characteristics of the scrapie isolates. Nine ovine hindbrain samples that were pooled and incubated with soil (a) were analysed by western blot. Murine isolates (b) designated G338 (lanes 1, 2 and 3), Apl338ii (lane 4), Apl338ii/G338 mixed phenotype (lane 5), Apl338ii/P338 mixed phenotype (Lane 6) and Cag338 (Lane 7) are also shown. Blots were probed with anti-PrP antibody SHa31 and molecular mass markers of 20, 30 and 40 kDa are indicated. All samples were analysed twice to determine the molecular mass of unglycosylated PrPSc and gave consistent results. The strains G338
(c) and Apl338ii (d) were further analysed by the conformational stability assay and gave distinct profiles. These molecular traits were consistent both before (closed symbols) and after (open symbols) treatment with SDS and Napta. Analysis was carried out on 3 murine isolates of G338 and 2 murine isolates of Apl338ii and the presented data is representative of these isolates.