Assessment of chromosome aberrations in large Japanese field mice (Apodemus speciosus) in Namie Town, Fukushima.

PURPOSE: After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in Japan on March 11 2011, the surroundings became contaminated with radionuclides. To understand the possible biological effects after chronic low dose-rate radiation in contaminated areas of Fukushima, we assessed the effects in large Japanese field mice (Apodemus speciosus) by means of chromosome aberration analysis. MATERIALS AND METHODS: We collected A. speciosus in five sites around Namie Town, Fukushima (contaminated areas) and in two sites in Hirosaki City, Aomori (control areas, 350 km north of FDNPP) from autumn 2011 to 2013. The number of mice captured and ambient dose-rates were as follows: high (n = 11, 10.1-30.0 µGy h-1), moderate (n = 10, 5.7-15.6 µGy h-1), low (n = 12, 0.23-1.14 µGy h-1) and control (n = 20, 0.04-0.07 µGy h-1). After spleen extraction from rodents, spleen cell culture was performed to obtain metaphase spreads. Chromosome aberrations were assessed on Giemsa-stained metaphase spreads. RESULTS: Although the mice in the contaminated areas were chronically exposed, there was no radiation-specific chromosome aberrations observed, such as dicentric chromosomes and rings. Some structural aberrations such as gaps and breaks were observed, and these frequencies decreased annually in mice from Namie Town. CONCLUSION: These findings suggest that chromosome aberration analysis is useful to evaluate and monitor radiation effects in wild animals.

Confounding by dietary factors in case-control studies on the efficacy of cancer screening in Japan.

Evaluation of cancer screening using case-control studies is less valid in comparison to randomized controlled trails, due to the intrusion of a possible self-selection bias in the former. The randomized controlled trial approach, however, may be difficult in developed countries where mass cancer screening programs are already being performed nationally. Accordingly, case-control studies are often performed instead of randomized controlled trials. In case-control studies, no reports could be found in the literature using dietary habit, an important influencing factor in carcinogenesis, as an adjusting item. We surveyed nutrition and food intake status through a nutrition survey using the weighing method, and smoking prevalence and alcohol consumption with questionnaires in the general population in northern Japan, in subjects over 30 years of age. We then compared these results among non-participants and participants in cancer screening programs, and evaluated how any differences between the two groups might affect the results of case-control studies. Non-participants had a significantly lower intake of vegetables, carotene, vitamin C, and dietary fiber, which are thought to be beneficial factors in the prevention of carcinogenesis. Non-participants had a significantly higher cigarette smoking prevalence than participants. In relation to the intake of vegetables, a difference between participants and non-participants was evident, as proper adjustment for vegetable intake led to an odds ratio closer to the null value. The value of the odds ratio will probably not decrease, but it might increase when other dietary factors or smoking are taken into consideration.