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P Pucelík

Publications and source records attributed to P Pucelík.

At least 19 recordsLinked to original sources
PubMed2000

[Na+/Ca+ exchange: structure, mechanism, regulation and function].

The Na+/Ca2+ exchange is a plasma membrane system for the countertransport of Na+ and Ca2+ ions. The system can transport Ca2+ both into and out of the cell and therefore it plays a crucial role in the calcium homeostasis. The system works in electrogenic way (3 Na+ are exchanged for 1 Ca2+) and thus it influences the electrogenic properties of excitable cells. Due to new techniques of electrophysiology and molecular biology a lot of information about transport mechanism, regulation and possible physiological and pathophysiological roles of the exchanger was accumulated. This review summarises new findings and shows progress in this attractive field of biological research.

Biological Transport, Active↗
PubMed1999

Effects of strontium ions on contraction and action potential in rabbit papillary muscles. A comparison with effects of tetraethylammonium ions.

The effects of Sr2+ on contraction and action potential were studied in rabbit papillary muscles and compared with effects of tetraethylammonium (TEA+). The membrane potential was measured with KCl-filled microelectrodes and the contraction was simultaneously recorded using a mechanoelectrical transducer. A partial (90%) substitution of extracellular Ca2+ (Ca2+e) by Sr2+ produced stimulation frequency-dependent prolongation of the action potential (AP) with a dominant phase "plateau" as well as prolongation of the contraction. At low frequencies where the AP prolongation was well pronounced, the contraction became biphasic. The effect of Sr2+ on both AP and contraction was blocked by nifedipine (10 mumol/l) or by increasing Ca2+e. Ryanodine suppressed the early contraction component only. AP was prolonged to a similar extent and in the same frequency-dependent manner by TEA+ (20 mmol/l). Despite similar AP configuration, no biphasic contraction developed in the presence of TEA+. High Ca2+e (10 mmol/l) or low Na+e (70 mmol/l) suppressed the TEA+ effect on AP. The data indicate that the two components of the biphasic contraction are of different origin; the early one is activated by activator cation released from the sarcoplasmic reticulum while the late one results from the Sr2+ entry across the sarcolemma via L-type Ca2+ channels.

Action Potentials↗
PubMed1990

Mechanical and electrical manifestations of the papillary muscles of verapamil-treated adult guinea-pigs under steady state conditions and after a pause.

The authors studied the effect of verapamil in 10(-7) to 10(-4) mol.l-1 concentration on the duration of action potentials (AP) and the corresponding isometric contractions (MG) from the right ventricular papillary muscles of adult guinea-pigs. In the steady state, using stimulation frequencies of 0.1, 1 and 2 Hz, verapamil caused dose- and use-dependent shortening of the AP plateau phase (D0) in 10(-5) and 10(-4) mol.l-1 concentration; lower concentrations did not affect the D0. With all the given concentrations, the MG fell in relation to the dose and the stimulation frequency. The pause regimen was defined by the induction of a steady state at 1 Hz frequency, followed by the interpolation of a pause lasting 5 s to 600 s and its effect was studied on the first and second AP after the pause and on the corresponding MG, without any pharmacological treatment and in the presence of verapamil (10(-5) mol.l-1). In the absence of the drug, slight lengthening of the D0 and weakening of the MG, proportional to the length of the pause, occurred after the pause. In the presence of verapamil, the first post-rest contraction after a 10 s pause attained five-fold the value in the steady state, while the second post-rest contraction was much weaker than the first. The possibility that verapamil acts on intracellular links in calcium metabolism, and of disproportion of its effect on the D0 and on contractility when it is administered in low concentrations, is discussed. The most likely mechanism of this effect is the presence of a negative feedback between calcium release from the sarcoplasmic reticulum and membrane electrogenesis.

Action Potentials↗
PubMed1987

Influence of a period of inactivity on the duration of post-rest action potentials of the mammalian working ventricular myocardium in correlation to the preceding stimulation frequency.

