Ion Transport Phenomena Research Articles

Electromagnetic modulation of biological processes: Chemical, physical and biological correlations in the Ca-uptake by embryonal chick tibia in vitro

Ca-uptake by embryonal chick tibia in short-term culture is herewith used as an empirical model to probe the coupling of electromagnetic signals with biological processes. Tibiae from 8- to 10-day-old chick embryos were incubated 60 to 120 minutes in media of given composition at 37.5±0.5°C in the presence of 45Ca, either inside or outside a very low frequency pulsating electromagnetic field. Ca-uptake by the chick tibia rudiment was best determined by 45Ca counting in aliquots of the culture medium. The field produced an increase in Ca-uptake only in the presence of sufficient quantities of bicarbonate, which was also the most effective of the ions to bring about Ca-uptake outside the field (bicarbonate > phosphate > chloride > acetate). Pharmacologic agents, as ethanol, Mg 2+, and NaF, stimulated the positive effect of the field on Ca-uptake, but only in the presence of bicarbonate. The magnitude of the effect was also dependent on the characteristics of the induced electromagnetic signal, whereby the dose-response curves had peaks at certain signal amplitudes. No molecular mechanisms have been as yet identified for the observed electromagnetic effects. However, because of the passivity of non-living systems, it is clearly the Ca-uptake by living tissue that is being modified by the pulsating electromagnetic field. Probable candidates in the electromagnetic coupling that results in an increased Ca-uptake may have to be found in the membrane processes of active ion transport and related phenomena.

Electromagnetic modulation of biological processes: Chemical, physical and biological correlations in the Ca-uptake by embryonal chick tibia in vitro

Abstract Ca-uptake by embryonal chick tibia in short-term culture is herewith used as an empirical model to probe the coupling of electromagnetic signals with biological processes. Tibiae from 8- to 10-day-old chick embryos were incubated 60 to 120 minutes in media of given composition at 37.5±0.5°C in the presence of 45Ca, either inside or outside a very low frequency pulsating electromagnetic field. Ca-uptake by the chick tibia rudiment was best determined by 45Ca counting in aliquots of the culture medium. The field produced an increase in Ca-uptake only in the presence of sufficient quantities of bicarbonate, which was also the most effective of the ions to bring about Ca-uptake outside the field (bicarbonate > phosphate > chloride > acetate). Pharmacologic agents, as ethanol, Mg2+, and NaF, stimulated the positive effect of the field on Ca-uptake, but only in the presence of bicarbonate. The magnitude of the effect was also dependent on the characteristics of the induced electromagnetic signal, whereby the dose-response curves had peaks at certain signal amplitudes. No molecular mechanisms have been as yet identified for the observed electromagnetic effects. However, because of the passivity of non-living systems, it is clearly the Ca-uptake by living tissue that is being modified by the pulsating electromagnetic field. Probable candidates in the electromagnetic coupling that results in an increased Ca-uptake may have to be found in the membrane processes of active ion transport and related phenomena.

The active magnetospheric particle tracer explorers (AMPTE) program

The Active Magnetospheric Particle Tracer Explorers (AMPTE) will carry out the release and monitoring of tracer ions (lithium and barium) in the solar wind and within the distant magnetosphere in order to study access of solar wind ions to the magnetosphere and the convective‐diffusive transport and energization of magnetospheric particles. In addition, a single massive release of barium in the dawn magnetosheath will create a visible artificial comet in the flowing solar wind plasma within which studies of diamagnetic effects, ionization, momentum exchange, ion transport, and visible phenomena will be made. The AMPTE spacecraft will also obtain comprehensive measurements of the composition and dynamics of the ambient Z≥2 magnetospheric particle populations at the geomagnetic equator, including the energy interval (˜20 to ˜200 keV) of importance to the ring current. Implementation of these objectives utilizes two primary spacecraft, the Ion Release Module (IRM) and the Charge Composition Explorer (CCE), launched into elliptical orbits of apogee 19.5 RE and 9.0 RE, respectively. A supporting instrumented spacecraft, the United Kingdom Subsatellite, positioned a few hundred kilometers from the IRM, provides two‐point in situ plasma diagnostic measurements. All three spacecraft are currently scheduled for launch on a Delta 3924 vehicle in August 1984. The AMPTE program is a collaborative effort between the United States and the Federal Republic of Germany (FRG) and between Germany and the United Kingdom (UK).

