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PubMed1986

Absence of effects on platelet membrane fluidity by antibiotics in ESR spectra.

The effect of several antibiotics on rat platelet membrane fluidity was examined by ESR spectrometry using 5-doxyl stearate as the spin probe. Latamoxef, cefamandole, cefotaxime and carbenicillin had negligible effects on the order parameters, the indices of membrane fluidity, of platelet-rich plasma or washed platelets at high concentrations that would inhibit ADP-induced rat platelet aggregation in vitro. A further in vivo study with one of these antibiotics, latamoxef, showed no significant effect on the fluidity based on ESR data.

Adenosine Diphosphate↗
PubMed1997

Platelet membrane fluidity and intraplatelet Ca2+ mobilization are affected in uraemia.

In present investigations, platelet membrane fluidity and intraplatelet Ca2+ mobilization were analysed in uraemic platelets by fluorescence techniques. Thirteen non-dialyzed uraemic patients and 16 control subjects were examined. Anisotropy of DPH-probe, measured at 37 degrees C, was significantly higher in control (0.2236 +/- 0.0050) than in uraemic platelets (0.1969 +/- 0.0082; p < 0.01). There was no difference between control (109.8 +/- 6.0 nM) and uraemic platelets (100.0 +/- 7.3 nM) when the basal [Ca2+]i in resting platelets was determined. Activation of platelets by ADP (12.5 microM) or by thrombin (0.1 U/ml) resulted in an increase in [Ca2+]i. It was significantly higher (p* < 0.003 for ADP and p* < 0.009 for thrombin, respectively) in control platelets (383.6 +/- 56.3 nM and 2031.0 +/- 298.8 nM, respectively) than in uraemic ones (191.0 +/- 21.3 nM and 838.7 +/- 144.1 nM, respectively). The amount of released Ca2+ was higher in control platelets activated by both ADP and thrombin (157.6 +/- 21.4 nM and 409.3 +/- 71.0 nM, respectively) than in uraemic platelets (76.7 +/- 15.7 nM and 203.0 +/- 29.3 nM, respectively) and the differences were significant (p < 0.01 and p* < 0.01, respectively). These results indicate an abnormal intracellular Ca2+ mobilization in uraemic platelets. Both increased membrane fluidity and decreased Ca2+ mobilization should be considered as a possible reason of reduced fibrinogen receptor exposure on uraemic platelets.

Adenosine Diphosphate↗
PubMed1984

Adenylate cyclase and membrane fluidity. The repressor hypothesis.

The relationships between membrane fluidity as induced by drug addition and the stimulation of adenylate cyclase by hormones (mainly catecholamines), GTP, Gpp(NH)p and NaF are reviewed. In particular, the data corresponding to pigeon erythrocyte membranes are reviewed and compared with other data published in the literature. A brief summary of the theories involved in fluidity measurements and their significance at the molecular level is also given for anisotropy of fluorescence and electron spin resonance. One of the conclusions is that the cationic drugs and neutral alcohols by perturbing preferentially the inner half-layer of the bilayer induced in pigeon erythrocyte membrane correlated multiphasic changes on fluidity and adenylate cyclase activity. This and other experimental data concerning the regulation of the adenylate cyclase are discussed in regard to a new interpretation of cyclase stimulation: the repressor hypothesis. In cell membrane the catalytic unit C is repressed by its association with a repressor complex made of the hormone receptor R and the regulatory protein N. The activation of cyclase activity is the dissociation of the catalytic unit C from the repressor complex R.N according to the equilibrium: R.N.C (inactive) in equilibrium R.N + C (active). Hormones, metal ions (magnesium), and nucleotides (GTP) are the allosteric ligands which shift this equilibrium towards the dissociation state with the liberation of the active form, membrane-bound, C unit. Gpp(NH)p, fluoride and forskolin will also shift the equilibrium toward the right. GDP and free receptors favour the associated repressed state of the system.

