The samples were fixed in 2.5% glutaraldehyde in 0.1 M sodium phosphate buffer (pH 7.2) at 4 8C overnight, and next post-fixed for 1 hour in 2% osmium tetroxide, and then were dehydrated in graded ethanol solutions and propylene oxide and embedded in epon. Ultrathin sections (60 nm) were cut on Leica Reycher Ultracut S, contrasted with uranyl acetate and lead citrate, and examined in OPTON 900 PC electron microscope. Gastroendocrine cells were identified and evaluated on the basis of secretory granules.