Environmental γ-ray doses were measured in Akita prefecture by a NaI (Tl) scintillation surveymeter. The numbers of measurement site were 207 on pavement, 45 on unpaved ground, nine in concrete buildings and nine in wooden houses. The results of measurements, which were subtracted for background (cosmic ray and self-irradiation of the surveymeter), were 31 nSv/h (effective dose rate) on pavement, 27 nSv/h on unpaved ground, 65 nSv/h in the concrete buildings and 34 nSv/h in the wooden houses. The effective dose rate due to environmental γ-ray for the people of Akita Prefecture was estimated taking into account of seasonal change of the dose rate at one site and occupancy factor in the prefecture. The outdoor and indoor dose rates were estimated to be 0.03 mSv/y and 0.33 mSv/y, respectively.
To obtain short culm mutants with lodging resistance, while retaining the other desirable traits, such as an excellent quality of the original variety, dry seeds of a glutinous rice cultivar Mezuru were exposed to gamma-rays. In M3, thirty plants were selected from 4 020 plants, based on the short culm length. From the results of the subsequent yield and adaptability tests, a promising mutant line was called by the name of Sakata-Mezuru as a new cultivar in 1996. This mutant variety was mainly characterized by shortening of each internode, especially the lowest internode, and at harvest it was more adaptable to mechanical work due to the lodging resistance than its parent. It was demonstrated that the grain quality of the mutant equals to or slightly surpasses that of the parent. Sakata-Mezuru has been registered in February of 2001 and officially released.
We examined the effect of low-dose γ-irradiation on proliferation of myeloid leukemia, Ml cells. Ml cells irradiated with 4 cGy showed increased proliferation as determined by cell number, alamar Blue metabolism and DNA synthesis. The increase by low-dose irradiation was observed at every concentration of serum from 1 % to 10%. showing the decrease of the serum requirement in irradiated cells. Furthermore, survival days of SL mice inoculated intraperitoneally with low-dose irradiated Ml cells were shorter than those with sham-irradiated cells. These results shown as the decrease of serum requirement and increase of transplantation ability, indicated the augmentation of leukemia malignancy by low-dose irradiation.