Villus height (A) and crypt depth (B) after 7 days of treatment with either nelfinavir (NFV, 100 mg/kg), indinavir (IDV, 100 mg/kg), zidovudine (AZT, 50 mg/kg) and didanosine (DDI, 100 mg/kg) or PBS. For each animal, a total of 10 villi and 10 crypts were measured for each segment of duodenum, jejunum, and ileum with a micrometer. The results are expressed as mean ± SEM of six mice per group. *statistical significance (P < 0.05) compared to the PBS control group by ANOVA, Bonferroni's multiple test. (C) Illustrative pictures of the effects of CONTROL (PBS), NFV (100 mg/kg), DDI (100 mg/kg), IDV (100 mg/kg), AZT (50 mg/kg) on the intestinal jejunal tissue, showing decreased villi length caused by all antiretrovirals and increased crypt depth caused by AZT.