Akira Inouye

A dielectric theory of “multi-stratified shell” model with its application to a lymphoma cell

Abstract A theory of complex dielectric constant ( e ∗ ) for the suspension of “multi-stratified” spherical particles is presented. Based on Maxwells theory of interfacial polarization, we derive a general expression which correlates e ∗ with the electrical and geometrical parameters of each stratum. It can be shown that such a “multi-stratified” system in general should give rise to multiple dielectric dispersions, the number of which corresponds to the number of interfaces lying between the successive shell phases. The conditions for a full number of different “unit” dispersions to occur are also discussed. As an example, a special case of the “double-shell” model consisting of a spherical core and three layers of concentric phases is solved numerically by using a set of parameter values pertinent to a lymphoma cell. In light of the characteristic behavior of e ∗ thus revealed, we propose a scheme of procedure that applies to the determination of electrical parameters associated with the specific “double-shell” model.

Electrical properties and active solute transport in rat small intestine

SummaryAddition ofd-glucose to the mucosal fluid resulted in a significant depolarization of the mucosal membrane potential (Vm) in rat duodenum, jejunum, and ileum accompanied by an increase in the transepithelial potential difference (PDt). On the other hand,l-glucose did not inducePDt andVm changes. Glycine applied from the mucosal side also inducedVm-depolarization andPDt-increment in the ileum. Phlorizin added to the mucosal fluid or ouabain added to the serosal fluid inhibited the sugar-dependent changes inPDt andVm.According to the analysis with an equivalent circuit model for the epithelium, it was concluded that an actively transported solute induced not only a depolarization of the mucosal (brush border) membrane but also a hyperpolarization of the serosal (baso-lateral) membrane of an epithelial cell, so that the origin of solute-inducedPDt changes should be attributed to changes in emfs at both membranes. The hyperpolarization of the serosal membrane in the presence of an actively transported solute was attributed to a mechanism of serosal electrogenic sodium pump stimulated by the increase in the extrusion rate of Na+ co-transported into the cell with sugar or amino acid.

Passive electrical properties of cultured murine lymphoblast (L5178Y) with reference to its cytoplasmic membrane, nuclear envelope, and intracellular phases

SummaryDielectric dispersion measurements over a frequency range 0.01–100 MHz were made with the suspensions of a cultured cell line, mouse lymphoma L5178Y, and an attempt to explain the observed dielectric behavior by taking explicitly into consideration the possible involvement of cell nucleus has been presented.The use of a conventional “single-shell” model in which the cell is represented by a homogeneous sphere coated with a thin limiting shell phase did not duplicate the observed dispersion curves, whereas a “double-shell” model in which one additional concentric shell is incorporated into the “single-shell” model gave a much better fit between the observed and the predicted dispersion curves. Based on the latter model, we analyzed the raw data of dielectric measurements to yield a set of plausible electrical parameters for the lymphoma cell:CM≅1.0μF/cm2,CN≅0.4μF/cm2, εk≅300, κc/κa≅0.9, and κk/κc≅0.7. Here,CM andCN are the specific capacities of plasma and nuclear membranes; ε and κ are the dielectric constant and conductivity with subscripta, c andk referring respectively to the extracellular, the cytoplasmic and the karyoplasmic phases.

Oscillations of membrane potential in L cells

SummaryEffects of divalent cations on oscillations of membrane potentials (i.e., spontaneous repetitive hyperpolarizing responses) and on hyperpolarizing responses induced by electrical stimuli as well as on resting potentials were studied in large nondividing L cells. Deprivation of Ca2+ from the external medium inhibited these hyperpolarizing responses accompanying slight depolarization of the resting potential. Sr2+ or Mn2+ applied to the external medium in place of Ca2+ was able to substitute for Ca2+ in the generation of hyperpolarizing responses, while Mg2+, Ba2+ or La3+ suppressed hyperpolarizing responses. The addition of A23187 to the bathing medium or intracellular injection of Ca2+, Sr2+, Mn2+ or La3+ induced membrane hyperpolarization. When the external Ca2+, Sr2+ or Mn2+ concentration was increased, the resting potential also hyperpolarized, in a saturating manner. The amplitude of maximum hyperpolarization produced by high external Ca2+ was of the same order of magnitude as those of hyperpolarizing responses and was dependent on the external K+ concentration. In the light of these experimental observations, it was deduced that the K+ conductance increase associated with the hyperpolarizing excitation is the result of an increase in the intracellular concentration of free Ca2+ mainly derived from the external solution.

Oscillations of membrane potential in L cells. I. Basic characteristics.

