Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Membrane Fluidity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 487 records · Page 27Linked to original sources
PubMed1990

Evidence that plasma membrane fluidity of isolated hepatocytes is modified by exposure to microtubule-depolymerizing drugs.

The role of microtubules on membrane fluidity has been investigated on freshly isolated whole rat hepatocytes prepared by the perfusion method and exposed either to the microtubule-depolymerizing drugs colchicine and vincristine or to beta-lumicolchicine, a colchicine analog deprived of biological activity. Exposure of hepatocytes to 6.3 microM colchicine or to 3.0 microM vincristine led to a significant decrease of membrane fluidity as measured by fluorescence polarization of trimethylammoniodiphenylhexatriene (TMA-DPH). No changes were observed in cells exposed to 10.0 microM beta-lumicolchicine. These observations support the hypothesis that the microtubular system plays a role in the modulations of physico-chemical properties of the plasma membrane.

Animals↗
PubMed1996

Plasma membrane fluidity of keratinocytes of normal and psoriatic skin: a study using fluorescence anisotropy of trimethylammoniumdiphenylhexatriene (TMA-DPH).

The aim of this study was to investigate plasma membrane fluidity in human keratinocytes using fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) and its cationic derivative 1-[4-(trimethylamino)-phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH). Keratinocytes from normal or psoriatic skin were isolated using trypsin-EDTA or dispase. In keratinocytes isolated from normal skin, TMA-DPH anisotropy values were higher than those observed using DPH; the difference must be related to the different localization of the two probes. In fact, DPH in whole cells localizes in plasma as well as intracellular membranes, yielding an average value of fluidity, while the cationic derivative TMA-DPH resides in the plasma membrane of the whole cells for a sufficient time for anisotropy measurements. Moreover, it has to be considered that plasma membrane is more ordered than intracellular membranes. The kinetics of incorporation of TMA-DPH was similar in keratinocytes isolated using trypsin-EDTA and those isolated using; dispase, however, the fluorescence anisotropy values were lower in keratinocytes isolated with dispase (0.260 +/- 0.01 vs 0.270 +/- 0.01, p = 0.029). This difference is probably related to modifications of lipid-protein interactions after trypsin treatment. Since no damage to plasma membrane after incubation with dispase seems to have been reported, we decided to use this separation procedure to study plasma membrane fluidity in psoriasis, a human pathological condition characterized by excessive cell proliferation and incomplete differentiation. Lower anisotropy values (0.260 +/- 0.01 vs 0.270 +/- 0.01, p = 0.001), indicating an increase in fluidity, were observed in keratinocytes isolated from skin of psoriatic patients than in epidermal cells isolated from normal human skin. We suggest that the measurement of fluorescence anisotropy in living cells is a convenient and useful tool to study membrane fluidity in human keratinocytes isolated from normal and diseased skin. Its application represents a technical advance because plasma membrane fluidity can be measured using very limited amounts of tissue, as obtained from biopsies.

Diphenylhexatriene↗
PubMed1983

Effect of ionic strength on the membrane fluidity of rabbit intestinal brush-border membranes. A fluorescence probe study.

The effect of ionic strength on the fluidity of rabbit intestinal brush-border membranes has been studied using two fluorescence probes, pyrene and 1-anilino-8-naphthalene sulfonate (ANS). The imposition of a potential gradient on the pyrene-probed membrane vesicles (out greater than in) with increasing NaCl concentration in the medium resulted in a marked enhancement of the excimer formation efficiency, accompanied by a decrease in the ratio of fluorescence intensities of the probe at 392 and 375 nm. Fluorescence polarization of the pyrene-membrane complex is independent of temperature in the absence of salts, while it is dependent on temperature from 10 to 47 degrees C in the presence of salts, as shown by the thermal Perrin plots of polarization. It has been demonstrated that there is a linear relationship between the changes in the pyrene excimer formation efficiency in the membranes and of the values of the binding parameters of ANS for the membranes. From these results, it is suggested that the lipid phase of the membranes becomes more fluid by shielding negatively charged groups of the membrane surface and that there is a fairly close correlation between the membrane organization and the membrane surface charge density.