Experiments were carried out on the working right ventricular myocardium of adult cats, guinea-pigs and rabbits. Membrane voltage was recorded by the glass microelectrode technique and the preparations were stimulated with frequencies of 5, 1 and 0.2 Hz. After a steady state had been reached, a pause (TP) lasting 10-600 s was interpolated. The influence of TP on the duration (D) of post-rest action potentials (AP) was studied; the effect of the pause was measured at electric zero level (D0) and at further repolarization levels (-20, -40 and -60 mV, given here as D-20, D-40 and D-60). At 1 and 0.2 Hz frequency, the cat myocardium displayed lengthening of the AP proportional to the duration of the pause; at 5 Hz frequency, D0 reacted by lengthening up to TP = 120 s and to further pauses by slight shortening. D-60, at all frequencies, lengthened throughout the whole of the given TP range. The rabbit myocardium, at all the given frequencies, reacted up to TP = 60-120 s by marked shortening of post-rest AP at all repolarization levels; with longer pauses the AP lengthened. At 5 Hz frequency the guinea-pig myocardium reacted similarly to the cat myocardium; at the lower stimulation frequencies, the pause-induced changes in the post-rest AP were less strongly expressed. In all the given types of myocardium, the most pronounced post-rest AP reactions were those at electric zero level (the plateau phase of the AP); towards more negative repolarization values and with lower pre-pause stimulation frequencies they were less strongly expressed.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1985

Effect of a pause on action potentials of the working ventricular myocardium of human embryos.

The effect of a period of rest (Tp) lasting from 5 to 120 s on the action potentials (AP) of the ventricular myocardium of 9- to 11-week human embryos was studied. The result was shortening of the AP proportional to the duration of the pause and it was accompanied by a shift of the AP plateau phase to more negative membrane voltages. Shortening of the AP during the pause was more pronounced in solutions with a half extracellular calcium concentration. Recovery from the effect of the pause took place significantly more slowly in solutions with the lower extracellular calcium concentration than in the presence of a normal concentration.

Action Potentials↗
PubMed1984

Action potentials of the rabbit, guinea pig, dog and albino rat working ventricular myocardium under interpolated extrasystole conditions during postnatal ontogenesis.

Experiments were carried out on the working myocardium of the right heart ventricle of newborn and adult rabbits, guinea-pigs, dogs and albino rats. In the dog, the guinea-pig and the rabbit, after ten action potentials (AP) elicited with 1 Hz frequency we always interpolated an extrasystole at an interval (TE) of 100-900 ms. In albino rats we used a basic frequency of 2 Hz and a TE of 30-370 ms from the last regular AP. Using glass microelectrodes, we recorded the extrasystolic AP (EAP) and the next subsequent AP (2AP). The results were evaluated by constructing graphs of the correlations of the duration of the plateau phase (D0) to TE and of the duration of repolarization to -60 mV level (D60) to the TE. In the myocardium of newborn rabbits, guinea-pigs and dogs, with short TE both D0 and D60 of the EAP are shorter than in the steady state (SS), while for the 2AP the same parameters are influenced only a little. As the TE lengthens, the EAP gradually acquire a length corresponding more to the SS. With TE longer than half the duration of the cycle in the steady state the EAP return to normal, while the 2AP become shorter. The effect of extrasystole on the rat EAP and 2AP diminished with advancing age. In the myocardium of adult rabbits and adult guinea-pigs, and slightly in the myocardium of adult dogs and newborn rats, we observed that the duration of the EAP, with certain TE, was greater than in the steady state.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1984

Effect of acetylcholine and adrenaline on ventricular action potentials of the human embryonic myocardium.

Using the glass microelectrode technique we measured the effect of adrenaline (ADR, 10(-5) mol . l-1) and acetylcholine (ACh, 10(-5) mol . l-1) on action potentials (AP) of the ventricular myocardium of 8- to 11-week-old human embryos. ACh prolonged the AP (by 20%), without affecting voltage of the plateau phase. ADR markedly elevated the plateau phase (by 8 mV) and prolonged the AP (by up to 40% of the initial duration). The ACh effect attained the maximum in 5-7 min and was frequency dependent. The ADR effect reached the maximum in 1-2 min. Neither ACh nor ADR affected the resting membrane potential value. The effect of ACh was blocked by atropine (10(-6) mol . l-1), showing that it is mediated by way of M-receptors. Propranolol (6.10(-6) mol . l-1) only partly blocked the effects of ADR. The results show that the human ventricular myocardium is already sensitive to the action of ACh and ADR before autonomic innervation of the heart develops.

Acetylcholine↗
PubMed1983

Electromechanical relationships of rabbit papillary muscle under interpolated extrasystole conditions and after a pause.

