scholarly journals A new approach to the determination of tubular membrane capacitance: passive membrane electrical properties under reduced electrical conductivity of the extracellular solution

2021 ◽  
Author(s):  
Jiří Šimurda ◽  
Milena Šimurdová ◽  
Olga Švecová ◽  
Markéta Bébarová
Keyword(s):  
Time Course ◽  
Sucrose Solution ◽  
Osmotic Shock ◽  
Surface Membrane ◽  
Extracellular Medium ◽  
Electrical Equivalent Circuit ◽  
Capacitive Current ◽  
Tubular Membrane ◽  
Tubular System

The tubular system of cardiomyocytes plays a key role in excitation-contraction coupling. To determine the area of the tubular membrane in relation to the area of the surface membrane, indirect measurements through the determination of membrane capacitances by electrophysiological measurements are currently used in addition to microscopic methods. Unlike existing electrophysiological methods based on an irreversible procedure (osmotic shock), the proposed approach uses a reversible short-term intermittent increase in the electrical resistance of the extracellular medium. The resulting increase in the lumen resistance of the tubular system makes it possible to determine separately capacitances of the tubular and surface membranes from altered capacitive current responses to subthreshold voltage-clamped rectangular pulses. Based on the analysis of the time course of capacitive current, computational relations were derived which allow to quantify elements of the electrical equivalent circuit of the measured cardiomyocyte including both capacitances. The exposition to isotonic low-conductivity sucrose solution is reversible which is the main advantage of the proposed approach allowing repetitive measurements on the same cell under control and sucrose solutions. In addition, it might be possible to identify changes in both surface and tubular membrane capacitances caused by various interventions. Preliminary experiments in rat ventricular cardiomyocytes (n = 10) resulted in values of the surface and tubular capacitances 72.3 ± 16.4 and 42.1 ± 14.7 pF, respectively, implying the fraction of tubular capacitance/area of 0.36 ± 0.08. We conclude that the newly proposed method provides results comparable to those reported in literature and, in contrast to the currently used methods, enables repetitive evaluation of parameters describing the surface and tubular membranes. It may be used to study alterations of the tubular system resulting from various interventions including associated cardiac pathologies.

scholarly journals Radial propagation of muscle action potential along the tubular system examined by potential-sensitive dyes.

1980 ◽  
Vol 76 (6) ◽  
pp. 751-762 ◽  
Author(s):  
S Nakajima ◽  
A Gilai
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Time Course ◽  
Surface Membrane ◽  
Simultaneous Recording ◽  
Conduction Delay ◽  
Muscle Action Potential ◽  
Tubular System ◽  
Intracellular Action ◽  
T System

Isolated single (Xenopus) muscle fibers were stained with a non-permeant potential-probing dye, merocyanine rhodanine (WW375) or merocyanine oxazolone (NK2367). When the fiber was massively stimulated, an absorption change (wave a), which seemed to reflect the action potential, occurred. Simultaneous recording of optical changes and intracellular action potentials revealed that the time-course of wave a was slower than the action potential: the peak of wave a was attained at 1 ms, and the peak of action potential was reached at 0.5 ms after the stimulation. This difference suggests that wave a represents the potential changes of the whole tubular membrane and the surface membrane, whereas the action potential represents a surface potential change. This idea was substantiated by recording absorption signals preferentially from the surface membrane by recording the absorption changes at the edge of the fiber. Wave a obtained by this method was as quick as the intracellular action potential. The value of radial conduction velocity of action potential along the T system, calculated by comparing the action potential with wave a, was 6.4 cm/s at 24.5 degrees C, in fair agreement with González-Serratos (1971. J. Physiol. [Lond.]. 212:777-799). The shape of wave a suggests the existence of an access delay (a conduction delay at the orifice of the T system) of 130 microseconds.

