In seawater, drinking is a fundamental part of the osmoregulatory strategy for teleost fish, and presents a unique challenge. The intestine has an established role in osmoregulation, and its ability to effectively absorb fluid from imbibed seawater is crucial to compensating for water losses to the surrounding hyperosmotic environment. Alongside solute-linked water transport (driven by NaCl cotransport), intestinal bicarbonate (HCO3-) secretion also benefits fluid absorption directly (via apical Cl-/HCO3- exchange), and indirectly through the formation of calcium carbonate (CaCO3) thus removing the osmotic influence of Ca2+ within the gut fluid. For the European flounder (Platichthys flesus), elevated luminal Ca2+ has proven to be a specific, potent stimulator of HCO3- secretion both in vitro and in vivo where these actions are presumably modulated by an extracellular Ca2+-sensing receptor (CaR). The focus of this work was to learn more about how intestinal HCO3- secretion is regulated, the role of Ca2+, and more specifically the CaR. To achieve this, in vitro ‘gut sac’ experiments investigated how luminal Ca2+ influenced HCO3- secretion, and associated ion and fluid transport. Contrary to expectation, increasing Ca2+ from 5 to 20 mM did not stimulate HCO3- secretion. In an attempt to elucidate the role of CaCO3 precipitation in fluid absorption, and further explore the physiological implications of HCO3- secretion, the intestine was perfused in vivo with salines containing varying concentrations of Ca2+ (10, 40 and 90 mM). The production and secretion of HCO3-, in addition to CaCO3 formation increased accordingly with Ca2+, and was associated with a dramatic 25 % rise in the fraction of fluid absorbed by the gut. Additional in vitro experiments, utilising the Ussing chamber, helped establish some of the characteristics of intestinal HCO3- secretion by the euryhaline killifish (Fundulus heteroclitus), but was unresponsive to elevated mucosal Ca2+. Further attempts to potentiate the activity of the CaR, and application of the receptor agonists gadolinium (Gd3+) and neomycin, failed to produce responses consistent with the effect of Ca2+ observed previously, either in vitro or in vivo. With no evidence supporting a direct role for an extracellular, intestinal CaR in HCO3- secretion it was argued that secretion would be principally regulated by two factors, the ability of the epithelia to generate high levels of intracellular HCO3- and the rate of CaCO3 formation.

Industry surveys indicated that up to 16percent of pork is pale, soft, and exudative (PSE); which has reduced functionality. Recently, the cost of sodium phosphates (SP) has escalated. SPs are used to improve water holding capacity (WHC), increase pH, and retard lipid oxidation. Alkaline non-meat ingredient addition could improve PSE pork functionality and replace SP in pork products. The objective was to examine effects of alkaline solutions on pH, color, WHC, and texture of PSE and normal pork gels. Normal (pH 5.6-5.9) and PSE (pH ≤ 5.4) loins were obtained and homogenized. Treatment solutions were: no added solution (control); double-distilled deionized water (ddW); 0.1, 0.2, and 0.3 pecent(w/v) SP; and 0.1, 0.2, and 0.3M potassium bicarbonate (PB), sodium bicarbonate (SB), potassium carbonate (PC), or sodium carbonate (SC). PSE gels had lighter color, lower pH, WHC, and cook yields, and higher TPA values than normal gels. Control and ddW gels had lower pH, and higher L*, a*, and b* values. As treatment levels increased, gels had higher pH, and lower L*, a*, and b* values. SP gels had lower pH, WHC, cook yields, and higher L*, a*, b*, and TPA values compared to PB, SB, PC, and SC gels. PC and SC gels had higher cook yields than normal control gels and PB and SB gels were intermediate. For both meat types, TPA values improved for PB and SB gels compared to normal control gels, but did not differ from SP gels. As levels of PC and SC increased, gels were softer, less cohesive, chewy, and lower in work 2 than other gels. Cooked PSE gels treated with 0.2 or 0.3M PC or SC were less red and yellow and had cook yields that surpassed normal control and ddW gels. Normal and PSE gels treated with 0.2 or 0.3M PC or SC did not differ in TPA measurements for hardness and work. PSE pork functionality was improved with PC or SC addition to be similar to or higher than normal samples. PC and SC are feasible alternatives to replace SP in pork gel systems without loss of WHC, color, or pH.

