Biomedical subjects
Publications and source records attributed to D D Matsievskii.
Acute experiments on narcotized rats showed that intravenous infusion of GABA derivative lithium hydroxybutyrate induced different changes in hemodynamic and respiratory parameters in animals with high and low resistance to hypoxia. Rats highly resistant to hypoxia better tolerated lithium hydroxybutyrate treatment compared to low resistant animals.
We compared the effects of a pyrrolidone-pyroglutamic acid composition and nimodipine on blood circulation in the middle cerebral artery in rats. The composition produced a strong effect on blood supply to the brain, stimulated blood flow in the middle cerebral artery (by 60 +/- 9%) and decreased blood pressure (by 25.0 +/- 2.7%). The cerebrovascular effects of this composition differed from those of nimodipine. Nimodipine not only increased middle cerebral artery blood flow, but also decreased cerebral blood flow in the early period after treatment.
Experiments employing ultrasound technique showed that nonselective blockade of central muscarinic cholinoceptors with amizyl significantly increases the number and lifespan of rats highly resistant to acute massive blood loss. This pretreatment increased individual resistance of the circulatory system to posthemorrhagic hypoxia (blood pressure and portal blood flow rate). Preliminary blockade of central nicotinic cholinoceptors and peripheral muscarinic cholinoceptors with cyclodol and methacin, respectively, had no effect on the percentage of rats highly and low resistant to acute blood loss. Preliminary blockade of peripheral muscarinic cholinoceptors with methacin prevented the decrease in the cardiac output in low resistant animals during the posthemorrhagic period.
Ultrasound blood flow transducers were tested by using pulsating flows in a dynamic test system with Pito tube. Simultaneous studies of rat ascending aorta with a Doppler strip detector (13 MHz) and ultrasound catheter (33 MHz) produced a 10% discrepancy of the results. Here we describe a computing unit to estimate the volume flow rate in biomicroscopic studies. The value of blood flow rate estimated with a 38.5-MHz Doppler probe and diameter of the microscopically examined vessel were inputted into a computer for real-time processing. Blood flow rate in microvessels of rat mesentery and cremaster muscle was 10-700 nl/sec.
Effects of acute hypoxia on hemodynamics and respiration were studied in acute experiments on narcotized rats. The animals were divided into groups characterized by high, low-, and medium- resistance to hypoxia by the time of respiration arrest during inhalation of gas mixture containing 3% O2. Hemodynamic parameters of highly resistant animals were higher than in low-resistant rats throughout the entire hypoxic period. The development of a rare (with prolonged inspiratory phase) respiratory rhythm in highly resistant rats is an adaptive reaction, which allows them longer tolerate hypoxia compared to low-resistant animals.
Peculiarities of application of two modes of ultrasonic measurements of blood flow in experimental research are considered, which are based on Doppler effect and on differential transit-time of upstream and downstream sound propagation. The efficiency of high-frequency ultrasound flowmeter equipped with 26.8 MHz transducers was demonstrated in measurements of blood flow in rat midbrain and coronary arteries. This approach can be used for evaluation of the dynamics of cardiac output with an intravascular catheter 0.6 mm in diameter working at 33 MHz. The probe and electronic scheme of the devise for measuring blood flow in microvessels are described. Blood flow rate measured in mesentery and m. cremaster arterioles under normal conditions was 2-12 mm/sec. One-element probe working at 38.5 MHz provided stable recording of blood microflows in 30-40-micro vessels.
Acute experiments on cats showed that mild hypoxia did not disturb the balance between right and left ventricular outputs. Breaching 3% O(2) shifted this balance by reducing right ventricular output in cats with low resistance to hypoxia. Spontaneous breathing hypercapnic gas mixtures shifted this balance towards the left ventricular output. During artificial ventilation under open chest conditions, hypercapnia induced opposite changes and shifted the balance towards the right ventricular output.
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