Membrane potentials measurement

Szollosi, J., Damjanovich, S., Mulhem, S. A., and Tron, L. (1987) Fluorescence energy transfer and membrane potential measurements monitor dynamic properties of cell membranes a critical review. Prog. Biophys. Mol. Biol. 49, 65-87. 

In conclusion, it can be claimed that a combination of kinetic and equilibrium conductance and membrane potential measurements provides a powerful method for investigating the permselective properties of membranes of low fixed charge density. Such methods should be applicable also to other polymers useful in hyperfiltration if they can be prepared in the form of homogeneous membranes. 

PANCREAS Membrane potential measurements in pancreatic /3 cells with intracellular microelectrodes, 192, 235 stimulation of secretion by secretagogues, 192, 247 pancreatic secretion in vivo, perfused gland, and isolated duct studies, 192, 256 dispersed pancreatic acinar cells and pancreatic acini, 192, 271 permeabilizing cells some methods and applications for the study... 

Transport numbers can be measured by different methods. The small mono- and divalent inorganic ions have been used to demonstrate skin permselectivity, and have been determined from membrane potential measurements, or by the Hittorf method [10,25,77,79]. The latter method has been frequently used for drugs alternatively, the transport number can be estimated from the slope of a plot of drug flux as a function of current intensity (Figure 14.4) [18,66]. 

The voltage v in the Hodgkin-Huxley model is the membrane potential measured relative to the equilibrium voltage Veq v = AT — Veq, where Veq is the potential when no current is applied. The experimentally determined equilibrium potentials (which depend on the ion gradients across the membrane) for the model are... 

Other electrochromic membrane probes of note include, me-rocyanine 540 used to study the transmembrane potential in liver mitochondria although some problems are evident (5, 30, 31). Overall, measurements of transmembrane potential differences in living cells are well established with the methods fairly reliable and robust. Many of these membrane potential measurement strategies are generic and hold for plasma membranes of neurones and other excitable tissues (6). 

O Shea P. Membrane potentials measurement, occurrence and roles in cellular function. In Bioelectrochemistry of Membranes. Walz D, et al., eds. 2005. Birkhauser Verlag, Switzerland, pp. 23-59. 

Intermingled with the neurons in the brain are a variety of other cell types. The most common of these satellite cells are glial cells. These make up virtually about one half of the total volume of the brain and exist in several forms such as astrocytes, oligodendrocytes, and Schwann cells. Membrane properties of glial cells exhibit fundamental differences from neurons, the chief difference being their passive nature. Unlike neurons, most glial cells are not excitable and do not fire action potentials. Membrane potential measurements of... 

The ions which are most frequently employed to estimate mitochondrial membrane potential are Rb in the presence of valinomycin, and lipophilic phosphonium cations. The ionophore valinomycin creates a uniport pathway for K or Rb in a variety of membranes [25]. The use of Rb enables the concentration gradient to be determined iso topically after rapid separation of the mitochondria from the medium Rb is usually considered to behave ideally in the matrix (i.e., not to be bound). Indeed, other methods of membrane potential measurement are usually referred back to the K or Rb gradient in the presence of valinomycin for their calibration. However, a disadvantage is that the ionophore will also transport K, which means that when the ionophore is added the membrane potential will tend to shift towards the value given by any K-gradient which happens to be pre-existing across the membrane. 

Involvement of Plasmalemma Energization. For SSHB and DHS the membrane potential measurements in Egeria leaf... 

Table 6.6 lists voltage-gated sodium channelopathies (disease, mutations and phenotype), Table 6.7 describes the VGSC gene family and Table 6.8 describes ion-chatmel assay technologies, such as electrophysiology, membrane-potential measurement, flux assays, and binding assays. 

Cells treated 7.5 or 960 min with cytotoxic levels of paraoxon, tri-o-tolyipbosphatc, or triphenyl phosphite mitochondrial membrane potential measured by image analy.sis with rhodaminc 123. 

O Shea P (2004). Membrane Potentials measurement, occurrence roles in cellular function pp 23-59 in Bioelectmchemistry of Membranes (D. Walz et al. Eds) Birkhauser Verlag, Switzerland. 

The intact ATPase system of frog-muscle plasma membrane is elec-trogenic, and the passage of one positive charge outwards per hydrolytic cycle may agree with the membrane potential measurements ... 

Benavente, J Canas, A Ariza, MJ Lozano, AE de Abajo, J. Electrochemical parameters of suUbnated poly(ether ether sulfone) membranes in HCl solutions determined by impedance spectroscopy and membrane potential measurements. Solid State Ionics, 2001, 145, 53-60. 

Here the bacteria were added to an acidic medium at pH 3.5 and their membrane potential measured by the dye-uptake method outlined earlier. No membrane potential was found at that pH. After 5 minutes, buffer was added to elevate medium pH to 6.2, and no restoration of the potential was found, indicating death of the organism. On the other hand, when buffer was added almost immediately to bring the pH back to 6.2, there was a slow recovery of membrane potential to the control value expected for a medium pH of 6.2. Hence, H. pylori is able to survive only short exposure to acid, and its acid-adaptive response must happen relatively quickly. Again, this shows that acid-adaptive mechanisms are essential even for survival of the organism with exposure to mild acidity. 

Ion transport numbers across membranes (relative ion fluxes) and effective fixed charge can be obtained from membrane potential measurements, but a wide porous structure might mask the membrane material electrical characteristics (membrane/solution interactions). These can be determined from filtration... 

Seamer, L. C. Mandler, R. N. Method to improve the sensitivity of flow cytometric membrane potential measurements in mouse spinal cord cells. Cytometry 1992, 13, 545-552. 

Feeney, C. J. Pennefather, P. S. G5mlkhandanyan, A. V. A cuvette-based fluorometric analysis of mitochondrial membrane potential measured in cultured astrocyte monolayers. J. Neurosci. Methods 2003, 125, 13-25. 

Sureda, E X. Escubedo, E. Gabriel, C. Comas, J. Camarasa, J. Camins, A. Mitochondrial membrane potential measurement in rat cerebellar neurons by flow cytometry. Cytometry 1997,28,74-80. 

In membrane potential measurements, a membrane is positioned between two half-cells. The cells are filled with electrolyte solutions the solution of higher electrolyte concentration is in contact with the active side of the membrane, and the solution of lower electrolyte concentration is in contact with the membrane support layer. The electrical potential difference is measured by inserting electrodes directly into the bulk solutions (Fig. 32.7a). The membrane potential measurements evaluate the amount of charge inside the membrane (Canas and Benavente, 2002 Nakagaki and Takagi, 1986 Schaep and Vandecasteele, 2001 Takagi et al., 2000). 

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