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The effect of vibration on the development and outcome of radiation injury was studied and the efficacy of pharmacochemical and local protection was measured. The biological effect of the combined exposure was estimated by radiobiological and hematological methods. The animals were exposed to vibration with a frequency of 70, 700, 1500 Hz (during single and repeated exposures) and irradiation with X-rays, gamma-rays and protons at different doses. Vibration may exert a significant effect on the development and outcome of radiation injury of animals. The effect was that this factor was capable either of increasing or decreasing responses of the animal body to ionizing radiation. The direction and level of changes depended on the pattern and force of stimulation, time and sequence of action of factors, etc. The lymph tissue showed high sensitivity to vibration. The findings indicate that vibration may both enhance and diminish the efficacy of antiradiation pharmacochemical drugs.
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A protective effect of a combined application of radioprotectors (AET -i.p., mexamine -s.c.) was studied in experiments on mice. Duration of the protective effect on the haemopoietic stem cells and on the survival of mice after a lethal exposure to X-ray radiation lasted for 5 hours after the injection. DRF calculated from a change of LD 50/30 reached the maximum (1.53) within 30 min after the injection, and was equal to 1.17 within an interval of 5 hrs. The protection of haemopoiesis, as expressed by DRF calculated from an equieffective exposure for 2 ESC, reached the maximum within a 60 min interval after the injection (DRF=3.4). D0 calculated from the CFU survival curves of endogenous haemopoietic tissue colonies (ESC) was, within a 120 min interval, almost three times higher (310 R) than in the control group (110 R). After the injection of radioprotectors a greater number of haemopoietic CFU survives at an exposure of 100-400 R than after mere irradiation. The postirradiation decrease in the weight of small intestine was smaller in protected animals than in the controls. The role of a decrease of the radiation damage to the haemopoietic stem cells in the total protective effect of the radioprotectors used is discussed.
Test on mice demonstrated the radio-protective activity of 12 derivatives of 4-oxyhexahydropyrimidinethione-2 and 1,2,3,6-tetrahydropyrimidinethione-2 well-marked with intraperitoneal administration 10--20 minutes prior to irradiation (1000 r, exposure dose rate--10 r/min). As a whole the tetrahydroderivates are more toxic.
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The SH-groups of alpha-mercapto-propionylglycine (MEPRIN) are remarkably stable in diluted solution either at room temperature or at 50 degrees C, even if storing takes place under air-bubbling. The SH-activity was measured by polarographic method and amperometric titration. Neutralization of the carboxyl group decreases the stability of the sulfhydryl groupings. Evaporation of neutralized solution leads to a 30--50 per cent decrease of SH-activity. Lyophilization reduces this loss by 10--15 per cent. Neutralization is best carried out in the absence of oxygen; in this case, 94 per cent of the sulfhydryl activity will persists, irrespective of the pH. The dissociation constant of MEPRIN-SH is pK' = 8.47. The SH-stability of the product is satisfactory when neutralized in nitrogen atmosphere to pH 3--5; a loss of only 5 per cent can be expected after storing in an oxygen-free 10(-3) molar solution for 144 hours. Between pH 6 and 8 this value is 31 per cent on the average, while at pH 9 it is more favorable again.
The effect of polyriboguanylic-polyribocytidylic acid complex was investigated against acute X- and prolonged 60Co-gamma irradiation. Prophylactic administration of the polyribonucleotide complex increased endogenous spleen colony formation and the percentage of survival of irradiated BALB/c mice. The most pronounced effect was observed when the animals had been irradiated at the time of maximum interferon accumulation in blood, i.e. 24 hr after interferon induction by the polyribonucleotide complex.