Data analysis
Data processing and displaying were performed using GraphPad Prism 5
(GraphPad Software, USA). Mean and standard deviation were displayed for
all data sets. Statistical significance was determined using either
Student’s t -test or two-way ANOVA followed by Tukey’s post
hoc test (p < 0.05). Groups with significant
differences are shown with alphabetic letters to signify ranking of
means. Groups indicated with the same letters were not found to be
significantly different.