Ionic permeability, effect

PE permeability was enhanced by CaCl2 at lower concentrations than effective for NaCl. Pi8o in O.IM CaCL was approximately 0.33, and similar to the permeability in 0.4M NaCl at pH 3.8. There seems to be a unique cation effect rather than ionic strength effect. At equivalent ionic strength (0.3M NaCl and O.IM CaCl2, pH 3.8), Pjso of PE with CaCl2, was approximately four fold higher. 

Schafer JA, Troutman SL, Andreoli TE (1974) Volume reabsorption, transepithelial potential differences, and ionic permeability properties in mammalian superficial proximal straight tubules. J Gen Physiol 64 582-607 Schlatter E, Greger R, Weidtke C (1983) Effect of high ceiling diuretics on active salt transport in the cortical thick ascending limb of Henle s loop of rabbit kidney. Correlation of chemical structure and inhibitory potency. Pfltigers Arch 396 210-217... 

Walters, K.A. Walker, M. Olejnik, O. Non-ionic surfactant effects on hairless mouse skin permeability characteristics. J. Pharm. Pharmacol. 1988, 40, 525-529. 

Fixed Charge Hypothesis. According to the computation described above, the movement of an ion across the red cell membrane is governed by its concentration gradient and the transmembrane potential. It has been suggested (33) that the membrane potential is one factor that, in addition to its direct effect on flux, is a determinant of ionic permeability. For cation movements over wide ranges of membrane potential, a relatively small dependence of permeability on potential has been demonstrated (34). 

Addition of sterol to bilayer membranes dramatically decreased both ionic and non-ionic permeability [212] but interaction of polyenes with membrane sterol did more than simply reverse the effect of sterol incorporation. Polyene addition produced specific permeability alterations [201—205] consistent with the creation of ion-selective channels or pores within the bilayer. 

While the modeling efforts of Barnes and Hu, Cain, Pickard, and Rosenbaum are not likely to reveal the precise nature of athermal coupling between field and membrane, they are useful in that correlations can conceivably be made, in the case of excitable membranes, between possible changes in membrane permeability to various ionic species, effects on gating currents, displacement of the resting potential, etc., to the frequency and intensity of the applied radiation, as well as to the duration of exposure. 

Action events involve a multiphase biochemical-bioelectric process. A localized stimulus to an excitable cell can launch a series of cascading molecular events affecting the membrane s ionic permeability. The accompanying changes in TMP feed back on the membrane by way of voltagegated channels and magnify the effect of the stimulus. If the stimulus amplitude reaches a threshold value, this causes further and more dramatic changes in the membrane s ionic permeability. 

These simulations were performed only for one type of the membrane. Therefore, there is no direct data on the effect of different head groups and membrane widths on ionic permeability. It can be expected, however, that for sufficiently wide membranes, the formation of deep deformations, extending to the midplane of the bilayer, would become highly unfavorable. Then, the ion would have to undergo almost complete desolvation near the center of the bilayer. In... 

Ionic liquids have already been demonstrated to be effective membrane materials for gas separation when supported within a porous polymer support. However, supported ionic liquid membranes offer another versatile approach by which to perform two-phase catalysis. This technology combines some of the advantages of the ionic liquid as a catalyst solvent with the ruggedness of the ionic liquid-polymer gels. Transition metal complexes based on palladium or rhodium have been incorporated into gas-permeable polymer gels composed of [BMIM][PFg] and poly(vinyli-dene fluoride)-hexafluoropropylene copolymer and have been used to investigate the hydrogenation of propene [21]. 

Seventy years later, this theory largely holds true, although periodically challenged [67, 68]. Observation of transmembrane permeability of ionic species was initially explained by the formation of neutral ion-pair [69, 70]. A comprehensive review of the physicochemical properties influencing permeation has been written by Malkia et al. [5]. The reality is that, despite many studies, the effect of ionization on permeation is still a matter of discussion and active research. In contrast, it became clear that bulk-phase partitioning measurements are not adequate to describe bilayer partitioning [71-73]. 

Precellular solute ionization dictates membrane permeability dependence on mucosal pH. Therefore, lumenal or cellular events that affect mucosal microclimate pH may alter the membrane transport of ionizable solutes. The mucosal microclimate pH is defined by a region in the neighborhood of the mucosal membrane in which pH is lower than in the lumenal fluid. This is the result of proton secretion by the enterocytes, for which outward diffusion is slowed by intestinal mucus. (In fact, mucosal secretion of any ion coupled with mucus-restricted diffusion will provide an ionic microclimate.) Important differences in solute transport between experimental systems may be due to differences in intestinal ions and mucus secretion. It might be anticipated that microclimate pH effects would be less pronounced in epithelial cell culture (devoid of goblet cells) transport studies than in whole intestinal tissue. 

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