English: "(a) HPLC analysis of the in vitro digestion of 10 μg of a damaged oligodeoxynucleotide (5′-d(UUUUC)-3′) with a digestive enzyme mix, gastric lysate, or gastrointestinal lysate at 37 °C for 24 h. (b) Levels of dU and (c) control 8-oxo-dG in gDNA extracted from the intestines of control (−) and damaged DNA-fed mice (+), showing >10-fold increases in levels of dU in the genomic DNA from later small intestinal tissue. (d) Immunostaining of γ-H2AX in villi of the small intestine (ileum), showing enhanced DNA double-strand break (DSB) signals (in red) in response to damaged oligonucleotide feeding for 1 week. (e) Quantification results of red fluorescence (level of γ-H2AX) measured from epithelial cells in panel d. ****p ≤ 0.0001 by the unpaired t test. Tissues were co-stained with blue Hoechst 33343 (5 μg/mL) to highlight nuclear DNA. Uncertainties are standard deviations."