Acute Gamma Irradiation Research Articles

Researches in National Institute of Radiological Sciences (NIRS) for radiation protection of non-human biota and ecosystems in Japanese environment

This paper summarizes research activities in National Institute of Radiological Sciences (NIRS) for evaluation of the radiation effects on selected terrestrial and aquatic organisms as well as the ecosystems. Seven organisms, conifers, fungi, earthworms, springtails, algae, daphnia and Medaka are presently selected to study. For the estimation of possible radiation dose, transfers of radionuclides and related elements from medium to organisms are evaluated. Dose-effect relationships of acute gamma radiation on the survival, growth, and reproduction of selected organisms have been studied. Studies on the effect of chronic gamma radiation at low dose rate were also started. In order to understand the mechanism of radiation effects and to find possible indicators of the effects, information of genome- and metagenome-wide gene expression has been collected. Evaluation of ecological effects of radiation is more challenging task. Study methods by using three-species microcosm were established, and an index for the holistic evaluation of effects on various ecological parameters was proposed. The microcosm has been simulated as a computer simulation code. Developments of more complicated and practical model ecosystems have been started. The Denaturant Gradient Gel Electrophoresis (DGGE) has been applied on soil bacterial community in order to evaluate the radiation effects on soil ecosystems.

Effects of acute gamma-irradiation on extracellular adenine nucleotide hydrolysis in developing rat brain

Cell membrane is highly sensitive to irradiation which, acting directly or indirectly, may disturb functions of constitutive proteins including membrane enzymes. Plasma membrane surface-located enzyme chain of ecto-nucleotide triphospho diphosphohydrolases (NTPDases) and 5′-nucleotidase are involved in termination of cell purinergic signalization by hydrolyzing extracellular, excitatory adenosine triphosphate (ATP), as well as nucleotide di-, and mono-phosphate (ADP and AMP) to neuroprotective adenosine. Extracellular ATP, ADP, and AMP hydrolyzes were examined in purified synaptic plasma membranes after whole-body acute irradiation. All measurements were done 24 h after irradiation of developing (15-, 30-day-old) and adult (90-day-old) rats with low (50 cGy) and high (2 Gy) dose of gamma-rays. Both, high and low doses inhibited nucleotide hydrolyses in 15-day-old rats; in 30-day-old rats low dose of radiation inhibited ADP and AMP hydrolyses while high dose inhibited only ATP hydrolyse. In adult rats high dose induced no effects, while low dose stimulated nucleotides hydrolyses. According to obtained results it was concluded that ecto-nucleotidases of young rats are more sensitive to irradiation, since even low dose induces inhibition of ecto-nucleotidases activities. Ionizing radiation, by decreasing brain nucleotide hydrolyses in developing rats, induces accumulation of ATP and decreases production of adenosine in synaptic cleft which could be neurocytotoxic. On the contrary, in adult rats low dose of radiation stimulates NTPDase and 5′-nucleotidase activity and protective adenosine production which indicates protective and adaptive mechanisms developed in adult brain neuronal cells.

Radiation Sensitivity of Primary Fibroblasts from Hereditary Retinoblastoma Family Members and Some Apparently Normal Controls: Colony Formation Ability during Continuous Low-Dose-Rate Gamma Irradiation

We previously described an enhanced sensitivity for cell killing and G(1)-phase cell cycle arrest after acute gamma irradiation in primary fibroblast strains derived from 14 hereditary-type retinoblastoma family members (both affected RB1(+/-) probands and unaffected RB1(+/+) parents) as well as distinctive gene expression profiles in unirradiated cultures by microarray analyses. In the present study, we measured the colony formation ability of these cells after exposure to continuous low-dose-rate (0.5-8.4 cGy/h) (137)Cs gamma radiation for a 2-week growth period. Fibroblasts from all RB family members (irrespective of RB1 genotype) and from 5 of 18 apparently normal Coriell cell bank controls were significantly more radiosensitive than the remaining apparently normal controls. The average dose rates required to reduce relative survival to 10% and 1% were approximately 3.1 and 4.7 cGy/h for the Coriell control strains with normal radiosensitivity and approximately 1.4 and 2.5 cGy/h for the radiosensitive RB family member and remaining apparently normal Coriell control strains. The finding that a significant proportion of fibroblast strains derived from apparently normal individuals are sensitive to chronic low-dose-rate irradiation indicates such individuals may harbor hypomorphic genetic variants in genomic maintenance and/or DNA repair genes that may likewise predispose them or their children to cancer.

