Bioassay of PMCA products.

Incubation time to terminal disease stage in individual animals (circles) and in animal groups represented as mean ± S.D. (black bars). Animals were inoculated with 10⁻⁴-fold diluted 263K brain homogenate (group 1); 10⁻⁴-fold diluted 263K brain homogenate sonicated for 48 cycles (a single PMCA round) in the absence of beads (group 2) or presence of 3 large beads (group 3) in the absence of NBH; and 10⁻⁴-diluted 263K brain homogenate subjected to six serial PMCA rounds in the absence of beads (group 4) or presence of 3 large beads (group 5) using 1∶10 dilutions between rounds. After serial PMCA, the amplification products were diluted an additional 10-fold to obtain 10¹⁰-fold dilutions of the original seeds for inoculating groups 4 and 5.