GENETIC TOXICITY IN BACTERIA AND RODENTS

本财政年度已完成了25项微生物致突变性检测和22项体内微核检测。在ILS上，用流式细胞术(FCM)和显微镜对4种化学物质进行了小鼠和大鼠微核计数的比较研究，并公布了数据。已经证明了ILS使用基于流程的MN确定方法的技术转让和熟练程度，根据上述比较研究的结果，基于流程的自动化程序现在已经取代了更劳动密集型和不那么健壮的基于幻灯片的方法。NTP遗传毒性数据库已更新，以接受新的流式派生数据，数据分析方法已更新并编程到数据库中，为分析使用自动流式细胞仪系统获得的大量细胞提供了更合适的方法。量化每个MN的荧光强度作为非整倍体的潜在标记似乎是有用的，并且在那些显示暴露于化学物质后MN频率增加的研究中是常规的。用于测量DNA损伤水平的彗星试验正在ILS的这些体内研究中使用；在急性和亚慢性剂量研究中，正在分析各种组织的诱导DNA损伤。NTP正在建立一个数据库，以确定在NTP研究动物中常规结合彗星分析和MN分析是否为评估化学毒性提供了额外的好处。暴露于一种已知的体细胞染色体损伤诱导剂的小鼠的精子样本正在使用精子鱼CT8试验进行分析，以确定是否检测到暴露于这种化合物的生殖细胞中染色体损伤水平的增加。进行这项工作是为了帮助更好地确定CT8试验在检测生殖细胞诱变剂方面的敏感性。 关键词：微核；Ames试验；沙门氏菌；突变；染色体损伤

25 microbial mutagenicity assays have been completed and 22 in vivo micronucleus assays have been finalized during the fiscal year. At ILS, a comparative study of micronucleus (MN) enumeration in mice and rats by flow cytometry (FCM) and microscopy for 4 chemicals has been completed and the data published. Technology transfer and proficiency at ILS using a flow-based MN determination method has been demonstrated and based on the results of the comparative study mentioned above, the automated flow-based procedure has now replaced the more labor-intensive and less robust slide-based method. The NTP Genetic Toxicity data base has been updated to accept the new flow-derived data, and the data analysis methods have been updated and programmed into the data base, providing more appropriate methods of analyzing the larger number of cells scored with the automated flow cytometry system. Quantification of the fluorescence intensity for each MN as a potential marker for aneuploidy appears to be useful and is routinely done in those studies that show an elevated frequency of MN following exposure to a chemical. The Comet assay for measuring DNA damage levels is being used at ILS in these same in vivo studies; a variety of tissues are being analyzed for induced DNA damage in both the acute and the subchronic dosing studies. NTP is building a data base from which to determine if routinely combining Comet analysis with MN analysis in NTP study animals provides added benefit to assessing chemical toxicity. Sperm samples from mice exposed to a known inducer of chromosomal damage in somatic cells are being analyzed using the sperm FISH CT8 assay to determine if increased levels of chromosomal damage are detected in germ cells as a consequence of exposure to this compound. This exercise is being conducted to help better define the sensitivity of the CT8 assay in detecting germ cell mutagens. Keywords: Micronuclei; Ames test; salmonella; mutation; chromosomal damage