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At least 55 records · Page 3Linked to original sources
PubMed1987

Adenovirus-dependent changes in cell membrane permeability: role of Na+, K+-ATPase.

Adenovirus-dependent release of choline phosphate from KB cells at pH 6.0 was partially blocked by ouabain. In K+-containing medium, maximum inhibition of release was obtained by 10(-5) M ouabain and half-maximal inhibition was achieved by about 0.5 X 10(-6)M ouabain. Ouabain did not block either the binding or the uptake of adenovirus by KB cells. Without K+, about 25% of cell-associated choline phosphate was released by adenovirus, whereas with 1 mM K+ about 50% was released. This activation by K+ was blocked by 0.1 mM ouabain. HeLa cells behaved like KB cells, but a mutant of HeLa cells resistant to ouabain (D98-OR) released much lower amounts of choline phosphate in response to human adenovirus type 2 (Ad2). Wild-type D98-OR cells bound nearly the same amount of adenovirus as did normal HeLa cells. Ad2 also increased the activity of Na+,K+-ATPase in KB cells, with maximum activation at 50 micrograms of Ad2 per ml. In D98-OR cells, Ad2 failed to activate Na+,K+-ATPase activity. Ad2-dependent lysis of endocytic vesicles (receptosomes) was assayed by measuring Ad2-dependent enhancement of epidermal growth factor-Pseudomonas exotoxin toxicity. This action of adenovirus was increased when K+ was present in the medium. Under the conditions used, K+ had no effect on the amount of Ad2 or epidermal growth factor taken up by the cells. On the basis of these results, it is suggested that Ad2-dependent cellular efflux of choline phosphate and adenovirus-dependent lysis of receptosomes may require Na+,K+-ATPase activity.

Adenoviruses, Human↗
PubMed2006

Nitric oxide red blood cell membrane permeability at high and low oxygen tension.

Red blood cell (RBC) encapsulated hemoglobin in the blood scavenges nitric oxide (NO) much more slowly than cell-free hemoglobin would. Part of this reduced NO scavenging has been attributed to an intrinsic membrane barrier to diffusion of NO through the RBC membrane. Published values for the permeability of RBCs to NO vary over several orders of magnitude. Recently, the rate that RBCs scavenge NO has been shown to depend on the hematocrit (percentage volume of RBCs) and oxygen tension. The difference in rate constants was hypothesized to be due to oxygen modulation of the RBC membrane permeability, but also could have been due to the difference in bimolecular rate constants for the reaction of NO and oxygenated vs deoxygenated hemoglobin. Here, we model NO scavenging by RBCs under previously published experimental conditions. A finite-element based computer program model is constrained by published values for the reaction rates of NO with oxygenated and deoxygenated hemoglobin as well as RBC NO scavenging rates. We find that the permeability of RBCs to NO under oxygenated conditions is between 4400 and 5100 microm s(-1) while the permeability under deoxygenated conditions is greater than 64,000 microm s(-1). The permeability changes by a factor of 10 or more upon oxygenation of anoxic RBCs. These results may have important implications with respect to NO import or export in physiology.

Cell Membrane Permeability↗
PubMed1993

Multiparameter flow cytometric analysis of a novel cytotoxin (factor 2) induced tumor cell membrane permeability.

An improved twin-probe multiparameter flow cytometric technique was applied to examine a novel cytotoxin, Factor (F2), induced tumor cell permeability. Ability to retain preloaded intracellular bis-carboxyethyl carboxyfluorescein (BCECF, green fluorescence) and to exclude extracellular propidium (red fluorescence) was measured simultaneously with forward and right-angle scatter. In addition to the two expected cell populations which were stained green negative, red positive ("membrane-damaged" and "non-viable", Region 2), and green positive, red negative ("membrane intact" and "viable", Region 3), a third population was seen which fluoresced neither green nor red and displayed intermediate light scatter characteristics (Region 1). K562 cells progressed from Region 3 to Region 1, and then from Region 1 to Region 2 after treatment with F2. These results suggest that sequential changes in membrane structure lead to increased permeability, first with respect to intracellular BCECF and then in turn to extracellular propidium. Flow cytometric changes caused by F2 were detectable 10 min after treatment with 2.5 U/ml of F2, and 5 min after 10 or 40 U/ml of F2. Flow cytometric analysis showed that F2-induced tumor cell lysis and growth inhibition were accompanied by rapid alternations in tumor cell membrane permeability. Flow cytometric analysis also distinguished F2 cytotoxicity from phorbol myristate acetate (PMA) associated cytotoxicity to K562 cells and determined that F2 produced spontaneously or induced by PMA and/or ciprofloxacin had a similar ability to induce tumor cell membrane permeability change.

