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Results for “OSMOSIS AND PERMEABILITY”

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At least 1,009 records · Page 56Linked to original sources
PubMed1987

Sepsis in sheep reduces pulmonary microvascular sieving capacity.

The changes in pulmonary microvascular permeability in sheep, after infusion of live Escherichia coli, were studied using estimations of the osmotic reflection coefficients (sigma) for total protein, albumin, immunoglobins (Ig) G and M and based on these estimations equivalent pore dimensions were calculated. A chronic lung lymph fistula was prepared in seven sheep. After a base-line period, left atrial pressure (Pla) was increased. E. coli (10(9) X kg body wt) were given after attaining filtration independent L/P values. The sigma's for the normal lung were calculated to 0.73 for total protein and to 0.65, 0.76, and 0.91 for albumin, IgG, and IgM, respectively. The equivalent pore radii were determined to 50 and 175 A with 35% of the filtration accounted for by the large pores. After bacterial infusion, the sigma's for total protein, albumin, IgG, and IgM decreased significantly from preseptic values to 0.58, 0.50, 0.64, and 0.83, respectively. After sepsis the small pores were 50 A and the large pores 200 A with 49% of total volume flow at maximum lymph flows occurring through the large pores. Assuming a constant small-pore population the large-pore number increased 32% after bacterial infusion. These results indicate that pulmonary microvascular permeability may have increased due to the sepsis.

Animals↗
PubMed1994

Pathophysiological description of the ultrastructural changes of the peritoneal membrane during long-term continuous ambulatory peritoneal dialysis.

Some of the patients on continuous ambulatory peritoneal dialysis (CAPD) develop with time on treatment an increased transperitoneal transport of small solutes, implying that glucose is more rapidly absorbed from the dialysate. Hence, the dialysate/serum crystalloid osmotic gradient dissipates at a faster rate, so that ultrafiltration failure may result. The pathophysiological correlates to these changes are not well understood. However, it seems that with time on CAPD, there are changes in the submesothelial interstitium, affecting both the ground substance and spacing and orientation of collagen fibers. There may also be mesothelial alterations with patchy shedding of the cells. The present article discusses these changes in terms of a modified three-pore model of peritoneal permeability. In this model, the capillary walls act as a major barrier for solutes ranging in size from inulin (molecular radius 14 A) to macromolecules (molecular radius > 30 A). However, for solutes smaller than inulin both capillary wall and insterstitium contribute to the blood-peritoneum transport impedance. The increased small-solute exchange sometimes occurring in long-term CAPD can be explained either by recruitment of vascular surface area, due, e.g., to an increased capillarization of the peritoneal membrane with time, or, more likely, a drop in the interstitial transport resistance to small solutes. The latter possibility is supported by the often more pronounced increase in the transperitoneal transfer of small solutes than that of macromolecules over time in CAPD.

Biological Transport↗
PubMedDate not supplied

The effect of cell size distribution on predicted osmotic responses of cells.

An understanding of the kinetics of the osmotic response of cells is important in understanding permeability properties of cell membranes and predicting cell responses during exposure to anisotonic conditions. Traditionally, a mathematical model of cell osmotic response is obtained by applying mass transport and Boyle-vant Hoff equations using numerical methods. In the usual application of these equations, it is assumed that all cells are the same size equal to the mean or mode of the population. However, biological cells (even if they had identical membranes and hence identical permeability characteristics--which they do not) have a distribution in cell size and will therefore shrink or swell at different rates when exposed to anisotonic conditions. A population of cells may therefore exhibit a different average osmotic response than that of a single cell. In this study, a mathematical model using mass transport and Boyle-van't Hoff equations was applied to measured size distributions of cells. Chinese hamster fibroblast cells (V-79W) and Madin-Darby canine kidney cells (MDCK), were placed in hypertonic solutions and the kinetics of cell shrinkage were monitored. Consistent with the theoretical predictions, the size distributions of these cells were found to change over time, therefore the selection of the measure of central tendency for the population may affect the calculated osmotic parameters. After examining three different average volumes (mean, median, and mode) using four different theoretical cell size distributions, it was determined that, for the assumptions used in this study, the mean or median were the best measures of central tendency to describe osmotic volume changes in cell suspensions.

