Regenerating gene protein may mediate gastric mucosal proliferation induced by hypergastrinemia in rats

BACKGROUND & AIMS

Regenerating gene (Reg) has been isolated from rat regenerating pancreatic islets, and Reg protein is mitogenic to islet cells. We have recently shown that Reg gene and Reg protein are expressed in gastric enterochromaffin-like (ECL) cells. This study aimed to clarify whether gastrin enhances Reg protein production in ECL cells and whether Reg protein is mitogenic to gastric mucosal cells.

METHODS

Reg gene expression in response to acute and chronic hypergastrinemia was investigated in rats. Immunohistochemical studies, Northern blotting, and in situ hybridization were performed to investigate the expression of Reg protein and Reg gene. The direct effect of gastrin on Reg gene expression was investigated using isolated ECL cells, and the trophic effect of Reg protein on cultured gastric epithelial cells was assessed by [3H]thymidine uptake.

RESULTS

Both chronic hypergastrinemia and short-term gastrin administration stimulated Reg gene expression and Reg protein production in fundic mucosa. Reg gene expression was also augmented in isolated ECL cells after incubation with rat gastrin. Reg protein was mitogenic to cultured rat gastric epithelial cells.

CONCLUSIONS

Gastrin stimulates the production of Reg protein in gastric ECL cells, which may be involved in the gastrin-induced gastric mucosal cell growth.

Lineage and clonal development of gastric glands

Individual gastric glands of the stomach are composed of cells of different phenotypes. These are derived from multipotent progenitor stem cells located at the isthmus region of the gland. Previous cell lineage analyses suggest that gastric glands, as in the colon and small intestine, are invariably monoclonal by adult stages. However, little is known about the ontogenetic progression of glandular clonality in the stomach. To examine this issue, we employed an in situ cell lineage marker in female mice heterozygous for an X-linked transgene. We found that stomach glands commence development as polyclonal units, but by adulthood (6 weeks), the majority progressed to monoclonal units. Our analysis suggests that at least three progenitor cells are required to initiate the development of individual gastric glands if they are analyzed just after birth. Hence, unlike the colon and small intestine, stomachs showed a significant fraction (10-25%) of polyclonal glands at adult stages. We suggest that these glands persist from polyclonal glands present in the embryonic stomach and hypothesize that they represent a subpopulation of glands with larger numbers of self-renewing stem cells.

Lectin-gold localization of fucose residues in human gastric mucosa

The oligosaccharides of the mucous gastric glycoproteins are involved in the protection of the gastric mucosa and are altered in different diseases. Therefore, it is important to know their composition in health, to better determine the alterations induced by the disease. Moreover, analysis of the molecular composition of the fundic gland cells has been previously used to obtain new insights into the origin of the different cell types. The aim of the present study was the localization in the subcellular structures of the fucose residues of the oligosaccharides in human fundic glands. For this, lectin cytochemical methods were used at the light and electron microscopic levels. They were combined with enzymatic and chemical treatments to characterize the nature of the oligosaccharide chains containing the fucose residues. The presence of this carbohydrate belonging to N- or O-linked oligosaccharides has been demonstrated in the secretory granules of the surface, gastric pit, mucous neck, and transitional cells of the fundic mucosa, and in the intracellular canaliculi and tubulovesicular system of the parietal cells. These fucose residues were added in the trans-Golgi regions to the elongating chains. Additional fucose linked to the innermmost N-acetylglucosamine of the N-linked oligosaccharides was found in the chief cells, being incorporated in the cis-Golgi. The findings in the transitional cells corroborate the origin of the chief cells from the mucous neck cells.

An immunologically distinct beta-adaptin on tubulovesicles of gastric oxyntic cells

Clathrin and the gamma-adaptin subunit of the AP-1 clathrin adaptor have been previously identified on H-K-ATPase-rich tubulovesicles from gastric acid secretory (oxyntic) cells [C. T. Okamoto, S. M. Karam, Y. Y. Jeng, J. G. Forte, and J. Goldenring. Am. J. Physiol. 274 (Cell Physiol. 43): C1017-C1029]. We further characterized this AP-1 adaptor from rabbit and hog tubulovesicles biochemically and immunologically. Clathrin coat proteins were stripped from purified tubulovesicular membranes and fractionated by hydroxyapatite chromatography. The AP-1 adaptor appears to elute at 200 mM sodium phosphate, based on the presence of proteins in this fraction that are immunoreactive with antibodies against three of the four subunits of this heterotetrameric complex: the gamma-, mu1-, and sigma1-adaptin subunits. Although the putative beta-adaptin subunit in this fraction is not immunoreactive with the anti-beta-adaptin monoclonal antibody (MAb), this beta-adaptin is immunoreactive with polyclonal antibodies (PAbs) directed against the peptide sequence Gly625-Asp-Leu-Leu-Gly-Asp-Leu-Leu-Asn-Leu-Asp-Leu-Gly-Pro-Pro- Val640 , a region conserved between beta1- and beta2-adaptins that is thought to be involved in the binding of clathrin heavy chain. Immunoprecipitation of the AP-1 adaptor complex from this fraction with anti-gamma-adaptin MAb 100/3 resulted in the coimmunoprecipitation of the beta-adaptin that did not react with the anti-beta-adaptin MAb but did react with the anti-beta-adaptin PAbs. In contrast, immunoprecipitation of the AP-1 adaptor complex from crude clathrin-coated vesicles from brain resulted in the coimmunoprecipitation of a beta-adaptin that was recognized by both the anti-beta-adaptin MAb and PAbs. These results suggest that the tubulovesicular AP-1 adaptor complex may be distinct from that found in the trans-Golgi network and may contain an immunologically distinct beta-adaptin. This immunologically distinct beta-adaptin may be diagnostic of apical tubulovesicular endosomes of epithelial cells.

