Residual activity data of 60Co and 152Eu were not enough to evaluate the dosimetry system DS86 in around 1987. Additional data of 152Eu, 60Co, 36Cl, 63Ni were accumulated both in Hiroshima and Nagasaki. The results of 152Eu in Hiroshima revealed that the measured data were 30-40% lower than the activation calculation based on the DS86 neutrons. The data beyond 1300 m ground range were not clarified because of detection limit o the gamma-ray measurement. The results of 60Co showed similar discrepancy as 152Eu. In the new dosimetry system DS02 (tentative name) , the coordinate of the hypocenter, the height of burst, the yield of the bomb were reevaluated. As a result, residual activity data and calculations show good agreement up to about 1300 m at Hiroshima and Nagasaki. [J Radiat Res 44:383 (2003)]

View full abstract

Discrepancy between measured Eu-152 activity and theoretical calculation has long been discussed. Various ideas were examined to solve the problem on the bases that observed values are correct, however, agreeable answer has not been obtained. The Hiroshima and Nagasaki samples measured previously were re-measured by using extremely low background Ge detectors in Ogoya Underground Laboratory. As a results, Eu-152 could not be detected in the samples collected from more than 1000 m from hypo-center for Hiroshima and more than 600m for Nagasaki. New Eu-152 measurements were conducted for kg-size Hiroshima samples and compared with Cl-36 measurement by AMS method.Eu samples separated and enriched by the JCAC were measured at Ogoya during March to August in 2002 by large volume well type Ge. As a result, Eu-152 activities in 10 samples collected at 146m to 1400 m from hypocenter agreed well with theoretical calculation based on the DS86. [J Radiat Res 44:383 (2003)]

View full abstract

As a part of reassessment study of A-bomb radiation dosimetry in Hiroshima and Nagasaki, the magnitudes of Cl-36 created in A-bombed granites through a (n,g) reaction have been measured by a means of a tandem accelerator mass spectrometry (AMS). In order to guarantee the reliability of result, three laboratories, Tsukuba, LLNL and Munchen, were involved into this study and measured the samples prepared from the same granites. Though each laboratory uses own developed AMS techniques, the agreement of result is sufficient and the results strongly support a new dosimetry system DS02. It will be reported the details of the Cl-36 AMS and will be discussed about the results. [J Radiat Res 44:383 (2003)]

View full abstract

Measuring of ⁶³Ni (t_1/2 = 100.1 y) produced by fast neutron induced reaction of ⁶³Cu(n,p)⁶³Ni enables us to evaluate the fast neutron fluence even at present. In order to determine the amount of ⁶³Ni produced in an exposed copper sample, we employed liquid scintillation method for the measurement of beta-rays from ⁶³Ni. The copper samples analyzed in this work were two rain gutters collected from Hiroshima University (slant range: 1502 m). The nickel in the copper sample was chemically extracted by electrolysis, solvent extraction and ion exchange methods. The chemical yield was determined to be 60-70% by ICP-AES. As a result, the ⁶³Ni produced in a copper sample exposed by Hiroshima Atomic Bomb was clearly detected by liquid scintillation method for the first time. [J Radiat Res 44:383 (2003)]

View full abstract

Dosimetry system DS86 included detailed calculations of gamma ray dose in individual samples (bricks and tiles) from Hiroshima and Nagasaki that had been measured by thermoluminescence (TL). Measurers took samples from superficial surfaces with a direct line of sight to the bomb, to get doses close to the kerma received by an infinitesimal sample suspended one meter above flat ground ("free-in-air (FIA) kerma"), but the actual in situ/FIA ratio varies. DS86 calculated in situ doses by adjoint Monte Carlo for models of samples and buildings in which they were located, but DS02 lacked resources for new calculations of this type. Therefore we analyzed the ratios calculated for DS86 and developed a method to apply them to the new gamma ray and neutron fluences of DS02 (samples calculated in DS86), and to choose the best estimates for new measurements (samples not calculated in DS86). We explain the DS02 methods and summarize the results. Agreement is good overall and somewhat improved over DS86 in Hiroshima. [J Radiat Res 44:383-384 (2003)]

View full abstract

Since early in 1960's, Japanese groups have performed retrospective gamma dose estimations for the epidemiological studies in the Radiation Effects Research Foundation, by TL measurements of bricks and tiles present in Hiroshima and Nagasaki during the bombings. Such measurements may cover a dose range from a few tens mGy to several Gy. The two most often-used methods are the quartz inclusion (high temperature) technique, and the pre-dose technique. Background dose comes from natural radioactivity in and around ceramic materials, primary the ²³⁵U, ²³⁸U and ²³²Th series, ⁴⁰K and ⁸⁷Rb, and cosmic rays. Since the gamma doses beyond 1km from the hypocenter are very small, evaluation of background radiation is important. Fortunately, the alpha component does not affect high temperature measurements, and its effects on pre-dose measurements has been shown to be negligible. It is concluded that the gamma doses for RERF epidemiological studies should be based on DS02 calculated doses, since the TL measurements support the DS02 up to ground distances of about 1.6 km in Hiroshima and Nagasaki. [J Radiat Res 44:384 (2003)]

View full abstract

An intercomparison study has been made using the same 9 granite atomic-bomb exposed samples in Hiroshima within 1200m ground range and also using liquid standard samples which contained the same amount of Eu and Cl after the irradiation with thermal and epithermal neutrons. The Eu-152 data were obtained at Ogoya, Kanazawa University and the Cl-36 data were obtained at Livermore, Munich and Tsukuba University, respectively. According to this intercomparison study, the results of the Eu-152 and Cl-36 data agree well with not only each other and also with the DS02 calculation except for two higher data. The deviation between Eu-152 and Cl-36 for granite samples are within 14%, and for liquid standard samples are within 9%. This shows that consistency in each measured datum and new dosimetry system within 1200m. [J Radiat Res 44:384 (2003)]

