scholarly journals High-speed dynamic-clamp interface

2015 ◽  
Vol 113 (7) ◽  
pp. 2713-2720 ◽  
Author(s):  
Yang Yang ◽  
Timothy Adowski ◽  
Bina Ramamurthy ◽  
Andreas Neef ◽  
Matthew A. Xu-Friedman
Keyword(s):  
User Interface ◽  
Sodium Channels ◽  
High Speed ◽  
Markov Models ◽  
Dynamic Clamp ◽  
Voltage Sensitivity ◽  
Voltage Gated ◽  
High Speeds ◽  
Voltage Dependent ◽  
Testing Mode

The dynamic-clamp technique is highly useful for mimicking synaptic or voltage-gated conductances. However, its use remains rare in part because there are few systems, and they can be expensive and difficult for less-experienced programmers to implement. Furthermore, some conductances (such as sodium channels) can be quite rapid or may have complex voltage sensitivity, so high speeds are necessary. To address these issues, we have developed a new interface that uses a common personal computer platform with National Instruments data acquisition and WaveMetrics IGOR to provide a simple user interface. This dynamic clamp implements leak and linear synaptic conductances as well as a voltage-dependent synaptic conductance and kinetic channel conductances based on Hodgkin-Huxley or Markov models. The speed of the system can be assayed using a testing mode, and currently speeds of >100 kHz (10 μs per cycle) are achievable with short latency and little jitter.

Two Types of Voltage-Gated K+ Currents in Dissociated Heart Ventricular Muscle Cells of the Snail Lymnaea stagnalis

1999 ◽  
Vol 82 (5) ◽  
pp. 2415-2427 ◽  
Author(s):  
M. S. Yeoman ◽  
P. R. Benjamin
Keyword(s):  
Voltage Clamp ◽  
Action Potentials ◽  
Muscle Cells ◽  
Delayed Rectifier ◽  
Voltage Sensitivity ◽  
Ventricular Muscle ◽  
Current Time ◽  
Voltage Gated ◽  
Time To Peak ◽  
Voltage Dependent

We have used a combination of current-clamp and voltage-clamp techniques to characterize the electrophysiological properties of enzymatically dissociated Lymnaea heart ventricle cells. Dissociated ventricular muscle cells had average resting membrane potentials of −55 ± 5 mV. When hyperpolarized to potentials between −70 and −63 mV, ventricle cells were capable of firing repetitive action potentials (8.5 ± 1.2 spikes/min) that failed to overshoot 0 mV. The action potentials were either simple spikes or more complex spike/plateau events. The latter were always accompanied by strong contractions of the muscle cell. The waveform of the action potentials were shown to be dependent on the presence of extracellular Ca2+ and K+ ions. With the use of the single-electrode voltage-clamp technique, two types of voltage-gated K+ currents were identified that could be separated by differences in their voltage sensitivity and time-dependent kinetics. The first current activated between −50 and −40 mV. It was relatively fast to activate (time-to-peak; 13.7 ± 0.7 ms at +40 mV) and inactivated by 53.3 ± 4.9% during a maintained 200-ms depolarization. It was fully available for activation below −80 mV and was completely inactivated by holding potentials more positive than −40 mV. It was completely blocked by 5 mM 4-aminopyridine (4-AP) and by concentrations of tetraethylammonium chloride (TEA) >10 mM. These properties characterize this current as a member of the A-type family of voltage-dependent K+ currents. The second voltage-gated K+ current activated at more depolarized potentials (−30 to −20 mV). It activated slower than the A-type current (time-to-peak; 74.1 ± 3.9 ms at +40 mV) and showed little inactivation (6.2 ± 2.1%) during a maintained 200-ms depolarization. The current was fully available for activation below −80 mV with a proportion of the current still available for activation at potentials as positive as 0 mV. The current was completely blocked by 1–3 mM TEA. These properties characterize this current as a member of the delayed rectifier family of voltage-dependent K+ currents. The slow activation rates and relatively depolarized activation thresholds of the two K+ currents are suggestive that their main role is to contribute to the repolarization phase of the action potential.

scholarly journals An unconventional conductance is required for pacemaking of nigral dopamine neurons