Cell Membrane Permeability↗
PubMed1978

Changes in the lipid composition of ripening banana fruits and evidence for an associated increase in cell membrane permeability.

The content of total lipid in banana fruit pulp tissue remained constant during the climacteric rise induced by applied ethylene. The relative proportions of neutral lipid, glycolipid and phospholipid did not change. However, the fatty acid composition of the lipid did change during ripening. This change was confined largely to the phospholipid fraction, in which there was an increase in the proportion of linolenic acid and a decrease in the proportion of linoleic acid. The net result was an increase in total unsaturation of the fatty acids in the phospholipid fraction. Measurements of spin label motion in liposomes prepared from banana phospholipids showed that the motion and fluidity of bilayer lipids increased during ripening of the fruit from which the liposomes were prepared, probably as a result of increased lipid unsaturation during ripening. Since increases in membrane fluidity are accompanied by increases in the passive permeability to small molecules in a number of membrane systems, it is suggested that the increased leakage which has been previously demonstrated in ripening banana fruit tissue is due to increases in the permeability of at least some cell membranes.

Cell Membrane Permeability↗
PubMed1996

Inhibition of FGF-stimulated phosphatidylinositol hydrolysis and neurite outgrowth by a cell-membrane permeable phosphopeptide.

BACKGROUND: Activated receptor tyrosine kinases bind downstream effector molecules with high affinity. Provided that they can be introduced into cells, peptides corresponding to these high-affinity sites should be able to compete for the interaction and thereby inhibit specific signal transduction cascades. The high-affinity binding site for phospholipase C gamma (PLCgamma) on the activated fibroblast growth factor receptor (FGFR) is centred around the tyrosine at position 766 (766Tyr), and peptides corresponding to this site inhibit PLCgamma binding to the receptor in vitro. A 16 amino-acid peptide from the third helix of the Antennapedia homeodomain protein has recently been shown to be able to act as an internalization vector that can deliver other peptides into cells. Here, we have designed a peptide that contains both the internalization sequence and the FGFR high-affinity binding site for PLCgamma, and tested it in cultures of cerebellar neurons for its ability to inhibit the activation of PLCgamma by basic FGF. RESULTS: The peptide containing the FGFR high-affinity binding site for PLCgamma inhibited phospholipid hydrolysis stimulated by basic FGF with a maximal effect at 1 microg ml-1. Phosphorylation of 766Tyr was required for this effect. The phosphorylated peptide had no effect on phospholipid hydrolysis stimulated by platelet-derived growth factor, neurotrophin-3 and bradykinin. The phosphorylated peptide also inhibited neurite outgrowth stimulated by FGF, but had no effect on neurite outgrowth stimulated by agents that activate the FGFR signal transduction cascade downstream from the activation of PLCgamma. CONCLUSIONS: Cell-permeable peptides can be designed that inhibit the function of receptor tyrosine kinases. In this context we have developed a peptide that prevents the FGFR from activating PLCgamma, and have used this peptide to obtain the first direct evidence that activation of PLCgamma is required for the neurite outgrowth response stimulated by basic FGF.

Amino Acid Sequence↗
PubMed2000

A two-parameter model of cell membrane permeability for multisolute systems.

A two-parameter model of cell osmotic response (F. W. Kleinhans, 1998, Cryobiology 37, 271-289) is expanded for multisolute systems. The cell water volume W and intracellular osmolalities of N solutes are related as W[1 + L(p)RTSigma(N)(i=1)(M(i)/P(i))] = W(0)[1 + L(p)RTSigma(N)(i=1)(M(0)i)/P(i))], where M(i) is the intracellular osmolality of the ith solute (i = 1 ellipsis N), P(i) is the membrane permeability of the ith solute, L(p) is the membrane hydraulic conductivity, R is the gas constant, T is the absolute temperature, and the subscript "0" denotes the initial values at time zero. The above formula allows calculating the final (equilibrium) volume when all entities are permeable. Simple algebraic expressions for calculation of the number and magnitude of transient maximum volume excursions are presented. These simple expressions can all be calculated by hand on a pocket calculator. Practical examples of one-, two-, and three-solute systems are discussed. Special attention has been given to situations when systems contain an impermeable component. All formulas are simple to use for optimization of variety of cryobiological protocols. Application of the theory for optimization of addition and dilution of a permeable cryoprotectant is also discussed.