Anilino Naphthalenesulfonates↗
PubMed1987

Evaluation of membrane fluidity effects and enzyme activities alterations in adriamycin neurotoxicity.

Adriamycin (ADR) increased the lipid fluidity of dog brain synaptosomal plasma membranes (SPM) labeled with 1,6-diphenyl-1,3,5-hexatriene (DPH), as indicated by the steady-state fluorescence anisotropy [(ro/r)-1]-1. Arrhenius-type plots of [(ro/r)-1]-1 indicated that the lipid phase separation of the membrane at 23.3 +/- 1.2 degrees was perturbed by ADR such that the temperature was reduced to 16.2 +/- 1.1 degrees. Arrhenius plots of (Na+ + K+)-stimulated ATPase activity exhibited a break point at 22.8 +/- 1.1 degrees in control SPM which was reduced to 15.8 +/- 1.0 degrees in ADR treated SPM, suggesting differences in the interaction of (Na+ + K+)-stimulated ATPase with lipids between ADR treated and untreated SPM. (Na+ + K+)-stimulated ATPase and Ca2+-stimulated ATPase activities were increased at a concentration range 10(-18)-10(-15) M of ADR; higher concentrations (up to 10(-7) M), however, led to a progressive inhibition of the enzyme activities. The allosteric properties of SPM-bound (Na+ + K+)-stimulated ATPase by fluoride (F-) (as reflected by changes in the Hill coefficient) were modulated by ADR whereas those of SPM-bound acetylcholinesterase remained unaffected. We propose that ADR achieves these effects through asymmetric perturbations of the membrane lipid structure and that changes in membrane fluidity may be an early key event in ADR induced neurotoxicity.

Acetylcholinesterase↗
PubMed2000

Influence of membrane fluidity modifiers on lysosomal osmotic sensitivity.

Since lysosomes are prone to osmotic lysis, we have examined the correlation between their physical state and sensitivity to osmotic challenge, using agents which modify membrane fluidity. The latency loss of beta-hexosaminidase after an incubation in hypotonic sucrose medium was followed under different conditions of membrane fluidity, recorded by steady-state fluorescence anisotropy of 1,6-diphenyl-1,3, 5-hexatriene. Increasing fluidity of the lysosomal membranes with benzyl alcohol (BA) and greater rigidity caused by cholesteryl hemisuccinate (CHS) increased and decreased the enzyme latency loss, respectively. The effects of BA and CHS treatments on osmotic sensitivity were reversible subsequently by reciprocal treatments of the lysosomes with CHS and BA, respectively. The results indicate that the physical state of the membrane does indeed affect lysosomal osmotic stability.

Anesthetics, Local↗
PubMed1996

Influence of equinatoxin II on coronary smooth muscle membrane fluidity.

Equinatoxin II forms pores in artificial as well as in natural phospholipid bylayers. As it also reduces the perfusion through the coronary arteries it seemed reasonable to investigate the interaction of this protein with the plasmalemma of the vascular smooth muscle cells more directly with the patch-clamp method and with EPR using the spin probe methyl ester of 5-doxylpalmitate. In the EPR spectra at least three regions in the membranes were identified with different membrane fluidity. Application of 0.1 microM or 1 microM equinatoxin II increases the portion with the lower membrane fluidity, and irreversibly increases the unspecific membrane conductance. This is compatible with the view that equinatoxin II forms pores in the membrane bilayer.

Animals↗
PubMed1988

Phosphatidylcholine and phosphatidylethanolamine derivatives, membrane fluidity and changes in the lipolytic activity of ram spermatozoa plasma membranes during cryoconservation.

