Data presented are means ±SEM. Statistical analyses were performed using SigmaStat (Systat). Statistical differences for one factor between two groups or more than two groups were determined using an unpaired Student’s t-test or an analysis of variance (ANOVA) with a post-hoc test, respectively. Statistical differences for two factors between more than two groups were determined using a two-way ANOVA with a post-hoc test. Values of P<0.05 were considered statistically significant.