Adenylyl Cyclases↗
PubMed1992

[The effect of electroacupuncture "zusanli" and "neiguan" points on membrane fluidity of red cells in rabbits].

The effect of electroacupuncture "ZUSANLI" and "NEIGUAN" points on membrane fluidity of red cells in rabbits, has been determined by fluorescence polarization method. Results showed that the membrane fluidity of red cells was developed evidently after electro-acupunctured "NEIGUAN", but "ZUSANLI" had no effect on it, and it was significantly developed by electroacupuncture "ZUSANLI" and "NEIGUAN" points at the same time.

Acupuncture Points↗
PubMed1986

Membrane fluidity changes in P. berghei-infected erythrocytes, investigated with a specific plasma membrane fluorescent probe.

Trimethylamino-diphenylhexatriene (TMA-DPH), a novel hydrophobic fluorescent probe with relevant photophysical properties for fluorescence anisotropy measurements in phospholipidic membranes, specifically labels the plasma membranes of whole living-cells, unlike earlier commonly used probes such as 1,6-diphenyl-1,3,5-hexatriene (DPH) and anthroyloxy fatty acids, which invade all hydrophobic regions of the cell. Using TMA-DPH, it was shown that mouse malaria parasite Plasmodium berghei induced a statistically highly significant increase (8%) in the plasma membrane fluidity of the host erythrocyte. The physical factors, which might critically influence the measurements in this study, i.e. the fluorescence lifetime of the probe and the contribution of scattered light, were carefully controlled. The effect observed is discussed on the basis of earlier established metabolic changes in the membrane following infection, namely phospholipidic and cytoskeleton modifications.

Animals↗
PubMed1993

Organic solvents increase membrane fluidity and affect bile flow and K+ transport in rat liver.

Following the earlier observation that inhalation of volatile lipid solvents and of narcotic gases causes cholestasis, we studied the effects of various organic solvents on bile flow, plasma membrane fluidity and potassium movement in rat liver. Both in vivo and in the isolated perfused liver, applications of CCl4, CHCl3, dichloromethane, trichloroethylene, halothane, benzene and cyclohexane elicited rapid and sustained but reversible cholestasis. A transient phase of choleresis was observed prior to and after cholestasis, during the increase and fall in liver tissue solvent concentrations, respectively. Tissue concentrations required to produce cholestasis were lower the higher the lipophilicity of the solvent. Membrane fluidity was measured in isolated basolateral liver cell membranes by fluorescence polarization. Fluidity increased with increasing solvent concentration, the increase being associated with either biphasic stimulation and inhibition of membrane enzymes (Na+,K(+)-ATPase, 5'nucleotidase) or with inhibition alone (Mg(2+)-ATPase). In the isolated perfused liver, application of organic solvents caused hepatic uptake of K+ that was followed by K+ release upon withdrawal of the solvent. The magnitude of K+ uptake elicited by the solvent was comparable with the effect of blocking K+ channels with 2 mM Ba2+, but Ba2+ was ineffective in the presence of the solvent. In contrast, application of ouabain caused K+ release in equal amounts in the absence and presence of the solvent, indicating that K+ uptake elicited by the solvent results from inhibition of K+ efflux through K+ channels rather than stimulation of the Na+,K+ pump. The data show that cholestasis elicited by lipid solvents is associated with an increase in membrane fluidity and with disturbance of liver K+ homeostasis. The significance of these observations is discussed with respect to other models of experimental cholestasis.

Animals↗
PubMed2005

Combined cold, acid, ethanol shocks in Oenococcus oeni: effects on membrane fluidity and cell viability.

