The recovery of humoral immunity after the long-term action of tritium oxide at different irradiation levels

Dynamics of recovery of humoral immunity of CBA mice was studied 1, 3, 6 and 12 months after termination of long-term exposure to tritium oxide at various levels of absorbed doses (3, 5 and 9 Gy) and dose rates (3.3, 4.9 and 9.2 cGy.day-1). A severer and more stable residual radiation damage was observed in the department of lymphocyte precursors. A considerable decrease in the content of antibody producers was due to the lymphoid tissue hypoplasia. There was a direct relationship between the immunodeficiency and dose rate and total absorbed dose of beta radiation.     

Cloning of murine B- and T-lymphocytes in vitro after the long-term action of tritium oxide

The cloning method was used to study the content of B- and T-lymphocyte committed precursors in central and peripheral organs of the immune system of mice at different times after long-term exposure to tritium oxide (a cumulative dose of approximately 9 Gy). It was shown that recovery of the colony-forming ability of the committed lymphocyte precursors was different in central and peripheral lymphoid organs; the dynamics and degree of restoration of the pools of B--(CFU--LB) and T--(CFU--LT) lymphocyte precursors were different.     

The early changes in humoral immunity under the prolonged action of tritium oxide with different dose rates

Within the dose range from 0.2 to 1 Gy, early changes in the humoral immunity of mice exposed to tritium oxide at varying dose rates have been investigated. The study of the immunity impairment at different stages of immunopoiesis permits to reveal the points (a lymphocyte precursor department) that are mostly affected by radiation, to find the causes of the decrease in the antibody production, and to reveal the relationship between the damages observed the dose absorbed and dose rate of beta radiation.     

The significance of immunity disorders in the development of tumorous effects during the long-term action of tritium in mice

In experiments with CBA mice it was shown that the long-term influence of tritium oxide administered with drinking water daily during 180 days (370 kBq.g-1 of body mass, cumulative dose 8.7 Gy, dose rate 4.5 cGy.day-1) causes the development of immunity deficiency 90 days after the onset of the administration that persists for up to 270 days. There is a 34% decrease in the average life of irradiated animals and an increase in the number of malignant neoplasms (postmortem examination was performed after natural death or killing on days 250, 350 and 450). There is a direct relationship between the occurrence of malignant neoplasms and the immunity deficiency.     

Chromosome structural damages to the myelokaryocytes of rats in late periods after chronic exposure to tritium and external gamma irradiation

A pronounced variation in the total amount and spectrum of chromosome aberrations of rat myelocarycytes was found at later times following long-term exposure to tritium oxide and external gamma-radiation (137Cs). Cells with atypical chromosomes (symmetrical exchanges) were 1.5-2 times more frequent in bone marrow of tritium-treated rats throughout the entire lifetime.     

Nitric oxide voltammetric measurements in the rat brain after gamma irradiation

The effects of a lethal gamma irradiation were investigated on cerebral NO-ergic system by using a voltammetric method in freely moving rats. It is reported that the cortical NO concentration increases right from the end of the radiation exposure (15 Gy) and reaches a maximal magnitude (+120%) 24 h later. A dose-effect relationship from 2 to 15 Gy for gamma-ray exposure has also been observed. The effects, obtained with either an NO synthase inhibitor nonselective for the different NO synthase isoforms or an NO synthase inhibitor selective for the constitutive isoform, suggest that the radiation-induced increase in NO is likely to be dependent on the inducible NO synthase isoform. Moreover, experiments performed under ex vivo conditions showed that the cortical mRNA level for Ca(++)-independent NO synthase, the brain NOS activity, and urinary nitrites/nitrates increased significantly 24 h after gamma-ray exposure. These results demonstrate that a supralethal whole-body irradiation alters the NO-ergic pathways. The increase in NO obtained under such conditions might constitute a good index of central nervous system radiosensitivity during the acute phase of the radiation syndrome.     

The state of dog's metabolism after long interval after oxide tritium administration

An attempt to evaluate the influence of tritium oxide on the metabolism by some indices of lipid metabolism (common lipids, beta-lipoproteins, cholesterin), protein metabolism (cholinesterasa) and carbohydrate metabolism (blood sugar) was made. It was established that the introduction into organism of tritium oxide in the quantities, which could form lethal and sublethal doses of internal radiation, provoked the main changes of values of mentioned indices of metabolism. The character of metabolism changes in the remote period allows us to judge about the development of sclerosis processes, which can be the result of radiation-stipulated acceleration of organism aging.     

Inactivation of non-syngeneic hematopoietic stem cells by mouse lymphocytes after long-term exposure to tritium oxide

A study was made of functional activity of lymphocytes, which inactivated nonsyngeneic colony-forming units (CFU) in allogenous and xenogenous interaction systems, at different times after long-term action of tritium oxide in a cumulative dose of approximately 9 Gy. The function of these lymphocytes was depressed during the first months after termination of exposure while at later times it exceeded the control level. The consequences of the interaction between lymphocytes and nonsyngeneic CFU were also studied in this work.     

Relative biological effectiveness of tritium oxide based on nucleic acid metabolic indices

Relative biological effectiveness (RBE) of tritium oxide, as compared to gamma-rays (137Cs), with regard to LD50/30 is 2,32 +/- 0,69 for rats. The RBE coefficients for tritium oxide are obtained with regard to some indices of nucleic acid metabolism in the thymus and spleen during the dose formation (0-14 days). The RBE of tritium oxide increases with a decrease in radiation dose as determined according to the concentration and content of DNA per organ and activity of thymus DNAases.     

