Partial Osmotic Pressure Research Articles

Partial osmotic pressures of ions in electrolyte solutions and the Gibbs-Guggenheim uncertainty principle.

The concept of the partial osmotic pressure of ions in an electrolyte solution is critically examined. In principle these can be defined by introducing a solvent-permeable wall and measuring the force per unit area which can certainly be attributed to individual ions. Here I demonstrate that although the total wall force balances the bulk osmotic pressure as required by mechanical equilibrium, the individual partial osmotic pressures are extrathermodynamic quantities dependent on the electrical structure at the wall, and as such they resemble attempts to define individual ion activity coefficients. The limiting case where the wall is a barrier to only one species of ion is also considered, and with ions on both sides the classic Gibbs-Donnan membrane equilibrium is recovered, thus providing a unifying treatment. The analysis can be extended to illustrate how the electrical state of the bulk is affected by the nature of the walls and the container handling history, thus supporting the "Gibbs-Guggenheim uncertainty principle," namely the notion that the electrical state is unmeasurable and usually accidentally determined. Since this uncertainty is conferred also onto individual ion activities, it has implications for the current (2002) IUPAC definition of pH.

Pre-sowing magnetic field- induced changes in water relations and lipid peroxidation in cucumber under salinity stress

Overcoming salinity problems through increasing plant tolerance is a substantial strategy to increase crop production. A pot experiment was carried out to investigate the effect of salinity stress, pre-sowing magnetic fields and their combination on cucumber growth, water relations and lipid peroxidation. Seawater salinity (10%) enormously reduced the plant growth, relative water content (RWC), transpiration rate and water use efficiency (WUE), and increased partial osmotic pressure (POP), lipids peroxidation and membrane injury index. Root/shoot ratio was not affected by the salinity stress.Pre-sowing treatment with 50 mT (for 30 s or 30 min) and 100 mT (30 min) magnetic field enhanced plant growth, root/shoot ratio, RWC, transpiration rate and WUE under control and stress conditions in relation with the un-treated plants. These treatments appeared to reduce lipid peroxidation and membrane injury in cucumber under salinity stress. The effect of these magnetic treatments on POP was not regular. The combination treatment of those magnetic fields and salinity reduced the stress intensity index (SII) by about 25% in relation with salinity alone. Conversely, the application of 200 mT magnetic field for 30 min adversely affected the plant growth and water relations, and increased the SII, lipid peroxidation and membrane injury in cucumber under salinity stress. On many occasions, the effects of 100 mT for 30 min and 200 mT for 30 s were not significant.

Mucus Hyperconcentration as a Unifying Aspect of the Chronic Bronchitic Phenotype.

Abnormalities in mucus production and qualitative properties such as mucus hydration are central to the pathophysiology of airway disease including cystic fibrosis, asthma, and chronic bronchitis. In vitro air-liquid interface epithelial cell cultures demonstrate direct relationships between mucociliary transport, periciliary liquid (PCL) height, and mucus concentration (expressed as percent solids or partial osmotic pressure). In health, the osmotic modulus/pressure of the PCL exceeds that of the mucus layer, resulting in efficient, low-friction movement of mucus. In disease, through multiple mechanisms, the osmotic pressure of the mucus begins to exceed basal PCL values, resulting in compression of the cilia and slowing of mucus transport. The in vivo data in both cystic fibrosis and chronic bronchitis parallel in vitro data demonstrating that when mucus osmotic pressure is increased, mucociliary clearance is decreased. In chronic bronchitis, there is a direct correlation between FEV1 and percent solids of mucus, demonstrating a strong relationship between disease progression and mucus abnormalities. Animal models, based mechanistically on raised sodium absorption (and therefore water absorption) from airway surfaces, mimic the pathophysiology of chronic obstructive pulmonary disease. Collectively, these data suggest the importance of mucus concentration in the pathogenesis of airway disease. It is important to understand the precise mechanisms that result in mucus hyperconcentration, for example, mucin overproduction versus abnormal regulation of ion/water transport, which may be unique to and characteristic of each disease phenotype. The measurement of mucus concentration may be a simple method to diagnose chronic bronchitis, monitor its progression, and serve as a biomarker for development of new therapies.

The Relationship of Mucus Concentration (Hydration) to Mucus Osmotic Pressure and Transport in Chronic Bronchitis.

Chronic bronchitis (CB) is characterized by persistent cough and sputum production. Studies were performed to test whether mucus hyperconcentration and increased partial osmotic pressure, in part caused by abnormal purine nucleotide regulation of ion transport, contribute to the pathogenesis of CB. We tested the hypothesis that CB is characterized by mucus hyperconcentration, increased mucus partial osmotic pressures, and reduced mucus clearance. We measured in subjects with CB as compared with normal and asymptomatic smoking control subjects indices of mucus concentration (hydration; i.e., percentage solids) and sputum adenine nucleotide/nucleoside concentrations. In addition, sputum partial osmotic pressures and mucus transport rates were measured in subjects with CB. CB secretions were hyperconcentrated as indexed by an increase in percentage solids and total mucins, in part reflecting decreased extracellular nucleotide/nucleoside concentrations. CB mucus generated concentration-dependent increases in partial osmotic pressures into ranges predicted to reduce mucus transport. Mucociliary clearance (MCC) in subjects with CB was negatively correlated with mucus concentration (percentage solids). As a test of relationships between mucus concentration and disease, mucus concentrations and MCC were compared with FEV1, and both were significantly correlated. Abnormal regulation of airway surface hydration may slow MCC in CB and contribute to disease pathogenesis.

