Journal article · January 1, 2020
Following is a continuation of the listing of papers presented: Automatic Calibration of On-Line Respiratory Measurements. By J. O. Beaumont and W. A. Radke. System for Storage and Retrieval of Textual and Numeric Data Collected During Patient Monitoring. ...
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Journal article · January 1, 2017
Following is a continuation of the listing of papers presented: Automatic Calibration of On-Line Respiratory Measurements. By J. O. Beaumont and W. A. Radke. System for Storage and Retrieval of Textual and Numeric Data Collected During Patient Monitoring. ...
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Journal articleProceedings International Conference on Data Engineering · September 14, 2015
Knowledge and/or data-based decision support systems can be viewed as complex control systems designed to optimize a desired criterion. As such, they aid users in transforming objects with an initial state vector to some desired outcome state by applicatio ...
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Journal articlePloS one · January 2013
The distribution of cellular source-sink relationships plays an important role in cardiac propagation. It can lead to conduction slowing and block as well as wave fractionation. It is of great interest to unravel the mechanisms underlying evolution in wave ...
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Journal articleMedical Science Educator · June 1, 2012
The learning strategy developed by Duke-NUS educators, called TeamLEAD, incorporates Team-Based Learning principles. Lectures, readings and e-learning on a given topic are completed before class; in-class activity focuses on assuring understanding, applyin ...
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Journal articleAmerican journal of physiology. Heart and circulatory physiology · November 2010
Lidocaine is a class I antiarrhytmic drug that blocks Na(+) channels and exists in both neutral and charged forms at a physiological pH. In this work, a mathematical model of pH and the frequency-modulated effects of lidocaine has been developed and incorp ...
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Journal articleSingapore General Hospital Proceedings · December 1, 2008
Each day's work, whether a clinician, researcher or homemaker, focuses on investigative strategies and problem solving. Investigative methods and problem solving are rarely addressed formally in a medical school curriculum. Our goal with Investigative Meth ...
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Journal articleJ Membr Biol · September 2005
Featured Publication
Voltage- and/or conformation-dependent association and dissociation of local anesthetic-class drugs from a putative receptor site in domain IV S6 of the sodium channel and slow conformation transitions of the drug-associated channel have been proposed as m ...
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Journal articleCardiovasc Res · March 15, 2003
OBJECTIVE: The fate of an impulse arising from stimulation is determined by the ability of the wave front to recruit sufficient Na channels from adjacent cells. Previous numerical studies of mutant Na channels revealed both the velocity of a conditioning w ...
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Journal articleIEEE transactions on bio-medical engineering · February 2003
First identified in the 1930s (Ferris et al., 1936 and Wiggers and Wegria, 1939), the concept of vulnerability applies perfectly to biological oscillators. We can safely say that vulnerability is an inherent property of any excitable media. The duration of ...
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Journal articleCardiovasc Res · January 2003
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OBJECTIVE: The vulnerable period (VP) defines an interval during which premature impulses can trigger reentrant arrhythmias leading to ventricular fibrillation and sudden death. The mechanistic basis of the success or failure of impulse propagation during ...
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Journal articleComputers in Cardiology · January 1, 2003
We propose a detailed explanation of increased variability of high-frequency (> 100 Hz) components within the QRS observed in post-myocardial infarction patients, reported in recent studies of real high-resolution ECGs. Using mathematical models of single, ...
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Journal articleJ Clin Invest · October 2002
The function of the 12 positive charges in the 53-residue III/IV interdomain linker of the cardiac Na(+) channel is unclear. We have identified a four-generation family, including 17 gene carriers with long QT syndrome, Brugada syndrome, and conduction sys ...
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Journal articleInternational Journal of Bifurcation and Chaos in Applied Sciences and Engineering · September 1, 2002
Two large clinical trials of drugs that exhibited significant antiarrhythmic properties in single cells were found to increase the rate of sudden cardiac death in patients by two to three fold over untreated patients. We hypothesized that premature excitat ...
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Journal articleBiofizika · December 1, 2001
A new approach to the analysis of variability of electrocardiograms (ECGs) typical of polymorphic arrhythmias is developed. In these ECGs, separate QRS complexes can be often hardly identified. As a result, the mathematical methods that have been elaborate ...
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Journal articleBiofizika · March 2001
A new approach to the analysis of variability of electrocardiograms (ECGs) typical of polymorphic arrhythmias is developed. In these ECGs, separate QRS complexes can be often hardly identified. As a result, the mathematical methods that have been elaborate ...
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Journal articleBiofizika · March 1, 2001
A new approach to the analysis of variability of electrocardiograms (ECGs) typical of polymorphic arrhythmias is developed. In these ECGs, separate QRS complexes can be often hardly identified. As a result, the mathematical methods that have been elaborate ...
