Osmotic Component Research Articles

Laboratory Evaluation of Soil Suction Components

Abstract A laboratory evaluation of the soil-water potential components (total, matrix, and osmotic suction) is presented using a series of clay specimens statically compacted dry- and wet-of-optimum. In unsaturated soils, moisture movement is controlled either by total or matrix suction depending upon the degree of unsaturation, whereas deformation and strength behavior is controlled primarily by matrix suction. Therefore, it is imperative to evaluate the suction components separately. Significant osmotic suction component was induced as a result of incomplete leaching of the sodium and calcium surface-saturated Grundite (initially prepared by treating the clay slurry with strong sodium chloride and calcium chloride solutions to achieve mass action of cations). Matrix suction was induced by equilibrating the specimens to different pressures on a ceramic-plated extractor. At equilibrium, total suction of the specimens was measured using a Peltier type psychrometer. Test results indicate the use and limitations of the psychrometric method and the interrelationship of suction components. Measured values of the total suction by the psychrometric method indicate more consistent results at moisture contents above the plastic limit. Below the plastic limit, the osmotic component, as deduced by the difference between total and induced matrix suctions, tends to decrease gradually with increasing matrix suction. It is found that the osmotic suction can be measured most suitably on pore-water extracts using psychrometry.

Physiologic determinants of biliary calcium secretion in the dog

Studies were carried out to define the origins and physiologic determinants of biliary calcium secretion in the dog. Canalicular bile flow was varied by infusions of several bile acids or a canalicular choleretic agent, SC2644. Three natural bile acids (cholyltaurine, chenodeoxycholyltaurine, and ursodeoxycholyltaurine) that have a low critical micellar concentration and a synthetic hydroxy-oxo bile acid (12-dehydrocholyltaurine) with a much higher critical micellar concentration were used. Calcium output, bile acid output, and bile flow were determined; canalicular bile flow was assessed by measurement of erythritol clearance. Calcium output increased linearly with bile acid output for all three natural bile acids (r = 0.94; 0.026–0.035 μmolΔcalcium /μmolΔbile acid), but chenodeoxycholyltaurine and ursodeoxycholyltaurine infusions induced a slightly greater secretion of calcium for a given bile acid output and bile flow than cholyltaurine. Calcium output also increased linearly with bile flow, whether bile flow was induced by the canalicular choleretic SC2644 (r = 0.93; 0.0018 μmolΔcalcium/ μlΔwater) or the hydroxy-oxo bile acid (r = 0.99; 0.0021 μolΔcalciumμlΔwater). Because the calcium output induced by the three micelle-forming bile acids was greater than that which could be explained by the induced increase in bile flow per se, it was deduced that canalicular calcium has two origins; a micellar component that is dependent on the presence of micelles or micelle-forming bile acids and an osmotic component that is dependent on osmotic forces, e.g., caused by secretion induced by SC2644 or bile acid molecules and possibly bile acid micelles. A small bile acid-independent output of calcium was also detected and should contribute to the osmotic fraction. To determine whether ductular modification of bile flow influenced biliary calcium secretion, ductular secretion was induced by secretin and ductular absorption was induced by somatostatin. Changes in calcium output followed water movements, increasing with ductular secretion and decreasing with ductular absorption. The relationship between changes in ductular bile flow and calcium output was identical during induced ductular secretion (r = 0.83; 0.0016 μmolΔcalcium/ μlΔwater) or induced ductular absorption (r = 0.91; 0.0019 μmolΔcalcium/μlΔwater). Thus calcium movements in relation to water movements were identical for the osmotic component of canalicular bile and the ductular component of bile. The experimental manipulations in bile secretion caused anticipated changes in biliary calcium concentration which ranged from 1.6 to 6.4 mM. These results indicate that at the usual rates of bile acid secretion, most biliary calcium originates at the canaliculus and is bile acid-dependent. The biliary ductule is permeable to calcium, but the effect of ductular modification of bile flow on biliary calcium outputs is small.