Differential effects of protein kinase C inhibitors on fibronectin-induced interleukin-beta gene transcription, protein synthesis and secretion in human monocytic cells

Human monocytic cells express interleukin-1beta (IL-1beta) when stimulated with the extracellular matrix glycoprotein, fibronectin (FN). Protein kinase C (PKC) activation is considered important for this process; however, the metabolic steps at which PKC acts upon to mediate the FN-induced IL-1beta response remain unclear. We performed an analysis of the mechanisms by which two PKC inhibitors, Calphostin C and Staurosporine, prevent the FN-induced IL-1beta response. Both inhibitors blocked the secretion of IL-1beta protein into the media of peripheral blood mononuclear cells exposed to FN. Immunoprecipitation analysis revealed that under these circumstances, Calphostin C inhibited the production of IL-1beta protein, whereas Staurosporine allowed protein production, but inhibited its secretion. To determine the mechanisms responsible for these differences, we turned to human U937 promonocytic cells. U937 cells transfected with the human full-length IL-1beta promoter connected to a luciferase reporter gene were submitted to transcription assays, Northern blotting, and DNA electrophoresis mobility gel shift assays. These studies revealed that Calphostin C inhibited the nuclear translocation of the transcription factor activator protein-1 (AP-1) which is considered necessary for FN induction of IL-1beta gene transcription, and prevented the transcription of the IL-1beta gene. In contrast, Staurosporine alone induced AP-1 translocation and stimulation of the gene. Overall, our data indicate that Calphostin C prevents the transcription of the IL-1beta gene thereby inhibiting protein synthesis. Based on the high specificity of this compound for PKC, we conclude that PKC is necessary for FN-induced IL-1beta protein production. In contrast, Staurosporine prevented secretion of IL-1beta by unknown mechanisms.

Depolarization and cAMP elevation rapidly recruit TrkB to the plasma membrane of CNS neurons

Here, we describe a novel mechanism for the rapid regulation of surface levels of the neurotrophin receptor TrkB. Unlike nodose ganglion neurons, both retinal ganglion cells (RGCs) and spinal motor neurons (SMNs) in culture display only low levels of surface TrkB, though high levels are present intracellularly. Within minutes of depolarization or cAMP elevation, surface TrkB levels increase by nearly 4-fold, and this increase is not blocked by cycloheximide. These findings suggest that activity and cAMP elevation rapidly recruit TrkB to the plasma membrane by translocation from intracellular stores. We propose that a fundamental difference between peripheral nervous system (PNS) and central nervous system (CNS) neurons is the activity dependence of CNS neurons for responsiveness to their peptide trophic factors and that differences in membrane compartmentalization of the receptors underlie this difference.

Conditional lineage ablation to model human diseases

Cell loss contributes to the pathogenesis of many inherited and acquired human diseases. We have developed a system to conditionally ablate cells of any lineage and developmental stage in the mouse by regulated expression of the diphtheria toxin A (DTA) gene by using tetracycline-responsive promoters. As an example of this approach, we targeted expression of DTA to the hearts of adult mice to model structural abnormalities commonly observed in human cardiomyopathies. Induction of DTA expression resulted in cell loss, fibrosis, and chamber dilatation. As in many human cardiomyopathies, transgenic mice developed spontaneous arrhythmias in vivo, and programmed electrical stimulation of isolated-perfused transgenic hearts demonstrated a strikingly high incidence of spontaneous and inducible ventricular tachycardia. Affected mice showed marked perturbations of cardiac gap junction channel expression and localization, including a subset with disorganized epicardial activation patterns as revealed by optical action potential mapping. These studies provide important insights into mechanisms of arrhythmogenesis and suggest that conditional lineage ablation may have wide applicability for studies of disease pathogenesis.

Transforming growth factor-beta inhibits proliferation and maturation of cultured guinea pig gastric pit cells

We studied the effects of transforming growth factor-beta1 (TGF-beta1) on guinea pig gastric mucous cells, cultured in serum-free conditions. Electron microscopy showed that most cells were pre-pit cells, characterized by the presence of a few secretory granules scattered in the cytoplasm. Epidermal growth factor (EGF) stimulated cell growth, [3H]glucosamine uptake, and accumulation of mucus granules positive for galactose oxidase-Schiff reaction. This EGF-induced maturation into pit cells was confirmed morphologically by the appearance of uniformly dense ovoid or spherical mucus granules packed in the ectoplasm. Western blotting with an antiphosphotyrosine antibody showed that TGF-beta1 did not inhibit the EGF-initiated tyrosine phosphorylation of the EGF receptor. Northern blotting with cDNA probes for c-fos and c-myc demonstrated that TGF-beta1 did not affect the EGF-induced expression of the transcripts. However, TGF-beta1-treated cells did not replicate and remained in an immature stage, even in the presence of EGF, suggesting a potential role of TGF-beta1 in the regulation of proliferation and differentiation of a pit cell lineage in vivo.

Infection of sheep with adult and larval Ostertagia circumcincta: abomasal morphology

The infection of parasite-naive sheep with approximately 15,000 adult Ostertagia circumcincta via abomasal cannulae resulted in marked changes in the structure and function of the abomasum. The functional changes, which have been characterised previously, included elevated abomasal pH and increased serum concentrations of pepsinogen and gastrin. Eight days after the transplant of adult worms, the abomasa of recipient animals were significantly heavier than those of controls (P < 0.001), the thickness of the fundic mucosa was greater (P < 0.01), there were fewer parietal cells (P < 0.01) and increases in the numbers of mitotic figures and mucus-producing cells. Mucous cell hyperplasia was also evident in the fundic mucosae of sheep receiving a trickle infection of infective, third-stage O. circumcincta larvae and was prominent within nodules associated with larval development. In non-nodular mucosa, there was hyperplasia of mucous cells and changes in the distribution of parietal cells. Decreases in the number of parietal cells at the gland base were offset by increases at a mid-gland level, probably due to chronic hypergastrinaemia, so that, overall, total parietal cell number was unaffected. Mucous cell hyperplasia and the diminution of parietal cell number are seen in a diverse range of disease states and may be mediated by host growth factors such as Transforming growth factor-alpha. Alternatively, the cellular and/or the secretory changes in response to the presence of adult worms are mediated by chemicals that are cytotoxic/inhibitory for parietal cells, and released by the parasites themselves.

Water immersion-restraint stress induces expression of immediate-early genes in gastrointestinal tract of rats

The aims of this study were to determine 1) which cells are involved in stress-induced acute gastric mucosal lesion and 2) what kinds of molecular alterations are induced by stress, using immediate-early genes (IEG) as tools for detection of cellular activation. Male Wistar rats were exposed to acute water immersion-restraint stress. Protein and mRNA for IEG were detected by immunohistochemistry and in situ hybridization, respectively. This stress induced the expression of c-fos and nerve growth factor-induced gene (NGFI-A) mRNA in gastric epithelial cells, the smooth muscle layer of small blood vessels, and the stomach wall. Stress upregulated the mRNA levels of these IEG in the duodenal epithelial cells and induced de novo expression of IEG in the smooth muscle layer of small blood vessels and the duodenal wall. These findings indicate that these cells are activated in response to stress. Expression of these IEG and/or transcriptional factors may reflect an initiation of mechanisms for repairing the lesions induced by stress as well as an adaptation to the stress.

