Exposure to ionizing radiation results in the generation of reactive oxygen species that induce DNA damage in the form of mutations. EGCg((-)-epigallcatechin gallate) is considered to be a radioprotective agent. The radical scavenging effect of EGCg on γ-rays irradiated plasmid DNA was evaluated. The numbers of double strand breaks of pUC118DNA in the presence or absence of EGCg were monitored by agarose-gel-electrophoresis. Moreover, the protective effects of EGCg in yeast cells exposed to radiation were measured, and the mutation frequencies of yeast cells exposed to radiation were also measured in the presence or absence of EGCg. The yield of closed circle plasmid DNA after γ-ray irradiation increased in the presence of EGCg. EGCg reduced the DNA damage induced by γ-ray irradiation. Our results show that the mutation frequency induced by γ-ray irradiation was reduced by EGCg(400nM), and indicate that EGCg is useful for providing protection against the harmful effects of ionizing radiation.
In order to develop a simple but reliable radiation detector for the general public, photon detection performances of radiation sensors have been studied in photon calibration fields and by Monte Carlo simulations. A silicon p-i-n photodiode and a CdTe detector were selected for the low cost sensors. Their energy responses to ambient dose equivalent H*(10) were evaluated over the energy range from 60keV to 2MeV. The response of the CdTe decreases markedly with increasing photon energy. On the other hand, the photodiode has the advantage of almost flat response above 150keV. The sensitivities of these sensors are 4 to 6 cpm for the natural radiation. Detection limits of the radiation level are low enough to know the extreme increase of radiation due to emergency situations of nuclear power plants, fuel treatment facilities and so on.
Strontium-89 (89Sr) is a radiopharmaceutical which accumulates in bone metastases showing increased calcium metabolism, emits β particles, and is used for palliative treatment for bone pain. A total of 65% - 90% of the patients demonstrated an improvement of the pain symptoms. This agent is available for clinical use since October 2007 in Japan. Though it can be administered in outpatient clinics, some cautions must be taken because of its long physical half-life, bone marrow toxicity as a side effect, and so on. The guidelines published for 89Sr treatment procedures must be referred for the appropriate administration. Further academic investigations are expected such as tumoricidal effect of the agent, bremsstrahlung imaging with scintillation camera, combined radionuclide and chemotherapy, and so on.
Concentrations of 134Cs, 137Cs and 40K in mushrooms cultivated in Saitama prefecture and those substrates were measured by gamma-ray spectrometry. In all mushrooms and substrates, 134Cs was not detected. Concentrations of 137Cs in mushrooms were in the range of 0.012-2.1Bq/kg·fresh, and those in substrates were in the range of 0.080-1.8Bq/kg·dry. Concentrations of 137Cs in mushrooms varied widely with mushroom species, and the average concentration of 137Cs in Lentinus edodes (Shiitake) was over 30 times higher than that in Pleurotus ostreatus (Hiratake). Mushroom-to-substrate concentration ratios of 137Cs (fresh/dry) were 0.11-0.53. They were higher than the reported transfer factors for common agricultural plants.