Transient Impairment of Hippocampus-dependent Learning and Memory in Relatively Low-Dose of Acute Radiation Syndrome is Associated with Inhibition of Hippocampal Neurogenesis

Neurogenesis in the adult hippocampus, which occurs constitutively, is vulnerable to ionizing radiation. In the relatively low-dose exposure of acute radiation syndrome (ARS), the change in the adult hippocampal function is poorly understood. This study analyzed the changes in apoptotic cell death and neurogenesis in the DGs of hippocampi from adult ICR mice with single whole-body gamma-irradiation using the TUNEL method and immunohistochemical markers of neurogenesis, Ki-67 and doublecortin (DCX). In addition, the hippocampus-dependent learning and memory tasks after single whole-body gamma-irradiation were examined in order to evaluate the hippocampus-related behavioral dysfunction in the relatively low-dose exposure of ARS. The number of TUNEL-positive apoptotic nuclei in the dentate gyrus (DG) was increased 6-12 h after acute gamma-irradiation (a single dose of 0.5 to 4 Gy). In contrast, the number of Ki-67- and DCX-positive cells began to decrease significantly 6 h postirradiation, reaching its lowest level 24 h after irradiation. The level of Ki-67 and DCX immunoreactivity decreased in a dose-dependent manner within the range of irradiation applied (0-4 Gy). In passive avoidance and object recognition memory test, the mice trained 1 day after acute irradiation (2 Gy) showed significant memory deficits, compared with the sham controls. In conclusion, the pattern of the hippocampus-dependent memory dysfunction is consistent with the change in neurogenesis after acute irradiation. It is suggested that a relatively low dose of ARS in adult ICR mice is sufficiently detrimental to interrupt the functioning of the hippocampus, including learning and memory, possibly through the inhibition of neurogenesis.

Acute gamma-irradiation of mice BALB/c strain in dose range from 1 Gy to 3 Gy can lead to change in RAPD and I

The aim of this work is the study hereditary effects of ionizing radiation on mice progeny, whose parents were irradiated on different stages of spermatogenesis. Male mice BALB/c strain were acute irradiated by γ-radiation at doses 1, 2 and 3 Gy on gamma-unit GYPOS (dose rate- 4,5 Gy/min, source- Cs-137). For comparison of sensitivity of different stages of spermatogenesis males were crossed with females the same strain in two weeks (post meiotic stage) and in three months (pre meiotic stage) after an irradiation. The offspring in both cases contained in standard conditions and were killed in the 3-4 weeks of age. DNA was isolated from liver by using DNA PrepTM (IZOGEN Lab). Amplification was performed by using lyophilizated PCR-mix DNA CoreTM (IZOGEN Lab) on thermocycler PT-48 (TDL Company). Products of amplification were separated in 1,5 % agaroze gel and visualized by ethydium bromide. For detection effects of irradiation was used RAPD- and ISSR-assays. Analysis of offspring patterns carried out on the basis of comparison with patterns, with the purpose of registration of new, not parental bands, as case of mutation. We are counting mutation frequency per animal in the group and processed these data statistically. Our results are show, that beginning at dose 1 Gy, mutation frequencies in irradiated offspring is significantly distinguished from the control group. At the same time, change of mutation frequencies is independent of increasing of the irradiation dose. The comparison of sensitivity different stages of spermatogenesis is indicated, that post-irradiated changes in RAPD- and ISSR-patterns of pre and post meiotic cells have similar character.

