AIMTo study the effects of the 50 Hz-filter circuit in a microelectrode amplifier on cardiac action potential waveform and parameters.

METHODSCardiac action potential signals were fed into a microcomputer through a glass microelectrode, a microelectrode amplifier, a differentiator and A/D converter. The cardiac action potential signals were recorded and analyzed with 50 Hz-filter circuit and without it, and the frequency spectrum in the signals was analyzed with the fast Fourier transformation.

RESULTSWhen the 50 Hz-filter circuit was used, the phase 0 of the potential waveform was seriously distorted and prolonged. The maximal rate of depolarization at the phase 0 was cut down, while the other parameters were not effected.

CONCLUSIONThere has already been much 50 Hz element in the action potential waveform. During amplifying the cardiac action potential signal, the 50 Hz-filter circuit should not be turned on. Otherwise, the experiment results will be effected.

Action Potentials ; physiology ; Amplifiers, Electronic ; Animals ; Guinea Pigs ; Myocytes, Cardiac ; physiology ; Papillary Muscles ; cytology ; physiology

The membrane permeability to potassium at a resting state is greater than to any other ions and the maintenance of resting membrane potential is largely dependent on K+ concentration of outside medium (Hodgkin and Horowicz 1959), i.e. an increase of K+ concentration of medium induces a depolarization, vice versa. However, on the contrary to this prediction, in some mammalian heart muscle a reduction of external K+ concentration induces a depolarization of membrane potential rather than a hyperpolarization (Vassalle 1965). In this study it was aimed to elucidate the possible mechanism of spontaneous depolarization induced by low external K+ in canine Purkinje fibers. The membrane potential was constantly recorded while components of cations in the bathing medium were replaced one by one by equimolar sucrose until the low K+ induced depolarization was blocked. The results are summarized as follows; The membrane potential of canine Purkinje fibers was spontaneously depolarized by low external K+, and the magnitude of depolarization was not affected by verapamil TEA, and a partial replacement of external Na+ and Ca2+ with choline chloride. But the membrane potential was hyperpolarized only when the all external cations were substitued with sucrose; and this hyperpolarization was disappeared again by substitution of sucrose with choline chloride. From these results, it may be concluded that the depolarization induced by low external K+ in canine Purkinje fibers is due to the nonspecific increase of membrane permeability to external cations and/or combinations with decreased K+ conductance.
Animal ; Dogs ; Guinea Pigs ; Heart/physiology* ; Membrane Potentials/drug effects* ; Papillary Muscles/physiology ; Potassium/pharmacology* ; Purkinje Fibers/physiology ; Rest

Action Potentials ; drug effects ; physiology ; Animals ; Female ; Guinea Pigs ; Heart Ventricles ; drug effects ; Papillary Muscles ; drug effects ; physiology ; Progesterone ; pharmacology

OBJECTIVEThe clinical diagnosis and treatment of ischemia mitral regurgitation (IMR) remained difficult because of its unclear mechanisms. This paper reviews studies on the mechanisms of IMR during the last 20 years, and discusses the relevance of the various mechanisms.

DATA SOURCESData used in this review were mainly from CNKI and Pubmed in English. The search terms were "ischemia mitral regurgitation mechanism", "myocardial infarction" AND "mitral regurgitation".

STUDY SELECTIONArticles were selected if they involved mechanisms of IMR.

RESULTSIMR is one of the common complications of coronary artery disease. But currently, the clinical diagnosis and treatment of IMR remained difficult because of its unclear mechanisms.

CONCLUSIONSFor now, dominating theory of ischemic mitral regurgitation mechanisms are left ventricular remodeling, imbalance of leaflet tethering and the closing force, left ventricular dysfunction, changes in spatial structure of the annulus and the dyssynchrony of the left ventricular electromechanical activity.

