Roles of DNA polymerase β on repair of DNA damaged by γ－rays irradiation

ＲｏｌｅｓｏｆＤＮＡｐｏｌｙｍｅｒａｓｅβｏｎｒｅｐａｉｒｏｆＤＮＡｄａｍａｇｅｄｂｙγ－ｒａｙｓｉｒｒａｄｉａｔｉｏｎＣａｉＪｉａｎｍｉｎｇ（蔡建明）；ＺｈｅｎｇＸｉｕｌｏｎｇ（郑秀龙）；ＬｕｏＣｈｅｎｇｊｉ（罗成基）；ＧａｏＪｉａｎｇｕｏ（高建国...     

Induction of micronuclei in human sperm-hamster egg hybrids at the two-cell stage after in vitro gamma-irradiation of human spermatozoa

The efficiency of the micronucleus test to assess radiation-induced chromosomal damage in human spermatozoa has been investigated. Micronuclei were scored in human sperm-hamster egg hybrids at the two-cell stage, after exposure of human spermatozoa to in vitro gamma-rays at doses of 0.00, 0.10, 0.25, 0.50, 1.00, 2.00, and 4.00 Gy. The relationship between the yield of micronuclei per two-cell stage as well as the percentage of two-cell stages with micronuclei and the different doses of irradiation were fitted to linear equations. To evaluate whether scoring micronuclei is useful for the quantification of chromosomal damage occurring in human spermatozoa, induced micronuclei at the different doses of sperm irradiation were compared to the induction of breaks and fragments in sperm-derived chromosomes. After interspecific fertilization of zona-free hamster oocytes by irradiated spermatozoa, a total of 699 fertilized eggs at the two-cell stage and a total of 387 sperm-derived complements were analyzed. The incidence of fertilized eggs with micronuclei at the two-cell stage coincided well with the incidence of sperm-derived chromosome breaks and fragments (e.g., 8.9% vs. 6.7% in the 0.25 Gy group and 52.8% vs. 58.6% in the 4.00 Gy group). A similar correlation was found between the number of micronuclei per two-cell stage and the number of breaks and fragments per sperm complement (0.09 vs. 0.07 in the 0.25 Gy group and 0.71 vs. 0.81 in the 4.00 Gy group). The results show that this test system can be used for the quantification of spontaneous or induced chromosomal damage in human spermatozoa. © 1995 Wiley-Liss, Inc.     

用荧光玻璃剂量计测量高水平γ剂量

本文介绍了在大剂量情况下,荧光玻璃剂量计的响应特性及其测量方法。用分光光度计测量经大剂量辐照过的荧光玻璃(以下简称大剂量荧光玻璃),在1.84×10¹～2.09×10⁴Gy范围内荧光玻璃的吸光度与吸收剂量有良好的线性关系。用荧光玻璃剂量仪在被测玻璃上面加光吸收片法测量大剂量荧光玻璃,玻璃的吸收剂量为1.84×10Gy时已偏离线性;4.43×10²Gy以上时,荧光强度随吸收剂量的增加而降低。此种方法简易可行。在大剂量情况下,荧光玻璃不经过任何处理,可以在荧光玻璃剂量仪上直接进行测量。     

大剂量γ射线对树突状细胞表型及功能的影响

目的探讨大剂量电离辐射对树突状细胞(DC)表型及免疫功能的影响和辐射致免疫抑制的机制。方法以粒细胞-巨噬细胞集落刺激因子(GM-CSF)和白介素-4(IL-4)诱导造血干细胞产生DC,给予0、10、20、30 Gyγ射线照射,并于照后24 h进行脂多糖(LPS)处理(1μg/ml)使之成熟。用Transwell法研究DC的迁移能力,流式细胞术检测DC表面分子(CD80、CD86、MHC-Ⅱ和CCR7)的表达,ELISA检测细胞因子(IL-6、IL-10和PGE2)的分泌。结果大剂量γ射线对DC的表型无影响,却能抑制DC向CCL19的迁移,同时下调CCR7的表达,减少IL-6、IL-10和PGE2等细胞因子的分泌。结论大剂量γ射线可以通过下调CCR7和诱导凋亡抑制DC的迁移,减少细胞因子的分泌,导致免疫抑制。     

γ射线对薏苡诱变效应的初步研究

目的：研究γ射线对薏苡诱变效应。方法：用薏苡干种子作为诱变材料,以M₁代发芽率、成苗率、苗高、根长为生理效应指标,以M₂代叶绿素突变为诱变效应指标进行了相关诱变研究。结果：γ射线对幼苗生长有明显的抑制作用,具有较强的诱发叶绿素突变的能力。结论：γ射线是一种对薏苡有效的诱变剂。薏苡干种子诱变时γ射线的适宜剂量为450 Gy。     

Relative biological effects of neutron mixed-beam irradiation for boron neutron capture therapy on cell survival and DNA double-strand breaks in cultured mammalian cells

Understanding the biological effects of neutron mixed-beam irradiation used for boron neutron capture therapy (BNCT) is important in order to improve the efficacy of the therapy and to reduce side effects. In the present study, cell viability and DNA double-strand breaks (DNA-DSBs) were examined in Chinese hamster ovary cells (CHO-K1) and their radiosensitive mutant cells (xrs5, Ku80-deficient), following neutron mixed-beam irradiation for BNCT. Cell viability was significantly impaired in the neutron irradiation groups compared to the reference gamma-ray irradiation group. The relative biological effectiveness for 10% cell survival was 3.3 and 1.2 for CHO-K1 and xrs5 cells, respectively. There were a similar number of 53BP1 foci, indicators of DNA-DSBs, in the neutron mixed-beam and the gamma-ray groups. In addition, the size of the foci did not differ between groups. However, neutron mixed-beam irradiation resulted in foci with different spatial distributions. The foci were more proximal to each other in the neutron mixed-beam groups than the gamma-ray irradiation groups. These findings suggest that neutron beams may induce another type of DNA damage, such as clustered DNA-DSBs, as has been indicated for other high-LET irradiation.     

Benign tumors from the human nervous system express high levels of survivin and are resistant to spontaneous and radiation-induced apoptosis

Survivin, an inhibitor of apoptosis, is over-expressed in foetal tissues and human cancers, but it is almost undetectable in normal tissues. Here we have assessed the level of the survivin protein in some benign tumors of the nervous system: meningioma, schwannoma, low-grade ependymoma, pilocytic astrocytoma and pituitary adenoma. Using immuno-blot analysis we present evidence that these low-grade tumors are positive for survivin expression. In agreement, flow cytometrical analysis showed that both spontaneous and radiation-induced apoptosis levels are very low in these neoplasms. Using host cell reactivation assay we have also shown that these tumor cells are proficient in the repair of -ray-induced DNA damage. However, they are deficient in the removal of ultraviolet (UV) light-induced DNA photolesions, especially the shwannoma- and the pituitary adenoma-derived cells. These results suggest that survivin overexpression may be an early event in the stepwise tumoregenesis and hence could be responsible for the onset as well as the growth advantage during tumoregenic progression of malignant as well as benign neoplasms.