The sensitivity of a forest soil microbial community to acute gamma-irradiation

The community response of soil microbes exposed to acute gamma (γ)-irradiation at 0, 1, 5 and 10 kGy doses were examined for 56 days after irradiation. Physiological activity was determined by community substrate utilisation potentials (BIOLOG™) and a glucose substrate assay. Culture dependant analysis was used to track the changes in fungal and bacteria numbers while culture independent analyses were carried out to assess changes in bacterial community composition. As a consequence of irradiation, bacterial populations initially decreased and then exceeded control populations at the higher radiation doses, while fungal populations did not recover substantially after irradiation. These data suggest that either changes in niche competition between bacteria and fungi or a change in nutrient availability has led to the re-establishment of bacterial populations. The recovery in bacterial populations was mirrored by substrate utilisation potentials increasing in both the rate of utilisation as well as the number of substrates being used. Molecular profiling (DGGE) at later time points showed discrete dominant bands in profiles from the 5 and 10 kGy treatments suggesting outgrowth of certain taxa above background levels. The identities of these taxa were typical of soil environments. In conclusion microbial functioning and physiology can recover from acute doses of γ-irradiation, yet higher doses may lead to changes in the underlying community structure, presumably due to competition for recently opened niches.

The effect of γ-radiation on induction of the hobo element transposition in Drosophila melanogaster

The transposition frequency of the hobo mobile element in four successive generations of Drosophila melanogaster strain y2-717 after an acute gamma-irradiation with a dose of 30 Gr amounted to 7.5 x 10(-4) per site per genome per generation. Under the same conditions, PCR analysis of the genomic DNA of y2-717 flies detected new variants of defective hobo sequence. No changes in the hobo localization and PCR products compared with the control were detected in the case of single irradiation with doses of 3 and 30 Gr. The localizations of hobo element on polytene chromosomes of y2-717 strain did not change during 11 generations after five exposures of flies to 30 Gr. Irradiation of a highly unstable D. melanogaster strain y+743 did not increase the number of families with mutant progeny, yet increased the total number of mutant descendants almost twofold, from 5 to 9%.

A new locus for resistance to gamma-radiation-induced thymic lymphoma identified using inter-specific consomic and inter-specific recombinant congenic strains of mice.

Mice of the C57BL/6J inbred strain develop thymic lymphomas at very high frequency after acute gamma-irradiation, while mice of several inbred strains derived from the wild progenitor of the Mus spretus species and their F1 hybrids with C57BL/6J appear extremely resistant. Analysis of the genetic determinism of the gamma-radiation-induced thymic lymphoma (RITL) resistance with the help of inter-specific consomic strains (ICS), which carry a single introgressed Mus spretus chromosome on a C57BL/6J genetic background, provide significant evidence for the existence of a thymic lymphoma resistance (Tlyr1) locus on chromosome 19. The subsequent analysis of the backcross progeny resulting from a cross between consomic mice heterozygous for the Mus spretus chromosome 19 and C57BL/6J mice, together with the study of inter-specific recombinant congenic strains (IRCS), suggest that this Tlyr1 locus maps within the D19Mit60-D19Mit40 chromosome interval. In addition to the discovery of a new locus controlling RITL development, our study emphasizes the value of ICS and IRCS for the genetic analysis of cancer predisposition.

The Effect of Low Doses of Gamma Irradiation on the Homeostasis of Intracellular Calcium in Lymphocyte Cells of Rats

The influence of acute and chronic gamma irradiation (0.25 and 0.5 Gy doses) on rat lymphocytes was examined on the 1st and 10th days after irradiation. Acute gamma irradiation increased the intracellular calcium concentration in the cytoplasm of the lymphocytes on the 1st day after the influence of the radiation. Calcium concentration returned to the control level on the 10th day after the effect of the radiation at all the doses. In the lymphocytes after acute irradiation the increase of the Ca2+ concentration in the intracellular depots on the 1st day was observed. Changes were also observed in the physicochemical state of the plasma membrane of these cells. Research on the influence of prolonged gamma irradiation on intracellular calcium homeostasis revealed opposite effects in comparison with acute gamma irradiation.

