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Physiological Research 2002Mitochondria are involved in cellular functions that transcend the traditional role of these organelles as the energy factory of the cell. Their relative inaccessibility... (Review)
Review
Mitochondria are involved in cellular functions that transcend the traditional role of these organelles as the energy factory of the cell. Their relative inaccessibility and the difficulties involved in attempts to study them in their natural environment -- the cytosol -- has delayed much of this understanding and they still have many secrets to yield. One of the relatively new fields in this respect is undoubtedly the analysis of mitochondrial membrane potential. The realization that its alteration may have important pathophysiological consequences has led to an increased interest in measuring this variable in a variety of biological settings, including cardiovascular diseases. Measurements of mitochondrial membrane potential tell us much about the role of mitochondria in normal cell function and in processes leading to cell death. However, we must be aware of the limitations of using isolated mitochondria, single cells and different fluorescent indicators.
Topics: Animals; Membrane Potentials; Mitochondria; Myocytes, Cardiac
PubMed: 12470194
DOI: No ID Found -
International Journal of Molecular... Sep 2015Membrane potentials display the cellular status of non-excitable cells and mediate communication between excitable cells via action potentials. The use of genetically... (Review)
Review
Membrane potentials display the cellular status of non-excitable cells and mediate communication between excitable cells via action potentials. The use of genetically encoded biosensors employing fluorescent proteins allows a non-invasive biocompatible way to read out the membrane potential in cardiac myocytes and other cells of the circulation system. Although the approaches to design such biosensors date back to the time when the first fluorescent-protein based Förster Resonance Energy Transfer (FRET) sensors were constructed, it took 15 years before reliable sensors became readily available. Here, we review different developments of genetically encoded membrane potential sensors. Furthermore, it is shown how such sensors can be used in pharmacological screening applications as well as in circulation related basic biomedical research. Potentials and limitations will be discussed and perspectives of possible future developments will be provided.
Topics: Action Potentials; Animals; Animals, Genetically Modified; Biosensing Techniques; Cardiovascular System; Fluorescence Resonance Energy Transfer; Gene Expression; Genes, Reporter; Humans; Membrane Potentials; Myocytes, Cardiac; Recombinant Fusion Proteins; Research; Voltage-Sensitive Dye Imaging
PubMed: 26370981
DOI: 10.3390/ijms160921626 -
Advances in Physiology Education Mar 2021The ability to understand the relationship between the reversal potential and the membrane potential is a fundamental skill that must be mastered by students studying...
The ability to understand the relationship between the reversal potential and the membrane potential is a fundamental skill that must be mastered by students studying membrane excitability. To clarify this relationship, we have reframed a classic experiment carried out by Hodgkin and Katz, where we compare graphically the membrane potential at three phases of the action potential (resting potential, action potential peak, and afterhyperpolarization) to reversal potential for K (), reversal potential for Na (), and membrane potential () (calculated by the Goldman Hodgkin Katz equation) to illustrate that the membrane potential approaches the reversal potential of the ion to which it is most permeable at that instant.
Topics: Action Potentials; Cell Membrane Permeability; Humans; Membrane Potentials; Models, Biological; Permeability; Potassium
PubMed: 33661050
DOI: 10.1152/advan.00188.2020 -
The Journal of Physiological Sciences :... Jul 2016Throughout our investigations on the ontogenesis of the electrophysiological events in early embryonic chick hearts, using optical techniques to record membrane... (Review)
Review
Throughout our investigations on the ontogenesis of the electrophysiological events in early embryonic chick hearts, using optical techniques to record membrane potential probed with voltage-sensitive dyes, we have introduced a novel concept of "functiogenesis" corresponding to "morphogenesis". This article gives an account of the framework of "functiogenesis", focusing on the cardiac pacemaker function and the functional organization of the pacemaking area.
Topics: Animals; Chick Embryo; Electrophysiological Phenomena; Heart; Membrane Potentials; Myocardial Contraction
PubMed: 26719289
DOI: 10.1007/s12576-015-0431-2 -
Journal of Molecular and Cellular... Jan 2010Cardiac I(K1) and I(KACh) are the major potassium currents displaying classical strong inward rectification, a unique property that is critical for their roles in... (Review)
Review
Cardiac I(K1) and I(KACh) are the major potassium currents displaying classical strong inward rectification, a unique property that is critical for their roles in cardiac excitability. In the last 15 years, research on I(K1) and I(KACh) has been propelled by the cloning of the underlying inwardly rectifying potassium (Kir) channels, the discovery of the molecular mechanism of strong rectification and the linking of a number of disorders of cardiac excitability to defects in genes encoding Kir channels. Disease-causing mutations in Kir genes have been shown experimentally to affect one or more of the following channel properties: structure, assembly, trafficking, and regulation, with the ultimate effect of a gain- or a loss-of-function of the channel. It is now established that I(K1) and I(KACh) channels are heterotetramers of Kir2 and Kir3 subunits, respectively. Each homomeric Kir channel has distinct biophysical and regulatory properties, and individual Kir subunits often display different patterns of regional, cellular, and membrane distribution. These differences are thought to underlie important variations in the physiological properties of I(K1) and I(KACh). It has become increasingly clear that the contribution of I(K1) and I(KACh) channels to cardiac electrical activity goes beyond their long recognized role in the stabilization of resting membrane potential and shaping the late phase of action potential repolarization in individual myocytes but extends to being critical elements determining the overall electrical stability of the heart.
