Effect of Helicobacter pylori infection on gastrin secretion in patients with duodenal ulcer : The association between antral G and D cells and mucosal inflammation, atrophy, and Helicobacter pylori infection in subjects with normal mucosa, chronic gastritis, and duodenal ulcer Comparison of meal-stimulated serum gastrin response in Helicobacter pylori-positive duodenal ulcer and asymptomatic volunteers with and without Helicobacter pylori infection