Naoki Matsuda

Nagasaki University, Nagasaki, Nagasaki, Japan

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Publications (36)53.1 Total impact

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    ABSTRACT: As a result of the accident at the Fukushima Daiichi Nuclear Power Plant (FNPP) on 11 March 2011, a huge amount of radionuclides, including radiocesium, was released and spread over a wide area of eastern Japan. Although three years have passed since the accident, residents around the FNPP are anxious about internal radiation exposure due to radiocesium. In this study, we screened internal radiation exposure doses in Iwaki city of Fukushima prefecture, using a whole-body counter. The first screening was conducted from October 2012 to February 2013, and the second screening was conducted from May to November 2013. Study participants were employees of ALPINE and their families who underwent examination. A total of 2,839 participants (1,366 men and 1,473 women, 1-86 years old) underwent the first screening, and 2,092 (1,022 men and 1,070 women, 1-86 years old) underwent the second screening. The results showed that 99% of subjects registered below 300 Bq per body in the first screening, and all subjects registered below 300 Bq per body in the second screening. The committed effective dose ranged from 0.01-0.06 mSv in the first screening and 0.01-0.02 mSv in the second screening. Long-term follow-up studies are needed to avoid unnecessary chronic internal exposure and to reduce anxiety among the residents by communicating radiation health risks.
    PLoS ONE 12/2014; 9(12):e114407. · 3.53 Impact Factor
  • Naoki Matsuda, Naoko Morita, Miwa Miura
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    ABSTRACT: The accident at the Tokyo Electric Power Company (TEPCO) Fukushima Daiichi nuclear power plant on March 11, 2011, released a large amount of radioactive materials resulting in the radioactive contamination of a wide area of eastern Japan. Residents of the Fukushima prefecture experienced various unavoidable damages and fear of radiation effects on their health. A reliable communication of accurate risk assessment for residents is required as a countermeasure aimed at the reconstruction of Fukushima. Here, the current status of individual dose estimation and the issues relating to the radiation risk perception are discussed.
    YAKUGAKU ZASSHI 01/2014; 134(2):135-42. · 0.37 Impact Factor
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    ABSTRACT: Ionising radiation (γ or X-rays) is the mandatory tool to treat cancer despite its detrimental effects in particular on skin cells which lead to severe dermatological diseases and carcinogenesis. Natural antioxidants caffeic acid (CA), rosmarinic acid (RA), trans cinnamic acid (TCA), p-coumaric acid (PCA), and hydroxyphenyllactic acid (HPA) acid are known to be potent anticancer and antioxidant agents. Current study is designed to provide experimental evidence as these compounds offer radiation protection for skin cells. Non-toxic concentrations of CA, RA, TCA, PCA, and HPA were tested for radiation protection, γ-radiation induced intracellular reactive oxygen species (ROS) by flow cytometry and DNA double strand break in human keratinocytes (HaCaT cells) by immunocytochemistry. CA, RA and TCA pre-treatment can protect the HaCaT cells by 40%, 20%, 15% respectively through scavenging γ-radiation induced ROS and decreasing number of post irradiation 53bp1 foci. Inclusion of these compounds in chemo-radiotherapy could facilitate to achieve multiple target protection (i.e. anti-cancer and skin radio protectant).
    International Journal of Low Radiation 01/2014; 9(4):305 - 316.
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    ABSTRACT: The hawksbill turtle is an ectotherm, whose sex is determined by temperature during embryonic development. This study aimed to determine whether embryonic hawksbill turtle cells respond differently to temperature than mammalian cells. Embryonic hawksbill turtle cells were established in culture, and thermal effects on these cells were investigated in vitro. Cells were maintained in Dulbecco's Modified Eagle Medium supplemented with non-essential amino acids, vitamin solution, sodium pyruvate, and 10% fetal bovine serum at 33°C and cell proliferation occurred at 25-33°C. When cells were incubated at 37°C (the temperature of mammalian cell culture) for 24 h, cell growth was completely inhibited. This growth inhibition was evidently recovered by changing the incubation temperature back to 33°C. Expression of heat shock protein was found to increase with elevating culture temperature from 25 to 33°C.