Le bicarbonate de soude raffiné, produit industriellement par la société Solvay, est fabriqué dans des colonnes à bulles de grande taille, appelées les colonnes BIR.<p>Dans ces colonnes, une phase gazeuse contenant un mélange d’air et dioxyde de carbone (CO2) est dispersée sous forme de bulles dans une solution aqueuse de carbonate et de bicarbonate de sodium (respectivement Na2CO3 et NaHCO3). Cette dispersion donne lieu à un transfert de CO2 des bulles vers la phase liquide. Au sein des colonnes, la phase gazeuse se répartit dans deux populations de bulles :des petites bulles (diamètre de quelques mm) et des grandes bulles (diamètre de quelques cm). Le transfert bulle-liquide de CO2 est couplé à des réactions chimiques prenant place en phase liquide, qui conduisent à la conversion du Na2CO3 en NaHCO3. Une fois la concentration de saturation dépassée le NaHCO3 précipite sous forme de cristaux et un mélange liquide-solide est recueilli à la sortie de ces colonnes.<p>Ce travail, réalisé en collaboration avec la société Solvay, porte sur l’étude et la modélisation mathématique des phénomènes de transfert de matière entre phases, couplés à des réactions chimiques, prenant place au sein d’une colonne BIR. L’association d’études sur des colonnes à bulles à l’échelle industrielle ou réduite (pilote) et d’études plus fondamentales sur des dispositifs de laboratoire permet de développer une meilleure compréhension du fonctionnement des colonnes BIR et d’en construire un modèle mathématique détaillé.<p>L’objectif appliqué de ce travail est la mise au point d’un modèle mathématique complet et opérationnel d’une colonne BIR. Cet objectif est supporté par trois blocs de travail, dans lesquels différents outils sont développés et exploités.<p><p>Le premier bloc est consacré à la modélisation mathématique du transfert bulle-liquide de CO2 dans une solution aqueuse de NaHCO3 et de Na2CO3. Ce transfert est couplé à des réactions chimiques en phase liquide qui influencent sa vitesse. Dans un premier temps, des modèles sont développés selon des approches unidimensionnelles classiquement rencontrées dans la littérature. Ces approches passent par une idéalisation de l’écoulement du liquide autour des bulles. Une expression simplifiée de la vitesse du transfert bulle-liquide de CO2, est également développée et validée pour le modèle de colonne BIR.<p>Dans un second temps, une modélisation complète des phénomènes de transport (convection et diffusion), couplés à des réactions chimiques, est réalisée en suivant une approche bidimensionnelle axisymétrique. L’influence de la vitesse de réactions sur la vitesse de transfert est étudiée et les résultats des deux approches sont également comparés.<p><p>Le deuxième bloc est consacré à l’étude expérimentale du transfert gaz-liquide de CO2 dans des solutions aqueuses de NaHCO3 et de Na2CO3. A cette fin, un dispositif expérimental est développé et présenté. Du CO2 est mis en contact avec des solutions aqueuses de NaHCO3 et de Na2CO3 dans une cellule transparente. Les phénomènes provoqués en phase liquide par le transfert de CO2 sont observés à l’aide d’un interféromètre de Mach-Zehnder.<p>Les résultats expérimentaux sont comparés à des résultats de simulation obtenus avec un des modèles unidimensionnels développés dans le premier bloc. De cette comparaison, il apparaît qu’une mauvaise estimation de la valeur de certains paramètres physico-chimiques apparaissant dans les équations de ce modèle conduit à des écarts significatifs entre les grandeurs observées expérimentalement et les grandeurs estimées par simulation des équations du modèle.<p>C’est pourquoi une méthode d’estimation paramétrique est également développée afin d’identifier les valeurs numériques de ces paramètres physico-chimiques sur base des résultats expérimentaux. Ces dernières sont également discutées.<p><p>Dans le troisième bloc, nous apportons une contribution à l’étude des cinétiques de précipitation du NaHCO3 dans un cristallisoir à cuve agitée. Cette partie du travail est réalisée en collaboration avec Vanessa Gutierrez (du service Matières et Matériaux de l’ULB).<p>Nous contribuons à cette étude par le développement de trois outils :une table de calcul Excel permettant de synthétiser les résultats expérimentaux, un ensemble de simulations de l’écoulement au sein du cristallisoir par mécanique des fluides numérique et une nouvelle méthode d’extraction des cinétiques de précipitation du NaHCO3 à partir des résultats expérimentaux. Ces trois outils sont également utilisés de façon combinée pour estimer les influences de la fraction massique de solide et de l’agitation sur la cinétique de germination secondaire du NaHCO3.<p><p>Enfin, la synthèse de l’ensemble des résultats de ces études est réalisée. Le résultat final est le développement d’un modèle mathématique complet et opérationnel des colonnes BIR. Ce modèle est développé en suivant l’approche de modélisation en compartiments, développée au cours du travail de Benoît Haut. Ce modèle synthétise les trois blocs d’études réalisées dans ce travail, ainsi que les travaux d’Aurélie Larcy (du service Transferts, Interfaces et Procédés de l’ULB) et de Vanessa Gutierrez. Les équations modélisant les différents phénomènes sont présentées, ainsi que la méthode utilisée pour résoudre ces équations. Des simulations des équations du modèle sont réalisées et discutées. Les résultats de simulation sont également comparés à des mesures effectuées sur une colonne BIR. Un accord raisonnable est observé.<p>A l’issue de ce travail, nous disposons donc d’un modèle opérationnel de colonne BIR. Bien que ce modèle doive encore être optimisé et validé, il peut déjà être utilisé pour étudier l’effet des caractéristiques géométriques des colonnes BIR et des conditions appliquées à ces colonnes sur le comportement des simulations des équations du modèle et pour identifier des tendances.<p>//<p>The refined sodium bicarbonate is produced by the Solvay company using large size bubble columns, called the BIR columns.