TABLE 2.

Scrapie incubation period in murine neuroblastoma (N2A) and C2C12 myoblast and myotube cell lysates

Samplea	Trial 1b			Trial 2
	Incubation period, days (mean ± SD)c	No. affected/no. inoculated	No. of times cultures were passed after scrapie infection	Incubation period, days (mean ± SD)	No. affected/no. inoculated	No. of times cultures were passed after scrapie infection
22L scrapie-infected brain	137 ± 7d	5/5	NAe	NDf	NA	NA
22L scrapie-infected N2A cells	125 ± 7.6*	5/5	19	138 ± 2.2	5/5	15
22L scrapie-infected C2C12 myoblasts	138 ± 6.2*	6/6	17	145 ± 4.3	6/6	14
22L scrapie-infected C2C12 myotubes	132 ± 2.2	5/5	17	137 ± 1.7	4/4	14
22L A3 scrapie-infected C2C12 myoblasts	ND	NA	NA	139 ± 6.4	4/4	18
22L A3 scrapie-infected C2C12 myotubes	ND	NA	NA	133 ± 0.6	3/3	18
C2C12 myoblasts	>250	0/5	17	>205	0/3	14
C2C12 myotubes	ND	NA	NA	>205	0/3	14

^aFor the brain sample, a 1% (wt/vol) homogenate was used. For all other samples, a 56-cm² tissue culture at ∼90% to 100% confluence was trypsinized and resuspended in phosphate-buffered saline, and the total cell lysate was inoculated into each group of mice.

^bTrials represent C2C12 muscle cells and N2A cells from independent scrapie infection experiments.

^cBrain homogenates or tissue lysates were intracerebrally inoculated into C57Bl/6 mice and the time to onset of clinical disease was measured. *, Tukey's Studentized range test, P < 0.05.

^dThe presence of PrP^Sc in the brains of all clinically ill mice was confirmed by Western blotting.

^eNA, not applicable.

^fND, not done.