High MB-doses increase Tau aggregation. (a) Sarcosyl-extraction of insoluble Tau from cortex tissue of TauRDΔK mice. MB application using a daily dose of 40 mg/kg for 3mo results in an increase of sarcosyl-insoluble human TauRDΔK and endogenous mouse Tau (antibody K9JA). (b) Quantification of (a) shows a ~2-3 fold increase of insoluble Tau after high-dose MB treatment for 3mo. Bars represent mean values ± SEM. Statistics: two-tailed t-test; *: p < 0.05; **: p < 0.01; n, number of samples. (c, d) Gallyas silver staining of Tau aggregates shows an increase of tangle-positive cells inside the hippocampus formation of MB-treated TauRDΔK mice (40 mg/kg for 3mo). Scale bar: 200 μm. Boxed areas indicate close-ups presented in (e-j). Higher magnification of dentate gyrus (DG), CA3 and CA1 hippocampal areas of untreated TauRDΔK mice (e-g) in comparison to corresponding areas of MB-treated TauRDΔK mice (h-j). CA3: region III cornus ammonis; CA1: region I cornus ammonis. Scale bar: 40 μm.