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Journal articleIEEE transactions on bio-medical engineering · January 2001
We developed a two-dimensional ventricular tissue model in order to probe the determinants of electrocardiographic (ECG) morphology during acute and chronic ischemia. Hyperkalemia was simulated by step changes in [K+]out, while acidosis was induced by redu ...
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Journal articleBiophys J · December 2000
The role of inactivation as a central mechanism in blockade of the cardiac Na(+) channel by antiarrhythmic drugs remains uncertain. We have used whole-cell and single channel recordings to examine the block of wild-type and inactivation-deficient mutant ca ...
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Journal articleComputers in Cardiology · December 1, 2000
Pharmacological treatment of cardiac arrhythmias still arises serious questions concerning both efficacy and safety. CAST failure as well as classification based on functional characteristics revealed the arrhythmogenic potential of both class I and class ...
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Journal articleProgress of Theoretical Physics Supplement · January 1, 2000
In an excitable medium, the method of phase plane analysis of ODE reductions is often used to separate suprathreshold disturbances that collapse from disturbances that expand and result in a propagating front. Following this approach, we study here pulse f ...
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Journal articleComputers in Cardiology · December 1, 1999
A realistic evolution of ischemia from coronary artery occlusion to myocardial infarction is investigated in order to identify the relationship between micro level changes and the surface ECG. Based on the available experimental results, a complete descrip ...
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Journal articleCardiovasc Res · May 1999
OBJECTIVE: Prior studies of the modulation of the Na+ current by sympathetic stimulation have yielded controversial results. Separation of the Na+ and Ca2+ currents poses a problem in myocyte preparations. The gating of cloned Na+ channels is different in ...
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Journal articleComputers in Cardiology · December 1, 1998
In order to identify generic mechanisms for altering the ECG during ischemia, we explored changes in the action potential propagation during different ischemic conditions using simple cellular models. Based on the Beeler-Reuter and Lou-Rudy I cellular mode ...
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Journal articleBiofizika · November 1998
The mechanism of polymorphic disturbances of the heart rhythm is studied on an experimental model, isolated ventricular preparations of ground squirrel and rabbit. Polymorphic arrhythmias are identified from habitus of the isolated preparation pseudoECGs m ...
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Journal articleBiofizika · November 1, 1998
The mechanism of polymorphic disturbances of the heart rhythm is studied on an experimental model, isolated ventricular preparations of ground squirrel and rabbit. Polymorphic arrhythmias are identified from habitus of the isolated preparation pseudoECGs m ...
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Journal articleAm J Physiol Heart Circ Physiol · May 1, 1998
Several aspects of the effect of the KPQ deletion mutation on Na+channel gating remain unresolved. We have analyzed the kinetics of the early and late currents by recording whole cell and single-channel currents in a human embryonic kidney (HEK) cell line ...
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Journal articleAmerican Journal of Physiology - Heart and Circulatory Physiology · May 1, 1998
Several aspects of the effect of the KPQ deletion mutation on Na+ channel gating remain unresolved. We have analyzed the kinetics of the early and late currents by recording whole cell and single-channel currents in a human embryonic kidney (HEK) cell line ...
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Journal articleBiofizika · January 1, 1998
The mechanism of polymorphic disturbances of the heart rhythm is studied on an experimental model, isolated ventricular preparations of ground squirrel and rabbit. Polymorphic arrhythmias are identified from habitus of the isolated preparation pseudoECGs m ...
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Journal articleAnnual International Conference of the IEEE Engineering in Medicine and Biology Proceedings · December 1, 1997
The size of a circular spiral wave core is predicted on the basis of a boundary layer analysis of a spiral wave tip. Dependencies of a spiral core radius on medium parameters are found analytically and numerically for the FitzHugh-Nagumo and Beeler-Reuter ...
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Journal articleBiofizika · March 1997
A method of computer-aided visualization of autowave vortices on the cardiac tissue surface is developed. The software for research into autowave vortex evolution is designed, which allowed an adequate presentation of excitation propagation along complex t ...
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Journal articleBiofizika · March 1, 1997
A method of computer-aided visualization of autowave vortices on the cardiac tissue surface is developed. The software for research into autowave vortex evolution is designed, which allowed an adequate presentation of excitation propagation along complex t ...
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Journal articlePacing and clinical electrophysiology : PACE · February 1997
Because sudden cardiac death is usually preceded by a reentrant arrhythmia, the precipitating arrhythmia must be multicellular in origin. Therefore clinicians seeking to reduce the incidence of reentrant arrhythmias in their patients with antiarrhythmic dr ...
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Journal articlePhysical Review E Statistical Physics Plasmas Fluids and Related Interdisciplinary Topics · January 1, 1997
Spiral waves rotate either around a circular core or meander, inscribing a noncircular pattern. The medium properties determining the transition of meandering were found to be equivalent to those defining the transition from wave tip separation and attachm ...