SummaryThe membrane potentials and resistances of L cells were measured using a standard electrophysiological technique. The values obtained in physiological media were around −15 mV and 37 MΩ, respectively. Almost all the large nondividing L cells (giant L cells) showed spontaneous oscillations of the membrane potential between around −15 and −40 mV. Application of an appropriate electrical or mechanical stimulus was also capable of eliciting responses but such were usually induced only once. The total membrane conductance increased significantly and in parallel with such a hyperpolarizing response. Cooling of the cells and application of metabolic inhibitors to the cells completely blocked the spontaneous oscillation despite the fact that the electrically induced hyperpolarizing response remained. Intracellular K+, Na+ and Cl− concentrations were measured by means of a flame photometer and a chloridometer, and the equilibrium potential for each ion was estimated.

Electrical properties and active solute transport in rat small intestine. II. Conductive properties of transepithelial routes.

SummaryThe transepithelial resistance, the cell membrane resistance and the ratio of resistances of the serosal (baso-lateral) to the mucosal (brush border) cell membrane were measured in rat duodenum, jejunum and ileum by means of microelectrode techniques. These measured values were not affected in the presence of actively transported solutes in the mucosal bathing fluid.Contribution of an electrical conductance through the extracellular shunt pathway to the total transepithelial conductance was quantitatively estimated using an electrically equivalent circuit analysis. These values estimated in respective tissues of small intestine were approx. 95% of the total transepithelial conductance, remaining unaffected by an active solute transport.From these data, the changes in emfs of the mucosal and serosal membrane induced byd-glucose or glycine were separately evaluated.

Perfusion of frog's spinal cord as a convenient method for neuropharmacological studies

Abstract The isolated spinal cord of the bull frog was perfused through the anterior spinal artery. Under physiological conditions, the tissue survived for several hours and the spike potential of motorneurons, reflexes and ventral or dorsal root potentials remained constant during this time. This type of perfusion has the following advantages: it is simple to handle, the ionic environment of the neurons is easily controlled and small amounts of substances or substances which are weak in action can be tested.

Effects of potassium ions and sodium ions on membrane potential of epithelial cells in rat duodenum

1. Mucosal and serosal membrane potentials (Vm and Vs) of epithelial cells in rat duodenum were recorded together with the transmural potential differences (PDt). 2. The value of Vm in rat duodenum at 37 degrees C was about -53mV, being considerably greater than the values reported hitherto for the small intestine of various species. 3. When Cl- in the mucosal medium was partially replaced with SO42- at fixed mucosal Na+ and K+ concentrations ([Na+]m and [K+]m), the membrane potential was scarcely affected in the steady state several minutes after replacement, whereas marked changes in the potential were observed with varying [K+]m or [Na+]m. 4. As the mucosal K+ concentration increased at constant [Na+]m, Vm was gradually decreased (depolarization), together with the increase in PDt. Such a change in Vm caused by varying [K+]m obeys Nernsts equation in the range of [K+]m higher than about 60 mM. 5. At constant [K+]m, an increase in [Na+]m also caused the decrease of Vm for the lower [K+]m region, whereas Vm was not affected by such changes in [Na+]m in the range of [K+]m higher than approx. 60 mM. 6. The values of PNa/PK were obtained from the modified Goldman equation under an appropriate assumption. The ratio of the permeability coefficients markedly increases from zero to approx. 0.07 with a decrease in [K+]m.

Calcium-binding of synaptosomes isolated from rat brain cortex: IV. Effects of ruthenium red on the co-operative nature of calcium-binding

SummaryRuthenium red combines with isolated synaptosomes, resulting in strong inhibition of their Ca2+-binding. In isotonic saline media, however, the dye-induced inhibition of Ca2+-binding is significantly greater than that expected for the amount of bound dye and Hills exponent of the Ca2+-binding decreases to 1 with an increase in the amount of the dye bound. On the other hand in isotonic mannitol-sucrose solution, inhibition of synaptosomal Ca2+-binding brought about by the dye is proportional to the amount of dye bound. Based on these results, the effects of the dye on the co-operative nature of synaptosomal Ca2+-binding is discussed.

Calcium-binding of synaptosomes isolated from rat brain cortex

SummaryCa++ concentration in the synaptosomal suspension was measured to determine the liberation from and binding to isolated brain cortex synaptosomes by utilizing a dual wavelength spectrophotometer to monitor the absorbance changes of murexide raised by Ca++. When synaptosomes were suspended in isotonic solutions of a NaCl−KCl mixture containing more than 30 to 40mM of KCl, a marked liberation of calcium ion was observed in proportion to the rise in KCl concentration, whereas there was rarely any significant release of Ca++ observed with an external KCl concentration of less than 20mM. Titration of the synaptosomal suspension with Ca++ revealed that, in the absence of external K+, a part of added Ca++ was almost instantaneously bound to the synaptosomal particles so far as these particles had not been saturated with Ca++. Such a Ca++-binding was markedly depressed by a higher external K+ concentration. Ouabain and cyanide did not have that effect on such a K+-induced inhibition of Ca++-binding. The present results indicate that the inhibition of Ca++-binding by high external K+ concentration probably results from a change in synaptosomal membrane which is of a cooperative nature.