Short range order and glass transition in AgIAg 2OB 2O 3 vitreous electrolytes

Several experimental techniques are used to study the short range order, the dynamics and the glass transition in AgIAg 2B 2O 3 compounds. Addition of Ag 2O to B 2O 3, up to [Ag 2O]/[B 2O 3] ⩽0.5 modifies the borate network by creating a BO 4 unit for each silver added. Addition of AgI decreases the glass transition temperature ( T g) but has only minor effects on the short range structure of the borate network. Silver iodide is partially accomodated in the interstices of the glass network. The relationship among a tentative structural picture, the ion transport phenomena and the low temperature dynamics are discussed. An investigation of the dynamics in the AgI·Ag 2O·2B 2O 3 glass near and above T g is presented. With NMR techniques, we monitor the onset of tumbling of the borate units and the dynamical effects of crystallization and/or aging of the glass. Hysteresis effects in the ionic conductivity (σ) temperature dependence and the non-Arrhenian behavior of σT near T g are interpreted in terms of structural modifications occurring at elevated temperatures in the glass.

Solid State Ionics Vol 1

(An interdisciplinary journal devoted to experimental and theoretical research involving properties related to ionic transport phenomena in solids) M Stanley Whittingham (ed) 1980 Amsterdam: North-Holland xiv + 161 pp price $74.75 (for 6 issues during 1980) This new journal deals with the physics, chemistry and materials science of ion transport phenomena in solids. It is timely and welcome since this is a fast growing field, particularly as there is very considerable interest in the practical development of solid electrolytes for use in high energy density batteries.

Fast ion transport in oxide glasses

The discovery of fast ion transport in solids has in recent years stimulated much interest in the scientific community both with regard to obtaining improved understanding of the phenomenon and applying such materials in advanced battery systems. More recently the phenomenon of fast ion transport has also been observed to occur in increasing numbers of amorphous systems. In this paper we review recent transport data obtained in over 100 glasses which appear to exhibit exceptionally high Ag, Li, Na and F ion conductivities at temperatures far from the melting points. We also include results recently obtained in our laboratory for glasses in the lithium borate system. Common characteristics of these glasses are summarized and are compared with predictions of classical diffusion theory. Relatively low and composition-independent values of σ 0 indicate poor agreement with a simple isolated-ion diffusion model, while composition-dependent activation energies are related to structural changes. Some glasses share similar properties with their crystalline counterparts while others do not. This is discussed in terms of the relative disorder already existing within the crystals. The need for improved characterization of glasses is also discussed.

Vasoactive intestinal polypeptide: Increased tone, enhancement of acetylcholine release, and stimulation of adenylate cyclase in intestinal smooth muscle

Vasoactive intestinal polypeptide (VIP) was examined in vitro for effects on tone and neuronal release mechanisms in intestinal smooth muscle since this is a site of high peptide concentration. VIP contracted the guinea pig ileum and rabbit jejunum in concentrations ranging from 10 −9 to 10 −7 M. Increased tone in the guinea pig ileum was partially antagonized by the anticholinergic agent, atropine (4.38 × 10 −6 M) suggesting that one component of the contractile response was due to the indirect release of acetylcholine. The H 1 receptor antagonist, pyrilamine, did not alter the increased tone produced by VIP indicating that histamine release did not contribute to the ileal contractile response and that VIP exerted a selective effect to enhance neuronal release of acetylcholine. The ability of VIP to modulate acetylcholine release was confirmed in field stimulated ileal preparations where VIP increased the force developed to endogenously released acetylcholine without altering the direct response to acetylcholine. In rabbit jejunum and ileal smooth muscle, VIP related cyclic AMP levels. However, inhibition of phosphodiesterase with papaverine did not potentiate either the VIP-induced ileal contraction or enhancement of the field stimulated response. This raises the possibility that increases in intestinal cyclic AMP may be involved more in VIP-induced alterations in ion transport or secretory phenomenon than in intestinal motility. These studies describing the ability of VIP to modulate acetylcholine release and to increase ileal tone are consistent with the proposed role of VIP in intestinal patholgies involving excessive mucous secretion and motility.

