Membrane conducting

Within the nervous system, ChEs were shown to be involved in membrane conductance and transmission of excitatory amino acids, learning and memory, neurite growth, neuritic translocation and acute stress reactions. Recent findings propose AChE s involvement in apoptosome formation [2]. 

A = approximate area of the bilayer lipid membrane G = membrane conductance Gj = specific membrane conductance Cm = membrane capacitance C, = specific membrane capacitance. 

Ionotropic Those linked directly to ion channels such as those for Na+ (e.g. ACh nicotinic or some glutamate receptors) or Cl (GABA), involving fast events with increased membrane conductance and ion flux. 

In both Navanax neurons (65) and an artificial phospholipid bilayer membrane (66). salicylic acid (1-30 mM) increased K" " permeability but decreased Cl- permeability resulting in a net Increase in membrane conductance. To account for the selective effect of salicylic acid (and other benzoic acids) on the two permeabilities, it was proposed that the anions of the organic acids adsorb to membranes to produce either a negative surface potential (66) or an increase in the anionic field strength of the membrane (47, 48). 

Fig. 21.3. Two-micropipette current-clamp recording and effect of maintained application of 30 pM levamisole, which produces a 15 mV depolarization (upward movement of trace). The downward transients are the result of injected current pulses used to measure membrane conductance. The trace gets narrower as the input conductance increases from 2.35 pS to 4.35 pS as the levamisole ion channels open. The peak amplitude of the membrane potential response and change in input conductance are used as an assay of the number and activity of the levamisole ion channel receptors present in the muscle cell membrane. The response was fully reversible on washing (not shown).

Kasianowicz et al. [65] described the determination of the transport of niclosamide protons across lipid bilayer membranes by equilibrium dialysis, electrophoretic mobility, membrane potential, membrane conductance, and spectrophotometric... 

Seizures result from excessive excitation, or from disordered inhibition of a population of neurons. Initially, a small number of neurons fire abnormally. Then normal membrane conductances and inhibitory synaptic currents break down, excitability spreads locally (focal seizure) or more widely (generalized seizure). 

Bloc, A. et al., An invertebrate defense molecule activates membrane conductance in mammalian cells by means of its lectin-like domain, Dev. Comp. Immunol., 26, 35, 2002. 

Gas separation membranes, conducting polymer applications, 7 539 Gas-solid chromatography, adsorption,... 

In this section, we describe the role of fhe specific membrane environment on proton transport. As we have already seen in previous sections, it is insufficient to consider the membrane as an inert container for water pathways. The membrane conductivity depends on the distribution of water and the coupled dynamics of wafer molecules and protons af multiple scales. In order to rationalize structural effects on proton conductivity, one needs to take into account explicit polymer-water interactions at molecular scale and phenomena at polymer-water interfaces and in wafer-filled pores at mesoscopic scale, as well as the statistical geometry and percolation effects of the phase-segregated random domains of polymer and wafer at the macroscopic scale. 

The effective conductivity of the membrane depends on its random heterogeneous morphology—namely, the size distribution and connectivity of fhe proton-bearing aqueous pafhways. On fhe basis of the cluster network model, a random network model of microporous PEMs was developed in Eikerling ef al. If included effecfs of varying connectivity of the pore network and of swelling of pores upon water uptake. The model was applied to exploring the dependence of membrane conductivity on water content and... 

A. Destexhe and T. J. Sejnowski, Interactions between membrane conductances underlying thalamocortical slow wave oscillations. Physiol. Rev 83, 1401-1453 (2(X)3). 

Distributions of water and reactants are of high interest for PEFCs as the membrane conductivity is strongly dependent on water content. The information of water distribution is instrumental for designing innovative water management schemes in a PEFC. A few authors have studied overall water balance by collection of the fuel cell effluent and condensation of the gas-phase water vapor. However, determination of the in situ distribution of water vapor is desirable at various locations within the anode and cathode gas channel flow paths. Mench et al. pioneered the use of a gas chromatograph for water distribution measurements. The technique can be used to directly map water distribution in the anode and cathode of an operating fuel cell with a time resolution of approximately 2 min and a spatial resolution limited only by the proximity of sample extraction ports located in gas channels. 

Some doubt might be expressed about the concentration dependence of the membrane conductance and the evaluation of the limiting ratio K /c in equation 24. We have found the ratio (K -K )/Cg to be aimost constant. If it is plotted against 1/c (see Figure 4) and extrapolated to 1/c =0 one obtains the... 

Table III. Membrane Conductance and Physicochemical Constants of Benzoic Acids Used...

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