Search PubMed⌕ Search

Biomedical subjects

N I Kukushkin

Publications and source records attributed to N I Kukushkin.

At least 19 recordsLinked to original sources
PubMed1998

Weak combined magnetic field affects basic and morphine-induced rat's EEG.

The present study was undertaken to find out, whether weak combined magnetic field (CMF) with intensity comparable to that of the Earth's static magnetic field can influence the EEG activity of the rat's brain at normal (non-treated animals) conditions and after intraperitoneal (i.p.) and intracerebroventricular (i.c.v.) administration of morphine in experimental animals bearing chronically implanted electrodes and cannules. Most of the experiments were performed using CMF containing co-linear static (20.9 microT) and alternating sinusoidal (20.9 microT, 48 Hz) components, i.e., tuned for Ca2+-resonance. The effects of the field were estimated by comparison of the averaged EEG frequency spectra in the range of frequencies between 0.8-23 Hz in experimental and control animals. Statistically significant effects of CMF were observed both in non-treated and morphine-treated rats. However, the most profound effect-the drastic power reduction at most EEG frequencies-appeared in the animals subjected to the i.p.-injection of morphine. These results show that weak CMF can influence the spontaneous electrical brain activity. The data obtained are consistent with the findings of other groups demonstrating that weak magnetic fields may drastically modify the effects of both exogenous and endogenous opioids on different basic functions in vertebrates and invertebrates. Possible mechanisms for the observed effects are discussed.

Analgesics, Opioid↗
PubMed1997

Effects of weak microwave fields amplitude modulated at ELF on EEG of symmetric brain areas in rats.

Averaged electroencephalogram (EEG) frequency spectra were studied in eight unanesthetized and unmyorelaxed adult male rats with chronically implanted carbon electrodes in symmetrical somesthetic areas when a weak (0.1-0.2 mW/cm) microwave (MW, 945 MHz) field, amplitude-modulated at extremely low frequency (ELF) (4 Hz), was applied. Intermittent (1 min "On," 1 min "Off") field exposure (10-min duration) was used. Hemispheric asymmetry in frequency spectra (averaged data for 10 or 1 min) of an ongoing EEG was characterized by a power decrease in the 1.5-3 Hz range on the left hemisphere and by a power decrease in the 10-14 and 20-30 Hz ranges on the right hemisphere. No differences between control and exposure experiments were shown under these routines of data averaging. Significant elevations of EEG asymmetry in 10-14 Hz range were observed during the first 20 s after four from five onsets of the MW field, when averaged spectra were obtained for every 10 s. Under neither control nor pre- and postexposure conditions was this effect observed. These results are discussed with respect to interaction of MW fields with the EEG generators.

Animals↗
PubMed1991

Effect of perfluorodecalin on activities of hepatic phase II xenobiotic biotransformation enzymes.

The activity of the hepatic phase II enzymes of xenobiotic biotransformation after intravenous administration of perfluorodecalin emulsion to rats was measured. Perfluorodecalin was found to increase the microsomal glutathione S-transferase and UDP-glucuronosyltransferase activities 1.4- and 2.3-fold, respectively. The activity of sulphotransferase was decreased 2-fold. These results show that perfluorodecalin is an inducer of both the enzymes of cytochrome P-450-dependent monooxygenase system [Mishin V. et al (1989) Chem.-Biol. Interactions, 72, 143-155.] and those catalyzing conjugation reactions: microsomal glutathione S-transferase and UDP-glucuronosyltransferase.

Animals↗
PubMed1991

[An electrophysiological study of the anti-arrhythmia effect of antioxidant ionol].

The paper describes the study of anti-arrhythmia effects of ionol. In isolated rabbit papillary muscle, ionol (a) had no effect on the depolarization-induced automaticity; (b) did not influence early afterdepolarizations: (c) delayed the onset of post-depolarizations initiated by Ca-overload and therefore inhibited the ectopic focal activity in myocardium. In isolated left auricles of rabbit, ionol suppressed the shortening of the excitation wavelength induced with adrenaline and thus protected the heart of reentry and consequent rhythm disturbances.

Animals↗
PubMed1991

[Effect of emulsions of carbon perfluoride compounds on the blood plasma complement system and functional state of the rabbit brain].

Experiments were conducted in vitro on rabbits to study the effect of emulsions based on composition of carbon perfluorides (decalin perfluoride/methyl cyclohexyl piperidine perfluoride) and proxanol (P-268) on the blood complement system. It is shown that despite preservation of the composition some emulsions activate complement others fail to do this. Intravenous infusion of complement-activating emulsion in a test-dose leads to early neutropenic reaction in the peripheral blood of rabbits and intensified power of low frequency rhythms in the electrocorticogram.