Insecticides affecting ion transport

Ion transport phenomena have been reviewed and shown to be an integral part of many physiological processes in the nervous system including peripheral nerve, synaptic junctions and neuromuscular connections. Many instances where insecticides have been demonstrated by neurophysiological and/or biochemical techniques to interfere with ion transport processes have been indicated. In particular, organochloine insecticides have been demonstrated to alter the ability of excitable tissue in regard to selective permeability of Na + and K + ions associated with the action potential of a propagated impulse. In neuromuscular junctions a variety of insecticides appear to upset the binding of Ca + with the sarcoplasmic reticulum. Transmitter release associated with ion transport was also reported to be affected by certain insecticides and other pesticides. Description of attempts to elucidate the biochemical basis for the alteration in ion movements as observed by neurophysiological techniques were described. A major emphasis of the biochemical approaches included studying ATPase enzymes. These enzymes are involved in various aspects of ion transport and indeed inhibition of ATPase associated with the sarcoplasmic reticulum was claimed to be involved with muscle contractions caused by the insecticides. Aspects of inhibition of ATPases in peripheral nerve were described and in particular a Ca + sensitive ATPase that was inhibited by DDT at low concentrations was reported. Correlations between this enzyme and the resurfacification of Ca 2+ on the axonic membrane were presented as a possible mode of action of DDT in peripheral nerve. Problems of insecticides affecting ion transport are of interest from the viewpoint of basic physiology in that these compounds can and have been used as tools to study physiological processes. These studies are also of importance in determining the safety and acute and chronic toxicity of insecticides.

Bilayer Lipid Membranes

AbstractThin lipid membranes formed across an aperture in a teflon foil are frequently used as model systems to simulate the hydrophobic diffusion barrier of biological membranes. These membranes have a thickness of about twice the length of a lipid molecule (bilayer membranes) and are prepared either by a spontaneous transition of a thick lamella made from a solution of lipids in a hydrocarbon [1] or by a direct “addition” of two monomolecular lipid layers on the two water surfaces separated by the teflon foil [2]. The aqueous phases on both sides of these planar membranes are easily accessible by electrodes which may serve to study the electrical properties of the membranes. The whole system allows the application of steady state electrical methods as well as that of fast relaxation methods. The latter include the voltage jump‐current relaxation technique [3,6], the charge pulse method [4,5] as well as the temperature jump method [6]. These kinetic techniques have been used throughout recent years to investigate ion transport phenomena across bilayer lipid membranes.Unmodified lipid membranes have been found to represent high energy barriers for the movement of inorganic cations and anions. A simple equivalent electrical circuit of the membrane consists of a parallel arrangement of the membrane resistance RM and the membrane capacitance CM (typical values: RM = 106‐108μcm2, CM = 0.3‐0.8μF/cm2). A refined version composed of three of such elements (one for the hydrocarbonlike membrane interior, the two others for the polar membrane‐water interfaces) has been suggested on the basis of a.c. measurements [7]. These measurements were, however, confined to the rather small band width of 0.1‐100 Hz. A different possibility of testing such a circuit is to make use of the voltage jump method. The induced current relaxation may be measured with a time resolution of at least 1 μs and very high sensitivity by using signal averaging techniques. For the three element circuit described above the relaxation should consist of two exponential terms. At least five different relaxation times were, however, necessary to obtain a sufficiently good fit to the experimental data [8.9]. This finding indicates that even the refined equivalent circuit is insufficient for a phenomenological description of the high frequency behaviour of bilayer lipid membranes. The complex current relaxation may be interpreted on the basis of cooperative dielectric relaxation phenomena associated with the dipoles of the polar head groups of the lipid molecules.

Cole-Cole diagrams of ionic hopping systems

A hopping conduction mechanism is proposed for the mobile ions in evaporated silicon oxide films. The Cole-Cole diagram, calculated numerically, is identical to that of a simple Debye relaxation mechanism. The hopping conduction mechanism can also be combined with surface trapping, which gives rise to Cole-Cole diagrams similar to those found experimentally. Lastly it is shown that the hopping conduction model is closely related to a drift-diffusion mechanism, which has also been used to describe ion transport phenomena in thin insulating films.

Investigation of the Kinetics of Proton Translocation across the thylakoid membrane

When isolated chloroplasts from spinach are illuminated, protons are pumped across the thylakoid membrane into the inner phase of the thylakoid vesicles. This inward proton translocation is accompanied by the translocation of other ions. The light-induced ion redistribution is analyzed and a model for ion transport phenomena is deduced. The influence of surface-charge changes are taken into account. The effect of the membrane-permeability-inducing agents valinomycin (K + specific) and carbonylcyanid- m-chlorophenylhydrazone (H + specific) on the kinetics of proton translocation is studied and analyzed.

Transport of Pb Ions at the Interface Between Silicate Glass and Molten Lead

The influence of an external dc electric field on the Pb content near the interface between float glass and molten Pb was studied at 500°C. The diffusion coefficient and velocity of Pb ions in the external electric field were determined, and the theoretical time dependence of Pb content in the glass was calculated. A theoretical model of ion transport phenomena in the system is suggested.

