Endemic areas of human T-lymphotropic virus type 1 (HTLV-1) have been reported in Japan as well as tropical Africa, Central and South America and Melanesia. The existence of two subgroups, i.e., the transcontinental and Japanese subgroups, was reported in Japan. In the present study, we provide data on the ratio of the two subgroups in each endemic area and infection foci and examine the distribution of HTLV-1 in Japan and neighboring areas. A 657 bp fragment of env region of HTLV-1 proviral genome was successfully amplified for 183 HTLV-1 positive DNA samples. The subgroup determination was done by RFLP reactions using endonucleases HpaI and HinfI. The northern part of mainland Kyushu, represented by Hirado and Kumamoto, was monopolized by the Japanese subgroup, while the transcontinental subgroup ranged from 20 to 35% in the Pacific coast areas of Shikoku (Kochi), the Ryukyu Archipelago (Kakeroma and Okinawa) and Taiwan. An interesting finding in the present study is the presence of the transcontinental subgroup in Kochi, suggesting the endemicity of the transcontinental subgroup along the Kuroshio Current.

　　The purpose of the present study was to reduce absorbed dose rates in air by means of the X-ray tube protector in the X-ray fluoroscopy room. We measured absorbed dose rates in air using an ionization chamber type survey meter, made the scatter radiation maps and worked out the reduction rate of absorbed dose rates in air. Absorbed dose rate in air reduced 75-90% with use of the X-ray tube protector. Especially, absorbed dose rate in air reduced 85-90% at the height of crystalline lens and thyroid gland of the X-ray technician near the patient. It was suggested X-ray protector could reduce the risk of radiation exposure of radiologists effectively.