Comparison of PrPres morphology at sites of secondary deposition in mid-thalamic region 3 mm caudal to the needle track injection site in C57 versus tg44 mice at various times after scrapie microinjection. In C57 mice at 40 dpi (a) punctate PrPres is seen in thalamus on ipsilateral side but not on contralateral side. Line denotes middle of brain separating the two sides. Most PrPres is accumulated around cells with visible round nuclei (arrow). (b) At 80 dpi in a C57 mouse PrPres was detected on both sides of brain in thalamus, again mostly around cells with large nuclei (arrow). (c) At 160 dpi in tg44 mice no PrPres was detected at this level in thalamus. However, one perivascular plaque was seen in cortex in 1 of 3 mice (inset). (d) At 213 dpi in tg44 mice several PrPres plaques were seen in thalamus on both sides of brain. At higher power PrPres appeared to be concentrated around capillaries (arrowheads) and larger vessels (arrow). Scale is same in each panel, and bar shown in (a) represents 100 μm.