<p>In these columns, a gaseous phase containing an air-carbon dioxyde mixture (CO2) is dispersed under the form of bubbles in an aqueous solution of sodium carbonate and sodium bicarbonate (Na2CO3 and NaHCO3, respectively). This dispersion leads to a CO2 transfer from the bubbles to the liquid phase. Inside these columns, the gaseous phase is distributed in two bubbles populations :small bubbles (a few mm of diameter) and large bubbles (a few cm of diameter).<p>The bubble-liquid CO2 transfer is coupled with chemical reactions taking places in the liquid phase that leads to the conversion of Na2CO3 to NaHCO3. When the solution is supersaturated in NaHCO3, the NaHCO3 precipitates under the form of crystals and a liquid-solid mixture is extracted at the outlet of the BIR columns.<p>This work, realized in collaboration with Solvay, aims to study and to model mathematically the mass transport phenomena between the phases, coupled with chemical reactions, taking places inside a BIR column. Study of bubble columns at the industrial and the pilot scale is combined to a more fundamental study at laboratory scale to improve the understanding of the BIR columns functioning and to develop a detailed mathematical modeling.<p>The applied objective of this work is to develop a complete and operational mathematical modeling of a BIR column. This objective is supported by three blocks of work. In each block, several tools are developed and used.<p><p>The first block is devoted to the mathematical modeling of the bubble-liquid CO2 transfer in an NaHCO3 and Na2CO3 aqueous solution. This transfer is coupled with chemical reactions in liquid phase, which affect the transfer rate.<p>In a first time, mathematical models are developed following the classical one-dimensional approaches of the literature. These approaches idealize the liquid flow around the bubbles. A simplified expression of the bubble-liquid CO2 transfer rate is equally developed and validated for the BIR column model.<p>In a second time, a complete modeling of the transport phenomena (convection and diffusion) coupled with chemical reactions is developed, following an axisymmetrical twodimensional approach. The chemical reaction rate influence on the bubble-liquid transfer rate is studied and the results of the two approaches are then compared.<p><p>The second block is devoted to the experimental study of the gas-liquid CO2 transfer to NaHCO3 and Na2CO3 aqueous solutions. An experimental set-up is developed and presented. CO2 is put in contact with NaHCO3 and Na2CO3 aqueous solutions in a transparent cell. The phenomena induced in liquid phase by the CO2 transfer are observed using a Mach-Zehnder interferometer.<p>The experimental results are compared to simulation results that are obtained using one of the one-dimensional model developed in the first block. From this comparison, it appears that a wrong estimation of some physico-chemical parameter values leads to significative differences between the experimentally observed quantities and those estimated by simulation of the model equations. Therefore, a parametric estimation method is developed in order to estimate those parameters numerical values from the experimental results. The found values are then discussed.<p><p>In the third block is presented a contribution to the NaHCO3 precipitation kinetic study in a stirred-tank crystallizer. This part of the work is realized in collaboration with Vanessa Gutierrez (Chemicals and Materials Department of ULB).<p>Three tools are developed :tables in Excel sheet to synthetize the experimental results, a set of simulations of the flow inside the crystallizer by Computational Fluid Dynamic (CFD) and a new method to extract the NaHCO3 precipitation kinetics from the experimental measurements. These three tools are combined to estimate the influences of the solid mass fraction and the flow on the NaHCO3 secondary nucleation rate.<p><p>Finally, the synthesis of all these results is realized. The final result is the development of a complete and operational mathematical model of BIR columns. This model is developed following the compartmental modeling approach, developed in the PhD thesis of Benoît Haut. This model synthetizes the three block of study realized in this work and the studies of Aurélie Larcy (Transfers, Interfaces and Processes Department of ULB) and those of Vanessa Gutierrez. The equations modeling the phenomena taking place in a BIR column are presented as the used method to solve these equations. The equations of the model are simulated and the results are discussed. The results are equally compared to experimental measurement realized on a BIR column. A reasonable agreement is observed.<p>At the end of this work, an operational model of a BIR column is thus developed. Although this model have to be optimized and validated, it can already be used to study the influences of the geometrical characteristics of the BIR columns and of the conditions applied to these columns on the behaviour of the model equation simulations and to identity tendencies. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