The effects of combined cold, acid and ethanol on the membrane physical state and on the survival of Oenococcus oeni were investigated. Membrane fluidity was monitored on intact whole O. oeni cells subjected to single and combined cold, acid and ethanol shocks by using fluorescence anisotropy with 1,6-diphenyl-1,3,5-hexatriene (DPH) as a probe. Results showed that cold shocks (14 and 8 degrees C) strongly rigidified plasma membrane but did not affect cell survival. In contrast, ethanol shocks (10-14% v/v) induced instantaneous membrane fluidisation followed by rigidification and resulted in low viability. Acid shocks (pH 4.0 and pH 3.0) exerted a rigidifying effect on membrane without affecting cell viability. Whatever the shock orders, combined cold (14 degrees C) and ethanol (14% v/v) shocks resulted in strong membrane rigidification. Interestingly, O. oeni survived combined cold and ethanol shocks more efficiently than single ethanol shock. Membrane rigidification was induced by ethanol-and-acid (10% v/v - pH 3.5) shock and correlated with total cell death. In contrast, O. oeni recovered its viability when subjected to cold (8 degrees C)-then-ethanol-and-acid shock which strongly rigidified the membrane. Our results suggested a positive short-term effect of combined cold, acid and ethanol shocks on membrane fluidity and viability of O. oeni.

Acids↗
PubMed2003

Biochemical assessments of oxidative stress, erythrocyte membrane fluidity and antioxidant status in professional soccer players and sedentary controls.

BACKGROUND: Physical exercise is characterized by an increase in oxygen consumption by the whole body. This leads to a decrease in antioxidant levels that could promote both an increase in the markers of lipoprotein peroxidation and damage to the erythrocyte membrane with consequent modification of membrane fluidity. MATERIALS AND METHODS: Different markers of oxidative stress, erythrocyte membrane fluidity and antioxidant status were determined in 20 professional soccer players and 20 sedentary controls. Plasma lipoperoxides and kinetics of Cu-stimulated plasma peroxidation were measured together with hydrosoluble (albumin, uric acid and vitamin C), liposoluble (vitamin E and bilirubin) and enzymatic (superoxide dismutase and glutathione peroxidase) serum antioxidants. Erythrocyte membrane rigidity was determined by measuring fluorescence anisotropy (rs) of the fluorescent probe 1, 3, 5 diphenylexatriene. RESULTS: The sportsmen showed higher levels of the following plasmatic antioxidants: ascorbic acid (P<0.0001), uric acid (P<0.0001), alpha-tocopherol (P=0.03) and superoxide dismutase activity (P=0.0001). According to this evidence, the lipoperoxide levels (P=0.0158), the duration of the latency phase of plasma peroxidation (P=0.0123) and erythrocytes membrane fluidity (P=0.0152) were found to be significantly higher in the soccer players. DISCUSSION: Athletes undergoing regular and adequate training show improved antioxidant status together with a more fluid membrane status, which could contribute to improving both peripheral resistance to insulin and all the functional metabolic interchanges in the cellular membrane.

Adult↗
PubMed1999

Changes in membrane fluidity and lipid peroxidation of skeletal muscle mitochondria after exhausting exercise in rats.

We studied the effects of exhausting exercise and exercise training on skeletal muscle mitochondrial membrane fluidity and lipid peroxidation in rats. The first part of the study involved 60 untrained rats divided into six equal groups. Of the total number 10 rats were sedentary and acted as controls. The remaining 50 rats exercised to exhaustion and were sacrificed at 0-h, 24-h, 48-h, 72-h, and 96-h post-exercise. The second part of the study involved 40 rats which were divided into four equal groups. Of these 10 rats were sedentary and acted as controls. The remaining 30 rats underwent 8 weeks of exercise training. They were then subjected to a single period of exhausting exercise and were sacrificed at 0-h, 24-h and 48-h post-exercise. Membrane fluidity was measured using the fluorescence polarization method. Lipid peroxidation was estimated by determining the thiobarbituric acid-reactive substances (TBARS) in mitochondria. In the untrained rats, mitochondrial fluorescence polarization and TBARS contents were significantly increased post-exercise compared with the sedentary controls (P < 0.05). They did not return to near control levels until 96 h and 48 h, respectively. In the trained rats, fluorescence polarization was raised compared with the sedentary controls but this was significantly lower than those measured at the same times of the untrained group post-exercise (P < 0.05). Exhausting exercise decreased membrane fluidity and increased lipid peroxidation in rat skeletal muscle mitochondria. These effects were relieved to some extent by exercise training.

