Seventeen-year follow-up study on chromosomal aberrations in five victims accidentally exposed to several Gy of 60Co gamma-rays.

On 25 June 1990, a radiation accident occurred in a (60)Co source radiation unit in Shanghai, due to violations in operation regulations. This accident resulted in the exposure of seven individuals to acute high-dose and dose-rate whole-body external irradiation. Conventional chromosomal aberration analysis, G-banding automatic karyotype analysis and/or fluorescent in situ hybridization (FISH) painting methods were used to analyze chromosomal aberrations in peripheral blood lymphocytes from five of the victims 24 h to 17 years after accidental exposure to 1.9-5.1 Gy of (60)Co gamma-rays. The frequency of unstable chromosomal aberrations (dicentrics and rings) remained at constant levels 1 month after exposure. Three months after exposure, the frequency was reduced by 20-40% in three victims, while no reduction was seen in the other two victims. Twelve years after exposure, the number of dicentrics and rings decreased by more than 90%, and did not reveal a dose-dependent relationship. However, even at 12-17 years after exposure, stable chromosome aberrations, dominated by translocations, remained at a high level in a dose-dependent manner. The frequency of stable chromosomal aberrations detected by FISH showed a similar dose-dependent relationship as that detected by karyotype analysis of G-banding chromosomes. The G-banding analysis also suggested that the pattern of chromosome breakpoints is random. The FISH data showed a decreasing tendency with time for chromosome translocation frequency in the peripheral lymphocytes, and the rate of reduction varied among different individuals. It is likely that the higher dose the victim received, the lesser the translocation frequency decreased with time. The G-banding data also showed that the rate of reduction of translocations is different among individuals. From 5 to 17 years after accidental irradiation, a very small reduction (approximately 10%) of translocation frequency was observed in victims C and D, while there was about a 35% reduction (the highest among the victims) for victim G who received the smallest dose (1.9 Gy). These observations can be used to validate the existence of chromosomal aberrations in peripheral blood lymphocytes as a biological dosimeter for radiation exposures.

[Study on polymorphisms of CYP3A5 gene and their clinical role].

OBJECTIVE: To investigate the polymorphisms of CYP3A5 gene in Chinese population and the association between CYP3A5 genotypes and their clinical functions. METHODS: CYP3A5 gene varisances were detected in 180 samples using denaturing high-performance liquid chromatography(DHPLC), and CsA concentrations in 12 of 180 samples from hemopoietic stem cell transplant recipients were monitored by a commercial fluorescence polarization immunoassay. The data were analyzed by a statistical software. RESULTS: In the 180 samples, there was only one allelic variant CYP3A5*3 with a frequency of 76.1% (274/360), and there were three CYP3A5 genotypes, namely CYP3A5*1/*1, CYP3A5*1/*3 and CYP3A5*3/*3 with frequencies of 5.6%, 36.7% and 57.8% respectively. Also, there were significant differences in CsA concentrations, including standardized trough concentrations C(0) and two-hour peak concentrations C(2), between CYP3A5 CYP3A5*1/*1 and CYP3A5*1/*3 found in 12 hemopoietic stem cell transplant recipients, and both C(0) and C(2) in CYP3A5*1/*1 were lower than those in CYP3A5*1/*3. CONCLUSION: CYP3A5*3 is the primary allelic variant in Chinese population. CYP3A5 genotypes are closely associated with blood CsA concentrations in hemopoietic stem cell transplant recipients, and CYP3A5*1/*1 requires a larger CsA dose to maintain the same blood concentration than does CYP3A5*1/*1. CYP3A5 genotyping by DHPLC may predict recipients' phenotype and CsA dose requirement.