Biomedical subjects
Publications and source records attributed to A S Shevchenko.
In lymphocytes of sheep exposed to 52 and 103 mC/kg radiation revealed was an increase in spontaneous incorporation of 3H-thymidine into DNA. A change in spontaneous DNA-synthesizing activity in lymphocytes of exposed animals was accompanied by the increase in the total protein content of the peripheral blood lymphocytes.
The immunoreactive calmodulin content was shown to increase in the irradiated platelets of rats and cows. Total Ca content did not vary significantly in platelets of exposed animals although there was a tendency toward its increase. At the same time, total Ca content in lymphocytes of irradiated cows increased while the immunoreactive calmodulin level remained unchanged.
Changes in basal and prostaglandin stimulated activity of adenylate cyclase in lymphocytes and platelets of irradiated sheep are phasic. In platelets adenylate cyclase activity is maximum on days 5 and 10 following irradiation, whereas in lymphocytes the enzyme activity is maximum on day 7. cAMP phosphodiesterase activity is slightly changed in platelets and increased in lymphocytes of exposed sheep.
Enhancing stimulation effect of prostaglandin E1 on adenylate cyclase, decrease in basal activity of adenylate cyclase in platelets and reducing thyroxine concentration in cow plasma 5 years after radioiodine damage to thyroid gland with doses higher than 200 Gy were detected, whereas only decrease in adenylate cyclase activity in platelets from animals irradiated with 40 Gy to thyroid gland was observed. No changes in platelet adenylate cyclase in cows exposed to less than 1 Gy to thyroid gland after 5 years of maintenance on the territory with 137Cs contamination density lower than 0.37 MBq/m2 were found.
It was found that the total Ca content in erythrocytes from irradiated sheep and horses increased by 10-40% from 1st till 5th days after irradiation, the intracellular Mg content being unchanged. More than 2-fold increase in total Ca content in lymphocytes during first 15 days was revealed, while in platelets only a trend for a growth in acute period of radiation disease was detected. On the contrary, no reliable changes in total Ca content in plasma after irradiation were observed. This fact indicates that Ca accumulation in blood cells after whole-body irradiation is due to disturbance in intracellular Ca(2+)-homeostasis.
Increasing of Ca2+ concentration in cytoplasm and of the rate of 45Ca iflux into cows erythrocytes in 19-24 month after Chernobyl accident was revealed. Correlation between Ca2+ concentration in cytoplasm of erythrocytes and thyroxin content in plasma of cows with radioiodine damage of thyroid gland was found. Reduction of the rate of 45Ga influx into erythrocytes in cows with radiation doses of 20-60 By on thyroid gland was shown in later time after accident (3-5 years). Changes in Ca2+ permeability through membranes of erythrocytes and neutrophils after injection of 131I into calves in doses of 300 Gy and more on thyroid gland was found.
The indices of lipid peroxidation and the contents of alpha-tocopherol and retinol in the blood plasma of sheep exposed to repeated gamma irradiations were studied. It was shown that a repeated acute gamma irradiation of sheep with sublethal and lethal doses after 9 months of chronic low-dose gamma irradiation adversely affected the activity of the lipid free-radical oxidation. A radiologic pathology in the repeatedly irradiated animals developed as a decrease in the intensity of spontaneous chemiluminescence. Also, a tendency to an increase in the concentration of malonic dialdehyde was observed along with weak changes in the contents of triene and diene conjugates and the levels of alpha-tocopherol and retinol.
Parameters of the Ca2+ permeability (the 45Ca influx rate in the presence of orthovanadate blocking the Ca(2+)-ATPhase, and the initial rate of the 45Ca uptake) and the DNA fragmentation were determined in rat thymocytes after gamma-irradiation-induced (with a dose of 5 Gy) apoptosis. Within the first 30-90 min after irradiation, the 45Ca influx rate that is characteristic of the membrane passive permeability remained unchanged. The initial rate of the 45Ca uptake that is characteristic of the Ca2+ exchange almost doubled. In 90-180 min, the rate of the 45Ca influx in the irradiated cells increased 1.5 to 2.0 times. An increase in the DNA fragmentation was observed in 90-120 min after irradiation of thymocytes; in 3 h, it developed up to 50%. Thus, modification of the membrane Ca2+ permeability in the irradiated thymocytes precedes a stage of initiation of the DNA degradation. A degree of disturbance of the membrane passive permeability increases as the thymocyte apoptosis progresses. The obtained data suggest that disturbance of the passive Ca2+ permeability and the intracellular Ca2+ homeostasis are responsible for the apoptosis of lethally irradiated thymocytes.
The parameters of Ca(2+)-permeability (rate of Ca2+ influx in the presence of Ca(2+)-ATPase blocker vanadate and initial rate of Ca2+ uptake) were determined in the rat thymocytes after induction of apoptosis in vitro by gamma (gamma-irradiation at 5 Gy. There were no changes in the rate of Ca(2+)-influx within 30 to 909 min after irradiation, thus suggesting passive membrane permeability, while the initial rate of Ca(2+)-uptake, which characterizes Ca(2+)-exchange, approximately doubled in the irradiated cells. Thereafter, the initial rate of Ca(2+)-uptake in the intact and irradiated thymocytes became equal, while the rate of Ca(2+)-influx in the irradiated cells increased reliably 1.5-2 times within 90-180 min. Modification of membrane permeability for Ca2+ in the irradiated thymocytes precedes initiation of DNA degradation, and passive permeability is increasingly disturbed as apoptosis progresses. These data suggest that disturbances in Ca2+ passive permeability and intracellular Ca2+ homeostasis are an apoptosis trigger in lethally irradiated thymocytes.