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Patent 4580206: Voltage clamp regulator   (Site not responding. Last check: 2007-10-20) To regulate the increase in voltage in the secondary, diode clamping is accomplished by a common string of zener diodes connected to the output of the secondaries of th transformer circuits and to the emitters of the transistors. To regulate the increase in voltage in the secondary, diode clamping is accomplished by a common string of zener diodes connected to the output of the secondaries of the transformer circuits and to the emitters of the transistors. One method of clamping the voltage is to connect a zener diode across the collector emitter junctions of each of the transistors 20 and 22 to clamp the voltage at an appropriate level. www.freepatentsonline.com /4580206.html   (1731 words)

Patent 5196793: Crankshaft position voltage developing apparatus having a voltage clamp The apparatus includes a negative voltage clamp which clamps the voltage of a junction of the clamp circuit to substantially ground potential during negative half-cycles of the alternating voltage induced in the pick-up coil. The clamp voltages are determined by the base-emitter voltages of Q1 and Q2 and the voltage drops across diodes 68 and 60. Thus, the clamp voltage at terminal VP is related to base-emitter voltage of Q2 added to the voltage drop across diode 68 and the clamp voltage at terminal VPD is related to the base-emitter voltage of Q1 added to the voltage drop across diode 60. www.freepatentsonline.com /5196793.html   (2165 words)

Correction of Conductance Measurements in Non-Space-Clamped Structures: 1. Voltage-Gated K+ Channels -- Schaefer et al. ... The voltage clamp was inserted in the middle of the cable, and consisted of a voltage step from -80 mV to 0 mV. The voltage attenuation in steady state is shown for a simulated voltage clamp to -20 mV in the middle of the cable with an ohmic membrane conductance of 30 pS/µm The voltage attenuation in steady state is shown for a simulated voltage clamp to -20 mV in the middle of the cable. www.biophysj.org /cgi/content/full/84/6/3508   (7919 words)

4. Active Behavior of the Cell Membrane This chapter describes the voltage clamp device, the experiments of Hodgkin and Huxley, the mathematical model into which their data were fitted, and the resulting simulation of a wide variety of recognized electrophysiological phenomena (activation, propagation, etc.). Voltage clamp recordings may be accomplished with the whole cell method for cells as small as red blood cells. Thus a voltage clamp measurement may be performed simply by applying a voltage to the micropipette and measuring the current in the conventional way. butler.cc.tut.fi /~malmivuo/bem/bembook/04/04.htm   (14332 words)

Voltage dependence of macroscopic and unitary currents of gap junction channels formed by mouse connexin50 expressed in ... Voltage dependence of macroscopic and unitary currents of gap junction channels formed by mouse connexin50 expressed in rat neuroblastoma cells -- Srinivas et al. To evaluate the voltage dependence of the junctional conductance, 7-10 s hyperpolarizing or depolarizing pulses were applied every 30 s from the holding potential of 0 mV to various test potentials (between -100 and 100 mV). Differences in voltage sensitivity for other connexins when expressed in oocytes and in mammalian cells has been noted previously, but in all other cases, the voltage sensitivity in mammalian expression systems is steeper than in oocytes. jp.physoc.org /cgi/content/full/517/3/673   (10157 words)

Voltage Clamp   (Site not responding. Last check: 2007-10-20) The basic idea is that the voltage potential across a cell membrane is controled by the experimenter and the current is measured. So, if the voltage level is quickly changed via a step function from one voltage to another, then the capcitance current is circumvented and we are left with a measure of the ionic current. Finally, if the voltage is clamped to the equilibrium potential of a particular ion, then any current change would be due to the flow of other ions. retina.anatomy.upenn.edu /~lance/Physio/voltage_clamp.html   (218 words)

What Does The Voltage Clamp Simulation Allow You To Do The voltage clamp apparatus consists of a Feedback Amplifier, a Voltage Amplifier, and an Ammeter (A). Not surprisingly, the voltage clamp experiment is still being used extensively by researchers in their efforts to understand the function of excitable cells. When you initiate a simulation run, the clamping voltage is not applied until approximately 1 ms after the simulation commences. www.unm.edu /~toolson/435_voltage_clamp_introduction.htm   (1312 words)

