**2.8 Statistical analysis**

Results are expressed as the mean ± standard error of the mean (S.E.M). The differences between groups were analyzed by Mann-Whitney U test and, if appropriate, by Kruskal-Wallis ANOVA test. Survival curves were analyzed by the Kaplan-Meyer log-rank test. Changes in body weight were compared by use of the Wilcoxon matched-pair signed-rank test. A value of P <0.05 was considered significant.
