The incidence of thyroid cancer is increased among the A-bomb survivors and people suffered from the Chernobyl Nuclear Power Plant Reactor accident. However, the precious molecular mechanisms underlying radiation-induced thyroid carcinogenesis are still unknown. In this study, we investigated DNA damaged response in primary human thyroid cells in vitro. Firstly, to investigate the induction of DNA damage checkpoint in response to 1.0 Gy of gamma-rays, we analyzed the number of Ser1981-phosphorylated ataxia–telangiectasia mutated (ATM) and 53BP1 foci by immunofluorescent staining. The number of 53BP1 foci was increased immediately after irradiation and reached a peak at 30 minutes. Almost all of the 53BP1 foci were co-localized with Ser1981-phosphorylated ATM foci. Most initial foci were disappeared within 24 hours after irradiation, while some foci were remained. Secondary, primary human thyroid cells were irradiated with 6 Gy of gamma rays, and cell cycle arrest was examined. We found that they showed permanent cell cycle arrest and exhibited morphology of senescent cells together with the expression of senescence-associated-β-galactosidase (SA-β-gal). In conclusion, our results demonstrated, for the first time, that primary human thyroid cells retain efficient DNA damage response as well as efficient DNA repair capacity. The cells harboring irreparable DNA damage undergo premature senescence to maintain the integrity of the genome, which could be the major defense mechanisms against ionizing radiation.

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The loss of heterozygosity (LOH) analysis of cancer genome is a powerful method to identify tumor suppressor genes. We have reported that LOH of the Ikaros locus, which encodes a key transcription factor for lymphoid cell differentiation, is frequently observed in radiation-induced mouse thymic lymphoma, as an example of radiation-specific alteration of a tumor suppressor gene. On the other hand, epidemiologic studies of atomic bomb survivors indicate that the mammary gland is the most susceptible organ to solid tumor induction by radiation. Most studies have failed to identify clear genetic alterations in radiation-induced mammary cancer. This prompted us to search for characteristic LOH loci in radiation-induced rat mammary cancers. [Methods] Female Sprague-Dawley (SD) rats at 7 weeks of age were exposed to either gamma-rays (0, 0.5, 1 and 2 Gy), a chemical carcinogen PhIP (40 mg/kg/day, 10 days), or a combination thereof. Genomic DNA was extracted from collected mammary cancers and ear skins of corresponding individuals. Sizes of PCR products were compared between cancers and ear skins for loci that are reported to show PhIP-specific LOH. Hybrid (F1) rats between susceptible SD and resistant Copenhagen rats were generated and irradiated with 4 Gy of gamma-rays for a more systematic LOH analysis. [Result] Relatively high frequency of LOH was observed in PhIP-induced cancers (6 of 28, 21%) compared with gamma-ray-induced and combination-induced cancers (6 and 0%, respectively). Mammary cancer developed in 18 of 29 (62%) F1 rats. The LOH analysis of these cancers is currently underway and will be reported.

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Min mouse is susceptible to radiation tumorigenesis. The efficacy depends on the age at exposure, with a peak at 1-2 weeks of age. Exposure at 7 weeks of age has little enhancement. To better understand the molecular mechanism in the age-dependent radiation tumorigenesis, we carried out detailed LOH analysis of chromosome 18 to which the Apc gene maps, by using statistical method for LOH detection in the tumors of chromosome 18 consomic-Min mice. LOH profiling of the chromosome 18 revealed a difference between the small intestine and the colon, as well as spontaneous and radiation-induced tumors. A majority of spontaneous tumors exhibited MSM allele loss spanning wide range or entire chromosome 18, while tumors induced by 2-week-old exposure exhibited LOH restricted to specific narrow regions, a region spanning the Apc gene, distal chromosome 18, and proximal chromosome 18. Lost allele was of MSM origin (normal allele) in the Apc gene, and of both origins in the distal and proximal chromosome 18. There is a tendency that distal and proximal chromosome 18 had lost alleles of the same origin.

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To evaluate the risk of diagnostic irradiation for infant and children, we studied the mutation in Aprt locus induced by X-ray exposure using mouse kidney cells. Aprt is an enzyme that catalyzes phosphoribosylation of adenine molecule in a salvage pathway. A lack of Aprt activity causes a disease known as APRT deficiency in human associated with marked interstitial fibrosis and/or urolithiasis, however, not essential for survival, because of de novo synthetic pathway. Therefore, the non-essentiality of Aprt activity enables us to use it for mutation detection. We used the Aprt heterozygous mouse for X-ray irradiation and subsequent mutation detection experiment to evaluate the age-dependent risk of X-ray.
Aprt+/- heterozygous B6C3F1 mice were were exposed to 0Gy, 1Gy, or 4Gy of X-rays at 1 or 7 week old. F1 mice were sacrificed after 8 weeks of X-ray exposure and the cells derived from each kidney were cultured in the presence of 1mM 2,6-diaminopurine (DAP) to select Aprt-/- cells. The frequency of DAP-resistant colonies was 2.3 x 10^-5 in average in the un-irradiated control. When mice were exposed with 1Gy of X-rays at 7 weeks old, the frequency of DAP-resistant clone was 61% of unexposed control. This result was unexpectedly lower than the one of the un-irradiated control. When the same dose was applied to the mice at 1 week old, the frequency increased to 200% of unexposed control. This result suggested that X-ray has more suppressive effect on Aprt activity in younger mouse kidney cells. Also mice were exposed with 4Gy of X-rays at 7 weeks old, and the result was 435% increase in mutant frequency compared to the unexposed group. When 4Gy of X-ray was exposed to the mice at 1 week old, the frequency of DAP-resistant colony was further increased to 604% of unexposed control. These data suggested that the higher the dose of X-rays and the younger the age of irradiation, the more Aprt-deficient colonies were induced.

