Osmotic Water Transfer Research Articles

Theoretical and Experimental Study of Joint Osmotic and Electroosmotic Water Transfer through a Cation-Exchange Membrane.

Using the previously developed cell model of a charged membrane and the principles of linear thermodynamics of irreversible processes (the Onsager approach), exact and approximate (in the case of an ideally selective membrane) analytical formulae for calculating the osmotic and electroosmotic permeability of the membrane in aqueous solutions of 1:1 electrolyte at constant electric current density and concentration gradient were suggested. The formulae have been successfully verified by our own experimental data for the extrusion cation-exchange membrane MF-4SC p.29 in NaCl solution up to concentrations of 3 M. The contribution of electroosmotic and osmotic water fluxes to the total water transport through the mentioned individual perfluorinated ion-exchange membrane under conditions close to the process of electrodialysis concentrating was experimentally estimated. The cases of co- and counter-directed osmotic and electroosmotic water fluxes are studied. A good correspondence between theoretical and experimental results was obtained, which made it possible to determine the physicochemical parameters of the electromembrane system (the diffusion coefficients of individual ions and the coefficient of equilibrium distribution of electrolyte molecules in the membrane matrix, the characteristic exchange capacity of the cell model). The achieved results make it possible to fully characterize existing and promising types of ion-exchange membranes based on the developed cell model of a charged membrane.

Ion fluxes resolve organellar volume

Cell Biology Animal cells continuously sample the surrounding medium, a feature accentuated in immune cells. Sampling is accomplished by trapping external medium into membrane-bound vesicles or vacuoles. These structures are promptly resolved, thus avoiding accumulation of endomembranes and volume expansion. In a variety of cultured cells, Freeman et al. found that this resolution entails conversion of spherical vacuoles into thin tubules, a process that involves marked changes in surface-to-volume ratio (see the Perspective by King and Smythe). Shrinkage of membrane-bound structures is driven by ion fluxes and subsequent osmotic transfer of water. Shriveled vacuoles attract curvature-sensing proteins that promote the extension of fine tubules. Ion channels thereby control membrane remodeling, enabling receptor recycling and proper routing of cellular cargo. Science , this issue p. [301][1]; see also p. [246][2] [1]: /lookup/doi/10.1126/science.aaw9544 [2]: /lookup/doi/10.1126/science.aba3623

Lipid-gated monovalent ion fluxes regulate endocytic traffic and support immune surveillance

Despite ongoing (macro)pinocytosis of extracellular fluid, the volume of the endocytic pathway remains unchanged. To investigate the underlying mechanism, we used high-resolution video imaging to analyze the fate of macropinosomes formed by macrophages in vitro and in situ. Na+, the primary cationic osmolyte internalized, exited endocytic vacuoles via two-pore channels, accompanied by parallel efflux of Cl- and osmotically coupled water. The resulting shrinkage caused crenation of the membrane, which fostered recruitment of curvature-sensing proteins. These proteins stabilized tubules and promoted their elongation, driving vacuolar remodeling, receptor recycling, and resolution of the organelles. Failure to resolve internalized fluid impairs the tissue surveillance activity of resident macrophages. Thus, osmotically driven increases in the surface-to-volume ratio of endomembranes promote traffic between compartments and help to ensure tissue homeostasis.

Impedance and conductivity of bovine myocardium during freezing and thawing at slow rates - implications for cardiac cryo–ablation

Increasing impedance during freezing might be a valuable marker for guiding cardiac cryo-ablation. We provide model based insights on how decreasing temperature below the freezing point of tissue relates to the percentage of frozen water. Furthermore, we provide experimental data for comparing this percentage with the increase in impedance.Measurements were performed on a bovine tissue sample at frequencies between 5 and 80 kHz. Slow cooling and heating rates were applied to minimize temperature gradients in the myocardial sample and to allow accurate assessment of the freezing point. Computer simulation was applied to link impedance with temperature dependent conductivities. The osmotic virial equation was used to estimate the percentage of frozen water.Measurements identified the freezing point at −0.6 ∘C. At −5 ∘C, impedance rose by more than a factor of ten compared to that at the freezing point and the percentage of frozen water was estimated as being 89%. At −49 ∘C impedance had increased by up to three orders of magnitude and ice formation was most pronounced in the extracellular space.Progressive ice formation in tissue is reflected by a large increase in impedance, and impedance increases monotonically with the percentage of frozen water. Its analysis allows for experimental assessment of factors relevant to cell death. Solid ice contributes to the rupture of the micro-vasculature, while phase shifts reflect concentration differences between extra- and intracellular space driving osmotic water transfer across cell membranes.

