@article{oai:repo.qst.go.jp:00045658,
 author = {Koana, Takao and Sakai, Kazuo and et.al and 酒井 一夫},
 issue = {2},
 journal = {Radiation Research},
 month = {Feb},
 note = {A sex-linked recessive lethal mutation assay was performed in Drosophila melanogaster using immature spermatocytes and spermatogonia irradiated with X rays at a high or low dose rate. The mutation frequency in the sperm irradiated with a low dose at a low dose rate was significantly lower than that in the sham-irradiated group, whereas irradiation with a high dose resulted in a significant increase in the mutation frequency. It was obvious that the dose–response relationship was not linear, but rather was U-shaped. When mutant germ cells defective in DNA excision repair were used instead of wild-type cells, low-dose irradiation at a low dose rate did not reduce the mutation frequency. These observations suggest that error-free DNA repair functions were activated by low dose of low-dose-rate radiation and that this repaired spontaneous DNA damage rather than the X-ray-induced damage, thus producing a practical threshold},
 pages = {217--221},
 title = {Reduction of Background Mutations by Low-Dose X Irradiation of Drosophila Spermatocytes at a Low Dose Rate},
 volume = {167},
 year = {2007}
}