View full abstract

The calculation system used to develop DS02 has the same structure as DS86. DS02 can be considered a graded-up version of DS86, reflecting the progress of computer capacity and the refinement of nuclear cross section data during the past about 15 years. The main feature of the DS calculation system is that it is composed of replaceable modules for each step of dose evaluation. Main modules are divided into four parts: source terms, air-over-ground transport, shield effects and organ dose factors. Through the efforts to develop DS02, the first two modules (source terms and air-over-ground transport) of DS86 were replaced with new ones. Ionizing radiation from atomic bombs is categorized into prompt components (prompt gamma, prompt neutron, prompt secondary gamma) and delayed components (delayed gamma, delayed neutron, delayed secondary gamma). All these components in Hiroshima and Nagasaki were reevaluated using new source terms and air-over-ground transport calculations. The results of gamma and neutron fluence above the non-shielded ground are passed to the shield effects module and the organ factor module to reevaluate radiation dose for the survivors. [J Radiat Res 44:384 (2003)]

View full abstract

Dosimetry system for atomic bomb radiation; DS86 issued in 1986 had been discussed for log years. There exist discrepancies of measured residual activities and calculations at the short- and also long-ranges. From 2000, Japan and US joint workshop has been held, and reassessment was started to improve the dosimetry system. As the results of the works, consensus was obtained for the evaluations, and the new dosimetry system DS02 has been issued through the senner committee. In the DS02, higher cpu machine (~10Tflops) has been used for calculations, and precise calculation of which calculating memory increased to about 100 times, has been performed. And also, the cross section data libraries were improved from ENDF/B5 to the newer ENDF/B6.2. The burst height and output of the atomic bomb are re-evaluated using the calculation results and the measurement data. As the results of this evaluations, differences between DS86 and DS02 are shown to be less than 20%. However, the reproducibility of the measured data, especially at the short range, is quite improved. Some comparisons of DS02 with DS86 will be presented in this talk. [J Radiat Res 44:384 (2003)]

View full abstract

A new dosimetry system (DS02) has been developed for use in the computation of atomic bomb survivor dose estimates after a 15-year multinational effort. It is based on new energy- and angle-dependent gamma-ray and neutron fluences at distances up to 2500 m from the hypocenters. The changes reflect changes in the height and yield of the Hiroshima bomb, improved air and material cross-sections, improved transport models, and more powerful computers. It features improved methods for characterization of shielding, including shielding by terrain features not previously considered, houses or wooden schools, and light factories in Nagasaki. For the use of survivor doses at Radiation Effects Research Foundation, staff are responsible for modification and testing of the dose estimation codes of the DS02 system, development of methods to provide dose estimates for survivors beyond 2,500m from the hypocenter, and extraction of additional shielding information from original survivor records. In this talk we outline the key features of RERF's implementation of the DS02 system and summarize the nature of changes in survivor dose estimates. [J Radiat Res 44:385 (2003)]

View full abstract

After a 15-year multinational effort, the system (DS86) used to compute dose estimates for individual survivors has been replaced by a new system (DS02). Although motivated by concerns about discrepancies between measured and calculated neutron activation values, the new system also incorporates improved radiation-transport models; uses newly coded information on shielding by houses, factories, and schools; and allows for shielding by terrain features not taken into account in earlier survivor dosimetry systems. While the changes in neutron dose estimates are less than has been suggested in some reports, the changes in dose estimates will affect risk estimates to some extent.We use the DS02 and DS86 dose estimates to investigate the impact of the change in dosimetry using data on about 10,000 solid cancer and 300 leukemia deaths among 86,600 atomic bomb survivors in the Life Span Study cohort between 1950 and 2000. We compare overall risk estimates and inferences about low dose risks, describe the nature of age-time patterns, and consider the magnitude and nature of differences between Hiroshima and Nagasaki risk estimates. [J Radiat Res 44:385 (2003)]

View full abstract

In 1995, there found as much as 500, 000 tons of illegal industrial waste in tiny island, Teshima in Seto inland sea. The waste included lead, cadmium, dioxin, arsenic, trichloroethylene, mercury and so on. One of the strangest facts is that these environmental hazards decrease heme concentoration; i.e., lead, dioxin, and trichloroethylene inhibit heme biosynthesis whereas arsenic, cadmium, mercury, and dioxin accelerate heme degradation. Why should they decrease heme level? Functions of heme are well known as prosthetic group of oxygen-related proteins, such as hemoglobin, myoglobin, cytochrome P450, and other cytochromes. Oxygen itself also affects heme metabolism, suggesting a common effect of environmental hazards and oxygen on lives. Since we recently found a novel heme protein, Bach1, which regulates many genes, biological significances of reduced heme concentration will be discussed in this presentation. [J Radiat Res 44:385 (2003)]

View full abstract

Rreactive oxygens (ROS) and nitric oxide (NO) are important for aerobic life and the etiology of various diseases. We hypothesized that overflow of free electrons from mitochondria is the critical cause for ROS generation. Kinetic analysis revealed that mitochondrial generation of ROS was enhanced either by respiratory substrates and Ca2+ or by electron transport inhibitors particularly under high energy status and that the generated ROS oxidized the critical SH of adenine nucleotide translocase to release ctochrome c, thereby stimulating the process of apoptosis. Targetting carnitine or SOD markedly inhibited the oxidation of the critical SH and the release of cytochrome c. Thus, ROS generated by perturbed mitochondria determins the fate of cells and tissues. ROS and/or NO impaires DNA in symbiotic bacteria and their hosts; the former enhances the mutation that accelerates their evolution while the latter enhances the process of aging and carcinogenesis. Based on such findings, critical roles of mitochondria and ROS/NO in the mechanism of evolution, life, aging and age-associated diseases will be discussed. [J Radiat Res 44:385 (2003)]

