H. pylori and PaCS Figure 1. Identification of PaCS in H. pylori-colonized human gastric epithelium in vivo. (A, 1,000x) and (B, 1,000x) H. pylori (arrows) colonized superficial gastric epithelium stained with toluidine blue shows metachromatic pink areas (arrowheads), mainly infranuclear, surrounded by blue stained (ribosome-rich) cytoplasm. Note in A a dendritic cell (DC; see [ref. 12]) approaching luminal bacteria. Aldehyde-osmium fixed, 0.5-mm- thick resin sections. (B1, 1,000x) TEM of the same epithelium in a consecutive section to B shows identity of the pink structures with PaCSs. A PaCS is enlarged in b2 (6,300x) and further in b3 (31,500x) to show the characteristic particles (left side in b3), to be compared with ribosomes of surrounding RER (right side in b3). Note in b3 direct contiguity of the PaCS with ribosomes and, in the lower right corner, with two RER cisternae (arrows), apparently without admixture of respective contents. (C, 500x) Toluidine blue stained resin section showing on the right a highly colonized, severely damaged epithelium with deeply irregular luminal border (due to cell bulging, desquamation and microerosion), vacuolation and loss of mucin granules in the apical-supranuclear cytoplasm, disappearance of ribosome-related basophilia in the basal cytoplasm and loss of cell polarity, to be compared with a relatively preserved epithelium in the lower left corner and a moderately damaged epithelium upper left. Note several metachromatic areas in lower left (arrowheads), a single fainty stained area upper left and no metachromatic areas in the severely damaged epithelium on the right. (D, 120,000x) High-resolution TEM of barrel-like, randomly oriented PaCS particles, 13 nm thick and 15 to 43 nm long, to show their regular punctate substructure. Compare with more dense, frequently angular ribosomes aligned along RER cisternae in E (120,000x). cs, cisterna; ics, intercellular space; L, gastric lumen; Lp, lamina propria; n, nucleous; sg, secretory granules. doi:10.1371/journal.pone.0009716.g001 PLoS ONE | www.plosone.org 3 March 2010 | Volume 5 | Issue 3 | e9716