Experimental design and histopathological findings. A: Experimental design. Five- to six-week-old male C57BL/6J mice were inoculated with H. pylori SS1 strain (Groups B and D) or Brucella broth (Groups A and C). All animals were administered 120 ppm MNU in their drinking water on alternate weeks (total exposure, 5 weeks). Mice of Groups C and D were given basal diet (CE-2) containing 10% NaCl. B: Histopathological findings for MNU-induced mice gastric tumors. (a and b) Gastric adenoma in the pyloric region of an MNU-treated and H. pylori-infected mouse (Group B). (c and d) Gastric adenocarcinoma observed in Group B. Note the high cell density and cellular and structural atypia. Bar = 200 (a and c) or 100 μm (b and d).