Switched single-electrode voltage-clamp amplifiers allow precise measurement of gap junction conductance -- Müller ... Data, the voltage and current of each amplifier, were sampled at a rate of 5 kHz/channel after low-pass filtering at 1 kHz. A: proportional-integral controller was employed, and voltage in nonpulsed cell remained unchanged except for small voltage transients at beginning and end of voltage jump. Limitations of the dual voltage clamp method in assaying conductance and kinetics of gap junction channels. ajpcell.physiology.org /cgi/content/full/276/4/C980   (3575 words)

NASIOC - Torque chip II and voltage clamp? I also have a voltage clamp that is with my lude speed kit. You will have to drive it but first hook a voltage meter to the wire going to the map sensor. If the voltage is too high it will throw the mil light (other things also) if it too low it will run lean. forums.nasioc.com /forums/showthread/t-434360.html   (236 words)

Alembic Instruments. VE-2 Patch Clamp Amplifier   (Site not responding. Last check: 2007-10-20) Voltage Clamp the largest, fastest whole-cell currents under physiologic conditions. In demanding applications, Rs voltage errors of only a few millivolts cause uncontrolled current activation and loss of the voltage clamp. The voltage error is reduced to 5mV (B) but undampened oscillations indicate instability. www.alembicinst.com   (209 words)

Pulse and Trapezoidal Voltage Clamp Applied To Jurkat Cells: A T- Lymphocyte Cell Line - Storming Media From a holding potential of 70 mv, a sequence of depolarizing square voltage pulses ranging from 0 to 130 mv., spaced 10 mv apart and of duration 190ms., was applied to the cell membrane and the resulting currents measured. In addition to square pulses, trapezoidal voltage wave forms were applied to the cell and the evoked currents were measured. Also, it may be possible to interpret the current vs. time records evoked by the trapezoidal voltage wave forms in terms of a variable capacitance. www.stormingmedia.us /29/2924/A292462.html   (381 words)

NASIOC - broken voltage clamp = no prob. the voltage clamp was malfunctioning, making it impossible to drive my car. the bottom line is, with no voltage clamp, my car still runs fine up to 5psi of boost. The voltage is IIRC 4.1V at fuel cut. forums.nasioc.com /forums/showthread/t-203643.html   (405 words)

Whole-Cell Voltage Clamping of Isolated Heart Cells Whole-cell voltage clamp of isolated heart cells has led to an explosion of information about ionic currents in the heart. Once a gigohm seal is formed between the glass and cell membrane (cell-attached mode), capacitance transients are generated by applying 5 mV voltage pulses to the pipette. The whole-cell configuration is subsequently attained by rupturing the patch of membrane within the pipette by either suction (generally applied by mouth or alternatively by a gas-tight syringe) or by “zapping” the membrane. www.usouthal.edu /ishr/help/wholecellclamp   (2194 words)

NMDA-Induced Dendritic Oscillations during a Soma Voltage Clamp of Chick Spinal Neurons -- Moore et al. 19 (19): 8271 ... A whole-cell voltage clamp of the somatic membrane was used to The step voltage command was applied for 0.2-0.6 sec, after which was added 1 sec of a small signal deterministic white noise signal consisting of 400 sequential sine waves with randomized phases. Sernagor E, O'Donovan MJ (1991) Whole-cell patch clamp recordings from rhythmically active motoneurons in the isolated spinal cord of the chick embryo. www.jneurosci.org /cgi/content/full/19/19/8271   (6503 words)

Publications 90: 280-290 [PDF] Hartline, D.K. and Castelfranco, A.M. "Simulations of voltage clamping poorly space-clamped voltage-dependent conductances in a uniform cylindrical neurite" J. Graubard, K. and Hartline, D.K. (1991) "Voltage clamp analysis of intact stomatogastric neurons" Brain Res. Hartline, D.K., Palacio, J.Y., and Gassie, D.V. (1985) "Voltage clamp studies of isolated somata from identified pattern generator neurons in the lobster stomatogastric ganglion." Soc. www.pbrc.hawaii.edu /~danh/publications.html   (1866 words)