Comparison of the signal transduction pathways activated by gastrin in enterochromaffin-like and parietal cells

BACKGROUND & AIMS

Gastrin stimulates acid secretion from parietal cells and histamine release from enterochromaffin-like (ECL) cells through identical gastrin receptors. However, gastrin has been shown to have a trophic effect only on ECL cells. The aim of this study was to compare gastrin-induced signal transduction pathways in the ECL and parietal cells of Mastomys natalensis, an African rodent.

METHODS

Both ECL and parietal cells were isolated from the gastric mucosa of M. natalensis, and intracellular signal transduction events in response to gastrin were investigated.

RESULTS

Gastrin elicited histamine release from ECL cells and acid secretion from parietal cells in association with enhanced inositol phospholipid turnover. Although gastrin increased [3H]thymidine incorporation into ECL cells, it had no effect on parietal cells. Moreover, tyrosine phosphorylation and activation of mitogen-activated protein (MAP) kinase as well as c-fos and c-jun gene expression were augmented only in ECL cells. In addition, gastrin increased the formation of guanosine triphosphate-Ras with a simultaneous decrease in guanosine diphosphate-Ras levels in ECL but not in parietal cells.

CONCLUSIONS

Although gastrin receptors are present in both ECL and parietal cells, they activate the Ras-MAP kinase pathway only in ECL cells.

Rab11a redistributes to apical secretory canaliculus during stimulation of gastric parietal cells

Previous investigations in several systems have demonstrated that Rab3 family members redistribute to soluble fractions on fusion of secretory granules with target plasma membranes. Rab proteins are then recycled back onto mature secretory vesicles after reinternalization of the membrane. Although this cycle is well established for Rab3, far less is known about redistribution of other Rab proteins during vesicle fusion and recycling. In the gastric parietal cell, Rab11a is associated with H-K-ATPase-containing tubulovesicles, which fuse with the apical plasma membrane (secretory canaliculus) in response to agonists such as histamine. We have analyzed distribution of Rab11a and other tubulovesicle proteins in resting and histamine-stimulated rabbit parietal cells. Stimulation of isolated gastric glands in the presence of 100 microM histamine and 100 microM 3-isobutyl-1-methylxanthine did not cause a significant increase in soluble Rab11a. H-K-ATPase, Rab11a, Rab25, syntaxin 3, and SCAMPs increased immunoreactivity in stimulus-associated vesicles prepared from rabbits treated with histamine compared with those from ranitidine-treated animals. The large GTPase dynamin was found in both vesicle preparations, but there was no change in amount of immunoreactivity. Immunofluorescence staining of resting and histamine-stimulated primary cultures of parietal cells demonstrated redistribution of H-K-ATPase and Rab11a to F-actin-rich canalicular membranes. Dynamin was present on canalicular membranes in resting and stimulated cells. These results indicate that Rab11a does not cycle off the membrane during the process of tubulovesicle fusion with the secretory canaliculus. Thus Rab11a may remain associated with recycling apical membrane vesicle populations.

Localization and significance of pp55, a gastric mucosal membrane protein with tyrosine kinase activity

In Fischer 344 rats, induction of gastric mucosal proliferative activity, whether the result of aging or injury or occurring after administration of epidermal growth factor, gastrin, or bombesin, is associated with a rise in tyrosine kinase activity and tyrosine phosphorylation of several mucosal proteins, including a protein with a molecular mass of 53-55 kDa. We hypothesized that this phosphotyrosine membrane protein (referred to as pp55) may play a role in regulating gastric mucosal cell proliferation and differentiation. Purification and subsequent immunoprecipitation studies now show that pp55 is a tyrosine kinase. In addition, the enzyme activity in the gastric mucosa is found to be fourfold higher in aged rats than in young rats. Incubation of gastric mucosal membranes with transforming growth factor-alpha (2 x 10(-8) M) stimulates tyrosine kinase activity of pp55. Immunolocalization studies reveal that pp55 immunoreactivity is predominantly present in mucous cells that are located just above the proliferative zone and spasmolytic peptide-immunoreactive mucous neck cells. Tyrosine kinase activity as well as expression of pp55 are also greatly increased in the gastric mucosa after hypertonic saline-induced injury, a condition that results in stimulation of surface mucosal cell proliferation and differentiation. Our current data suggest that pp55 is a tyrosine kinase, likely localized to pre-surface cells. The presence of pp55 in pre-surface mucous cells and the expression and tyrosine kinase activity of this protein, which can be stimulated during mucosal cell proliferation and differentiation, strongly suggest a role for pp55 in differentiation of gastric surface mucous cells.

Reversal of myogenic terminal differentiation by SV40 large T antigen results in mitosis and apoptosis

Terminally differentiated skeletal muscle myotubes are arrested in the G0 phase of the cell cycle, and this arrest is not reversed by stimulation with serum or growth factors. The myotubes have been shown to be refractory to apoptosis even under low serum conditions. When the SV40 large T antigen is induced in the C2SVTts11 myotubes, which stably harbor the T antigen gene linked to an inducible promoter, the terminally differentiated cells reenter the cell cycle to resume nuclear DNA replication representing S phase. We show here that the large T-expressing myotubes further proceeded to M phase represented by the appearance of mitotic figures with centrosomes, condensed chromosomes, and mitotic spindles. The myotubes eventually cleaved and midbodies were formed at the cleavage sites of the cytoplasm. In some cases actin filaments, reminiscent of the contractile rings, accumulated at the cleavage furrows. Thus, terminally differentiated myotubes remain able to resume at least one round of the cell cycle and consequently are considered to be capable of dedifferentiation. A subset of myotubes expressing large T did not undergo mitosis. Some of them were degenerative and contained deformed giant nuclei and pulverized nuclei. The others suffered apoptotic cell death, which was identified by morphological changes of the nuclei and the labeling with dUTP at the ends of chromatin DNA fragments. The induction of apoptosis was unlikely to be confined to a particular phase of the cell cycle. These results imply that terminally differentiated myotubes also retain a complete set of machinery for apoptosis.

Mice lacking secretory phospholipase A2 show altered apoptosis and differentiation with Helicobacter felis infection

BACKGROUND & AIMS

Infection with Helicobacter pylori uniformly leads to a chronic superficial gastritis that may progress to atrophic gastritis, a premalignant process. A mouse model of Helicobacter felis infection was used to study possible genetic determinants of the response to infection.

