Western blot analysis of present cases 1, 2, and 4 and an Austrian FFI case using 3F4 as the primary antibody. PrPres type 1, 2A and 2B standards were run in the lanes as indicated. a: PrPres was undetectable in 200 μl (of 10% wt/vol brain homogenate) after centrifugal concentration. b: Centrifugal concentration (100 μl of 10% wt/vol brain homogenate) shows readily detectable PrPres in the A-FFI case. c: PrPres was undetectable in 500 μl of 10% wt/vol brain homogenate from cases 1, 2 and 4 after NaPTA precipitation. FC, frontal cortex; OC, occipital cortex; CB, cerebellum; TC, temporal cortex; H, hippocampus; Thal, thalamus.