High expression of the circadian gene mPer2 diminishes the radiosensitivity f NIH 3T3 cells

Period2 is a core circadian gene, which not only maintains the circadian rhythm of cells but also regulates some organic functions. We investigated the effects of mPeriod2 (mPer2) expression on radiosensitivity in normal mouse cells exposed to 60Co-γ-rays. NIH 3T3 cells were treated with 12-O-tetradecanoylphorbol-13-acetate (TPA) to induce endogenous mPer2 expression or transfected with pcDNA3.1(+)-mPer2 and irradiated with 60Co-γ-rays, and then analyzed by several methods such as flow cytometry, colony formation assay, RT-PCR, and immunohistochemistry. Flow cytometry and colony formation assay revealed that irradiated NIH 3T3 cells expressing high levels of mPer2 showed a lower death rate (TPA: 24 h 4.3 percent vs 12 h 6.8 percent and control 9.4 percent; transfection: pcDNA3.1-mPer2 3.7 percent vs pcDNA3.1 11.3 percent and control 8.2 percent), more proliferation and clonogenic survival (TPA: 121.7 ± 6.51 vs 66.0 ± 3.51 and 67.7 ± 7.37; transfection: 121.7 ± 6.50 vs 65.3 ± 3.51 and 69.0 ± 4.58) both when treated with TPA and transfected with mPer2. RT-PCR analysis showed an increased expression of bax, bcl-2, p53, c-myc, mre11, and nbs1, and an increased proportionality of bcl-2/bax in the irradiated cells at peak mPer2 expression compared with cells at trough mPer2 expression and control cells. However, no significant difference in rad50 expression was observed among the three groups of cells. Immunohistochemistry also showed increased protein levels of P53, BAX and proliferating cell nuclear antigen in irradiated cells with peak mPer2 levels. Thus, high expression of the circadian gene mPer2 may reduce the radiosensitivity of NIH 3T3 cells. For this effect, mPer2 may directly or indirectly regulate the expressions of cell proliferation- and apoptosis-related genes and DNA repair-related genes.

Analysis of social factors and human behavior attributed to family distribution of schistosomiasis japonica cases.

An investigation of family distribution patterns of schistosomiasis japonica was carried out in four pilot villages in Yunnan Province. Family clustering of the disease was present in Bihuayuan Village before and after economic reform (site A); however, such clustering did not occur in Tuanshan and Liantie Villages (sites B and C) in the same periods. Being contrary to the stage prior to economic reform family clustering existed in Zhonghe Village (site D) after the reform. The results obtained from single- and multifactor analysis showed that the main human behavior related to family distribution of schistosomiasis in mountainous regions of Yunnan Province included the frequency of laborer migration, contact with cercariae-infested water in public places or family microenvironments with a high transmission potential, promiscuous defecation and status of cattle grazing. The frequency of laborer migration and human contact with cercariae-infested water in public places in sites B and C without family clustering was higher than that in sites A and D with family clustering. Place for promiscuous defecation and cattle grazing in site A converged compared with that in sites B and C.