View full abstract

"Depleted uranium" is a low-level radioactive material produced in the process of enrichment of natural uranium for the purpose of nuclear weapons or nuclear energy. Compared to natural uranium, depleted uranium contains a lower percentage of U-235 and a higher percentage of U-238. Still, it has 60% radioactivity of natural uranium in addition to chemical toxicity. However, only the limited information is available as to the nature of depleted uranium which is actually being used by the military. Due to uranium's high density and heavy weight, the military finds it valuable to use depleted uranium as artillery shell penetrators and tank armors. When depleted uranium penetrators hit hard targets like tanks, they will dissolve into aerosol particles. What is feared is that human beings inhale aerosol particles in the air. When inhaled or swallowed into a human body, most of uranium will eventually be excreted. Nevertheless, some may reach the kidney through blood to make serious damage. The insolvable form of uranium will remain in the body for a long period by increasing a risk of internal radioactive toxicity. [J Radiat Res 44:386 (2003)]

View full abstract

The author will discuss on "What did the investigators on environmental radioactivityleave behind?". Discussions will be concentrated on behavior of artificial radionuclides in the atmosphere and ocean.Two distinctive feature of radionuclides, no artifical radionuclides exist before the 20th century and specific half-life of each radionuclide, has been working as tracers in the meteorology and oceanography. Many new findings on these fields obtained by means of tracer use of radionuclides by investigators in these field. On the other hand, investigators of environmental radioactivity had concentrated their interest in restricted fields of their own. The investigators leave some basic and important issues those should be solved. For example, it is commonly used that the 137Cs/90Sr activity ratio in the fallout is 1.6, however, this ratio should vary depending on the type of the explosions. The global inventory of artifical radionuclides such as 90Sr was estimated only from land base measurements. Advection and diffusion works much in the ocean, however, previous discussions on the inventory of artifical radionuclides in the ocean sometimes neglect these effect. [J Radiat Res 44:386 (2003)]

View full abstract

The human health risk due to the prolonged exposure to the low-level radioactive and non-radioactive materials in an environment is now to be evaluated based on the quite the same procedures especially in the cell and molecular (DNA) level. This suggests that the risk evaluation studies for the radioactive and non-radioactive pollutants might be crossed over for mutual benefit in the preventive risk-based management of environmental micro-pollutants based on the common framework. [J Radiat Res 44:386 (2003)]

View full abstract

Organotin compounds, such as tributyltin (TBT) and triphenyltin (TPT) have been used worldwide in antifouling paints for ships and fishing nets since the mid-1960s. These organotins have caused severe contamination in the marine environment, because of low rate of decomposition by bacteria and remarkably high accumulation in marine organisms. TBT and TPT are very toxic to organisms, and also known as environmental hormones (endocrine disrupters). Gastropods imposex is accepted to be typically induced by very low concentrations of TBT and/or TPT in the marine environment. The authors have studied the Japanese gastropod imposex as well as organotin contamination in the inshore waters of Japan since 1990, in terms of the current status and mode of action of organotins. Here, the results on our field studies concerning the current status of the Japanese gastropod imposex and organotin contamination in the inshore waters of Japan will be summarized. Results on laboratory experiments to reveal the mode of action of organotins will be also presented, indicating a new hypothesis about induction mechanism of imposex in gastropods. [J Radiat Res 44:386 (2003)]

View full abstract

Purpose: We analyzed intermediate risk factors in ophthalmologic study of A-bomb survivor. Subjects: The AHS participants who were age 13 or less at the time of the bombs and those who had the previous ophthalmologic examination during 1978-1980. Methods: Slit lamp examination, digital photograph, and classification by the Lens Opacity Classification System. We selected items statistically significant both with radiation dose and cataract from ophthalmologic findings, 23 cataract related questionnaires and 15 clinical laboratory tests. Results: During the period, 873 persons underwent the ophthalmologic examination. Statistical significance in dose response was observed in cortical and posterior subcapsular opacities, but not in nuclear color and nuclear opacity. Inflammation and calcium were found to be significant as intermediate risk factors. Conclusion: Thus, presence of intermediate risk factors in A-bomb survivors strongly suggests a presence of indirect effects in radiation cataractogenesis. [J Radiat Res 44:387 (2003)]

View full abstract

We examined the correlation between lifestyle and mortality on the basis of health survey interview which 3831 Nagasaki A-bomb survivors underwent in 1997. Items asked at interview were: activities of daily living (ADL), living with family, recollection of atomic bombing, worry about health, relatives' death, visit by friends, socializing with neighbor, club member and mental health. Mental health conditions were assessed by 30-item version of General Health Questionnaire. Among 3700 who completely responded, 408 died from 1 August 1997 to 31 January 2003. It was observed that mortality was significantly correlated with ADL, socializing with neighbor, club member and mental health after adjustment for sex and age, and that mortality in those with poor ADL was 1.94-fold higher than those with better ADL. [J Radiat Res 44:387 (2003)]

View full abstract

We compared cancer mortality between two groups of Nagasaki A-bomb survivors; one group was bombed in area shielded by Mt. Kompira(366 meter-high) and Mt. Gosha(285 meter-high) located east and east-south at about 2.5 km from the hypocenter, respectively, while the other was bombed in unshielded area in the south at a similar distance from the hypocenter. Cancer mortality during 1970-2001 in 2345 survivors bombed in the unshielded area was 1.51-fold (95%CI: 1.20-1.89) higher than that in 2340 bombed in the shielded area after adjustment for sex, age, distance and shielding. The results suggest that the survivors bombed in the shielded area were less irradiated than those bombed in the unshielded area. [J Radiat Res 44:387 (2003)]