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Though the study of carcinogenesis with p53 gene knockout mice (p53 KO mice) is essential for investigating the relationship between the role of the p53 gene and the carcinogenic process, such experiments are difficult, because the p53 KO mouse has a short lifespan. RNA interference (RNAi), studied with interest recently, enables the knockdown of functional genes, but its application to in vivo conditions is not easy. However, some reports suggest that a method of injection with a mixture of small interfering RNA (siRNA) and collagen is effective for achieving a gene knockdown.
We injected a mixture of siRNA and collagen into the subcutis to make false p53 gene knockout skin locally, and we inspected whether we could use the skin in a radiation carcinogenesis experiment. Our method of experimental skin carcinogenesis is to put a beta-ray source on the back skin of a mouse and continue the irradiation three times a week until the mouse dies or a tumor forms. Beta-rays, which have a low penetration, have little influence on organs except the skin. On the other hand, the tumors induced by this method can be considered beta ray-induced tumors, because skin tumors are rare spontaneous tumors for mice. We hypothesized that we could approximate experiments using p53 KO mice by knocking down the skin p53 gene in the irradiated region by this method. Therefore, we tested an siRNA that knocked down the p53 gene efficiently, with a dosage of the mixture for the subcutis. Also, we examined the time after injection when the siRNA began to show an effect and how long it persisted. We set these conditions variably and obtained the optimal condition for knockdowns of the skin p53 gene.
If local gene control is achieved by this method, as well as in a radiation carcinogenesis experiment, we can apply this method not only to radiation carcinogenesis experiments, but also to UV or chemical carcinogenesis experiments.

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The essential etiology of radiation-induced acute myeloid leukemia (AML) in mice is the downregulation of the transcription factor PU.1. It usually results from a deletion of the PU.1-coding chromosomal region and a mutation of the retained allele. Interestingly, the latter mutation consists mostly of C:G to T:A transitions at a CpG site and is likely to be of spontaneous origin. To work out a mechanism underlying the association between radiation exposure and the AML induction, we have hypothesized that replicative stress after irradiation accelerates the aging of hematopoietic stem cells (HSCs), and the aging-related decline in DNA repair could affect the spontaneous mutation rates. Mathematical model analysis was conducted to examine whether and to what extent the cell-kinetics of HSCs can be modified after irradiation. The hematopoietic differentiation process is expressed as a linear compartment model and the cell-kinetics parameters were estimated by fitting the simulation result to the assay data. The analysis showed the upregulated cell kinetics for HSCs after 3 Gy-irradiation, which seemed to be sufficient to accelerate aging of them. Possible leukemogenic processes have been discussed based on the results, and we have found the most plausible explanation is that the replicative stress-related stem cell aging plays a role elevating spontaneous mutation rates of HSCs and their progeny.

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Combined effects of radiation and chemical carcinogen on pulmonary tumorigenesis in juvenile and adult animals were investigated. Female, 5- and 22-week-old Wistar rats were locally irradiated on the thorax with 3.18 Gy of X-ray, and/or then N-nitrosobis (2-hydroxypropyl) amine (BHPN; 1g/kg body weight) was intraperitoneally injected at intervals of a week or 18 weeks. While control animals still survived at 90 weeks of age when all animals were sacrificed, the administration of BHPN to both 6- and 23-week-old rats resulted in survival reduction due to kidney, brain and ovary tumors. Single irradiation or BHPN alone increased incidence of lung tumors, although most of tumors were benign adenomas. The tumorigenic effects in rats given a combined treatment with irradiation and BHPN were synergistic, and lung carcinomas increased in groups irradiated at 5 and 22 weeks of age. Immunohistochemical staining showed SP-A- and CC-10-positive cells localized in both adenomas and adenocarcinomas induced by thoracic irradiation and/or BHPN administration, suggesting that the lung tumors appear to be mostly derived from alveolar type II cells and Clala cells. These results indicate that X-rays and BHPN affect the same type of target epithelial cells, and posterior treatment with BHPN synergistically enhances radiation-induced lung tumors in juvenile and adult rats.

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Risk assessment on technologies and social activities involves subjective judgments as one of its major components, which depends on the perception of risk by individuals. The present study tried to examine degree of difference in risk perception among different groups, by means of ordering of risks as perceived by individual subjects, and to find any effect of time by comparing the results of three separate trials that were made in 1983, 1992 and 2007.
We interviewed with people who are engaged in NIRS and asked them rank 30 items of various types of technologies and human activities according to their subjective judgments on the order of perceived magnitude of risk (Slovic et al 1981). We undertook the similar survey of public perception in all parts of Japan using web-based questionnaires and 638 responses were obtained. We asked them about occupations, academic carriers, families, information sources and safety of daily lives.
In general, the risk perceptions of female clerical staffs (e.g., secretaries and research assistants) and researchers have got similar closely during 25 years, although there was a difference in the trend of perception of nuclear between them. The formers have consistently judged nuclear power as most risky, whereas its rank judged by researchers fluctuated with social events such as Chernobyl accident. The orders of motor vehicle fell during 25 years. The orders of health risk sources with low exposure (food preservatives, food coloring, X-rays, antibiotics, etc) transiently rose in 1992 survey. Unexpectedly, the web-survey indicated that Japanese public perceived risk similarly irrespective of sex, age, occupation and so on. They judged handguns, nuclear power and smoking as most risky.

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A concern often occurs for an increase of infant congenital anomalies due to pollution sources such as nuclear power plant. Our purpose is to provide a reasonable interpretation for variation of infant mortality from congenital anomalies by calendar year and areas. Analysis by six local area blocks is mainly based on the 1972-2007 Japanese vital statistic prefecture data. General infant mortality in Japan continues to decrease but infant deaths related to perinatal conditions reflect the deaths one-week after birth stronger recently. Different geographical variation was seen between congenital anomalies and other diseases excluding neoplasm. Retaionship with perinatal death was not indicated for chromosomal abnormalities but was observed stronger for congenital anomalies of non-circulatory system except them in 1988-92 or later. Variation was not seen in last five years for other diseases combined but was seen for sudden infant death syndrome. Decrease of observed deaths makes it difficult to understand temporal variation of mortality in small areas but potential risk for infant deaths from congenital anomalies near a pollution facility is small in normal operation.