Short-term volume and turgor regulation in yeast

2008 ◽  
Vol 45 ◽  
pp. 147-160 ◽  
Author(s):  
Jörg Schaber ◽  
Edda Klipp
Keyword(s):  
Dynamic Model ◽  
Volume Change ◽  
Volume Regulation ◽  
Time Course ◽  
Osmotic Shock ◽  
Intracellular Concentration ◽  
Short Term ◽  
Hydrodynamic Property ◽  
Turgor Regulation ◽  
Thermodynamic Framework

Volume is a highly regulated property of cells, because it critically affects intracellular concentration. In the present chapter, we focus on the short-term volume regulation in yeast as a consequence of a shift in extracellular osmotic conditions. We review a basic thermodynamic framework to model volume and solute flows. In addition, we try to select a model for turgor, which is an important hydrodynamic property, especially in walled cells. Finally, we demonstrate the validity of the presented approach by fitting the dynamic model to a time course of volume change upon osmotic shock in yeast.

Time course of sodium-induced Na(+)-K(+)-ATPase recruitment in rabbit cortical collecting tubule

1992 ◽  
Vol 263 (1) ◽  
pp. C61-C68 ◽  
Author(s):  
N. Coutry ◽  
M. Blot-Chabaud ◽  
P. Mateo ◽  
J. P. Bonvalet ◽  
N. Farman
Keyword(s):  
Time Course ◽  
Sucrose Solution ◽  
Sodium Concentration ◽  
Rabbit Kidney ◽  
Ouabain Binding ◽  
Kinase C ◽  
Short Period ◽  
Intracellular Sodium Concentration ◽  
Collecting Tubule ◽  
Collecting Tubules

In cortical collecting tubules (CCD) of aldosterone-repleted rabbit kidney, an increase in intracellular sodium concentration (Nai) induces the recruitment and/or activation of latent Na(+)-K(+)-ATPase pumps (Blot-Chabaud et al., J. Biol. Chem. 265: 11676-11681, 1990). The present study was addressed to determine the time course of this Nai-dependent pump recruitment and to examine some of the factors possibly involved in this phenomenon. CCD from adrenalectomized rabbits complemented with aldosterone and dexamethasone were incubated at 4 degrees C either in a K(+)-free saline solution (Na(+)-loaded CCD) or in a sucrose solution (control CCD) and then rewarmed for various time periods to allow pump recruitment to occur. The number of pumps in the membrane was determined by specific [3H]ouabain binding; Nai was measured using 22Na. A rise in Nai induced a threefold increase in the number of basolateral pumps, which was fully achieved within 1-2 min. This pump recruitment was reversible within 15 min after restoration of low Nai. It was unaffected by inhibitors of cytoskeleton and Ca2+ ionophore A 23187. The blocker of the Na(+)-H+ antiporter, amiloride, did not prevent it. The protein kinase C activator, phorbol 12-myristate 13-acetate, did not induce it in the absence of Na+. We conclude that Nai is a major determinant of pump recruitment and/or activation, which occurs over a very short period of time. It may constitute a rapid adaptative response to an increase in the cell Na+ load.

Exosite-dependent regulation of factor VIIIa by activated protein C

Blood ◽  
2003 ◽  
Vol 101 (12) ◽  
pp. 4802-4807 ◽  
Author(s):  
Chandrashekhara Manithody ◽  
Philip J. Fay ◽  
Alireza R. Rezaie
Keyword(s):  
Protein C ◽  
Time Course ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Limited Proteolysis ◽  
Activated Protein C ◽  
Coagulation Cascade ◽  
Factor Va ◽  
Factor Viiia

