Membrane fluidization

Rl. MRP, MRP2. MRP3. LRP. BCRP. pH Vesicularrlransport Membrane Fluidization... 

Regev R, Assaraf YG, Eytan GD (1999) Membrane fluidization by ehter, other anesthetics, and certain agents abolishes P-glycoprotein ATPase activity and modulates efflux from multidrug-resistant cells. Eur J Biochem 259 18-24... 

Membrane conformational changes are observed on exposure to anesthetics, further supporting the importance of physical interactions that lead to perturbation of membrane macromolecules. For example, exposure of membranes to clinically relevant concentrations of anesthetics causes membranes to expand beyond a critical volume (critical volume hypothesis) associated with normal cellular function. Additionally, membrane structure becomes disorganized, so that the insertion of anesthetic molecules into the lipid membrane causes an increase in the mobility of the fatty acid chains in the phospholipid bilayer (membrane fluidization theory) or prevent the interconversion of membrane lipids from a gel to a liquid form, a process that is assumed necessary for normal neuronal function (lateral phase separation hypothesis). 

FIGURE 28.4 Schematic illustration twofold effects of Pluronic block copolymer on Pgp drug efflux system. Inhibition of Pgp activity is due to a combination of two cellular pathways depletion of ATP levels and membrane fluidization in the cells. 

Batrakova, E., et al. 2001. Mechanism of pluronic effect on P-glycoprotein efflux system in blood-brain barrier Contributions of energy depletion and membrane fluidization. J Pharmacol Exp Ther 299 483. 

Butyl ether has the ability to dissolve lipids. As a result, it may cause irritation and pain upon contact with eyes and nose mucosa. It also causes dermal irritation and dermatitis upon contact with the skin. Damage caused by butyl ether appears to be scattered loss of epithelial cells due to dissolution of phospholipid cell membranes. At the CNS level, butyl ether, like other volatile organic solvents, depresses the CNS by dissolving in the cell lipid membrane and disrupting the lipid matrix. These effects are known as membrane fluidization. At the molecular level, membrane fluidization disrupts solute gradient homeostasis that is essential for cell function. 

Tsuchiya H. Structure-specific membrane-fluidizing effect of propofol. Clin Exp Pharmacol Physiol 2001 28 292-9. 

The enhancement or inhibitory effect of the comutagens on mutagenicity may be a net result of substrate inhibition and membrane fluidization in the microsomal or nuclear mixed-function-oxidase system. 

The Enhancement or the Inhibitory Effect of the S-CarboHnes Is a Net Result of Substrate Inhibition and Membrane Fluidization ... 

The alternative explanation must involve the MFO system. The possible mechanism for the inhibitory effect or enhancement effect of Norharman upon covalent DNA binding and mutagenicity must be the results of the net balancing of substrate inhibition and membrane fluidization of the microsomal membrane or of the lipid vesicles in the reconstituted MFO system. A schematic pathway of the metabolism of these tryptophan pyrolysis products is postulated as shown in Figure 8. 

Enhancement due to membrane fluidization (-) Inhibition due to substrate inhibition (+) No net effect due to reversibility... 

The added-particle effect is also evident in the application of fluidized beds to provide turbulence promotion. Figure 10.46 is a schematic diagram of a combined tubular membrane-fluidized bed system. It consists of a tubular membrane module, fluidized particles, a feed pump, and the feed storage tank. During the operation, the particles are fluidized... 

Various mechanisms which are responsible for the efflux-pump inhibitory properties of pluronics have been identified and discussed in detail previously [30]. Among them are inhibition mediated by ATP depletion, membrane fluidization and ATPase inhibition. As... 

However, besides the high heat exchange coefficients, fluidized beds are also suitable for isothermal operations even if a highly exothermic reaction is occurring. This has been demonstrated a.o. by Deshmukh et al. [46,47], who carried out oxidative dehydrogenation of methanol in laboratory-scale membrane fluidized bed reactors. The authors found virtually isothermal conditions even for very high methanol feed concentrations. This important... 

Increase in temperature (from O to 40 C Fig.l) corresponded to increase in membrane fluidity and decrease in Fm. Similarly in presence of n-butanol/ a membrane fluidizing agent (Fig.3) Fm was found to decrease. This may suggest that high yield of fluorescence which is related to PS II activity is observed only when the membrane fluidity is optimum/ e.g. at low temperature. Addition... 

Indeed, Roy et aL first demonstrated that autothermal operation could be achieved by directly adding oxygen to a fluidized bed reformer to provide all of the heat required via the partial oxidation reaction [24], The extension of this work to a membrane fluidized bed reactor has been performed by the same... 

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