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It is known that people who entered into the ground-zero area after the atomic bombings in Hiroshima /Nagasaki soon suffered from various diseases. Although a possibility has been pointed out that these diseases were caused by residual radiation, the information was too fragmentary to consider the casual relation between diseases and radiation. A NHK TV program in August 2008 showed individual records of early entrants interviewed around 1950 by medical staffs of ABCC. According to these records, such diseases as fever, diarrhea, epilation etc. were registered. This year we met two entrants in Hiroshima who had individual records at ABCC. We estimated their external exposure, taking into consideration their behaviors after entering the city. About 30 mGy was estimated for Ms A, who entered on August 7 in Otemachi (900 m from the hypocenter) and stayed for one week at Bunridai (1,400 m). Fever, diarrhea, sore mouth etc. appeared with her on August 13. Bleeding gums and epilation began at the beginning of September 1945. About 8 mGy was estimated for Ms. B, who walked on August 7 from Hijiyama to Koi station. She suffered from vomiting and bloody diarrhea on September 12 and epilation began on October 5. Although these diseases recall us radiation syndrome, the level of their radiation exposure seems to be too small to cause such diseases. We are considering three possibilities. (1)Observed diseases were not related with radiation, but with other factors such as fatigue or infection, (2)Radiation exposure was mistakenly underestimated, (3)Under the extreme condition of atomic bomb, synergistically working with other factors, threshold for radiation syndrome could be drastically reduced.

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We report the results of analyses on translocation frequency in lymphocytes of a-bomb survivors by fluorescence in situ hybridization (FISH) method. This study is expected to provid answers to several questions raised by the past cytogenetic studies using conventional Giemsa staining methods. These questions related to the disparity in radiation dose responses between the two cities—Hiroshima and Nagasaki, and lower dose response of Nagasaki factory workers. Because Hiroshima and Nagasaki survivors were examined at Hiroshima and Nagasaki RERF laboratoey, respectively, previouse study with simple Giemsa staining were not free from laboratory bias. Therefore, the present FISH study conducted exclusively at the Hiroshima Laboratory. To date, 900 Hiroshima and 541 Nagasaki survivors were examined by FISH. Present data are summarized as follows: (a) a wide scatter of individual translocation frequencies was observed when plotted against DS02 doses as seen in the previous Giemsa staining study; (b) the city difference became much smaller now using FISH, and the difference is only marginally significant; (c) Nagasaki factory workers and the peoples exposed in outside but with house shielding in both cities had significantly lower dose responses than people who were exposed in Japanese houses; (d) the reduced intercity difference suggests that the previous city difference by the Giemsa methods was mainly due to different aberration detection rates between Hiroshima and Nagasaki laboratories.

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We estimate radiation dose using enamel of molars donated by atomic bomb survivors in Hiroshima by electron spin resonance (ESR) technique. In the present study, we conducted ESR measurements of 92 molars and compared the results with chromosome aberration frequencies (by FISH method and/or Giemsa method) of the same survivors. Both ESR signal intensity and chromosome aberration frequency were used to calculate ⁶⁰Co gamma-ray equivalent dose. FISH data and Giemsa data fitted closely in 37 individuals who were examined by the two methods. We decided to use FISH data of these cases. Among a total of 92 survivors (35 had only Giemsa data, 20 had only FISH data, and 37 had both data sets), we found that ESR dose and chromosome dose showed a close association in the majority of cases. There are a few exceptions, however. Seven survivors showed substantially lower ESR doses than corresponding chromosome doses. Scince most of the samples were wothdom teeth ot the donors were exposed to the bomb below age of 5years old, we think that molars examined were not probably established at the time of the bomb. On the other hand, nine survivors showed considerably higher ESR doses than corresponding chromosome doses. Their histories of medical exposure are being investigated but so far we found no evidence for the exposure. When ESR doses or FISH doses were compared with DS02 gamma-ray doses, the individual points showed a wider distribution. Because the biodosimetric endpoints by the two completely different methods (ESR and FISH) fitted closely to each other, it seems that the results validated the two methods each other, which may allow us to use chromosome data which had already been obtained from 4000 A-bomb survivors, and may be able to indicate possible extent and direction of dose bias in the DS02 individual doses.

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The method of electron spin resonance (ESR) dosimetry was applied to human tooth enamel to obtain individual absorbed doses of residents of Makanchi, Urdzhar and Taskesken settlements located near Kazakhstan-Chinese border (about 400 km to South-East from Semipalatinsk nuclear test site (SNTS) and about 1000 km from The Lop Nor Nuclear Weapons Test Base (China)). Since the ground and atmospheric nuclear tests (1964-1981) at Lop Nor, the people residing in these settlements have believed to be exposed heavily by radioactive fallout. Tooth samples were extracted according to medical reasons in a course of ordinary dental treatment. Kokpekty was chosen as control and was not subjected to any radioactive contamination and located 400 km to the Southeast from SNTS. It was found that the excess doses obtained after subtraction of the contribution of natural background radiation do not exceed 92 mGy for residents of Makanchi. For residents of Urdzhar, excess doses ranged up to 243 mGy for all ages. For residents of Taskesken, the maximum of excess dose were determined as 95 mGy.

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The pollution caused by the military use of depleted uranium has raised increasing concern about its toxicity on children. Renal toxicity is the hallmark effect of uranium exposure. In the present study, the relationship between renal development and uranium distribution was examined in immature rats exposed to uranium acetate.
In the new born rats, the renal cortex and medulla are complicated in the kidney. Uranium was found in the innermost areas of the cortex. The kidneys achieve their adult zonation into a cortex, outer medulla, and the inner medulla at around 3 weeks of postnatal age. Uranium was localized in the inner cortex and the outer stripe of the outer medulla. The distribution of the S3 segment of the proximal tubules was corresponding to uranium distribution; the S3 segment was confined to the innermost areas of the cortex of the new born rats and spread to inner cortex and the outer stripe of the outer medulla of the young rats. The age-differences in uranium levels and damage in kidney was observed. Taken together, it suggest that the developments of S3 segments of the proximal tubules, which are selective-site of uranium accumulation, could be involved in the age-differences in the renal toxicity caused by uranium.

