scholarly journals The enduring legacy of the “constant-field equation” in membrane ion transport

2017 ◽  
Vol 149 (10) ◽  
pp. 911-920 ◽  
Author(s):  
Osvaldo Alvarez ◽  
Ramon Latorre
Keyword(s):  
Field Equation ◽  
Ion Transport ◽  
Historical Perspective ◽  
Ionic Composition ◽  
Constant Field ◽  
Seminal Paper ◽  
Ion Concentrations ◽  
The Relationship ◽  
Concise Expression ◽  
Membrane Ion Transport

In 1943, David Goldman published a seminal paper in The Journal of General Physiology that reported a concise expression for the membrane current as a function of ion concentrations and voltage. This body of work was, and still is, the theoretical pillar used to interpret the relationship between a cell’s membrane potential and its external and/or internal ionic composition. Here, we describe from an historical perspective the theory underlying the constant-field equation and its application to membrane ion transport.

scholarly journals Effect of acetylcholine on postjunctional membrane permeability in eel electroplaque.

1977 ◽  
Vol 70 (1) ◽  
pp. 23-36 ◽  
Author(s):  
N L Lassignal ◽  
A R Martin
Keyword(s):  
Field Equation ◽  
Membrane Potential ◽  
Membrane Permeability ◽  
Ionic Composition ◽  
Reversal Potential ◽  
Resting Potential ◽  
Constant Field ◽  
Free Solution ◽  
Positive Direction ◽  
External K

Acetylcholine (ACh) was applied iontophoretically to the innervated face of isolated eel electroplaques while the membrane potential was being recorded intracellularly. At the resting potential (about -85 mV) application of the drug produced depolarizations (ACh potentials) of 20 mV or more which became smaller when the membrane was depolarized and reversed in polarity at about zero membrane potential. The reversal potential shifted in the negative direction when external Na+ was partially replaced by glucosamine. Increasing external K+ caused a shift of reversal potential in the positive direction. It was concluded that ACh increased the permeability of the postjunctional membrane to both ions. Replacement of Cl- by propionate had no effect on the reversal potential. In Na+-free solution containing glucosamine the reversal potential was positive to the resting potential, suggesting that ACh increased the permeability to glucosamine. Addition of Ca++ resulted in a still more positive reversal potential, indicating an increased permeability to Ca++ as well. Analysis of the results indicated that the increases in permeability of the postjunctional membrane to K+, Na+, Ca++, and glucosamine were in the ratios of approximately 1.0:0.9:0.7:0.2, respectively. With these permeability ratios, all of the observed shifts in reversal potential with changes in external ionic composition were predicted accurately by the constant field equation.

Design, synthesis and membrane ion transport properties of cystine- and serine-based cyclo -4-oxa-heptane-1,7-bisamides

2002 ◽  
Vol 43 (29) ◽  
pp. 5145-5147 ◽  
Author(s):  
Darshan Ranganathan ◽  
Manoj P Samant ◽  
R Nagaraj ◽  
E Bikshapathy
Keyword(s):  
Ion Transport ◽  
Transport Properties ◽  
Design Synthesis ◽  
Membrane Ion Transport

scholarly journals The Effects of Alkali Metal Cations and Common Anions on the Frog Skin Potential

1964 ◽  
Vol 47 (4) ◽  
pp. 749-771 ◽  
Author(s):  
Barry D. Lindley ◽  
T. Hoshiko
Keyword(s):  
Alkali Metal ◽  
Frog Skin ◽  
Ionic Composition ◽  
Metal Cations ◽  
Leopard Frog ◽  
Constant Field ◽  
Alkali Metal Cations ◽  
Ionic Selectivity ◽  
Skin Potential ◽  
Mean Values

The effects on the potential difference across isolated frog skin (R. catesbeiana, R. pipiens) of changing the ionic composition of the bathing solutions have been examined. Estimates of mean values and precision are presented for the potential changes produced by substituting other alkali metal cations for Na at the outside border and for K at the inside border. In terms of ability to mimic Na at the outside border of bullfrog skin, the selectivity order is Li > Rb, K, Cs; at the outside border of leopard frog skin, Li > Cs, K, Rb. In terms of ability to mimic K at the inside border of bullfrog and leopard frog skin: Rb > Cs > Li > Na. Orders of anion selectivity in terms of sensitivity of the potential for the outside border of bullfrog skin are Br > Cl > NO3 > I > SO4, isethionate and of leopard frog skin are Br, Cl > I, NO3, SO4. An effect of the solution composition (ionic strength?) on the apparent Na-K selectivity of the outside border is described. The results of the investigation have been interpreted and discussed in terms of the application of the constant field equation to the Koefoed-Johnsen-Ussing frog skin model. These observations may be useful in constructing and testing models of biological ionic selectivity.