METHODS

Three inbred mouse strains with known secretory phospholipase A2 (sPLA2) genotypes [BALB/c (+/+), C3H/HeJ (+/+), and C57BL/6 (-/-)] were orally infected with H. felis and examined longitudinally using routine histology, immunocytochemistry, electron microscopy, proliferating cell nuclear antigen, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling, and Northern and Western blot studies.

RESULTS

Only the C57BL/6 strain showed increased gastric fundic proliferation and apoptosis in response to infection. In addition, the C57BL/6 mouse showed a marked loss of parietal and chief cells, along with a marked expansion of an aberrant gastric mucous cell lineage that stained positive for spasmolytic polypeptide. In contrast, no significant change in these cell types was observed in BALB/c and C3H/HeJ strains. Increased expression of sPLA2 was observed in BALB/c and C3H/HeJ after H. felis infection, whereas sPLA2 expression was absent in C57BL/6 mice.

CONCLUSIONS

H. felis infection leads to increased apoptosis and altered cellular differentiation in the C57BL/6 mouse, a strain that lacks gastric sPLA2 expression. Because sPLA2 has been identified recently as the MOM1 (modifier of MIN) locus that influences polyp formation in the colon, these studies suggest that sPLA2 may also influence the gastric epithelial response to Helicobacter infection.

Epithelial attachment alters the outcome of Helicobacter pylori infection

Genetically defined in vivo models are needed to assess the importance of target cell attachment in bacterial pathogenesis. Gastric colonization by Helicobacter pylori in human populations is common and persistent, and has various outcomes including peptic ulcers and cancer. The impact of attachment on the course of infection was examined in transgenic mice expressing a human receptor for H. pylori in their gastric epithelium. Persistent infection by a clinical isolate occurred at comparable microbial densities in transgenic and nontransgenic littermates. However, microbial attachment in transgenic mice resulted in production of autoantibodies to Lewisx carbohydrate epitopes shared by bacteria and acid-secreting parietal cells, chronic gastritis, and parietal cell loss. This model should help identify bacterial and host genes that produce attachment-related pathology.

Targeted disruption of the murine Na+/H+ exchanger isoform 2 gene causes reduced viability of gastric parietal cells and loss of net acid secretion

Multiple isoforms of the Na+/H+ exchanger (NHE) are expressed at high levels in gastric epithelium, but the physiological role of individual isoforms is unclear. To study the function of NHE2, which is expressed in mucous, zymogenic, and parietal cells, we prepared mice with a null mutation in the NHE2 gene. Homozygous null mutants exhibit no overt disease phenotype, but the cellular composition of the oxyntic mucosa of the gastric corpus is altered, with parietal and zymogenic cells reduced markedly in number. Net acid secretion in null mutants is reduced slightly relative to wild-type levels just before weaning and is abolished in adult animals. Although mature parietal cells are observed, and appear morphologically to be engaged in active acid secretion, many of the parietal cells are in various stages of degeneration. These results indicate that NHE2 is not required for acid secretion by the parietal cell, but is essential for its long-term viability. This suggests that the unique sensitivity of NHE2 to inhibition by extracellular H+, which would allow upregulation of its activity by the increased interstitial alkalinity that accompanies acid secretion, might enable this isoform to play a specialized role in maintaining the long-term viability of the parietal cell.

Impaired gastric acid secretion in gastrin-deficient mice

To further understand the role of the peptide hormone gastrin in the development and function of the stomach, we have generated gastrin-deficient mice by gene targeting in embryonic stem cells. Mutant mice were viable and fertile, without obvious visible abnormalities. However, gastric function was severely affected by the loss of gastrin. Basal gastric acid secretion was abolished and could not be induced by histamine, carbachol, or gastrin. Histological analysis revealed alterations in the two cell types primarily involved in acid secretion, parietal and enterochromaffin-like (ECL) cells. Parietal cells were reduced in number with an accumulation of immature cells lacking H(+)-K(+)-adenosinetriphosphatase (H(+)-K(+)-ATPase). ECL cells were positioned closer to the base of the gastric glands, with markedly lower expression of histidine decarboxylase. Gastrin administration for 6 days reversed the effects of the gastrin deficiency, leading to an increase in the number of mature, H(+)-K(+)-ATPase-positive parietal cells and a partial restoration of acid secretion. The results show that gastrin is critically important for the function of the acid secretory system.

Experimental studies on the stem cell concept of liver regeneration. I

There are increasing references for the existence of a hepatic stem or progenitor cell system as well as its participation in the physiological as well as reparative regeneration of the liver and in carcinogenesis. For the physiological regeneration the existence of a dynamic "cell-renewal" system finds increasing consideration and in the "streaming liver concept" (Zajicek et al. 1985) its functional expression. This concept is still under discussion. The present paper tries to check this animal-experimentally (Wistar rats) under use of two different thymidine analogues (3H-thymidine and Bromodeoxyuridine). In different time intervals after labelling (1 h, 14, 30, 60, 90, 120 d) a shift of the labelling bias or a migration of the hepatocytes in the liver acinus (Rapaport) in portovenous direction could be shown. The average migration speed is 0.575 microm or 0.0315 cell positions per day, the cell production rate is one in 31.5 days. The present paper results support the inclusion of a stem or progenitor cell system into the physiological regeneration of the liver and allow the classification into the "streaming liver concept" (Zajicek et al. 1985).

Induction of precocious pepsinogen synthesis by glucocorticoids in fetal rat gastric epithelium in organ culture: importance of mesenchyme for epithelial differentiation