Different magnesium release profiles from W/O/W emulsions based on crystallized oils

Water-in-oil-in-water (W/O/W) double emulsions based on crystallized oils were prepared and the release kinetics of magnesium ions from the internal to the external aqueous phase was investigated at T=4°C, for different crystallized lipophilic matrices. All the emulsions were formulated using the same surface-active species, namely polyglycerol polyricinoleate (oil-soluble) and sodium caseinate (water-soluble). The external aqueous phase was a lactose or glucose solution at approximately the same osmotic pressure as that of the inner droplets, in order to avoid osmotic water transfer phenomena. We investigated two types of crystallized lipophilic systems: one based on blends of cocoa butter and miglyol oil, exploring a solid fat content from 0 to 90% and the other system based on milk fat fractions for which the solid fat content varies between 54 and 86%. For double emulsions based on cocoa butter/miglyol oil, the rate of magnesium release was gradually lowered by increasing the % of fat crystals i.e. cocoa butter, in agreement with a diffusion/permeation mechanism. However for double emulsions based on milk fat fractions, the rate of magnesium release was independent of the % of fat crystals and remains the one at t=0. This difference in diffusion patterns, although the solid content is of the same order, suggests a different distribution of fat crystals within the double globules: a continuous fat network acting as a physical barrier for the diffusion of magnesium for double emulsions based on cocoa butter/miglyol oil and double globule/water interfacial distribution for milk fat fractions based double emulsions, through the formation of a crystalline shell allowing an effective protection of the double globules against diffusion of magnesium to the external aqueous phase.

Mitochondria–based biosensors with piezometric and RELS transduction for potassium uptake and release investigations

Dysfunctional mitochondria appear to be involved in many diseases through their role in respiration, reactive oxygen species generation, and energy production. To aid in the design of new biosensors based on mitochondria (MT), we have investigated the feasibility of detecting ion fluxes through the MT-membrane K+-ion channels using piezosensors with MTs immobilized either by hydrogen bonding or thin polypyrrole (PPy) binding film. We have demonstrated for the first time that the mitochondria-based piezosensors are able to detect ion fluxes and thus be utilized for drug development aimed at ion channel opener- or inhibitor-function. The quartz crystal resonator responding only to mass changes in the lower part of the MT film, penetrated by the acoustic wave, is able to detect a pronounced cationic dynamics in PPy-bonded MT piezosensors despite of the undoped-PPy preference for pure anion dynamics. The control experiments performed by resonance elastic light scattering (RELS) confirmed MT swelling/shrinking, ion dynamics, and osmotic water transfer in MTs, as well as the effects of exposure to a drug valinomycin at sub-nanomolar concentrations.

Interdroplet bilayer arrays in millifluidic droplet traps from 3D-printed moulds

In droplet microfluidics, aqueous droplets are typically separated by an oil phase to ensure containment of molecules in individual droplets of nano-to-picoliter volume. An interesting variation of this method involves bringing two phospholipid-coated droplets into contact to form a lipid bilayer in-between the droplets. These interdroplet bilayers, created by manual pipetting of microliter droplets, have proved advantageous for the study of membrane transport phenomena, including ion channel electrophysiology. In this study, we adapted the droplet microfluidics methodology to achieve automated formation of interdroplet lipid bilayer arrays. We developed a 'millifluidic' chip for microliter droplet generation and droplet packing, which is cast from a 3D-printed mould. Droplets of 0.7-6.0 μL volume were packed as homogeneous or heterogeneous linear arrays of 2-9 droplets that were stable for at least six hours. The interdroplet bilayers had an area of up to 0.56 mm(2), or an equivalent diameter of up to 850 μm, as determined from capacitance measurements. We observed osmotic water transfer over the bilayers as well as sequential bilayer lysis by the pore-forming toxin melittin. These millifluidic interdroplet bilayer arrays combine the ease of electrical and optical access of manually pipetted microdroplets with the automation and reproducibility of microfluidic technologies. Moreover, the 3D-printing based fabrication strategy enables the rapid implementation of alternative channel geometries, e.g. branched arrays, with a design-to-device time of just 24-48 hours.