Effect of 2,4-dinitrophenol and ionophores on growth and methanogenesis inMethanobacterium thermoautotrophicum

2,4-Dinitrophenol and gramicidin D completely inhibited growth and methanogenesis inMethanobacterium thermoautotrophicum. At low K+ concentrations valinomycin inhibited growth and methanogenesis relatively slightly, at high K+ concentrations (0.1m KCl) growth was inhibited completely and methanogenesis by about 50%. Monensin and nigericin inhibited growth completely; methanogenesis was inhibited like with valinomycin at high K+ concentrations. The results can be interpreted in terms of Mitchell’s chemiosmotic theory as follows. The protonmotive force inM. thermoautotrophicum is the basic source of energy for endergonic processes. Dissipation of the electrical component of protonmotive force may probably be compensated by an increased generation of the proton gradient. However, the osmotic component is essential for growth ofM. thermoautotrophicum.

Freilanduntersuchungen zum Wasserhaushalt von Mercurialis perennis und Asarum europaeum: Water Relations ofMercurialis perennisandAsarum europaeumin Their Natural Habitat

In a Melico-Fagetum holdelymetosum community, plant water relations of Mercurialis perennis and Asarum europaeum were studied in October 1982. After a preceding long and sunny period without rain, at the beginning of October both plant species appeared quite different due to water stress on three neighbouring sites in close vicinity to each other. At the first site the plants seemed to wilt, on the second they were fully expanded, and on the third they were neither wilted nor expanded. These differences in the shape were reflected by the leaf water potential and the osmotic component. Apparently small scale microclimatical changes between sites lasting for a longer period were mainly responsible for the site differences. On the other hand Mercurialis showed more negative values in leaf water potential and osmotic component on each site compared to Asarum. This differential behaviour between species can be explained by the fact that during extensive dry periods Mercurialis does not close its stomata, while Asarum early reduces transpiration.

Proton motive force and Na+/H+ antiport in a moderate halophile.

The influence of pH on the proton motive force of Vibrio costicola was determined by measuring the distributions of triphenylmethylphosphonium cation (membrane potential, delta psi) and either dimethyloxazolidinedione or methylamine (osmotic component, delta pH). As the pH of the medium was adjusted from 5.7 to 9.0, the proton motive force steadily decreased from about 170 to 100 mV. This decline occurred, despite a large increase in the membrane potential to its maximum value at pH 9.0, because of the loss of the pH gradient (inside alkaline). The cytoplasm and medium were of equal pH at 7.5; membrane permeability properties were lost at the pH extremes of 5.0 and 9.5. Protonophores and monensin prevented the net efflux of protons normally found when an oxygen pulse was given to an anaerobic cell suspension. A Na+/H+ antiport activity was measured for both Na+ influx and efflux and was shown to be dissipated by protonophores and monensin. These results strongly favor the concept that respiratory energy is used for proton efflux and that the resulting proton motive force may be converted to a sodium motive force through Na+/H+ antiport (driven by delta psi). A role for antiport activity in pH regulation of the cytosol can also explain the broad pH range for optimal growth, extending to the alkaline extreme of pH 9.0.

Control of evaporative heat loss during changes in plasma osmolality in the cat.

1. The effects of intravenous infusion of hypertonic saline and distilled water into normally hydrated and dehydrated cats have been examined at both high and neutral ambient temperatures.2. In hydrated cats measurements of body temperature (T(b)) and evaporative heat loss (e.h.l.) show that infusion of 30% saline (1.5 ml./kg) at an ambient temperature of 38 degrees C, lowers e.h.l. by an average of 0.21 W/kg (P < 0.001) and elevates T(b) by 0.43 degrees C (P < 0.01).3. At 25 degrees C alterations in these two parameters were in the same direction, though not statistically different from pre-infusion levels (P > 0.05).4. Infusion of distilled water (15 ml./kg) into dehydrated animals produced significant increases in e.h.l. (+0.35 W/kg, P < 0.001) and reductions in T(b) (-0.45 degrees C, P < 0.001) at 38 degrees C. No significant effects were observed at 25 degrees C.5. Infusion of water into normally hydrated animals at 38 degrees C also significantly increased e.h.l. (+0.13 W/kg, P < 0.05) and insignificantly lowered T(b) (-0.03 degrees C, P > 0.05).6. Local heating of the preoptic hypothalamic area in four animals indicated that hypertonic saline infusion into normally hydrated animals caused a reduction in the slope and displacement to the right of the relationship between hypothalamic temperature and e.h.l.7. Conversely, water infusion into dehydrated animals increased the slope and shifted this relationship to the left.8. These experiments provide evidence for an osmotic interaction in body temperature regulation which acts to alter the responsiveness of the hypothalamus to increasing temperature. This osmotic component may be an important factor in the alterations in thermoregulation seen in dehydrated animals.