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By using two-dimensional DNA electrophoresis, we have been studying mutations in the F1 mice derived from X-irradiated spermatogonia cells in order to estimate the genetic risk of radiation. We previously reported the results of comparative genomic hybridization study with high-density microarray (HD-array CGH) on five deletion mutations identified in F1 mice derived from BALB/c male mice. Recently, we have determined the sizes and base-sequences of seven deletion mutations identified in F1 mice derived from B6C3 male mice. We have prepared custom arrays by selecting specific oligo-probes at every 1-5 kb intervals expanding approximately 10 Mb surrounding each NotI site involved in deletions. The array-CGH analyses revealed that among the six deletions in male alleles, the sizes of the five deletions in the exposed group were: 13 Mb, 10.7 Mb, 4.7 Mb, and 1.9 Mb. The sizes of the deletions in one control male allele and one control female allele were 2.3 Mb and 2.5 Mb respectively. The sequences around the break-points of five deletions in the exposed group and one deletion in the female allele contained no homologous sequences, this implies that these deletions were originated from non-homologous end joining. On the other hand, the spontaneous deletion in one control male allele contained highly homologous (96%) sequence spanning 2 kb at both ends of the break-points and this was thought to be derived from homologous recombination and subsequent deletion.

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We used two-dimensional electrophoresis (2-DE) of DNA to display thousands of DNA fragments as spots on a gel without the use of probes for detection of gene mutations. Using this technique, we assessed mutation rate in mouse germ cells following paternal radiation exposure. We selected B6C3F1 males and JF1 females as parents. We examined DNA samples of 1,007 progeny, 505 derived from sprematoginial cells irradiated with 4-Gy of X-rays and 502 control progeny. We selected 1,190 paternal spots and 1,240 maternal spots for the mutation screening. Analyses of 595,387 paternal spots in the 4-Gy exposed group permitted us to identify six mutations affecting 12 spots in six mice. Among these, five mutations were deletions involved multiple spots; one deletion involved four spots, three deletions each involved two spots and another one involved a single spot. Molecular studies using high-density oligo microarray revealed that all five deletions were quite extensive, 1.9Mb to 13Mb. Another mutation in the exposed group consisted of a small change of 6-bp gain at a microsatellite. In the control group one spontaneous mutation, 2.3-Mb deletion which involved two spots, was identified among the 583,051 paternal spots. Among the 1,228,352 maternal spots, we found two spontaneous mutations, a 34-bp deletion at a microsatellite locus and a 2.5-Mb deletion. Assuming that each spot as a locus, the estimated spontaneous mutation rate is 0.34 x 10^-5/locus/generation. The induction rate is estimated as 0.42 x 10^-5/locus/Gy (the confidence interval includes 0). Our estimate is considerably lower than the mean induction rate at the 7-locus tests in mice, which is estimated to be 2-3 x 10^-5/locus/Gy. The DNA 2-DE scans about 0.2% of the genome, thus we estimate that 1-Gy of radiation on male spermatogonial cells will induce approximately one relatively large deletion mutation per genome (or animal).

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Background: Late effects of radiation exposure to the atomic bomb have been evaluated including the Life Span Study (LSS).
Methods: Initial 120,321 people identified in 1950 were followed up until the end of 2003 using population registry system and death certificates. Among them, 86,611 subjects with known individual doses by the Dosimetry System 2002 (DS02) were analyzed. Excess relative risks per Gy of target organ dose (ERR/Gy) and their 95% confidence intervals were calculated by a Poisson regression model.
Results: Total of 50,620 subjects (58%) died during the follow up period. ERR/Gy in a linear model was 0.22 (95%CI: 0.18, 0.26) for all causes of death, and 0.47 (0.38, 0.56) for total solid cancer, 2.62 (0.47, 7.25) for urinary tract cancer, 1.60 (0.99, 2.37) for breast cancer, 1.12 (0.33, 2.26) for bladder cancer, and significantly increased for cancers of esophagus, stomach, colon, liver, gall bladder, lung, and ovary. Also, significantly increased for total leukemia (ERR/Gy: 4.3, 95%CI: 3.1, 5.8), but not for malignant lymphoma and multiple myeloma. ERR/Gy for total circulatory diseases (0.11, 95%CI: 0.05, 0.17) including heart diseases and stroke and respiratory diseases (0.21; 0.10, 0.33) significantly increased. Effect modification in ERR for solid cancer by sex, age at exposure, and attained age was significant.
Conclusions: Risk of death of total death, major cancers, and major chronic diseases significantly increased with dose-response to radiation in the LSS subjects throughout life. The risk of leukemia continues, albeit at a lower level than previously. The risk of stroke and heart diseases also increases at moderate-to-high doses. Those relative risks were larger in females and in those who were exposed at young age and getting smaller along with subjects’ age. The results of this study, six-year elongation of the study period, are consistent with the previous report.

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Purpose: The Radiation Effects Research Foundation has reported that there is radiation risk for basal cell carcinoma based on pathological examination and follow–up of radiation and skin cancer incidence through 1987 of the Life Span Study (LSS) cohort comprising atomic bomb survivors. In this study, we extended the follow up by 10 years, reexamining radiation risk for skin cancer by histological type.
Method: Of 120,321 LSS members, 80,158 who were in the city of Hiroshima or Nagasaki at the time of bombing and with radiation dose estimated by the DS02 dosimetry system were examined. Pathologists reviewed suspected skin cancer cases diagnosed between 1958 and 1996, and confirmed first primary skin cancers. Excess relative risks (ERRs) of skin cancer due to radiation by histological type were estimated using Poisson regression model.
Results: Among the eligible LSS population, 336 incident skin cancer cases were observed. By histological type, the following cases were observed: malignant melanoma (n = 10), basal cell carcinoma (n = 123), squamous cell carcinoma (n = 144), Bowen’s disease (n = 64), Paget’s disease (n = 10), and other skin cancer cases (n = 15). ERRs were estimated assuming a linear dose response, and only basal cell carcinoma had a statistically significant positive dose response (ERR/Gy = 2.1, 95% confidence interval (CI) = 0.37-1.2, P<0.01), the previous study with follow-up through 1987 reported an ERR/Gy of 1.8 (90% CI = 0.83-3.3). We also explored other models in an effort to find a best fit model using Akaike information criteria (AIC). The best fit dose response model estimated a dose threshold at 0.6 Gy (95% CI = 0.34- 0.89), an ERR/Gy of 2.7 (95% CI = 1.1 - 5.1). This model predicted an ERR at 1 Gy of 1.1 (95% CI = 0.43-2.05). This model provided the risk of basal cell carcinoma increased by 10% with each decrease year of age at exposure.
Conclusion: Epidermal basal cells are sensitive to ionizing radiation, especially for people who were young at exposure. The threshold for a radiation dose response of basal cell carcinoma was estimated to be 0.6 Gy, lower than the 1.0 Gy reported in the previous study.

