(A) Worms expressing human wild-type α-synuclein–YFP in muscle cells (strain NL5901) were fed indicated dosages of PFFs or monomer (MON), or buffer alone, on day 1 of adulthood. Worms expressing YFP in muscle without transgenic α-synuclein expression (strain AM134) were also fed PFFs on day 1. On day 2, α-synuclein aggregates were imaged. Scale bar, 50 μm. (B) Quantification of # α-synuclein aggregates per worm in the head region after treatment with 0.1 ng/μl PFF or MON. n = 6 for each group on day 2 except n = 7 for MON, n = 8 for each group on day 3 except n = 10 for PFF, n = 7 for each group on day 4 except n = 9 for MON. Data are mean ± SEM. two-way ANOVA. (C) Quantification of # α-synuclein aggregates per worm in the head region after treatment with 0.25 ng/μl PFF or MON. For day 2, n = 6 for Buffer, 12 for PFF, 8 for MON. For day 3, n = 10 for Buffer, 9 for PFF, 13 for MON. For day 4, n = 7 for Buffer, 8 for PFF, 10 for MON. Data are mean ± SEM. Two-way ANOVA with Tukey’s post hoc test. (D) Quantification of # α-synuclein aggregates per worm in the head region after treatment with 0.5 ng/μl PFF or MON. n = 7 for each group on day 2 except n = 6 for PFF, n = 9 for each group on day 3 except n = 8 for MON, n = 9 for each group on day 4 except n = 8 for MON. Data are mean ± SEM. Two-way ANOVA with Tukey’s post hoc test. (E) Quantification of # α-synuclein aggregates per worm in the head region after treatment with 1 ng/μl PFF or MON. For day 2, n = 6 for Buffer, 9 for PFF, 10 for MON. For day 3, n = 9 for Buffer, 5 for PFF, 9 for MON. For day 4, n = 8 for Buffer, 9 for PFF, 8 for MON. Data are mean ± SEM. Two-way ANOVA with Tukey’s post hoc test. ns, not significant. *P < 0.05, **P < 0.01, ****P < 0.0001.