Na+-induced intestinal interstitial hyperosmolality and vascular responses during absorptive hyperemia.

The coupled active transport of Na+ with sugars and amino acids could cause intestinal villus interstitial hyperosmolarity, which contributes to absorptive hyperemia. However, for the villus hyperosmolarity to cause a major vascular response, a mild-to-moderate hyperosmolarity must occur in the vicinity of the major resistance vessels of the submucosa. Interstitial Na+ activity was measured throughout the small intestinal wall of rats with monensin ion-selective electrodes during glucose absorption. In the upper half of villi, the resting [Na+] was 201 +/- 5 (SE) mM and increased to 267 +/- 6 mM during luminal exposure to 25-300 mg/100 ml glucose. The submucosal resting [Na+] was 144 +/- 1 mM and increased to 177 +/- 3 mM during luminal glucose exposure. The time courses of Na+ appearance and submucosal arterial dilation were almost identical. Calculations of tissue osmolarity indicate an increase in villus osmolarity of 150-200 mosM and 79-90 mosM in the submucosa during glucose absorption. The data are interpreted to indicate that villus hyperosmolarity during glucose absorption increased submucosal osmolarity and a naturally occurring osmotic dilatory component of absorptive hyperemia could exist.

Relation between Osmotic Fragility and Component of Human Red Cells in vitro Treated with Beryllium Chloride

Relation between Osmotic Fragility and Component of Human Red Cells in vitro Treated with Beryllium Chloride

Zur Pathophysiologie und Klinik des Morbus Menière

The most prominent changes in temporal bone histopathology of Menière's disease are hydrops-like extensions of the endolymphatic spaces. The endolymphatic hydrops seems to be the consequence of a diminished function or complete atrophy of the endolymphatic sac. The etiology or pathomechanism of perisaccular fibrosis or saccular degeneration is unknown. But as a consequence of experimental datas obtained by animal studies the pathogenesis of the endolymphatic hydrops can be explained by osmotic active forces which develope within the endolymphatic spaces after blockage of the endolymphatic aqueduct or sac: An increasing concentration of osmotic active endolymphatic components cause an influx of water from the perilymphatic (extracellular) environment so that the limiting membranes of the endolymphatic space have to extend (e.g. Reissner's membrane, saccular membrane). At any topographic location of the endolymphatic spaces these membranes can rupture followed by intermixing of potassium-rich endolymph with sodium rich perilymph. This leads to an acute or chronic intoxication of those sensory nerve elements which have close contact to perilymphatic fluid. The hypothesis of an osmotic induced accumulation of "water' during endolymphatic hydrops is supported by sometime striking results of the glycerol test. Nevertheless, the pathogenesis and etiology of Menière's disease remains obscure, as indicated by the diverging spectrum of the different conservative or surgical therapeutic methods in use.

The osmotic component of swelling under extended wear soft contact lenses.

Swelling of the cornea during sleep when wearing an extended wear contact lens has a osmotic and hypoxic component. The normal swelling of the cornea during sleep, caused by the change from hypertonic tears of the open eye to the isotonic tears of the closed eye, is about 3%. Under an extended-wear contact lens, there is an additional 6 to 8% swelling of the cornea in the closed eye because the cornea under the contact lens is at an oxygen tension substantially below that present in the palpebral conjunctiva. Data on human subjects wearing extended wear contact lenses are consistent with this allocation of the 8 to 12% total corneal swelling observed upon awakening.

