Hideaki Yamashiro

Distribution of Artificial Radionuclides in Abandoned Cattle in the Evacuation Zone of the Fukushima Daiichi Nuclear Power Plant

The Fukushima Daiichi Nuclear Power Plant (FNPP) accident released large amounts of radioactive substances into the environment. In order to provide basic information for biokinetics of radionuclides and for dose assessment of internal exposure brought by the FNPP accident, we determined the activity concentration of radionuclides in the organs of 79 cattle within a 20-km radius around the FNPP. In all the specimens examined, deposition of Cesium-134 (134Cs, half-life: 2.065 y) and 137Cs (30.07 y) was observed. Furthermore, organ-specific deposition of radionuclides with relatively short half-lives was detected, such as silver-110m (110mAg, 249.8 d) in the liver and tellurium-129m (129mTe, 33.6 d) in the kidney. Regression analysis showed a linear correlation between the radiocesium activity concentration in whole peripheral blood (PB) and that in each organ. The resulting slopes were organ dependent with the maximum value of 21.3 being obtained for skeletal muscles (R2 = 0.83, standard error (SE) = 0.76). Thus, the activity concentration of 134 Cs and 137Cs in an organ can be estimated from that in PB. The level of radioactive cesium in the organs of fetus and infants were 1.19-fold (R2 = 0.62, SE = 0.12), and 1.51-fold (R2 = 0.70, SE = 0.09) higher than that of the corresponding maternal organ, respectively. Furthermore, radiocesium activity concentration in organs was found to be dependent on the feeding conditions and the geographic location of the cattle. This study is the first to reveal the detailed systemic distribution of radionuclides in cattle attributed to the FNPP accident.

Effects of radioactive caesium on bull testes after the Fukushima nuclear plant accident

We aimed to investigate the effect of chronic radiation exposure associated with the Fukushima Daiichi Nuclear Plant accident on the testis from 2 bulls. Estimated dose of internal exposure in one bull was 0.7–1.2 mGy (134Cs) and 0.4–0.6 mGy (137Cs) and external exposure was 2.0 mGy (134Cs) and 0.8 mGy (137Cs) (196 days). Internal dose in the other was 3.2–6.1 mGy (134Cs) and 1.8–3.4 mGy (137Cs) and external dose was 1.3 mGy (134Cs) and 0.6 mGy (137Cs) (315 days). Sperm morphology and spermatogenesis were within normal ranges. 134, 137Cs radioactivity was detected but Cs was not detectable in the testis by electron probe microanalysis. Thus, adverse radiation-induced effects were not observed in bull testes following chronic exposure to the above levels of radiation for up to 10 months. Since we could analyse a limited number of testes, further investigation on the effects of ionizing radiation on spermatogenesis should be extended to more animals.

Interspecies somatic cell nucleus transfer with porcine oocytes as recipients: A novel bioassay system for assessing the competence of canine somatic cells to develop into embryos

Interspecies somatic cell nucleus transfer (iSCNT) could be a useful bioassay system for assessing the ability of mammalian somatic cells to develop into embryos. To examine this possibility, we performed canine iSCNT using porcine oocytes, allowed to mature in vitro, as recipients. Canine fibroblasts from the tail tips and dewclaws of a female poodle (Fp) and a male poodle (Mp) were used as donors. We demonstrated that the use of porcine oocytes induced blastocyst formation in the iSCNT embryos cultured in porcine zygote medium-3. In Fp and Mp, the rate of blastocyst formation from cleaved embryos (Fp: 6.3% vs. 22.4%; and Mp: 26.1% vs. 52.4%) and the number of cells at the blastocyst stage (Fp: 30.7 vs. 60.0; and Mp: 27.2 vs. 40.1) were higher in the embryos derived from dewclaw cells than in those derived from tail-tip cells (P<0.05). The use of donor cells of any type in later passages decreased the rate of blastocyst formation. Treatment with trichostatin-A did not improve the rate of blastocyst formation from cleaved dewclaw cell-derived embryos but did so in the embryos derived from the tail-tip cells of Fp. Only blastocysts derived from dewclaw cells of Mp developed outgrowths. However, outgrowth formation was retrieved in the embryos derived from dewclaw cells of Fp by aggregation at the 4-cell stage. We inferred that iSCNT performed using porcine oocytes as recipients could represent a novel bioassay system for evaluating the developmental competence of canine somatic cells.

