Statistical analysis
All data analyses were performed in SAS 9.2 (SAS Institute Inc., NC,
USA), and graphs were produced with Origin 8.0 (Origin Lab, MA, USA).
Data were presented as mean ± SEM. Analysis of variance was performed
using the ANOVA procedure in SAS 9.2. If the differences between
treatments were significant, multiple comparisons were performed using
the Tukey method. Statistical significance was considered P <
0.05.