[Electrical activity and circulatory effects of nitrite in the rat cerebrum].

An association between the cerebrum electrical activity (CEA) in rats, blood supply of its cortex microregions (linear blood flow), and general cerebrum blood flow under acute nitrite hypoxia was studied. The phase character of the change in hemodynamic indices and the total capacity of electroencephalography (EEG) spectrum for 75 min after sodium nitrite introduction (30 mg/kg of body weight) was detected. The first phase (30 min) was associated with cerebrum adaptation to hypotension caused by nitrite and was completed by EEG normalization. The second phase was characterized by pathological EEG changes (in spite of restoration of hemodynamics in the cerebrum) caused by the growth of oxygen debt in the nervous tissue as a result of a decrease in the blood oxygen capacity by 60-75 min of the effect of nitrite.

[Myocardial electrogenesis in laboratory rats under conditions of acute nitrite intoxication].

In anesthetized male rats the arterial blood pressure in femoral artery and electrocardiogram in standard leads were recorded uninterruptedly for 1-1.5 h under conditions of acute nitrite intoxication produced by a subcutaneous injection of water solution of sodium nitrite (donor of nitric oxide) at concentrations of 10, 30, and 50 mg/kg body mass. Results of the study have shown dose-dependent changes of arterial pressure as well as of time and amplitude characteristics of electrocardiogram under effect of NaNO2. At the threshold hypoxic dose, an increase of amplitude of R and S waves was observed by the 30-45th min, while at the maximal NaNO2 dose, amplitude of all waves rose by the 15th min of intoxication. High nitric doses often caused an increase of the ST segment above the isoelectric line and a rise of the amplitude of the T wave, on which a notch appeared in some cases. The change of the ECG time parameters was expressed in the dose-dependent development of bradycardia for the first 4-7 min; its level correlated with the progressively decreasing arterial pressure in the beginning (the 2-4th min) of nitrite intoxication. Variation analysis of heart rate spectral characteristics by Baevskii has revealed a rise of the total spectral power of pulse oscillations. Under effect of nitrite, in the spectrum of cardiointervals, quent recovery of the normal ECG spectrum in the end of the experimental period. The maximal nitrite dose produced more pronounced shifts of the heart rate spectrum towards the LF and VLF diapasons that were not restored for 1 h of experiment. Transitory processes of readjustment of the cardiac rhythm had discrete character. The nitrite dose of 50 mg/kg body mass increased the RR-interval after 4-7 min with amplitude steps of 3-5 imp/s and the time constant of 20-40 s. The revealed ECG changes had the reflex (enhancement of parasympathetic tonus) and metabolic (the hypoxic and histotoxic damage of myocardium) nature.

[Effect of nitrite-induced methemoglobinemia on the kinetics of blood deoxygenation].

Kinetics of blood deoxygenation was studied during acute hypoxia induced by subcutaneous administration of sodium nitrite using polarographic method. Plasma oxygen tension remained unaltered as the dose of sodium nitrite increased, while the dynamics of oxygen release was dose-dependent. The constant of oxyhemoglobin deoxygenation rate proved to vary with blood deoxygenation. The nitrite-induced deceleration of oxyhemoglobin deoxygenation was due to the inactivation of a fraction of hemoglobin as well as to the increased hemoglobin oxygen affinity and possible changes in the oxygen permeability of erythrocyte membranes during acute methemoglobinemia.

[Bioelectrical reactions on the surface of the mamma in the goat]. / Bioélektricheskie reaktsii na poverkhnosti molochnoi zhelezy kozy.

Spontaneous and evoked biopotentials were recorded on the mammary gland surface in goats. The biopotentials appear in the course of secretion during milk ejection as well as under electrical, mechanical and hormonal actions. They might be considered as adequate indices of secretion and ejection processes in the mammary gland.

[The comparative characteristics of the heart rhythm in cetaceans]. / Sravnitel'naia kharakteristika serdechnogo ritma u kitoobraznykh.

In Amazon River dolphins, bottle-nosed dolphins and white whales, comparative studies have been made on cardiac electrical activity using electrocardiographic and telemetric techniques. In all the species investigated, certain dependence of cardiac cycle duration on the phase of respiratory pause was observed. A pronounced bradycardia was noted in diving animals which reflects the level of their adaptation to hypoxia and hypoxemia. Autocorrelation functions of the dynamic sequences of cardiac intervals were calculated. The presence of "slow" waves in cardiac cycle was shown which were considerably increased during diving.