Detection of bovine spongiform encephalopathy (BSE) PrPScby serial potassium dextran sulfate-protein misfolding cyclic amplification. (A) Homogenates (10%) of BSE-infected spinal cords treated in yellow grease at 140°C–180°C for 1 or 3 h were diluted 10–1 with the PrPC substrate and amplified by serial PMCA. Duplicate samples were analyzed after each round (R1–R4) of amplification by western blotting after digestion with proteinase K. The lanes labeled “N” are samples in which only the PrPC substrate was treated in the same manner. Horizontal lines indicate the positions of molecular-weight markers corresponding to 37, 25, 20, and 15 kDa. (B) Homogenates (10%) of the heat-untreated BSE-infected spinal cords were diluted 10–7 to 10–10 with the PrPC substrate and amplified in four tubes by serial PMCA.