Water Potential-Water Content Characteristics of Wheat Straw

Water is an important environmental factor affecting microbial decomposition of crop residues. To study the influence of water on residue decomposition, knowledge of the water potential-water content relationship of crop residue would be very useful. The concept of soil-water potential is well established, but limited data are available relating water potential to crop residue water content. Thermocouple psychrometry and hydraulic press methods were used to measure the water potential (ψ) characteristics of chopped and ground wheat straw (Triticum aestivum L.). The data fit the empirical relationship ψ = aθ-b (where θ = water content and a and b are empirical constants), with large coefficients of determination likely, because the osmotic component of wheat straw can be significant depending on leaching history. There was no difference between the matric potential curves of ground and chopped straw over the range −50 to −1 bar. The hydraulic press did not appear to measure the true matric potential characteristics of wheat straw as determined by thermocouple psychrometry. The water potential-water content relationships of wheat straw were quite different from those of a Palouse silt loam (fine-silty, mixed, mesic pachic Ultic Haploxerolls) used as an example. The data presented show the importance of using water potential to adjust water when, for example, comparative residue-soil incubation studies are conducted, otherwise differences in water relationships can result when these studies are conducted on the basis of water content.

Pressure-flow characteristics of the roots ofZea mays

Root pressure is generally considered to be osmotic in origin. This explanation is not held by all workers, however. An alternative view contends that while an osmotic component certainly exists, the xylem concentrations are inadequate to account for the total pressure and that therefore the remainder must result from some form of active water pumping (see for example [2,4]). In the ideal method of testing this claim one would allow the root pressure to attain its maximum value, collect a sample of the xylem sap and compare its osmotic pressure to that developed by the root. Unfortunately, this is impossible with present techniques, since to develop maximum pressures requires zero flow, in which case no sap can be collected. One can, however, reduce the flow very nearly to zero and still obtain a small sample for comparison. Such an experiment was performed by collecting 50 µl samples of exudate from each of 22 plants under 2.7 bar pressure and pooling them for analysis. Since the exudation flowrate in this case was reduced to an average of only 7% of the unimpeded rate, the results should represent a close approximation to the ideal case. The osmotic pressure of the exudate collected in this way was found to be 3.2 bar above that of the bathing solution, well in excess of the applied pressure. Thus in the present instance, there is no need to assume that root pressure is generated by any means other than osmotic.

Seasonal patterns of leaf water relations in four co-occurring forest tree species: Parameters from pressure-volume curves.

Leaf water relationships were studied in four widespread forest tree species (Ilex opaca Ait., Cornus florida L., Acer rubrum L., and Liriodendron tulipifera L.). The individuals studied all occurred on the same site and were selected to represent a range of growth forms and water relationships in some of the principal tree species of the region. The water relations of the species were analyzed using the concept of the water potential-water content relationship. The pressure-volume method was used to measure this relationship using leaf material sampled from naturally occurring plants in the field. Water potential components (turgor, osmotic, and matric) were obtained by analysis of the pressure-volume curves.Initial osmotic potentials (the value of the osmotic component at full turgidity) were highest (least negative) at the start of the growing season. They decreased (becoming progressively more negative) as the season progressed through a drought period. Following a period of precipitation at the end of the drought period, initial osmotic potentials increased toward the values measured earlier in the season.Seasonal osmotic adjustments were sufficient in all species to allow maintenance of leaf turgor through the season, with one exception: Acer appeared to undergo some midday turgor loss during the height of the July drought period.In addition to environmental influences, tissue stage of development played a role; young Ilex leaves had higher early season initial osmotic potentials than overwintering leaves from the same tree.The seasonal pattern of initial osmotic potential in Liriodendron and the observed pattern of leaf mortality suggested a possible role of osmotic potentials in the resistance of those leaves to drought conditions. The fraction of total leaf water which is available to affect osmotic potentials, called the osmotic water fraction in this study, was greatest in young tissue early in the season and declined as the season progressed.The results of this study showed that the water potential-water content relationship represents a dynamic mechanism by which plant internal water relations may vary in response to a changing external water-availability regime. The measured water relationships confirmed the relative positions of the species along a water-availability gradient, with Cornus at the wettest end and Ilex at the driest end of the gradient. Acer and Liriodendron were intermediate in their water relations. The spread of these species along a water-availability gradient on the same site suggested that coexistence is partially based on differential water use patterns.

