EFFECTS OF RADIATION ON MAMALIAN CELLS

该研究计划的长期目标是获取知识 concerning the mechanisms involved in the response of 哺乳动物细胞对辐射的影响，特别是其 致癌和致突变作用。 该方法是一种多 faceted one, and the endpoints under investigation include 诱变、恶性转化、细胞存活和 诱发染色体异常。 该程序具有双重 目的：一是更好地界定低水平辐射的风险 exposure by examining the role of factors such as total dose, dose-rate, LET and the intracellular distribution of dose on 诱变和转化；其次，了解更多 the cellular and molecular mechanisms for these effects. 的 具体目标是： 1）识别在 辐射恶变过程。 转染 将定期将 DNA 导入 NIH 3T3 细胞 10T1/2细胞培养物照射后；来自原代和 secondary transfectants will be examined by Southern blotting and 对特定单克隆抗体的反应性。 2）检查 各类电离辐射的直接致突变作用 the c-Ha-ras proto-oncogene by transfection of the irradiated 质粒载体中的基因。 3) 考察影响因素 人类的形态转变和永生化 二倍体成纤维细胞。 将特别关注以下方面的研究： DNA fragment derived from the second intron of c-myc which induces specific morphologic alterations in a strain of partially 转化的细胞。 我们建议确定这一推定 regulatory element by deletion analysis and sequencing, and 进一步研究其在转化中的作用。 4) 分析 molecular structure of spontaneous and induced mutations at the TK6 人类细胞系中的常染色体 tk 基因座。 适当的 probes will be obtained and restriction fragment or sequence 寻找多态性标记。 分子生物学技术将 以确定是否大规模 changes we have observed involve gene conversion, mitotic 重组或多位点缺失事件并估计 他们的程度。 5) 进行突变体的细胞遗传学分析 克隆以确定是否存在大规模 DNA 结构 changes are associated with visible chromosomal abnormalities. Results will be correlated with those of dosage blots. 6) 到 analyse the spectrum of molecular structural changes induced by 不同类型的辐射，包括快中子、重离子 和俄歇发射放射性核素。 7) 继续研究 转化的相对生物有效性和 低剂量、低剂量率中子暴露的诱变。 8) 至 研究高 LET 剂量微观分布的作用 使用俄歇法测量细胞内辐射对其生物效应的影响 发射电子的放射性核素。 重点将放在诱变上 在人类 TK6 细胞中。

The long term goal of this research program is to gain knowledge concerning the mechanisms involved in the response of mammalian cells to radiation, with particular reference to its carcinogenic and mutagenic effects. The approach is a multi- faceted one, and the endpoints under investigation include mutagenesis, malignant transformation, cell survival and the induction of chromosomal abnormalities. The program has a dual purpose: first, to better define the risks of low-level radiation exposure by examining the role of factors such as total dose, dose-rate, LET and the intracellular distribution of dose on mutagenesis and transformation; and second, to learn more about the cellular and molecular mechanisms for these effects. The specific aims are: 1) To identify oncogenes activated during the process of malignant transformation by radiation. Transfection of DNA into NIH 3T3 cells will be carried out at regular intervals after irradiation of 10T1/2 cell cultures; DNA from primary and secondary transfectants will be examined by Southern blotting and reactivity to specific monoclonal antibodies. 2) To examine the direct mutagenic effects of various types of ionizing radiation on the c-Ha-ras proto-oncogene by transfection of the irradiated gene in a plasmid vector. 3) To examine factors involved in the morphological transformation and immortalization of human diploid fibroblasts. A particular focus will be on the study of a DNA fragment derived from the second intron of c-myc which induces specific morphologic alterations in a strain of partially transformed cells. We propose to identify this presumptive regulatory element by deletion analysis and sequencing, and furthur study its role in transformation. 4) To analyze the molecular structure of spontaneous and induced mutations at the autosomal tk locus in the TK6 human cell line. Appropriate probes will be obtained and restriction fragment or sequence polymorphic markers sought. Molecular biological techniques will be employed in order to determine whether the large-scale changes we have observed involve gene conversion, mitotic recombination or multi-locus deletion events and to estimate their extent. 5) To carry out cytogenetic analysis of mutant clones in order to determine whether large scale DNA structural changes are associated with visible chromosomal abnormalities. Results will be correlated with those of dosage blots. 6) To analyse the spectrum of molecular structural changes induced by different types of radiation including fast neutrons, heavy ions and Auger emitting radionuclides. 7) To continue studies of the relative biological effectiveness for transformation and mutagenesis of low dose, low dose-rate neutron exposure. 8) To investigate the role of microdistribution of dose of high LET radiation within the cell on its biologic effects by use of Auger electron emitting radionuclides. Emphasis will be on mutagenesis in human TK6 cells.