Cystic fibrosis airway secretions exhibit mucin hyperconcentration and increased osmotic pressure.

The pathogenesis of mucoinfective lung disease in cystic fibrosis (CF) patients likely involves poor mucus clearance. A recent model of mucus clearance predicts that mucus flow depends on the relative mucin concentration of the mucus layer compared with that of the periciliary layer; however, mucin concentrations have been difficult to measure in CF secretions. Here, we have shown that the concentration of mucin in CF sputum is low when measured by immunologically based techniques, and mass spectrometric analyses of CF mucins revealed mucin cleavage at antibody recognition sites. Using physical size exclusion chromatography/differential refractometry (SEC/dRI) techniques, we determined that mucin concentrations in CF secretions were higher than those in normal secretions. Measurements of partial osmotic pressures revealed that the partial osmotic pressure of CF sputum and the retained mucus in excised CF lungs were substantially greater than the partial osmotic pressure of normal secretions. Our data reveal that mucin concentration cannot be accurately measured immunologically in proteolytically active CF secretions; mucins are hyperconcentrated in CF secretions; and CF secretion osmotic pressures predict mucus layer-dependent osmotic compression of the periciliary liquid layer in CF lungs. Consequently, mucin hypersecretion likely produces mucus stasis, which contributes to key infectious and inflammatory components of CF lung disease.

Tolerance and avoidance responses to salinity and water stresses in Calotropis procera and Suaeda aegyptiaca

This study was designed to evaluate the response of 2 wild shrubs, Calotropis procera and Suaeda aegyptiaca, to salinity (100% seawater), drought, and waterlogging stresses. The 90-day-old plants were subjected to the stress treatments for 3 weeks, and growth and some physiological parameters were evaluated. The total plant dry mass of C. procera plants was reduced by 40%, whereas S. aegyptiaca was not significantly affected by salinity stress. Water deficit and waterlogging stresses significantly reduced the total dry mass of both species. Under all conditions, the root/shoot ratio in C. procera was 3-fold higher than in S. aegyptiaca. All applied stresses markedly increased leaf shedding in C. procera plants only. These plants appeared to have a higher salinity and waterlogging stress intensity index as manifested by chlorophyll levels lower than those in S. aegyptiaca. Under all conditions, Na^+ levels of S. aegyptiaca were twice those of C. procera plants. All stresses reduced the K^+/Na^+ ratio in C. procera leaves. On the other hand, S. aegyptiaca plants were able to maintain this ratio near control levels under salinity and drought stresses. Consequently, S. aegyptiaca leaves had higher partial osmotic pressure than C. procera. The proline and total free amino acids levels in C. procera were between 1.3- and 2-fold higher than in S. aegyptiaca. Among all amino acids, the common change in both species under all stresses was an accumulation of free proline and a decrease in methionine levels. The results revealed that the response of both species to salinity and water stresses included avoidance and tolerance mechanisms with some differences between them.

Generalization of membrane reflection coefficients for nonideal, nonisothermal, multicomponent systems with external forces and viscous flow

The notion of reflection coefficients is generalized from dilute ideal solutions to apply to virtually any kind of solution and any kind of membrane whose properties are not affected by the solution. The crucial points in the generalization are the selection of a suitable definition of partial osmotic pressure and the inclusion of separative viscous flow as a transport mechanism (necessary to obtain the correct semipermeability limit). The latter can lead to loss or concealment of Onsager reciprocity, so that the reflection coefficients for volume flow and for solute fluxes are not necessarily equal. Two choices of reference state are presented: the traditional choice of zero reflection coefficient for solvent volume flow, and a more symmetric choice of an average reflection coefficient equal to zero. Several examples are worked out for binary and ternary solutions and compared with results from experiments and from model calculations. Thermal gradients are included for completeness, but play no essential role in the reflection coefficients. The development is given entirely in terms of differential equations of transport, and problems and inconsistencies associated with the use of finite-difference equations are briefly discussed.

The thermodynamic analysis of the observed osmotic pressures of protein salts in solutions of finite concentration

The application of Dalton’s law of partial pressures to the osmotic pressures of mixtures of protein salts and diffusible salts has been discussed in a previous communication. The observed osmotic pressures of protein salts, measured with membranes permeable by water and other crystalloids but impermeable by the protein, are difficult to interpret until they have been analysed in terms of the partial osmotic pressures of protein ions and of diffusible ions. The partial osmotic pressure of the protein ions, symbolised p p , may be calculated from the observed osmotic pressure p by the formula p = p p + P i , in which P i represents the “ion pressure difference,” or the pressure due to the excess of diffusible ions inside the membrane. The provisional estimates of these partial pressures, p p and p i , published in the paper referred to above, depend upon a number of simplifying assumptions concerning the deviations from the ideal solution laws in mixtures of protein salts and diffusible salts, and the range of application of the approximate formulæ employed is restricted to mixtures in which the equivalent concentration of the protein salt is relatively small. In order to confirm the provisional results and to interpret the osmotic pressures of concentrated protein solutions, a more general method, based on Gibb’s fundamental equations, is developed in this paper.

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A theory of partial osmotic pressures and membrane equilibria, with special reference to the application of Dalton's Law to hæmoglobin solutions in the presence of salts

Dalton's Law of Partial Pressures affords a point of departure for the discussion of the osmotic of colloidal solutions. The observed osmotic pressure of a solution of a protein such as hæmoglobin is essentially a property of the protein system as a whole, and a knowledge of the partial pressures of the various components is of service in a systematic study of the properties of the solution. It will be shown that many of the difficulties in the interpretation of such systems can be overcome by the application of Dalton's Law in the form used by Gibbs.

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