Influence of the inner droplet fraction on the release rate profiles from multiple W/O/W emulsions

Water-in-oil-in-water (W/O/W) double emulsions were prepared and the kinetics of release of magnesium ions from the internal to the external water phase was investigated as a function of the inner droplet volume fraction, at constant temperature (T=25°C). All the emulsions were formulated using Miglyol as the oil phase and the same surface-active species, namely polyglycerol polyricinoleate (oil-soluble) and sodium caseinate (water-soluble). Also, the internal droplet and oil globule diameters were almost identical for all systems under study. The external aqueous phase was a lactose solution at approximately the same osmotic pressure as that of the inner droplets, in order to avoid osmotic water transfer phenomena. We probed two different initial configurations in terms of inner droplet composition: (i) “one-component” systems where all droplets were composed of the same MgCl2 solution, and (ii) a “two-component” systems, where droplets containing MgCl2 and lactose coexisted. In all cases, coalescence of the inner droplets on the oil globule surface was marginal so that magnesium leakage was mainly due to diffusion phenomena. The rate of magnesium release was lowered by increasing the inner droplet fraction, regardless of the initial configuration. Assuming that the transfer of the encapsulated species mainly occurs via thin liquid films, such evolution could reflect the increasing tortuosity of the diffusion pathways with the inner droplet fraction.

Electrodialysis of concentrated brine from RO plant to produce coarse salt and freshwater

Reverse osmosis (RO) process is the most popular seawater desalination technology to solve global water crisis. However, the effluent of concentrated brine from RO plant could induce severe damage to marine ecosystems, especially for closed continental areas. Electrodialysis (ED) as an excellent technology has been used to treat RO effluent. An electrodialyzer which consisted of five pieces of cation-exchange membranes (CEMs) and four pieces of anion-exchange membranes (AEMs) was used to treat concentrated brine of RO plant. The effect of operation parameters such as current density, operating mode, type of membranes and initial brine concentration was investigated to measure a Lab-scale device. The results indicate that water transportation phenomenon through ED process are mainly induced by electro-osmotic rather than osmotic water transfer due to concentration difference. The ED process of RO concentrated brine can produce both refresh water and highly concentrated brine (ca. 27.13% (m/v)) for producing coarse salt via further crystallization.

A description of a flat geometry direct osmotic concentrator to concentrate tomato juice at ambient temperature and low pressure

A novel membrane module was developed for the purpose of concentrating tomato juice by direct osmosis at ambient temperature and low pressure. This stainless steel module was in the shape of a flat configuration consisting of two parts of a square flange screwed together, with a piece of flat membrane between them. The configuration resulted in the formation of two chambers of special morphology which allowed the flow of tomato juice and osmotic medium in the two respective sides of the membrane and enabled the osmotic transfer of pure water from the juice to the osmotic medium side. By using this module at ambient temperature and low pressure (∼4 bar), with sodium chloride as the osmotic medium, fresh tomato juice was concentrated from 5.5°Brix to the level of approximately 16°Brix, and from 4.25 to 7.5°Brix. The levels of achieved concentrations meet the standards attained by two commercially available tomato concentrates with concentration ranges 7–9 and 10–14°Brix, known as PASSATA and PIZZA SAUCE, respectively. For re-concentration of the post-process diluted osmotic NaCl brines, electrodialysis is proposed as a viable alternative to the commonly used evaporative process. Electrodialysis is an established methodology in the chemical industry for concentrating brines up to the saturation and is far more economical than evaporization. In summary, the use of NaCl brines as osmotic media in a combined direct osmosis–electrodialysis process operated at ambient temperature and low pressure allows concentration of tomato juice to produce tomato concentrates of commercial interest.

Water transport study across commercial ion exchange membranes in the vanadium redox flow battery

The water transfer behaviour of Selemion CMV, AMV and DMV membranes (Asahi Glass, Japan) has been studied in the vanadium redox cell, as was the water transfer across Nafion 117 membrane (E.I. Du Pont, USA). The earlier water transport studies of a variety of commercial ion exchange membranes and non-ionic separators in the vanadium redox cell have shown that the net water transport through anion exchange membranes and non-ionic separators in the vanadium redox cell is from the positive half cell (+ve) to the negative half cell (−ve), while for cation exchange membranes the net water transport is in the opposite direction. In the present study, it was found that a significant amount of water is transferred across cation exchange membranes from the −ve vanadium half cell electrolyte to the +ve vanadium half cell electrolyte by the hydration shells of V 2+ and V 3+ ions which carry a large amount of water and can easily permeate through cation exchange membranes due to their relatively high charge numbers. The net amount of water of hydration which is transferred across anion exchange membranes from the −ve half cell electrolyte, however, is almost equal to the net amount of water of hydration which is transferred from the +ve half cell electrolyte. Thus, the net amount of water which is transferred across anion exchange membranes is in the same direction as the osmotic water transfer.