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AIM: To investigate pathologically effects of internal radiation on human body, we determine radioactivity on samples of Nagasaki atomic bomb casualties. We have already investigated methodology of detecting residual radiation on formalin fixed tissue specimens and paraffin-embedded blocks of autopsy cases at acute stage of atomic bomb injury in Nagasaki and Thorotrast patients, who were internally exposed chronic low-dose-rate to alpha-radiation from thorium dioxide deposits following intravascular administration of the radiographic contrast agent. In this study, we determined radioactivity on tissue specimens of Nagasaki atomic bomb causalities at the acute stage injury, Thorotrast patient and non-exposed control subjects by autoradiography. MATERIAL and METHODS: 1) 7 cases of Nagasaki atomic bomb casualties at acute stage radiation injury, 2) 1 case of Thorotrast patient and 3) non-exposed control subjects; 4 cases from Nagasaki Medical Ceneter and 3 cases from Kyusyu university were determined radioactivity in the tissue specimen by autoradiography. The alpha-particle track lengths in the tissue specimen by autoradiopraphy. The alpha-particle track lengths in the tissue specimen were measured. Energy characteristic of 239Pu was calculated from the alpha-particle length in the emulsion by Zeigler's Method, Herium Stopping Powers and Ranges in All Elemental Matter. RESULTS: The much number of alpha-particle tracks from Nagasaki atomic bomb acute casualties was observed on lung, kidney and bone, compared with non-exposed control subjects. The pattern of alpha-particle track lengths of Nagasaki atomic bomb acute casualties was consistent with energy characteristic of 239Pu. It should be identified the nuclide of residual radiation by radiation detector.

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Excess relative risk of lung cancer among atomic-bomb survivors remains high even now, more than 60 years after the bombings. However, molecular mechanisms underlying the long-lasting effects of radiation exposure on lung cancer development remain unclear. To assess effects of radiation on lung carcinogenesis, we analyzed DNA methylation status of the p16 and RASSF1A genes in 20 atomic-radiation-exposed and 18 non-exposed non-small cell lung cancer (NSCLC) cases and examined association between methylation status and radiation exposure. Our analysis showed trends that RASSF1A methylation in the exposed NSCLC cases was less frequent compared with the non-exposed cases: 32% (6/19) vs. 56% (10/18), and that, among the exposed cases, methylation frequency of the gene in squamous cell carcinoma were less frequent than those in adenocarcinoma. These results suggest that frequencies of certain types of gene methylation might be associated with radiation exposure in a histologically dependent manner, although the association was not statistically significant. Further analysis with increased numbers of cases is required.
Methylation status of retrotransposone LINE1, a marker of global DNA methylation in genomic DNA, is under analysis. Results from this analysis also will be presented.

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Thyroid cancer is one of the malignancies most strongly associated with ionizing radiation. Risk of papillary thyroid cancer (PTC) among atomic-bomb survivors has been found to significantly increase with radiation dose. A major early event in papillary thyroid carcinogenesis is constitutive activation of MAPK signaling pathway caused by one of the following gene alterations, which may be categorized into two types: Chromosomal rearrangements of RET and NTRK1 and gene point mutations of RAS and BRAF. Most of these alterations are known to activate not only MAPK pathway but also PI3K/AKT pathway. In fact, amplification of PIK3CA gene has been recently detected in PTC, suggesting that activation of this pathway may also be involved in papillary thyroid carcinogenesis.
To clarify relationship between radiation exposure and development of PTC, we examined gene alterations involved in MAPK signaling pathway, i.e. RET, NTRK1 and BRAF rearrangements, as well as BRAF and RAS point mutations, in 73 adult-onset PTC cases among atomic-bomb survivors. We found that relative frequency of BRAF and RAS gene point mutations in our PTC cases significantly decreased with increased radiation dose, while RET and NTRK1 chromosomal rearrangements showed a significant increase in relative frequency in the PTC cases with radiation dose. These findings indicate an important role of chromosomal rearrangements, especially RET/PTC rearrangements, in adult-onset radiation-associated PTC carcinogenesis.
Interestingly, PTC cases with no detected gene alterations were found frequently among patients who were exposed to high radiation doses and developed cancer early after exposure. This result suggests that other radiation-associated gene alterations than RET/PTC rearrangements might be involved in the development of radiation-associated PTC. In the light of this, amplification of PIK3CA gene is currently under analysis. This result will also be presented.