90Sr in teeth of cattle abandoned in evacuation zone: Record of pollution from the Fukushima-Daiichi Nuclear Power Plant accident

Here we determined the 90Sr concentrations in the teeth of cattle abandoned in the evacuation area of the Fukushima-Daiichi Nuclear Power Plant (FNPP) accident. 90Sr activity concentrations in the teeth varied from 6–831 mBq (g Ca)−1 and exhibited a positive relationship with the degree of radioactive contamination that the cattle experienced. Even within an individual animal, the specific activity of 90Sr (Bq (g Sr)−1) varied depending on the development stage of the teeth during the FNPP accident: teeth that were early in development exhibited high 90Sr specific activities, while teeth that were late in development exhibited low specific activities. These findings demonstrate that 90Sr is incorporated into the teeth during tooth development; thus, tooth 90Sr activity concentrations reflect environmental 90Sr levels during tooth formation. Assessment of 90Sr in teeth could provide useful information about internal exposure to 90Sr radiation and allow for the measurement of time-course changes in the degree of environmental 90Sr pollution.

A comprehensive dose evaluation project concerning animals affected by the Fukushima Daiichi Nuclear Power Plant accident: its set-up and progress

It is not an exaggeration to say that, without nuclear accidents or the analysis of radiation therapy, there is no way in which we are able to quantify radiation effects on humans. Therefore, the livestock abandoned in the ex-evacuation zone and euthanized due to the Fukushima Daiichi Nuclear Power Plant (FNPP) accident are extremely valuable for analyzing the environmental pollution, its biodistribution, the metabolism of radionuclides, dose evaluation and the influence of internal exposure. We, therefore, sought to establish an archive system and to open it to researchers for increasing our understanding of radiation biology and improving protection against radiation. The sample bank of animals affected by the FNPP accident consists of frozen tissue samples, formalin-fixed paraffin-embedded specimens, dose of radionuclides deposited, etc., with individual sampling data.

Cesium radioactivity in peripheral blood is linearly correlated to that in skeletal muscle: Analyses of cattle within the evacuation zone of the Fukushima Daiichi Nuclear Power Plant

The accident at the Fukushima Daiichi Nuclear Power Plant (FNPP) released a large amount of radioactive substances into the environment. Furthermore, beef contaminated with radioactive cesium above the 500 Bq/kg safety standard was circulated in the food chain in 2011. Japanese consumers remain concerned about the safety of radioactively contaminated food. In our previous study, we detected a linear correlation between radioactive cesium ((137) Cs) activity in blood and muscle around 500 to 2500 Bq/kg in cattle. However, it was unclear whether the correlation was maintained at a lower radioactivity close to the current safety standard of 100 Bq/kg. In this study, we evaluated 17 cattle in the FNPP evacuation zone that had a (137) Cs blood level less than 10 Bq/kg. The results showed a linear correlation between blood (137) Cs and muscle (137) Cs (Y = 28.0X, R(2)  = 0.590) at low radioactivity concentration, indicating that cesium radioactivity in the muscle can be estimated from blood radioactivity. This technique would be useful in detecting high-risk cattle before they enter the market, and will contribute to food safety.

Analysis of Plasma Protein Concentrations and Enzyme Activities in Cattle within the Ex-Evacuation Zone of the Fukushima Daiichi Nuclear Plant Accident

The effect of the Fukushima Daiichi Nuclear Power Plant (FNPP) accident on humans and the environment is a global concern. We performed biochemical analyses of plasma from 49 Japanese Black cattle that were euthanized in the ex-evacuation zone set within a 20-km radius of FNPP. Among radionuclides attributable to the FNPP accident, germanium gamma-ray spectrometry detected photopeaks only from 134Cs and 137Cs (radiocesium) commonly in the organs and in soil examined. Radioactivity concentration of radiocesium was the highest in skeletal muscles. Assuming that the animal body was composed of only skeletal muscles, the median of internal dose rate from radiocesium was 12.5 μGy/day (ranging from 1.6 to 33.9 μGy/day). The median of external dose rate calculating from the place the cattle were caught was 18.8 μGy/day (6.0–133.4 μGy/day). The median of internal and external (total) dose rate of the individual cattle was 26.9 μGy/day (9.1–155.1 μGy/day). Plasma levels of malondialdehyde and superoxide dismutase activity were positively and glutathione peroxidase activity was negatively correlated with internal dose rate. Plasma alanine transaminase activity and percent activity of lactate dehydrogenase (LDH)-2, LDH-3 and LDH-4 were positively and LDH-1 was negatively correlated with both internal and total dose rate. These suggest that chronic exposure to low-dose rate of ionizing radiation induces slight stress resulting in modified plasma protein and enzyme levels.

