Phototoxic effect of fluoroquinolones on two human cell lines
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Ethidium bromide
Phototoxicity
Cell membrane
HL60
Mechanism of Action
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Phorbol
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AIM: To study the effects of propofol on plasma membrane fluidity in PC12 cells and liposome,and its relevant mechanism. METHODS: Fluorescence depolarization method was used to measure values of fluorescence anisotropy, fluorescence polarization as well as microviscosity in PC12 cells and microviscosity in liposome continuously for 30 min. RESULTS: Propofol induced a significant decrease of fluorescence anisotropy, fluorescence polarization as well as microviscosity in PC12 cells, particularly in the first 5 min. After 5 min, the values of anisotropy were remained lower levels. Although propofol at concentration of 1 mg·L -1 had no effects on microviscosity in liposome, porpofol at concentration of 10 mg·L -1 and 100 mg·L -1 significantly decreased microviscosity in liposome. CONCLUTION: Propofol can significantly increase membrane fluidity in PC12 cells and liposome in a concertration dependent manner, and the anesthetic effect of propofol may be resulted from changes of membrane fluidity and structure of neurocyte.
Microviscosity
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The objectives of this study were to determine whether there are differences between black and white individuals with regard to the membrane fluidity of isolated erythrocytes, and/or in the relationships between membrane fluidity, gender and circulating lipids. Fluorescent polarization anisotropy, as an index of membrane fluidity, was determined using the fluorescent probe 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) in 52 black and 52 white individuals, of whom 39 pairs were matched for age, sex and blood pressure. In the 39 matched pairs, the TMA-DPH anisotropy was significantly higher in the black (0.262+/-0.007) compared with the white (0.258+/-0.005) subjects (P<0.005). There was also a significant difference in serum lipids. Gender differences in TMA-DPH anisotropy were observed in the white but not in the black individuals. The associations between membrane fluidity and serum lipids were examined in the total group, separated according to ethnic group. Although the associations were in the same direction in both groups, the association was only significant in the white subjects (r= - 0.42; P<0.02). The ethnic difference in membrane fluidity was abolished when adjusting for serum triacylglycerols. In conclusion, ethnic differences in erythrocyte membrane fluidity, as determined by the use of TMA-DPH anisotropy, appear to be the result of ethnic differences in the level of serum triacylglycerols.
Association (psychology)
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The lipophilic fluorescent probe diphenylhexatriene (DPH) has been shown previously to behave as a marker of plasma membrane in living cell systems, and it is therefore been widely used in membrane fluidity studies via fluorescence anisotropy measurements. The anisotropic coefficient, which is inversely related to the rotational motion of the probe in membrane phospholipids, was significantly higher at 37 degrees C than at 23 degrees C for 9 series of red blood cells ghosts obtained from three healthy subjects. We also have studied the importance of the nature of two different polaroid films which permits the observation of fluorescence polarization.
Diphenylhexatriene
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The effect of hydrostatic pressure at levels applied in diving or hyperbaric treatment (thus considered “physiological”) on the order of lipid domains in human red blood cell (RBC) membrane was studied. Membrane order was determined by measuring 1) the fluorescence anisotropy (FAn) of lipid probes, 2) the resonance energy transfer from tryptophan to lipid probes, and 3) spectral shifts in Laurdan fluorescence emission. It was found that the application of mild pressure (< 15 atm) 1) increased, selectively, the FAn of lipid probes that monitor the membrane lipid core, 2) increased the tryptophan FAn, 3) increased the resonance energy transfer from tryptophan to lipid probes residing in the lipid core, and 4) induced changes in the Laurdan fluorescence spectrum, which corresponded to reduced membrane hydration. It is proposed that the application of pressure of several atmospheres increases the phase order of membrane lipid domains, particularly in the proximity of proteins. Because the membrane lipid order (“fluidity”) of RBCs plays an important role in their cellular and rheological functions, the pressure-induced alterations of the RBC membrane might be pertinent to microcirculatory disorders observed in humans subjected to elevated pressure.
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Hydrostatic pressure
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Agglutination (biology)
Ristocetin
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Lipid rafts are specialized microdomains in cell membranes, rich in cholesterol and sphingolipids, and play an integrative role in several physiological and pathophysiological processes. The integrity of rafts can be disrupted via their cholesterol content-with methyl-β-cyclodextrin (MCD) or with our own carboxamido-steroid compound (C1)-or via their sphingolipid content-with sphingomyelinase (SMase) or with myriocin (Myr). We previously proved by the fluorescent spectroscopy method with LAURDAN that treatment with lipid raft disruptors led to a change in cell membrane polarity. In this study, we focused on the alteration of parameters describing membrane fluidity, such as generalized polarization (GP), characteristic time of the GP values change-Center of Gravity (τCoG)-and rotational mobility (τrot) of LAURDAN molecules. Myr caused a blue shift of the LAURDAN spectrum (higher GP value), while other agents lowered GP values (red shift). MCD decreased the CoG values, while other compounds increased it, so MCD lowered membrane stiffness. In the case of τrot, only Myr lowered the rotation of LAURDAN, while the other compounds increased the speed of τrot, which indicated a more disordered membrane structure. Overall, MCD appeared to increase the fluidity of the membranes, while treatment with the other compounds resulted in decreased fluidity and increased stiffness of the membranes.
Laurdan
Lipid raft
Sphingolipid
Raft
Membrane Lipids
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Laurdan
Dipalmitoylphosphatidylcholine
Diphenylhexatriene
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