Western blot analysis of mice inoculated with BSE/scrapie mixtures. Western blots were performed as described in Materials and methods using antibodies Sha31 (a) and 12B2 (b). Western blots show three mouse lines (C57BL/6, RIII & VM) challenged with 100% BSE (B), 50% BSE (50% BSE) and 100% scrapie (S). Brain tissue from an unchallenged mouse (N) was also analysed. Molecular mass markers (M) are indicated in kDa. All samples were extracted from fresh frozen tissue. Each lane was loaded with 15 μl of neat extracted sample, equivalent to 30 mg of brain tissue.