Swelling Components of Compacted Ca-Montmorillonite

AbstractIntracrystalline water adsorption of Ca-montmorillonite was calculated as the product of one-half the interlayer spacing from X-ray powder diffraction analysis and the difference between the desorption surface area determined with ethylene glycol-monoethyl ether and BET surface area determined by N2 adsorption. Osmotic adsorption was calculated as the product of the N2 surface area and theoretical double layer thickness. Measured water adsorption of P2O5-dry clay, compacted to initial densities (γ0) from 0.52 to 1.59 g/cm3 and submerged in 0.01 N CaCl2 was 2.4 to 4.2 times greater than intracrystalline plus osmotic adsorption due to the occurrence of pores exceeding double layer dimensions. The increase in expansion caused by reducing electrolyte concentration to 0.001 N was equal to the predicted increase in double layer volume, verifying the existence of an osmotic component to swelling.Measured expansion following submersion in 0.01 N CaCl2 increased continuously with γ0 from 0.53 cm3/g at γ0 = 0.52 g/cm3 to 1.17 cm3/g at γ0 = 1.59 g/cm3, while estimated osmotic plus intracrystalline expansion was constant at 0.30 cm3/g. This discrepancy is attributed to swelling caused by gas pressures developing ahead of advancing wetting fronts. The effect of compaction on expansion is explained by reductions in pore size, as measured by N2 desorption, which accompany compaction. Reduced pore size should increase entrapped air pressures, whereas gradual wetting should favor their dissipation. Accordingly, slow wetting reduced the expansion of a sample where γ0 = 1.06 g/cm3 from 0.77 to 0.37 cm3/g. Swelling due to entrapped air pressures produced a large increase in the number of pores &gt; 104 Å in diameter, as determined by Hg intrusion porosimetry.

Influence of the Matric and Osmotic Components of Water Potential on Zoospore Discharge in Phytophthora

Influence of the Matric and Osmotic Components of Water Potential on Zoospore Discharge in Phytophthora

Effect of absorbable and non-absorbable solutes on the elongation of barley coleoptiles

The effect of combinations of mannitol and KCl on the elongation of barley coleoptile sections was investigated. During initial phases KCl reduced the lengths of coleoptile sections but after a few hours, a stimulatory effect became progressively more evident and an optimum KCl concentration at which elongation was at a maximum was clearly indicated. In time, the position of the optimum was shifted toward higher KCl concentrations. Mannitol depressed the elongation rate at all times and it caused a shift of the optimum KCl concentration toward higher values. This response of elongating Coleoptiles to added osmotica is caused by a dual effect of absorbable solutes: (1) the external water potential is reduced and through it the turgor pressure and (2) after absorption of the solutes the vacuolar osmotic component of the water potential is reduced and consequently the turgor pressure is increased. During initial phases, only the depressing effect of an osmoticum is possible but as the consequences of solute uptake become effective, the stimulation becomes noticeable. For elongating tissues, continuous solute uptake is necessary to maintain favorable cellular water relations. The observed optimum is due to the hyperbolic nature of the KCl absorption isotherm. Since little mannitol enters the cells, only a depressing effect by this osmoticum is observed. The elongation of coleoptiles could reasonably be predicted from a model of cell elongation in which solute uptake was partly rate limiting. Solute uptake is essential for maintaining a small water potential gradient favorable for water uptake which itself is necessary to maintain turgor pressure and cause elongation.