AbstractActivated protein C (APC) is a natural anticoagulant serine protease in plasma that down-regulates the coagulation cascade by degrading cofactors Va and VIIIa by limited proteolysis. Recent results have indicated that basic residues of 2 surface loops known as the 39-loop (Lys37-Lys39) and the Ca2+-binding 70-80–loop (Arg74 and Arg75) are critical for the anticoagulant function of APC. Kinetics of factor Va degradation by APC mutants in purified systems have demonstrated that basic residues of these loops are involved in determination of the cleavage specificity of the Arg506 scissile bond on the A2 domain of factor Va. In this study, we characterized the properties of the same exosite mutants of APC with respect to their ability to interact with factor VIIIa. Time course of the factor VIIIa degradation by APC mutants suggested that the same basic residues of APC are also critical for recognition and degradation of factor VIIIa. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) of the factor VIIIa cleavage reactions revealed that these residues are involved in determination of the specificity of both A1 and A2 subunits in factor VIIIa, thus facilitating the cleavages of both Arg336 and Arg562 scissile bonds in the cofactor.

scholarly journals Electrical Equivalent Circuit of Multi-Tips Pulsed Corona Discharge Reactor

2021 ◽  
Vol 348 ◽  
pp. 01014
Author(s):  
Karim Saber ◽  
Alyen Abahazem ◽  
Nofel Merbahi ◽  
Mohamed Yousfi
Keyword(s):  
Corona Discharge ◽  
Electrical Circuit ◽  
Electrical Model ◽  
Electrical Equivalent Circuit ◽  
Rls Algorithm ◽  
Estimated Parameters ◽  
Maximum Value ◽  
Pulsed Corona ◽  
Discharge Behavior

In this work, an electrical model equivalent to the corona discharge reactor has been proposed in a multitips plan configuration, in dry air at atmospheric pressure. The electrical parameters evolution of the circuit are obtained by using the identification method which is based on the least squares recursive (RLS) algorithm, the estimated parameters allow us to describe the corona discharge behavior inside the reactor. The RLS method used during the determination of capacitance and resistance is validated by the comparison between the measured and the calculated currents, the significant forms of capacitance and resistance confirm the validity of the proposed electrical model. The estimated parameters of the electrical circuit allowed us to determine the discharge power, the power delivered to the reactor and thus the energy efficiency during the discharge, this efficiency increases during the propagation of streamers towards the plane, it reaches a maximum value which is equal to 50% in the case of the fourtips- plane configuration. The energy stored in the reactor is also calculated using the electrical circuit, it increases to a maximum value of 2.6 pJ, which is a very low value compared to the energy delivered to the reactor. This work allows us to control the discharge and lost energy during the corona discharge in the case of multi-tips-plane configuration.

scholarly journals In Vitro Evaluation of the Sensitivity of a Hyaluronic Acid PEG Cross-Linked to Bovine Testes Hyaluronidase

2018 ◽  
Vol 6 (1) ◽  
pp. 20-24 ◽  
Author(s):  
Nicola Zerbinati ◽  
Torello Lotti ◽  
Damiano Monticelli ◽  
Virginia Martina ◽  
Giovanna Cipolla ◽  
...  
Keyword(s):  
Hyaluronic Acid ◽  
Soft Tissue ◽  
Chemical Reaction ◽  
Time Course ◽  
Soft Tissue Augmentation ◽  
Facial Soft Tissue ◽  
Microplate Reader ◽  
Kinetics Of

Neauvia Intense is biocompatible, injectable hyaluronic acid (HA) filler PEG cross-linked for facial soft-tissue augmentation that provides volume to tissues. The aim of the present study is to evaluate the sensitivity of Neauvia Intense in hyaluronidase from bovine testes in a time-course analysis. The test is based on the colourimetric determination of the N-acetyl – D - glucosamine (NAG) released by the hyaluronidase in standardised conditions. The in vitro conditions involve the treatment of Neauvia Intense with a known concentration of the enzyme (6080U/ml). The NAG content was determined at different times to assess the kinetics of the degradation (1h, 3h, 6h, 24h, 48h, 72h, 120h, and 168h); the Ehrlich’s reagent was used for the colourimetric quantification, by the method described by Reissing and colleagues. The intensity of the violet colour developed after the chemical reaction was proportional to the NAG present in each sample. A microplate reader at 585 nm read the absorbance. The amount of NAG released by the product was proportional to the time of incubation with bovine hyaluronidase, reaching a plateau after 168 hours.