Language contact and multilingualism in Iran

2018 ◽  
Author(s):  
Shahrzad Mahootian
Keyword(s):  
Language Contact ◽  
Historical Perspective ◽  
Language Maintenance ◽  
Language And Identity ◽  
General Description ◽  
The Status ◽  
Bilingual Communities ◽  
The Relationship

Throughout its history, Iran has been a richly multilingual nation, with documented evidence reaching back nearly three millennia. Today, estimates of the number of languages spoken in modern Iran vary, with numbers ranging from fifty-four to seventy-six living languages. This chapter presents a general description of societal bilingualism, how bilingual communities come about, the relationship between language and identity in multilingual contexts, and how best to describe the kind(s) of bilingualism found in Iran, including the use of English. The chapter then turns to bilingualism in Iran from a historical perspective, with the goal of understanding why there are so many languages in present-day Iran. Finally, it addresses the status of English in pre- and post-revolutionary Iran and issues of language maintenance.

scholarly journals Molecular Dynamics Study of Ion Transport in Polymer Electrolytes of All-Solid-State Li-Ion Batteries

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1012
Author(s):  
Takuya Mabuchi ◽  
Koki Nakajima ◽  
Takashi Tokumasu
Keyword(s):  
Molecular Dynamics ◽  
Solid State ◽  
Ion Transport ◽  
Polyethylene Oxide ◽  
Polymer Electrolytes ◽  
Li Ion Batteries ◽  
Transport Mechanisms ◽  
Li Ion ◽  
Dynamics Simulations ◽  
The Relationship

Atomistic analysis of the ion transport in polymer electrolytes for all-solid-state Li-ion batteries was performed using molecular dynamics simulations to investigate the relationship between Li-ion transport and polymer morphology. Polyethylene oxide (PEO) and poly(diethylene oxide-alt-oxymethylene), P(2EO-MO), were used as the electrolyte materials, and the effects of salt concentrations and polymer types on the ion transport properties were explored. The size and number of LiTFSI clusters were found to increase with increasing salt concentrations, leading to a decrease in ion diffusivity at high salt concentrations. The Li-ion transport mechanisms were further analyzed by calculating the inter/intra-hopping rate and distance at various ion concentrations in PEO and P(2EO-MO) polymers. While the balance between the rate and distance of inter-hopping was comparable for both PEO and P(2EO-MO), the intra-hopping rate and distance were found to be higher in PEO than in P(2EO-MO), leading to a higher diffusivity in PEO. The results of this study provide insights into the correlation between the nanoscopic structures of ion solvation and the dynamics of Li-ion transport in polymer electrolytes.

scholarly journals Revisiting the Relationship between Financial Wealth, Housing Wealth and Consumption: A Panel Analysis for the US

2018 ◽  
Author(s):  
Dimitra Kontana ◽  
Fotios Siokis
Keyword(s):  
House Prices ◽  
Composite Index ◽  
Housing Wealth ◽  
Seminal Paper ◽  
Financial Wealth ◽  
Distribution Of Wealth ◽  
High Rise ◽  
The Us ◽  
Housing Investments ◽  
The Relationship

Based on the seminal paper of Case, Quigley and Shiller (2013), we investigate the effects of financial and housing wealth on consumption.  Using quarterly data from 1975 to 2016, for all States of U.S. economy, and a different methodology in measuring wealth, we report relatively greater financial effects than housing effects on consumption.  Specifically, in our basic utilized model, the calculated elasticity for financial wealth is 0.060, while for housing is 0.045.  The results are not in agreement with the ones obtained by Case, Quigley and Shiller.  In an attempt to investigate the disparity we proceed by incorporating the introduction of the Tax Reform Act in 1986, which increased incentives for owner-occupied housing investments.  Finally, due to distributional factors at work, and taking into account the pronounced uneven distribution of wealth we investigate the effects of wealth for 8 states that include the Metropolitan areas comprising of the well known Case-Shiller 10-City Composite Index.  Now the housing effect on consumption is much stronger and larger than the financial effect.  Additionally, we forecast the consumption changes at the time of the high rise and large drops in house prices for these states.  Forecasts showed a recession from the fall of Lehman Brothers until the fourth quarter of 2011.  These forecasts were not verified.  Probably, the new techniques used by politics played an important role.  We also find that extreme behaviors cannot be predicted.

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