Glucocorticoids significantly affect both proliferation and differentiation of gastric epithelial cells in vivo. Here we examined the mechanism of action of glucocorticoids on the cells in vitro, with special reference to the epithelial-mesenchymal interaction. When 16.5-day fetal rat gastric explants were maintained in organ culture, the epithelial cells began to invaginate into mesenchyme on days 3 to 4, and formed glandular structures on days 5 to 6 in culture. Immunohistochemical analysis with specific antibodies revealed that pepsinogen-synthesizing cells first appeared on day 2, and they increased in number with epithelial morphogenesis to about 20%-30% of total epithelial cells on days 4 to 6, and that these cells were localized at the base of glandular structures in control media. When the explants were treated with hydrocortisone (1 microgram/ml), epithelial morphogenesis was mostly suppressed, but epithelial cytodifferentiation was significantly stimulated, indicating that epithelial morphogenesis is not necessary for their cytodifferentiation. In glucocorticoid-treated explants, pepsinogen-synthesizing cells first appeared on day 1, and more than 90% of the cells were positively stained with the antibodies from days 3 to 5 in culture. Biochemical analysis showed that much higher acid protease activity could be detected in glucocorticoid-treated explants than in controls from days 2 to 6 in culture, and analysis by zymography indicated that the synthesis of pepsinogen 1 but not cathepsin E was stimulated by the hormone. Northern blotting analysis showed that the level of pepsinogen 1 mRNA was greatly increased by glucocorticoids. Examination of the effect of the hormone on the epithelial proliferation showed that hydrocortisone (1 microgram/ml) significantly inhibited the epithelial growth from days 1 to 3 in culture. To investigate the role of epithelial-mesenchymal interaction in the glucocorticoid-induced differentiation of the gastric epithelial cells, effects of the hormone on the proliferation and differentiation of the cells in the absence of mesenchyme were examined, using a recently established primary culture system. The epithelial cells synthesized cathepsin E but not pepsinogen in cell culture, irrespective of glucocorticoid treatment, and the level of acid protease activity was not affected by the hormone, indicating that mesenchyme is necessary for the hormone to induce pepsinogen gene expression in the epithelial cells. In the cell culture system, glucocorticoids did not inhibit but significantly stimulated epithelial proliferation. This suggests that the hormone indirectly inhibited epithelial proliferation in organ culture, probably via mesenchyme. The mechanism of action of glucocorticoids on the epithelial-mesenchymal interaction in the fetal glandular stomach is discussed.

Induction of apoptosis of lymphocytes in rat mucosal immune system

AIM: To undergo apoptosis during negative and positive selection processes in rat mucosal immune system which are implicated in the pathogenesis of various mucosal diseases.

METHODS: Female Sprague-Dawley rats were given protein synthesis inhibitor, cycloheximide, intravenously or intraperitoneally, an apoptosis was recognized by morphological hallmark under light and electronmicroscopy, and the expression of proliferating cell nuclear antigen was visualized immunohistochemically.

RESULTS: The apoptosis of mucosal lymphocytes in the digestive tract, as well as in trachea, uterus and lacrimal gland was induced by cycloheximide ( > 1.0 mg·kg^-1 body weight), which were located mainly in lamina propria and germinal centers of lymphoid nodules. At the same time, a portion of crypt epithelial cells of proliferating zone in small and large intestine, and the epithelial cells in genital tract were also found to undergo apoptosis. Immunostainings showed that apoptotic cells expressed proliferating cell nuclear antigen.

CONCLUSION: Apoptosis of lymphocytes in mucosal immune system can be induced by cycloheximide. This model will facilitate the understanding of normal mucosal immune system and its role in the pathogenesis of related diseases such as inflammatory bowel diseases.

Cell lineage relationship in the stomach of normal and genetically manipulated mice

The oxyntic mucosa of the mouse stomach is lined with a heterogeneous population of cells that form numerous short pits continuous with long tubular glands. Tritiated thymidine radioautography has made it possible to pinpoint the origin of all cell types and to follow the differentiation/migration of different cell lineages along the pit-gland unit. The proliferating multipotent stem cells functionally anchored in the upper glandular region, the isthmus, give rise to three main lineage precursors: 1) pre-pit cells, which migrate upward to the pit while differentiating into mucus-producing pit cells; 2) pre-neck cells, which migrate downward to the glandular neck while differentiating into mucus-producing neck cells that, by approaching the glandular base, gradually change their phenotype into pepsinogen- and intrinsic factor-producing zymogenic cells; 3) pre-parietal cells, which differentiate into acid-producing parietal cells in the isthmus and then undergo bipolar migration towards the pit and the glandular base. Thus, parietal cells are the only cells that complete their differentiation in the isthmus and then migrate to be scattered throughout the pit-gland unit. To determine whether parietal cells play a role in controlling decisions about cell fate within the pit-gland unit, the gastric epithelium has been examined in transgenic mice expressing the H,K-ATPase beta-subunit-1035 to +24/simian virus 40 large T antigen fusion gene. The blockade in parietal cell differentiation in these mice produces an amplification of lineage precursors, a marked depletion of zymogenic cells and an increase in pit cell census. Ablation of parietal cells in another transgenic mouse model expressing the H,K-ATPase beta-subunit-1035 to +24/diphtheria toxin fragment A fusion gene also produces amplification of lineage precursors, and similar effects on zymogenic and pit cell census. These findings strongly suggest that parietal cells produce regulatory signals that control the cellular differentiation program of both pit and zymogenic cell lineages, and would hopefully improve our ability to identify the cellular pathways leading to malignant transformation.

Nucleotide metabolism by gastric glands and H(+)-K(+)-ATPase-enriched membranes

alpha-Toxin-permeabilized gastric glands represent a functional model in which acid secretion can be elicited by either adenosine 3',5'-cyclic monophosphate (cAMP) or ATP, with proven morphological and functional transition between resting and secretory states [X. Yao, S. M. Karam, M. Ramilo, Q. Rong, A. Thibodeau, and J. G. Forte. Am. J. Physiol. 271 (Cell Physiol. 40): C61-C73, 1996.] In this study we use alpha-toxin-permeabilized rabbit gastric glands to study energy metabolism and the interplay between nucleotides to support acid secretion, as indicated by the accumulation of aminopyrine (AP). When permeabilized glands were treated with a phosphodiesterase inhibitor, the secretory response to cAMP was inhibited, whereas the secretory response to ATP was potentiated. This implied that 1) ATP provided support not only as an energy source but also as substrate for adenylate cyclase, 2) activation of acid secretion by cAMP needed ATP, and 3) ATP and cAMP exchanged rapidly inside parietal cells. To address these issues, we tested the action of adenine nucleotides in the presence and absence of oxidizable substrates. All adenine nucleotides, including AMP, ADP, ATP, and cAMP, could individually enhance the glandular AP accumulation in the presence of substrates, whereas only a high concentration of ATP (5 mM) was able to support secretory activity in substrate-free buffer. Moreover, ATP could maintain 75-80% of maximal secretory activity in phosphate-free buffer; cAMP alone could not support secretion in phosphate-free buffer. In glands and in H(+)-K(+)-adenosinetriphosphatase-rich gastric microsomes, we showed the operation of adenylate kinase, creatine kinase, and ATP/ADP exchange activities. These enzymes, together with endogenous adenylate cyclase and phosphodiesterase, provide the recycling of nucleotides essential for the viability of alpha-toxin-permeabilized gastric glands and imply the importance of nucleotide recycling for energy metabolism in intact parietal cells.