The aim of the study was to describe and attempt to explain certain specific features of electromechanical coupling in the rabbit myocardium. Electromechanical correlations in the papillary muscles of the right ventricle of adult rabbit hearts were studied by a programmed stimulation technique. The duration of action potentials (AP) was measured in the plateau phase (Do, ms) and at -80 mV level (D80, ms), together with the intensity of the corresponding isometric contractions (MG, arbitrary units). After twenty AP of 1 Hz frequency, we interpolated an extrasystole with a variable interval (TE = 100-900 ms) and measured D0 and MG of the premature AP and the first AP of the subsequent cycle. When a steady state at 1 Hz frequency had been reached, we interpolated pauses (Tp) of 5 to 600 s and read D80 and MG of the first to the tenth contraction after the pause. The extrasystole D0 attained the maximum at TE = 260 ms and then fell abruptly. The MG of extrasystoles with a longer TE grew from the lowest value (0.3), attained 1 at TE = 700 ms and then remained stable. The first contraction after extrasystole displayed distinct postextrasystolic potentiation (MG = 2), while D0 was unwontedly short. Prolongation of TE was accompanied by an increase in its D0 value and by a steep drop in MG (to as little as 0.2). D80 of the first AP evoked after the pause fell proportionally to log Tp and then, from Tp = 60 s, gradually rose. The MG value of the first contraction after the pause fell proportionally to log Tp. The AP recovered much more rapidly than contractility from the effect of the pause. In the discussion, an attempt is made to explain the found correlations on the basis of differences in the behaviour of the calcium current channel system in the rabbit myocardium and a commentary on electromechanical correlations is based on the hypothesis that the free sarcoplasmic calcium level determines both membrane electrogenesis and the inotropic state.

Action Potentials↗
PubMed1983

An analysis of the postnatal development of the action potential repolarization process in the working ventricular myocardium of albino rats (effect of tea, frequency, verapamil and adrenaline).

Using the glass microelectrodes techniques, we analysed the causes of the shortening of the ventricular myocardial action potentials (AP) of albino rats during postnatal development. Delayed outward currents were blocked with tetraethylammonium (TEA) in 20 mmol.l-1 concentration. TEA led to prolongation of action potentials and to accentuation of frequency sensitivity in all the given age groups, but a block of TEA-sensitive currents nevertheless does not permit the conclusion that the cause of postnatal AP shortening is due to an increase in the intensity of outward currents. Slow inward current (Isi) were blocked with verapamil (2.10(-5) mol.l-1), which markedly shortened the myocardial AP of newborn rats; with advancing age its effect diminished and shifted to the negative membrane voltage level. The Isi was stimulated by adrenaline (10(-5) mol.l-1), which markedly prolonged the AP of newborn animals; with advancing age its effect rapidly diminished and was virtually undetectable in 10-day-old animals. The results indicate that postnatal AP prolongation is caused by a drop in the Isi rate rather than by the growth of outward repolarizing currents.

Action Potentials↗
PubMed1983

Action potentials of the working ventricular myocardium of newborn and adult dogs in the steady state and after a pause.

The aim of the study was to find and measure any differences in the electrophysiological manifestations of the dog working ventricular myocardium during postnatal development. The experiments were performed with the right working ventricular myocardium of eight adult (A) and seven newborn (N) beagles. Using the glass microelectrode technique and programmed stimulation we measured the resting membrane potential (RMP), the duration of action potentials (AP) in the plateau phase (D0) and AP duration at the level of repolarization at -60 mV (D60). Two stimulation programmes were used: 1) stimulation at different frequencies in the steady state (0.1 Hz to 5 Hz) and 2) the effect of a pause (Tp, duration 10 s to 600 s) on D0 and D60 of the first post-rest AP. During postnatal life the RMP value rose from -80 mV (N) to -86.6 mV (A). AP duration in the steady state at 1 Hz stimulation frequency was significantly longer, at both the given levels, in adult animals (D0: N = 56.1 ms, A = 106.1 ms; D60: N = 141.2 ms, A = 212 ms). In the steady state the frequency sensitivity of the neonatal myocardium differed from that of the adult myocardium. In both groups, stimulation frequencies of over 1 Hz shortened the AP, while in A frequencies under 1 Hz markedly prolonged D60 and slightly prolonged D0. Conversely, a decrease in the stimulation frequency shortened both D0 and D60 in N. In the case of A a pause led to marked lengthening of D60 and weak lengthening of D0.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1983

Do differences develop in the electrogenesis of action potentials of the right and left ventricle of the guinea-pig heart during postnatal development.

