Figure 1.

Nicotinamide rescues TPrP-damaged neuroblastoma cells. (A) Dose-dependent protection of nicotinamide against TPrP-induced toxicity (2.5 µg/ml TPrP). Nicotinamide was added at Day 3, cell survival measured at Day 5. Statistical differences are shown compared to the untreated control (**P < 0.01). Triplicate samples are shown with standard deviations. (B) Time-course phase-contrast micrographs illustrating the rescue of TPrP-injured neurons by nicotinamide. Nicotinamide (8 µg/ml) was added to neurons previously exposed to 5 µg/ml TPrP for 3 days (lower panels). At Day 3 post-TPrP exposure, neurons are rounded and vacuolated. In the absence of nicotinamide rescue (upper panels), at Day 4 vacuolation is severe, and at Day 6 most neurons are dead. Three hours after onset of nicotinamide treatment (lower panels), neurons resume their elongated shape and vacuoles disappear. Two days later, they harbour a perfectly healthy morphology. Pictures of cells exposed to TPrP in the presence or absence of nicotinamide treatment were taken from the same area in the cell culture to allow for a longitudinal study of the cell’s fate. Arrows show examples of individual cell tracking. Individual cell follow-up was not possible at Day 2 post-nicotinamide treatment as healthy cells moved in the culture. The experiment was done four times.