Animals↗
PubMed1991

[The effect of perfluordecaline on the activity of phase III xenobiotic transformation enzymes].

Injection of perfluorodecaline to rats caused an increase of the phase II xenobiotic biotransformation enzyme activities followed by cytochrome P-450 induction. The activities of liver microsomal UDP-glucuronosyl transferase and glutathione transferase increased by 130 and 40%, respectively, against the control level. The increase of the cytosolic glutathione transferase activity was insignificant In contrast, the activity of sulfotransferase decreased about 2-fold. The role of modification of xenobiotic biotransformation enzymes in the biological effect of perfluorodecaline is discussed.

Animals↗
PubMed1989

[The blocking action of platelet-activating factor (PAF) on the calcium currents of the atrial fibers in the frog and guinea pig].

The effects of platelet-activating factor (PAF) on the myocardial cell membrane Ca-current (ICa) and Ca-action potential (Ca-AP) were investigated. In double sucrose-gap voltage-clamped frog atrial trabeculae PAF (2 X 10(-7) M) reduced ICa-amplitude to 40-50%; at the same time the IK-amplitude was increased to the same value. These changes of ICa and IK amplitudes were protected by simultaneous action of PAF and PAF antagonist BN 52021 (4 X 10(-6) M). In the partially depolarized (K+0 = 15-20 mM) of the guinea pig myocardial auricles PAF decreased Ca-AP amplitude and Vmax of its upstroke and shortened the Ca-AP duration (intracellular microelectrodes) like the isometric tension responses. These effects were prevented by PAF antagonist U-66985. Histamine was also able to protect from the PAF-induced changes of Ca-AP and tension responses. Our data demonstrated both by direct and by indirect methods of ICa registration in myocardia membrane that PAF induces reversed blocking of ICa. Because the blocking effects of PAF on frog and guinea pig myocardium are identical, these results imply that the mechanisms of PAF action on cold- and warm-blooded animals are similar in principle. The coupling of ICa and IK changes confirm our earlier supposition that PAF-induced Ca-AP shorting can be explained by IK augmentation.

Animals↗
PubMed1988

The "pacemaker" function of the transient outward current in the rabbit myocardium.

The single sucrose gap technique was employed to study the electrically induced automaticity in rabbit papillary muscles. When the potential was clamped at the level of the "maximum diastolic potential" following the first spike of automaticity an initial decline of the outward ionic current with subsequent activation of the delayed potassium current was observed. The initial decline was potential-sensitive with a maximum at approximately -2 mV; it diminished when the rate of stimulation increased and was abolished with 4-aminopyridine plus Sr2+. It is suggested that the transient outward current determines the development of the "pacemaker potential" after the first spike of electrically induced automaticity in rabbit papillary muscles.

Action Potentials↗
PubMed1983

Transient outward current and rate dependence of action potential duration in rabbit cardiac ventricular muscle.

A conventional (single sucrose gap) voltage clamp technique was employed to investigate the rate dependence of ionic currents activated in the plateau range of potential in the rabbit ventricular muscle. A transient outward current of increasing amplitude was observed when the period of rest preceding the test voltage clamp pulse was increased from 0.7-60 s. The action potential duration was short when the transient outward current peak (100-150 ms after the voltage clamp pulse beginning) was high under the studied conditions of stimulation (interbeat intervals 0.7-60 s). The rate dependent transient outward current was small at low levels of depolarization above the resting potential (40 mV), had a maximum at some 90-100 mV and decreased at more positive potentials. This current was sensitive to the simultaneous application of 4-aminopyridine and calcium substitution with strontium in the Tyrode solution. It is suggested that the transient outward current is probably responsible for the changes of the action potential duration in rabbit papillary muscles when the interbeat interval varies from some 0.7-60 s.

4-Aminopyridine↗
PubMed1983

A study of the healing-over in the cardiac muscle using suction electrodes.

Suction electrodes were used to investigate the phenomenon of the healing-over in preparations of rabbit, cat and dog ventricular muscles. At least two processes were shown to participate in the process of the healing-over: a rapid one (time constant approximately 1 min) and a slow one (time constant approximately 10 min). Procion Yellow dye was used to determine the size of the injured zone under the suction electrode tip. Larger tips resulted in larger zones injured. The specific resistance of the border formed during the healing over was estimated to be in the range of approx. 1 k omega X cm2, i.e. much smaller than that of the intact surface membrane.

