Transport d'une solution saline en cellule de Hele-Shaw - Expériences et simulations numériques

Rapporteurs : HULIN J.P., ACKERER P. Examinateurs : ROYER P. Président : PANFILOV M.To study the spatio-temporal evolution of a miscible and non-reactive contaminant into a saturated porous media, a laboratory model (a transparent Hele-Shaw cell) was developed. The carrying out of the experimental set-up, the plates are made of optical glass, allowed to elaborate a global and non-intrusive method to measure concentration in the mixing zone. This method is based on light absorption properties by dye marking injected solution. The analogy between a Hele-Shaw cell and a porous medium is derived from the fact that the flow velocity averaged between the two plates is described by Darcy's law. Moreover, the averaged tracer transport is described by a dispersion tensor (Taylor dispersion). For a heterogeneous fluid (e.g.: density or dynamic viscosity contrasts), the conditions of analogy are obtained by an analytical approach using asymptotic development and homogenization to take into account the density and dynamic viscosity variation according to the concentration. A new structure of the dispersion tensor is obtained. According to flow rate and salt mass fraction of the injected solution, qualitatively reproducible results show that the plume propagates with a finger or two fingers shape. An empirical criterion, based on the ratio between gravitational velocity and that at the injection, is formulated to predict the type of propagation. Simulations, carried out with a numerical code developed at the laboratory and including the new structure of the dispersion tensor, allowed to: (i) to reproduce experimental results obtained for homogeneous and heterogeneous media and (ii) to analyze the influences of the diffusion, the injection geometry or the dispersion regime type on the solute numerical distributions.Afin d'étudier l'évolution spatio-temporelle d'un polluant miscible à l'eau et non réactif dans un milieu poreux saturé, un modèle de laboratoire (une cellule de Hele-Shaw transparente) a été développé. La conception de ce dispositif, les plaques sont réalisées en verre optique, a permis de mettre au point une méthode globale et non intrusive de mesure de la concentration dans la zone de mélange. Cette méthode est basée sur les propriétés d'absorption de la lumière par un colorant marquant la solution injectée. L'analogie entre une cellule de Hele-Shaw et un milieu poreux est basée sur la possibilité d'exprimer la vitesse moyenne de l'écoulement entre les deux plaques par la loi de Darcy. En outre, le transport moyen d'un traceur peut être décrit avec un tenseur de dispersion (dispersion de Taylor). Dans le cas d'un fluide hétérogène (e.g. : contrastes de masse volumique ou de viscosité), les conditions d'analogie sont obtenues par une approche analytique de type développement asymptotique et homogénéisation pour prendre en compte la variation de la masse volumique et de la viscosité dynamique en fonction de la concentration. Une nouvelle forme du tenseur de dispersion est établie. Suivant le débit volumique et la fraction massique en sel de la solution injectée dans le milieu homogène, des expériences qualitativement reproductibles montrent que le panache se propage sous la forme d'un ou de deux doigts. Un critère empirique, basé sur le rapport entre la vitesse gravitationnelle et celle à l'injection, est formulé pour prédire le type de propagation. Les simulations, réalisées avec un code numérique développé au laboratoire et incluant la nouvelle forme du tenseur de dispersion, permettent : (i) de reproduire de manière satisfaisante les résultats expérimentaux obtenus en milieu homogène et hétérogène et (ii) d'analyser les influences de la diffusion, de la géométrie de l'injection et du type de régime de dispersion sur les distributions numériques du soluté

Transport d'une solution saline en cellule de Hele-Shaw (expériences et simulations numériques)

NANCY/VANDOEUVRE-INPL (545472102) / SudocSudocFranceF

Ocular Clocks: Adapting Mechanisms for Eye Functions and Health

International audienc

Sodium bicarbonate cotransporter NBCe2 gene variants increase sodium and bicarbonate transport in human renal proximal tubule cells.