Expression of intrinsic factor and pepsinogen in the rat stomach identifies a subset of parietal cells

Morphological and functional heterogeneity of parietal cells has been thought to be due to different maturation positions within the gastric gland. Morphodynamic studies have shown that 2% of parietal cells in mice derive from a pre-neck (chief) cell precursor. Intrinsic factor (IF) and pepsinogen, markers of rat chief cells, were used to determine if these proteins identified a subset of parietal cells that might reflect origin from the pre-neck cell lineage. The zymogenic region of the rat stomach and gradient-isolated fractions enriched in parietal and chief cells were fixed in 10% buffered Formalin or in Bouin's solution. Immunostaining was performed using indirect immunoperoxidase histochemistry and double-labeled immunofluorescence with antibodies raised against human IF, pepsinogen II, and H(+)-K(+)-adenosinetriphosphatase (H(+)-K(+)-ATPase). In intact tissue, parietal (H(+)-K(+)-ATPase-positive) cells were found starting at the upper edge of the isthmus, but parietal cells positive for IF and pepsinogen were only found from just below the isthmus and neck region to the base of the gastric gland. Three to four percent of isolated parietal cells were positive for these ectopic markers. This subset of cells was also positive for H(+)-K(+)-ATPase. Thus products of rat chief cells are expressed in a subset of parietal cells. The percentage of positive cells is similar to that predicted to be derived from the pre-neck (chief) precursor lineage in the mouse. The distribution of these cells to the lower neck and base of the gland suggests that the expression of chief cell products is consistent with either predetermination by lineage or parietal cell maturation or with both processes.

State of actin in gastric parietal cells

Remodeling of the apical membrane-cytoskeleton has been suggested to occur when gastric parietal cells are stimulated to secrete HCl. The present experiments assayed the relative amounts of F-actin and G-actin in gastric glands and parietal cells, as well as the changes in the state of actin on stimulation. Glands and cells were treated with a Nonidet P-40 extraction buffer for separation into detergent-soluble (supernatant) and detergent-insoluble (pellet) pools. Two actin assays were used to quantitate actin the deoxyribonuclease I binding assay to measure G-actin and F-actin content in the two pools and a simple Western blot assay to quantitate the relative amount of actin in the pools. Functional secretory responsiveness was assayed by aminopyrine accumulation. About 5% of the total parietal cell protein is actin, with about 90% of the actin present as F-actin. Stimulation of acid secretion resulted in no measurable change in the relative amounts of G-actin and cytoskeletal F-actin. Treatment of gastric glands with cytochalasin D inhibited acid secretion and resulted in a decrease in F-actin and an increase in G-actin. No inhibition of parietal cell secretion was observed when phalloidin was used to stabilize actin filaments. These data are consistent with the hypothesis that microfilamentous actin is essential for membrane recruitment underlying parietal cell secretion. Although the experiments do not eliminate the importance of rapid exchange between G- and F-actin for the secretory process, the parietal cell maintains actin in a highly polymerized state, and no measurable changes in the steady-state ratio of G-actin to F-actin are associated with stimulation to secrete acid.

Proliferation, differentiation and morphogenesis of fetal rat glandular stomach transplanted under the kidney capsule of syngeneic hosts

Undifferentiated glandular stomach tissue fragments from 16.5-day fetal rats were transplanted under the kidney capsule of syngeneic adult rats, and the proliferation, differentiation and morphogenesis of the transplanted tissues were investigated. Gastric epithelial cells began to invaginate 3-4 days after the transplantation and immature glands were formed after 1 week. During the period, there was a gradual increase in the expression of pepsinogen and cathepsin E, markers of cytodifferentiation of the stomach epithelia, both at protein and mRNA levels. Cathepsin E was weakly expressed in undifferentiated gastric epithelial cells at 16.5 days of gestation, and a higher level of the expression was observed in differentiated epithelia of the transplants. In contrast, the pepsinogen-producing cells first appeared around days 3-4 after transplantation and gradually increased in number to about 30% of the epithelial cells and became localized at the bottom of the gland. During the period of the experiment up to 1 month, the pepsinogen-producing cells were all positive for class III mucin and cathepsin E, indicating the immature character of these cells. In addition, no parietal cells were observed. When the tissue fragments were transplanted into adrenalectomized animals, the epithelial differentiation and morphogenesis was suppressed, but its proliferation was enhanced. The observed changes were reversed by hydrocortisone replacement. These results suggest that the development of the 16.5-day fetal stomach is regulated intrinsically to a certain extent by the genetic program of the cells involved and various gastric functions develop in the absence of luminal stimulation, stage-specific systemic hormonal change, neuronal regulation or other systemic influences, and that glucocorticoids modulate the developmental program of the fetal stomach tissues.

Examining the role of Paneth cells in the small intestine by lineage ablation in transgenic mice

The Paneth cell lineage is one of four epithelial lineages derived from the adult mouse small intestine's multipotent stem cell. Mature Paneth cells secrete antimicrobial peptides (cryptdins), growth factors, as well as two gene products, a secreted phospholipase A2 and matrilysin, that has been implicated as modifiers of adenoma formation in mice containing a mutation in the tumor suppressor Apc. Immature Paneth cells are located just above and below the cell layer, in intestinal crypts, that has been proposed to contain the multipotent stem cell. Paneth cells differentiate during a downward migration to the crypt base. The location and direction of Paneth cell migration, their high density and long residency time at the crypt base, and the nature of their secreted gene products, suggest that they may influence the structure and/or function of the stem cell niche. Paneth cell ablation can therefore be viewed as an experimental manipulation of the cellular microenvironment that purportedly contains the stem cell and its immediate descendants. Two types of ablation experiments were performed in transgenic mice. Nucleotides -6500 to +34 of the mouse cryptdin-2 gene (CR2) were used to express an attenuated diphtheria toxin A fragment. Light and electron microscopic immunohistochemical analyses of several pedigrees of postnatal day 28 to 180 animals established that ablation of Paneth cells is accompanied by an increase in the proportion of undifferentiated crypt base columnar cells. These cells normally co-exist with Paneth cells. The ablation does not produce a detectable effect on the proliferation or terminal differentiation programs of the other three lineages or on host-microbial interactions. The last conclusion is based on the ability of crypts to remain free of microbes detectable by Gram and Warthin-Starry stains and by retention of the normal crypt-villus distribution of components of the diffuse gut-associated lymphoid tissue. CR2-directed expression of simian virus 40 large T antigen also results in a loss of mature Paneth cells but produces a marked amplification of crypt cells having a morphology intermediate between Paneth and granule goblet cells. EM immunohistochemical analyses suggest that intermediate cells can differentiate to mature goblet cells but not to Paneth cells, as they migrate up the crypt-villus axis. Our findings suggest that (i) stemness in the crypt is not defined by instructive interactions involving the Paneth cell; (ii) expressing a Paneth cell fate may require that precursors migrate to the crypt base; (iii) antimicrobial factors produced by Paneth cells are not required to prevent colonization of small intestinal crypts; and (iv) this lineage does not function to maintain the asymmetric crypt-villus distribution of components of the diffuse gut-associated lymphoid tissue.

