The Electrical Properties of Cells
Richard C. Niemtzow in Transmembrane Potentials and Characteristics of Immune and Tumor Cell, 2020
In point of fact, a membrane is not actually necessary in order to observe a potential between two solutions of differing ion concentrations in contact with one another. If a solution of 0.01 M NaCl is carefully layered on top of a solution of 0.1 M NaCl, a potential can be recorded between the two solutions. The potential arises because of the difference in mobility of the Na+ ion and the Cl- ion. Since the rate of movement of Cl- in solution is greater than that of Na+, anions will move across the solution boundary from higher concentration to lower somewhat faster than cations, thus producing a negative potential in the solution of lower concentration. The formula which describes the magnitude of this liquid junction potential is
Superparamagnetic iron oxide nanoparticles (SPIONs) modulate hERG ion channel activity
Published in Nanotoxicology, 2019
Roberta Gualdani, Andrea Guerrini, Elvira Fantechi, Francesco Tadini-Buoninsegni, Maria Rosa Moncelli, Claudio Sangregorio
Electrophysiological recordings were performed in whole-cell patch-clamp configuration. The extracellular solution had the following composition: 140 mM NaCl, 5 mM KCl, 1 mM MgCl2, 2 mM CaCl2, 10 mM Glucose, 10 mM HEPES, pH 7.4 with NaOH. The pipette contained: 130 mM KCl, 10 mM EGTA, 1 mM MgCl2, 2 mM Mg-ATP, 10 mM HEPES, pH 7.20 with KOH. Solutions were applied to the cell via a gravity-fed perfusion system coupled with a Fast Exchange Open Diamond Bath chamber (VC-6 Six Channel Valve Controller, Warner Instruments, Hamden, CT), in order to allow very fast solution exchange. Currents were sampled at 20 kHz and digitally filtered at 2.9 kHz. The currents were not corrected for the liquid junction potential. Series resistance was electronically compensated. Patch-clamp recordings of cell cultures were carried out at room temperature 48 h after transfection. Patch-clamp electrodes were pulled from Sutter capillary glass (Novato, San Francisco, CA, USA) on a Flaming/Brown type puller (Sutter P-87), and fire polished to 3–4 MΩ resistance, using a microforge (Narishige, Tokyo, Japan). For recordings a Multiclamp 700B amplifier (Molecular Devices Inc., Sunnyvale, CA, USA) and Digidata 1440 data acquisition board (Molecular Devices Inc., Sunnydale, CA, USA) with pCLAMP 10 software (Molecular Devices Inc., Sunnyvale, CA, USA) were used. Data analysis was performed using Origin version 8.0 (OriginLab Corporation, Northampton, MA, USA).
Calcium-dependent, non-apoptotic, large plasma membrane bleb formation in physiologically stimulated mast cells and basophils
Published in Journal of Extracellular Vesicles, 2019
C. Jansen, C Tobita, E. U. Umemoto, J. Starkus, N. M. Rysavy, L. M. N. Shimoda, C. Sung, A.J. Stokes, H Turner
Patch-clamp experiments were performed in the tight-seal whole-cell configuration at 21–25°C. Current and membrane capacitance recordings were captured with EPC-10 amplifier (HEKA, Lambrecht, Germany). RBL-2H3 cells were grown on glass coverslips and bathed in the external Ringer solution. External Ringer solution (in mM): 140 NaCl, 2.8 KCl, 1 CaCl2, 2 MgCl2 and 10 NaHEPES. Internal solution in the pipette contained the following (in mM): 120 Cs-glutamate, 8 NaCl, 1 MgCl2, 8.5 CaCl2, 10 Cs-BAPTA and 10 CsHEPES, which resulted in 1.2 µM buffered internal calcium. The internal solution-filled patch pipettes had a resistance between 2 and 4 MΩ. Following break-in, voltage ramps of 50 ms duration from −100 mV – +100 mV were delivered to the cells with a holding potential of 0 mV at a rate of 0.5 Hz over the period of the recording. All voltages were corrected for a liquid junction potential of 10 mV. Currents were filtered at 2.9 kHz and digitized at 100 µs intervals. Capacitance measurements specifically employed the OnCell_Cm protocol in PATCHMASTER on the HEKA EPC-10 amplifier.
A major interspecies difference in the ionic selectivity of megakaryocyte Ca2+-activated channels sensitive to the TMEM16F inhibitor CaCCinh-A01
Published in Platelets, 2019
Kirk A. Taylor, Martyn P. Mahaut-Smith
Electrophysiology: Whole-cell patch clamp recordings were conducted as described previously with ≥70% series resistance compensation and apriori liquid junction potential correction [23]. Bath solutions contained 150mM NaCl, 1mM CaCl2, 1mM MgCl2, 10mM glucose, 10mM HEPES (pH 7.35; NaOH). Where indicated, [Cl−]o and/or [Na+]o were reduced by equimolar substitution with gluconate− or NMDG+, respectively. Internal solutions contained 150mM NaCl, 1mM MgCl2, 10mM glucose, 10mM HEPES, 50µM Na2-GTP, 1mM EGTA (pH 7.2; NaOH). [Ca2+]i was set at ≈5nM (1mM EGTA, no added Ca2+) or 100µM (by addition of CaCl2), calculated using Maxchelator (http://web.stanford.edu/~cpatton/webmaxcS.htm). The effect of CaCCinh-A01 (A01; Merck, Watford, UK) was compared with vehicle (DMSO) control. Statistical analysis was by two-way ANOVA (Prism7, GraphPad Software Inc., CA, USA).
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