2020 ◽  
Author(s):  
Kevin Jehasse ◽  
Laurent Massotte ◽  
Sebastian Hartmann ◽  
Romain Vitello ◽  
Sofian Ringlet ◽  
...  
Keyword(s):  
Substantia Nigra ◽  
Sodium Channels ◽  
Dopamine Neurons ◽  
Substantia Nigra Pars Compacta ◽  
Voltage Gated ◽  
Molecular Identity ◽  
Voltage Gated Sodium Channels ◽  
Voltage Dependent ◽  
Ionic Mechanisms ◽  
Voltage Gated Channels

ABSTRACTAlthough several ionic mechanisms are known to control rate and regularity of the pacemaker in dopamine (DA) neurons from the substantia nigra pars compacta (SNc), a conductance essential for pacing has yet to be defined. Here we provide pharmacological evidence that pacemaking of SNc DA neurons is enabled by an unconventional conductance. We found that 1-(2,4-xylyl)guanidine (XG), an established blocker of gating pore currents in mutant voltage gated sodium channels, selectively stops pacemaking of DA SNc neurons and is without effect on the main pore of their voltage-gated channels. We isolated a voltage-dependent, non-inactivating XG-sensitive current of 20-25 pA which operates in the relevant subthreshold range and is carried by both Na+ and Cl- ions. While the molecular identity of this conductance remains to be determined, we show that this XG-sensitive current is crucial to sustain pacemaking in these neurons.

scholarly journals SCN5A mutation G615E results in NaV1.5 voltage-gated sodium channels with normal voltage-dependent function yet loss of mechanosensitivity

Channels ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 287-298 ◽  
Author(s):  
Peter R. Strege ◽  
Arnaldo Mercado-Perez ◽  
Amelia Mazzone ◽  
Yuri A. Saito ◽  
Cheryl E. Bernard ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Voltage Gated ◽  
Dependent Function ◽  
Voltage Gated Sodium Channels ◽  
Voltage Dependent ◽  
Scn5a Mutation

Fast and Slow Activation Kinetics of Voltage-Gated Sodium Channels in Molluscan Neurons

1997 ◽  
Vol 77 (5) ◽  
pp. 2373-2384 ◽  
Author(s):  
William F. Gilly ◽  
Rhanor Gillette ◽  
Matthew McFarlane
Keyword(s):  
Sodium Channels ◽  
Voltage Dependence ◽  
Na Channel ◽  
Molluscan Neurons ◽  
Na Channels ◽  
Activation Kinetics ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Voltage Dependent ◽  
Kinetics Of

Gilly, William F., Rhanor Gillette, and Matthew McFarlane. Fast and slow activation kinetics of voltage-gated sodium channels in molluscan neurons. J. Neurophysiol. 77: 2373–2384, 1997. Whole cell patch-clamp recordings of Na current ( I Na) were made under identical experimental conditions from isolated neurons from cephalopod ( Loligo, Octopus) and gastropod ( Aplysia, Pleurobranchaea, Doriopsilla) species to compare properties of activation gating. Voltage dependence of peak Na conductance ( g Na) is very similar in all cases, but activation kinetics in the gastropod neurons studied are markedly slower. Kinetic differences are very pronounced only over the voltage range spanned by the g Na-voltage relation. At positive and negative extremes of voltage, activation and deactivation kinetics of I Na are practically indistinguishable in all species studied. Voltage-dependent rate constants underlying activation of the slow type of Na channel found in gastropods thus appear to be much more voltage dependent than are the equivalent rates in the universally fast type of channel that predominates in cephalopods. Voltage dependence of inactivation kinetics shows a similar pattern and is representative of activation kinetics for the two types of Na channels. Neurons with fast Na channels can thus make much more rapid adjustments in the number of open Na channels at physiologically relevant voltages than would be possible with only slow Na channels. This capability appears to be an adaptation that is highly evolved in cephalopods, which are well known for their high-speed swimming behaviors. Similarities in slow and fast Na channel subtypes in molluscan and mammalian neurons are discussed.

scholarly journals Mapping of voltage sensor positions in resting and inactivated mammalian sodium channels by LRET

2017 ◽  
Vol 114 (10) ◽  
pp. E1857-E1865 ◽  
Author(s):  
Tomoya Kubota ◽  
Thomas Durek ◽  
Bobo Dang ◽  
Rocio K. Finol-Urdaneta ◽  
David J. Craik ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Structural Changes ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Voltage Sensor ◽  
Structural Basis ◽  
Excitable Cells ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Voltage Dependent