Role of gastrin/CCK-B receptor in the regulation of gastric acid secretion in rat

The aim of this study was to investigate whether gastrin regulates morphological changes and alpha-subunit gene expression in parietal cells through the gastrin/CCK-B receptor on enterochromaffin-like cells by histamine release. Treatment with 100 mg/kg of YM022, a potent and selective gastrin/CCK-B receptor antagonist, for one week in rats did not alter mRNA levels of histidine decarboxylase or H+, K+-ATPase. However, parietal cell morphology predominantly changed to the resting form, although the serum gastrin concentration was significantly increased. Additional treatment with YM022 and oral omeprazole, 100 mg/kg, for one week markedly suppressed the increases of mRNA levels of histidine decarboxylase and H+, K+-ATPase and completely blocked the morphological transformation of the parietal cells to a stimulated form induced by treatment with omeprazole alone. This indicates that the morphological transformation of parietal cells to an activated form with a subsequent increase in H+, K+-ATPase synthesis caused by hypergastrinemia is mediated by increased histidine decarboxylase gene expression in enterochromaffin-like cells via gastrin/CCK-B receptors.

Ultrastructure of the zymogenic-cell lineage in abomasal mucosa of adult cattle

The ultrastructural differentiation and maturation of the neck cells and the zymogenic cells during physiological cell renewal were investigated in the abomasal oxyntic-gland region of cattle. Immature neck cells of the distal isthmus and proximal neck exhibit transitional morphology to the predominantly mucous isthmus cells. Neck cells confined to the glandular neck are characterized by bipartite peptic-cored mucous secretory granules. In a proximal-distal gradient along the neck, a progressive increase in the peptic granular component and concomitant reduction in mucous components paralleled by proliferation of the rough endoplasmic reticulum creates pre-zymogenic cells in the proximal glandular base. These, in turn, give rise to mature zymogenic cells with pure peptic secretory granules and typical zymogenic cell morphology. In the depth of the gland, older degenerative zymogenic cells are found. Variations in size and number of the zymogenic granules point to different secretory activities of the mature zymogenic-cell population of the glandular base. These results favour the conception of a zymogenic-cell lineage arising within the isthmus and passing through different developmental stages, including neck cells, during their migration down the gland.

Effect of enprostil on omeprazole-induced hypergastrinemia and inhibition of gastric acid secretion in peptic ulcer patients

This study was performed to examine the effects of additional enprostil administration on hypergastrinemia and gastric acid suppression induced by omeprazole. Serum gastrin concentrations were measured in 10 peptic ulcer patients (six Helicobacter pylori-positive and four Helicobacter pylori-negative patients) before treatment, after two weeks of omeprazole (20 mg/day), and after two weeks of omeprazole and enprostil (50 micrograms/day). The additional acid inhibitory effect of enprostil was evaluated by 24-hr intragastric pH measurements in five healthy Helicobacter pylori-negative volunteers. After omeprazole treatment, the serum gastrin level of Helicobacter pylori-positive patients (3.5-fold of control) was markedly higher than that of Helicobacter pylori-negative patients (1.7-fold of control). Additional treatment with enprostil suppressed serum gastrin levels to 0.4-fold and 0.7-fold of omeprazole treatment levels in Helicobacter pylori-positive and Helicobacter pylori-negative patients, respectively. In healthy volunteers, median pH recorded during the nonmeal daytime interval increased significantly with additional enprostil. Thus, enprostil reduces undesirable omeprazole-induced hypergastrinemia, especially in Helicobacter pylori-positive patients, and effectively suppresses acid secretion.

A novel group of pumilio mutations affects the asymmetric division of germline stem cells in the Drosophila ovary

Germline stem cells play a pivotal role in gametogenesis; yet little is known about how they are formed, how they divide to self-renew, and how these processes are genetically controlled. Here we describe the self-renewing asymmetric division of germline stem cells in the Drosophila ovarian germline, as marked by the spectrosome, a cytoplasmic structure rich in membrane skeletal proteins. The ontogeny of the spectrosome marks the lineage of germline stem cells. We identified two new groups of mutations in which the divisional asymmetry is disrupted. The first, which we refer to as ovarette (ovt) mutations, was shown to correspond to a novel class of mutations in the pumilio locus. Since pumilio is known to posttranscriptionally repress the expression of target genes at earlier stages of germ cell development, our results suggest that a similar activity is needed to maintain germ line stem cells. We have also identified a second and novel gene, piwi, whose mutations abolish germline stem cell division.

Proprotein-processing endoprotease furin controls the growth and differentiation of gastric surface mucous cells

Gastric surface mucous cells originate from progenitor cells at the isthmus of the gastric gland, from where the cells migrate to the luminal surface. With migration they form secretory granules and express TGF alpha. We found that proprotein-processing endoprotease furin-positive cells were layered around the upper one fourth of the gastric glands of adult rats, whereas they were distributed along an outer epithelial layer in fetal rats. Because the furin-positive cell layer was localized from the upper cell proliferating zone to the less proliferating pit-cell region in the gastric gland unit, we examined the role of furin in the growth and differentiation of surface mucous cells by using the cell line, GSM06. This cell line is derived from the gastric surface mucous cells of transgenic mice harboring the temperature-sensitive simian virus 40 T antigen. At T antigen-active temperature (33 degrees C), the cells grew to confluency, whereas at T antigen-inactive temperature (39 degrees C), the cells ceased growing. At 33 degrees C, the cells exhibited a high level of furin expression with a negligible level of periodic acid Schiff (PAS)-positive materials and a low level of TGF alpha. In contrast, at 39 degrees C the cells produced a high level of PAS-positive materials, TGF alpha, and secretory granules, with a negligible level of furin expression. To further examine the role of furin, we established a GSM06 cell line introduced with either a sense or an antisense furin cDNA. The cells with sense furin expression produced fewer PAS-positive materials and a low level of TGF alpha even at 39 degrees C, whereas the cells with antisense furin expression exhibited more PAS-positive materials and TGF alpha even at 33 degrees C. When furin expression was suppressed by its antisense oligonucleotide, the cell growth was retarded with enhanced expression of the differentiated characteristics. Thus, we conclude that furin is instrumental in controlling the growth of the surface mucous cells.