Animals↗
PubMed2001

Clostridium perfringens epsilon toxin induces a rapid change of cell membrane permeability to ions and forms channels in artificial lipid bilayers.

Epsilon toxin is a potent toxin produced by Clostridium perfringens types B and D, which are responsible for a rapidly fatal enterotoxemia in animals. One of the main properties of epsilon toxin is the production of edema. We have previously found that epsilon toxin causes a rapid swelling of Madin-Darby canine kidney cells and that the toxin does not enter the cytosol and remains associated with the cell membrane by forming a large complex (Petit, L., Gibert, M., Gillet, D., Laurent-Winter, C., Boquet, P., and Popoff, M. R. (1997) J. Bacteriol. 179, 6480-6487). Here, we report that epsilon toxin induced in Madin-Darby canine kidney cells a rapid decrease of intracellular K(+), and an increase of Cl(-) and Na(+), whereas the increase of Ca(2+) occurred later. The entry of propidium iodide that was correlated with the loss of cell viability monitored by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test indicates that epsilon toxin formed large pores. In artificial lipid bilayers, epsilon toxin caused current steps with a single-channel conductance of 60 pS in 100 mm KCl, which represented general diffusion pores. The channels were slightly selective for anions, but cations could also penetrate. Epsilon toxin formed wide and water-filled channels permeable to hydrophilic solutes up to a molecular mass of at least 1 kDa, which probably represents the basic mechanism of toxin action on target cells.

Animals↗
PubMed1991

[Free radical oxidation of red blood cell membrane lipid structures as a trigger mechanism of an increase in red blood cell membrane permeability during blood coagulation in vitro].

The study of venous blood samples from 50 clinically normal subjects has shown that free radical oxidation of red blood cell membrane lipid structure induced by the blood sample contact with atmospheric oxygen serves a trigger rising the membrane permeability during blood coagulation in vitro. Activation of endogenous phospholipase A2 is a process dependent on the increase of intraerythrocytic concentration of calcium ions.

Blood Coagulation↗
PubMed1994

[Changes in the cell membrane permeability of chick myoblasts in primary culture when in contact with rat neutrophils].

The reaction of chicken myoblasts in competent primary culture during their contact with activated rat neutrophils was evaluated. In the incubation medium dynamics of activities were defined for proteinases and creatine kinase, protein content, as well as for DNA and protein marked precursor increase. An increase in myoblast membrane permeability has been revealed. It is shown that the culture is a sensitive model for investigation of physiological interaction of neutrophils with muscle tissue cells.

Animals↗
PubMed1982

[Highly permeable contacts and the electrical characteristics of normal liver tissue and hepatomas. II. A structural model and calculation of the cell membrane permeability of induced mouse hepatomas].

The values of specific resistances of non-junctional (Rm) and junctional (Rj) membranes of mouse induced hepatoma cells were calculated with the aid of the syncytium theory equations and on the basis of the previously measured input resistances and electrotonic potential spread curves. A three-dimensional model with cable element length equal to two cell diameters, with the length constant value of 600 mkm, and with three contacts per cell was used for calculations. For this model, Rm and Rj were found to be 3300-5600 Ohm . cm2 and 2 . 10(-2) Ohm . cm2, respectively. For the three-dimensional model of normal liver, Rm and Rj amounted to 2400-7200 Ohm . cm2 and 6.5 . 10(-2) Ohm . cm2, respectively.

Animals↗
PubMed1993

Alterations in cell membrane permeability by the lentivirus lytic peptide (LLP-1) of HIV-1 transmembrane protein.

Previously we reported that synthetic peptide homologs of an amphipathic region (designated the lentivirus lytic peptide, or LLP-1) near the carboxy terminus of HIV-1 transmembrane protein (TM) were toxic for both prokaryotic and eukaryotic cells when added exogenously to cell cultures. We postulated that these peptides may exert their toxic effects in much the same manner as natural cytolytic peptides such as magainins, cecropins, and melittin by forming pores through cellular membranes. Here we show the results of 51Cr-release assays and membrane flux measurements of peptide treated cells that support our hypothesis. We have also tested a limited panel of LLP-1 peptide analogs in these assays and found that relatively minor alterations in peptide charge or amphipathicity in the parent HIV LLP-1 sequence resulted in total loss of membrane perturbative properties. These results demonstrate that the peptide homolog of HIV-1 LLP-1 can indeed perturb membranes by forming pores of defined size in cytoplasmic membranes. Furthermore, the analog studies described here reveal that the amphipathy and high positive charge of this protein segment are required for the membrane perturbative properties.

Amino Acid Sequence↗