Topics: Action Potentials; Animals; Heart; Humans; Membrane Potentials; Models, Biological; Myocardium; Potassium Channels, Inwardly Rectifying
PubMed: 19703462
DOI: 10.1016/j.yjmcc.2009.08.013 -
Small (Weinheim An Der Bergstrasse,... Jul 2017All cells have a resting membrane potential resulting from an ion gradient across the plasma membrane. The resting membrane potential of cells is tightly coupled to...
All cells have a resting membrane potential resulting from an ion gradient across the plasma membrane. The resting membrane potential of cells is tightly coupled to regeneration and differentiation. The ability to control this parameter provides the opportunity for both biomedical advances and the probing of fundamental bioelectric pathways. The use of poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) conducting polymer microwires to depolarize cells is tested using E. coli cells loaded with a fluorescent dye that is pumped out of the cells in response to depolarization; a more positive membrane potential. Fluorescence imaging of the cells in response to a conducting-polymer-microwire applied voltage confirms depolarization and shows that the rate of depolarization is a function of the applied voltage and frequency. Microwire activity does not damage the cells, demonstrated with a propidium iodide assay of membrane integrity. The conducting polymer microwires do not penetrate the cell, or even come into contact with the cell; they only need to generate a minimum electric field, controlled by the placement of the wires. It is expected that these microwires will provide a new, noninvasive, cellular-scale tool for the control of resting membrane potential with high spatial precision.
Topics: Bridged Bicyclo Compounds, Heterocyclic; Membrane Potentials; Polymers; Polystyrenes
PubMed: 28556571
DOI: 10.1002/smll.201700789 -
FASEB Journal : Official Publication of... Dec 2019Cell membrane potential and inorganic ion distributions are currently viewed from a kinetic electric paradigm, which ignores thermodynamics. The resting membrane...
Cell membrane potential and inorganic ion distributions are currently viewed from a kinetic electric paradigm, which ignores thermodynamics. The resting membrane potential is viewed as a diffusion potential. The 9 major inorganic ions found in blood plasma (Ca, Na, Mg, K, H, Cl, HCO, HPO, and HPO) are distributed unequally across the plasma membrane. This unequal distribution requires the energy of ATP hydrolysis through the action of the Na-K ATPase. The cell resting membrane potential in each of 3 different tissues with widely different resting membrane potentials has been shown to be equal to the Nernst equilibrium potential of the most permeant inorganic ion. The energy of the measured distribution of the 9 major inorganic ions between extra- and intracellular phases was essentially equal to the independently measured energy of ATP hydrolysis, showing that the distribution of these 9 major ions was in near-equilibrium with the Δ' of ATP. Therefore, thermodynamics does appear to play an essential role in the determination of the cell resting membrane potential and the inorganic ion distribution across the plasma membrane.-Veech, R. L., King, M. T., Pawlosky, R., Bradshaw, P. C., Curtis, W. Relationship between inorganic ion distribution, resting membrane potential, and the Δ' of ATP hydrolysis: a new paradigm.
Topics: Adenosine Triphosphate; Animals; Humans; Hydrolysis; Ions; Membrane Potentials; Sodium-Potassium-Exchanging ATPase; Thermodynamics
PubMed: 31690124
DOI: 10.1096/fj.201901942R -
Medical & Biological Engineering &... May 2015Outer hair cell electromechanics, critically important to mammalian active hearing, is driven by the cell membrane potential. The membrane protein prestin is a crucial...