View full abstract

We have recently found that A-bomb survivors exposed in utero recorded practically no chromosome damage induced by radiation exposure. To investigate the mechanisms, we irradiated pregnant mice (B6C3F1) at day 15.5 pc with 2Gy of X rays, and translocation frequencies were examined at 18-21 weeks after birth using FISH painting of chromosomes 1 (yellow) and 3 (red). We scored 800 metaphase cells in each tissue from each animal; T lymphocytes from peripheral blood (PB) and spleen (SP), and bone marrow cells (BM). We found that genomic translocation frequencies in the mothers were about 25% (PB), 20% (SP), and 10% (BM). In contrast, about half of the offspring showed no translocations, and the remaining animals had the frequency of only about 5%, in which several clonal translocations were detected. The results confirmed our previous observations in A-bomb survivors exposed in utero, and we propose that fetal lymphoid precursor cells undergo elimination when damaged by irradiation, probably through apoptosis. We expect that future studies using genetically manipulated mice will clarify the mechanisms. [J Radiat Res 44:387 (2003)]

View full abstract

We have already reported that plasma levels of IL-6, which is an inflammatory cytokine, and CRP, which is induced by IL-6, increase with increasing radiation dose among A-bomb survivors. In this study, usual levels of plasma pro- and anti-inflammatory cytokines (TNF-alpha, IFN-gamma, and IL-10) of A-bomb survivors were measured to evaluate the late effects of radiation on inflammatory status of A-bomb survivors. The TNF-alpha levels appeared to increase with increasing age and radiation dose. The IFN-gamma levels increase with radiation dose, but not with age. The anti-inflammatory cytokine IL-10 levels also increase with age and radiation dose, but the increasing rate of the anti-inflammatory cytokine was lower than that of the pro-inflammatory cytokine. These results indicate that there are certainly elevated inflammatory signs among A-bomb survivors even now, more than 50 years after their radiation exposure. Such changes may play a role in some of the excess inflammatory disease, such as myocardial infarctions, that the survivors experience. [J Radiat Res 44:388 (2003)]

View full abstract

[PURPOSE] We examined aspects of the multistage frailty models for carcinogenesis. [METHODS] We see that the generalized Armitage-Doll model, which can examine the age-, dose-, and age-at-exposure- dependent effects of external exposure to a carcinogen, do not, because of various unobserved factors, account for population heterogeneity. Thus we developed multistage frailty models that assume that population heterogeneity may come from either different sensitivities to exposure or different background cancer risks, and that frailty distributions are gamma and inverse-Gaussian distributions. Using these models, we demonstrated how population heterogeneity affects estimates of model parameters, particularly excess risks of cancer. [EXAMPLE] We reanalyze a solid cancer incidence data set of atomic bomb survivors exposed before they were 40 years old, and we assess the magnitude of population heterogeneity, the excess absolute and relative risks of solid cancers from exposure to a 100-millisievert colon dose, and the goodness of fit of the models. [CONCLUSION] We see that the multistage frailty models are useful for understanding the time course of carcinogenesis with effects of exposure and unobserved heterogeneity factors in epidemiologic data. [J Radiat Res 44:388 (2003)]

View full abstract

The catalase activities in blood and organs of the acatalasemic (C3H/AnLCsbCsb) mouse of C3H strain are lower than those of the normal (C3H/AnLCsaCsa) mouse. We examined the effects of prior low dose (0.5 Gy) X-ray irradiation reducing the oxidative damage under carbon tetrachloride (CCl₄)-induced hepatopathy in the acatalasemic or normal mice. The acatalasemic mice showed a significantly lower catalase activity and a significantly higher glutathione peroxidase activity compared with those in the normal mouse. Moreover low-dose irradiation increased the catalase activity in the acatalasemic mouse liver to the similar level to that of the normal mouse liver. Pathological examinations and analysis of blood GOT and GPT activity and lipid peroxide levels showed that CCl₄-induced hepatopathy was inhibited by low dose irradiation. These findings indicate that the free radical reaction induced by the lack of catalase and administration of CCl₄ is neutralized by high glutathione peroxidase activity and low dose irradiation in the acatalasemic mouse liver, and this relieved dysfunction at least in the liver of mice. [J Radiat Res 44:388 (2003)]

View full abstract

A derivative of murine immortal NIH/PG13Luc cells stably transfected with p53-dependent luciferase reporter plasmid was used for detection of transcriptional activity of p53 in response to radiations. This cell line was sensitive enough to detect p53 response to low dose rate γ-ray irradiation (ranging from 0.1-5 cGy/h for ⁶⁰Co γ-rays) as well as to acute X-ray. The cells irradiated by low dose rate γ-ray (1 cGy/h at 72 h, and 5 cGy/h at 72 h) undergo growth arrest that was correlated with p53-mediated CDKN1A/p21 up-regulation. Microarray analysis showed up-regulation of seven p53-mediated genes, CDKN1A/p21, MDM2, SIP27, CCNG1/cyclin G1, EI24/PIG8, POLK, and BAX, at 1 to 10 cGy/h exposure: CDKN1A/p21 and CCNG1/cyclin G1, were significantly increased at more than 1 cGy/h, whereas MDM2 and BAX showed increase at more than 10 cGy/h exposure. Taken together, the data suggested that cells show differential response to the different doses of radiation and involve more than one pathway. (This work was supported by Aomori Prefecture, Japan.) [J Radiat Res 44:388-389 (2003)]