Prolonged effects of acute gamma irradiation on acetylcholine-induced potassium currents in human umbilical vein endothelial cells.

Bourlier, V., Diserbo, M., Gourmelon, P. and Verdetti, J. Prolonged Effects of Acute Gamma Irradiation on Acetylcholine-Induced Potassium Currents in Human Umbilical Vein Endothelial Cells. Radiat. Res. 155, 748-752 (2001). We have recently reported an acute effect of gamma irradiation (15 Gy, 1 Gy/min) on acetylcholine-mediated endothelium-dependent relaxation in rat aortic rings. Given the importance of permeability to K+ to endothelium-dependent relaxation, we have evaluated the effect of the same radiation on K+ currents in human endothelial cells in culture using the patch-clamp technique in the whole-cell recording configuration. Our results indicate that, in resting cells, gamma irradiation has no effect on endothelial permeability to K+. However, irradiation during stimulation of endothelial cells with acetylcholine reduces the sustained increase in permeability to K+ observed in the acetylcholine-stimulated, nonirradiated cells. Additional experiments using K+ channel inhibitors (TEA, charybdotoxin, apamin) suggest that irradiation may in part decrease the prolonged activation of Ca2+-activated K+ channels by acetylcholine. Taken together with our previous finding that irradiation inhibits the acute relaxing effects of acetylcholine, these results show that gamma irradiation also affects the delayed effects of acetylcholine on permeability to K+.

Dietary sugar beet fiber ameliorates diarrhea as an acute gamma-radiation injury in rats.

Gamma radiation induces diarrhea as an acute injury. We have studied whether ingestion of sugar beet fiber influences radiation-induced diarrhea. Abdominal irradiation with gamma rays induced diarrhea in male Wistar/ST rats from 2 to 7 days after a single sublethal dose. The body weight of the irradiated rats was decreased temporarily at 4 days after irradiation regardless of the ingestion of sugar beet fiber. At day 8, it returned to almost the same level as that of unirradiated rats. A change in daily food intake resulted in a pattern similar to that for body weight. Dietary sugar beet fiber had little significant effect on the changes in body weight and daily food intake, and its ingestion significantly decreased gamma-ray-induced diarrhea. Changes in biochemical and histological parameters in intestinal mucosa (small intestine, cecum and colon) were not greatly influenced by the ingestion of sugar beet fiber through the periods of diarrhea. It was concluded that dietary sugar beet fiber ameliorated the diarrhea induced by abdominal irradiation. We suggest that the inhibitory effect of the ingestion of sugar beet fiber is due to its effects on the luminal environment, such as support for bacterial function in the luminal contents in the colon of animals that ingest sugar beet fiber.

Synthetic activity of rat blood lymphocytes under acute and continuous gamma-irradiation -- fluorescent microspectral study.

The effects of different doses of acute and continuous gamma-irradiation on the synthetic activity of rat blood lymphocytes stained with acridine orange were studied by fluorescent microspectrometry. Male rats were exposed to acute gamma-irradiation with doses of 7.5, 4 and 3 Gy, or to continuous irradiation with dose rates of 14.4, 2.1, 1.1 and 0.43 cGy/day, respectively. The changes of the synthetic activity of blood lymphocytes occurred in three main stages after acute gamma-irradiation and in four stages under continuous irradiation. The stages reflect the processes of depression and activation of the immune system under irradiation. Essential differences between the acute and continuous effects were observed in the first stage. After acute gamma-irradiation, the synthetic activity decreased sharply, indicating the predominant contribution of the damaging effect of irradiation, whereas under continuous irradiation, as a result of the stimulatory effect of low-dose irradiation, the synthetic activity increased during the first stage.

