Figure 1. Dose-incubation period curve of brain microsomal fraction from sporadic Creutzfeldt-Jakob disease MM1 (patient 1) intracerebrally injected into Tg40 mice. Each solid circle represents the incubation time for single animal (x-axis) at different brain tissue equivalent dilution. Animals with the same incubation times have overlapping solid circles. Right y-axis is the amount of infectivity present in the inoculum at each brain tissue equivalent dilution (left y-axis). The experimental points were fitted by linear regression curve and 50% infectious dose (ID50) calculated by using probit-nonlinear regression analysis. Dashed lines indicate 95% confidence interval.