View full abstract

There has been a recent upsurge of interest in radiation-induced bystander effects. Previously we reported that the accumulation inducible nitric oxide synthase (iNOS) was induced only in human glioblastoma mutant (m) p53 cells by acute irradiation with X-rays. In the present study, we found that the accumulation of iNOS in wtp53 cells was induced by chronic irradiation with gamma-rays followed by acute irradiation with X-rays, but not by each one. It is suggested that the accumulation of iNOS may be due to the depression of acute irradiation-induced p53 functions by pre-chronic irradiation. We found that chronic irradiation with gamma-rays did not inhibit the accumulation of p53 after exposure to the conditioned medium from the irradiated mp53 cells. However, the decay of accumulated p53 was stimulated by chronic irradiation with gamma-rays. At the same time, the accumulation of Hdm2 was observed, suggesting that chronic irradiation with gamma-rays may stimulate the degradation of p53 accumulated by NO-mediated bystander effects. [J Radiat Res 44:389 (2003)]

View full abstract

We have reported that pre-irradiation with a small dose (0.3-0.5 Gy) induces radio-resistance observed as an increased survival rate from bone marrow death in ICR and C57BL/6 mice. This was also observed in splenectomized C57BL/6 mice, and the lifespan of pre-irradiated group after observation of bone-marrow death rate was significantly longer than that of non-pre-irradiated control group. In this study, lifespan of intact (without splenectomy) mice was examined. The 30-day survival rates of pre-irradiated and non-preirradiated control animals were 96% (48/50) and 58% (29/50), respectively. Increment of the survival rate was significant (Fisher's exact probability=0.0000035). Lifespan of the survived 48 (pre-irradiated) and 29 (control) animals were observed. The average survival time (and its standard error) was 347.3 (29.8) days for pre-irradiated group and 378.9 (40.9) days for control group. The difference of the lifespan was not significant both in generalized Wilcoxon's rank sum test (p=0.55) and log rank test (p=0.32). [J Radiat Res 44:389 (2003)]

View full abstract

It is considered that induction of the GADD45 gene after X-ray irradiation is p53-dependent, requiring binding of p53 to the p53-recognition element in the third intron. However, it is not understood whether additional transcription factors (TFs) other than p53 are required for transcriptional regulation of the GADD45 gene after X-ray irradiation. We have previously revealed X-ray-inducible binding of factors at several loci in the regulatory region of the GADD45 gene in ML-1 cells. Among them, we focused on the locus, spanning -793 / -759 bp in the upstream region of the GADD45 gene, where binding of factors is induced after 0.5 Gy of X-rays irradiation. Although this locus is homologous to the consensus recognition sequences for TFs, GATA, Ikaros, and IRF, EMSA using competitor oligonucleotides revealed an association of none of these TFs. By introduction of point mutations into the probe, we revealed that this X-ray-inducible factor binds to the -775 bp / -759 bp region. [J Radiat Res 44:389 (2003)]

View full abstract

Radioadaptive response is a biological defense mechanism that is induced by low-dose ionizing irradiation for cellular resistance to the genotoxic effects of subsequent irradiation. The response is the acquisition of resistance to the induction of mutation, chromosome aberraion, and cell killing by ionizing radiation. We have shown that the radioadaptive response is mediated through the pathways involving protein kinase C and p38 mitogen-activated protein kinase. However, its molecular mechanism is still largely elusive. We examined mutations induced by ionizing radiation with or without radioadaptive response at the Hprt locus in mouse m5S cells. We analyzed the Hprt gene in 6-thioguanine-resistant mutants by amplification of all the nine exons of the mouse Hprt gene. Our results showed that the proportion of partial deletions was much higher in mutants isolated from the pre-exposed radioadaptive culture than in non-primed irradiated culture. [J Radiat Res 44:389-390 (2003)]

View full abstract

The suppression of Methylcholantholene(MC)-induced tumor by low dose-rate gamma irradiation has been reported in 44th annal meeting. However, it's not known how the low dose-rate radiation suppressed the appearance of MC-induced tumor. Here, we investigated the fluctuations of TD50 values in irradiated mice at low dose-rates to elucidate the mechanism of the suppressive effects. Irradiations were performed with Cs-137 gamma-rays at 1.0 mGy/hr or 0.30 mGy/hr for 1-8 weeks before tumor cell injection. Mice were injected with an appropriate number of cells prepared from MC-induced tumor. The results indicate that TD50 values in mice irradiated at 1.0 mGy/hr for 1-3 weeks were almost 1.5 times higher than in non-irradiated mice, and higher TD50 value was also shown in mice irradiated at 0.30 mGy/hr for 1-5 weeks. The change in TD50 values is considered to be reflected tumor immunological conditions; therefore, the results obtained in the present study may suggest that the low dose-rate radiation enhances tumor immunological capacity in the irradiated mice. [J Radiat Res 44:390 (2003)]

View full abstract

The daf-16 gene encodes a forkhead transcription factor that presumably regulates the downstream target genes in an insulin-like signal pathway. It is still unknown what genes are regulated by DAF-16, but at least some genes related anti-oxidation are expected, because daf-2 mutants are resistant to oxidative stress and a daf-16 mutation suppresses this phenotype. The daf-16 mutant itself is also sensitive to oxygen. We examined what anti-oxidant enzymes are regulated by DAF-16. Furthermore, we analyzed a transcriptional profiling of daf-16(m26) allele using an expressed sequence tag (EST) microarray experiments to detect the target genes of DAF-16. As the result, the change of the expression level of a few anti-oxidant genes was found in daf-16(m26) mutants, e.g., the levels of a microsomal catalase (ctl-2), a metallothionein gene (mtl-1) and lysosomal protease genes were decreased. These suggest that anti-oxidant proteins are strong candidates in the downstream target genes regulated by the DAF-16 transcription factor. [J Radiat Res 44:390 (2003)]

