PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “OSMOSIS AND PERMEABILITY”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67Linked to original sources
PubMed2003

Hydration-driven transport of deformable lipid vesicles through fine pores and the skin barrier.

We studied aggregate transport through semipermeable, nano-porous barriers experimentally and theoretically. By measuring and modeling the effect of hydration gradient across such barriers, spontaneous transbarrier transport of suitable lipid aggregates in vesicular form was proven to be driven by partial aggregate dehydration at the application site. By generalizing the Onsager transport model we derived a set of equations that rationalize all pertinent observations. Dehydration-induced vesicle motion starts with a lag time. This corresponds to the time needed to reach the limiting vesicle hydration; both are proportional to the starting excess water volume and decrease with increasing relative humidity at application site. The rate of transbarrier transport is insensitive to these parameters but increases with vesicle deformability and volume exchange capability. Both these properties depend on membrane composition. Reversible demixing of bilayer components is the cause of nonlinear bilayer characteristics and also potentially affects the effective membrane hydrophilicity. High hydrophilicity of vesicle surface and extreme aggregate shape adaptability together are necessary for successful material transport across the skin. This demonstrates the significance of basic biophysical investigations for better understanding of biological systems and for the practical use of artificial, nature-inspired carriers in drug delivery.

Biological Transport↗
PubMed1995

Mechanisms involved in iontophoretic transport of angiotensin.

PURPOSE: The feasibility of using iontophoresis to enhance the permeation rate of a model peptide was investigated in vitro using hairless mouse skin. METHODS: Angiotensin 2 (AT 2) was employed as a permeant probe, using optimum iontophoresis conditions. A number of physicochemical parameters (donor ionic strength; valence of competitive ions; pH of donor solution) were studied with the aim of exploring the mechanisms involved in the iontophoretic transport through the skin: electrokinetic transport or convective transport. For this purpose, the magnitude of the convective solvent flow was also evaluated by the permeation of (3H) H2O. The interest of pulsed currents for peptide delivery was also investigated and the effect of current density and frequency was studied. RESULTS: AT 2 transport was found to be enhanced 20-fold in comparison to passive permeation and was found to be proportional to the current density with direct currents as with pulsed currents. CONCLUSIONS: Although the flux enhancement of ions during iontophoresis is due principally to the electrical potential gradient, secondary effects such as convective solvent flow contribute also to flux enhancement of peptide delivery. This effect is dependent of physicochemical conditions of formulation.

Angiotensin II↗
PubMed1983

The intramitochondrial volume measured using sucrose as an extramitochondrial marker overestimates the true matrix volume determined with mannitol.

The matrix volume of isolated liver and heart mitochondria has been estimated at various osmolarities and in various osmotic supports using 36Cl- and [14C]sucrose, D-mannitol, D-3-methoxyglucose and choline as extramitochondrial markers. The use of 3-methoxyglucose was only possible at 0 degree C since it entered mitochondria at physiological temperatures. All extramitochondrial markers used gave linear plots of apparent matrix volume against the reciprocal of the osmolarity, but the slope of this plot was greater when sucrose was used than with the other extramitochondrial markers. When extrapolated to infinite osmolarity the mean matrix volume was zero when mannitol was used, but about 0.6 microliter/mg of protein for sucrose and Cl- and -0.4 microliter/mg of protein when choline was used. At physiological osmolarity (about 330 m-osmol) the mean matrix volume of de-energized liver mitochondria in KCl medium estimated using mannitol was 0.46 microliter/mg of protein, whereas that obtained using sucrose was 1.68 microliters/mg of protein. Values in mannitol, choline and sucrose media were similar when mannitol but not sucrose was used as extramitochondrial marker. It is argued that the 3H2O/[14C]mannitol space more accurately reflects the true mitochondrial matrix volume than does the 3H2O/[14C]sucrose space. The consequences of this for measurements of the protonmotive force and the intramitochondrial concentration of metabolites are discussed.

3-O-Methylglucose↗
PubMed2004

Plasmodium induces swelling-activated ClC-2 anion channels in the host erythrocyte.

Intraerythrocytic growth of the human malaria parasite Plasmodium falciparum depends on delivery of nutrients. Moreover, infection challenges cell volume constancy of the host erythrocyte requiring enhanced activity of cell volume regulatory mechanisms. Patch clamp recording demonstrated inwardly and outwardly rectifying anion channels in infected but not in control erythrocytes. The molecular identity of those channels remained elusive. We show here for one channel type that voltage dependence, cell volume sensitivity, and activation by oxidation are identical to ClC-2. Moreover, Western blots and FACS analysis showed protein and functional ClC-2 expression in human erythrocytes and erythrocytes from wild type (Clcn2(+/+)) but not from Clcn2(-/-) mice. Finally, patch clamp recording revealed activation of volume-sensitive inwardly rectifying channels in Plasmodium berghei-infected Clcn2(+/+) but not Clcn2(-/-) erythrocytes. Erythrocytes from infected mice of both genotypes differed in cell volume and inhibition of ClC-2 by ZnCl(2) (1 mm) induced an increase of cell volume only in parasitized Clcn2(+/+) erythrocytes. Lack of ClC-2 did not inhibit P. berghei development in vivo nor substantially affect the mortality of infected mice. In conclusion, activation of host ClC-2 channels participates in the altered permeability of Plasmodium-infected erythrocytes but is not required for intraerythrocytic parasite survival.