INACTIVATION OF DELAYED OUTWARD CURRENT STUDIED BY MEANS OF REPEATED VOLTAGE-CLAMP PULSES At a fixed holding potential the outward current increases with increasing membrane potential or, at a given clamp potential, a reduction of the outward current is observed when increasing holding potential. The deficit in net outward charge transfer, under voltage clamp condition, is related to the inward flow of Ca ions. does not activate the calcium dependent potassium current and with depolarizing clamps from -40 mV, to inactivate the transient outward current, it is possible to measure the voltage dependent component of delayed outward current. users.unimi.it /~monticy/cs068.htm   (248 words)

Differential expression of voltage-sensitive K+ and Ca2+ currents in neurons of the honeybee olfactory pathway -- ... hyperpolarizing voltage pulses to a nonactive region of the tetrodotoxin (TTX) and were elicited by command voltage pulses between -80 mV and +120 mV (increment 10 mV; preceded by a prepulse to -120 mV for 1 s; holding potential -80 mV; see pulse protocol in Fig. Currents were elicited by depolarizing voltage pulses (-90 to +60 mV, increment 10 mV; duration 100 ms; holding potential -80 mV); protocol (inset). jeb.biologists.org /cgi/content/full/206/1/117   (6017 words)

An Intermediate State of the {gamma}-Aminobutyric Acid Transporter GAT1 Revealed by Simultaneous Voltage Clamp and ... Q) was calculated by integrating the transient current induced by a voltage jump from a holding potential of -40 mV to various test potentials, as shown in Fig 5, middle. Comparison of the voltage dependence of the fluorescence relaxations and the charge movements. The voltage was held at -40 mV and stepped to a test potential of -140 mV. www.jgp.org /cgi/content/full/115/4/491   (8099 words)

Patch-Clamp Techniques topic - Unified Search Environment All patch-clamp methods rely on a very high-resistance seal between a micropipette and a membrane; the seal is usually attained by gentle suction. The four most common variants include on-cell patch, inside-out patch, outside-out patch, and whole-cell clamp. Patch-clamp methods are commonly used to voltage clamp, that is control the voltage across the membrane and measure current flow, but current-clamp methods, in which the current is controlled and the voltage is measured, are also used. www.use.hcn.com.au /subject.%60Patch-Clamp%20Techniques%60/home.html   (87 words)

Larry Abbott   (Site not responding. Last check: 2007-10-20) Sharp, A., O'Neil M.B, Abbott, L.F. and Marder, E. (1993) The Dynamic Clamp: Artificial Conductances in Biological Neurons. Passive or active channels can be selected and studied by a standard voltage clamp protocol. Clamping voltages and pulse timing can be set as can ion concentrations on both sides of the patch. wpad.brandeis.edu /~abbott   (4083 words)

Analysis of Voltage Clamp Data   (Site not responding. Last check: 2007-10-20) Current depends on the voltage that is driving it divided by the resistance to the flow of current. The reason for this is that at these voltages conductance doesn't change anymore because all of the channels are open. So, at negative voltages where driving force is greatest, the size of the current becomes more dependent upon the number of open channels. medweb.bham.ac.uk /bmedsci/bms2/neuroscience/Vclamp3.htm   (843 words)

Simulations of ion channels and excitable membranes   (Site not responding. Last check: 2007-10-20) This is a brief Textbook that covers the basics of the initiation and propagation of the nerve impulse using equivalent circuits with reference to ionic conductances. Voltage dependent conductances are explained on the basis of single channel properties. Model of the Shaker K channel voltage sensor pb010.anes.ucla.edu   (72 words)

