中文摘要：

目的测定羊瘙痒因子263K经颅内注射感染仓鼠后的LD500方法将感染羊瘙痒因子263K的仓鼠脑组织用生理盐水制成10％（w／v）脑组织匀浆，梯度稀释后感染仓鼠，观察仓鼠的发病情况。以Reed-Mueneh公式计算LD50，用western blot方法检测观察期结束后发病及仍存活的仓鼠脑组织、脾组织中抵抗蛋白酶K的PrP^Sc。结果当颅内接种稀释度由低到高变化时，仓鼠发病的潜伏期及病程同时也由短到长发生变化。发病仓鼠脑组织中可以检测到PrP^Sc，但是PrP^Sc的量在不同的组之间无太大差别。观察期结束后，仍存活的仓鼠脑组织中未检测到具有PK抗性的PrP信号。结论本实验室保存的羊瘙痒因子263K经颅内注射感染仓鼠的LD50为9．2-10g10 LD50 i．C．units／0．001g brain，即当对仓鼠颅内接种10μl羊瘙痒因子263K的10-9．2稀释液时，50％的仓鼠会死亡。

英文摘要：

To determine LD50 of scrapie agent strain 263K in hamsters through intracerebral route, hamsters were infected intracerebrally with 10-fold diluted 10 % homogenates of the infected hamster brain tissues from dilution of homogenates from 10-1 to 10-10 and the LDs0 value was calculated with Reed-Muench＇s method. The presence of PrP^Sc in the brain and spleen tissues of the clinical onset or the living hamsters to resist the action of proteinase K was screened by Western blot analysis. It was found that incubat.ion periods and clinical courses of disease varied greatly with the amounts of infectious agent inoculated, showing a remarkable dose - dependent manner. PrP^Sc could be detected in the brain tissues of the diseased hamsters, but the amount of PrP^Sc in brains was comparable among different groups, indicating that it was not related to the initiative concentration of the infectious agent. Proteinase K- resistant PrP signal was not observed in the brain tissues of the survival animals receiving 10- 9 and 10-10 dilutions of agent at the end of observation. It is concluded the LD50 of scrapic agent 263K kept in our laboratory is 9.2-1og10, that is, the intracerebral inoculation of 10μl of scrapic agent 263K at dilution of 10-9.2 causes 50% of death in the infected hamsters.