Table 4.

Analysis of the distribution of R2 labeling shows increased labeling on ″small″ neurites and relatively low labeling on dendrites in prion-infected stratum oriens

Compartment	Uninfected		Prion-infected		Row totals	χ2
	Observed	Expected	Observed	Expected		Uninfected	Prion-infected
Large dendrite PM	12.5	6.4	17.5	23.6	30	5.8	1.6
Large axon PM	5	3.7	12.5	13.8	17.5	0.4	0.1
Small neurite PM	36.5	49.9	197	183.6	233.5	3.6	1.0
Large dendrite EE	8	5.6	18	20.4	26	1.1	0.3
Large axon EE	3	4.9	20	18.1	23	0.7	0.2
Small neurite EE	4	15.4	68	56.6	72	8.4	2.3
Neuronal LE	1	1.9	8	7.1	9	0.4	0.1
Synaptic vesicle	2	2.1	8	7.9	10	0.0	0.0
Astrocyte	0	1.3	6	4.7	6	1.3	0.3
Extracellular	10	10.0	37	37.0	47	0.0	0.0
Mitochondrion	30	14.3	37	52.7	67	17.2	4.7
Other	19	15.4	53	56.6	72	0.8	0.2
Total	131		482		613	39.8	10.8

Quantification and analysis of the labeling distributions were performed as described in Materials and Methods and Table 3 legend. The same number of images of uninfected as prion-infected hippocampus were analysed, but PrP levels were higher in the infected hippocampus. The R2 antibody has a lower affinity for PrP than F4–31, and the gold counts were also lower. The total χ² value for R2 labeling was 50.6, and the two distributions were found to be significantly different (p < 0.001 for 11 degrees of freedom). All labeling was included in the analysis shown. However, the difference between the distributions was also highly significant (p < 0.001) if the numbers for mitochondria and myelin (included in the category ″Other″) were excluded from the analysis (data not shown).