FIGURE 8.

Survival and neuritogenesis of PC12 cells treated with purified NGF or muteins. A, survival (trypan blue) and differentiation were determined (as in Fig. 4 and Fig. 7) after treatment with purified mβNGF, 7-84-103 (SS-1), and Δ9/13 at the concentrations indicated. Cells bearing neurites were counted after 48 h of treatment in defined medium. Relative survival at 72 h was calculated as a percentage of the fold increase in survival with respect to buffer alone. Calculated relative survival = {(actual % survival for sample/actual % survival for buffer) − 1} × 100%. The actual survival observed for buffer alone was 45.2% and that for wtNGF (2 nm) was 81.3%. Data are presented as mean ± S.D. with n = 3 independent assays per data point. *, unadjusted p < 0.001 significantly different for % differentiation with respect to buffer; #, unadjusted p < 0.001 significantly different for % relative survival with respect to buffer. Statistical significance was calculated by one-way analysis of variance using the Holm-Sidak method in SigmaPlot. B, dose-response curve for neurite outgrowth. C, dose response for survival (trypan blue). These data were obtained as described in A at varying concentrations.