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Journal articlePhysical Review E Statistical Physics Plasmas Fluids and Related Interdisciplinary Topics · January 1, 1997
The size of a spiral core is predicted on the basis of a boundary-layer analysis of a spiral tip in the nonkinematic limit. Dependencies of a spiral core radius on medium parameters are found analytically and numerically for two models of excitable media. ...
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Journal articleBiofizika · January 1, 1997
A method of computer-aided visualization of autowave vortices on the cardiac tissue surface is developed. The software for research into autowave vortex evolution is desigened, which allowed an adequate presentation of excitation propagation along complex ...
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Journal articleMol Pharmacol · December 1996
Inactivation has been implicated as an important determinant of the block of Na+ channel by local anesthetic-class drugs. This proposition has been difficult to examine because agents used to modify inactivation change other channel properties and both ina ...
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Journal articleBiofizika · December 1, 1996
A new type of unstability of action potential propogating in spatially inhomogenious electrically excitable media is announced. Numerical experiments with the FitzHugh-Nagumo model show that if the medium contains a region where membrane slow, outward curr ...
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Journal articleAnnual International Conference of the IEEE Engineering in Medicine and Biology Proceedings · December 1, 1996
For reentrant arrhythmias, we show that the meandering transition is determined by the medium conditions for spiral wave tip attachment-separation from an unexcitable strip of thickness that is comparable with the wavefront thickness. ...
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Journal articleComputers in Cardiology · December 1, 1996
Spiral wave tips rotate either around a circular core or meander, inscribing a non-circular pattern. The transition to meandering was found to be equivalent to the transition from wave tip separation to wave tip attachment around the end of an unexcitable ...
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Journal articleBiophysical journal · February 1996
High-frequency arrhythmias leading to fibrillation are often associated with the presence of inhomogeneities (obstacles) in cardiac tissue and reduced excitability of cardiac cells. Studies of antiarrhythmic drugs in patients surviving myocardial infarctio ...
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Journal articleAm J Physiol · January 1996
Recent voltage-clamp studies of isolated myocytes have demonstrated widespread occurrence of a transient outward current (I(to)) carried by potassium ions. In the canine ventricle, this current is well developed in epicardial cells but not in endocardial c ...
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Journal articleInternational Journal of Bifurcation and Chaos in Applied Sciences and Engineering · January 1, 1996
Sudden cardiac death is often preceded by re-entrant (spiral wave) tachyarrhythmias associated with a prolongation of the action potential wavelength. Potassium channel blockade, hypokalemia and genetic alterations in membrane ion channels (e.g. long QT sy ...
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Journal articleBiofizika · 1996
A new type of unstability of action potential propagating in spatially inhomogeneous electrically excitable media is announced. Numerical experiments with the FitzHugh-Nagumo model show that if the medium contains a region where membrane slow, outward curr ...
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Journal articleBiofizika · January 1996
A new type of unstability of action potential propagating in spatially inhomogeneous electrically excitable media is announced. Numerical experiments with the FitzHugh-Nagumo model show that if the medium contains a region where membrane slow, outward curr ...
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Journal articleAnnual International Conference of the IEEE Engineering in Medicine and Biology Proceedings · December 1, 1995
Wavelet formation following collision of a wavefront with an unexcitable obstacle is studied analytically and numerically in a two-dimensional FitzHugh Nagumo excitable medium. Conditions are found when the incident wave colliding with a thin unexcitable f ...
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Journal articleCmg Proceedings · December 1, 1995
Workstations in a local area network environment must provide a time service that is synchronized with the other clocks on the LAN. To stay synchronized, computers on a network exchange information about the time via a time service protocol and adjust thei ...
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Journal articleCirculation · August 1, 1995
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BACKGROUND: Prompted by the results of CAST results, attention has shifted from class I agents that primarily block sodium channels to class III agents that primarily block potassium channels for pharmacological management of certain cardiac arrhythmias. R ...
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Journal articleChaos Solitons and Fractals · January 1, 1995
We have modified the Beeler-Reuter model of cardiac muscle cells to account for the action of catecholamines. This model reveals the ability for slowly propagating calcium waves to coexist with the normal rapidly propagating wavefront associated with sodiu ...
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Journal articleAnnual International Conference of the IEEE Engineering in Medicine and Biology Proceedings · December 1, 1994
The initiation of a 2-D spiral wave rotation around a periodic lattice of unexcitable zones (obstacles) is studied numerically by the finite-difference method. The lattice consists of thin asymmetrical filaments formed by unexcitable (diseased) portions of ...