Animals ; Humans ; Mitral Valve Insufficiency ; etiology ; Myocardial Ischemia ; complications ; Papillary Muscles ; physiology ; Systole ; Ventricular Dysfunction, Left ; complications ; Ventricular Remodeling

OBJECTIVE: To evaluate the influence of papillary muscles and trabeculae on left ventricular (LV) cardiovascular magnetic resonance (CMR) analysis using three methods of cavity delineation (classic or modified inclusion methods, and the exclusion method) in patients with hypertrophic cardiomyopathy (HCM). MATERIALS AND METHODS: This retrospective study included 20 consecutive HCM patients who underwent 1.5-T CMR imaging with short-axis cine stacks of the entire LV. LV measurements were performed using three different methods of manual cavity delineation of the endocardial and epicardial contours: method A, presumed endocardial boundary as seen on short-axis cine images; method B, including solely the cavity and closely adjacent trabeculae; or method C, excluding papillary muscles and trabeculae. Ascending aorta forward flow was measured as reference for LV-stroke volume (SV). Interobserver reproducibility was assessed using intraclass correlation coefficients. RESULTS: Method A showed larger end-diastole and end-systole volumes (largest percentage differences of 25% and 68%, respectively, p < 0.05), compared with method C. The ejection fraction was 55.7 +/- 6.9% for method A, 68.6 +/- 8.4% for B, and 71.7 +/- 7.0% for C (p < 0.001). Mean mass was also significantly different: 164.6 +/- 47.4 g for A, 176.5 +/- 50.5 g for B, and 199.6 +/- 53.2 g for C (p < 0.001). LV-SV error was largest with method B (p < 0.001). No difference in interobserver agreement was observed (p > 0.05). CONCLUSION: In HCM patients, LV measurements are strikingly different dependent on whether papillary muscles and trabeculae are included or excluded. Therefore, a consistent method of LV cavity delineation may be crucial during longitudinal follow-up to avoid misinterpretation and erroneous clinical decision-making.
Adult ; Aged ; Cardiomyopathy, Hypertrophic/*pathology ; Female ; Heart Ventricles/physiopathology/*radiography ; Humans ; *Magnetic Resonance Imaging, Cine ; Male ; Middle Aged ; Papillary Muscles/*physiopathology ; Retrospective Studies ; Stroke Volume/physiology ; Systole/physiology

The cardiac electrophysiological effects of hydrogen sulfide (H2S) were examined in guinea pig papillary muscles in vitro using intracellular microelectrode technique. The results obtained were as follows: (1) the duration of action potential (APD) in the normal papillary muscles was decreased by NaHS (H(2)S donor, 50, 100, 200 micromol/L) in a concentration-dependent manner; (2) in partially depolarized papillary muscles, 100 micromol/L NaHS not only reduced APD, but also decreased the amplitude of action potential (APA), overshoot (OS) and maximal velocity of depolarization at phase 0 (V(max)); (3) pretreatment with ATP-sensitive K(+) (K(ATP)) channel blocker glibenclamide (20 micromol/L) partially blocked the effects of NaHS (100 micromol/L); (4) pretreatment with L-type Ca(2+) channel agonist Bay K8644 (0.5 micromol/L) also partially blocked the effects of NaHS (100 micromol/L); (5) pretreatment with Ca(2+)-free Krebs-Henseleit solution containing glibenclamide (20 micromol/L) completely blocked the effects of NaHS (100 micromol/L); (6) APD in the normal papillary muscles was increased by DL-propargylglycine (PPG, an inhibitor of cystathionine gamma-lyase, 200 micromol/L). All these results suggest that the electrophysiological effects of H(2)S on papillary muscles in our study are due to an increase in potassium efflux through the opening of K(ATP) channels and a decrease in calcium influx. Endogenous H(2)S may act as an important regulator in electrophysiological characters in papillary muscles.
Action Potentials ; physiology ; Animals ; Calcium ; metabolism ; Female ; Guinea Pigs ; Hydrogen Sulfide ; pharmacology ; In Vitro Techniques ; KATP Channels ; metabolism ; Male ; Papillary Muscles ; metabolism ; physiology

Action Potentials ; drug effects ; Animals ; Estradiol ; pharmacology ; Female ; Guinea Pigs ; Heart Ventricles ; cytology ; Myocardial Contraction ; drug effects ; Papillary Muscles ; drug effects ; physiology ; Progesterone ; pharmacology

