Summary. Until recently, little has been known about the morphological features of dying enterocytes at the villus tips of the human small intestine. The present study aimed to show the exfoliating processes of effete enterocytes at the villus tips. Cellular elements of the duodenal lumen and jejunal tissue in humans were fixed and processed for DNA nick end labeling (TUNEL), and transmission and scanning electron microscopy (TEM and SEM). Most cellular elements in the duodenal lumen were enterocytes having TUNEL-positive nuclei. By SEM, protruding enterocytes were discerned at the villus tips. Using the SEM samples embedded in epoxy resin, protruding enterocytes were observed at the villus tips by TEM; they were shrunk by forming numerous clear and autophagic vacuoles, took dome-like profiles, and possessed nuclei with chromatin condensation. The intercellular spaces beneath these protruding or effete enterocytes were often occupied by large lymphocytes. By TUNEL reaction, positive stainings appeared in the epithelium not only at the tip of the villi but also around the site. The results suggest that effete enterocytes at the villus tips of human small intertine are first shrunk by forming clear and autophagic vacuoles, and showed that their nuclei exhibit chromatin condensation immediately before being exfoliated into the lumen.It is generally believed that enterocytes (columnar epithelial cells) of mammalian guts are generated in crypts and move towards the villus tips, where they die by apoptosis, being exfoliated into the lumen (LEBLOND and MESSIER, 1958; MACDONALD et al., 1964; CHENG and LEBLOND, 1974; EASTWOOD, 1977; LEBLOND, 1981;WRIGHT and ALISON, 1984). According to the morphological criteria of apoptosis, dying cells show chromatin condensation and cell shrinkage, followed by heterophagocytosis (WYLLIE et al., 1980(WYLLIE et al., , 1984 KERR et al., 1987; CLARKE, 1990). Recently, GAVRIELI et al. (1992) have used in situ nick end labeling of dUTP mediated by terminal deoxytransferase (TUNEL reaction) to show that DNA fragmentation appears in epithelial cells of the rat and mouse small intestine and human large intestine at the villus tips. However, dying enterocytes with morphological features of apoptosis are hardly seen at the villus tips (KERB et al., 1987).In the small intestine of guinea pigs, IWANAGA et al. (1993) have shown that intraepithelial lymphocytes and subepithelial macrophages are involved in removing effete enterocytes at the tips of villi. They demonstrated that the body of the effete enterocytes was removed by those cells, whereas their thin superficial layer was retained to be later exfoliated without destroying the barrier; these cell fragments could be recognized in the fluid collected from the ileal lumen. Until recently, however, there have been neither morphological nor biochemical reports on the fate of effete enterocytes in the human small intestine at the tip of villi. To investigate this problem, the present study examined the dying processes of effete enterocytes ...

Nonsteroidal antiinflammatory drugs (NSAIDs) cause complications such as gastrointestinal injury. NSAIDs were recently reported to cause mitochondrial injury: to dissipate the mitochondrial transmembrane potential (MTP), and to induce mitochondrial permeability transition pore (PTP), which liberates cytochrome c. This enzyme generates reactive oxygen species (ROS) thereby triggers caspase cascade and cellular lipid peroxidation, resulting in cellular apoptosis. However, the mechanism of this NSAID-induced MTP's role in cellular apoptosis remains unknown. Rebamipide, an antiulcer drug, is reported to scavenge ROS and to show the protective effects on indomethacin-induced tissue peroxidations. Since cytochrome c and its generation of ROS are involved in indomethacin-induced cellular apoptosis, rebamipide may attenuate mitochondrial damage. The aim of this study was to elucidate whether indomethacin induces both the MTP decrease and cellular apoptosis, and the effect of rebamipide on these phenomena. We examined the effect of rebamipide on 1) MTP change, 2) lipid peroxidation, 3) apoptosis, and 4) caspase activation using gastric mucosal epithelial cell-line treated with indomethacin. With a specially designed fluorescence analyzing microscope system, MTP change, cellular lipid peroxidation, and cellular apoptosis were investigated with the small star, filled following fluorescent dyes, MitoRed, DPPP, and Hoechst 33,258, respectively. Indomethacin treatment decreased MTP but increased both cellular lipid peroxidation and cellular apoptosis via caspase 3 and 9 activation. Rebamipide clearly inhibited these phenomena {in vitro}. We demonstrated that fluorescent dyes such as MitoRed, DPPP, and Hoechst 33,258 are useful indicators for detecting oxidative cellular injuries in living cells. Rebamipide exerts a protective effect on mitochondrial membrane stability in gastric epithelial cells.

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N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) induces gastric cancer in animal models. We established an MNNG-induced mutant of the rat murine RGM-1 gastric epithelial cell line, which we named RGK-1, that could be used as an in vitro model of gastric cancer. This cell line showed signs of neoplasia and transformation, in that it lost contact inhibition and formed tumors in nude mice. The mutant cells also expressed parietal cell-specific H(+),K(+)-adenosine triphosphatase (H(+),K(+)-ATPase), which parent RGM-1 did not. The results suggested that parent RGM-1 cells were gastric progenitor cells. This mutant RGK-1 cell line will contribute to future investigation on gastric carcinogenesis and to the development of other pathophysiologic fields.