Induction of gene conversion in yeast cells continuously cultured at high radiation background

The induction of genetic damage was investigated by culturing diploid yeast Saccharomyces cerevisiae D7 cells continuously at radiation levels ranging from 0.383 microSv/h to 1.275 mSv/h by selecting appropriate concentrations of tritiated water in the growth medium. These radiation levels correspond to 3-10,000 times the natural background. Parameters such as growth kinetics, gene conversion frequency at background radiation and after a challenging dose of acute gamma-radiation or alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were assessed. The gene conversion frequency in most of the assays was in the range of 5-10 convertants per 10(6) cells, as in the case of controls. However, a number of the cultures showed conversion frequencies above 20 per 10(6) viable cells. This stochastic phenomenon occurred more frequently in cells which were incubated at higher radiation levels and for longer durations. This suggests that radiation is responsible for the phenomenon. When subculturing continued beyond 900 h, gene conversion frequencies reverted back to normal values in all cultures in spite of elevated background radiation levels, thus suggesting an adaptive response. The generation time of the cells was 78 min in all cultures irrespective of the radiation level. The response of the cells cultured at elevated background radiation levels to subsequent challenging treatment with gamma-radiation or MNNG was identical to that of the control cultures. Our results suggest that in eukaryotic yeast, low-level radiation may induce an adaptive response to chronic radiation, whereas no such response could be detected when the cells were challenged with acute high-dose exposure or with MNNG.

Effect of Acute Gamma Radiation on some Physiological Features of Lichens

The influence of acute gamma radiation on four physiological characteristics of lichens was investigated. Membrane permeability in irradiated thalli of Cladonia arbuscula, Cetraria islandica and Hypogymnia physodes increased considerably compared to controls. The nitrogen content in Peltigera aphthosa appeared to be stable to acute gamma radiation. Up to 1000 Gy there was no essential decrease in respiration intensity in H. physodes and P. aphthosa or of peroxidase activity in P. aphthosa..

Effect of acute gamma radiation on some physiological features of lichens

The influence of acute gamma radiation on four physiological characteristics of lichens was investigated. Membrane permeability in irradiated thalli of Cladonia arbuscula, Cetraria islandica and Hypogymnia physodes increased considerably compared to controls. The nitrogen content in Peltigera aphthosa appeared to be stable to acute gamma radiation. Up to 1000 Gy there was no essential decrease in respiration intensity in H. physodes and P. aphthosa or of peroxidase activity in P. aphthosa.

Effect of acute gamma radiation on some physiological features of lichens

The influence of acute gamma radiation on four physiological characteristics of lichens was investigated. Membrane permeability in irradiated thalli of Cladonia arbuscula, Cetraria islandica and Hypogymnia physodes increased considerably compared to controls. The nitrogen content in Peltigera aphthosa appeared to be stable to acute gamma radiation. Up to 1000 Gy there was no essential decrease in respiration intensity in H. physodes and P. aphthosa or of peroxidase activity in P. aphthosa.

Cadmium deposition in rat heart following cadmium chloride and/or60Co radiation

Abstract Male Sprague‐Oawley rats were separated into nine groups and injected with cadmium (Cd) intraperitoneally every three days for 29 days for a total of nine injections. Injection doses ranged from 0 to 2.5 mg Cd/kg‐1 of body weight. Twenty‐four hours following Cd injections, rats received an acute whole body 60Co gamma radiation dose of 0, 3.62, or 5.43 Gray (Gy) at a dose rate of 3.04 Gy/min. Rats were sacrificed on day January 1994 7, or 21 post‐irradiation. Co‐insult groups which had been irradiated following Cd injections showed lower Cd concentrations in heart tissue than those groups which had been injected with Cd and sham‐irradiated. Our data indicate that radiation contributed to clearance of Cd from the heart. The present study points to a need for researchers to continue to study links between the environment and disease.