    ZOOLOGICAL SCIENCE 12/2013; 30(12):1038-43. · 0.88 Impact Factor
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    ABSTRACT: After the Tokyo Electric Power Company Fukushima Daiichi nuclear power plant accident on March 11, 2011, the reconstruction of early internal radiation doses in residents of Fukushima plays a major role in evaluating their future heath risk, including thyroid cancer by internal radioiodine. Internal radioactivity was measured using a whole body counter (WBC) at the Nagasaki University Medical School to evaluate the health risks of residents and short term visitors in Fukushima. Measurable (131)I, (134)Cs and (137)Cs were detected altogether in 49 out of 196 people who were in Fukushima prefecture at any time during March 11 and April 20, 2011. In 49 people, the 90 percentile of the thyroid equivalent dose by (131)I and the committed effective dose (total effective dose over a lifetime) by the sum of (134)Cs and (137)Cs was 3 mSv and 0.06 mSv, respectively. The radionuclide intakes in early evacuees who left Fukushima before March 16 were more than five times as high as in the responders who moved to Fukushima later. The intake ratio of (131)I/(137)Cs of the earlier evacuees was approximately three. The spatial analysis of 16 evacuees to the south indicated a reduction of internal radioactivity depending on the distance from the nuclear power plant. Among them, high internal (131)I radioactivity in 6 people in a particular evacuation route could be explained by the arrival of a radioactive cloud with a high airborne (131)I/(137)Cs ratio to the environment, as predicted by atmospheric dispersion simulations. Overall, the actual internal radioactivity assessed by a WBC examination comparatively agreed with the predicted airborne radioactivity. These results suggest that the accurate estimation of internal doses in the first week after the radiological accident is critical for the dose reconstruction. The evaluation of internal doses of residents based on their evacuation routes and the advanced estimation of airborne radioactivity from the atmospheric dispersion model should continue to be assessed.
    Radiation Research 08/2013; · 2.70 Impact Factor
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    ABSTRACT: Information on early internal radiation doses in Fukushima after the nuclear power plant accident on March 11, 2011, is quite limited due to initial organizational difficulties, high background radiation and contamination of radiation measuring devices. In Nagasaki, approximately 1,200 km away from Fukushima, the internal radioactivity in evacuees and short-term visitors to Fukushima has been measured by a whole body counter (WBC) since March 15, 2011. A horizontal bed-type scanning WBC equipped with two NaI(Tl) scintillation detectors was used for 173 people who stayed in the Fukushima prefecture between March 11 and April 10, 2011. The average length of stay was 4.8 days. The internal radioactivity was converted to an estimated amount of intake according to the scenario of acute inhalation, and then the committed effective dose and the thyroid dose were evaluated. (131)I, (134)Cs and (137)Cs were detected in more than 30% of examined individuals. In subjects who stayed in Fukushima from March 12 to March 18, the detection rate was approximately 50% higher for each radionuclide and 44% higher for all three nuclides. The maximum committed effective dose and thyroid equivalent dose were 1 mSv and 20 mSv, respectively. Although the number of subjects and settlements in the study are limited, the results suggest that the internal radiation exposure in Fukushima due to the intake of radioactive materials shortly after the accident will probably not result in any deterministic or stochastic health effects.
    Radiation Research 05/2013; · 2.70 Impact Factor
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    ABSTRACT: To evaluate the environmental contamination and contributory external exposure after the accident at the Fukushima Nuclear Power Plant (FNPP), the concentrations of artificial radionuclides in soil samples from each area were analysed by gamma spectrometry. Six artificial radionuclides ((131)I, (134)Cs, (137)Cs, (129m)Te, (95)Nb and (136)Cs) were detected in soil samples around FNPP. Calculated external effective doses from artificial radionuclide contamination in soil samples around FNPP were 1.9-2.9 μSv h(-1) (8.7-17.8 mSv y(-1)) in Fukushima city on 22 March 2011. After several months, these calculated external effective doses were 0.25-0.88 μSv h(-1) (2.2-7.6 mSv y(-1)) in Fukushima city on 29 June 2011. The present study revealed that the detected artificial radionuclides around FNPP mainly shifted to long-lived radionuclides such as radioactive caesium ((134)Cs and (137)Cs) even though current levels are decreasing gradually due to the decay of short-lived radionuclides such as (131)I, (129m)Te, (95)Nb and (136)Cs. Thus, radiation exposure potency still exists even though the national efforts are ongoing for reducing the annual exposure dose closer to 1 mSv, the public dose limit. Long-term environmental monitoring around FNPP contributes to radiation safety, with a reduction in unnecessary exposure to the residents.
