トロトラスト症患者と原爆被爆者の骨髄細胞、リンパ球にみられた血球小核と染色体異常

As two cytogenetic parameters of radiation exposure, the frequency of micronucleus in erythroblasts, lymphocytes and red cells (Howell-Jolly body) as well as chromosome aberrations in bone marrow cells and in lymphocytes were studied in 24 thorotrast patients and in 32 atomic bomb (A-bomb) survivors who were exposed within one kilometer from the Hiroshima hypocenter. The incidence of both micronucleus and chromosome aberrations in these two exposed groups were significantly higher than that in non-exposed controls. So that these two parameters are useful guide for evaluating the residual effects of radiation, especially on hematopoietic cells. Because of its simple procedures, micronucleus test is also helpful as screening for prediction of chromosome aberrations. The characteristics of lymphocyte chromosome aberrations differed considerably between thorotrast patients and A-bomb survivors; the incidence of unstable type aberrations and intracellular complexity of chromosome aberrations were much higher in the former group. The incidence of micronucleus in erythroblasts and lymphocytes was also higher in thorotrast patients. Such differences are attributable to the differences in the radiation quality (α-ray or γ-ray + neutron) and in the mode of exposure (persistent or single) of these two groups.This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Health and Welfare and the Ministry of Education, Science and Culture

Induction of Apoptosis in CD34+ Cells by Sera from Patients with Aplastic Anemia

To investigate the pathogenesis of aplastic anemia (AA), the apoptosis of CD34+ cells was assayed with annexin V-fluorescein 24hr and 48hr after incubation with the serum of normal controls (n=10), patients with non severe AA (NSAA, n=13) and severe AA (SAA, n=10). The CD34+ progenitors from the bone marrow of normal donors contained a significantly greater proportion of apoptotic cells after incubation with serum from SAA patients than that incubated with serum from normal controls and NSAA. Moreover, the percent apoptosis of CD34+ cells after 24hr incubation with serum from NSAA was slightly higher than that of normal controls. This appears to be related to clinical severity. No significant difference was found in the percent apoptosis of CD34+ cells between incubation for 24hr and 48hr with the same serum. To further explore the mechanism of increased apoptosis induced by the serum of AA patients, the expression of the Fas receptor was measured after incubation with serum from the normal controls and AA patients using flow cytometry. After incubation with serum from the AA patients, the Fas receptor was overexpressed, correlating with the increased apoptosis induced by the same serum from AA patients. In addition, the induction of apoptosis and Fas expression on CD34+ cells by serum from the SAA patients was blocked partly by preincubation of the serum with anti-γ-IFN neutralizing MoAb. These findings suggested that some aberrant components of the serum in the AA patients, which was confirmed partly to be γ-IFN, can induce CD34+ progenitors apoptosis through the Fas signaling pathway. This may contribute to understanding the decreased number of stem cells characteristic of aplastic anemia.This work was supported in part by the Natural Science Foundation of Jiangsu, China (NO. BK97149) and by a grant-in-aid for general scientific research from the Ministry of Education, Science and Culture, Japan (No. 08266109)

Effective doses among residents living 37 km northwest of the Fukushima Daiichi nuclear power plant

We estimated external and internal effective doses for 15 residents who lived approximately 37 km northwest of the Fukushima Dai-ichi Nuclear Power Plant. The average cumulative effective dose was 8.4 mSv for adults and 5.1 mSv for children. The average committed effective dose from 134Cs and 137Cs was 0.055 mSv for adults and 0.029 mSv for children. The committed effective doses for thyroid gland was 27-66 mSv at maximum

Chromosome Aberration Analysis in Persons Exposed to Low-level Radiation from the JCO Criticality Accident in Tokai-mura

Chromosome aberrations were studied in peripheral blood lymphocytes of 43 persons who were exposed to low-level radiation of mixed neutrons and γ-rays resulting from the JCO criticality accident. When the age-adjusted frequencies of dicentric and ring chromosomes were compared with the dose calibration curve established in vitro for ^Co γ-rays as a reference radiation, a significant correlation was observed between the chromosomally estimated doses and the documented doses evaluated by physical means. The regression coefficient of the chromosomal doses against the documented doses, 1.47 ± 0.33, indicates that the relative biological effectiveness of fission neutrons at low doses is considerably higher than that currently adopted in the radiation protection standard

Cytogenetic Abnormalities of Hematopoietic Tissue in Retired Workers of the Ohkunojima Poison Gas Factory

A high incidence of cancer of the respiratory tract has been reported among former workers in a poison gas manufacturing plant which operated on Ohkunojima from 1927 to 1945. This report provides evidence of a high incidence of chromosome abnormality and sister chromatid exchange (SCE) rate among the former workers, as well as cytogenetic changes in two patients among the former workers with chronic myelocytic leukemia (CML). A chromosome study of seven former workers with chronic bronchitis revealed a stable type of aberration, the average abnormality being 10.9 ± 4.4 percent, which is equivalent to those of atomic bomb survivors exposed at 1.2 km from the hypocenter. The SCE rate observed in 16 former workers ranged from 4.9 ± 2.1 to 17.8 ± 3.9, which was significantly higher than in the control group (p<0.03). One of the CML patients showed an extremely high percentage of missing Y chromosomes along with t(9;22) translocation which is a specific chromosome aberration for the disease. Furthermore, the patient had almost a 3 times higher SCE rate compared to the control group and a high incidence of chromosome abnormality (12.1 %) of the peripheral lymphocytes. These results suggest that the development of leukemia in this patient was strongly related to poison gas exposure.This work was supported in part by grants-in-aid from the Ministry of Education, Science and Culture and from the Japan Public Health Association's A-Bomb Survivors Joint Research Team supported by FY 1992 Health and Welfare Ministry A-Bomb Disease Investigation and Research Entrustment Fund (Shigematsu Collaborative Study Group)