Electrical Behaviour of Langmuir Films: A Review, Part II

The electrical behaviour of thin films obtained by a variety of processes, e.g. thermal evaporation in vacuum, has been extensively studied. The study of organic mono- and multilayer films obtained by the Blodgett–Langmuir technique (commonly referred to as Langmuir films), however, has gained considerable momentum only during the past decades. Unlike evaporated films, the stiking features of these organic films are their controllable thicknesses down to one monolayer (~25 Å) and the possibility of obtaining them free from holes and conducting imperfections. The aim of this paper is to describe the film deposition techniques, some of the properties of the films so obtained and to review their electrical behaviour. It is also intended to make this review a comprehensive and up-to-date source of information for those who are either already engaged in this field or are planning to adopt Langmuir films for future investigations.In this survey, emphasis is put on the possible problems worth further study to get more insight into the basic properties of these films. Further, since the latter possess some interesting electrical properties, this paper may prove useful in the assessment of our depth of knowledge about them and in reducing the existing gap between basic research and technological applications. Their potential usefulness in developing devices is therefore also discussed.The survey has been divided into two parts. Part I was concerned with deposition techniques, the physical properties of Langmuir films and certain electrical properties, namely dielectric behaviour and electrical conduction phenomena. This second part is concerned with electrical breakdown behaviour, voltage induced changes in electrical behaviour (forming) and ionic transport phenomena in the films and finishes, with suggestions as to future trends in work with such films together with a summary of possible applications.To assist the reader, the two parts have been numbered consecutively with regard to sections of the text, figures and references. “Appropriate” references already cited in Part I are given again at the end of this part.

Electrical Behaviour of Langmuir Films: A Review, Part I

The electrical behaviour of thin films obtained by a variety of processes, e.g. thermal evaporation in vacuum, have been extensively studied. However, the study of organic mono- and multilayer films obtained by the Blodgett–Langmuir technique (commonly referred to as Langmuir films) has gained considerable momentum only during the past decades. Unlike evaporated films, the striking features of these organic films are their controllable thicknesses down to one monolayer (~ 25 Å) and the possibility of obtaining them free from holes and conducting imperfections. The aim of this paper is to describe the film deposition techniques, some of the properties of the films so obtained and to review their electrical behaviour. It is also intended to make this review a comprehensive and up-to-date source of information for those who are either already engaged in this field or are planning to make Langmuir films the subject for future investigations.In this survey, emphasis is put on problems worth further study to obtain greater insight into the basic properties of these films. Further, since they possess some interesting electrical properties, this paper may prove useful in the assessment of our depth of knowledge about them and in reducing the existing gap between basic research and technological applications. Thus their potential usefulness in the development of devices is also discussed.The survey is divided into two parts. Part I is concerned with deposition techniques, the physical properties of Langmuir films and certain electrical properties, namely dielectric behaviour and electrical conduction phenomena. Part II, which will appear in the next issue, will be concerned with electrical breakdown behaviour, voltage induced changes in electrical behaviour (forming) and ionic transport phenomena in the films and will finish with suggestions as to future trends in work with such films together with a summary of possible applications.To assist the reader, the two parts have been numbered consecutively with regard to sections of the text, figures and references.

Ion transport and oscillatory phenomena in monolayers adsorbed on electrodes

The method of anodic stripping (inverse polarography) was used to study the transport of ions (K +, Na +, Cs +, Cl −, Br −) across monolayers of n-alkyl quaternary ammonium compounds, adsorbed at the respective amalgam | water and mercury halide | water interfaces. These monolayers have different permeability for the different cations; Cs + being the most permeable. Phase-sensitive a.c. polarography was employed to determine the differential capacitance of the electrical double layer in the presence of the adsorbed monolayer. During the anodic stripping of amalgams in the presence of monolayers of octadecyltrimethylammoniuum chloride and eicosanyltrimethylammonium chloride sustained oscillations of the electrode potential were observed. The frequency varies from about 0.3 Hz to I.0 Hz, and depends on the c.d. the duration of the anodic stripping, the composition of the monolayer and the temperature. The amplitude of the oscillations varies from I00 to 500 mV. The transport of Cl − and Br − was studied across adsorbed monolayers of long chain quaternary ammonia and carboxylic acids and of polyglutamic acid at the mercury halide | water interface. The anionic permeability depends on the type of anion, the composition of the monolayer, the charge density of the monolayer and the interface. Ion transport is correlated with the packing in the monolayer.

