Fig. 6

High-level cystatin F dimers in plasma rapidly aggravate cognitive impairment in 5xFAD transgenic mice. A Schematic of tail vein injection of 5xFAD mice, behavioural tests, and pathological analysis. B The purified murine cystatin F dimer was identified by western blot analysis. C The level of cystatin F in the plasma of the mice after tail vein injection of purified protein which was detected by ELISA analysis (n = 8). D Immunofluorescence and statistical analysis of Aβ plaques in brain section from transgenic mice that received a tail vein injection. Scale bar: 500 μm E, F ELISA method for measuring Aβ40 and Aβ42 levels in the brain of the mice. G, H ELISA method for measuring Aβ40 and Aβ42 levels in the plasma of the mice. I–L MWM analysis of the latency (s), number of target crosses, and mean speed (cm/s) in the invisible platform test of the mice. M Representative images of the track plots in the MWM test. N The motion traces of the NOR test were displayed. O The recognition index was calculated as described in Material and Methods. The data are presented as the means ± SD and were analysed using Student’s t test. ^*p < 0.05, ^**p < 0.01, ^***p < 0.001