Reactive Diffusion at the Cylindrical Dissolving of Copper in the Solder Melt

2011 ◽  
Vol 312-315 ◽  
pp. 387-392 ◽  
Author(s):  
Jaromír Drápala ◽  
Alena Struhařová ◽  
Daniel Petlák ◽  
Vlastimil Vodárek ◽  
Petr Kubíček
Keyword(s):  
Time Course ◽  
Solid Phase ◽  
Accurate Determination ◽  
Theoretical Description ◽  
Reactive Diffusion ◽  
Interface Boundary ◽  
Boundary Movement ◽  
Long Time ◽  
Melt Cooling

Problems of reactive diffusion at the solid phase and melt contact were studied theoretically and experimentally. The main intention was to calculate the time course of the solid phase dissolving in the case of cylindrical dissolving. These calculations were carried out on the assumption for the rate constant of dissolving K = const. In our work we give heed especially to the dominating process, which is the solid metal A dissolved in the melt B. During the dissolving the melt B saturates with the metal A and the process is influenced by convections which are characteristic for the given experimental configuration. A theoretical description of the kinetics of the solid phase dissolving in the melt will be presented for the case of cylindrical dissolving. The aim is to derive a relation for the interface boundary movement c(t) in dependence on time and a time course of growth of the element A concentration in the melt B. There are problems with accurate determination of the interface boundary movement after certain heating times of specimens, when it is observed experimentally, since intermetallic phases create in the original A metal at both the diffusion and cooling and some phases segregate at the solidifying melt cooling. The main intention was an experimental study of the copper dissolving in the tin melt. Experiments aimed to the determination of the Cu wires (diameters from 0.5 to 3.5 mm) dissolution in the solder melt were carried out at various selected temperatures and times. Rapid growth of phases in the metal A and determination of the thickness of layers with these phases pose considerable time demands to X-ray micro-analyses (WDX, EDX) of specimens after their long-time heating.

scholarly journals The Capacitance of Skeletal Muscle Fibers in Solutions of Low Ionic Strength

1972 ◽  
Vol 59 (3) ◽  
pp. 347-359 ◽  
Author(s):  
P. C. Vaughan ◽  
J. N. Howell ◽  
R. S. Eisenberg
Keyword(s):  
Skeletal Muscle ◽  
Ionic Strength ◽  
Surface Membrane ◽  
Muscle Fibers ◽  
External Solution ◽  
Rectangular Pulse ◽  
Bathing Solution ◽  
Skeletal Muscle Fibers ◽  
Tubular System ◽  
Low Ionic Strength

The capacitance of skeletal muscle fibers was measured by recording with one microelectrode the voltage produced by a rectangular pulse of current applied with another microelectrode. The ionic strength of the bathing solution was varied by isosmotic replacement of NaCl with sucrose, the [K] [Cl] product being held constant. The capacitance decreased with decreasing ionic strength, reaching a value of some 2 µF/cm2 in solutions of 30 mM ionic strength, and not decreasing further in solutions of 15 mM ionic strength. The capacitance of glycerol-treated fibers did not change with ionic strength and was also some 2 µF/cm2. It seems likely that lowering the ionic strength reduces the capacitance of the tubular system (defined as the charge stored in the tubular system), and that the 2 µF/cm2 which is insensitive to ionic strength is associated with the surface membrane. The tubular system is open to the external solution in low ionic strength solutions since peroxidase is able to diffuse into the lumen of the tubules. Twitches and action potentials were also recorded from fibers in low ionic strength solutions, even though the capacitance of the tubular system was very small in these solutions. This finding can be explained if there is an action potential—like mechanism in the tubular membrane.

Sign in / Sign up

Export Citation Format

Share Document