1. A decrease of the alkenyl-acyl derivatives and an increase of the diacyl derivatives of PC and PE were observed after cryoconservation. 2. A diminution of membrane-bound phospholipase A2 activity was observed after cryoconservation. The activity of neutral sphingomyelinase remained unchanged. 3. The enrichment of plasma membranes with DPPC as well as the addition of the cryoprotector of Nagase-Niwa were observed to protect the membranes from fluidization.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1995

Effects of peroxisomal beta-oxidation antagonist on 2',3'-cyclic-nucleotide 3'-phosphohydrolase, membrane lipid compositions, and membrane fluidity in C-6 glial cells.

In order to understand the relationship between peroxisomal dysfunction and clinical manifestations of peroxisomal disorders, the effect of thioridazine, a peroxisomal beta-oxidation antagonist, on the differentiation, membrane lipid composition and membrane fluidity of C-6 glial cells was examined. In our study, induction of 2',3'-cyclic-nucleotide 3'-phosphohydrolase (CNP), which was considered to be a membrane-associated enzyme closely associated with myelination, was inhibited with supplementation of thioridazine, followed by an increase in the relative concentration of longer chain fatty acids in cell membrane lipids, indicating that thioridazine causes impaired differentiation in the glial stem cell system. Membrane fluidity of C-6 glial cells was examined using a fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH). The DPH anisotropy value was decreased in the glial cells treated with thioridazine. These results indicate that the alteration of the membrane lipid composition caused by thioridazine affects the differentiation of glial cells via the changes in membrane properties.

2',3'-Cyclic Nucleotide 3'-Phosphodiesterase↗
PubMed2005

Effect of anti-inflammatory drugs on splenocyte membrane fluidity.

In this study, fluorescence anisotropy measurements were performed using the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene to investigate the effects on membrane fluidity resulting from the interaction between nonsteroidal anti-inflammatory drugs (NSAIDs)-indomethacin, diclofenac, piroxicam, tenoxicam, indoprofen, clonixin, and etodolac-and mouse splenocyte membranes. This study was performed in splenocyte membranes because most of the fluidity studies have been performed in membrane models; thus, clear correlations of the pharmacological action of drugs with molecular effects at the cellular membrane level were lacking. Besides providing a basis for studying the molecular mechanism of pharmacological action of NSAIDs, this research provides a data analysis of steady-state anisotropy measurements, taking into account that the probe itself strongly influences the data given that this problem is usually overlooked. Results show that the anti-inflammatory drugs indomethacin, diclofenac, piroxicam, and tenoxicam increase the membrane fluidity in a concentration-dependent manner. Their order of effectiveness reflected in their respective IC50 values (concentration of each NSAID required to increase the fluidizing effect ratio by 50%) is as follows: tenoxicam>piroxicam>indomethacin>clonixin. For the other drugs, the perturbation in membrane fluidity is not evident under these circumstances.

Animals↗
PubMedDate not supplied

Plasma membrane fluidity in isolated rat hepatocytes: comparative study using DPH and TMA-DPH as fluorescent probes.

The study of membrane fluidity is a rapidly expanding field of research and its interest in hepatology has been stressed recently. The present study is the first report concerned with the determination of membrane fluidity of isolated rat hepatocytes. The data have been compared with those obtained in plasma membrane fractions and subfractions (basolateral or canalicular) derived from homogenates. The fluorescent probes used to measure the fluidity were diphenylhexatriene (DPH) a 'classical' probe, and its derivative trimethylammoniodiphenylhexatriene (TMA-DPH) at 25 degrees C and at 37 degrees C. The values obtained with DPH were lower than those with TMA-DPH, probably due to the localization of the probes in different regions of the phospholipid bilayer. In addition, DPH revealed significant differences in the fluorescence polarization values obtained in isolated hepatocytes compared with membrane fractions, which was in contrast to TMA-DPH, where the respective values were of the same order of magnitude. This behaviour is probably due to the mobility of DPH in the membrane core and its rapid internalization into the cell, whereas TMA-DPH remains anchored for a long time on the cell surface. These findings suggest that TMA-DPH is a better probe than DPH for measuring the fluorescence polarization of whole isolated hepatocytes and that the use of different probes might be of help in exploring different zones of the membrane bilayer.

