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. 2005 Jun 8;25(23):5533–5543. doi: 10.1523/JNEUROSCI.4883-04.2005

Figure 4.

Figure 4.

Quantitation of APP and its metabolites in neuronal cultures over time. The levels of various proteins were quantified using Western blotting and film densitometry. For each graph, sister cultures containing the same number of rat neurons were collected at the indicated days after plating. At least three independent batches were quantified for each data point. To normalize for possible batch-to-batch variability, the levels at each time point in a given batch were normalized to the ubiquitous enzyme GAPDH in the same sample. a, Full-length APP levels increased over time. **p < 0.05 using linear regression analysis. b, Quantitation of AICD over time. Note the approximate twofold rise in its level at DIV 6 and 7, which is statistically significant (**p < 0.01). The increase at DIV 5 was also statistically significant (p < 0.01). c, The level of C83 exhibits a similar pattern as AICD, with an approximate threefold increase at DIV 6 and 7 (**p < 0.01). d, α-Secretase activity was measured by quantifying APP-α in the conditioned media of four independent batches of neurons. For each data point, media were conditioned for 1 d, and the values were normalized to the relative level of full-length APP. e, Aβ secreted into the medium was quantified using a sensitive and specific sandwich ELISA (Aβx-40) and normalized to APP levels in the corresponding neuronal lysate. Aβ increased linearly over time (***p < 0.001) based on linear regression analysis.