RATIONALE: Salt sensitivity of blood pressure affects \u3e30% of the hypertensive and \u3e15% of the normotensive population. Variants of the electrogenic sodium bicarbonate cotransporter NBCe2 gene, SLC4A5, are associated with increased blood pressure in several ethnic groups. SLC4A5 variants are also highly associated with salt sensitivity, independent of hypertension. However, little is known about how NBCe2 contributes to salt sensitivity, although NBCe2 regulates renal tubular sodium bicarbonate transport. We hypothesized that SLC4A5 rs10177833 and rs7571842 increase NBCe2 expression and human renal proximal tubule cell (hRPTC) sodium transport and may be a cause of salt sensitivity of blood pressure. OBJECTIVE: To characterize the hRPTC ion transport of wild-type (WT) and homozygous variants (HV) of SLC4A5. METHODS AND RESULTS: The expressions of NBCe2 mRNA and protein were not different between hRPTCs carrying WT or HV SLC4A5 before or after dopaminergic or angiotensin (II and III) stimulation. However, luminal to basolateral sodium transport, NHE3 protein, and Cl-/HCO3- exchanger activity in hRPTCs were higher in HV than WT SLC4A5. Increasing intracellular sodium enhanced the apical location of NBCe2 in HV hRPTCs (4.24±0.35% to 11.06±1.72% (P CONCLUSION: NBCe2 activity is stimulated by an increase in intracellular sodium and is hyper-responsive in hRPTCs carrying HV SLC4A5 rs7571842 through an aberrant HNF4A-mediated mechanism

Sodium bicarbonate cotransporter NBCe2 gene variants increase sodium and bicarbonate transport in human renal proximal tubule cells.

RATIONALE:Salt sensitivity of blood pressure affects >30% of the hypertensive and >15% of the normotensive population. Variants of the electrogenic sodium bicarbonate cotransporter NBCe2 gene, SLC4A5, are associated with increased blood pressure in several ethnic groups. SLC4A5 variants are also highly associated with salt sensitivity, independent of hypertension. However, little is known about how NBCe2 contributes to salt sensitivity, although NBCe2 regulates renal tubular sodium bicarbonate transport. We hypothesized that SLC4A5 rs10177833 and rs7571842 increase NBCe2 expression and human renal proximal tubule cell (hRPTC) sodium transport and may be a cause of salt sensitivity of blood pressure. OBJECTIVE:To characterize the hRPTC ion transport of wild-type (WT) and homozygous variants (HV) of SLC4A5. METHODS AND RESULTS:The expressions of NBCe2 mRNA and protein were not different between hRPTCs carrying WT or HV SLC4A5 before or after dopaminergic or angiotensin (II and III) stimulation. However, luminal to basolateral sodium transport, NHE3 protein, and Cl-/HCO3- exchanger activity in hRPTCs were higher in HV than WT SLC4A5. Increasing intracellular sodium enhanced the apical location of NBCe2 in HV hRPTCs (4.24±0.35% to 11.06±1.72% (P<0.05, N = 3, 2-way ANOVA, Holm-Sidak test)) as determined by Total Internal Reflection Fluorescence Microscopy (TIRFM). In hRPTCs isolated from kidney tissue, increasing intracellular sodium enhanced bicarbonate-dependent pH recovery rate and increased NBCe2 mRNA and protein expressions to a greater extent in HV than WT SLC4A5 (+38.00±6.23% vs HV normal salt (P<0.01, N = 4, 2-way ANOVA, Holm-Sidak test)). In hRPTCs isolated from freshly voided urine, bicarbonate-dependent pH recovery was also faster in those from salt-sensitive and carriers of HV SLC4A5 than from salt-resistant and carriers of WT SLC4A5. The faster NBCe2-specific bicarbonate-dependent pH recovery rate in HV SCL4A5 was normalized by SLC4A5- but not SLC4A4-shRNA. The binding of purified hepatocyte nuclear factor type 4A (HNF4A) to DNA was increased in hRPTCs carrying HV SLC4A5 rs7571842 but not rs10177833. The faster NBCe2-specific bicarbonate-dependent pH recovery rate in HV SCL4A5 was abolished by HNF4A antagonists. CONCLUSION:NBCe2 activity is stimulated by an increase in intracellular sodium and is hyper-responsive in hRPTCs carrying HV SLC4A5 rs7571842 through an aberrant HNF4A-mediated mechanism

Mastering the Shape and Composition of Dendronized Iron Oxide Nanoparticles To Tailor Magnetic Resonance Imaging and Hyperthermia