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Journal articleIndian journal of physiology and pharmacology · October 1994
Suppression of responses to premature stimulation has been the guiding principle in managing many cardiac arrhythmias. Recent clinical trails revealed that sodium channel blockade increased the incidence of re-entrant cardiac arrhythmias resulting in sudde ...
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Journal articlePhysica D Nonlinear Phenomena · September 15, 1994
Mechanisms for initiating rotating waves in 1D and 2D excitable media were compared and parameters affecting wavefront formation were analyzed. The time delay between two sequentially initiated wavefronts (a conditioning wave followed by a test wave) was v ...
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Journal articleCirc Res · September 1994
A rise in [K+]o, by depolarizing the resting membrane potential and partially inactivating the inward Na+ current (INa), is believed to play a critical role in slowing conduction during myocardial ischemia. In multicellular ventricular preparations, elevat ...
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Journal articleBiophys J · July 1994
Two types of the late Na channels, burst and background, were studied in Purkinje and ventricular cells. In the whole-cell configuration, steady-state Na currents were recorded at potentials (-70 to -80 mV) close to the normal cell resting potential. The q ...
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Journal articleAm J Physiol · May 1994
In voltage-clamp studies of atrial myocytes exposed to disopyramide or quinidine, pulse-train stimulation revealed use-dependent block that increased with increased pulse amplitude. Use-dependent block also became negligible at hyperpolarized holding poten ...
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Journal articleJournal of cardiovascular pharmacology · March 1994
Ethmozin (Moricizine HCl) and ethacizin are two class I antiarrhythmic drugs with different rate constants of interaction with the sodium channel. Computer simulation using the "guarded-receptor" model predicted that the combination of ethacizin and ethmoz ...
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Journal articlePhysica D Nonlinear Phenomena · February 15, 1994
Potentially life-threatening cardiac arrhythmias can be iniated with stimuli timed to occur during the "vulnerable window (VW)". We defined VW as the time interval between the "conditioning" and "test" stimuli following in sequence, during which the test s ...
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Journal articleBiophysical journal · November 1993
Featured Publication
Cardiac tissue can display unusual responses to certain stimulation protocols. In the wake of a conditioning wave of excitation, spiral waves can be initiated by applying stimuli timed to occur during a period of vulnerability (VP). Although vulnerability ...
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Journal articleJ Membr Biol · November 1993
Block of cardiac sodium channels is enhanced by repetitive depolarization. It is not clear whether the changes in drug binding result from a change in affinity that is dependent on voltage or on the actual state of the channel. This question was examined i ...
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Journal articleAm J Physiol · May 1993
The local anesthetic-class antiarrhythmic drugs produce greater depression of conduction in ischemic compared with normal myocardium. The basis for this relatively selective action is uncertain. A model of the pH-dependent interaction of tertiary amine dru ...
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Journal articleThe American journal of physiology · December 1992
This study was designed to test the hypothesis that the electrical load seen at a microelectrode impalement site is sensitive to the direction of propagation of the approaching wavefront as a reflection of an altered spatial relationship between the impale ...
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Journal articleAm J Physiol · December 1992
The results of studies on modulation of Na channel function are often difficult to interpret due to time-dependent changes in channel kinetics. Although the "tight-seal" whole cell voltage-clamp technique has proved very useful in studying the properties o ...
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Journal articleJ Clin Invest · August 1992
A number of basic and clinical studies suggest that elevation of external sodium concentrations, [Na]o, may reverse the cardiotoxic effect of local anesthetic-class drugs. The mechanisms of reversal are uncertain. The blocking action of lidocaine and disop ...
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Journal articleCirc Res · June 1992
The recovery of the sodium channel from blockade by local anesthetic antiarrhythmic drugs is voltage dependent. Recovery from lidocaine-induced blockade is accelerated by hyperpolarization, whereas that from glycylxylidide (GX) blockade has been reported t ...
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Journal articleJournal of cardiovascular pharmacology · May 1992
The vulnerable period (VP) is an interval of time during the cardiac cycle within which premature stimulation may lead to trains of responses (one: many stimulus-response coupling). Although the VP parallels the recovery of sodium channel availability, mod ...
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Journal articleAm J Physiol · April 1992
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Drugs that exhibit use-dependent Na channel blockade, including antiarrhythmic agents, tricyclic antidepressants, opiate-like analgesics, and cocaine, are linked with an increased susceptibility to cardiac arrhythmias and sudden death. Computer simulations ...
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Journal articleJournal of Statistical Planning and Inference · January 1, 1992
Many biological respomses are dependent on the frequency of excitation. Frequency-dependent processes are a class of ligand binding processes where the degree of binding site saturation may be dependent on the cumulative duration of ligand release or recep ...
