Scholarly summary

Centrifugation of post-ribosomal supernatant fluids of brain homogenates at high speed for a prolonged period yielded a transparent pellet material. Resuspension of this pellet followed by centrifugation on a caesium chloride gradient resulted in a sharp band at a density of 1"34 g./cm. 3. The band material sedimented as a single peak of approximately 5 S in the analytical ultracentrifuge and had scrapie activity. Although the position of the band and its S value are similar in normal and scrapie-affected mice there was an increased incorporation of [3H]thymidine and [14C]uridine-diphospho-glucose into the gradient fractions immediately above and into the band at a density of I-3 to 1.34 g./cm? in scrapie-affected mice. Chromatography of the resuspended post-ribosomal pellet on Sepharose 4 B yielded two peaks. In scrapie-affected mice, incorporation experiments showed an area between the two peaks with increased incorporation of [aH]thymidine, [14C]uridine-diphospho-glucose and p4C]glucosamine. Experiments on spleen homo-genates yielded comparable r sults