observation) postule que la réduction des fibres intra-érythrocytaires de HbS pourrait améliorer le statut clinique des patients en abaissant la fréquence et la sévérité des crises vasoocclusives. Dans l optique de mieux comprendre et de mieux gérer la variabilité individuelle drépanocytaire, il apparaît donc indispensable de disposer, en premier lieu, d une description réaliste de la polymérisation de l HbS. L objectif de ce travail de thèse est la mise en place et la validation d un modèle mathématique de la polymérisation de l HbS désoxygénée, en tant que processus cinétiquethermodynamique, sous l influence de la concentration et de la température les deux facteurs modulateurs les plus importants. A partir d un modèle existant, mais linéaire et incomplet (Ferrone et al., 1985), nous avons procédé à son implémentation, à sa correction et à sa mise à jour, ainsi qu à l évaluation quantitative de ses performances dynamiques, par intégration complète et simulation numérique (Simulink ). Ceci nous a permis de réaliser un diagnostic et d effectuer un certain nombre de raffinements, concernant en particulier (i) la voie de nucléation hétérogène (formation de néo-fibres sur les fibres préexistantes), (ii) la non-idéalité de la solution protéique de HbS, induite par le volume exclus des fibres polymères (coefficients d activité calculé à partir de la théorie des particules convexes ), ainsi que (iii) la structuration spatiale des polymères en domaines. Le modèle développé dans ce travail servira de base pour une description (i) de l influence dynamique de l oxygénation et des hémoglobines non-polymérisantes sur la polymérisation de HbS, puis (ii) des polymères de HbS sur les propriétés membranaires et rhéologiques de l érythrocyte drépanocytaire.Sickle cell disease pathology exhibits a strong interindividual variability, which depends upon multiple, dynamic and interacting factors, from the molecular to the patient level. Sickle hemoglobin, hemoglobin S (HbS, a2bS 2 tetramer), is a mutant of HbA (a2b2), with a surface valine (hydrophobic) substituting a native glutamic acid (negatively charged). Such a mutation endows deoxygenated HbS with the propensity to agregate into polymers, altering erythrocyte properties including its rheology and its interactions with vascular and circulatory cells. Thus HbS polymerization is a key etiological factor of sickle cell disease, if not the primum movens. Indeed, one therapeutical hypothesis (supported by observation) postulates that the reduction of intra-erythrocytic HbS fibers could improve patients clinical status by lowering the frequency and the severity of vasooclusive crisis. In order to better understand and manage sickle cell disease variability, it is essential to have a realistic description of HbS polymerization. This work aims at developing and validating a mathematical model of deoxygenated HbS polymerization, as a kinetic and thermodynamic process under the influence of concentration and temperature the two most important modulators. Building on an existing, but linearized and uncomplete (Ferrone et al., 1985) model, we have implemented, corrected and updated, and quantitatively evaluated its dynamical performances: this was done by full numerical integration using Simulink . This allowed us to make several improvements, related in particular to : (i) the heterogeneous nucleation pathway (seeding and formation of new fibers from pre-existing ones), (ii) the non-ideality of the HbS protein solution, caused by polymer fibers excluded volume (activity coefficients were calculated with the CPT, Convex Particle Theory), and (iii) the spatial organization of polymers into domains. The model developped in this work will ground the description of the dynamic influence (i) oxygenation and non-polymerizing hemoglobins, (ii) HbS polymers interactions with membrane and consequences upon rheological properties of sickle cell erythrocyte.PARIS-EST-Université (770839901) / SudocPARIS12-Bib. électronique (940280011) / SudocSudocFranceF

From channelopathies to hypertension: A multi-mode modeling approach for exploration of heterogeneous systems spanning many scales and involving multiple organ systems

Despite the development of ever more sophisticated models at many scales, from the level of gene regulation or intra-cellular signal transduction or cellular metabolism, through models of tissue function, epithelial transport, or even whole organ physiology, there is presently, to our knowledge, no comprehensive, organism-level modeling environment that allows exploration of the whole chain of regulatory influences brought into play by a local perturbation such as a defect in a cell membrane ion transport protein. To fill this need, we are developing a comprehensive, modular, interactive modeling environment centered on overall regulation of blood pressure and body fluids. We rely on state-of-the-art multi-scale, multi-mode simulation methods. The core model will give succinct input-output (reduced-dimension) descriptions of all relevant organ systems and regulatory processes, and it will be modular, multi-resolution, and extensible, in the sense that detailed sub-modules of any process(es) can be "plugged-in" to the basic model in order to explore, e.g., system-level implications of local perturbations. The goal is to keep the basic core model compact enough to insure fast execution time (in view of eventual use in the clinic) and yet to allow elaborate detailed modules of target tissues or organs in order to focus on the problem area while maintaining the system-level regulatory compensations. We will present the core model, inspired by Guyton's classic 1972 model of overall regulation of blood pressure, and several aspects of the renal, cardiac, and lung modules to be included in the initial development

Oxidative Stress Evaluation in Ischemia Reperfusion Models: Characteristics, Limits and Perspectives

International audienceIschemia reperfusion injury is a complex process consisting of a seemingly chaotic but actually organized and compartmentalized shutdown of cell function, of which oxidative stress is a key component. Studying oxidative stress, which results in an imbalance between reactive oxygen species (ROS) production and antioxidant defense activity, is a multi-faceted issue, particularly considering the double function of ROS, assuming roles as physiological intracellular signals and as mediators of cellular component damage. Herein, we propose a comprehensive overview of the tools available to explore oxidative stress, particularly in the study of ischemia reperfusion. Applying chemistry as well as biology, we present the different models currently developed to study oxidative stress, spanning the vitro and the silico, discussing the advantages and the drawbacks of each set-up, including the issues relating to the use of in vitro hypoxia as a surrogate for ischemia. Having identified the limitations of historical models, we shall study new paradigms, including the use of stem cell-derived organoids, as a bridge between the in vitro and the in vivo comprising 3D intercellular interactions in vivo and versatile pathway investigations in vitro. We shall conclude this review by distancing ourselves from “wet” biology and reviewing the in silico, computer-based, mathematical modeling, and numerical simulation options: (a) molecular modeling with quantum chemistry and molecular dynamic algorithms, which facilitates the study of molecule-to-molecule interactions, and the integration of a compound in a dynamic environment (the plasma membrane...); (b) integrative systemic models, which can include many facets of complex mechanisms such as oxidative stress or ischemia reperfusion and help to formulate integrated predictions and to enhance understanding of dynamic interaction between pathways