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[Purpose]To study the trans-generational effects of atomic-bomb radiation, that is effects on human germline cells, at the genome-wide level, a bacterial artificial chromosome (BAC) DNA micro-array based comparative genomic hybridization (BAC-aCGH) have been introduced. We report the results obtained from 305 individuals by this method. [Experiment] We used an array with about 2,500 BAC-clones distributed across human autosomes. We examined 265 offspring who had at least one parent exposed to high-radiation doses(1.0 Gray or more) and 40 offspring from unexposed parents. [Results] We found 1,534 copy number variants (CNVs) in the genome;of these, 97 CNVs were termed 'rare' CNVs whose frequencies were less than 1%. With respect to rare CNVs, DNA from the offspring and their parents were examined by quantitative polymerase chain reaction to confirm whether or not those CNVs were from their parents. Three rare CNVs identified in three offspring were not identified in either parent and these are defined as 'putative de novo mutants.' One mutant was a deletion type and remaining two were amplification types. We determined the parental origin of the de novo mutants using single nucleotide polymorphisms within the mutated region in the offspring. The results demonstrated that all three de novo mutants occurring on the gametes originated from exposed fathers. [Discussion] This number of de novo mutants (three) is too small to reach a firm conclusion as to whether the mutation rate of the exposed group is significantly higher than that in those from unexposed group. Moreover, in the past data, the mutations caused by radiation seem to favor being deletions. However, in the classic animal studies, duplications could not be detected due to a technical limitation. It will be an important task to test whether segmental duplications occur as commonly as deletions. Therefore, we will continue the study using the high-density array system to 1) increase the number of loci examined in order to increase the number of de novo mutants to be identified, and 2) to get information whether or not duplication-type de novo mutations are radiation-dose related.

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It is widely known that there are many copy number polymorphisms in the human genome and several are related to certain kinds of disease or individual differences. While most are transmitted from parent to child, a few arise de novo. We have investigated whether atomic-bomb radiation causes de novo copy number mutations in the germ cells of atomic-bomb survivors by examining the genome of offspring of atomic-bomb survivors. In case only one of the parents was exposed to radiation, it was necessary to discriminate whether mutation occurred on which one of homologous chromosome of offspring derived from their parents. In order to examine the whole human genome, we conducted the examination using BAC-array CGH on which about 2,500 BAC clones were printed. The study used genomic DNA from 265 offspring of atomic-bomb survivors and 40 offspring of an unexposed control group. Three mutations were identified in three offspring, that were not in their parents. One mutation was a deletion type involving a 1.4 Mb length of chromosome 1q41 and two mutations were an amplification type involving 131,290 bp of 5p15.2 and 431,737 bp of 17p13.3, respectively. In the breakpoints of the deletion mutation, precise breakpoints could not be determined, segmental duplications were involved in both termini. There were microhomologies in the each breakpoint of both two amplification mutations. Because only one of the parents was the atomic-bomb survivor in all three families, we needed to determine parental origin of the de novo mutations. We used an Affymetrix SNP array 6.0 to examine Mendelian inconsistency of SNP information in the genome region involving the mutations. We examined 422 SNPs in the genome region involving the deletion mutation, of which 43 SNPs were informative for discrimination of parental origin. There were 54 and 85 SNPs in the genome regions involving the two amplification mutations, of which 15 SNPs were informative for each. Informative SNPs for each case showed that all three mutations occurred on a chromosome derived from the radiation-exposed father. The SNP array was valuable for determination of the parental origin of de novo copy number mutations. This number of de novo mutations (three) is too small to reach a solid conclusion as to whether the mutation rate of the children of atomic-bomb survivors is significantly higher than in those from control group. We will continue and expand our study to increase the statistical power.

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Various scintillators have been used in a wide range of scientific fields, such as physical science, engineering, and medical science. Although the performance of organic scintillators is inferior to the performance of inorganic scintillators, they can be simply manufactured, they are inexpensive, they are readily available, and they have been used by many people for half a century. Plastic scintillators are produced by using plastics containing aromatic hydrocarbons, which are basic materials, and doping them with one or two types of wavelength shifters. The main reason for doping with wavelength shifters is to convert the fluorescence generated in the basic material into a wavelength in the visible light region where it can be detected and recorded. Another reason is to reduce self-absorption of the light that is fluoresced in the basic material. However, due to extensive technological developments, detectors that can detect light in the short wavelength region have become commercially available. Here we show to review the history of scintillation detectors and verify that "simple" plastics can detect radiation with high accuracy.

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Pyroelectric crystal has spontaneous polarization so that the surface of the crystal is charged. The surface charge is compensated by the electron or ion in the air. The variation of the temperature of the pyroelectric crystal yields the residual compensating charge that generates the high-voltage field. This leads to make a compact radiation source. Several studies of the radiation source using the pyroelectric crystal showed the emission of the electron, ion, x ray, and neutron. However, it is not clear for the parameters in order to control the emission of the radiations. In this study, the electron current from the pyroelectric surface to the ground was measured with the parameters of the pressure and the temperature ramp rate that is the rate of the temperature variation to the time. A single crystal of LiTaO₃ (10 mm X 10 mm X 5 mmt) was fixed on a copper plate. The surface of the crystal faced to another copper plate at intervals of about 4.8 mm. The copper plate was connected to the picoammeter (Keithley 6485). The electron current was measured with the pressure of 15-25 Pa and the maximum temperature ramp rate of 2.0 K/s. The pulsed electron current was observed with the current of about 100 uA and the duration of about 1 ms. This is explained as follows. The compensating charge appears at the surface of the pyroelectric crystal by varying the temperature and the surface charge generates the high voltage. When the voltage exceeds a breakdown voltage at a pressure, the surface charge is discharged as the pulsed current. For the pressure, the number of the pulse increased as the pressure increased because the breakdown voltage become low as the pressure increases at the pressure around 20 Pa. For the temperature ramp rate, in proportion as the rate increases the number of the pulse increased because the surface charge appeared increases.

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The present study proposed a stochastic model for the randomly generated DNA double strand breaks, under the assumption that double strand breaks (dsbs) result from a pair of closely located single strand breaks (ssbs) produced in the opposite strands. By introducing probability variables corresponding to the number and the location of ssbs, mathematical formulation was presented to give the ratio of dsbs to the total number of ssbs. In the case of Poisson distribution for randomly produced ssbs, when the number of dsbs and those of ssbs in both stands is represented by q, q₁ and q₂, respectively, the ratio q/(q₁+q₂) was found to be proportional to (d/t)[λexp(-2λ)+λ²exp(-λ)+λ³], where d, t and λ is the distance between two ssbs to form dsb, the length of each strand, the average number of ssbs produced in each strand, respectively. In order to compare these results with the existing model based on the similar assumption to ours, q/(q₁+q₂) was calculated following the formulation of ssbs presented by Aspen's textbook on Radiation Biophysics. The result was simply expressed as [1-exp(-λ)]. Although the detailed comparison has not been achieved yet, the ratio becomes approximately proportional to radiation dose in both cases under the realistic assumption that λ is small. In addition, we also considered a binomial distribution model and compared with the Poisson distribution case.