Animals↗
PubMed1993

Expression of multiple water channel activities in Xenopus oocytes injected with mRNA from rat kidney.

To test the hypothesis that renal tissue contains multiple distinct water channels, mRNA prepared from either cortex, medulla, or papilla of rat kidney was injected into Xenopus oocytes. The osmotic water permeability (Pf) of oocytes injected with either 50 nl of water or 50 nl of renal mRNA (1 microgram/microliter) was measured 4 d after the injection. Pf was calculated from the rate of volume increase on exposure to hyposmotic medium. Injection of each renal mRNA preparation increased the oocyte Pf. This expressed water permeability was inhibited by p-chloromercuriphenylsulfonate and had a low energy of activation, consistent with the expression of water channels. The coinjection of an antisense oligonucleotide for CHIP28 protein, at an assumed > 100-fold molar excess, with either cortex, medulla, or papilla mRNA reduced the expression of the water permeability by approximately 70, 100, and 30%, respectively. Exposure of the oocyte to cAMP for 1 h resulted in a further increase in Pf only in oocytes injected with medulla mRNA. This cAMP activation was not altered by the CHIP28 antisense oligonucleotide. These results suggest that multiple distinct water channels were expressed in oocytes injected with mRNA obtained from sections of rat kidney: (a) CHIP28 water channels in cortex and medulla, (b) cAMP-activated water channels in medulla, and (c) cAMP-insensitive water channels in papilla.

4-Chloromercuribenzenesulfonate↗
PubMed1967

Determination of extracellular space in amphibian muscle.

The volumes of distribution of inulin and dextran in the sartorius, stomach, and cardiac muscle of the frog agree rather closely. That these spaces represent the volume of extracellular water is supported by the observation that efflux of sucrose can be divided into a fast and a slow phase and that the fast-moving fraction corresponds closely with inulin space determined in the same muscle. These and other findings confirm that sugars and related substances penetrate slowly into part of the fiber water and that, therefore, their volume of distribution does not accurately represent the volume of extracellular water. The kinetics of efflux of sucrose is consistent with the assumption that the movement of sugars is determined by the resistance of the cell surface as well as by internal diffusion. In connective tissue, sucrose and inulin are excluded only from a small part of the total water.

Animals↗
PubMed1971

An analysis of unstirred layers in series with "tight" and "porous" lipid bilayer membranes.

The present experiments were designed to evaluate the effective thickness of the unstirred layers in series with native and porous (i.e., in the presence of amphotericin B) lipid bilayer membranes and, concomitantly, the respective contributions of membranes and unstirred layers to the observed resistances to the diffusion of water and nonelectrolytes between aqueous phases. The method depended on measuring the tracer permeability coefficients for the diffusion of water and nonelectrolytes (P(DDi), cm sec(-1)) when the aqueous phase viscosity (eta) was increased with solutes having a unity reflection coefficient, such as sucrose or dextran. The effective thickness of the unstirred layers (alpha(t), cm) and the true, or membrane, permeability coefficients for diffusion of water and nonelectrolytes (P(mmi), cm sec(-1)) were computed from, respectively, the slope and intercept of the linear regression of 1/P(DDi) on eta. In both the native and porous membranes, alpha(t) was approximately 110 x 10(-4) cm. The ratio of P(f), the osmotic water permeability coefficient (cm sec(-1)) to P(mmH2O) was 1.22 in the native membranes and 3.75 in the porous membranes. For the latter, the effective pore radius, computed from Poiseuille's law, was approximately 5.6 A. A comparison of P(mmi) and P(DDi), indicated that the porous membranes accounted for 16, 25, and 66% of the total resistance to the diffusion of, respectively, H(2)O, urea, and glycerol, while the remainder was referable to the unstirred layers.

Amphotericin B↗
PubMed1977

Effects of cytochalasin B and dimethylsulphoxide on isosmotic fluid transport by rabbit gall-bladder in vitro.