    Radiation Protection Dosimetry 04/2012; 151(3):537-45. · 0.91 Impact Factor
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    ABSTRACT: The relationship between the reported ambient dose equivalent (H*(10)) and the individual dose rate recorded by medical staff in Fukushima City after the accident at the Fukushima Daiichi nuclear power plant was evaluated, following a 9.0-magnitude earthquake that struck the east coast of Japan. Personal dose equivalent (H(p)(10)) ranged from 0.08 to 1.63 µSv h(-1) and H*(10) ranged from 0.86 to 12.34 µSv h(-1). H(p)(10) from March to July 2011 were significantly lower than H*(10). The relationships between these dose equivalents were moderately correlated. The regression equation was calculated as follows: H(p)(10)=0.0696×H*(10)+0.0538. The preliminary data of this study show that, in Fukushima, the individual dose is much lower than that determined H*(10). It is important to evaluate H(p)(10) in order to lessen the anxiety of the general population in Fukushima.
    Radiation Protection Dosimetry 01/2012; 151(1):144-6. · 0.91 Impact Factor
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    ABSTRACT: South coast of India is known as the high-level background radiation area (HBRA) mainly due to beach sands that contain natural radionuclides as components of the mineral monazite. The rich deposit of monazite is unevenly distributed along the coastal belt of Tamil Nadu and Kerala. An HBRA site that laid in 2×7 m along the sea was found in the beach of Chinnavillai, Tamil Nadu, where the maximum ambient dose equivalent reached as high as 162.7 mSv y(-1). From the sands collected at the HBRA spot, the high-purity germanium semi-conductor detector identified six nuclides of thorium series, four nuclides of uranium series and two nuclides belonging to actinium series. The highest radioactivity observed was 43.7 Bq g(-1) of Th-228. The individual dose of five inhabitants in Chinnavillai, as measured by the radiophotoluminescence glass dosimetry system, demonstrated the average dose of 7.17 mSv y(-1) ranging from 2.79 to 14.17 mSv y(-1).
    Radiation Protection Dosimetry 04/2011; 146(1-3):314-7. · 0.91 Impact Factor
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    ABSTRACT: Fol-8Col is a novel recombinant collagen-like protein incorporated with foldon sequences derived from the native T4 phage fibritin. In this paper, we examined the potential of using Fol-8Col as scaffold for bone tissue engineering. Circular dichroism (CD) spectra indicate that the triple helix structure of Fol-8Col exists at temperatures ranging from 4 to 40°C. Lactate dehydrogenase assay results and live/death cell staining of osteoblast-like MC3T3-E1 cells, cultivated on Fol-8Col for 24h, showed evidence of cell cytocompatibility comparable to that of native type I collagen. Attachment and spreading of osteoblast-like MC3T3-E1 cells seeded on Fol-8Col were studied by immunofluorescence staining of cell nuclei, vinculin, and F-actin. Intensive focal adhesion patches and an elongated cortical actin cytoskeleton were observed after 24hours’ cultivation. Proliferation assays of MC3T3-E1 cells cultivated on Fol-8Col for 2weeks revealed no consistent differences in rate and pattern compared to growth on type I collagen. Alkaline phosphatase activity assay and osteogenic gene expression, detected by RT-PCR, evaluated the osteogenic differentiation of MC3T3-E1 cells on Fol-8Col. This study shows that Fol-8Col, with a triple helix structure, has good potential for application in bone regeneration as a replacement for native collagen, thereby reducing the risk of contamination.
    Journal of Materials Science 01/2011; 46(5):1396-1404. · 2.31 Impact Factor
  • Advanced Materials Research 08/2010;
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    ABSTRACT: We screened urinary iodine (UI) concentrations in high background radiation areas of the Kanyakumari district of Tamilnadu, India. We collected 331 urine samples from three villages in the district: Chinna-Villai, Kadiyapatinam, and Pallam-Annai nagar. The median UI concentrations were 257, 262, and 454 microg/L in Chinna-Villai, Kadiyapatinam, and Pallam-Annai nagar, respectively. Only 27 samples showed mild or moderate iodine deficiency (<100 microg/L) and none showed severe deficiency (<20 microg/L). These findings indicate that iodine supplementation in the villages is sufficient, probably as a result of appropriate fortification of iodized salt in the region. Further screening, including morphological and functional analysis of the thyroid gland, will be needed to clarify the health effects of chronic low-dose radiation exposure attributable to residing in a high background radiation area.