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Journal articleComput Biomed Res · December 1991
A recent study of single sodium channel currents in neuroblastoma cells suggested interaction between ion channels in close proximity to one another (T. Kiss and K. Nagy, Eur. Biophys. J. 12, 13, 1985). The opening of one channel appeared to affect the lik ...
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Journal articleCirc Res · September 1991
Cardiac toxicity is a frequent manifestation in amitriptyline overdose and is felt to be due, in part, to sodium channel blockade by the drug. Another agent with sodium channel blocking properties, diphenylhydantoin, has been used clinically to reverse car ...
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Journal articleCirculation · September 1991
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BACKGROUND: The use of flecainide and encainide was terminated in the Cardiac Arrhythmia Suppression Trial because of an excess of sudden cardiac deaths in the active treatment group. Such events might arise from reentrant rhythms initiated by premature st ...
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Journal articleJournal of theoretical biology · March 1991
Application of existing models of sinoatrial node pacemaker activity and of channel-drug interaction allow us to reproduce action potential changes as a result of the blocking effect of drugs. Two calcium antagonistic drugs, nifedipine and mesudipine, were ...
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Journal articleJournal of molecular and cellular cardiology · February 1991
The frequency-dependent effects on the intraventricular conduction through the dog heart in situ produced by two class 1 antiarrhythmic drugs, ethacizin and lidocaine, with different kinetic properties were investigated. Conduction delay was measured using ...
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Journal articleJ Mol Cell Cardiol · February 1991
Lidocaine binds to sodium channels in a voltage dependent manner where depolarization enhances block and hyperpolarization relieves block. Voltage--clamp studies demonstrate that there are two components of block: one involving interaction with a binding s ...
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Journal articleCirculation · December 1990
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Although work on class III antiarrhythmics remains at an early stage, these agents still appear to possess greater efficacy and less proarrhythmia than conventional class I agents in those experimental arrhythmia models considered to be most representative ...
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Journal articleProceedings of the First Conference on Visualization in Biomedical Computing · December 1, 1990
A system of graphical software tools to facilitate the two-dimensional visualization of primary and model data is described. The system uses a direct manipulation interface developed at Duke University Medical Center. This system presents the investigator ...
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Journal articleThe American journal of physiology · November 1990
The ATP-sensitive potassium channel current (IK-ATP) was studied in excised inside-out patches from rat ventricular cells at 20-23 degrees C. The bath solution contained 140 mM KF, and the pipette solution contained 140 mM KCl and 1.2 mM MgCl2. ATP (0.5 mM ...
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Journal articleAm J Physiol · October 1990
Slowing of the recovery of the Na channel from local anesthetic block at low external pH has been well described. In contrast the Ca channel has been reported not to show such an effect. Because of the absence of this response, a two-site model for the int ...
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Journal articleAm J Physiol · August 1990
Models of ion channel blockade are frequently validated with observations of ionic currents resulting from electrical or chemical stimulation. Model parameters for some models (modulated receptor hypothesis) cannot be uniquely determined from ionic current ...
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Journal articleEnvironmental health perspectives · July 1990
Data representation, data file specification, and the communication of data between software systems are playing increasingly important roles in clinical data management. This paper describes the concept of a self-documenting file that contains annotations ...
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Journal articleThe Journal of pharmacology and experimental therapeutics · June 1990
Ethacizin, a positively charged analog of ethmozin, reduces the cardiac action potential upstroke and blocks peak sodium current (INa). We investigated ethacizin block of INa in 11 cells and ethmozin block in 4 cells at 20 degrees C. Rest block measured as ...
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Journal articleKardiologiia · March 1990
Experiments with recording the time of intraventricular reentry of the canine heart by a special protocol of stimulation showed that the first-line antiarrhythmic agents having various kinetics, ethacizine and lidocaine, compete for their binding to the Na ...
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Journal articleKardiologiya · March 1, 1990
Experiments with recording the time of intraventricular reentry of the canine heart by a special protocol of stimulation showed that the first-line antiarrhythmic agents having various kinetics, ethacizine and lidocaine, compete for their binding to the Na ...
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Journal articleComput Biomed Res · February 1990
In a previous paper we described a self-documented file and a collection of general purpose programs or tools that facilitates the management and analysis of biological data. The tools can be specified in a pipeline to accomplish a specific analysis task. ...
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Journal articleKardiologiya · 1990
Experiments with recording the time of intraventricular reentry of the canine heart by a special protocol of stimulation showed that the first-line antiarrhythmic agents having various kinetics, ethacizine and lidocaine, compete for their binding to the Na ...
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Journal articleAmerican Journal of Physiology Heart and Circulatory Physiology · December 14, 1989
The effect on calcium channels of the sodium channel antagonist, ethacizin, was studied in isolated frog ventricular cells using the whole cell voltage-clamp methodology. Ethacizin was found to block inward calcium current in a frequency-, voltage-, and co ...