Animals↗
PubMed2001

[The hypocaloric balanced diet therapy and the supplementation with antioxidant and omega-3: what are the effects on the oxidative balance and erythrocytes membrane fluidity status?].

BACKGROUND: To investigate the effects of a hypocaloric balanced diet therapy and a supplementation with antioxidant and omega-3 polyunsaturated fatty acids on the oxidative balance and erythrocytes membrane fluidity status. METHODS: A randomised, double-blind, placebo-controlled study of the association between a hypocaloric balanced diet therapy and a supplementation with antioxidant and omega-3 was done on 40 women with 25 < BMI < 33. The inclusion criteria were the following: absence of dismetabolic pathologies, of previous hypocaloric diet therapy and/or supplementation and of hormonal treatments. Each subjects consumed a balanced diet with a daily caloric intake equal to: Kcal of basal metabolism (determined by indirect calorimetry) x LAF (1.64) 800 Kcal. At the start and after two months of treatment, the blood chemistry and anthropometrics parameters, the plasmatic reactive oxygen species (ROS) and antioxidant defence levels and erythrocyte membrane fluidity status were measured. RESULTS: The preliminary results of this study show that the weight loss, found in both groups investigated, determines a significant decrease of ROS. Furthermore, the association of the hypocaloric diet with antioxidant and omega-3 polyunsaturated fatty acids caused a significant increase of both plasmatic antioxidant defences and erythrocytes membrane fluidity status. CONCLUSIONS: The correlations found between the above parameters and the blood chemistry and anthropometrics variables suggest that the supplementation with antioxidant and omega-3 polyunsaturated fatty acids could ameliorate the effects of hypocaloric diet on the obesity treatment and may give some clinical benefit through the decrease of the values of atherosclerosis risk factors.

English Abstract↗
PubMed1996

Anesthetic activity of monoketones in mice: relationship to hydrophobicity and in vivo effects on Na+/K+ -ATPase activity and membrane fluidity.

The in vivo anesthetic activity of monoketones in mice was examined in relation to their hydrophobicity and to the in vivo effects on Na+/K+ -adenosine triphosphatase (Na+/K+ -ATPase) activity and membrane fluidity. Anesthetic potency (AD50) of monoketones was determined; AD50 implys the dose required to anesthetize 50% of the animals from the treated group. The n-octanol/water partition coefficient (P) was used as an index of hydrophobicity. Membrane fluidity was determined by using 1,6-diphenyl-1,3,5-hexatriene (DPH) or 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH as fluorescence probes. Log (1/AD50) was the parabolic function of log P, log ((1/AD50) = -0.167(log P)2 + 0.698 log P - 1.365, and the log P that corresponds to the minimum AD50 was estimated to be 2.09. Brain synaptosomes were prepared from mice that were considered anesthetized with each of the 4 monoketones (1.5-fold AD50), methyl n-propyl, methyl n-amyl, methyl 3-methylhexyl and methyl n-octyl ketone. The Na+/K+ -ATPase activity was inhibited by methyl n-propyl ketone alone, membrane DPH fluidity was decreased by each of the 4 monoketones, and membrane TMA-DPH fluidity was decreased by methyl n-propylketone alone. These results suggest an involvement of the decreased DPH fluidity in monoketone-induced anesthesia.

Anesthetics↗
PubMed1995

High membrane fluidity is related to NaCl stress in Candida membranefaciens.

