Active volume regulation in adhered cells

Recent experiments reveal that the volume of adhered cells is reduced as their basal area is increased. During spreading, the cell volume decreases by several thousand cubic micrometers, corresponding to large pressure changes of the order of megapascals. We show theoretically that the volume regulation of adhered cells is determined by two concurrent conditions: mechanical equilibrium with the extracellular environment and a generalization of Donnan (electrostatic) equilibrium that accounts for active ion transport. Spreading affects the structure and hence activity of ion channels and pumps, and indirectly changes the ionic content in the cell. We predict that more ions are released from the cell with increasing basal area, resulting in the observed volume–area dependence. Our theory is based on a minimal model and describes the experimental findings in terms of measurable, mesoscale quantities. We demonstrate that two independent experiments on adhered cells of different types fall on the same master volume–area curve. Our theory also captures the measured osmotic pressure of adhered cells, which is shown to depend on the number of proteins confined to the cell, their charge, and their volume, as well as the ionic content. This result can be used to predict the osmotic pressure of cells in suspension.

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Pressure Gradients Affecting the Labyrinth during Hypobaric Pressure

Annals of Otology Rhinology & Laryngology ◽

10.1177/000348949710600610 ◽

1997 ◽

Vol 106 (6) ◽

pp. 495-502 ◽

Cited By ~ 10

Author(s):

Konrád S. Konrádsson ◽

Björn I. R. Carlborg ◽

Joseph C. Farmer

Keyword(s):

Cerebrospinal Fluid ◽

Eustachian Tube ◽

Ambient Pressure ◽

Pressure Gradients ◽

Cochlear Aqueduct ◽

Fluid Compartment ◽

Large Pressure ◽

Fluid Compartments ◽

Pressure Changes ◽

Considerable Pressure

Hypobaric effects on the perilymph pressure were investigated in 18 cats. The perilymph, tympanic cavity, cerebrospinal fluid, and systemic and ambient pressure changes were continuously recorded relative to the atmospheric pressure. The pressure equilibration of the eustachian tube and the cochlear aqueduct was studied, as well as the effects of blocking these channels. During ascent, the physiologic opening of the eustachian tube reduced the pressure gradients across the tympanic membrane. The patent cochlear aqueduct equilibrated perilymph pressure to cerebrospinal fluid compartment levels with a considerable pressure gradient across the oval and round windows. With the aqueduct blocked, the pressure decrease within the labyrinth and tympanic cavities was limited, resulting in large pressure gradients toward the chamber and the cerebrospinal fluid compartments, respectively. We conclude that closed cavities with limited pressure release capacities are the cause of the pressure gradients. The strain exerted by these pressure gradients is potentially harmful to the ear.

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Colloid osmotic pressure changes of dog's blood exposed to different mixtures of CO2 and air

Journal of Applied Physiology ◽

10.1152/jappl.1978.44.2.254 ◽

1978 ◽

Vol 44 (2) ◽

pp. 254-257 ◽

Cited By ~ 1

Author(s):

Y. Kakiuchi ◽

A. B. DuBois ◽

D. Gorenberg

Keyword(s):

Red Blood Cells ◽

Osmotic Pressure ◽

Cell Volume ◽

Blood Cells ◽

Freezing Point ◽

Colloid Osmotic Pressure ◽

Red Cell ◽

Freezing Point Depression ◽

Pressure Changes ◽

Different Levels

Hansen's membrane manometer method for measuring plasma colloid osmotic pressure was used to obtain the osmolality changes of dogs breathing different levels of CO2. Osmotic pressure was converted to osmolality by calibration of the manometer with saline and plasma, using freezing point depression osmometry. The addition of 10 vol% of CO2 to tonometered blood caused about a 2.0 mosmol/kg H2O increase of osmolality, or 1.2% increase of red blood cell volume. The swelling of the red blood cells was probably due to osmosis caused by Cl- exchanged for the HCO3- which was produced rapidly by carbonic anhydrase present in the red blood cells. The change in colloid osmotic pressure accompanying a change in co2 tension was measured on blood obtained from dogs breathing different CO2 mixtures. It was approximately 0.14 mosmol/kg H2O per Torr Pco2. The corresponding change in red cell volume could not be calculated from this because water can exchange between the plasma and tissues.