Stabilizing Effects of Some Amino Acids on Membranes Of Rabbit Erythrocytes Perturbed by Chlorpromazine

Hemolysis experiments indicated that glycine (20 mM) remarkably suppressed the chlorpromazine (CPZ)-induced osmotic permeability enhancing effect in rabbit erythrocytes. Lysine and aspartic acid also showed a similar protecting effect at the same concentration. Thus, the acid-base properties of amino acids were not a determining factor in stabilizing the cell membranes perturbed by CPZ. These results suggest that amino acids stabilize the membranes of the erythrocytes by inhibiting the osmotic water transfer from the outside to the inside of the cells. The kinetic studies in isotonic suspensions of erythrocytes indicated that glycine decreased the hemolytic activity of CPZ, and it was suggested that glycine molecules possibly inhibited penetration of CPZ into the cell membranes. The data also showed that the membrane stabilizing action of glycine was not affected by the dissociation of CPZ molecules. The degree of dissociation of glycine molecules was not found to be related to the degree of the protection. The FT-IR spectroscopy data indicated that glycine made the acyl chains of the liposome perturbed by CPZ more orderly.

Use of Electrodialysis to Remove Heavy Metals from Water

Abstract The removal of heavy metals from water by using electrodialysis is discussed. Parameters studied include current efficiency, stack resistance, and osmotic water transfer. Four single-electrolyte systems are investigated: CdCl2 and CdSO4 are used as representative heavy metal salts; NaCl and CaCl2 are studied in order to enhance the understanding of physical electrodialytic processes in general and to provide a basis of comparison. The variables of electrolyte type, electrolyte concentration, pH, temperature, and elapsed time of membrane usage are examined. Results indicate that the purification of cadmium-laden waters can be achieved while maintaining high current efficiencies and reasonable stack resistances. The osmotic water transfers (in units of liter/mole) of the above cadmium salts are small enough to allow a high percentage of a wastewater stream to be reclaimed as purified water. but are higher than the water transfers of NaCl and CaCl2 due to increased hydration effects.

Equilibration, distribution, and elimination of a single dose of intravenous ethanol in dogs with intact renal function or anuria.

We infused 11 mmol/kg of intravenous ethanol into dogs with either intact renal function (n = 5) or ureteral ligation (n = 7), and studied by frequent blood sampling and by urine collection the time and mode of ethanol equilibration, the elimination parameters, and the comparison of observed equilibrated plasma ethanol levels to levels predicted either by linear or by nonlinear kinetics. Equilibration time was 25 min or less, renal fraction of elimination was less than 5% of total elimination, and both linear (elimination rate) and nonlinear (Vmax and Km) elimination parameters were not different between dogs with intact renal function and dogs with anuria. Serum sodium concentration did not change throughout the experiments, eliminating the hypothesis that acute ethanol load creates clinically significant temporary osmotic water transfer from the intracellular into the extracellular compartment. Distribution volumes of ethanol from linear kinetics were slightly, but not statistically, greater than volumes from nonlinear kinetics. Equilibrated plasma ethanol levels predicted by linear kinetics agreed closely with observed levels greater than 4 mmol/liter, but underestimated observed levels less than 4 mmol/liter. Equilibrated plasma ethanol levels predicted by nonlinear kinetics agreed with observed levels throughout the range of observed concentrations. The use of linear kinetics to predict blood ethanol levels should be limited to the pseudolinear portion of the blood alcohol curve.

Calcium/phospholipid-dependent protein kinase and its relationship to antidiuretic hormone in toad urinary bladder epithelium

The hydro-osmotic response of the toad urinary bladder to antidiuretic hormone (ADH) and cyclic AMP was inhibited by phorbol myristate acetate (PMA) and 4β- phorbol dideconate (4β-PDD), activators of protein kinase C (PKC). The inactive epimer of 4β-PDD, 4α-PDD, had no effect on the ADH response. The osmotic transfer of water in the absence of ADH was unaffected by PMA. PKC activity, localized in the soluble fraction of isolated toad bladder cells, was activated by PMA. ADH initially inhibited and subsequently stimulated 32Pi incorporation into phosphatidic acid (PA) and phosphatidylinositol (PI). Carbachol, which inhibits ADH-induced water flow, also stimulated 32P incorporation into PA and PI. It is suggested that phosphoinositide breakdown to diacylglycerol may activate PKC which functions to attenuate the hormone-mediated permeability response.