Voltage-gated sodium channels (Navs) play crucial roles in excitable cells. Although vertebrate Nav function has been extensively studied, the detailed structural basis for voltage-dependent gating mechanisms remain obscure. We have assessed the structural changes of the Nav voltage sensor domain using lanthanide-based resonance energy transfer (LRET) between the rat skeletal muscle voltage-gated sodium channel (Nav1.4) and fluorescently labeled Nav1.4-targeting toxins. We generated donor constructs with genetically encoded lanthanide-binding tags (LBTs) inserted at the extracellular end of the S4 segment of each domain (with a single LBT per construct). Three different Bodipy-labeled, Nav1.4-targeting toxins were synthesized as acceptors: β-scorpion toxin (Ts1)-Bodipy, KIIIA-Bodipy, and GIIIA-Bodipy analogs. Functional Nav-LBT channels expressed inXenopusoocytes were voltage-clamped, and distinct LRET signals were obtained in the resting and slow inactivated states. Intramolecular distances computed from the LRET signals define a geometrical map of Nav1.4 with the bound toxins, and reveal voltage-dependent structural changes related to channel gating.

A Statistical Study of Process Variables to Optimize a High Speed Curtain Coater: Part I

TAPPI Journal ◽  
2009 ◽  
Vol 8 (1) ◽  
pp. 20-26 ◽  
Author(s):  
PEEYUSH TRIPATHI ◽  
MARGARET JOYCE ◽  
PAUL D. FLEMING ◽  
MASAHIRO SUGIHARA
Keyword(s):  
Boundary Layer ◽  
Experimental Design ◽  
High Speed ◽  
Statistical Study ◽  
Process Variables ◽  
High Speeds ◽  
The Stability ◽  
Air Removal ◽  
Removal System

Using an experimental design approach, researchers altered process parameters and material prop-erties to stabilize the curtain of a pilot curtain coater at high speeds. Part I of this paper identifies the four significant variables that influence curtain stability. The boundary layer air removal system was critical to the stability of the curtain and base sheet roughness was found to be very important. A shear thinning coating rheology and higher curtain heights improved the curtain stability at high speeds. The sizing of the base sheet affected coverage and cur-tain stability because of its effect on base sheet wettability. The role of surfactant was inconclusive. Part II of this paper will report on further optimization of curtain stability with these four variables using a D-optimal partial-facto-rial design.

RED CUT COBALT

Alloy Digest ◽  
1980 ◽  
Vol 29 (8) ◽  
Keyword(s):  
Fracture Toughness ◽  
Cast Iron ◽  
High Speed ◽  
Elevated Temperatures ◽  
High Speed Steel ◽  
Heat Treating ◽  
High Speeds ◽  
Red Hardness ◽  
Nonferrous Alloys ◽  
Cutting Point

Abstract RED CUT COBALT steel is made by adding 5% cobalt to the conventional 18% tungsten -4% chromium-1% vanadium high-speed steel. Cobalt increases hot or red hardness and thus enables the tool to maintain a higher hardness at elevated temperatures. This steel is best adapted for hogging cuts or where the temperature of the cutting point of the tool in increased greatly. It is well adapted for tools to be used for reaming cast-iron engine cylinders, turning alloy steel or cast iron and cutting nonferrous alloys at high speeds. This datasheet provides information on composition, physical properties, and hardness as well as fracture toughness. It also includes information on forming, heat treating, and machining. Filing Code: TS-367. Producer or source: Teledyne Vasco.

CPM REX 25

Alloy Digest ◽  
1980 ◽  
Vol 29 (7) ◽  
Keyword(s):  
Heat Treatment ◽  
High Speed ◽  
High Speed Steel ◽  
High Hardness ◽  
Heat Treating ◽  
High Speeds ◽  
Aisi Type ◽  
Tool Performance ◽  
End Mills ◽  
Machining Operations

Abstract CPM REX 25 is a super high-speed steel made without cobalt. It is comparable to AISI Type T15 cobalt-containing high-speed steel in response to heat treatment, properties, and tool performance. CPM REX 25 is recommended for machining operations requiring heavy cuts, high speeds and feeds, and difficult-to-machine materials of high hardness and abrasion resistance. Typical applications are boring tools, drills, gear cutters, punches, form tools, end mills and broaches. This datasheet provides information on composition, physical properties, hardness, and elasticity as well as fracture toughness. It also includes information on forming, heat treating, machining, and surface treatment. Filing Code: TS-365. Producer or source: Crucible Materials Corporation.

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