Two-mutation models for bone cancer due to radium, strontium and plutonium

Data from beagle experiments and radium dial painters were used to derive two-mutation carcinogenesis models for bone cancer induced by the bone-seeking radionuclides radium, strontium and plutonium. For all data, the model fits indicate that at low doses both mutation rates depend linearly and equally strongly on dose rate. For the high-LET alpha-particle emitters, a cell killing term reduces the second mutation rate at high dose rates. In all cases, the combined effect of both mutation rates is a linear-quadratic dose-effect relationship for cancer at low doses. This behavior may lead to experimental data that could be mistaken as showing a threshold below which no cancers are induced. Derived parameters such as toxicity ratios and tumor growth times compare well with values reported in the literature. Furthermore, results for plutonium indicate that rapid burial of the nuclide in the growing bones of juvenile beagles leads to a significant reduction of its toxicity, as was suggested previously. The results for radium in beagles compare well with those for humans and suggest that the models derived for strontium and plutonium in beagles may be translated to humans. The significant model parameters for the accurate animal data could then also be used to fit human epidemiological data.     

对自然杂志发表的一篇文章的评注

最近自然杂志(Nature,432:383—386,2004)发表了Chengetal.的文章,首次报道了胡氏贵州龙的生育模式、性双形和可能胎生的证据,这无疑是非常重要的,但认为产胡氏贵州龙的竹杆坡组的时代为中三叠世,这与近年来牙形刺的研究结果不符。牙形刺的研究已充分证明竹杆坡组的时代为晚三叠世的早期(卡尼期)(王成源等,1998;Chen&Wang,2002),比以前认为的时代要晚出现大约一千万年。