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In this study, a process of peroxidation of linolenic acid, which is one of fatty acids that is the simplest biological lipid, by gamma-irradiation was analyzed. The linolenic acid was dissolved in benzene at a final concentration of 1 mM. The linolenic acid micelle was prepared as follows. The linolenic acid at a final concentration of 1 mM was added to PBS(-) with 0.08% nonaethylene glycol monododecyl ether. And, this solution was stirred vigorously. The prepared solutions were irradiated with ⁶⁰Co gamma-rays at several dose-rates. Gamma-irradiated sample solution was combined with TBA regent and mixed thoroughly. The mixed solution was heated for 15 min in a boiling water bath. The malondialdehyde (MDA) amount was determined by measuring the absorbance of the reaction solution at 532 nm. In this study, the lipid peroxidation was evaluated by the MDA amount. The lipid peroxidation of linolenic acid progressed with increasing dose of gamma-irradiation in benzene. It was revealed that this dose-effect relationship was nonlinear. In this experimental condition, there was a inverse dose-rate effect. In linorenic acid micelle solution, a relative MDA amount value increased linearly with increasing dose of gamma-irradiation up to 0.5 kGy (dose rate: 0.8 kGy/h). In dose of gamma-irradiation more than 0.5 kGy, a relative MDA amount value decreased dose-dependently and gradually. Difference between dose-effect relationship in a linolenic acid micelle solution and that in a linolenic acid benzene solution shows that the molecular environment of linolenic acid affects the linolenic acid peroxidation by gamma-irradiation.

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Transfer factor (TF), one of the traditional parameters used for predicting the transfer of radionuclides in the environment, is still useful for dose assessment of human as well as of environmental biota, because of its simplicity. As soil – plant TFs are studied and collected mainly in Europe, the data available for another environments are quite limited. Considering the increase need of nuclear power stations in Asian countries, collection of soil–plant TFs in Asian environments are urgently required. In this study, commonly consumed leafy vegetables in Sri Lanka and associated soils from two farming systems, organic and conventional, were collected and analyzed for major and trace elements by using inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). About 45 and 30 elements were determined for the 20 soil and 80 crop samples, respectively. In most case, K showed the highest TF, followed by P, Ca, Mg, Rb, Mo, and Mn, which were higher than 1.0 (dry plant / dry soil ratio). TFs of most elements in Sri Lankan leafy vegetables were higher than those in Japanese green vegetables. The values were compared also with the values in IAEA database (TRS-364). Difference between two farming systems was discussed too.

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The crystallization of magmas makes rock-forming minerals including more or less uranium and thorium isotopes other than major elements. This means that all terrestrial rocks become naturally radioactive. Since uranium and thorium are lithophile elements that are easy to be bond to silicates, radioactive concentrations of acid rock such as granite tend to be high. In this study, the natural radioactivity, radon (²²²Rn) emanation fraction and specific surface area of minerals separated from raw rocks were measured for comparing among rock-forming minerals. One granitic gneiss and weathered granite soil were prepared and sieved into not more than 500 μm. Minerals included in the two were first identified roughly by X-ray diffraction and then mineral separation from the raw samples was carried out using a heavy liquid, SPT (sodium polytungstate). Subsequently, the radioactive concentrations (²³⁸U, ²³²Th, ²²⁶Ra, ⁴⁰K), the radon emanation fractions of the separated minerals were measured using a high-purity germanium detector by γ-ray spectrometry. The specific surface areas were also determined according to the BET method. As a result of the mineral separation, two different minerals of quartz (SiO₂) and muscovite (KAl₂(Si₃Al)O₁₀(OH)₂) and three ones of quartz, microcline (KAlSi₃O₈) and goethite (FeO(OH)) were obtained from the gneiss and weathered granite samples, respectively. For the gneiss sample, the radioactivities of muscovite were 10 times higher than those of quartz, although the radon emanation fraction of quartz was much higher. For the weathered granite sample, the order of the higher radioactivities of decay series nuclides and ⁴⁰K was goethite > microcline > quartz and microcline > quartz ≈ goethite, respectively. In contrast, the radon emanation fraction of microcline was significantly lower than quartz and goethite. The inhomogeneous distribution of ⁴⁰K can be reasonably understood from the viewpoint of mineral compositions. On the other hand, we can explain for the other nuclides, taking into account the order of the crystallization of object minerals (quartz, muscovite and microcline). Because the latest crystallized mineral is quartz, more uranium and thorium may have been already contained in muscovite and microcline of the earlier silicates. Here, grains of goethite, which is a clay mineral with large surface areas, may adsorb natural radioactive nuclides. We will attempt to discuss why the radon emanation fractions are inhomogeneous between rock-forming minerals.

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Pyroelectric crystal is spontaneously polarized material. The polarization varies by varying temperature and the compensating charges appear on the surface. The high-energetic electron can be obtained by using this crystal. Thus radiation source which is very compact can be made without high-voltage generating device. Several studies of the radiation source using pyroelectric crystal have been performed, but basic data to control the radiation source had not been examined. In this study, we measured the charges emitted from pyroelectric crystal with the parameters of the temperature ramp rate and the pressure to obtain basic data to control the electron emission. Here, temperature ramp rate means temperature variation with respect to time. We used LiTaO3 crystal as pyroelectric crystal. LiTaO3 crystal was in size of 10×10×0.5 mm. We used the heater of 78 Ω. Temperature was varied from room temperature to about 70 °C by varying heater current (0.2, 0.3, and 0.4 A). Thus, the temperature ramp rate was the range of 0.4-1.5 K/s. The pressures were 15, 20, and 25 Pa by using rotary pump. While varying the temperature ramp rate, we measured the charges emitted from pyroelectric crystal for 30 sec for three times. When the averages of the temperature ramp rate were 0.4, 0.9, and 1.5 K/s at 20 Pa, the averages of the emitted charge were 73, 259, and 494 nC, respectively. This shows that the emitted charge increases as the temperature ramp rate increases. When the pressures were 15, 20, and 25 Pa at 1.5 K/s, the averages of the emitted charge were 157, 494, and 492 nC, respectively. The emitted charge at 20 Pa was almost same as that at 25 Pa. Compared with the pressures of 20 Pa and 25 Pa, the emitted charge was considerably low at 15 Pa. This result shows that when pressure is too low, it is hard for the electron to emit.

