Biomedical subjects
Publications and source records attributed to G I Kositskiĭ.
Acute experiments on cats have shown that the naloxone blocks of opiate receptors increased essentially the incidence of idioventricular arrhythmias in myocardial ischemia. These results may evidence of the endogenous opioid peptides involvement in the body response on the acute myocardial ischemia.
The effects of cordanum and propranolol on the coronary resistance were studied in isolated cat hearts. The infusion of cordanum and propranolol may be followed by both reduction or enlargement of the coronary resistance. The alterations of the coronary resistance are in most cases parallel with the weakening of the isolated heart function. In some cases cordanum infusion is followed by a short-term reduction in the coronary resistance, which precedes the alteration of the heart function and thus may be due to direct cordanum effect on the coronary vessels.
Acute experiments on cats anesthetized with nembutal, using a microelectrode technique, have demonstrated that pinching of the coronary artery involves changes in the patterns of impulse activity in all types of bulbar respiratory neurons, up to the appearance of ischemic shifts on the ECG. Progression of myocardial ischemia is paralleled by changes in all the bulbar respiratory neurons.
Possibilities of reversed cerebral circulation, with arterial blood coming to cerebral tissue through the venous network and venous blood going through the arteries, were examined in acute and chronic experiments in dogs. Arterial blood pressure in cephalic veins reached 70-120 mm Hg, venous blood pressure in the circle of Willis was 5-35 mm Hg. Liquor pressure was never beyond 20-35 mm Hg. The EEG and reflex responses of the cerebral trunk were maintained for scores of minutes under acute experiment. Animals, surviving after prolonged arterialization of the cerebral venous network in chronic experiments (3-4 days), showed no central nervous or behavior disorders.
The possibility of reverse perfusion of the brain (in which arterial blood flows to brain tissues through venous vessels, and venous blood is drained by the arteries) was studied in acute and chronic experiments on dogs. Blood pressure in cerebral veins could reach 90--120 mm Hg, in Willisii arteries it was 5--35 mm Hg. Liquor pressure reached 20--35 mmHg. After temporary arterialization of the brain venous system (10, 30 and 60 min) the animals survived without impairment of the brain function and behaviour. In the future reverse perfusion of the brain (in which blood pressure in the arteries falls to the level of venous pressure) could be used as a means of urgent surgical intervention in cases of threatened or beginning intracranial arterial hemorrhage.
The experiments performed on rabbits have shown that with the inhalation of various gas mixtures the impulse activity of cardiovascular neurons in bulbar cardiovascular centre is changed. The most active are inserted cardiovascular neurons that are highly sensitive to O2 shortage and CO2 excess. It is believed that the experiments on Hering nerve severing indicate the possible development of reflex effects on hemodynamics during changes in inhaled gas composition produced from sinocarotid reflexogenic zone not only through bulbar respiratory neurons, but also through a system of inserted neurons of bulbar cardiovascular centre.
The dependence of ornithine decarboxylase (ODC) activity on hydra peptide morphogen doses has been established. The parameters of protein synthesis were determined in normal and regenerating rat liver, using the peptide in a dose of 20 micrograms/kg body weight, initiating maximum enzyme activity. It was established that intraperitoneal injection of the peptide in partially hepatectomized animals stimulated ODS activity in dose-dependent manner and was dome-shaped. The peptide injection in intact animals does not affect the intensity of 3H-leucine inclusion into the liver protein and the protein content in rat liver. However, the peptide injection in partially hepatectomized animals increased the level of 3H-leucine inclusion into the protein of regenerating liver and stimulated protein accumulation in this type of tissue.
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The effects of phentolamine on coronary resistance and heart rate, as well as the influence of beta 1-adrenoceptor blockade on phentolamine effects were studied on the isolated cat hearts. Phentolamine reduced coronary resistance in 100% of cases (-25.9 +/- 4.4%; p less than 0.001) and increased heart rate only in 31.6% of cases (+9.1 +/- 1.4%); on average the alterations of heart rate were nonsignificant (p less than 0.1). After beta 1-blockade with Cordanum the rate of coronary dilation reduced (p less than 0.001), the changes in coronary resistance being nonsignificant (p greater than 0.1). Basal coronary resistance and tone during phentolamine infusion without or after beta 1-blockade were identical (p greater than 0.1). Thus, the reduction of coronary resistance during phentolamine infusion was due to beta 1-adrenomimetic activity of the drug.
The activity of afferent and internuncial neurons of the bulbar cardiovascular centre (BCVC) was evaluated, using microelectrodes, in conditions of serotonin microinjections, altered blood gas composition and sensomotor cortical stimulation, in acute experiments in cats and rabbits. The afferent flow from ischemized myocardium was examined at the level of nodular-ganglion neurons. Cortical stimulation, changed blood O2 and CO2 proportions and the afferent message related to impaired coronary flow are shown to affect primarily the activity of internuncial BCVC neurons. Myocardial ischemia is shown to be much more frequently complicated by idioventricular arrhythmias, including ventricular fibrillations, under sensomotor cortical stimulation. Disintegrated operation of the afferent and internuncial BCVC neurons that precedes the development of severe ischemic arrhythmias may be due to a heavier afferent flow from heart receptors, descending influences from the cortical sensomotor area, and altered blood gas composition and a lower serotonin level in the medulla oblongata, associated with myocardial ischemia.
In acute experiments on cats performed under nembutal anesthesia the stimulation of sensorimotor zone in cerebral hemisphere cortex changed the impulse activity of interneurons of bulbar cardiovascular centre and not of the afferent neurons. The analysis of the activity of afferent neurons and interneurons has shown a decrease in coordination between the reaction of these cells to the development of ischemic myocardial lesions during the cortex stimulation. In these conditions bulbar cardiovascular neurons could both increase and decrease the impulse activity. These changes seem to be the reason for the growing incidence of idioventricular ischemic arrhythmias during cortical stimulation.
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The hypothesis of neuropeptides involvement in intercellular interaction was checked on the neurons VD1 and RPD2 connected with electrotonic synapse with two-way transmission in nerve ganglia of the pond snail. The preparation was perfused with natural and synthetic fragments of ACTH (2 X 10(-7) M). In perfusion with ACTH4-10 solution, synapse became rectified whereas in ACTH4-7 and ACTH5-10 solutions it obtained partially rectified properties. After exposure to ACTH4-7--Pro--Gly--Pro, synapse obtained rectifying properties with one--way increase in conductivity following temporary two-way increase of transmission efficiency. With the use of Pro--Gly--Pro--ACTH4-7--Pro--Gly--Pro, inhibition of the two--way conductivity occurred. Neuropeptides seem to modulate synaptic transmission. Impulse priority depends on the initial level of the cell MPs and is purposefully modulated by the peptides under test.
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The authors studied the anabolic effect of peptide morphogen of the hydra undecapeptide on normal and regenerating rat liver. Ornithine decarboxylase (EC 4.1.1.17) activity served as a marker. Intraperitoneal injection of the peptide into intact animals stimulated ornithine decarboxylase activity in a dose-dependent manner. In partially hepatectomized rats the peptide stimulated ornithine decarboxylase activity in the dose of 20 micrograms/kg body weight while greater doses inhibited the enzyme activity.
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Standard microelectrode techniques were used to study the impulse activity of different types of nodosal ganglion neurons. Differences in electrical activity of cardiovascular neurons were observed in myocardial ischemia both complicated and not complicated by fibrillation. In these conditions rhythmic activity of cardiopulmonary, late inspiratory and inspiratory-expiratory neurons is quite similar.