Gene expression profiles in mouse liver after long-term low-dose-rate irradiation with gamma rays

Changes in gene expression profiles in mouse liver induced by long-term low-dose-rate γ irradiation were examined by microarray analysis. Three groups of male C57BL/6J mice were exposed to whole-body radiation at dose rates of 17-20 mGy/day, 0.86-1.0 mGy/day or 0.042-0.050 mGy/day for 401-485 days with cumulative doses of approximately 8 Gy, 0.4 Gy or 0.02 Gy, respectively. The gene expression levels in the livers of six animals from each exposure group were compared individually with that of pooled sham-irradiated animals. Some genes revealed a large variation in expression levels among individuals within each group, and the number of genes showing common changes in individuals from each group was limited: 20 and 11 genes showed more than 1.5-fold modulation with 17-20 mGy/day and 0.86-1.0 mGy/day, respectively. Three genes showed more than 1.5-fold modulation even at the lowest dose-rate of 0.04-0.05 mGy/day. Most of these genes were down-regulated. RT-PCR analysis confirmed the expression profiles of the majority of these genes. The results indicate that a few genes are modulated in response to very low-dose-rate irradiation. The functional analysis suggests that these genes may influence many processes, including obesity and tumorigenesis.     

Regenerative effects of tetrachlorodecaoxide in BD IX rats after total-body gamma irradiation

Tetrachlorodecaoxide (TCDO) was tested for its effects in BD IX rats when combined with a single dose nearing LD50 of total-body irradiation (gamma rays, 60Co). In pilot tests we found that TCDO administrations prior to or immediately after irradiation led to a very high mortality rate (up to 90%), whereas the initiation of TCDO treatment on Day 2, 3, or 4 after irradiation lowered the death rate noticeably, with optimum results when TCDO application was started on Day 4. In our major experiment on 100 BD IX rats, it was demonstrated that the following treatment schedule considerably decreased the death rate (from 44 to 4%): 15.5 mumol TCDO/kg body wt/day on Days 4-6 after irradiation and 7.75 mumol/kg body wt/day on Days 7-11. The animals treated with TCDO showed only mild anemia in the peripheral blood, accompanied by reticulocytosis and low-grade leukocytopenia. Examination of the bone marrow on Day 12 after irradiation revealed X-ray-induced agranulocytosis in the animals that had received only physiological saline solution, whereas in the bone marrow of the animals treated with TCDO there was erythropoiesis as well as myelopoiesis. In addition, the degree of hair loss and depigmentation occurring about 1 month after irradiation was considerably reduced by TCDO. From these results it can be postulated that TCDO has two different effects: as an oxygen donator it causes radiosensitization in the tissue when given before or immediately after irradiation; as an agent stimulating phagocytes and tissue regeneration, it promotes regeneration very effectively when damage is already evident in the tissue.     

The action of gamma irradiation on terrilytin immobilized on cellulose-fiber materials

The effect of gamma-radiation on terrilytin, a proteolytic enzyme immobilized on modified and nonmodified cellulose materials was studied by EPR. Dialdehyde cellulose and graft copolymer of cellulose and polyacrylic acid were used as the modified cellulose materials. Dependence of the native and immobilized terrilytin activity and the content of free radicals in the irradiated samples on the irradiation dose was observed. It was shown that immobilization of the enzyme led to increasing of its stability to the effect of the ionizing radiation. This was due to transfer of the free valency from terrilytin to the carrying polymer which prevented radiation and chemical destruction of the enzyme. The proteolytic activity of native terrilytin subjected to gamma-irradiation markedly decreased because of intramolecular and intermolecular interactions during reactions of the terrilytin free radicals, since in this case there was no polymer as an acceptor of the enzyme free valency.     

Resuscitation of microorganisms after gamma irradiation.

Microbiological analysis of rock exposed to gamma-radiation doses between 0 and 9.34 kGy indicated that some microorganisms became viable but nonculturable (VBNC) and lost metabolic capacity as measured by BIOLOG microtiter plates. To investigate this phenomenon, portions of irradiated rock were placed at 4 degrees C for 2 months in an attempt to resuscitate the microbes to a culturable state. Culturable heterotrophs were enumerated and BIOLOG plates were used to determine the metabolic capability of the microbial community. Culturable bacteria that had previously been nonculturable were found at all doses. The number of colony types decreased from 26 in the nonirradiated control rock to between 9 and 10 in rock irradiated at doses ranging from 2.34 to 9.34 kGy. BIOLOG plates indicated partial recovery of metabolic capacity in all the samples tested. Fatty acid methyl ester analysis of the recovered isolates using the MIDI system (Microbial ID, Inc.) yielded three distinct groups of related bacteria. All resuscitated isolates clustered with the original nonirradiated isolates at the genus level, and 92% of them clustered at the species level. These results indicate that microbes were likely resuscitated from a VBNC state.     

Changes of lipofuscin-like pigments in erythrocytes and spleen after whole-body gamma irradiation of rats

Whole-body gamma irradiation of rats induced the formation of lipofuscin-like pigments in erythrocytes. Erythrocytes that were damaged by oxidation were scavenged in the spleen, and lipofuscin-like pigments were transferred from erythrocytes to the spleen during this process. The time course of lipofuscin-like pigments in erythrocytes and spleen indicates that the pigments were not induced by the action of free radicals produced by ionizing radiation but rather were a sequela of postirradiation metabolic changes.     

Time course of lipolytic activity and lipid peroxidation after whole-body gamma irradiation of rats

The content of fluorescing products of lipid peroxidation (LFP) and hormone-stimulated lipolytic activity were determined in rat epididymal adipose tissue during a 29-day interval after whole-body gamma irradiation. An increase in LFP was accompanied by a decrease in lipolytic activity. It is suggested that these effects are interrelated and that the decrease in lipolysis in irradiated, semi fasting rats is an additional deteriorating factor leading to death in some animals.