Cell membrane, electrical properties

Harder, D.R., Brann, L., and Halpern, W. (1983) Altered membrane electrical properties of smooth muscle cells from small cerebral arteries of hypertensive rats. Bloodvessels, 20 154-160. 

More recently, dielectrophoretic studies have for instance been reported on T-lymphocytes (Pethig and Talary, 2007) and on how cell destruction during dielectrophoresis can be minimized (or used) by appropriate choice of AC frequency and amplimde (Menachery and Pethig, 2005). Dielectrophoresis has also been used for measurement of membrane electrical properties such as capacitance and conductance for insulin-secreting pancreatic cells (Pethig et al., 2005). 

Researchers at the MoneU Center (Philadelphia, Pennsylvania) are using a variety of electrophysical and biochemical techniques to characterize the ionic currents produced in taste and olfactory receptor cells by chemical stimuli. These studies are concerned with the identification and pharmacology of the active ion channels and mode of production. One of the techniques employed by the MoneU researchers is that of "patch clamp." This method aUows for the study of the electrical properties of smaU patches of the ceU membrane. The program at MoneU has determined that odors stimulate intraceUular enzymes to produce cycUc adenosine 3, 5 -monophosphate (cAMP). This production of cAMP promotes opening of the ion channel, aUowing cations to enter and excite the ceU. MoneU s future studies wiU focus on the connection of cAMP, and the production of the electrical response to the brain. The patch clamp technique also may be a method to study the specificity of receptor ceUs to different odors, as weU as the adaptation to prolonged stimulation (3). 

By the time the next overview of electrical properties of polymers was published (Blythe 1979), besides a detailed treatment of dielectric properties it included a chapter on conduction, both ionic and electronic. To take ionic conduction first, ion-exchange membranes as separation tools for electrolytes go back a long way historically, to the beginning of the twentieth century a polymeric membrane semipermeable to ions was first used in 1950 for the desalination of water (Jusa and McRae 1950). This kind of membrane is surveyed in detail by Strathmann (1994). Much more recently, highly developed polymeric membranes began to be used as electrolytes for experimental rechargeable batteries and, with particular success, for fuel cells. This important use is further discussed in Chapter 11. 

Pulsed electric field is another alternative to conventional methods of extraction. PEF enhances mass transfer rates using an external electrical field, which results in an electric potential across the membranes of matrix cells that minimizes thermal degradation and changes textural properties. PEF has been considered as a nonthermal pretreatment stage used to increase the extraction efficiency, increasing also permeability throughout the cell membranes. 

At the same time (1902), a membrane theory was proposed for the electrical properties of cells and tissues by Overton [80] and Bernstein [8], whose principles remain valid to the present day. 

In another type, mammalian cells or plasma membranes are used as electrical capacitors. Electrical impedance (El) uses the inherent electrical properties of cells to measure the parameters related to the tissue environment (Kyle et al., 1999). The mechanical contact between cell-cell and cell-substrates is measured via conductivity or El (Deng et al., 2003 ... 

The effects of digitalis on the electrical properties of the heart are a mixture of direct and autonomic actions. Direct actions on the membranes of cardiac cells follow a well-defined progression an early, brief prolongation of the action potential, followed by shortening (especially the plateau phase). The decrease in action potential duration is probably the result of increased potassium conductance that is caused by increased intracellular calcium (see Chapter 14). All these effects can be observed at therapeutic concentrations in the absence of overt toxicity (Table 13-2). 

Reverdin EC, Weingart R Electrical properties of the gap junctional membrane studied in rat liver cell... 

Essentially, this method is based on subjecting cell membranes to a short external electric field pulse of an intensity comparable to the electric field strength of the membrane 77). Under these conditions the membrane breaks down locally and becomes permeable. This process is reversible, i.e. the membrane reconstitutes its original properties in time intervals which can be experimentally controlled. 

BIOELECTROCHEMISTRY. Application of the principles and techniques of electrochemistry to biological and medical problems. It includes such surface and interfacial phenomena as the electrical properties of membrane systems and processes, ion adsorption, enzymatic clotting, transmembrane pH and electrical gradients, protein phosphorylation, cells, and tissues. 

The electrical properties of black lipid membranes (BLM s) have probably been studied more than those of other lipid systems because of the great similarity between BLM s and cell membranes. The electrical properties of BLM s were reviewed extensively by other authors (32, 33, 34, 35), and we shall therefore describe the electrical and physical properties of lipids which are not generally touched upon in connection with BLM s. We also concentrate on those properties which are intimately related to the different states of order in lipid systems. 

Fig. 17. a A scanning electron micrograph of square pores etched in a 3 micrometer thick silicon membrane. The pores were produced by anisotropic etching and their width on this side of the membrane is 6 pm. Cells (fibroblasts 3T3) attach to the surface and migrate over the pores, b Electrodes are placed on either side of the membrane and a constant current passed through it (mainly through the pores). The presence of cells is easily detected and movements of cell filopodia of less than 100 nm and the passive electric properties of the cell body can be determined by analysis of the signal fluctuations and impedance... 

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