La mucoviscidose est la maladie génétique autosomique récessive létale la plus fréquente dans la population caucasienne. Le gène muté code pour la protéine CFTR (Cystic Fibrosis Transmembrane conductance Regulator). CFTR est un canal anionique localisé dans la membrane apicale des épithélia. Il permet notamment le transport d’ions chlorure (Cl-) et bicarbonates (HCO3-). La délétion de la phénylalanine en position 508 (F508del) de CFTR est la mutation la plus fréquente et entraîne un défaut d’adressage de CFTR à la membrane plasmique. L’atteinte respiratoire réalise une bronchopathie obstructive surinfectée qui détermine le pronostic vital de la maladie. Deux mécanismes délétères présents dès la période néonatale vont notamment contribuer à la destruction du tissu pulmonaire : une inflammation exacerbée et auto-entretenue, et une colonisation bactérienne chronique du mucus notamment à Pseudomonas aerugonisa et Staphylococcus aureus. Les mécanismes à l’origine de l'initiation de ce double processus demeurent inconnus. De plus en plus d'arguments plaident pour l'implication des ions HCO3-, donc du pH, dans l'initiation de l'atteinte pulmonaire de la mucoviscidose. En effet, le défaut de CFTR entraîne une diminution de leur sécrétion dans le liquide de surface bronchique (ou Airway Surface Liquid : ASL), ce qui conduit à un pH local anormalement bas. Les ions HCO3- jouent un rôle important dans la physiopathologie bronchique pulmonaire. En effet, ils régulent la rhéologie du mucus et sont impliqués dans l’activité des peptides antimicrobiens, principaux facteurs de la bactéricidie locale et dont l'activité est pH dépendante. Cela a été démontré dans un modèle porcin de mucoviscidose. Ainsi une altération du transport de HCO3- pourrait contribuer à l'hyperviscosité des sécrétions muqueuses, initier la colonisation bactérienne en diminuant le pouvoir bactéricide du liquide de surface respiratoire. Cette hypothèse est la base de mon projet visant à étudier le rôle du transport transépithélial des ions bicarbonates dans la bactéricidie au sein de l’épithélium respiratoire dans la mucoviscidose. La mesure du pH de l’ASL a nécessité la conception d’une enceinte à atmosphère contrôlée. Cet outil a permis la mise en évidence d’une acidité de l’ASL F508del en comparaison du Wild Type (WT), due à un défaut de sécrétion des ions HCO3- dans l’ASL, lui-même induit par une inhibition fonctionnelle du transporteur Cl-/HCO3- SLC26A4 ou pendrine majoritairement et du canal CFTR minoritairement. L’évaluation de la bactéricidie de l’ASL après infection au Staphylococcus aureus révèle une déficience de bactéricidie chez les cellules épithéliales F508del, reliée à l’activité anormale de la pendrine. L’investigation des capacités d’adhésion et d’invasion du Staphylococcus aureus dans nos modèles montre que le défaut de bactéricidie épithélial observé se restreint à l’ASL et incite à poursuivre les recherches sur le rôle du pH de l’ASL dans l’activité de ses peptides antimicrobiens, principale ligne de défense de l’immunité innée respiratoire. Notre travail de restauration du pH de l’ASL avant infection de l’épithélium respiratoire démontre d’ores et déjà l’impact significatif du pH de l’ASL dans la modulation de sa bactéricidie, où la restauration du pH est corrélée à une amélioration de la bactéricidie. Ce travail met en lumière le rôle crucial du pH de l’ASL dans l’appréhension de la physiopathologie de la maladie et sensibilise à de nouvelles voies thérapeutiques, basées sur une restauration du pH de l’ASL et/ou l’utilisation de peptides antimicrobiens pH-indépendant. / Cystic fibrosis (CF) is a lethal autosomal recessive disorder caused by mutations in the CF Transmembrane Conductance Regulator (CFTR) gene encoding for a cAMP-activated anionic channel, secreting mainly chloride (Cl-) and bicarbonate (HCO3-) at the apical surface of the epithelia. Most patients are homozygous for the p.PHe508del mutation (F508del). The main cause of morbidity and mortality is obstructive lung disease characterized by exacerbated inflammation and bacterial infection of the airway surface liquid (ASL), a thin layer coating the luminal face of the airway epithelium. ASL bacterial colonization begins from the first hours of life with evidence of Staphylococcus aureus in airway secretions pointing to impaired local defense. However, the defect responsible for this defective bacterial clearance is not clearly understood. It was proposed to be related to decreased mucociliary clearance and abnormal inflammatory responses, but recent studies also show the contribution of ASL in the reduced antimicrobial capacity of ASL in CF airways. An abnormally low ASL pH impairs mucin hydration and solubilization, resulting in hyperviscous mucus, which impedes muco-ciliary clearance. It also reduces the activity of antimicrobial peptides by modulating their native charges and the bactericidal activity of antibiotics. This was supported by studies in newborn CF pigs, which highlighted an abnormally low ASL pH, in association with a defective short-term S. aureus antimicrobial activity. Restoring normal pH in the ASL of CF pigs improved ability to eradicate the bacteria, showing that reduced ASL pH is central to disease pathogenesis. However, there is still controversy about the value of ASL pH in humans. Very recently, a study in young CF children, based on in vivo measurements, showed similar ASL pH values in children with CF to that in children without CF. The mechanisms underlying the ASL pH homeostasis and in particular the balance between HCO3- and proton (H+) secretion are still not known. Shah et al highlighted the role of persistent H+ secretion by ATP12A concomitant to a CFTR-mediated reduced bicarbonate transport, but recent work overexpressing ATP12A in respiratory cells failed to find any pH modification in physiological conditions. Most importantly, there is no clear understanding of the initial host response, when S. aureus bacteria land on the pristine surface of a newborn airway, with a prolonged time of contact and continuous reseeding from infected mucus plugs. This is however crucial to clarify pathogenesis of this early steps to counteract pro-infectious vicious circle and define optimal therapeutic strategy in newborns. We focused on human airways and hypothesized that S. aureus clearance during the first hours of infection was impaired in human airway CF ASL because of lowered ASL pH. To test this hypothesis, we designed bacterial infection experiments within human airway epithelium to mirror the onset of initial S. aureus infection. We then studied the relationship between local bacterial clearance and ASL pH regulation in WT and F508del homozygous human bronchial epithelial cells, with special emphasis on physiologically relevant HCO3- and H+ transporters.