View full abstract

We previously found that the suppressive effect of 0.5 Gy gamma rays irradiation on transplantation tumor growth in mice. To investigate the mechanisms of anti-tumor immune enhancement by low dose irradiation, in this study we examined the polarization of Th1/Th2 cytokine balance in splenocytes and peritoneal macrophages. Interferon (IFN)-gamma / interleukin (IL)-4 ratio produced by splenocytes of tumor-bearing mice was significantly increased by 0.5 Gy gamma rays irradiation. The capability to produce IL-12 upon IFN-gamma plus LPS stimulation of peritoneal macrophages from irradiated mice was also significantly increased. These results suggest that 0.5 Gy gamma rays activate cell-mediated immunity through Th1 predominance, resulting in the suppression of tumor growth. [J Radiat Res 44:390 (2003)]

View full abstract

Germ-line mutation induced by ionizing radiation is suspected as a cause for the increased risk of developing cancers in successive generations. Two conflicting results, the negative one on the first-generation progeny of the atomic bomb survivors at Hiroshima and Nagasaki and the positive one among the human population in the Belarus area after the Chernobyl accident, have been reported for the effect of ionizing radiation on germline mutation in human populations. The mouse specific locus test has been successfully applied to evaluate the genetic effects of radiation. However, the frequencies of spontaneous mutation have varied in different series of experiments, suggesting that the number of mice used in the test was not sufficient for a statistical analysis. Therefore, we started to establish a new experimental system to detect germline mutation at the molecular level using the automated DNA sequencer. We will present the results and the reliability of our experimental system. [J Radiat Res 44:390-391 (2003)]

View full abstract

We have developed a new technique for geneexpression profiling called HiCEP. This method can analyze approximately80% of the genes that are expressed in a cell sample. A peak profilegenerated by HiCEP analysis represents the complete pattern of geneexpression in a sample under given conditions. Comparisons betweenprofiles made under different conditions (time after treatment, knock-outanimals etc) have revealed many new genes in our laboratory.HiCEP is different from other expression profiling methods in that it doesnot require any sequence information prior to the analysis, it is sensitiveand its results are highly reproducible. We are now building a database ofHiCEP peaks that will allow us to quickly identify the gene correspondingto a given peak. One such database based on expression profiling data of amouse embryonic stem cell line will be made available to the public soon.This kind of database should be useful in biological research on geneticdeficiencies, changes in response to the environment etc. [J Radiat Res 44:391 (2003)]

View full abstract

The radiosensitive mutant LX830, a derivative of the mouse leukemia L5178Y cell, is defective in DNA double-strand break rejoining ability. This cell line belongs to the XRCC4 deficiency group. LX830 cells were hypersensitive to cell killing and mutation induction by gamma rays compared to the parental cells. No dose-rate dependence was found for mutation induction in this cell line. To characterize the structural alterations at the Hprt locus in LX830 cells, we have developed the primer sets for multiplex PCR analysis of the gene. The cells were employed after the removal of pre-existing 6-thioguanine resistant (TG^r) mutants by THMG (Thymidine-Hypoxanthine-Methotrexate-Glycine) treatment. Independent TG^r mutant clones were isolated from unirradiated and gamma-irradiated cultures of both LX830 and L5178Y cells. The proportion of mutants with deletions, together with the size and distribution of deletions are determined by the multiplex PCR method. How the deficiency of XRCC4 protein affects the molecular nature of TG^r mutants will be discussed. [J Radiat Res 44:391 (2003)]

View full abstract

An exposure condition of tritium radiation from nuclear fusion reactor could be a long-term exposure with low dose rate. The biological effects of low dose (rate) radiation are not clear because any suitable detection system has not been established. Regarding to mutation induction by high LET radiation such as neutrons, the reversed dose rate effect has been reported when the dose rate is lower than a certain value. This might be caused by hypersensitivity of G2/M phase population to mutation induction by high LET radiation. However, it is not clear whether this phenomenon could be seen in the case of tritium radiation. To examine the low dose rate effect of tritium, we established a hypersensitive mutation detection system using hamster cells carrying a human X-chromosome. We have tested mutation induction by tritiated water at dose rate between 0.18 and 4.4 cGy/h. Our results suggest that mutation frequency seems to be slightly increased at lower dose rate. [J Radiat Res 44:391 (2003)]

View full abstract

The effects of low-dose X-irradiation on lens and forelimb regeneration in the newt were examined. Newts were subjected to sham or whole-body X-ray exposure at a dose of 0.05, 0.2 or 0.4Gy, delivered at a rate of 0.43Gy/min. On day 14 after lens removal, unexposed animals showed the formation of a hollow epithelial vesicle of depigmented cells continuous with the laminae of the iris (stage II). In contrast, lenses from newts exposed to a 0.2Gy dose X-ray showed some formation of the primary lens fiber nucleus (stage III-early). Furthermore, an acceleration from stage II to III-early was also found on day 14 following irradiation of only the upper belly, including the spleen. Interestingly, well regeneration could be observed on forelimb stage. On 6 weeks after amputation, unexposed animal was showed the assembly of the condrogenesis of the radius and ulna. In contrast, forelimb from newts exposed to a 0.2Gy spleen portion was showed the onset of digit formation. [J Radiat Res 44:391 (2003)]

View full abstract

The effects of low-dose rate gamma irradiation on C57BL/KsJ-db/db mice with Type II diabetes mellitus were investigated. A group of 12 female 10-week old mice were irradiated at 0.70 mGy/hr of gamma rays in our low dose rate irradiation facilities. The urine glucose levels of all of mice were strongly positive at the beginning of the irradiation. In the irradiated group, a decrease in the glucose level was observed in three mice. No recovery from the diabetes was observed among 12 mice of the non-irradiated control group. Mortality was delayed and healthy appearance was prolonged in the irradiated mice by about 20 weeks compared with the control mice. A marked difference was also observed in the appearance of the coat hair, skin and tail. The irradiated group was in much better condition. These results suggest that low-dose rate irradiation modified the condition of the diabetic mice, leading not only to recovery from diabetes, but also to suppression of aging process. [J Radiat Res 44:392 (2003)]