Outer hair cell electromechanics, critically important to mammalian active hearing, is driven by the cell membrane potential. The membrane protein prestin is a crucial component of the active outer hair cell's motor. The focus of the paper is the analysis of the local membrane potential and electric field resulting from the interaction of electric charges involved. Here the relevant charges are the ions inside and outside the cell, lipid bilayer charges, and prestin-associated charges (mobile-transferred by the protein under the action of the applied field, and stationary-relatively unmoved by the field). The electric potentials across and along the membrane are computed for the case of an applied DC-field. The local amplitudes and phases of the potential under different frequencies are analyzed for the case of a DC + AC-field. We found that the effect of the system of charges alters the electric potential and internal field, which deviate significantly from their traditional linear and constant distributions. Under DC + AC conditions, the strong frequency dependence of the prestin mobile charge has a relatively small effect on the amplitude and phase of the resulting potential. The obtained results can help in a better understanding and experimental verification of the mechanism of prestin performance.
Topics: Animals; Computational Biology; Electric Conductivity; Hair Cells, Auditory, Outer; Mammals; Membrane Potentials; Models, Theoretical
PubMed: 25687712
DOI: 10.1007/s11517-015-1248-0 -
Scientific Reports Sep 2022Electrical aspects of cell function manifest in many ways. The most widely studied is the cell membrane potential, V, but others include the conductance and capacitance...
Electrical aspects of cell function manifest in many ways. The most widely studied is the cell membrane potential, V, but others include the conductance and capacitance of the membrane, the conductance of the enclosed cytoplasm, as well as the charge at the cell surface (an electrical double layer) producing an extracellular electrical potential, the ζ-potential. Empirical relationships have been identified between many of these, but not the mechanisms that link them all. Here we examine relationships between V and the electrical conductivities of both the cytoplasm and extracellular media, using data from a suspensions of red blood cells. We have identified linear relationships between extracellular medium conductivity, cytoplasm conductivity and V. This is in contrast to the standard model of a resting membrane potential which describes a logarithmic relationship between V and the concentration of permeable ions in the extracellular medium. The model here suggests that V is partially electrostatic in origin, arising from a charge imbalance at an inner electrical double-layer, acting across the membrane and double-layer capacitances to produce a voltage. This model describes an origin for coupling between V and ζ, by which cells can alter their electrostatic relationship with their environment, with implications for modulation of membrane ion transport, adhesion of proteins such as antibodies and wider cell-cell interactions.
Topics: Anions; Cations; Cytoplasm; Electric Conductivity; Erythrocytes; Membrane Potentials
PubMed: 36056086
DOI: 10.1038/s41598-022-19316-z -
Frontiers in Neural Circuits 2020loose patch and breakthrough whole-cell recordings are useful tools for investigating the intrinsic and synaptic properties of neurons. However, the correlation among...
loose patch and breakthrough whole-cell recordings are useful tools for investigating the intrinsic and synaptic properties of neurons. However, the correlation among pipette resistance, seal condition, and recording time is not thoroughly clear. Presently, we investigated the recording time of different pipette resistances and seal conditions in loose patch and breakthrough whole-cell recordings. The recording time did not change with pipette resistance for loose patch recording (-loose) and first increased and then decreased as seal resistance for loose patch recording (-loose) increased. For a high probability of a recording time ≥30 min, the low and high cutoff values of -loose were 21.5 and 36 MΩ, respectively. For neurons with -loose values of 21.5-36 MΩ, the action potential (AP) amplitudes changed slightly 30 min after the seal. The recording time increased as seal resistance for whole-cell recording (-tight) increased and the zero-current membrane potential for breakthrough whole-cell recording (MP) decreased. For a high probability of a recording time ≥30 min, the cutoff values of -tight and MP were 2.35 GΩ and -53.5 mV, respectively. The area under the curve (AUC) of the MP receiver operating characteristic (ROC) curve was larger than that of the -tight ROC curve. For neurons with MP values ≤ -53.5 mV, the inhibitory or excitatory postsynaptic current amplitudes did not show significant changes 30 min after the seal. In neurons with -tight values ≥2.35 GΩ, the recording time gradually increased and then decreased as the pipette resistance for whole-cell recording (-tight) increased. For the high probability of a recording time ≥30 min, the low and high cutoff values of -tight were 6.15 and 6.45 MΩ, respectively. Together, we concluded that the optimal -loose range is 21.5-36 MΩ, the optimal -tight range is 6.15-6.45 MΩ, and the optimal -tight and MP values are ≥2.35 GΩ and ≤ -53.5 mV, respectively. Compared with -tight, the MP value can more accurately discriminate recording times ≥30 min and <30 min.
Topics: Acoustic Stimulation; Animals; Auditory Cortex; Excitatory Postsynaptic Potentials; Female; Inhibitory Postsynaptic Potentials; Membrane Potentials; Mice; Mice, Inbred C57BL; Patch-Clamp Techniques
PubMed: 32714153
DOI: 10.3389/fncir.2020.00034