Biomedical subjects
Publications and source records attributed to A Vacek.
The temperature of the rat's gingiva was 30.4 +/- 0.3 degrees C. before, and 37.1 +/- 0.2 degrees C. after irrigation. After irrigation, the oxygen tension in the gingiva of the rats was by 40% higher than its original value. When pure oxygen was inhaled, the tension increased by 120% before irrigation, and by 126% after irrigation.
A protective effect of the mixture of radioprotectors (mexamine and cystamine) on the haematopoietic stem cells of the spleen and bone marrow was studied in mice irradiated by a dose 700 R in different time intervals after intraperitoneal injections of the substances. The protective effect of the mixture against the lethal radiation effects outlasts till the 90th minute after the injection, as well as the protection of the haematopoietic stem cells in the bone marrow. D0 of the regression lines of the survival of endogenous colonies in the spleen (ESC) increases up to 340 R after irradiating the mice in the 15 min interval after the injection of the protective substances with a subsequent decrease to the level of the control group (100 R). The D0 values of CFU survival in the bone marrow does not change; however, in the interval up to 60 min after the injection complete reparation of the radiation damage takes place after an exposure to 100 R. The recovery from the damage to the erythropoiesis followed by an incorporation of 59Fe into the bone marrow and spleen is the faster the higher a number of CFU survived the used radiation dose. The importance of a decrease of the radiation damage to the small intestine for the total protective effect of the mixture of radioprotectors is discussed.
Mice of three different strains were classified according to the percentage of survival after a whole-body exposure of 600R as radioresistant (strain C57BL/10), radiosensitive (strain BALB/c) and intermediate (strain BFU). Haemopoietic recovery after a whole-body exposure of 200R was followed in the three groups. It was found that the radiosensitivity of bone marrow and spleen haemopoietic stem cells was equal in all the mouse strains tested. The extent of radiation damage to haemopoiesis, assessed by the changes in nucleated cell counts in bone marrow and spleen, as well as by bone marrow and spleen 59Fe uptake, was smaller and the rate of recovery higher in strain C57BL/10 than in strains BALB/c or BFU. An analogical difference among the strains was also observed during realimentation in the recovery of bone marrow and spleen haemopoiesis inhibited by fasting. The role of the capacity of haemopoietic cell population to repair the induqed haemopoietic damage is discussed and its decrease in BALB/c mice is held responsible for their higher radiosensitivity.
The frequency of exogenous haemopoietic spleen colonies in whole-body irradiated rats, aged 4--5 weeks, was found to be linearly dependent upon the dose of inoculated bone marrow or spleen nucleated cells. The recovery rate of the number of haemopoietic stem cells in rats exposed to 300R assessed on day 12 postirradiation was found to be faster in bone marrow than in spleen.
Experiments on non-inbred H-strain male mice confirmed that their radioresistance could be increased by a stimulatory action of the thyroid hormones applied for three weeks preceding the radiation exposure. It was found that the 30-day survival after 750R rose between the 1st and the 5th day after the end of the pretreatment. The highest degree of radioresistance was observed, when the radiation exposure fell into the phase of gradual receding of increased metabolic rate. The relevant experimental groups showed a higher frequency of endogenous spleen colonies and an increased granulocytic differentiation of haemopoietic stem cells. Higher colony-forming activity was also found in animals irradiated immediately after the termination of pretreatment with thyroid, but without an increase in survival. The lack of radioprotective effect under those circumstances could be explained by the persisting hypermetabolic effect of the thyroid, and by the fact that an increased proportion of haemopoietic stem cells underwent differentiation into the erythroid line.
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