Animals↗
PubMed1989

[The relationship between the intracellular content of 1-methyl-3-isobutylxanthine and the permeability for water of the bladder wall in the frog].

The data obtained show a direct interrelationship between the concentration of MIBX in cells and an increase of osmotic permeability. The method of determination of intracellular concentration of the MIBX using [3H]-MIBX, was developed, and the way to obtain radioactive MIBX described. The used approach permits to take into consideration functional changes as related to the intracellular concentration of inhibiting agents.

1-Methyl-3-isobutylxanthine↗
PubMed1989

Measurement of peritoneal lymph flow in CAPD using different osmotic agents.

No differences in lymphatic absorption ratio were observed using different osmotic agents (Glucose, Amino acid, glycorol). The differences in UF rate and intraperitoneal volumes during dialysis with these osmotic agents are soley dependent on the interactions between the osmotic agents (nature, strength) and the peritoneal membrane.

Absorption↗
PubMed1982

[Calcium-containing granules in frog bladder cells exposed to ionophore A-23187 and antidiuretic hormone].

Granules of granular cells of the frog bladder epithelium are shown concentrated near the apical cell membrane. The electron density of these granules is getting intensified after addition of antidiuretic hormone (ADH) and ionophore A23187. The intracellular localization of granules depends on the site of ionophore application--to the apical or basal membrane. The vacuolization of granular cells increases with the rising of water flow under the influence of ADH or ionophore A23187.

Animals↗
PubMed1976

[Effect of various antimicrotubular drugs on the osmotic water flow through the wall of frog's urinary bladder].

The action of antimicrotubular drugs (colchicine, vinblastine and copper) on the osmotic water flow through the wall of the urinary bladder of Rana temporaria has been studied. The osmotic gradient was made by five- or tenfold dilution of the internal Ringer solution. The water flow was estimated gravimetrically. The water flow was induced by pituitrin (50 milliunits/ml), cyclic AMP (cAMP, 0.5-10(-3) M) and nystatine (3.5-10(-5) M). Pituitrin and cAMP and all the antimicrotubular drugs were added from the serosal surface of the bladder. Nystatine was introduced with the help of a fixed polyethylene tube. Preincubation with colchicine lasted 4 hours and that with vinblastine and copper (CuSO4), 1 hour. The drug concentrations varied between 10(-5)--10(-4) M. All the drugs studied showed a significant inhibitory effect toward pituitrin. The action of cAMP on the water flow was seen inhibited in the presence of colchicine and copper. The nystatine induced water flow was supressed by copper, colchicine being in this case inactive. A conclusion is drawn that the inhibition of cAMP formation does not cause a decreased pituitrine effect in the presence of antimicrotubular drugs. It has been assumed that the microtubules may be involved in the directed water flow within the cell.

Animals↗
PubMed1971

Coupling of solute and solvent flows in porous lipid bilayer membranes.

The present experiments were designed to evaluate coupling of water and nonelectrolyte flows in porous lipid bilayer membranes (i.e., in the presence of amphotericin B) in series with unstirred layers. Alterations in solute flux during osmosis, with respect to the flux in the absence of net water flow, could be related to two factors: first, changes in the diffusional component of solute flux referable to variations in solute concentrations at the membrane interfaces produced by osmotic flow through the unstirred layers; and second, coupling of solute and solvent flows within the membrane phase. Osmotic water flow in the same direction as solute flow increased substantially the net fluxes of glycerol and erythritol through the membranes, while osmotic flow in the opposite direction to glycerol flow reduced the net flux of that solute. The observed effects of osmotic water flow on the fluxes of these solutes were in reasonable agreement with predictions based on a model for coupling of solute and solvent flows within the membrane phase, and considerably in excess of the prediction for a diffusion process alone.