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Colloid osmotic pressure changes in human whole blood and separated plasma in vitro with changes in CO2 content and pH

Comparative Biochemistry and Physiology Part A Physiology ◽

10.1016/0300-9629(86)90452-4 ◽

1986 ◽

Vol 85 (3) ◽

pp. 587-591 ◽

Cited By ~ 3

Author(s):

Christopher S. Ogilvy ◽

C.Bruch Wenger ◽

P.Glenn Tremml ◽

Arthur B. Dubois

Keyword(s):

Osmotic Pressure ◽

Whole Blood ◽

Colloid Osmotic Pressure ◽

Human Whole Blood ◽

Pressure Changes

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The Sensitivity of the Pedal Ganglion of the Slug to Osmotic Pressure Changes

Journal of Experimental Biology ◽

10.1242/jeb.33.3.493 ◽

1956 ◽

Vol 33 (3) ◽

pp. 493-501

Author(s):

G. A. KERKUT ◽

B. J. R. TAYLOR

Keyword(s):

Osmotic Pressure ◽

Ionic Concentration ◽

The Body ◽

Bathing Solution ◽

Pedal Ganglion ◽

Bathing Medium ◽

Rates Of Change ◽

Fluid Concentration ◽

Locke Solution ◽

Pressure Changes

1. The effects of different dilutions of Locke solution on the electrical activity of the isolated pedal ganglion of the slug can be reproduced by adding different concentrations of glucose of mannitol to a given concentration of Locke. 2. This indicates that certain cells in the pedal ganglion are sensitive to the osmotic pressure of the solution and not its ionic concentration. 3. The preparation is sensitive to slow changes in the concentration of the bathing medium. The cells increased their activity when the bathing solution was slowly changed from 0.7 Locke to 0.6 Locke, the change taking 43 min. This corresponds approximately to a change of 1% of the body fluid concentration over 4 min. Such rates of change are found in the normal intact animal. 4. The sensitivity of the preparation compares well with that of the mammalian osmoreceptors.

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Activated Shale Creep and Potential Micro-Annulus Investigated in the Field

10.2118/204088-ms ◽

2021 ◽

Author(s):

Andreas Bauer ◽

Matteo Loizzo ◽

Laurent Delabroy ◽

Tron Golder Kristiansen ◽

Kristian Klepaker

Keyword(s):

Core Sample ◽

Inversion Algorithm ◽

Log Data ◽

Sealing Capacity ◽

Large Pressure ◽

Elastic Rebound ◽

Zonal Isolation ◽

Pressure Changes ◽

Drilling Muds ◽

The Impact

Abstract It has been demonstrated that creeping shales can form effective hydraulic well barriers. Shale barriers have been used for many years in P&A of wells in Norway. More recently, shale barriers for zonal isolation have also been used in new wells where shale creep was found to occur within days. In some cases, shale creep is activated by a reduction in annulus pressure, in other cases shale creep sets in without any active activation, possibly by time-dependent formation-pressure changes. However, the presence of thixotropic fluids (drilling muds) in the annulus may prevent full closure of the annulus as it requires large pressure differentials to squeeze the fluid out of a microannulus. Furthermore, elastic rebound of an actively activated shale barrier could result in a microannulus and hence a possible leakage pathway. Improved logging technology is needed for identifying shale barriers and the presence of micro-annuli in shale-barrier zones. We use cement bond log data and standard bond logging criteria to evaluate the quality of the shale well barriers (Williams et al., 2009). In addition, in order to detect microannuli on the outside of the casing, a new inversion algorithm for the bond logging data was developed and tested on field data. Later, we had the chance to apply the inversion algorithm to bond-log data obtained in the laboratory with a miniature bond-logging tool inside a cased hollow-cylinder shale-core sample place. It turned out that both the micro-annulus widths and shale velocities determined by the inversion technique were too high. By constraining the shale velocities to more realistic values, the updated microannulus widths were smaller and more consistent with the experimental results. Small microannuli may not cause any measurable leakage along the well, especially if filled with a thixotropic fluid. However, more studies are needed to quantify the impact of microannuli on the sealing capacity of shale barriers.

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HYSTERESIS IN SILICA GEL SORPTION SYSTEMS

Canadian Journal of Research ◽

10.1139/cjr34-059 ◽

1934 ◽

Vol 10 (6) ◽

pp. 713-729 ◽

Cited By ~ 6

Author(s):

L. M. Pidgeon

Keyword(s):

Hysteresis Loop ◽

Silica Gel ◽

Sulphur Dioxide ◽

Water System ◽

The Other ◽

Vapor Pressures ◽

Large Pressure ◽

Pressure Changes ◽

Permanent Gases ◽

Sorption Systems

The hysteresis which normally appears in the isotherms of the silica gel-water system has been attributed by Patrick to the presence of permanent gases in the system. Only one case has been found in which a reversible isotherm has been recorded in the silica gel-water system. For alcohol and benzene only one case of hysteresis has been reported. These results seem to be independent of the presence or absence of air or other gases.The sorption of water, benzene and ethyl alcohol has been examined using the sorption balance. A hysteresis loop appears for water only. This hysteresis may not be eliminated by special methods of evacuation and must be considered as a real effect. The isotherms of alcohol and benzene, on the other hand, are completely reversible. It has been shown that the dimensions of the hysteresis occurring in the water system may be affected by the manner of addition of vapor to the apparatus. Only when the vapor pressures remain reasonably constant during sorption are the dimensions of the effect evident. If very large pressure changes take place the hysteresis may disappear.A comparison of the isotherms for water showing hysteresis, and those of the sulphur dioxide system (upon which the original suggestion as to the cause of hysteresis was based) show that there is not necessarily any relation between the two.