An apparatus for the concentration of large volumes of dilute protein solutions to a predetermined volume.

An apparatus was designed and manufactured that can be used for the concentration of large quantities of dilute protein solutions to a predetermined volume. The method is based on the osmotic transfer of water to a concentrated hydrophilic polymer (poly ethylene glycol, PEG) through a protein-stopping dialysis membrane and is a refinement of a method previously reported by van Oss. The apparatus is made of perspex. Concentration takes place through a commercially available dialysis tube and is aided by a 40% polyethylene glycol solution. Large volumes (5l) of dilute protein solution could be reduced to 50 ml at a rate of 30 ml per hour with no significant loss in biological activity.

Acid-base-induced changes in the distribution of water between plasma and erythrocytes, as measured with a sodium-ion-selective electrode.

aNa+ measured in whole blood changes with the pH of plasma, and the effect depends on the erythrocyte volume fraction (phi E). The relative change in aNa+ with pH, dlnaNa+/dpH, was -0.01 at phi E = 0 and -0.11 at phi E = 0.76. The observations agreed with the combined predicted effects of changes in phi E, in concentration of the NaHCO3 complex, and in liquid-junction potential. The pH-induced osmotic transfer of water between plasma and erythrocytes will affect the concentration of all components confined to plasma. Although the clinical importance of this may be limited, blood samples for research should either be dealt with immediately or stored anaerobically at 4 degrees C until separation, to avoid bias.

X-ray microanalysis of the filter chamber of the cicada, Cyclochila australasiae Don. A water-shunting epithelial complex.

X-ray microanalysis of frozen-hydrated specimens of the cicada filter chamber shows that there are concentration changes in K+ and Cl- in the various compartments of the filter chamber from feeding to non-feeding states. These changes are consistent with an osmotic transfer of water between the anterior midgut and the posterior midgut and Malpighian tubules. K+ and Cl- account for a large proportion of the osmotically active solutes in these compartments, and it is suggested that the osmotic gradients are generated by secretion of K+ and Cl- into the posterior midgut and Malpighian tubule lumina. Analysis of freeze-substituted sections of filter chamber supports the analysis of frozen-hydrated specimens and indicates that Na+ may also be secreted into the posterior midgut and the Malpighian tubules. The system functions as a water-shunting complex.

Role of calcium and prostaglandins in the antidiuretic hormone response: Effect of ionophore A23187

The calcium ionophore A23187 (IP) inhibited the antidiuretic hormone (ADH)-stimulated hydro-osmotic response in toad urinary bladder but had no effect on the osmotic transfer of water in the absence of hormone. Extracellular calcium was necessary for this effect at lower but not at higher IP concentrations. The hydro-osmotic response to exogenous cyclic AMP was unaltered by IP, but the same response produced by inhibition of phosphodiesterase was reduced significantly. Cyclic AMP concentrations in isolated toad bladder epithelial cells were reduced by 50% with IP or exogenous prostaglandin E 2 (PGE 2). Indomethacin, a prostaglandin synthesis inhibitor, prevented the inhibitory actions of the IP on the ADH-mediated response. Collectively, these observations suggest a key role for cellular calcium in modulating the actions of antidiuretic hormone and are consistent with the hypothesis that the ionophore, through increasing intracellular calcium, stimulates the synthesis of prostaglandins which have a negative feedback on adenylcyclase. This effect would terminate the action of the hormone.

EFFECTS OF CADMIUM ON THE HYDRO-OSMOTIC AND NATRIFERIC RESPONSES OF THE TOAD BLADDER TO VASOPRESSIN

Cadmium, 10(-3) mol/l on the mucosal or 10(-5) mol/l on the serosal side of the toad urinary bladder, inhibits the hydro-osmotic effect of vasopressin. This inhibition is irreversible. The osmotic transfer of water in the absence of vasopressin was unaffected by the presence of the Cd2+. The hydro-osmotic response to cyclic AMP was also reduced by the Cd2+, but the response due to hypertonicity of the serosal bathing solution was unaffected. The short-circuit current (reflecting active transmural Na+ transport) was inhibited by 10(-3) mol Cd2+/l on the serosa, but was increased by 10(-3) mol/l at the mucosa or 10(-4) mol/l at the serosa. The natriferic response of the bladder to vasopressin was unaffected when Cd2+ was present under conditions that inhibited the hydro-osmotic response, further emphasizing that separate effector mechamisms may be involved for each effect.