Experimental Studies on the Carcinogenicity of Man Made Fibers

对气管内注射闪石石棉、铁石棉和青石棉两年后的雌性叙利亚仓鼠进行了组织学观察，以评价6种细小人造纤维的致瘤性。研究表明，某些类型的人造纤维比石棉具有更强的诱发肿瘤的能力。此外，作为人造纤维组的一项特殊观察，肿瘤是在内皮器官而不是在胸腔诱发的。由于胸膜增厚与间皮瘤的发生率无关，提示内脏胸膜增厚可能是由不同于纤维材料致瘤性的机制引起的。我们通过测定几种体外条件下8-羟基-2‘-脱氧鸟苷(OH^8DG)的产量，比较了石棉和人造纤维对DNA的攻击能力。结果表明，石棉对DNA有损伤作用，可导致DNA发生点突变，几种人造纤维在一定条件下具有与石棉相似的作用。以Wistar大鼠(雌性，4周龄)饲喂缺铁或缺锰缺铜饲料8周，观察元素缺乏对DNA氧化损伤的影响。结果表明，患癌症的风险可能与次要和必要元素的摄入量有关。我们还测定了2-硝基丙烷染毒的雄性SD大鼠再生肝(肝部分切除后24、48、72小时和7天)肝细胞核DNA中OH8DG的含量，以验证肝部分切除后对致癌物高度敏感与细胞增殖期DNA损伤敏感性有关的假说。这表明，细胞增殖过程中的核DNA，如细胞受到纤维状物质的持续损伤，正处于对外源活性氧物种攻击敏感的阶段。

Histological observations were performed on female Syrian hamsters two years after the intratracheal administration of amphibole asbestos, amosite and crocidolite, to evaluate the tumorigenicity of six types of fine man-made fibers. It was demonstrated that some type of man-made fibers had a potency to induce tumors much more than asbestos. Moreover, as a specific observation in man-made fiber groups, tumors were induced at intracelial organs rather than at the pleural cavity. It was suggested that the thickening of visceral pleura might be induced by a different mechanism from the tumorigenicity of fibrous materials, since there was no relation between the pleural thickening and mesothelioma incidence in hamsters.We compared the potential of asbestos and man-made fibers to attack DNA by the determination of the yield of 8-hydroxy-2'-deoxyguanosine (oh^8dG) in several conditions in vitro. It was suggested by the result that asbestos could damage DNA which resulted in oh^8dG as a cause of point mutation and also several types of man-made fibers had similar effects as asbestos under certain conditions.Rats(Wistar, female, 4 week-old) were fed iron-deficient or manganese and copper-deficient diets for 8 weeks to determine the oxidative damage of DNA in element deficiency. Results suggest that the risk of cancer may be associated with the minor and essential element intake. We also determined the amount of oh^8dG in the nuclear DNA of regenerating liver (24, 48, 72 hours and 7 days after partial hepatectomy) of male Sprague Dawley rats exposed to 2-nitropropane for the verification of a hypothesis that a high sensitivity to carcinogens after partial hepatectomy is responsible for the sensitivity of DNA damage in the cell proliferating stage. It is suggested that nuclearDNA in a proliferating cells, e.g., cells in continuous cell damage by fibrous materials, is in a sensitive stage to exogenous attack by active oxygen species.