Amphotericin B↗
PubMed1996

Transalveolar osmotic and diffusional water permeability in intact mouse lung measured by a novel surface fluorescence method.

A surface fluorescence method was developed to measure transalveolar transport of water, protons, and solutes in intact perfused lungs. Lungs from c57 mice were removed and perfused via the pulmonary artery (approximately 2 ml/min). The airspace was filled via the trachea with physiological saline containing a membrane-impermeant fluorescent indicator (FITC-dextran or aminonapthalene trisulfonic acid, ANTS). Because fluorescence is detected only near the lung surface due to light absorption by lung tissue, the surface fluorescence signal is directly proportional to indicator concentration. Confocal microscopy confirmed that the fluorescence signal arises from fluorophores in alveoli just beneath the pleural surface. Osmotic water permeability (Pf) was measured from the time course of intraalveolar FITC-dextran fluorescence in response to changes in perfusate osmolality. Transalveolar Pf was 0.017 +/- 0.001 cm/s at 23 degrees C, independent of the solute used to induce osmosis (sucrose, NaCl, urea), independent of osmotic gradient size and direction, weakly temperature dependent (Arrhenius activation energy 5.3 kcal/mol) and inhibited by HgCl2. Pf was not affected by cAMP activation but was decreased by 43% in lung exposed to hyperoxia for 5 d. Diffusional water permeability (Pd) and Pf were measured in the same lung from intraalveolar ANTS fluorescence, which increased by 1.8-fold upon addition of 50% D2O to the perfusate, Pd was 1.3 x 10(-5) cm/s at 23 degrees C. Transalveolar proton transport was measured from FITC-dextran fluorescence upon switching perfusate pH between 7.4 and 5.6; alveolar pH half-equilibrated in 1.9 and 1.0 min without and with HCO3-, respectively. These results indicate high transalveolar water permeability in mouse lung, implicating the involvement of molecular water channels, and establish a quantitative surface fluorescence method to measure water and solute permeabilities in intact lung.

Animals↗
PubMed1997

Water distribution and permeability of zebrafish embryos, Brachydanio rerio.

Teleost embryos have not been successfully cryopreserved. To formulate successful cryopreservation protocols, the distribution and cellular permeability to water must be understood. In this paper, the zebrafish (Brachydanio rerio) was used as a model for basic studies of the distribution to permeability to water. These embryos are a complex multi-compartmental system composed of two membrane-limited compartments, a large yolk (surrounded by the yolk syncytial layer) and differentiating blastoderm cells (each surrounded by a plasma membrane). Due to the complexity of this system, a variety of techniques, including magnetic resonance microscopy and electron spin resonance, was used to measure the water in these compartments. Cellular water was distributed unequally in each compartment. At the 6-somite stage, the percent water (V/V) was distributed as follows: total in embryo = 74%, total in yolk = 42%, and total in blastoderm = 82%. A one-compartment model was used to analyze kinetic, osmotic shrinkage data and determine a phenomenological water permeability parameter, Lp, assuming intracellular isosmotic compartments of either 40 or 300 mosm. This analysis revealed that the membrane permeability changed (P < 0.05) during development. During the 75% epiboly to 3-somite stage, the mean membrane permeability remained constant (Lp = 0.022 +/- 0.002 micron x min-1atm-1 [mean +/- S.E.M.] assuming isosmotic is 40 mosm or Lp = 0.049 +/- 0.008 micron x min-1atm-1 assuming isosmotic is 300 mosm). However, at the 6-somite stage, Lp increased twofold (Lp = 0.040 +/- 0.004 micron x min-1atm-1 assuming isosmotic is 40 mosm or Lp = 0.100 +/- 0.017 micron x min-1atm-1 assuming isosmotic is 300 mosm). Therefore, the low permeability of the zebrafish embryo coupled with its large size (and consequent low area to volume ratio) led to a very slow osmotic response that should be considered before formulating cryopreservation protocols.

Animals↗