Effect of various samples of Helicobacter LPS on histamine (10−4 M)-stimulated acid secretion in the mouse gastric glands as measured by [14C]AP accumulation. PI, H. pylori isolate from a duodenal ulcer patient; NCTC/p, H. pylori NCTC 11637 (phenol phase); NCTC/w, H. pylori NCTC 11637 (water phase); SS1, the Sydney strain of H. pylori; HF, H. felis; ∗, P < 0.05. n = 8 or 9.