Enhanced heat flux in non-uniform electric fields

Heat transfer by convection from a thin wire to a liquid was very appreciably increased by the application of a non-uniform electric field of several hundred kilovolts per centimetre which was confocal with the temperature field. This enhancement of the heat flux was much larger in a polar, slightly conducting liquid than in a practically ion-free liquid; the behaviour of a non-polar liquid which contained traces of a polar impurity was intermediate between the two. The polarity of the electric field affected the magnitude of the enhancement of the heat flux in the polar liquid and to a lesser extent also in the non-polar liquid which had a slight content of a polar contamination, but the direction of the field had no influence what­-soever on the enhancement of the heat flux in the ion-free liquid. With each of these three liquids the electrostatic field delayed and even suppressed the transition to nucleate boiling and therefore reduced the risk of ‘burn-out'. It appears that dielectrophoresis is primarily responsible for the increased convection, but that an ion transport phenomenon can make a further significant contribution. The observed polarity effects, in the presence of a minute concentration of ions, suggest that this could be an ion wind. For large values of the elec­trical number ( El ) the incremental increase of the Nusselt number ( Nu ) by dielectrophoresis can be of the order of one hundred.

Ionic transport in super ionic conductors: a theoretical model

Ionic solids exhibiting exceptionally high levels of ionic conductivity are found among the cation disordered ionic compounds of the silver halide-chalcogenide type, the various cation substituted beta aluminas, and certain defect-stabilized ceramic oxides. We present in this paper a theoretical model for ionic transport phenomena in such “super” ionic conductors. The model is based on the hypothesis that there exists in the ionic conductor an energy gap ϵ 0 above which ions of mass M, belonging to the conducting species, can be thermally excited from localized ionic states to free-ion like states in which an ion propagates throughout the solid with a velocity v m and energy ϵ m = 1 2 M v m 2 . On account of the interaction with the rest of the solid such an excited free-ion like state is supposed to have a finite life-time τ m . On the basis of a postulated Boltzmann transport equation for the thermal occupations of the various free-ion like states, simple expressions are derived for the ionic conductivity σ, thermal conductivity K I , and thermoelectric power Q. The theoretical result for Q is well substantiated by available experimental data. The result for σ may be used to deduce empirical values for the characteristic “mean-free path”, l 0 = v 0 τ 0, of the free-ion like state excited at the gap entry ϵ 0. The characteristic life-time τ 0 could be deduced in principal from measurements of the frequency dependent ionic conductivity σ(ω) which, according to the model, should be of the Drude type.

Conformational model of active transport: role of protons.

A conformational model of monovalent cation transport in mitochondria is described. Because it incorporates the proton-generated membrane potential and pH differential of the chemiosmotic model, the model successfully rationalizes a wide variety of mitochondrial ion-transport phenomena.

Transport Phenomena in Partially Ionized Cesium

An analysis of electron and ion transport phenomena in cesium plasma is developed in a form consistent with experimental conditions typical of those in thermionic and magnetohydrodynamic energy converters and other cesium discharges. Particular attention is given to electron collision processes which are shown to influence significantly both electron and ion transport phenomena. Using available electron cross-section data, electron and ion transport coefficients are evaluated as a function of electron temperature and fractional ionization. Results are then applied to the plasma of a low-pressure nonuniform thermionic arc. Experimentally determined spatial variations of electron density and electron temperature are analyzed numerically and quantitative estimates are made of the spatial variation of electric field intensity, ion current density, and net charged particle production rate. The inferred production rate is compared with that evaluated using a nonequilibrium kinetic analysis developed by Norcross and Stone.

Oscillations at the Anode of Low Pressure Sodium Lamps

Aanalysis of the anode voltage pulsations for low pressure sodium lamps containing starting rare gases is made with regard to the electron temperature of positive column plasmas. The electron temperature and the anode voltage pulsations of sodium lamps at the wall tempernture 0 to 150°C are related to ionization of rare gases alone, on the contrary the electron temperature at the wall temperature of more than about 150°C is inversely proportional to the vapor pressure of sodium while the anode voltage pulsations are still caused by ionization of rare gas alone from transport phenomena of sodium ions and no pulsations over 250°C. The electron currents in the anode sheaths converge to the hot spots on barium oxide compound layers of double coiled anodes, and consequently cause abrupt ionization around the hot spots of anodes, followed stoppage of the ionization immediatly by quenching of anode sheaths partially with high density charges generated locally. That is followed to recover for the anode drop voltage by ambipolar diffusion of high density local charges and reconbination of them at the walls of tubes. It is shown that the periods (T) of anode voltage pulsations are related to the mean decay time constant (τ) of ambipolar diffusion, T∝τ=γa2/π2Da where γa is radius of anode bulb-wall and Da is ambipolar diffusion constant; and that the electrode life and D lines may be shortened more by anode voltage pulsation of rare gas than by sodium vapor.