Animals↗
PubMed2000

Membrane fluidity predicts the outcome of cryopreservation of human spermatozoa.

Semen cryopreservation is an important procedure in the treatment of human infertility. However, the ability of spermatozoa to survive freeze/thaw processes varies between patients. Cryopreservation-induced stress may result in membrane injury with consequent loss of sperm motility and viability. We investigated the relationship between the physico-chemical state of the human sperm membranes and their tolerance to cryopreservation. Conventional characteristics of 20 semen samples were analysed before and after cryopreservation as well as their membrane fluidity assessed by measuring the fluorescence polarization anisotropy, which is inversely proportional to the fluidity. Correlation between fluidity and post-thaw recoveries of motile and viable spermatozoa were examined. Results showed that membrane anisotropy markedly varies between patients. In cryopreserved spermatozoa, anisotropy values were significantly higher than in fresh spermatozoa. Furthermore, recovery of motile and viable spermatozoa after freeze/thaw was strongly correlated with anisotropy of fresh spermatozoa (P < 0.05). The higher the membrane fluidity was before freezing, the better was the response of spermatozoa to cryopreservation. The results indicate that the freeze/thaw process results in a rigidifying effect on the sperm membrane and suggest that sperm adaptability to freeze/thaw-induced stress could be dependent on their initial membrane fluidity. The latter finding has practical implications for predicting the response of spermatozoa following freezing and thawing and for improving the recovery of viable spermatozoa.

Cell Membrane↗
PubMed1994

The antioxidant action of synthetic oestrogens involves decreased membrane fluidity: relevance to their potential use as anticancer and cardioprotective agents compared to tamoxifen?

The synthetic oestrogens diethylstilboestrol, hexoestrol and 17 alpha-ethynyloestradiol are known to be good antioxidants, and we now report that they decrease membrane fluidity, in ox-brain phospholipid liposomes. The order of effectiveness was diethylstilboestrol > hexoestrol > 17 alpha-ethynyloestradiol and a good positive correlation was demonstrated between decreased membrane fluidity and antioxidant ability (measured as inhibition of liposomal lipid peroxidation: correlation coefficient, r = 0.99). This ability of diethylstilboestrol, hexoestrol and 17 alpha-ethynyloestradiol to decrease membrane fluidity is suggested, therefore, to be the mechanism of their antioxidant action. The membrane-modulating antioxidant action of these synthetic oestrogens is compared to that of tamoxifen and their potential use as anticancer and cardioprotective agents is discussed.

Antineoplastic Agents↗
PubMed1988

Effect of nitrogen dioxide on surface membrane fluidity and insulin receptor binding of pulmonary endothelial cells.