Le photosystème II (PSII) est un complexe multi-protéique qui utilise l'énergie solaire pour oxyder l'eau et réduire des quinones. Le site catalytique d'oxydation de l'eau est localisé coté lumen du complexe, alors, que le site de réduction comprenant deux quinones (QA et QB) et un fer non-hémique est localisé sur le coté stromal du complexe membranaire. Dans cette thèse j'ai étudié les deux cotés accepteur et donneur d'électrons du PSII.QA•- et QB•- sont couplés magnétiquement au fer non-hémique donnant de faibles signaux RPE. Le fer non-hémique possède quatre ligands histidines et un ligand (bi)carbonate échangeable. Le formate peut échanger le ligand (bi)carbonate induisant un ralentissement dans le transfert d'électrons. Ici, je décris une modification du signal RPE de QB•- Fe2+ lorsque le formate est substitué au (bi)carbonate. J'ai aussi découvert un second signal RPE dû à la présence du formate à la place du (bi)carbonate lorsque QB est doublement réduit. De plus, j'ai trouvé que les signaux RPE natifs de QA•- Fe2+ et QB•- Fe2+ possèdent une signature intense encore jamais détectée. Tous les signaux RPE rapportés dans cette thèse devraient faciliter le titrage redox de QB par RPE. J'ai aussi observé que QB•- peut oxyder le fer non-hémique à l'obscurité en anaérobie. Cette observation implique qu'au moins dans une fraction des centres, le couple QB•-/QBH2 possède un potentiel redox plus haut que supposé. La quantification du nombre de centres où cette oxydation du fer se produit par le couple QB•-/QBH2 reste à faire. La réduction du PSII par le dithionite génère un signal modifié de QA•-Fe2+, un changement structural du PSII observé par électrophorèse. Cela peut indiquer la réduction d'un pont disulfure à l'intérieur du PSII. Concernant le site d’oxydation de l'eau, j'ai étudié la première étape de l'assemblage du site catalytique (Mn4Ca), en suivant l'oxydation du Mn2+ par RPE en bande X et haut champ. J'ai mis au point des conditions expérimentales permettant le piégeage du premier intermédiaire et j'ai aussi trouvé une incohérence avec des travaux publiés dans la littérature. J'ai aussi trouvé que le dithionite pouvait réduire le site catalytique Mn4Ca, en formant des états sur-réduits qui peuvent correspondre aux intermédiaires de l'assemblage du cluster Mn4Ca. / Photosystem II (PSII) uses light energy to oxidise water and reduce quinone. The water oxidation site is a Mn4Ca cluster located on the luminal side of the membrane protein complex, while the quinone reduction site is made up of two quinones (QA and QB) and a non-heme Fe2+ located on the stromal side of the membrane protein. In this thesis I worked on both oxidation and reduction functions of the enzyme. QA•- and QB•- are magnetically couple to the Fe2+ giving weak and complex EPR signals. The distorted octahedral Fe2+ has four histidines ligands and an exchangeable (bi)carbonate ligand. Formate can displace the exchangeable (bi)carbonate ligand, slowing electron transfer out of the PSII reaction centre. Here I report the formate-modified QB•- Fe2+ EPR signal, and this shows marked spectral changes and has a greatly enhanced intensity. I also discovered a second new EPR signal from formate-treated PSII that is attributed to formate-modified QA•- Fe2+ in the presence of a 2-electron reduced form of QB. In addition, I found that the native QA•- Fe2+ and QB•- Fe2+ EPR signals have a strong feature that had been previously missed because of overlapping signals (mainly the stable tyrosyl radical TyrD•). These previously unreported EPR signals should allow for the redox potential of this cofactor to be directly determined for the first time. I also observed that when QB•-Fe was formed; it was able to oxidise the iron slowly in the dark. This occurred in samples pumped to remove O2. This observation implies that at least in some centres, the QB•-/QBH2 couple has a higher potential then is often assumed and thus that the protein-bound semiquinone is thermodynamically less stable expected. It has yet to be determined if this represents a situation occurring in the majority of centres. Treatment of the system with dithionite generated a modified form of QA•-Fe2+ state and a change in the association of the proteins on gels. This indicates a redox induced modification of the protein, possibly structurally important cysteine bridge in PSII.On the water oxidation side of the enzyme, I studied the first step in the assembly of the Mn4Ca cluster looking at Mn2+ oxidation using kinetic EPR and high field EPR. Conditions were found for stabilising the first oxidised state and some discrepancies with the literature were observed. I also found that dithionite could be used to reduce the Mn4Ca, forming states that are formally equivalent to those that exist during the assembly of the enzyme.