The purpose of this study was to investigate the effects of phytoestrogen genistein (GST) on delayed after depolarization (DAD) and triggered activity (TA) induced by ouabain in guinea pig papillary muscles. Action potentials (APs) were recorded from the guinea pig papillary muscles with standard glass microelectrode technique. The results are as follows: (1) DAD and TA induced by ouabain (1 micromol/L) were markedly inhibited by pretreatment with GST (10, 50, 100 micromol/L) in a concentration-dependent manner. (2) NG-nitro-L-arginine methyl ester (L-NAME, 1 mmol/L), an NO synthase inhibitor, failed to affect the above effects of GST. (3) 5 micromol/L 17beta-estradiol (E2) or 10 micromol/L GST alone showed no effects on DAD and TA, whereas GST combined with E(2) at the same doses exerted significant inhibitory effects on DAD and TA. Since GST is known to reduce the calcium influx, it is suggested that GST might have antiarrhythmic effects, possibly by reducing calcium influx. The antiarrhythmic effects of GST may contribute to its cardioprotective action.
Action Potentials ; drug effects ; Animals ; Genistein ; pharmacology ; Guinea Pigs ; Male ; Neuromuscular Depolarizing Agents ; pharmacology ; Ouabain ; pharmacology ; Papillary Muscles ; drug effects ; physiology ; Phytoestrogens ; pharmacology

The purpose of this study was to investigate the electrophysiological effects of resveratrol on guinea pig papillary muscles and the underlying mechanism. Action potentials were recorded by using intracellular microelectrode technique. The results obtained are as follows: (1) In normal papillary muscles, resveratrol (30, 60, and 120 micromol/L) shortened the duration of action potential (APD) in a concentration-dependent manner. (2) In partially depolarized papillary muscles, resveratrol (60 micromol/L ) not only shortened APD, but also decreased the amplitude of action potential (APA), overshoot (OS) and maximal rate of depolarization in phase 0 (Vmax). (3) Perfusion with Ca2+-free K-H solution, completely abolished the effects of resveratrol (60 micromol/L) on papillary muscles. (4) Application of potassium channel blocker tetraethylammonium chloride (TEA, 20 mmol/L) did not prevent the effect of resveratrol (60 micromol/L) on action potential. (5) Pretreatment with NG-nitro-L-arginine methyl ester (L-NAME, 1 mmol/L), a nitric oxide (NO) synthase inhibitor, failed to abolish the effect of resveratrol (60 micromol/L). All these results indicate that the electrophysiological effects of resveratrol on guinea pig papillary muscles are likely due to the reduction of calcium influx, which might not be mediated by NO.
Action Potentials ; drug effects ; Animals ; Calcium Channel Blockers ; pharmacology ; Guinea Pigs ; In Vitro Techniques ; Male ; Microelectrodes ; Papillary Muscles ; drug effects ; physiology ; Stilbenes ; pharmacology

OBJECTIVETo investigate the electrophysiological changes of ventricular myocardium of rats with experimental diabetes and the effect of adenosine on its electrophysiology.

METHODSDiabetes was induced in male SD rats, using a single injection of alloxan into tail vein. Untreated animals were used as controls. The electrocardiograms (ECG) were recorded 6 weeks after diabetes was induced. Effects of adenosine on ventricular myocardium in diabetic rats and controls were observed by measuring the transmembrane potentials with conventional glass microelectrodes.

RESULTSQT interval in ECG and action potential duration (APD) at all levels (APD30, APD50, APD70 and APD90) were significantly prolonged in right ventricular papillary muscle 6 week after diabetes was induced. No differences were observed in the resting membrane potential (RP), action potential amplitude (APA) and overshoot (OS) as well as the maximum rate of depolarization (Vmax) between the diabetic rats and control rats. At concentration of 10 approximately 400 micromol/L, ADO had little influence on all transmembrane potential parameters of right ventricular papillary muscle in diabetic rats and controls. At 500 micromol/L, ADO shortened APD30, APD50, APD70 and APD90 of control group, while having no effect on diabetic rats.

CONCLUSIONQT interval in ECG and APD at all levels are significantly prolonged in right ventricular papillary muscle of experimentally induced-diabetic rats.

Action Potentials ; drug effects ; Adenosine ; pharmacology ; Animals ; Anti-Arrhythmia Agents ; pharmacology ; Diabetes Mellitus, Experimental ; physiopathology ; Electrocardiography ; Electrophysiology ; Male ; Papillary Muscles ; physiology ; Rats ; Rats, Sprague-Dawley ; Ventricular Function