Water potentials of Salsola kali L. at differing levels of substrate water availability

Isolated embryos of Salsola kali L. (Russian thistle) were allowed to imbibe on filter paper in Peltier thermocouple psychrometer chambers with differing amounts of water available. Water potential determinations were made on the embryo-filter paper system periodically during the 24-h period of imbibition and early seedling growth. At the 24th h, complete extension of the embryonic axis occurred at an equilibrium water potential of -2 bars and an embryo water content of 114%, perceptible growth (uncoiling of the spiraled embryo) at -30 bars and 83%, and no growth or perceptible swelling at -54 bars and 56%. Hourly monitoring of the water potential of the plant-substrate system showed an initial rise toward a level that would be attained by the wetted filter paper alone and then a decline to lower water potential values at intermediate levels of water availability. This reversal is ascribed to the increasing effects of the osmotic and matric components of the total water potential of the plant tissue during imbibition and growth.

Water Potential of Germinating Seeds

Propagules of 11 species of grasses and forbs were imbibed sufficiently on water-saturated filter paper so that germination could occur subsequent to transfer into Peltier thermocouple psychrometer chambers. Water-potential determinations, made periodically during germination, showed an initial increase toward equilibrium vapor pressure and a subsequent decline to a second approximate equilibrium as low as -17 bars The decline in water-potential levels may be due to increasing effects of the osmotic and matric components of the total water potential of the propagules.

Effects of external solute supply on cell elongation in barley coleoptiles

The elongation of barley coleoptiles is stimulated by low concentrations and inhibited by high concentrations of KCl, NaCl, and RbCl, thus giving an optimum concentration at which elongation is at a maximum. The optimum concentration as well as the maximum elongation rates decrease in the order K > Na > Rb. The addition of a solute external to a cell has a dual effect on water relations: (1) it reduces the water potential and, consequently, the turgor pressure; however, (2) through solute uptake it also reduces the internal osmotic component, resulting in an increase of turgor pressure. At low concentrations, the favorable effect dominantes; at high concentrations the injurious one does. The existence of an optimum concentration was also demonstrated with a theoretical model of cell elongation in which the solute uptake followed a hyperbolic (Michaelis-Menten) relation and the injurious effect a linear relation. With help of the absorption isotherms for K, Na, and Rb, the optimum concentrations and their corresponding elongation rates were calculated. Optimum concentrations decreased in the order K > Na > Rb in agreement with the observations, whereas calculated elongation maxima decreased Na > K > Rb. Quantitatively, the agreement between calculated and observed values was good for K but less for Na and Rb.

The influx of calcium ions into human erythrocytes during cold storage. The influences of extracellular pH, intracellular adenosine triphosphate and efflux of univalent cations.

1. When human erythrocytes are stored at 3 degrees C for several days as a suspension in iso-osmotic sucrose or KCl, containing CaCl(2), the rates of cellular ATP degradation are similar. 2. During cold storage of erythrocytes in sucrose-CaCl(2) medium, Ca(2+) influx and univalent-cation efflux occur, the pH value of the suspending medium rises and the intracellular pH falls. These pH changes correlate reasonably well with alterations in the membrane potential calculated from Cl(-) distribution. 3. The presence of Ca(2+) in the medium does not increase the rate of univalent-cation efflux from the cells. 4. When the pH of the medium is raised by addition of buffers, the rates of both Ca(2+) influx and univalent-cation efflux increase. 5. Replacement of sucrose by KCl as the main osmotic component of the medium completely suppresses Ca(2+) influx and univalent-cation efflux, although the pH of the KCl medium is higher than that of the sucrose medium. 6. When sucrose is replaced by choline chloride, Ca(2+) influx and univalent-cation efflux still occur, and the pH of the medium is similar to that found in iso-osmotic KCl. 7. When valinomycin, Pb(2+) or Cd(2+) are added to the iso-osmotic sucrose medium, the rate of efflux of univalent cations increases as also does the influx of Ca(2+). 8. From these and other observations, it was concluded that it is univalent-cation efflux rather than ATP depletion or elevated extracellular pH which is the prerequisite for Ca(2+) influx during cold storage.