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Correlation between osmoregulation and cell volume regulation

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1987.252.4.r768 ◽

1987 ◽

Vol 252 (4) ◽

pp. R768-R773

Author(s):

M. A. Lang

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Osmotic Pressure ◽

Cell Volume ◽

Free Amino Acids ◽

Volume Regulation ◽

Free Amino ◽

Cell Volume Regulation

The euryhaline crab, Callinectes sapidus, behaves both as an osmoregulator when equilibrated in salines in the range of 800 mosM and below and an osmoconformer when equilibrated in salines above 800 mosM. There exists a close correlation between osmoregulation seen in the whole animal in vivo and cell volume regulation studied in vitro. Hyperregulation of the hemolymph osmotic pressure and cell volume regulation both occurred in salines at approximately 800 mosM and below. During long-term equilibration of the crabs to a wide range of saline environments, the total concentration of hemolymph amino acids plus taurine remained below 3 mM. During the first 6 h after an acute osmotic stress to the whole animal, the hemolymph osmotic pressure and Na activity gradually decreased, whereas the free amino acids remained below 3 mM. As the hemolymph osmotic pressure decreased below approximately 850 mosM, the amino acid level began to increase to 17-25 mM. This change was primarily due to increases in glycine, proline, taurine, and alanine. The likely source of the increase in hemolymph free amino acids in vivo is the free amino acid loss from muscle cells observed during cell volume regulation in vitro.

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Turgor-Volume Regulation and Cellular Water Relations of Nicotiana tabacum Roots Grown in High Salinities

Functional Plant Biology ◽

10.1071/pp9890517 ◽

1989 ◽

Vol 16 (6) ◽

pp. 517 ◽

Cited By ~ 16

Author(s):

SD Tyerman ◽

P Oats ◽

J Gibbs ◽

M Dracup ◽

H Greenway

Keyword(s):

Nicotiana Tabacum ◽

Osmotic Pressure ◽

Water Relations ◽

Volume Regulation ◽

Turgor Pressure ◽

Root Hairs ◽

Solution Culture ◽

Pressure Probe ◽

Initial Increase ◽

Solute Permeability

Nicotiana tabacum plants were grown in solution culture with salinity treatments of 1, 100 and 200 mol m-3 [NaCl], in Hoagland solution. After several weeks, solute concentrations and osmotic pressure of cell sap from the roots were measured. Increases in cellular [Na+] and [Cl-] and a smaller reduction in [K+] accounted for the difference in sap osmotic pressure between the 200 mol m-3 and 1 mol m-3 treatments. Turgor pressure (P) of fully expanded cortex cells measured with the pressure probe were 0.48 MPa in 1 mol m-3, 0.24 MPa in 100 mol m-3, 0.20 MPa in 200 mol m-3, and these values agreed with those calculated by difference between internal and external osmotic pressure. Low values of volumetric elastic modulus (ε), ranging from 1.2 MPa to 3.0 MPa at P = 0.42 MPa were obtained, which accounted for long equilibration times to changes in water potential. There was no effect of high salinities on ε after accounting for the fact that ε was a function of P and neither was there an effect on hydraulic conductivity (Lp), which ranged between 1.9 × 10-8 and 24.1 × 10-8 m s-1 Mpa-1. At 200 mol m-3 [NaCl]o, and to a lesser degree at 100 mol m-3 [NaCl]o, root hairs became deformed to resemble spherical bladders (mean diameter = 88 �m) which displayed similar P and water relations to other epidermal cells and cortex cells. In other experiments the response to a sudden reduction in [NaCl], from 200 to 1 mol m-3 was studied. P of cortex cells first rapidly increased from about 0.15 MPa to 0.53 MPa and then slowly declined with a half time of about 35 min to a new steady state of 0.3 MPa. This level was maintained in intact roots for at least 48 h. The rate of the initial increase in P is limited by water flow into the cells while the slow decline is limited by solute efflux from the cells with water following osmotically. The efflux was mainly in response to reduced external osmotic pressure rather than [NaCl]o. Efflux of Na+, K+ and Cl- accounted for the decrease in internal osmotic pressure but it is possible that the membrane also became more permeable to sugars. With the exception of bladder hairs, the overall integrity of the cell membrane was maintained since Lp did not increase and P declined smoothly to the new level with no evidence of rupture and resealing of the membrane. It is argued that the loss of solutes after the step down in external osmotic pressure consists of turgor or volume regulation in which solute permeability increases steeply as turgor or volume goes above a threshold.

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