seven patients with H. pylori-positive active gastritis under first and second 25 minutes incubations. While in Table 3, we com- pared the percentage of DNA damaged gastric epithelial cells in four normal individuals with four H. pylori-positive chronic gastritis under first and second 25 minutes incubations. In Table 4, we compared the percentage of DNA damaged gastric epithelial cells of four normal individuals with four patients with H. pylori -negative active gastritis under second and third 25 minutes incubations. In Table 5, we compared the percentage of DNA damaged gastric epithelial cells of four nor- mal individuals with four patients of H. pylori-negative chronic gastritis under third and fourth 25 minutes incubations. The gastric biopsies were incubated for 25 minutes (first 25 minutes incubation) and the percentages of DNA damaged cells (cometed cells) were calculated, then the same biopsies were washed out with distilled water and incubated for a further 25 minutes (second 25 minutes incubation) and cometed cells per- centages were calculated for comparison with the first 25 min- ute incubation as in Tables 1, 2, and 3. In Table 4, the gastric biopsies were incubated for 25 minutes (first 25 minutes incubation) the cells obtained were ignored and discarded, and then the same biopsies were washed out and incubated for a further 25 minutes (second 25 minutes incuba- tion), the percentages of cometed cells were calculated and the Table 1. Comparison of the Comet Percentages of Normal Gastric Mucosa after the First and Second 25 Minutes Incubation Period Case no. Comet percentages after serials of cell incubations 1st 25 minutes incubation 2nd 25 minutes incubation Table 2. Comparison of the Comet Percentages of H. pylori-Positive Active Gastritis after the First and Second 25 Minutes Incubation Pe- riod Case no. Comet percentages after serials of cell incubations 1st 25 minutes incubation 2nd 25 minutes incubation 1 2 3 4 5 6 7 8 9 10 11 12 13 14 52 58 62 45 48 52 49 46 35 48 40 38 39 42 28 36 47 39 29 38 36 25 30 32 35 27 28 31 35 48 32 43 45 32 22 28 13 12 8 15 13 6 9 12 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Case no. 54 59 46 55 52 40 45 43 35 25 42 55 29 28 35 32 Marie MAM, et al: Extent of DNA Damage and Gastritis in Normal and Helicobacter pylori-Infected Patients 317 Histological diagnosis Normal gastric mucosa Normal gastric mucosa Normal gastric mucosa Normal gastric mucosa H. pylori-positive chronic gastritis H. pylori-positive chronic gastritis H. pylori-positive chronic gastritis H. pylori-positive chronic gastritis Histological diagnosis Normal gastric mucosa Normal gastric mucosa Normal gastric mucosa Normal gastric mucosa H. pylori-negative active gastritis H. pylori-negative active gastritis H. pylori-negative active gastritis H. pylori-negative active gastritis biopsies were washed out and incubated for a further 25 min- utes (third 25 minutes incubation) and percentages of cometed cells were calculated for comparison with the second 25 minute incubation. In Table 5, we compared the percentage of DNA damaged cells (cometed cells) in two different incubation times (third and fourth 25 minutes incubations). The first and second 25 min- utes incubated gastric cells were ignored and discarded. Then the same biopsies were washed out and incubated for a further 25 minutes (third 25 minutes incubation), for which the cells’ percentages were calculated and then the same biopsies were washed out again and incubated for the last 25 minutes (fourth 25 minutes incubation) and cometed cells’ percentages were calculated for comparison with the third 25 minutes incubation. In Table 6, The DNA damaged gastric cells percentage (comet percentages) were allocated to different histological groups, five normal individuals had a mean comet percentage of 71%. Table 3. Comparison of the Comet Percentages of Four Normal In- dividuals and Four H. pylori-Positive Chronic Gastritis Patients after the First and Second 25 Minutes Incubation Period Case no. Comet percentages after seri- als of cell incubations 1st 25 minutes incubation 2nd 25 minutes incubation Table 4. Comparison of the Comet Percentages of Four Normal Indi- viduals and Four H. pylori-Negative Active Gastritis Patients after the Second and Third 25 Minutes Incubation Period Comet percentages after seri- als of cell incubations 2nd 25 minutes incubation 3rd 25 minutes incubation