Production of anti-SRBC antibodies after DDC administration in whole-body irradiated mice.

Production of antibody-forming cells (PFC) was studied in mice subjected to a single whole-body irradiation dose of 3.8 Gy after sodium diethyldithiocarbamate (DDC, 800 mg/kg) injected 30 min before irradiation. Animals were immunized (1% SRBC) 4 h, 5 and 10 days after irradiation, and the number of PFC was determined by a modified Jerne plaque technique on days 4, 7 and 10 after immunization. After the irradiation alone, the PFC levels were markedly reduced at all time intervals in comparison with unirradiated controls. Upon immunization of animals on day 10 after irradiation the peak PFC levels were observed on day 7 after immunization in the only irradiated group and in the group irradiated after DDC administration (in controls on day 4 after immunization). Administration of DDC entirely eliminated the unfavourable effect of radiation if immunization was performed 4 h after irradiation, in terms of the number and the peak level of PFC. Upon immunization of animals on day 5 and day 10 after irradiation the PFC levels were not markedly influenced by DDC injection.

The effect of microwave radiation on the primary IgM response to sheep red blood cells in mice.

We investigated the changes in the number of plaque-forming cells (PFC) in spleens of CBA mice after microwave (MW) irradiation. The mice were immunized with sheep red blood cells, the number of PFC was determined on days 4 and 5 after immunization. Mice received single doses of MW irradiation on days 1, 2, or 3 after immunization (exposure duration 1 to 9 min). It was found that the number of PFC was changed after MW irradiation and that this effect depended on the absorbed dose. Shorter exposures for 1, 3, and 5 min (SA = 4, 12, and 20.1 kJ/kg) stimulated the formation of PFC, exposures for 7 and 9 min did not change the number of PFC. After MW heating (exposure 5 min), the rectal temperature of mice was elevated by 2.5 degrees C. If the same thermal effect was induced by elevating the environmental temperature, the number of PFC was not increased. The observed changes in PFC number are probably due to the specific effect of MW radiation.

Protective efficacy of combined administration of lipopolysaccharide of E. coli and chemical radioprotectors under conditions of prolonged irradiation.

We investigated the protective effectiveness of the lipopolysaccharide of E. coli (LPS) in a combination with a mixture of chemical radioprotectors in female mice of the strain H at various radiation dose rates. LPS in a dose of 0.08 mg per kg of body mass was administered 1, 3, or 24 hours prior to irradiation, the radioprotective mixture (cystamine 90 mg X kg-1 + 5-methoxytryptamine 15 mg X kg-1) was administered 10 minutes before irradiation. Dose rates of 612 mGy X min-1 (irradiation time 10 to 15 minutes), 38 mGy X min-1 (3 to 4 hours), and 8.2 mGy X min-1 (27 to 29 hours) were used. The results showed that isolated administrations of LPS or of the radioprotective mixture increased the resistance of the mice against prolonged irradiation; the combined administration even enhanced the efficacy of the radioprotective action. However, this efficacy depended on the magnitude of the dose rate. At dose rates higher than 38 mGy X min-1 the effectiveness of the chemical protection prevailed, whereas at lower dose rates the biological and especially the combined protection became effective. We demonstrated a slight pyrogenic effect of LPS by measuring oxygen consumption and changes in some parameters of the hematopoiesis.

Resistance to prolonged irradiation in mice influenced by thyroid hormones and chemical radiation protectors.

After the end of 10 and 21 days' treatment of mice with dried thyroid gland (0.6 g/100 g diet) the effect of some radiation protectors against prolonged irradiation (38 mGy/min) increased. The combination of propranolol, phenobarbital and cystamine was more effective than a mixture of cystamine and 5-methoxytryptamine both in mice fed on a normal and a thyroid gland diet. A reduced oxygen consumption after the application of protectors reflected the degree of protection. The number of thrombocytes in peripheral blood increased after the end of thyroid treatment, which indicated a possible shift in the differentiation of stem cells in favour of megakaryocytes.

Characterization of the protective effect of radioprotective substances by means of long-term changes in oxygen consumption.

A comparison of long-term hypothermic effects of radioprotective substances and their protective effectiveness was carried out in mice after acute and prolonged irradiation. As radioprotective substances were used AET, cystamine, serotonine, 5-methoxytryptamine, cysteamine-S-phosphate, sodium fluoroacetate and some double combinations of these substances. The irradiation was carried out with dose rates 38.3 and 612.5 mGy/min, the hypothermic reaction was evaluated according to total oxygen consumption, measured during 5 hours after the drug administration. The results demonstrated the existence of a correlation between the suppression of metabolic processes and both short-term and long-term protective effectiveness of radioprotective substances. The protective effectiveness of a drug is the higher, the greater decrease of oxygen consumption is induced by this substance in the investigated time interval. An analogous dependence was also demonstrated between the duration of hypothermic and radioprotective effects. The found correlation is valid for both acute and prolonged irradiation (correlation coefficient 0.79-0.87; p < 0.01).

Dynamic characteristics of a metabolic reaction of mice with different responses to irradiation.

The course of the reaction of mice placed in a metabolic chamber and afterwards irradiated with an exposure dose of 610 R was studied by assessing total oxygen consumption and the size of its fluctuation. Fluctuation was greater in non-survivors than in survivors in the initial phase of the metabolic reaction only (P is less than 0.05), while the mean oxygen consumption values for the two groups were the same, In the distribution of the individual values there were more non-survivors in the frequency class with a high fluctuation level and, conversely, more survivors in the low level class (P is less than 0.01). Fluctuation during the studied reaction was more variable in survivors, despite its lower level, than in non-survivors. The reciprocal relationship between the size and fluctuation of oxygen consumption, determined for the whole series of experimental mice at given stages of the metabolic reaction, is linear. Attention is drawn to the association between changes measured in the metabolic rate and motor activity and to the possibility that it is determined by the individual's type of nervous activity.

Radioprotective and toxic effects of a mixture of AET and 5-methoxytryptamine in mice.

The authors studied the radioprotective efficacy and toxicity of an AET + 5-methoxytryptamine mixture and its effect on the course of respiratory exchange, using different weight ratios of the two components. The optomum was found to be 150 mg AET/kg b.w + 25 mg 5-MOT/kg b.w. This mixture gave very good protection in the supralethal exposure range and markedly prolonged its duration. The high toxicity of this mixture was abolished by the pre-administration of glutathione. Raised and longer protection was also manifested in the course of respiratory exchange, showing that an association exists between changes in energy metabolism and raised radioresistance of the organism.

Respiratory gas exchange as an indicator of changed radioresistance in mammals.

The paper deals with the problem of detection of radio-protective effects during irradiation. The method used is based on the fact that the known effective pharmacological and chemical radioprotectives (aminoethylthiouronium bromide HBr (AET), cystamine, sodium fluoroacetate (FAc), 5-hydroxytryptamine (5-HT), 5-methoxytryptamine (5-MT) and others) interfere directly or indirectly with enzymatic steps in energy metabolism of the organism. In mammals they induce at the same time an increase of resistance against ionizing radiation and a decrease in the respiratory gas exchange expressed by a depressed oxygen consumption. In experiments carried out on male mice of the H strain and male rats of the Wistar strain it was found that animals respiring a hypoxic mixture (5-8% O2, STPD), have a lower oxygen consumption during the period of increased radioresistance similar to that seen during the effect of radioprotective drugs. This finding is of practical importance as it enables one to evaluate quantitatively the effect of radioprotective measures (including the hypoxia) in individual experimental animals during the course of irradiation.