    Endocrine Journal 09/2009; 57(1):87-91. · 2.02 Impact Factor
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    ABSTRACT: Radiation safety management in Japan stands upon a global framework. The concerted activities of international organizations including the International Commission on Radiological Protection (ICRP), United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), International Atomic Energy Agency (IAEA), and World Health Organization (WHO) form the baseline of radiation safety in Japan by incorporation of their recommendations and guidelines into laws and regulations such as the law concerning Prevention of Radiation Hazards Due to Radioisotopes, etc., and the law for Regulations of Nuclear Source Material, Nuclear Fuel Material and Reactors. To support radiation safety management, the Japan Health Physics Society (JHPS), the Japan Radioisotope Association (JRIS), and the Japanese Society of Radiation Safety Management (JRSM) play their roles by providing seminars, meetings, and publications of updated information on radiation regulations and also for technical transfer. In each radiation facility, a “radiation protection supervisor” entitled by national examination, is required to not only supervise but also promote radiation safety management including radiation monitoring inside/outside control areas and the estimation of external/ internal exposure, education, and training of radiation workers. The goal of radiation safety management is, of course, to reduce the radiation health risk of the public as well as that of radiation workers. The expansion of radiation safety-risk control from legal demand to the daily life of the public, including medical exposure and emergency preparedness, through dosimetry, protection, and education is defi nitely important.
    12/2008: pages 243-247;
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    ABSTRACT: To examine whether nitric oxide (NO) and other radical species are involved in radiation-induced bystander effects in normal human fibroblasts. Bystander effects were modeled by co-culture of non-irradiated cells with X-irradiated cells, and induction levels of micronuclei in co-cultured non-irradiated cells were examined. Three types of radical scavenger, 2-(4-carboxyphenyl)-4,4,5,5- tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO), dimethylsulfoxide (DMSO) and ascorbic acid phosphoric ester magnesium salt (APM), were used to discover which types of radicals are involved in bystander responses. When irradiated cells were treated with c-PTIO, known to be an NO scavenger, the induction of micronuclei in non-irradiated bystander cells was suppressed. On the other hand, bystander effects were most effectively suppressed when non-irradiated bystander cells were treated with ascorbic acid, known to be a scavenger of long lived radicals. These results suggest that NO participates in bystander signal formation in irradiated cells but not in bystander cells that are receiving bystander signals.
    International Journal of Radiation Biology 11/2008; 84(10):809-14. · 1.84 Impact Factor
  • Radiation Safety Management. 01/2008; 7(1).
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    ABSTRACT: Evidence is accumulating that irradiated cells produce some signals which interact with non-exposed cells in the same population via a bystander effect. Here, we examined whether DMSO is effective in suppressing radiation induced bystander effects in CHO and repair deficient xrs5 cells. When 1 Gy-irradiated CHO cells were treated with 0.5% DMSO for 1 hr before irradiation, the induction of micronuclei in irradiated cells was suppressed to 80% of that in non-treated irradiated cells. The suppressive effect of DMSO on the formation of bystander signals was examined and the results demonstrated that 0.5% DMSO treatment of irradiated cells completely suppressed the induction of micronuclei by the bystander effect in non-irradiated cells. It is suggested that irradiated cells ceased signal formation for bystander effects by the action of DMSO. To determine the involvement of reactive oxygen species on the formation of bystander signals, we examined oxidative stress levels using the DCFH staining method in irradiated populations. The results showed that the treatment of irradiated cells with 0.5% DMSO did not suppress oxidative stress levels. These results suggest that the prevention of oxidative stress is independent of the suppressive effect of DMSO on the formation of the bystander signal in irradiated cells. It is suggested that increased ROS in irradiated cells is not a substantial trigger of a bystander signal.