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South coast of India is known as the high-level background radiation area (HBRA) mainly due to the emission from sea sands that contain natural radionuclides as components of the monazite. The rich deposit of monazite unevenly distributes in longer than 100km along the coastal belt of Tamil Nadu and Kerala. We measured radioactivity of sea sands collected from the coastal spot in Tamil Nadu where the anomalously high level of external radiation was detected. In the beach of Chinna Vilai in town of Manavalakurichi of Kanyakumari district, approximately 30km far from the south tip of the Indian peninsula, we found HBRA spot that lays in 2m (width) x 7m (long) along the sea. By the in situ radiation measurements using a field meter, the highest dose in this spot was 162.7mSv/y (18.8μSv/h) that was considerably higher than the previous report in 2007 by Singh et al. which showed 11.4μGy/h in somewhere in Manavalakurichi. The direct measurement by GM survey meter of approximately 100g of the sea sands samples, that were collected from four different places in the HBRA spot and were packed in an independent plastic bag, demonstrated the count rate higher than 1000cpm for all the samples. From these samples, 6 nuclides of Thorium series (Ac-228, Th-228, Ra-224, Pb-212, Bi-212, Tl-208), 4 nuclides of Uranium series (Pa-234m, Ra-226, Pb-214, Bi-214), and Th-231 belonging to Actinium series were found over the detection limit of the HPGe semi-conductor detector. The radioactivity of each nuclide was estimated within the range between 1.08Bq/g (Bi-214) and 43.7Bq-g (Th-228), which appears as the comparable level to the results obtained in Kerala (Shetty at al. 2006).

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The polymer gel dosimeter using the radical polymerization reaction of organic monomer enables small volume measurement of dose. In this work, we evaluate the simulated results are compared to depth dose distributions measured with polymer gel dosimeters for small volume objects. And also the polymer gel’s water equivalency by means of calculations on the attenuation and ionization of radiations, and Monte Carlo simulations on the transport of electron and photon respectively in water and polymer gel.

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Purpose: At present, the radioactivities in the environmental materials are monitored at many spots in Japan. The data is useful for estimating the radiation doses received by people. However, such environmental monitoring and study have not been conducted at Shobara City in the northern part of Hiroshima Prefecture. So, we started on accumulating the data of environmental radioactivity and studying how the radioactivities originated. First of all, we are measuring the radioactivities in airborne particulate matter (APM) in order to estimate where the radioactivity in APM is derived from.
Material and Methods: Every sampling of APM was performed using an air-dust sampler (Aloka,DMS-205) for six hours with absorption rate of 80 little per minute. After the sampling, the filter (ADVANTEC, HE-40T) was covered with polyethylene film. The gamma rays from the samples were measured with a high purity Ge-detector (Oxford, CPVDS30-0190, volume of 160 cm3). Each sample was measured three months after the sampling in order to determine the activities in the uranium and thorium series. In order to study how the rocks and soils around the sampling position influenced to the air dusts, the natural radioactivities in these materials were also determined with gamma-ray spectroscopy. The gamma-ray detection efficiencies for the powdered rock or dried soil samples were determined by using the rock reference samples from the Geological Survey of Japan.
Results and Discussion: Several natural radioactivities such as 212Pb and 40K were clearly observed in the APM collected in winter or spring. However, APM in summer included few natural radioactivities. This implied that the APM in winter and spring might have included the yellow sands or small particles from the east part of the Asian continent. The weathered rocks and dried soils around the sampling position also have a possibility to produce the natural radioactivities in the APM. The results of the present measurements will be used for studying how the near and distant sources related to the APM in the sampling spot.

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Accurate map work is critically important to determine distances of hibakusha(atomic bomb survivors) from the hypocenter, which is needed to evaluate radiation doses. However, the distances of hibakusha from the hypocenter were accurate for a 100-m mesh unit up to now because of the restrictions of map and space analysis technology. This study aims to undertake a more accurate evaluation by using a geographic information system(GIS). The outline of the procedure is as follows.
1)Selection of the base map. We selected a Hiroshima city urban planning map(scale:1/2500) made from 1925 to 1928 as a base map. To work with the GIS, the map was converted into a tiff file by a scanner.
2)House numbers for the map. This base map shows neither address information (house numbers) nor positional coordinates (latitude and longitude) but it is a survey map. Then, we added the house numbers from a Cadastre map made in around 1930.
3)Georeferencing. Georeferencing was undertaken using a GIS to give positional coordinates for the map made in step2 above. Georeferencing was used to select the control point (for example, buildings that have been exposed to radiation), to give the location information, and to adjust the distortion of the image.
4)Decisions on and digitizing of hibakusha locations by collation with ABS (database of atomic bomb survivors in Hiroshima) location information. The house polygon was made by searching on the map for a point (house) referring to the hibakusha location information(address) from the ABS and digitized geographic information. And, this house polygon was converted into the gravity point.We consider this gravity point as a hibakusha location.
5)Calculation of the distances of hibakusha locations from the hypocenter. The distance from a gravity point(step4 above) was calculated from the hypocenter by using Hawth Tools that was one of the GIS extension software.
As a result, we were able to confirm the effectiveness of this method though there were a few errors.
In this presentation, first of all, we will show details of the work. Next, we will report on the result up to the end of October 2009. Finally, we will try to examine the improvement from existing methods.
This work was supported by JSPS Grant-in-Aid for Challenging Exploratory Research(No.21652070).

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