The effect of hypersaline stress on the lipid composition of the salt-tolerant yeast Candida membranefaciens was studied. Fatty acid analyses of the plasma membrane showed a growth phase- and dose-dependent increase in the level of linolenic acid (C18:3) in 1.35 M NaCl-stressed cells. Palmitoleic acid (C16:1) was completely undetectable at all phases of the life cycle. Changes in the levels of other fatty acids were insignificant. The degree of unsaturation of fatty acids in the plasma membranes was higher in presence of 1.35 M NaCl. The fluorescence polarisation value of DPH (1,6-diphenyl- 1,3,5-hexatriene) in the spheroplasts of the stressed cells was lower as compared to the control cells, indicating the fact that a higher membrane fluidity favours osmotic adaptation against NaCl stress. Among different phospholipids, levels of Phosphatidylinositol and Phosphatidylethanolamine were elevated in the salt-adapted cells as compared to their controls. The levels of Phosphatidylcholine and cardiolipin did not change significantly in response to hypersaline stress. The study points out that hypersalinity signals affect the lipid composition which in turn affects the membrane fluidity of C. membranefaciens.

Candida↗
PubMedDate not supplied

Rat synaptic membrane fluidity parameters after intermittent exposures to ethanol in vivo.

Differentiated membrane alterations correlate with the development of functional tolerance or dependence during chronic alcohol intoxication in humans as well as in animals. In animal studies, a single period of continuous exposure was generally used. In humans, the consumption can be more episodic with heavier weekend drinking. How a heavy but intermittent alcohol exposure over 4 weeks affects the synaptic membrane fluidity and sensitivity was examined in male and female adult rats. No differences were seen between membranes from males and females. Alterations were found in the negative polar membrane region probed by TMA-DPH and the sensitivity to acute ethanol was significantly reduced in the DPH (lipid core) and TMA-DPH probed membrane regions. Tolerance to the hypothermic effect of ethanol has developed and could be correlated with the resistance of the membrane lipid core to ethanol. Intermittent exposures to ethanol, as continuous ones, can result in development of functional and membrane tolerance and in specific alterations in the fluidity of the polar part of the membrane, probably in relation with dependence.

Animals↗
PubMed1991

Effect of low-density lipoprotein on endothelial cell membrane fluidity and mononuclear cell attachment.

To determine the effects of prolonged low-density lipoprotein (LDL) exposure in vitro on cultured endothelial cell (EC) lipid dynamics and cellular function, human umbilical vein ECs were incubated in LDL concentrations [cholesterol (Chol) = 240 mg/dl] associated with the premature development of atherosclerosis. After 4 days of incubation, cells were examined for changes in cellular lipid composition and for membrane fluidity. Results indicate that LDL-EC have increased Chol content (control EC vs. LDL-EC = 22.4 +/- 5.26 vs. 38.9 +/- 0.24 nmol/10(6) cells, P less than 0.05) and cellular Chol-to-phospholipid ratio (0.61 +/- 0.10 vs. 1.21 +/- 0.10 mol/mol, P less than 0.05). Augmentation of EC Chol content was accompanied by a marked decrease in EC cellular membrane fluidity as assessed by fluorescence polarization (anisotropy, r values, 0.172 +/- 0.019 vs. 0.226 +/- 0.014, P less than 0.0001). LDL-induced changes in EC lipid dynamics were associated with enhanced EC binding of monocytes (P less than 0.05) and U937 cells (P less than 0.01). Both LDL-induced decreases in membrane fluidity and enhanced attachment of mononuclear cells were reversed to control levels following a 2-min incubation of LDL-EC with the membrane mobility agent, A2C. These data therefore suggest that LDL-induced modulations in lipid dynamics play an important role in perturbation of EC function.

Cell Adhesion↗
PubMed1990

Alterations in membrane fluidity during keratinocyte differentiation measured by fluorescence polarization.

The epidermis shows a distinctive pattern of differentiation wherein keratinocytes proliferate in the basal cell layer and mature into spinous and granular cells. Using a discontinuous density-gradient centrifugation method, guinea-pig keratinocytes were separated into high (HDF), intermediate (IDF), and low (LDF) density fractions. Morphological and flow cytometrical observations demonstrated that HDF, IDF, and LDF were basal, spinous, and granular cell-rich fractions, respectively. Membrane fluidity of the fractionated keratinocytes was measured by diphenylhexatriene fluorescence polarization. Polarization (p)-value of keratinocytes was negatively correlated with temperature. At each temperature, HDF cells showed a lower p-value than IDF or HDF cells except at 40 degrees C. Since a low p-value indicates a high degree of Brownian motion, membrane fluidity is higher in basal cells and lower in spinous and granular cells. Our results indicate that membrane fluidity of guinea-pig keratinocytes decreases during their maturation.