Whole-cell voltage-clamp recordings in granule cells acutely isolated from hippocampal slices of adult or aged rats.   (Site not responding. Last check: 2007-10-20) Whole-cell voltage-clamp recordings were undertaken in granule cells acutely dissociated by a simple enzymatic procedure from the dentate gyri of hippocampal slices obtained from adult or aged rats. This dissociation procedure also allowed the concomitant isolation of other neuron types from diverse hippocampal subfields for the study of ionic currents through voltage- and neurotransmitter-gated channels. For example, in isolated granule cells of the dentate gyrus both transient and sustained Ca2+ currents could be observed in the presence of extracellular tetrodotoxin (TTX) and intracellular Cs+. www.arclab.org /medlineupdates/abstract_2538782.html   (164 words)

A 5-HT7 Receptor-Mediated Depolarization in the Anterodorsal Thalamus. II. Involvement of the ... Serotonin shifts the voltage dependence of this current in the depolarizing direction by approximately 8 mV. voltage dependence of activation is evident in the raw traces Slices were incubated in either staurosporine or H-8 for at least 1 h to ensure penetration of the blocker to the cell. www.jpet.org /cgi/content/full/297/1/403   (4297 words)

STG References Graubard K, Hartline DK (1991) Voltage clamp analysis of intact stomatogastric neurons. Hartline DK, Castelfranco AM (2003) Simulations of voltage clamping poorly space-clamped voltage-dependent conductances in a uniform cylindrical neurite. Tazaki K, Cooke IM (1986) Currents under voltage clamp of burst-forming neurons of the cardiac ganglion of the lobster (Homarus americanus). stg.rutgers.edu /stgrefs/index.html   (13519 words)

The Pattern of Disulfide Linkages in the Extracellular Loop Regions of Connexin 32 Suggests a Model for the Docking ... responses to incremental hyper- and depolarizing voltage pulses. on the voltage gating characteristics of gap junctions. of the voltage responses of Cx46 in the hemichannel and the intact www.jcb.org /cgi/content/full/140/5/1187   (7018 words)

A Novel H+ Conductance in Eosinophils: Unique Characteristics and Absence in Chronic Granulomatous Disease -- ... The membrane potential of eosinophils, determined as the zero current holding potential, was measured in current clamp mode after the formation of the whole cell configuration (arrowhead). Currents measured 500 ms after the beginning of a 5-s-long voltage pulse were subtracted from the current measured at the end of the pulse. The holding voltage was –60 mV (pH 6.1), -40 mV (pH 7.1), and –20 mV (pH 7.6 and 8.1), and bath pH was 7.1 in all conditions. www.jem.org /cgi/content/full/190/2/183   (6320 words)

Effects of Irbesartan on Cloned Potassium Channels Involved in Human Cardiac Repolarization -- Moreno et al. 304 (2): ... Effects of irbesartan on the voltage dependence of Kv4.3 channel inactivation. A, Kv4.3 current traces in the absence and in the presence of 1 µM irbesartan obtained when applying pulses to potentials ranging from -90 to + 50 mV followed by a 250-ms pulse to +40 mV. to determine the voltage dependence of the blockade. jpet.aspetjournals.org /cgi/content/full/304/2/862   (5712 words)

Active Dendritic Membrane Properties of Xenopus Larval Spinal Neurons Analyzed With a Whole Cell Soma Voltage Clamp -- ... Active Dendritic Membrane Properties of Xenopus Larval Spinal Neurons Analyzed With a Whole Cell Soma Voltage Clamp. Voltage- and current-clamp measurements of inwardly directed currents were made from the somatic regions of Xenopus laevis voltage clamp, but not current clamp, were able to indicate a jn.physiology.org /cgi/content/abstract/83/3/1381   (369 words)

Losartan Improves Recovery of Contraction and Inhibits Transient Inward Current in a Cellular Model of Cardiac Ischemia ... After 20 min of reperfusion, untreated cells showed a significant decrease in contractions that was almost completely prevented in losartan-treated cells. Losartan did not alter the voltage dependence of contraction during ischemia or reperfusion. Neither of the AII treatment groups exhibited a shift in the voltage dependence of contraction during ischemia or reperfusion. www.jpet.org /cgi/content/full/295/2/697   (4060 words)

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