Correlation between electrical activity in symmetrical regions of the cerebral cortex and unilateral lesions]

Functional interrelations between cerebral hemispheres, and particularly, between their symmetrical areas, were studied during compensatory processes in patients with tumours localized in one of the hemispheres. Analysis of spontaneous electrical activity before the operation on the tumour revealed several types of interhemispheric relations. The existence of a sharply pronounced pathological activity in one hemisphere, testifying to inactivation of cortical cells, is, as a rule, accompanied by activation in the intact hemisphere, especially in the areas symmetrical with those injured. In cases of less pronounced pathology, with partial retention of activity of the cortical cells in the injured areas of the affected hemisphere, a lesser degree of activation is observed in the intact hemisphere. The data point to a development of substituting-compensatory processes in the areas of the intact hemisphere symmetrical with the injured ones and to the possibility of testing the processes electrophysiologically.     

Carbon monoxide affects electrical and contractile activity of rat myocardium

Background

Carbon monoxide (CO) is a toxic gas, which also acts in the organism as a neurotransmitter. It is generated as a by-product of heme breakdown catalyzed by heme oxygenase. We have investigated changes in electrical and contractile activity of isolated rat atrial and ventricular myocardium preparations under the influence of CO.

Methods

Standard microelectrode technique was used for intracellular registration of electrical activity in isolated preparations of atrial and ventricular myocardium. Contractions of atrial myocardial stripes were registered via force transducer.

Results

CO (10^-4 - 10^-3 M) caused prominent decrease of action potential duration (APD) in working atrial myocardium as well as significant acceleration of sinus rhythm. In addition CO reduced force of contractions and other parameters of contractile activity. Inhibitor of heme oxygenase zinc protoporphyrin IX exerts opposite effects: prolongation of action potential, reduction of sinus rhythm rate and enhancement of contractile function. Therefore, endogenous CO, which may be generated in the heart due to the presence of active heme oxygenase, is likely to exert the same effects as exogenous CO applied to the perfusing medium. In ventricular myocardium preparations exogenous CO also induced shortening of action potential, while zinc protoporphyrin IX produced the opposite effect.

Conclusions

Thus, endogenous or exogenous carbon monoxide may act as an important regulator of electrical and contractile cardiac activity.     

Effect of lysosomal enzymes on myocardial electrical and contractile activity in burn shock

Marked depression of the amplitude of isometric contractions of myocardial preparations, which was induced by lysosomal enzymes from the liver of control animals, was demonstrated in isolated rabbit papillary muscles. The decrease of contractility was not accompanied by remarkable changes in the amplitude or in the duration of intracellular action potentials. The negative inotropic action of lysosomal enzymes was similar to that of blood plasma of the burnt animals. Based on the appearance and subsequent activation of lysosomal enzymes in blood of the animals by the 20th to 60th min after thermal injury it is suggested that lysosomal enzymes might be one of factors that depress myocardial contractility in burn shock.     

A spectral-correlational analysis of the electrical activity of the sensorimotor cortex and the internal geniculate body during a motor-polarization dominant]

By spectral-correlative analysis the dynamics was studied of structural changes of coherent relations of the electrical activity of the sensorimotor cortex and medial geniculate body (MGB) of the rabbit under motor polarization dominant created by the action of DC anode on the sensorimotor cortex area. It was shown, that in the power spectra of the MGB, besides the increase of the delta-region components in interstimulus intervals at the dominant, during the action of the sound stimulus a distinct maximum appeared in the alpha-rhythm range of the electrical activity of MGB of the "dominant" hemisphere. The coherence increase of the delta-range of the MGB and the sensorimotor cortex electrical activity in the "dominant" part of the brain was manifested exclusively in the period of sound stimulus action.     

Participation of the contractile activity of the skeletal musculature in systemic circulatory reactions to orthostatic action]

Under orthostatic test (OT) the elimination of the skeletal muscle contractile activity with a myorelaxant sharply elevated the initial hypotension and decreased considerably the compensatory restoration of the arterial pressure (AP) in anesthetized cats. Reaction of the cardiac output in OT changed insignificantly. The AP elevation synchronous with the motor reactions, eliminated by the myorelaxant, was observed. As revealed by the method of artificial circulation (bypass of the left ventricle), the compensatory vasoconstriction of the resistance vessels was eliminated by the myorelaxant under OT. In some experiments myorelaxation evoked a significant elevation of the blood pooling in the capacitance vessels.     