Animals↗
PubMed1984

Modulation of canine myocardial sarcolemmal membrane fluidity by amphiphilic compounds.

Amphiphilic moieties such as lysophosphoglycerides and long-chain acyl carnitines accumulate in ischemic myocardium and potentially contribute to the sequelae of myocardial ischemia. To characterize alterations in membrane molecular dynamics produced by amphiphilic compounds, highly purified preparations of canine myocardial sarcolemma were spin-labeled with paramagnetic probes (5-, 12-, or 16-doxyl stearate), and alterations produced by amphiphilic compounds were quantified by electron spin resonance spectroscopy. Incorporation of 1.5, 3, or 6 mol % palmitoyl lysophosphatidylcholine resulted in a decrease of the order parameter of 16-doxyl stearate from 0.164 to 0.161, 0.155, and 0.145, respectively. Similar increases in membrane fluidity in the interior of the bilayer were present when palmitoyl lysophosphatidylethanolamine, L-palmitoyl carnitine, and platelet-activating factor were incorporated into sarcolemma. In contrast, incubation of sarcolemma with lysophosphatidylcholine did not result in significant change of the order parameter of 5-doxyl stearate, even at 6 mol %, demonstrating that lysophosphatidylcholine increases the transmembrane fluidity gradient. Sarcolemma treated with phospholipase A2 exhibited a time-dependent decrease in the rotational correlation time and order parameter when lysophospholipids constituted a small amount (6%) of sarcolemmal phospholipids. Furthermore, the effects of lysophosphatidylcholine were not dependent upon its physical state, since bilayers composed of gramicidin and lysophosphatidylcholine resulted in similar increases in membrane fluidity as micellar lysophosphatidylcholine. The results suggest that alterations in sarcolemmal molecular dynamics are one mechanism through which amphiphilic moieties mediate their multiple effects. Such alterations could contribute to the electrophysiological and biochemical sequelae of myocardial ischemia.

Animals↗
PubMed1984

Alteration by prolactin of surface charge and membrane fluidity of rat 13762 mammary ascites tumor cells.

Intraperitoneal injection of ovine prolactin (100 micrograms/d) in Fischer 344 rats bearing transplantable 13762 mammary ascites tumor (MAT) cells modifies the surface charge density and membrane fluidity of the tumor cells. In each of five experiments the mean electrophoretic mobility (epm) of MAT cells taken from prolactin-treated rats was significantly lower than that of cells from nonhormone-treated controls. Prolactin concentrations were increased in vivo by (a) direct intraperitoneal injection of ovine prolactin; (b) subcutaneous implantation of diethylstilbestrol-containing silastic capsules to produce pituitary prolactin secreting tumors; or (c) a single subcutaneous injection of polyestradiol phosphate, a long-acting estrogen. In an effort to establish that the prolactin effect was a direct one, two in vivo protocols were used: (a) MAT cells were coincubated with anterior pituitary halves obtained from nontumor-bearing littermates; or (b) rat or ovine prolactin was added to serum-free culture media containing MAT cells. In both protocols, the epm of the prolactin-treated cells was significantly lower. The isoelectric focusing pH of whole cells was increased by prolactin treatment from 4.93 to 5.12, consistent with a reduction in the number of surface carboxyl groups. The fluidity of membranes of treated cells was drastically increased, as measured by spin-label probe rotation rates. These combined results imply that the hormone exerts its effect by stimulating events in the cell that lead to a reduction of the average density of carboxylic acid residues on the tumor cell surface.

Animals↗