View full abstract

The radon effects and the thermal effects were biochemically compared under the condition with the similar chemical component, using as the parameters which are closely involved in the clinical for radon therapy. In the results, the radon and thermal therapy enhanced the antioxidation function, such as the activities of SOD and catalase, which inhibit lipid peroxidation and total cholesterol produce in the body. Moreover the therapy enhanced ConA induced mitogen response, and increased the level of CD4, which is the marker of helper T cell, and decreased the level of CD8, which is the common marker of supresser T cell. Furthermore, the therapy increased the levels of ANP, endorphin, ACTH, insulin and G-6-PDH, and decreased the vasopression level. The results were on the whole larger in the radon group than in the thermal group. The findings suggest that the radon therapy more contributes to the prevention of life style-related diseases related to peroxidation reactions and immune depression than thermal therapy. [J Radiat Res 44:392 (2003)]

View full abstract

Although linear non-threshold (LNT) is a basic theory for radioprotection, adaptability of LNT to biological responses at low dose/low dose-rate is not sufficiently investigated. In this study, we acquired quantitative data at low dose/low dose rate with statistically sufficient accuracy, using micronucleus formation of human osteosarcoma. These data were plotted on the coordinate of linearly scaled response and dose. The results followed to the straight line passing through the origin of the coordinate axes between 0.1-5 Gy when cells were irradiated for 1-10 min. The increase in binuclear cells bearing micronucleus was statistically significant at the dose above 0.1 Gy. In contrast, dose response curves never followed LNT and statistical significance was obtained at the doses above 6 Gy when cells were irradiated for 7 to 124 days. These results suggest that dose response curve of biological reaction is remarkably affected by exposure time, and that dose rate effect changes as a function of dose-rate and irradiation time. [J Radiat Res 44:392 (2003)]

View full abstract

Low dose radiation is reported to have beneficial effects such as attenuation of diabetes, auto-immune diseases, and cancer, which is called radiation hormesis. Because the disorder of accommodation in immune system is involved in such diseases, immunological network is assumed one of the targets for radiation hormesis. In this study, C57BL/6 mice (H-2^b) were continuously exposed to gamma-ray at 97 microGy/h, intraperitoneally immunized with an allogeneic mastocytoma, P815 (H-2^d), 98 h after the initiation of the irradiation. They were further irradiated for 335 h. We found that antigen-specific killer T cell activity, anti-P815 IgG₁ titer, and cytokine production of T cells including IL-2, -4 and -10, were significantly enhanced by the irradiation. In addition, T cell population in spleen and production of IL-2 and -4 were significantly elevated in naive mice irradiated with the same schedule, while natural killer activity, and production of IL-10 and interferon-gamma decreased. These results suggest that the enhancement of T cell-mediated immunity is involved in the hormetic effects of low dose-rate irradiation. [J Radiat Res 44:392 (2003)]

View full abstract

We established a technique based on single cell gel electrophoresis (comet assay) to detect DNA damage in mouse spleen cells induced by low dose of ionizing radiation. C57BL/6N female mice, 6-week old, were irradiated with 0.5Gy of X-rays at 1.6Gy/min or ¹³⁷Cs gamma-rays at 1.2mGy/hr. After the irradiation, spleen of the mouse was removed and cell suspension prepared. The amount of DNA damage was measured by the comet assay. The amount of DNA damage of the low dose rate irradiation was smaller than the high dose rate irradiation ; however, it was slightly larger than that in control mice. [J Radiat Res 44:393 (2003)]

View full abstract

It is known that the negative ions are produced by the waterfall electricity (Lenard effect), by the lightning or corona discharge (electric effect), and by the radon hot springs (radiation effect). The medical effects by the negative ion are similar to the effects of radon therapy, such as for the enhancement of the elimination of the active oxygen. Accordingly, we studied on the relationship between the radioactive minerals for radon therapy and the negative ion. The standard gamma-ray sources (¹³⁷Cs, ⁶⁰Co) and the radioactive minerals are prepared to measure the charge distribution around the samples using the negative ion counter. In the results, the negative ions were not detected from the standard gamma-ray sources but detected from the radioactive minerals. Moreover, the negative ions were not detected from the radioactive minerals with the shield of alpha rays. The findings suggested that alpha rays could be contribute to the production of the negative ions. [J Radiat Res 44:393 (2003)]

View full abstract

To investigate molecular mechanisms of biological responses to low-dose-rate gamma-irradiation, we examined the modulation of gene expression following low-dose-rate gamma-irradiation. Methods: Human acute lymphoblastic leukemia cell line MOLT-4 was irradiated using the long-term low-dose-rate irradiation facility at CRIEPI with a ¹³⁷Cs source at a dose rate of 1.1 mGy/hr. RNA was extracted from irradiated and sham-irradiated cells, and gene expression was measured by real time reverse transcriptase PCR method using primers and internal probes for p21^waf1, GADD45, Bax and p53 genes. Results: We found that the level of p21^waf1 gene expression increased after more than 1-day irradiation, reached a plateau (about 1.4-fold) at about 1 week and continued at the plateau to at least 91 days. The levels of GADD45 and Bax gene expression also increased slightly, but the level of p53 gene expression did not. No effects on cell growth and cell cycle were obserbed. [J Radiat Res 44:393 (2003)]