Nitrogen dioxide (NO2), an environmental oxidant pollutant, is known to peroxidize membrane lipids of lung cells. We evaluated the ability of NO2 to alter the surface membrane fluidity, lipid composition, and insulin receptor binding of porcine pulmonary artery endothelial cells in culture. After 3- to 24-hr exposure to 5 ppm NO2, cells were labeled with either 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH), a cationic fluorescent aromatic hydrocarbon that anchors at the lipid-water interface, or fluorescamine, a fluorescent molecular probe that covalently binds with amino groups of surface phospholipids and proteins. Membrane fluidity was measured by monitoring changes in the steady-state fluorescence anisotropies (rs) for TMA-DPH and fluorescamine. Insulin specific receptor binding was monitored by measuring time-dependent binding of 125I-insulin. Following NO2 exposure, rs values for TMA-DPH and fluorescamine were increased significantly in a time-dependent fashion, with maximum increases at 24 hr (P less than 0.001). Similar increases in rs values were observed in isolated plasma membranes as well as in lipid vesicles prepared from total lipid extracts of endothelial cells or their plasma membranes. Phosphatidylethanolamine plus phosphatidylserine content in lipid extracts from 24-hr but not 3- to 12-hr NO2-exposed cells was increased significantly (P less than 0.01) compared to control cells. Specific binding of 125I-insulin to cells exposed to NO2 for 12 and 24 hr (but not 3 and 6 hr) was reduced significantly (P less than 0.05) compared to binding in control cells. Scatchard analysis of the binding data indicated that NO2 exposure caused a 5-fold reduction in insulin receptor binding sites in endothelial cells. Recovery was achieved 24 hr after NO2 exposure with, but not without, changing culture medium. These results indicate that NO2 exposure causes reversible changes in the physical state of lipids in the superficial lipid domains of the pulmonary endothelial cell plasma membrane, and these alterations may interfere with plasma membrane-dependent functions such as receptor-ligand interaction.

Amino Acids↗
PubMed1997

[Effect of superoxide dismutase on membrane fluidity and functions of lymphocytes in traumatized mice].

Effect of superoxide dismutase (SOD) on membrane fluidity and functions of lymphocytes in traumatized mice was studied. The results showed that in vivo administration of SOD (10,000 U/kg.d, from 0 to 3 days posttrauma) could significantly decrease malondialdehyde (MDA) contents in serum, lymphatic tissues from spleen, thymus, mesenteric lymph nodes and T cells plasmalemma, mitochondria, microsome, restore decreased T lymphocytes and T cells in traumatized mice, elevate membrane fluidity of lymphocytes transformation (TLT), reduce interleukin 2 (IL-2) production, supprssed IL-2 receptor (IL-2R) expression and depress IL-2 mediated lymphocyte proliferation response (IL 2MLPR) after trauma in various degress. It is suggested that SOD may protect lymphocytes post trauma from damage of oxygen free radical, and elevate lymphocytes functions.

Animals↗
PubMed1985

Plasma membrane fluidity studies by fluorescence polarization in rat mast cells stimulated by compound 48/80.

Plasma membrane fluidity measurements were performed on purified living mast cells using a novel non-permeant fluorescence polarization probe TMA-DPH, upon stimulation by compound 48/80. The fluorescence anisotropy increased rapidly after treatment by 48/80 in a dose-dependent way. The effect was found to be specific for mast cells; it was inhibited by the histamine release antagonist FR 7534 in a correlative manner. The role of calcium was examined. The results brought evidence for a plasma membrane fluidity decrease induced by 48/80; a biphasic mechanism was inferred for the histamine release process.

Animals↗
PubMed1995

Anemia in copper-deficient rats: role of alterations in erythrocyte membrane fluidity and oxidative damage.

This study was designed to make precise the nature and the mechanism of the anemia induced by dietary copper (Cu) deficiency. Male Wistar rats were pair fed from weanling for 6 wk either a Cu-deficient or a control diet. The reduced red blood cell (RBC) 51Cr survival indicates an increased destruction of RBC during Cu deficiency. 1,6-Diphenyl-1,3,5-hexatriene fluorescence polarization studies revealed an increase in the fluidity of erythrocyte membranes from deficient rats. The reduced cholesterol-to-phospholipid ratio was consistent with the increased fluidity. Other results indicate an increased vulnerability of RBC to hemolysis in dilute hydrogen peroxide and an increased formation of lipid peroxidation products. Before exposure to free radical stress, electron spin resonance studies in intact RBC revealed decreased correlation time of 16-doxyl-stearic acid, confirming a more fluid membrane in RBC from Cu-deficient rats. After in vitro peroxidation, RBC from Cu-deficient rats showed a more ordered state of membrane lipids compared with controls. Together, these studies demonstrate the hemolytic nature of the anemia. The shortened survival of erythrocytes apparently results from changes in membrane fluidity and enhanced susceptibility to peroxidation.