Using the glass microelectrodes technique we measured the duration of action potentials (DAP) of the working myocardium of both ventricles in newborn and adult guinea-pigs in the steady state during stimulation with different frequencies and after a pause lasting 10--600 s. The resting membrane potential (RMP) value in the myocardium of newborn and adult animals was the same (85.3 mV and 86.3 mV respectively). The DAP of the right ventricular myocardium of newborn guinea-pigs was longer than in the left ventricle (p less than 0.02). Postnatally the action potentials (AP) of the left ventricular myocardium lengthened significantly, but the increase in the DAP of the right ventricular myocardium was very small, so that in adulthood the AP of the left ventricular myocardium were longer than those of the right ventricle (p less than 0.01). The frequency sensitivity of the guinea-pig myocardium was similar to the frequency sensitivity of the dog or cat myocardium; in both the neonatal and the adult myocardium it had the same character, but was quantitatively more pronounced in adult animals. An increase in the stimulation frequency from 0.5 Hz to 5 Hz slightly depressed the RMP. The first AP after the pause was longer and was proportional to the logarithm of the duration of the resting period. The effect of the pause was more noticeable in the myocardium of adult animals. Recovery of the AP from the effects of the pause was slow during stimulation with 1 Hz frequency and probably corresponded to recovery of intracellular calcium balance relationships. The results not only show dissimilarity of the neonatal and adult myocardium, but are also evidence of ontogenetically dependent differences in the character of electrogenesis in the left and right ventricular myocardium.

Action Potentials↗
PubMed1982

Postnatal development of electrophysiological manifestations of the working ventricular myocardium of albino rats.

To elucidate the postnatal development of electrogenesis in the rat ventricular myocardium, we investigated specimens of the right ventricles of rats of different ages (newborn, 2 days, 5 days, 10 days and adult) by means of glass microelectrodes and a programmable stimulator. The resting membrane potential rose from -82 mV (newborn) to -89.6 mV (adult). During the first 10 postnatal days the plateau phase of the action potential (AP) shortened from 46 ms to 16 ms; in adulthood its duration was 9.6 ms. An increase in the stimulation frequency from 2 Hz to 10 Hz led to pronounced shortening of the myocardial AP of newborn and 2-day-old rats; with advancing age the influence of a mounting frequency diminished and the myocardium of adult rats was frequency-insensitive. The first AP evoked after a rest interval in the myocardium of newborn animals was prolonged proportionally to the logarithm of the duration of the interval; the AP of adult rats was unaffected by the length of the interval. During the rest interval diastolic depolarization appeared on the myocardium of newborn rats; with advancing age it slowed down and the decrease in membrane voltage was smaller. In the adult rats myocardium there was no diastolic depolarization.

Action Potentials↗
PubMed1982

Basic electrophysiological parameters and frequency sensitivity of the ventricular myocardium of human embryos.

The basic electrophysiological manifestations of the ventricular myocardium of twelve 7- to 12-week human embryos were measured with a glass electrode and a programmed stimulation technique. The resting membrane potential value was 79.37 +/- 0.34 mV and the overshoot 32.7 +/- 0.57 mV; the action potential (AP) duration at 1 Hz stimulation frequency was 120.0 +/- 5.7 ms at AP plateau phase levels and 258 +/- 17 ms at the level corresponding to 95% repolarization. The duration of the AP was a function of the stimulation frequency. i.e. it altered in correlation to the stimulation programme fully developed frequency sensitivity). In stimulation with different frequencies the duration of the steady state AP was in an inverse relation to the stimulation frequency, the maximum changes being found in the terminal repolarization zone. An interpolated extrasystole mainly affected the duration of the plateau phase.

Action Potentials↗
PubMed1981

Action potentials of the right ventricular working myocardium of newborn and adult rabbits under paired stimulation conditions.

The effect of paired stimulation on the action potentials of the working ventricular myocardium of newborn and adult rabbits was studied with the aim of elucidating the postnatal development of electrogenesis in cardiac cells. After a 2 minutes' rest pause we applied two identical rectangular electric pulses (duration 0.1-1 ms, voltage double the stimulation threshold) with an exactly defined interval, T (100 ms to 20 s). In the recordings we evaluated the duration of the plateau phase of the first (D1) and the second (D2) action potential for given stimulation pairs. The area formed by the course of the first (A1) and second (A2) action potential above the resting membrane potential value was determined planimetrically. Graphs of the correlations of D2/D1 to T and of A2/A1 to T were constructed for the evaluation. The D2/D1 curve for adult animals rose from minimum T values, attained the maximum at T=260 ms and then gradually fell. In newborn rabbits, the corresponding curve, in the majority of cases, displayed a value of T=1. The correlations of A2/A1 to T in adult animals were similar to the course of the D2/D1 curve, and the same applied to newborn animals. The results show that the working right ventricular myocardium of the adult rabbit is capable of reacting to altered stimulation intervals by a change in the duration of the plateau phase, while the myocardium of newborn animals is frequency-insensitive. The rest pause did not affect the duration of action potentials in newborn rabbits, but in adult animals it caused marked shortening of the action potential. The differences found between the neonatal and adult myocardium are probably related to rhe characteristics of the channel systems of the slow Ca-dependent inward current.

Action Potentials↗