View full abstract

We have been investigating effects of low-dose-rate radiation (LDR) on immortal human cells established by introducing the hTERT gene. GI-phase-arrested AT and normal cells were irradiated by LDR (0.3mGy/min) continuously for a maximum of 2 weeks and high-dose-rate radiation (HDR; 2Gy/min). In normal human cells, the survival after LDR irradiation was significantly high, while the induction of micronuclei was significantly low, when compared to those after HDR irradiation. In contrast, in AT cells significant difference between LDR and HDR were not observed. Meanwhile, gH2AX foci formation was not observed in both non-irradiated and LDR irradiated normal cells, while in AT cells significant number of gH2AX foci were induced after LDR irradiation. These results suggest that, in AT cells, a repair system of the DNA double-strand breaks may be defective at least in GI phase. [J Radiat Res 44:393 (2003)]

View full abstract

Five-week or life-long low dose-rate gamma-radiation at 0.35 or 1.2 mGy/hr prolonged the life span of MRL-lpr/lpr mice carrying deletion in the apoptosis-regulating fas gene that markedly shortens life. All of non-irradiated control lpr mice died by 20 weeks of age. All mice of 0.35 mGy/hr irradiated group survived until the same age. All mice of 1.2 mGy/hr group survived until 24 weeks of age. In the 5-week irradiated group, immunologically important CD8⁺ T cells increased to 180% of non-irradiated group, while autoreactive CD3⁺ CD45R/B220⁺ cells and CD45R/B220⁺ CD40⁺ cells, characteristic of the autoimmune disease, decreased significantly compared with non-irradiated group, and the decreases were dependent on the dose rate. The percentage of mice with lymphadenopathy decreased from 80% (control) to 10% (0.35 mGy/hr) or 0% (1.2 mGy/hr). The percentage of mice with proteinuria decreased from 80% (control) to 40% (0.35 or 1.2 mGy/hr). Suppression of brain damage was also found in parallel with these curative effects by chronic low dose-rate irradiation. [J Radiat Res 44:393-394 (2003)]

View full abstract

We measured the growth rates of various primary human fibroblasts under very low levels of high LET particles. This was performed using an incubator and a radiation detector located in the HIMAC biology beam room. NHEJ deficient 180BR cells (Ligase IV mutant) showed an immediate growth delay after about 10mGy accumulated exposure (6days) while there is no clear delay in normal as well as ataxia telangiectasia (AT) cells for more than 50 days. 180 BR cells in the HIMAC incubator also showed an accelerated senescence. These phenomena indicate the involvement of NHEJ proteins in the cell growth control. In order to access damage caused by low level high LET radiation, we have compared cell growth between cells exposed to 0.1Gy carbon particles (LET=80keV/um) and cells exposed to 0.1Gy X-rays. A significant growth delay was observed in normal cells irradiated with carbon ions for the first 5 days while much less delay was seen in cells with X-rays,suggesting that the damage by high LET is severer than by X-rays. [J Radiat Res 44:394 (2003)]

View full abstract

Significant survival reduction was not observed at the lung dose of 0.16 Gy, but was correlated with early increase of lung carcinomas at the doses over 0.45 Gy after inhalation exposure of female Wistar rats to alpha-emitting plutonium (Pu) dioxide aerosols. These carcinomas were 70-80% among all the primary lung tumors, increased in a dose-dependent manner over 0.45 Gy, reaching the plateau of 90% at 6.6-8.5 Gy. As compared to the dose response curve for lung carcinomas from thoracic X-irradiated rats, the slope of the fit linear equation and the relative effectiveness for 50% incidence of carcinomas were approximately 11-times as high in Pu-exposure as those of thoracic X-irradiation. Microscopic numbers of lung tumor lesions were about 2-fold more in Pu-exposure, while the proportions of histopathological types were almost similar between Pu-exposure and X-irradiation. These results indicate that relative effectiveness for pulmonary carcinogenesis is greater in Pu-exposure than X-irradiation, whereas lung tumor types appear to originate from the same target epithelial cells. [J Radiat Res 44:394 (2003)]

View full abstract

An epithelial cell line (PuD2) was established from the lung of rat exposed to plutonium dioxides. Transplantation of the PuD2 cells into nude mice resulted in the formation of nodules with a diameter of 12-15 mm in two weeks. Several respiratory tract epithelial cell lines established from normal rats were also transplanted to compare tumorigenicity at different stages of cell growth. Although virus-immortalized SV40T2 cells and gamma ray-induced and transformed RTiv3 cells could not be transplantable, benzo [a] pyrene-induced BP, BP(P)Tu, BP130 and BP270 cells formed nodules three weeks after the transplantation. The second transplantation of these BP cell lines resulted in a rapid growth within two weeks. These results indicate that the tumorigenicity of respiratory tract epithelial cell lines is dependent on their different stages of the carcinogenic processes from the initiation through promotion and leading to the progression. Their association with chromosomal aberrations and/or genetic alterations is under investigation. [J Radiat Res 44:394 (2003)]

View full abstract

We characterized highly radioresistant thymocytes as a candidate of p53-/- thymocytes, because the enrichment of p53-/- thymocytes by a high dose of irradiation could be expected from the facts that p53+/- thymocytes are sensitive to radiation-induced apoptosis but p53-/- thymocytes highly resistant. At various times post irradiation (6Gy), p53 heterozygous B10 mice were treated with a high dose (30Gy) of irradiation to enrich p53-/- thymocytes and, 24 hours later, the remaining thymocytes assayed for surface marker and p53 genotype. In a significant fraction of the mice 7wks after 6Gy-irradiation, we observed an abnormal increase of relative cell number of CD4⁺CD8⁺ thymocytes remaining in the thymus of highly irradiated mice and such abnormal thymocytes could be detected even 5 weeks after the irradiation. The abnormal CD4⁺CD8⁺ thymocytes were shown by PCR analysis of sorted cells to contain cells with p53-/- genotype. The data suggest that p53-/- thymocytes may appear as prelymphoma cells within several weeks post irradiation in CD4⁺CD8⁺ thymocyte subpopulation of irradiated p53 heterozygous mice. [J Radiat Res 44:394-395 (2003)]

View full abstract