Abstract: Sodium bicarbonate is one of the major chemical compound used worldwide. We have studied the mechanisms presiding the crystallization of this product in order to identify the kinetic parameters. To be assured of the relevancy of our experimental results, we developed new and accurate measurement techniques to follow the supersaturation and to characterize the crystal morphologies of NaHCO3 like density measurement and images analysis. The systematic study of the mechanisms and the kinetic parameters of the crystallization of NaHCO3 has been conducted by the use of three different types of crystallizers conceived and built at the Department of Industrial Chemistry of ULB : a fluidized bed crystallizer, a classic MSMPR crystallizer and a bubble column. By this choice, we were able to thoroughly investigate the intrinsic phenomena occurring in the crystallization of NaHCO3 from the ideal condition to the conditions close to the industry. A NaHCO3 solution is typically a three components equilibrium, NaHCO3, Na2CO3 and CO2, depending on temperature. Our developed method of density measurement allows to measure continuously the supersaturation, during the crystallization. This method permits to neglect complex side effects due to Na2CO3 or dissolved mineral impurities. Density measurements are quick, sensitive and reliable. We have shown that the growth of sodium bicarbonate is widely controlled by a reaction step at 45°C (< 200 µm). A diffusion step controlled growth occurs however for large crystals (>300-425µm) which consume much less material than the small ones. We have shown that the secondary nucleation of NaHCO3 is principally dominated by the surface nucleation. The shape of the crystals obtained experimentally is in agreement with the theory, and strongly related to the size of the crystals and to the presence of impurities. Based on experience of NaHCO3 crystallization without introduction of impurity, we have demonstrated that Ca2+ and Mg2+ suppress crystallization kinetics. In the end, we have taken a brief look at the precipitation of NaHCO3 by gaz-liquid reaction in a bubble column. By a comparative and a fundamental approach, our experimental studies lead us to improve our understanding and the operational parameters of the NaHCO3 industrial refining process. Key words: Industrial crystallization, Sodium bicarbonate, Density measurement, Fluidized bed, MSMPR, Bubble column, Crystal growth, Nucleation Résumé: Le bicarbonate de sodium (NaHCO3) est un produit chimique important sur le marché mondial. Nous avons étudier les mécanismes de la cristallisation de ce produit afin d'en déterminer les paramètres cinétiques. Afin de garantir l'analyse la plus objective de ces phénomènes, nous avons développé des techniques de mesures originales pour la connaissance de la sursaturation et pour la caractérisation des cristaux de NaHCO3 par densimétrie et par analyse d’images. L'étude systématique des cinétiques et des mécanismes de cristallisation du NaHCO3 a été réalisée au moyen de trois cristallisoirs de conception différente, développés et construits au laboratoire du Service de Chimie Industrielle de l'ULB: un cristallisoir à lit fluidisé, un cristallisoir à cuve agitée MSMPR et une colonne à bulles. Ce choix nous a permis d'approfondir notre connaissance des phénomènes intrinsèques de la cristallisation du NaHCO3 dans des conditions idéales et des conditions proches des procédés industriels. Une solution de NaHCO3 est un système à l’équilibre à trois composantes, NaHCO3, Na2CO3 et CO2 fonction de la température. La mise au point de la méthode densimétrique a permis la mesure de la sursaturation en NaHCO3 en continu. Cette méthode permet de s’affranchir des complications introduites par la présence de Na2CO3 et des impuretés inorganiques en solution. Les mesures de masse volumique sont rapides, précises et sensibles. Nous avons démontré que la croissance du bicarbonate de sodium est largement dominé par l'étape de réaction à 45°C (< 200 µm). L'étape de diffusion intervient cependant dans la croissance de grands cristaux (>300-425µm) qui ne sont toutefois pas les plus grands consommateurs de matière. Nous avons mis en évidence que le mécanisme de la germination secondaire du NaHCO3 est principalement une germination secondaire vraie. La forme des cristaux obtenus est parfaitement en accord avec la théorie et dépend étroitement de la taille des cristaux mais également de la présence d'impuretés. En se basant sur les expériences de cristallisation du NaHCO3 sans introduction d’impuretés, nous avons démontré les effets de ralentissement des cinétiques de cristallisation d'ions tels que Ca2+ et Mg2+ . Nous avons enfin brièvement abordé la précipitation du NaHCO3 par réaction gaz-liquide dans une colonne à bulles. Cette approche expérimentale, comparative et fondamentale a permis d'affiner notre compréhension et d’optimiser un procédé industriel de raffinage du bicarbonate de sodium. Mots clés: Cristallisation industrielle, Bicarbonate de sodium, Densimétrie, Lit fluidisé, MSMPR, Colonne à bulles, Croissance des cristaux, Germination

Forty-eight Holstein cows at Utah State Dairy Farm were blocked statistically according to date of calving, previous milk production, and numbers of lactation at parturition. The cattle were assigned randomly to one of four treatments within blocks. The four treatments included a base ration (control, treatment #1), base ration plus .8% of sodium bicarbonate (treatment #2), base ration plus .4% of magnesium oxide (treatment #3), and base ration plus both .8% of sodium bicarbonate and .4% of magnesium oxide (treatment #4). The research was conducted from February 1983 to November 1984. A formagraph was used to measure milk coagulation parameters and pH was determined. There was no significant difference in milk coagulation parameters or pH between the control and the buffer treatments. Milk parameters were significantly different in individual cow, week, and milk pH. Milk parameters did not appear to be dependent upon season. Curd firmness was significant in interaction of season and treatment. Significant variations in milk pH were observed in relation to week, season, and individual cow. Overall treatments, the clotting time, K20, and pH value increased each week, and A30 decreased each week. The milk parameters and pH in each treatment were significant between weeks except K20 and A30 in treatment #3, and A30 in treatment #2 (p>0.05). The clotting time and K20 were negatively correlated with firmness, and there was positive correlation between Ct and K20 as expected. Somatic cell count was positively correlated with clotting time, K20, and pH and negatively correlated with A30. Milk pH was the most significant and had positive correlation coefficient with clotting time and firming rate and negative correlation coefficient with curd firmness.