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Journal articleJ Immunol · December 1, 1989
The CD7 gp40 molecule is a member of the Ig gene superfamily and is expressed on T cell precursors before their entry into the thymus during fetal development. N-terminal amino acids 1-107 of CD7 are highly homologous to Ig kappa-L chains whereas the carbo ...
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Journal articleJ Clin Invest · November 1989
The opiate analgesic propoxyphene produces cardiac toxicity when taken in overdose. We recently observed a patient with propoxyphene overdose in whom marked QRS widening was reversed by lidocaine. The reversal is apparently paradoxical as both agents block ...
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Journal articleThe American journal of physiology · November 1989
The effect on calcium channels of the sodium channel antagonist, ethacizin, was studied in isolated frog ventricular cells using the whole cell voltage-clamp methodology. Ethacizin was found to block inward calcium current in a frequency-, voltage-, and co ...
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Journal articleCirc Res · November 1989
The mechanism of interaction of lidocaine with cardiac sodium channels during use-dependent block is not well defined. We examined the blockade of single cardiac sodium channels by lidocaine and its hydrophobic derivative RAD-242 in rabbit ventricular myoc ...
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Journal articleCirc Res · September 1989
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Lidocaine block of the cardiac sodium channel is believed to be primarily a function of channel state. For subthreshold potentials, block is limited to the inactivated state, whereas above threshold, block results from the combination of open- and inactiva ...
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Journal articleJ Clin Invest · June 1989
The dynamic response of squared conduction velocity, theta 2, to repetitive stimulation in canine Purkinje fibers with quinidine was studied using a double-microelectrode technique. With stimulation, a frequency-dependent monoexponential increase in conduc ...
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Journal articleMathematical and Computer Modelling · January 1, 1989
The response of some biological processes is dependent on the frequency of stimulation. With first-order processes, the response is driven exponentially to an equilibrium determined by the value of the driving function. When the stimulus or driving functio ...
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Journal articleProceedings of the International Conference on Parallel Processing · December 1, 1988
The tool consists of a simple language for describing algorithms and an interpreter that determines the execution time on a given number of processors. The key concept is the separate specification of local computation and remote memory access in the algor ...
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Journal articleBiometrics · June 1988
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The response of some biological processes is dependent on the frequency of stimulation. With first-order processes, the response is driven exponentially to an equilibrium determined by the value of the driving function. When the stimulus or driving functio ...
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Journal articleundefined · December 1, 1987
Recent studies of the interactions between pharmacologic agents and ion channels in excitable membrane have yielded an analytical characterization of use- or activity-dependent processes. Using this model and observations of habituation and sensitization i ...
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Journal articleBiophysical journal · September 1987
Competitive ligand binding to periodically activated or accessible receptors is influenced by the interaction between ligand binding kinetics and the interval of time the binding site is accessible. This interaction produces a paradoxical reduction in boun ...
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Journal articleCirc Res · June 1987
We have examined the kinetics of closure of sodium channels using single-channel recordings in cell-attached and excised membrane patches of rabbit ventricular myocytes. Sodium-channel closure was dependent on membrane potential. The closing rate initially ...
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Journal articleComputers and biomedical research, an international journal · June 1987
Processing biomedical research data is frequently complex due to the evolutionary nature of experiments and the requisite modification of analysis software. For the past several years we have been evolving a set of software tools designed to improve our ab ...
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Journal articleJ Theor Biol · February 7, 1987
Many biological processes are characterized by models where ligand has continuous access to binding sites. Use-dependent processes such as ion channel blockade appear to represent a class of processes where binding site access is transient and is dependent ...
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Journal articleThe American journal of physiology · October 1986
Excitable membranes exposed to sodium channel blocking agents (D; local anesthetics and antiarrhythmic drugs) show a progressive reduction of peak sodium current when repetitively depolarized (use dependence). Thus, with repetitive excitation, use dependen ...
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Journal articleThe Journal of pharmacology and experimental therapeutics · July 1986
During diastole, tertiary amine local anesthetic molecules may exit cardiac sodium channels quickly through the membrane if they are neutral, or more slowly through the aqueous channel pore if they are charged. Extracellular acidosis potentiates sodium cha ...
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Journal articleBiophysical journal · April 1986
The interaction of QX222, a quaternary ammonium derivative of lidocaine, with the Na channel was studied in internally perfused squid axons under voltage-clamped conditions. A use-dependent block was observed in response to repetitive depolarizing pulses. ...
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Journal articleJournal of theoretical biology · March 1986
With repetitive stimulation, the time course of use-dependent blockade as assessed by peak membrane ion currents can be described by a sequence of blocking relationships that have the form of recurrence equations. The equations of the sequence describe blo ...