Action Potentials↗
PubMed1982

The prolongation of the action potential in mammalian ventricular muscle at rest. Is it due to intracellular calcium content changes.

The conventional microelectrode technique was used to investigate the effect of long periods of rest (greater than 10s) on the action potential duration of mammalian ventricular muscle. The action potential duration increased as the rest period increased. This prolongation of the action potential was the greatest and the slowest in rabbit ventricle, was smaller and more rapid in guinea-pig ventricle, and was practically absent in rat ventricle. The prolongation of the action potential at rest was suppressed with aminazine and strophanthin. Low sodium concentration, lanthanum ions, ruthenium red and acidosis failed to suppress the slow prolongation. It is concluded that the slow prolongation of the action potential at rest is related to changes in the intracellular calcium content induced by a mechanism different from Na/Ca exchange.

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↗
PubMedDate not supplied

[Slow excitation waves and mechanisms of polymorphic ventricular tachycardia in an experimental model: isolated walls of the right ventricle from rabbit and squirrel].

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 mathematically derived from electrograms registered simultaneously at 32 endocardial and 32 epicardial points. The same electrograms allow one to visualize the excitation wave propagation along each of the preparation surfaces. The comparison of excitation wave pictures and corresponding pseudoECGs enabled us to reveal the conditions necessary and sufficient for polymorphism in heart rhythm disturbances. Polymorphic arrhythmias are due to changes in wave pictures in the regions of retarded excitation propagation.

Animals↗
PubMedDate not supplied

[Dicrete zones of electrical connection between Purkinje terminals and muscle fibers in dog ventricles].

Activity of Purkinje terminals (P) and neighbouring muscle (M) fibres (P -- M-pairs) in various regions of dog's right ventricle was recorded. It has been shown that transmission of stimulation from P-to M-fibres is abserved not over all endocardial surface, rather in descrete sites -- zones of P--M-interaction. The zones ellips like with the axes 300X100 micron, they are located relatively far from one another -- at the distance of 800-2000 microns. The total area of the zones equals 5% of endocardial surface. P-M delay is less within the zone of connection of P--M-fibres (4 msec) and greater outside the zone (up to 10 msec).

Action Potentials↗
PubMedDate not supplied

[Evoked automatism (repeated responses) of cat cardiac ventricular fibers].

Repeated responses (RR) of cat papillary muscle fibres have been studied. Threshold current of the occurrence of repeated responses (2t) and saturation current (Is) on the accomodation curve have been determined. Two zones of autooscillations were revealed according to the ratio brage from low levels of the membrane potential (-80 divided by -55 mv). The second RR zone (It is not equal to Is) was activated in more than 70 per cent of preparations in the average from higher levels of the membrane potential (-40 mv and higher). A comparison was carried out between muscle and specialized fibres RR. The experimental data were analysed by the method of phase plane.

Animals↗
PubMedDate not supplied

[Anisotropy of stationary rates and delays in extrasystolic waves in the dog heart].

Excitation propagation in the ventricle and auricle bands of the dog's myocardium has been studied. The anisotropy of stationary valocities and delays of the initiation of extrasistole exciation has been shown: along the fibres the velocity is higher and the delay smaller than across the fibres. The levels of anisotropy of velocities and delays are almost equal in each structure. The strongest anisotropy of delays and velocities (-4,5) is observed in the ventricle muscle layer; the weakest (1,7)-in a specialized layer. The anisotropy of velocities and delays is the greater, the greater is the electrotone anisotropy. A new mechanism of extrasistole initiation (reentry) in the system homogenous by the membrane properties, but with anisotropy of intercellular bonds is considered.

Animals↗
PubMedDate not supplied

[Role of entering currents in the accommodation of myocardial fibers].

Varying ionic composition of outher medium and applying specific agents the role of fast and slow systems of entering currents in the accommodation of cats ventricular fibres has been studied. In potential region close to the level of resting potential (membrane depolarization no larger than 20-30mv), accomodation mainly depends on fast sodium currents. It is inhibited with a rise of this current (akonitin 0.1--1 mg) and, on the contrary, it increases when it gets weaker (novacain 2--5 mM). In the region of more positive potentials (membrane depolarization more than by 30 mv) the accommodation is mainly determined by the slow NA--Ca-systems of channels. The agents which strengthen NA--Ca--current (Si2+--5mM, Ca2+--10mM, Ba2+--0.1 mM) reduce the accommodation in the activation region of the Na--Ca--system. The agents which weaken the slow current (Mn2+--3 mM, isoptin--2+5 mg/l, inderal--2 mg/l) produce an opposite effect.

Aconitine↗