O presente trabalho teve como objetivo avaliar os efeitos de três diferentes aditivos (Levedura, Virginiamicina e Bicarbonato de sódio) na dieta de bovinos composta de 30% de silagem de milho e 70% de concentrado sobre alguns parâmetros do metabolismo ruminal (concentração de amônia, pH, protozoários ciliados), degradabilidade in situ da dieta e alguns parâmetros sanguíneos (pH, PCO2, PO2, TCO2, HCO3, Beefc, sO2 e lactato). Para tanto, quatro bovinos zebuínos, machos castrados, da raça Nelore, com cânulas ruminais e peso vivo médio de 295 Kg, foram utilizados em um experimento em quadrado latino 4 x 4 com 10 dias de adaptação e sete dias de colheita de amostras em cada período. Os animais foram alojados em galpão de alvenaria, com cochos e bebedouros individuais. No geral, houve uma diferença significativa no pH em todos os tratamentos nas primeiras 2 horas após a alimentação (P < 0,05), entretanto, não houve diferença entre os tratamentos nesse período. Já em relação aos parâmetros sanguíneos, o tratamento virginiamicina apresentou menor valor de pH em relação ao tratamento levedura (P < 0,10). No entanto, os tratamentos controle e bicarbonato de sódio não apresentaram diferença estatística (P < 0,10). Houve um aumento na concentração de oxigênio saturado (sO2) no tratamento levedura, enquanto no tratamento virginiamicina, o valor encontra se diminuído. Não houve diferença estatística entre os demais tratamentos (P > 0,05). Os demais parâmetros não apresentaram diferenças estatísticas (P > 0,05). Houve diferença significativa entre os tratamentos em todos os tempos. O tratamento com bicarbonato de sódio obteve maior concentração de protozoários, deferindo dos demais (P < 0,05). Os tratamentos levedura e virginiamicina, não diferiram entre si (P > 0,05). O tratamento controle apresentou a menor concentração de protozoários em relação aos demais tratamentos (P < 0,05). Não houve efeito significativo nos valores encontrados (P > 0,05) para amônia ruminal. Na degradabilidade, apenas o coeficiente de degradabilidade da matéria seca (CDMS) diferiu estatisticamente dos outros tratamentos (P < 0,05). / The present work had as objective evaluates the effects of three different addictive (Yeast, Virginiamycin and Bicarbonate of sodium) in the diet of bovine composed of 30% of corn silage and 70% of concentrated on some parameters of the metabolism ruminal (concentration of ammonia, pH, protozoa ciliated), degradability in situ of the diet and some sanguine parameters (pH, PCO2, PO2, TCO2, HCO3, Beefc, sO2 and lactato). For so much, four bovine zebu, castrated males, of the race Nelore, with stems ruminate and medium alive weight of 295 Kg, they were used in an experiment in Latin square 4 x 4 with 10 days of adaptation and seven days of crop of samples in each period. The animals were housed at masonry hangar. In the general, there was a significant difference in the pH in all of the treatments in the first 2 hours after the feeding (P < 0.05), however, there was not difference among the treatments in that period. Already in relation to the sanguine parameters, the treatment virginiamycin presented smaller pH value in relation to the treatment yeast (P < 0.10). However, the treatments control and bicarbonate of sodium didn\'t present statistical difference (P < 0.10). There was an increase in the concentration of oxygen saturated (sO2) in the treatment yeast, while in the treatment virginiamycin, the value finds if decreased. There was not statistical difference among the other treatments (P > 0.05). The other parameters didn\'t present statistical differences (P > 0.05). There was significant difference among the treatments in all of the times. The treatment with bicarbonate of sodium obtained larger concentration of protozoa, granting of the others (P < 0.05). The treatments yeast and virginiamycin didn\'t differ amongst themselves (P > 0.05). The treatment control presented to smallest concentration of protozoa in relation to the other treatments (P < 0.05). There was not significant effect in the found values (P > 0.05) for ammonia ruminal. In the degradability, just the coefficient of degradability of the matter dries (CDMS) differed of the other treatments (P < 0.05).

Uroguanilina (UGN) é um peptídeo normalmente sintetizado no intestino que modula o balanço de sódio através de ações renais. Investigamos os efeitos e os mecanismos de sinalização envolvidos na ação da UGN sobre a secreção de H+, em túbulos renais de ratos e em células LLC-PK1 (proximais) e MDCK-C11 (distais). Nos estudos in vivo foi utilizada a técnica de microperfusão estacionária, na qual medimos a secreção de H+ em túbulos proximais e distais de rins de rato, utilizando um microeletrodo sensível a H+. Nos estudos in vitro, para medir a atividade de NHE3 e H+-ATPase, utilizamos microscopia de fluorescência, usando BCECF como sonda sensível a pH. Nossos dados indicam que UGN inibe a secreção de hidrogênio em túbulos proximais e em células LLC-PK1 por um mecanismo dependente da inibição do permutador NHE3, envolvendo a ativação de PKG e PKA. Nosso estudo também sugere que UGN inibe a secreção de hidrogênio em túbulos distais de rato e em células MDCK-C11, envolvendo a inibição da atividade da H+-ATPase por um mecanismo dependente de PKG / Uroguanylin (UGN) is a peptide usually synthesized in the intestine that modulates sodium balance through actions on the kidney. We investigate the effects and signaling mechanisms involved in the UGN action on hydrogen secretion in rat renal tubules and in LLC-PK1 and MDCK-C11 cells. In the in vivo studies we used the stationary microperfusion method, measuring hydrogen secretion in proximal and distal tubules by a H+ sensitive microelectrode. In the in vitro studies, we used fluorescence microscopy to measure the activity of NHE3 and H+-ATPase, using BCECF as pH sensitive dye. Our data indicate that UGN inhibits the hydrogen secretion in proximal tubules and in LLC-PK1 cells by a mechanism dependent on the inhibition of NHE3, involving the activation of PKG and PKA. Our study also suggests that UGN inhibits hydrogen secretion in distal tubules and MDCK-C11 cells., and the inhibition of H+-ATPase by a mechanism dependent on PKG is involved in this distal effect of UGN.