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Journal articleMol Pharmacol · October 1985
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For excitable membranes, use and frequency dependence represent a progressive incorporation of drug into gated ion channels with repetitive stimulation. In contrast to receptors where access to ligand is continuous in time, we define guarded receptors, suc ...
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Journal articleJournal of theoretical biology · August 1985
Studies of interactions between blocking agents such as antiarrhythmic drugs and gated ion channels have suggested apparent variations in binding site affinity. In this report, we develop a model by which these properties of ion channels can be explained s ...
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Journal articleCirc Res · October 1984
Current theories envision recovery from local anesthetic block of sodium channels via slow hydrophilic and fast hydrophobic paths. Extracellular pH reduction which increases cationic/neutral anesthetic form should especially prolong recovery kinetics of hi ...
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Journal articleArch Intern Med · July 1984
We used standard, large adult, and thigh-size cuffs in random order to take BPs in 470 patients. The prevalences of definite high BP [( HBP]), greater than or equal to 160/95 mm Hg) and borderline HBP [( BHBP ], greater than or equal to 140/90 less than 16 ...
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Journal articleBiophys J · July 1984
Many local anesthetics promote reduction in sodium current during repetitive stimulation of excitable membranes. Use-, frequency-, and voltage-dependent responses describe patterns of peak INa when pulse width, pulse frequency, and pulse amplitude are vari ...
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Journal articleCirculation · January 1984
We developed a quantitative approach to assess the antifibrillatory effects of short-term interventions in a canine preparation of ventricular fibrillation caused by coronary reperfusion, and applied it to evaluate the antifibrillatory effects of bretylium ...
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Journal articleCirc Res · December 1983
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Transmembrane ionic movements are thought to occur through special membrane areas or channels. Until recently, it has not been possible to study the properties of individual ionic channels, directly. We have used the extracellular patch clamp technique to ...
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Journal articleArch Intern Med · May 1983
Many hypertensive patients, especially those in outpatient clinics at large teaching hospitals, do not achieve BP control. We incorporated a physician's associate into an existing house staff medical clinic and evaluated whether this improved BP control. I ...
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Journal articleIEEE Transactions on Computers · January 1, 1983
Contiguous element region selection is a fundamental step in many image analysis applications. This application is often run on computers with virtual memory systems. The page fault behavior of the contiguous element selection algorithm is greatly influenc ...
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Journal articleCancer Treat Rep · May 1982
Accurately assessing the effect of a clinical intervention is a complex task based on observing patients and their outcomes. Two strategies, the randomized trial and the observational data bank, represent different approaches toward detecting an outcome gr ...
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Journal articleJournal of medical systems · April 1982
Clinical investigations generate a spectrum of data and data relationships that no longer fit simple data structures. To build a data management facility sufficiently flexible to deal with this spectrum of structures is thus an important problem. A general ...
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Journal articleIEEE Transactions on Nuclear Science · January 1, 1982
The effects of scatter and attenuation on single photon emission computed tomography (SPECT) images can be analyzed with the aid of sophisticated Monte Carlo simulation. Correction procedures can be evaluated by comparing corrected images with images absen ...
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Journal articleAnnals of internal medicine · April 1981
We evaluated the usefulness of computed tomography (CT) brain scanning in alcoholic patients with withdrawal seizures (n = 151) and other neurologic problems (n = 87) and compared the findings of a detailed neurologic examination to the results of CT scann ...
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Journal articleIEEE Transactions on Nuclear Science · 1981
A Monte Carlo-based computer program accurately simulates the SPECT imaging system response. The performance of the simulation is illustrated and system resolution, effects of scatter and attenuation, and the final image variance are shown to be comparable ...
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Journal articleJournal of medical systems · 1981
Chronic illness is characterized by a long response time during which many external influences can modify the system. Accurate characterization of such a system may require a large number of attributes. Such "data" complexity, in both the time and the feat ...
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Journal articleBiometrics · June 1980
Chronic diseases are in many ways more complex than acute diseases. In chronic diseases, response times to environmental effects are long, and confounding variables are numerous and may fluctuate with time. Treatment schedules are complicated and may be un ...
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Journal articleCirculation · March 1980
A simulated randomized clinical trial in coronary artery disease was conducted to illustrate the need for clinical judgment and modern statistical methods in assessing therapeutic claims in studies of complex diseases. Clinicians should be aware of problem ...
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Journal articleInstitution of Mechanical Engineers Conference Publications · January 1, 1979
Stabilizing clinical decisions can be aided by incorporating outcome data into treatment decisions. Feedback of outcome data can be managed manually for acute illnesses. When the time between intervention and outcome becomes long as in chronic disease, the ...