1. Net fluid transport rate, transepithelial ohmic resistance and potential difference (p.d.), and unidirectional fluxes of Na+ were measured in rabbit gall-bladder preparations in vitro exposed on both sides to Ringer solutions of identical electrolyte composition. 2. Bilateral application of 1% dimethylsulphoxide (DMSO), the solvent for cytochalasin B, rapidly and reversibly depressed net fluid transport rate by 15% and increased the lumen positive p.d. by 1-5-2-0 mV. Resistance did not change significantly. These effects of DMSO were shown to be non-specific osmotic effects. 3. Cytochalasin B (10(-5)M) applied bilaterally caused: (a) a progressive inhibition of net fluid transfer rate to 40-50% of its control value within 60 min; the effect was partly reversible within 60 min and independent of the substrates glucose, glutamate and pyruvate; (b) a progressive depression of the mucosal-to-serosal Na+ flux within the first 30 min with no further change in the flux during the following 30 min of exposure to cytochalasin B; the effect was partly reversible within 70 min; (c) a rapid but moderate increase in the passive serosal-to-mucosal Na+ flux, which continued to increase gradually during the entire 60 min period of exposure to cytochalasin B; the effect was completely reversible within 70 min; (d) a prompt drop in ohmic resistance (30%) and p.d. (40%) with no further changes in these parameters during the following 60 min of exposure to cytochalasin B. The effect on resistance was partly reversible within 90 min; the effect on p.d. was completely reversible within 30 min. 4. The results are interpreted to indicate an early inhibitory action of cytochalasin B on the active transcellular pump mechanism and to suggest a cytochalasin B-mediated progressive increase in cell membrane permeability to sodium resulting ultimately in a highly leaky epithelium. The results are compatible with the concept that a mechanochemical process is involved in isosmotic transcellular transport of fluid across low-resistance epithelia.

Animals↗
PubMed2002

Quantification of lung microvascular injury with ultrasound.

Quantification of water and solute exchange rates across the lung microvascular barrier (LMB) may be an important early-warning indicator of pulmonary microvascular diseases such as acute respiratory distress syndrome. Our objective was to determine the degree to which osmotic water movement across the LMB induced by injection of hypertonic solutions of NaCl and glucose could be detected downstream from the lung with a specialized ultrasonic velocity (USV) transducer manufactured by Transonic Systems. We hypothesized that mathematical modeling of the osmotic transients (OT) would yield estimates of osmotic exchange parameters that were sensitive to microvascular injury. Two groups of six dogs were studied under baseline conditions and after injury with high dose (HD) or low dose (LD) oleic acid. Osmotic conductances (sigmaK(1), sigmaK(2)), and volumes (V(1), V(2)) of two extravascular spaces were estimated by fitting the mathematical model to the OT data. HD results (mean +/- standard error) indicated a significant decrease (by paired t test) in sigmaK(1) from 1.59 +/- 0.09 to 1.04 +/- 0.015 [ml h(-1) (mosm/l)(-1) g(-1) WLW)], an increase in sigmaK(2) from 0.20 +/- 0.08 to 0.32 +/- 0.12 [ml h(-1) (mosm/l)(-1) g(-1)], and a significant increase in V2 from 23.26 +/- 2.51 to 78.0 +/- 15.23 (ml) for NaCl injections. LD V2 estimated from NaCl increased significantly from 21.57 +/- 2.15 to 37.59 +/- 2.36 (ml), sigmaK2 increased from 0.09 +/- 0.03 to 0.17 +/- 0.04 and no significant change in sigmaK(1) was found. Baseline glucose sigmaK(1), sigmaK(2), and V1 in the LD series were 2.08 +/- 0.18, 0.64 +/- 0.19 [ml h(-1) (mosm/l)(-1) g(-1)] and 13.08 +/- 1.89 (ml), respectively, and did not change significantly with injury. We conclude that OT data measured by USV is a sensitive and informative indicator of LMB osmotic properties, and may be useful for quantification of LMB permeability changes due to acute injury. We further conclude that V(1) represents microvascular endothelial volume and V(2) is an estimate of interstitial volume.

Animals↗
PubMed2001

[Diagnostic significance of evaluating erythrocyte membrane permeability as an intoxication syndrome criterion].

Twenty-five patients with pyoinflammatory maxillofacial diseases treated in an inpatient setting in the Regional Dentistry Clinic of Krasnodar and 8 healthy volunteers were examined. After opening and draining of the purulent focus the patients were divided into 2 groups. Group 1 consisted of 21 patients treated by intravenous 0.04% sodium hypochlorite (SHC) and intravenous infusions of SHC-oxidized autoblood for 2-3 days. Group 2 (6 pts) was treated by intravenous infusions of SHC-oxidized autoblood for 6 days. The criteria of intoxication were erythrocyte resistance tests in hypotonic sodium chloride and at different concentrations of urea in isotonic medium. A new method for evaluating erythrogram deviations from reference values is proposed, which helps adequately assess the severity of intoxication.

Adolescent↗
PubMed1984

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.

Body Water↗