Anemia↗
PubMed1992

Membrane fluidity and platelet aggregation: dibucaine permits ristocetin-induced platelet aggregation with low-molecular-weight von Willebrand multimers.

The effects of brief incubation of platelets with dibucaine were studied. Membrane fluidity was increased after incubation with 1 mM dibucaine for 1 min as determined by fluorescence polarization. Platelet aggregation was increased when ristocetin was employed as modulator and normal plasma used as a source of von Willebrand factor (vWF). In contrast, aggregation was decreased with botrocetin. After cryoprecipitation the supernatant, which contained predominantly low-molecular-weight vWF multimers, was effective with ristocetin only after prior incubation of the platelets with dibucaine. This indicates that low-molecular-weight vWF multimers can also support ristocetin-induced aggregation when the membrane fluidity is increased. This idea was supported by the use of plasma from a patient with von Willebrand disease type IIa. Being a multimeric protein, von Willebrand factor contains multiple binding sites for glycoprotein Ib (GP Ib). GP Ib-dependent aggregation by agents that do not contain multiple binding sites, i.e. wheat germ agglutinin or polyclonal antibodies to GP Ib, was decreased after brief incubation with dibucaine. These observations are discussed in relation to the hypothesis that the increased membrane fluidity allows an increased number of GP Ib molecules to bind to each vWF multimer.

Crotalid Venoms↗
PubMed1986

Effect of essential fatty acid deficiency on acyl group composition, membrane fluidity and adenylate cyclase activity in plasma membranes of rat submandibular salivary glands.

The effects of a marginal and severe deficiency of essential fatty acids (EFA) on the fatty acid composition, fluorescence polarization of diphenylhexatriene (DPH) and adenylate cyclase activity were studied in plasma membranes of rat submandibular salivary glands (SMSG). Three groups of male weanling Sprague-Dawley rats were fed ad libitum EFA-deficient (EFAD), marginally EFA-deficient (MEFAD) or the control diets. Rats were killed after 8-17 wk of feeding and plasma membranes were prepared from the SMSG and the assayed for basal and fluoride-stimulated adenylate cyclase activity. In membranes prepared from EFAD and MEFAD rats, the fluoride-stimulated enzyme activity was 30-35% higher than that of the control group. Lower double-bond index of phospholipids in plasma membranes of the SMSG from EFAD and MEFAD rats was observed, suggesting a lower fluidity compared with the control group. Higher fluorescence polarization of DPH in membranes of EFAD and MEFAD rats was more evidence of lower fluidity. It is suggested that higher adenylate cyclase activity in SMSG of rats fed EFAD or MEFAD diets may be related to lower membrane fluidity. Fluoride-stimulated enzyme activity and fatty acid composition of membrane lipids were restored to normal values after feeding the control diets for 6 wk to the EFAD and MEFAD rats.

Adenylyl Cyclases↗
PubMed1994

Effects of kappa-selenocarrageenan on membrane fluidity and ghost reseal ability of rat erythrocyte.

Effects of kappa-selenocarrageenan (kappa-SeC) on membrane fluidity and ghost reseal ability of rat erythrocyte were studied by measuring the fluorescence polarization and the NADH-cytochrome C oxido-reductase, respectively. After rats were given ig kappa-SeC 140 mg.kg-1.d-1 x 30 d, the fluorescence polarization was decreased in comparison with saline control group (P < 0.05). It suggested that kappa-SeC increased the membrane fluidity. The reseal ability of erythrocyte membrane (ghost) was also elevated after ig kappa-SeC 140 and 70 mg.kg-1.d-1 x 30 d (P < 0.05).

Animals↗