Abstract
A total of 4000 SPF B6C3F1 mice were divided into four groups [three irradiated groups and one control group], each consisting of 500 male and 500 female mice. Irradiation was performed using 137Cs gamma-rays at dose-rates of 20, 1 and 0.05 mGy/day with accumulated doses equivalent to 8000, 400 and 20 mGy, respectively. Partial results of pathological examination show that malignant lymphomas and soft tissue neoplasms at 20 mGy/day irradiated groups in both sexes appear to contribute to early deaths and consequent shorter life spans. The relationship between life shortening and non-neoplasm death however was not clear. The 20 mGy/day irradiated group appear to show a higher frequency of lung and endocrine neoplasm in females and Harderian gland neoplasms in both sexes. The experiment is currently in progress and is scheduled for completion in year 2004. This interim report is based on data collected from 1996 to the present. (The work is supported by grants from Aomori prefecture, Japan.) [J Radiat Res 44:376 (2003)]