A incidência da nefropatia por contraste tem aumentado simultaneamente ao aumento da utilização do uso de métodos radiológicos com fins diagnósticos e de intervenção terapêutica. Infelizmente, parcela significante dos profissionais da área da saúde desconhece a sua existência e mesmo aqueles que a identificam, algumas vezes, desconhecem os fatores de risco associados ao seu desenvolvimento. A incidência da nefropatia por contraste na população geral é baixa, porém se levarmos em conta os pacientes com fatores de risco como diabetes e doença renal prévia, esta incidência aumenta exponencialmente. Várias estratégias tem sido utilizadas na tentativa de minimizar os efeitos da nefropatia por contraste sobre os indivíduos expostos ao seu uso. Entre elas, citamos o uso de drogas vasodilatadoras, de bloqueadores dos canais de cálcio, de antioxidantes, de solução fisiológica a 0,9% e a 0,45%, de solução de bicarbonato de sódio a 1,3%, do uso de contraste de baixa osmolalidade e mesmo de contrates iso-osmolares. As estratégias que tem sido descritas como mais eficazes são a hidratação com solução fisiológica (0,9% ou 0,45%), uso de contraste de baixa osmolalidade ou isoosmolar e a infusão de bicarbonato de sódio. A N-acetilcisteína, que é uma substância antioxidante, apresentou efeito positivo nos primeiros trabalhos publicados, mas trabalhos posteriores e meta-análises mostraram inconsistência neste efeito de prevenção. O objetivo deste trabalho é revisar a literatura pertinente sobre prevenção de nefropatia do contraste e estudar, de forma inicial, a eficácia da hidratação a base de bicarbonato de sódio a 1,3% comparada à hidratação a base de cloreto de sódio a 0.9% na prevenção da nefrotoxicidade do contraste em pacientes de alto risco para o seu desenvolvimento. Para tanto, foram randomizados um total de 27 pacientes, sendo 48% do grupo bicarbonato. Todos os pacientes eram portadores de diabetes mellitus e/ou doença renal crônica prévia e diagnosticados com algum tipo de câncer. Nenhum dos 27 pacientes desenvolveu nefropatia do contraste, caracterizada como aumento de 0,5 mg/dL na creatinina basal e/ou aumento de 25% no valor da creatinina. A revisão de literatura sugere fortemente que o uso de bicarbonato de sódio é eficaz na prevenção de nefropatia por contraste. Em relação ao estudo randomizado e controlado que foi efetuado, o pequeno número de indivíduos incluídos não permite a obtenção de conclusões definitivas. No entanto, nos pacientes estudados, o bicarbonato de sódio foi tão eficaz quanto à hidratação a base de solução fisiológica na prevenção da nefropatia por contraste. / The incidence of contrast nephropathy has increased simultaneously to the augment of the use of diagnostic and interventional imaging procedures. Unfortunately, a large number of physicians do not know its existence and even when so do, sometimes do not do not know the risk factors associated to its development. The incidence of contrast nephropathy in the general population is low, but, if we consider only the patients with risk factors such as diabetes and chronic kidney disease, this incidence increases largely. Several strategies have been used in order to prevent contrast nephropathy. Among them, we include the use of vasodilators, calcium channel blockers, antioxidants, saline (0.9 or 0.45%), bicarbonate, low or iso osmolar iodinate contrast. The strategies that have proved better efficacy are saline hydration (0.9 or 0.45%), use of low or iso osmolar contrast and bicarbonate. N-acetylcysteine (an antioxidant agent), despite of the positive results obtained in the first trials, did not demonstrate the same efficacy subsequently. The aim of the current study was to review the pertinent literature and to assess the efficacy of sodium bicarbonate compared to saline in order to prevent contrast nephropathy. There were randomized 27 patients, 48% allocated in the bicarbonate group. All the patients were diabetic and/or had chronic kidney disease, and were diagnosed with some kind of cancer. No one of 27 patients developed contrast nephropathy (increase of 0.5 mg/dL in the baseline creatinine and/or a relative increase of 25% in baseline creatinine). The literature review strongly suggested that sodium bicarbonate use is valuable in then prevention of contrast nephropathy. In reference to the randomized study the small number of included patients did not allow that conclusive conclusions were obtained. However, in the group studied sodium bicarbonate demonstrated the same efficacy than saline in the prevention of contrast nephropathy.