Effect of staphylococcal toxin and antistaphylococcal gamma-globulin on the electrical and contractile activity of the guinea pig myocardium

A study was made of the action of staphylococcal toxin (ST) and its combination with antistaphylococcal gamma-globulin (ASGG) on intracellular potentials (rest potential--RP, and action potential--AP), and isometric contractions of guinea-pig auricle. ST (initial concentration 18.10(-2)Lh) diluted with normal Tyrode's solution at 1:1000, 1:100 and 1:10 (spontaneously active preparations), and Tyrode's solution with 13.5 mM KCl (evoked activity of preparations), significantly increased the duration of AP of myocardial cells. In evoked activity of preparations, RP and the amplitude of AP declined as the concentration of ST was raised. The amplitude of isometric contractions and maximal rates of their growth and fall increased under the effect of ST (1:1000) and decreased at 1:100 and 1:10. ASGG combined with ST (1:100) did not produce any protective effect on the myocardium. On the contrary, it provoked a still greater inhibition of contractility. The inhibitory action of combined ST and ASGG was seen at all ratios of ST to ASGG (use was made of ASGG shortage, equivalent amount and excess as regards ST) and reached 50% for all study characteristics of contractility. Anatoxin (inactivated toxin) combined with ASGG also produced a cardiodepressant action which was manifested in an approximately 50% decrease in the maximal rate of the growth and fall of contractions in the absence of significant changes in the contraction amplitude.     

Acetate-induced depression of electrical and contractile activity in normoxic and hypoxic guinea pig papillary muscle

The action potential configuration, developed tension, and resting tension were monitored in normoxic and hypoxic guinea pig papillary muscles superfused with solutions containing no substrate, glucose, or acetate (1-10 mM). In normoxic muscle, acetate provoked a concentration-dependent transient depression of the action potential duration and force of contraction, depression was maximal after 10-30 min, and recovery was complete after 90-120 min. In hypoxic muscle, acetate accelerated functional rundown (action potential shortening, decline of developed tension, increase in resting tension). Because rundown in hypoxic muscle was sensitive to factors affecting glycolysis (moderated by external glucose; accentuated by 2-deoxyglucose), the accentuated rundown with acetate may be accounted for by a partial block of glycolysis. However, block of glycolysis cannot explain the acetate-induced transient depression in normoxic muscle, since the depression was enhanced in normoxic muscle with 2-deoxyglucose-blocked glycolysis. We suggest that the transient depression is due to a transient depression of high energy nucleotides with consequent effects on ionic currents.     

Effect of noradrenaline on the electrical and contractile properties of smooth muscle cells in the pulmonary artery]

Experiments were performed on the smooth muscle cells of rabbit a. pulmonalis using the microelectrode technique. No spontaneous electrical or mechanical activity was recorded in normal Krebs solution. The current-voltage relation in these smooth muscle cells showed marked rectification. No changes in the isometric tension were observed due to the anodal or cathodal stimulating currents. Strong depolarization of the muscle cells produced only local potentials on the cathelectrotone which never developed into a spike. Noradrenaline (10(-8) g/ml) caused depolarization of the 5-7 mV in the muscle cell membrane and a considerable contraction of the muscle strip as well. Under such conditions the contractile apparatus of the muscle cells became sensible to the resting potential level. Anodal stimulation was accompanied by relaxation of the muscle strip, whereas cathodal stimulation--by its contraction. The alpha-adrenoblocking agent (phentolamine) blocked the effect of noradrenaline evidencing the fact that noradrenaline exerted its excitatory action on the smooth muscle cells of the a. pulmonalis through the alpha-adrenoreceptors.     

Effect of serotonin and histamine on the cellular contractile activity of the internal carotid artery]

In the experiments on isolated segments of the canine internal carotid artery it was shown that serotonin (5.10(-11)--5.10(-5) g/ml) activated the contractions. Histamine (5.10(-9) g/ml) induced dilation of isolated segments and its higher concentrations produced the contractile responses. Serotonin and histamine were shown to induce the contractions of the depolarized smooth vascular muscle. It is suggested that serotonin activates the inflow of extracellular calcium ions and histamine activates both the inflow of extracellular and the cut-flow of the intracellular calcium ions.     

Hemispheric asymetry of the evoked electrical activity of the cerebral cortex to letter and non-verbal stimuli]

Average evoked potentials (AEP) were recorded in practically healthy subjects to "meaningless" figures and letters, presented to different halves of the visual field. Analysis of the amplitudes of AEP late components to verbal and non-verbal stimuli reveals hemispheric asymmetry. A higher amplitude of the late positive evoked response (P300) to a "direct" stimulation both by verbal and non-verbal stimuli (in the contralateral field of vision) is recorded in the left hemisphere than in the right one. Similar stimulation of the right hemisphere does not reveal sucha difference. In the left hemisphere the P300 wave is of a clearly greater amplitude to a "direct" stimulation (contralateral visual field) than to an "indirect" one (ipsilateral visual field), regardless of the nature of the stimulus. No such difference is observed in the right hemisphere. The magnitude of the late negative wave (component N200) to non-verbal stimuli is greater in the right hemisphere both in response to "direct" and "indirect" stimulations. No intrahemispheric difference has been found in the amplitude of late evoked responses of the cerebral cortex to verbal and non-verbal stimuli.     

Stress-induced inhibition of the ileal, caecal, and colonic contractile activity in rabbits]

In alert rabbits, immobilisation stress decreased the spike burst rate and amplitude in ileum, caecum, and colon for 20 min. Following beta-adrenoceptor blockade, the contractile activity suppression was aggravated. The stress seems to lead to suppression of the ileal, caecal, and colonic contractile activity for up to 40 min which is unrelated to adrenergic inhibition of the smooth muscle activity mediated by beta-adrenoceptors.