Association of a single-nucleotide polymorphism in myosin-binding protein C, slow-type (MYBPC1) gene with marbling in Japanese Black beef cattle

Bin Tong*, Seiki Sasaki*, Youji Muramatsu, Takeshi Ohta, Hiroyuki Kose, Hideaki Yamashiro*, Tatsuo Fujita and Takahisa Yamada* *Department of Agrobiology, Faculty of Agriculture, Niigata University, Nishi-ku, Niigata 950-2181, Japan; Department of Nutritional Sciences for Well-being, Faculty of Health Sciences for Welfare, Kansai University of Welfare Sciences, Kashiwara, Osaka 582-0026, Japan; Central Pharmaceutical Research Institute, Japan Tobacco, Inc., Takatsuki, Osaka 569-1125, Japan; Department of Life Science, Division of Natural Sciences, International Christian University, Mitaka, Tokyo 181-8585, Japan; Oita Prefectural Institute of Animal Industry, Takeda, Oita 878-0201, Japan

Electron probe X-ray microanalysis of boar and inobuta testes after the Fukushima accident

We aimed to investigate the effect of chronic radiation exposure associated with the Fukushima Daiichi Nuclear Power Plant (FNPP) accident on the testes of boar and inobuta (a hybrid of Sus scrofa and Sus scrofa domestica). This study examined the contamination levels of radioactive caesium (Cs), especially 134Cs and 137Cs, in the testis of both boar and inobuta during 2012, after the Fukushima accident. Morphological analysis and electron-probe X-ray microanalysis (EPMA) were also undertaken on the testes. The 134Cs and 137Cs levels were 6430 ± 23 and 6820 ± 32 Bq/kg in the boar testes, and 755 ± 13 and 747 ± 17 Bq/kg in the inobuta testes, respectively. The internal and external exposure of total 134Cs and 137Cs in the boar testes were 47.1 mGy and 176.2 mGy, respectively, whereas in the inobuta testes, these levels were 6.09 mGy and 59.8 mGy, respectively. Defective spermatogenesis was not detected by the histochemical analysis of radiation-exposed testes for either animal. In neither animal were Cs molecules detected, using EPMA. In conclusion, we showed that adverse radiation-induced effects were not detected in the examined boar and inobuta testes following the chronic radiation exposure associated with the FNPP accident.

Analysis of the Effect of Chronic and Low-Dose Radiation Exposure on Spermatogenic Cells of Male Large Japanese Field Mice (Apodemus speciosus) after the Fukushima Daiichi Nuclear Power Plant Accident

In this study we analyzed the effect of chronic and low-dose-rate (LDR) radiation on spermatogenic cells of large Japanese field mice (Apodemus speciosus) after the Fukushima Daiichi Nuclear Power Plant (FNPP) accident. In March 2014, large Japanese field mice were collected from two sites located in, and one site adjacent to, the FNPP ex-evacuation zone: Tanashio, Murohara and Akogi, respectively. Testes from these animals were analyzed histologically. External dose rate from radiocesium (combined 134Cs and 137Cs) in these animals at the sampling sites exhibited 21 μGy/day in Tanashio, 304–365 μGy/day in Murohara and 407–447 μGy/day in Akogi. In the Akogi group, the numbers of spermatogenic cells and proliferating cell nuclear antigen (PCNA)-positive cells per seminiferous tubule were significantly higher compared to the Tanashio and Murohara groups, respectively. TUNEL-positive apoptotic cells tended to be detected at a lower level in the Murohara and Akogi groups compared to the Tanashio group. These results suggest that enhanced spermatogenesis occurred in large Japanese field mice living in and around the FNPP ex-evacuation zone. It remains to be elucidated whether this phenomenon, attributed to chronic exposure to LDR radiation, will benefit or adversely affect large Japanese field mice.