Skin fibroblast cell lines derived from non‐hodgkin's‐lymphoma (NHL) patients show increased sensitivity to chronic gamma irradiation

Cultured fibroblast cells from 19 patients with non-Hodgkin's lymphoma (NHL), 3 patients with ataxia telangiectasia (AT), 3 AT heterozygotes and 11 (presumed) normal subjects were studied for impaired colony-forming ability after chronic gamma irradiation. Five cell lines from the NHL patients were also examined for the sensitivity to acute gamma irradiation, as compared with those of normal subjects. To ascertain the degree of radiosensitivity of different cell lines, a comparison was made of the D10 values (radiation dose resulting in 10% survival) for each cell line, estimated "by eye" from the actual survival curves, and also from the calculated curves fitted to a log-linear model. It was observed that the acute gamma irradiation failed to show any appreciable difference in the radiation response of the cell lines from NHL patients as compared with those of normal subjects. However, chronic irradiation demonstrated significantly increased radiosensitivity in at least 10-12 NHL patients with a p value of less than 0.05, when the D10 values of each patient's cell line were compared with the calculated composite values for the normals. When the D10 values of the NHL patients and the normal subjects were compared as 2 groups, the former appeared to be significantly more sensitive to chronic gamma irradiation (p less than 0.0001). The same level of significant difference in radiosensitivity was found between the 2 groups when their D37 values (radiation dose resulting in 37% survival) were compared. In general, the radiation response of the NHL patients was similar to that of the AT homozygotes and heterozygotes used as a positive control group. Our data thus show that increased radiosensitivity is associated with the NHL patients studied, indicating an underlying abnormality of their DNA repair.

Long-Term Overproduction of Collagen in Radiation-Induced Fibrosis

Collagen metabolism was investigated in the fibrotic tissue which developed in pig thigh muscle 6 to 15 months after acute gamma irradiation. During this period, total collagen deposits in the fibrotic tissue increased 10-fold compared to the healthy muscle tissue. These deposits were composed mainly of type I and III collagen, and the type I/type III ratio was lower in the fibrotic than in the muscle tissue. Small pieces of both fibrotic and muscle tissue were incubated with [14C]proline. The [14C]hydroxyproline content of the fibrotic tissue reflected large concomitant increases in the synthesis of total collagen, mainly of types I and III, which rose 14- and 17-fold, respectively. Similarly, the level of type I and type III procollagen mRNAs rose 9- and 5-fold, respectively, in the fibrotic tissue versus the muscle tissue. These results suggest that procollagen gene transcription or RNA maturation in the cell nuclei is activated in the fibrotic tissue. The possibility that such activation is due to the long-term inflammatory state of this tissue is discussed.

Radiosensitivity of fibroblasts obtained from a café-au-lait spot and normal-appearing skin of a patient with neurofibromatosis (NF-6)

Fibroblast cells derived from a café-au-lait spot and normal-appearing skin of a neurofibromatosis (NF-6) patient were studied for radiosensitivity in comparison with two normal cell lines used as "controls." No difference in radiosensitivity was observed between the patient's cell lines and the controls using acute gamma-irradiation. However, a markedly increased radiosensitivity of the fibroblasts obtained from the patient's skin of normal appearance was demonstrated after chronic gamma-irradiation. The cells from the café-au-lait spot showed intermediate sensitivity to chronic irradiation as compared with the control cell lines and the fibroblasts derived from the normal skin of the patient. These results showed the usefulness of chronic irradiation in detecting increased cellular radiosensitivity which may result from a unique DNA repair defect in an NF patient. We suggest that enhanced genetic changes in radiosensitive NF patients may lead to formation of café-au-lait lesions and certain tumors. Such a transformation may be associated with production of radiotolerant cells.