    Journal of Radiation Research 08/2007; 48(4):327-33. · 1.69 Impact Factor
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    ABSTRACT: UV radiation causes cell death through the activation of various intracellular signaling molecules in both DNA damage-dependent and -independent manners. The ability of middle-wavelength UV (UVB) radiation to form DNA photoproducts is less than that of short-wavelength UV (UVC) radiation; however, the differences between UVB and UVC radiation in the extent of DNA damage-independent signaling and its contribution to cell death have not been well characterized. When cells were irradiated with UVB or UVC radiation at doses that generated equivalent amounts of DNA photoproducts, UVB radiation induced more clonogenic cell death, apoptotic cells, mitochondrial cytochrome C release, and intracellular oxidative stress. Among the signaling molecules examined, levels of p53 phosphorylated at Ser-392 and p38 were higher in UVB-irradiated cells than in UVC-irradiated cells. Both phosphorylations were reduced by treating cells with an antioxidant. Furthermore, an inhibitor of p38 also blocked the phosphorylation of p53 at Ser-392. These results suggest that UVB radiation activates the p38 pathway through the generation of oxidative stress, which merges with the DNA p53 pathway by phosphorylation of p53 at ser392. This greater contribution of the DNA damage-independent pathway in UVB-irradiated cells may explain the greater lethality of UVB radiation.
    Radiation Research 07/2007; 167(6):655-62. · 2.45 Impact Factor
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    ABSTRACT: Evidence is accumulating that irradiated cells produce signals, which interact with non-exposed cells in the same population. Here, we analysed the mechanism for bystander signal arising in wild-type CHO cells and repair deficient varients, focussing on the relationship between DNA repair capacity and bystander signal arising in irradiated cells. In order to investigate the bystander effect, we carried out medium transfer experiments after X-irradiation where micronuclei were scored in non-targeted DSB repair deficient xrs5 cells. When conditioned medium from irradiated cells was transferred to unirradiated xrs5 cells, the level of induction was independent of whether the medium came from irradiated wild-type, ssb or dsb repair deficient cells. This result suggests that the activation of a bystander signal is independent of the DNA repair capacity of the irradiated cells. Also, pre-treatment of the irradiated cells with 0.5% DMSO, which suppresses micronuclei induction in CHO but not in xrs5 cells, suppressed bystander effects completely in both conditioned media, suggesting that DMSO is effective for suppression of bystander signal arising independently of DNA damage in irradiated cells. Overall the work presented here adds to the understanding that it is the repair phenotype of the cells receiving bystander signals, which determines overall response rather than that of the cell producing the bystander signal.
    Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 06/2007; 619(1-2):134-8. · 4.44 Impact Factor
  • Genro Kashino, Naoki Matsuda
    RADIOISOTOPES. 01/2005; 54(1):23-25.
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    ABSTRACT: Evidence is accumulating that irradiated cells produce some signals which interact with non-exposed cells in the same population. Here, we analysed the mechanism of such a bystander effect from targeted cells to non-targeted cells. Firstly, in order to investigate the bystander effect in CHO cell lines we irradiated a single cell within a population and scored the formation of micronuclei. When a single nucleus in the population, of double strand break repair deficient xrs5 cells, was targeted with 1Gy of Al-K soft X-rays, elevated numbers of micronuclei were induced in the neighbouring unirradiated cells. The induction of micronuclei was also observed when conditioned medium was transferred from irradiated to non-irradiated xrs5 cells. These results suggest that DNA double strand breaks are caused by factors secreted in the medium from irradiated cells. To clarify the involvements of radical species in the bystander response, cells were treated with 0.5%DMSO 1 hour before irradiation and then bystander effects were estimated in xrs5 cells. The results showed clearly that DMSO treatment during X-irradiation suppress the induction of micronuclei in bystander xrs5 cells, when conditioned medium was transferred from irradiated xrs5 cells. Therefore, it is suggested that radical species induced by ionizing radiation are important for producing bystander signals

Publication Stats

406 Citations
53.10 Total Impact Points


  • 1998–2013
    • Nagasaki University
      • • Center for Frontier Life Sciences
      • • Graduate School of Biomedical Sciences
      • • Division of Radiation Biology and Protection
      • • Department of Basic Pharmaceutical Sciences
      Nagasaki, Nagasaki, Japan
  • 2011
    • Shinshu University
      • Department of Functional Polymer Science
      Shonai, Nagano, Japan
  • 2007
    • Kyoto University
      • Research Reactor Institute
      Kyoto, Kyoto-fu, Japan
  • 2004
    • National Institute of Health Sciences, Japan
      • Division of Medical Devices
      Edo, Tōkyō, Japan