The current challenge in the field of nano-medicine is the design of multifunctional nano-objects effective both for the diagnosis and treatment of diseases. Here, dendronized FeO1-x@Fe3-xO4 nanoparticles with spherical, cubic, and octopode shapes and oxidized Fe3-xO4 nanocubes have been synthesized and structurally and magnetically characterized. Strong exchange bias properties are highlighted in core shell nanoparticles (NPs) due to magnetic interactions between their antiferromagnetic core and ferrimagnetic shell. Both in vitro relaxivity measurements and nuclear magnetic resonance (NMR) distribution profiles have confirmed the very good in vitro magnetic resonance imaging (Mm) properties of core shell and cubic shape NPs, especially at low concentration. This might be related to the supplementary anisotropy introduced by the exchange bias properties and the cubic shape. The high heating values of core shell NPs and oxidized nanocubes at low concentration are attributed to dipolar interactions inducing different clustering states, as a function of concentration. In vivo MRI studies have also evidenced a clustering effect at the injection point, depending on the concentration, and confirmed the very good in vivo MRI properties of core shell NPs and oxidized nanocubes in particular at low concentration. These results show that these core shell and cubic shape dendronized nano-objects are very suitable to combine MRI and hyperthermia properties at low injected doses

Models of ion transport in hRPTCs.

<p>This is a model of the hRPTC with the apical (brush border, facing the lumen) (left hand side) and the basolateral side (right hand side). The principal ion transporters and some of the receptors that regulate them are shown. Starting at 11 o’clock in blue is shown the classic pathway for transporting bicarbonate (HCO₃^-) into the cell. Filtered NaHCO₃ dissociates into Na⁺ and HCO₃. HCO₃^- in the luminal fluid and H⁺ secreted into the lumen form H₂CO₃. Carbonic anhydrase type 4 (CA IV) in the luminal membrane catalyzes the conversion of H₂CO₃ to H₂O and CO₂.CO₂ diffuses inside the hRPTC where intracellular carbonic anhydrase type 2 (CA II) catalyzes the conversion of CO₂ and H₂O into H₂CO₃ which then dissociates into HCO₃^- and H⁺. At 9 o’clock is NHE3 which exchanges one Na⁺ from the lumen with one H⁺ inside the hRPTC. At 7 o’clock HCO₃^- Cl^- exchanger (PAT1) is depicted which exchanges luminal Cl^- with cytoplasmic HCO₃^-. At 3 o’clock is depicted NBCe1 at the basolateral membrane which electrogenically transports 2–3 Na⁺ and one HCO₃^- into the basolateral space. At 4 o’clock is Na⁺, K⁺/ATPase which pumps 3 Na⁺ out of the cell into the blood stream and pumps in 2 K⁺ inside the cell The topic of this manuscript deals with NBCe2, drawn at 8 o’clock. Under a normal sodium load it plays a minor role in Na⁺ and HCO₃^- transport into the hRPTC. There are various plasma membrane receptors that regulate some of these transporters/ exchanger/pumps. The dopamine-1 receptor (D₁R) (ten o’clock) when stimulated with dopamine (green box) inhibits (red lines) both NHE3 and Na⁺, K⁺/ATPase (without the red line, for simplicity) activities resulting in reduced Na⁺ reabsorption and increased Na⁺ excretion. The AT₁R (5 o’clock) increases Na⁺, K⁺/ATPase activity (green arrow) resulting in increased Na⁺ reabsorption. An increase in intracellular Na⁺ increases Na⁺, K⁺/ATPase activity (5 o’clock) that is abetted by AT₁R (green arrow) resulting in increased Na⁺ transport from inside the cell to the basolateral space. The D₁R and AT₁R oppose each other. The D₁R inhibits the AT₁R, resulting in reduced Na⁺ transport. We showed that NBCe2 is not affected by stimulation of the D₁R or AT₁R. Under basal conditions, NBCe1 is more active than NBCe2 (depicted as relatively larger directional transport arrows).</p

NBCe1 protein expression regulation by D₁-like (D₁R and D₅R) dopamine receptor agonist in hRPTCs carrying wild-type (WT) <i>SLC4A5</i>.

<p>NBCe1 protein expression is decreased following an increase in intracellular sodium (↑Na⁺) (10 μmol monensin/L, 24 h) (N = 4, *P<0.001 vs VEH, one-way ANOVA, Tukey’s test) in WT <i>SLC4A5</i> hRPTC. The combination of monensin (↑Na⁺) and D₁R/D₅R agonist SKF38393 (SKF, 10 μmol/L, 24 h) further decreases NBCe1 protein (N = 4, **P<0.05 vs monensin (↑Na⁺), ^#P<0.001 vs SKF, one-way ANOVA, Tukey’s test) that is blocked by the D₁-like receptor antagonist LE300 (10 μmol/l, 24 h), which by itself has no effect. NBCe1 protein is not affected by SKF or LE300 in the absence of monensin.</p