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Journal articlePhysics in medicine and biology · July 1978
The propagation of errors in quantitative biplane cineroentgenography was investigated to see which variables were the most critical. The analysis was carried out both for the propagation of root-mean-square errors and for errors as derived by a Taylor exp ...
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Journal articleAbstracts of Hospital Management Studies · January 1, 1978
The objective of the research is to establish a data bank consisting of clinical data from patients with coronary artery disease. This extensive, longitudinal and reliable collection of data represents an aggregated clinical experience that can be shared w ...
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Journal articleChromosoma · April 1977
Relative length is a constant and distinctive characteristic for each autosomal SC, despite variations in absolute length from cell to cell. Arm ratio is distinctive for each SC except for two of the three sub-acrocentrics, and serves, together with relati ...
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Journal articleCirculation · March 1977
Relationships between enzyme estimates (EE) and histologic measurements of infarct size (HIS) were analyzed in 14 conscious dogs with permanent occlusion of the circumflex coronary artery. EE were derived from serial CPK, CPK-MM, CPK-MB, and CPK-BB. Estima ...
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Journal articleACM SIGMIS Database · January 1, 1977
There is uncertainty in the management of an individual with a chronic illness. The uncertainty results from lack of information about groups of similar patients. A feedback model for patient care is presented and its implementation discussed. The model re ...
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Journal articleCirculation · December 1975
The authors followed 536 medically managed patients with angiographically documented coronary artery disease for up to 4 years, and examined antemortem clinical, anatomical, and hemodynamic characteristics of the 29 patients who died suddenly during the fo ...
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Journal articleArchives of internal medicine · August 1975
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A data bank containing our clinical experience with more than 3,000 patients with suspected and documented ischemic heart disease is being used to expand our ability to care for patients. This report describes how the experience is documented, stored, and ...
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Journal articleCirculation · March 1975
This report represents our experience with 522 consecutive patients with acute myocardial infarction admitted directly to the Duke Coronary Care Unit. Fifty items of information were used to characterize the patients, their hospital course and follow-up. S ...
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Journal articleComputer · January 1, 1975
The nature of the contractions of the heart wall has long been recognized as indicative of the presence and degree of atherosclerotic lesions in the coronary arteries. More recently, the coronary arterial tree-itself has been studied and the changes in len ...
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Journal articlePROC.SOC.PHOTO-OPT.INSTR.ENGIN. · January 1, 1975
This paper describes a collection of simple ideas and procedures to aid in the collection and analysis of coronary arterial trees. The uses to which the tree data will be put include the evaluation of myocardial function and the formation of a library suff ...
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Journal articleSPIE Semin Proc · January 1, 1975
Coronary cineangiography is a routine procedure in the authors' hospital for evaluation of the coronary circulation. From the biplane cineangiograms one obtains a visual representation of coronary perfusion. In addition the three-dimensional structure of t ...
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Journal articleMathematical Biosciences · January 1, 1975
The concept of an abnormality of glutamine metabolism in primary gout was first proposed on the basis of isotope data: when 15N-glycine was administered to gouty subjects, there was disproportionately great enrichment of N-(3+9) of uric acid, wh ...
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Journal articleComputer · January 1, 1975
The ability of the computer-based data bank to provide a quality of information about like patients that is not available in textbooks, journals, and monographs creates a degree of excitement and timeliness in the long-term management of chronically ill pa ...
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Journal articleundefined · January 1, 1974
The nature of the contractions of the heart wall has long been recognized as indicative of the presence and degree of atherosclerotic lesions in the coronary arteries. More recently, the coronary arterial tree itself has been studied and the changes in len ...
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Journal articleThe Journal of clinical investigation · October 1973
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THE CONCEPT OF AN ABNORMALITY OF GLUTAMINE METABOLISM IN PRIMARY GOUT WAS FIRST PROPOSED ON THE BASIS OF ISOTOPE DATA: when [(15)N]glycine was administered to gouty subjects, there was disproportionately great enrichment of N-(3 + 9) of uric acid, which de ...
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Journal articleundefined · January 1, 1971
Following is a continuation of the listing of papers presented: Automatic Calibration of On-Line Respiratory Measurements. By J. O. Beaumont and W. A. Radke. System for Storage and Retrieval of Textual and Numeric Data Collected During Patient Monitoring. ...
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Journal articleCirculation · October 1970
Hemodynamic and clinical evaluations of 123 patients with acute myocardial infarction were performed during the first hour of admission to the hospital. In the 123 patients, the right atrial pressure was less than 10 mm Hg in 49 patients, the right atrial ...
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Journal articleThe Journal of clinical investigation · May 1969
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This study was designed to assess the independent effects of stroke volume and heart rate on the phases of systole and other selected hemodynamic parameters. By means of the pressure gradient technique instantaneous blood pressure and flow were recorded in ...
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