Course of apoptotic changes in the rat gastric mucosa caused by oral administration of fusarenon-X

Male 5-week-old Wistar rats orally (po) administered with fusarenon-X (FX) 1.5 mg/kg and control rats po-treated with distilled water were sacrificed at 0-48 hr after gavage. FX-administered rats showed significant dilatation of the stomach with increased fluid contents at 1-24 hr postadministration (PA). Histopathologically, karyopyknosis of chief cells in the basal region of the gastric glands began to appear at 1 hr, and nuclear fragments were seen in the neck cell region at 1.5 hr PA. At 2-4 hr PA, apoptotic cells appeared diffusely in the neck region and focally in the basal region. Electron microscopy revealed that cells phagocytosing apoptotic bodies were the surface epithelia, undifferentiated neck cells, parietal cells and chief cells. No evidence was detected to show that parietal cells underwent apoptotic changes. The apoptotic lesions peaked at 4-6 hr PA, gradually subsided at 12 hr PA, and became minimal leaving apoptotic remnants in the basal region at 24 hr PA. At 48 hr PA, however, diffuse apoptotic lesions reappeared in the basal region at a level similar to that at 2-3 hr PA. This might be attributable to absorption of FX retaining in the stomach for 24 hr. In situ detection of DNA breaks by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) reaction was consistent with the histopathologic findings. Agarose gel electrophoresis of DNA fragments isolated from the gastric mucosae of FX-administered rats showed a ladder pattern after 1.5 hr PA and the pattern became more distinct at 2-4 hr PA.

Proliferation and differentiation of cells from explants of fetal rat stomach

The current understanding of the mechanisms controlling the proliferation and differentiation of the stem cells of the gastric oxyntic glands is limited. The aim of the present study was to develop a method for investigating proliferation and differentiation of undifferentiated cells from fetal rat stomach. Outgrowth of cells was initiated from explants of 16-day-old fetal rat stomachs. At this stage of the fetal development the gastric epithelial cells are undifferentiated. The explants were cultured in DMEM/F-12 medium supplemented with fetal calf serum only, or fetal calf serum combined with either hydrocortisone or pentagastrin. Morphological characterization by means of light microscopy, dye staining and immunostaining was used to identify the growing cells. Both hydrocortisone and pentagastrin accelerated the differentiation towards H,K-ATPase-positive cells, mucus-producing cells and other epithelial cells. H,K-ATPase-positive cells, which were identified by immunostaining with a monoclonal antibody reacting with the alpha-subunit of the H,K-ATPase, grew on top of the confluent layer of epithelioid and fibroblastoid cells. With this method in vitro investigations of the mechanisms of proliferation and differentiation of gastric mucosal cells are possible. Although by different mechanisms, both hydrocortisone and pentagastrin appear to play a regulatory role in these processes.

Cellular proliferation and differentiation in rat atrophic gastric mucosa induced by N'-methyl-N'-nitro-N-nitrosoguanidine

It has been demonstrated that mucosal cell proliferation in atrophic gastritis is significantly accelerated, although the dynamics of the cell proliferation and differentiation have not been well characterized. We sequentially analyzed the markers of proliferation and differentiation of rat atrophic gastritis induced by MNNG. Immunohistochemical staining by anti-BrdU, anti-PCNA, and anti-PDGF-BB antibodies demonstrated that cell proliferation in atrophic gastritis was accelerated not only in the parenchymal tissue but also in the mesenchymal tissue. Expression of a gap junction protein (connexin 32), which is a marker for differentiation of epithelial cells, was reduced during the progression of atrophy. Some apoptotic cells were observed in the lower to middle third of the atrophic mucosa, whereas apoptotic cells were rarely seen in normal mucosa, which suggests that apoptosis in these parts of the mucosa may be related to the occurrence of mucosal atrophy.

G protein-coupled cholecystokinin-B/gastrin receptors are responsible for physiological cell growth of the stomach mucosa in vivo

Many peptide hormone and neurotransmitter receptors belonging to the seven membrane-spanning G protein-coupled receptor family have been shown to transmit ligand-dependent mitogenic signals in vitro. However, the physiological roles of the mitogenic activity through G protein-coupled receptors in vivo remain to be elucidated. Here we have generated G protein-coupled cholecystokinin (CCK)-B/gastrin receptor deficient-mice by gene targeting. The homozygous mice showed a remarkable atrophy of the gastric mucosa macroscopically, even in the presence of severe hypergastrinemia. The atrophy was due to a decrease in parietal cells and chromogranin A-positive enterochromaffin-like cells expressing the H+,K(+)-ATPase and histidine decarboxylase genes, respectively. Oral administration of a proton pump inhibitor, omeprazole, which induced hypertrophy of the gastric mucosa with hypergastrinemia in wild-type littermates, did not eliminate the gastric atrophy of the homozygotes. These results clearly demonstrated that the G protein-coupled CCK-B/gastrin receptor is essential for the physiological as well as pathological proliferation of gastric mucosal cells in vivo.

Foveolar hyperplasia following partial gastrectomy results from expansion of surface mucous cell compartment

Antrectomy with gastroenterostomy reconstruction is often associated with the development of foveolar hyperplasia and oxyntic atrophy. While a role for bile reflux in the etiology of foveolar hyperplasia is well established, the identity of the mucous cell lineages responsible for this condition have not been well characterized. We have studied three patients who demonstrated foveolar hyperplasia in their gastric remnant following antrectomy and gastroenterostomy. Mucosal samples were stained with antibodies against the trefoil peptides pS2 and hSP, to identify surface mucous and mucous neck cell lineages, respectively. Postoperative biopsies from all three patients showed oxyntic atrophy as documented by staining of parietal cells with antibodies against H/K-ATPase. All three patients demonstrated an exclusive expansion of pS2 immunoreactive mucous cells. The hSP staining cells were located deep in the expanded foveolar region. The results suggest that foveolar hyperplasia following antrectomy with gastroenterostomy results from a reactive hyperplasia of surface mucous cells. This pattern of surface cell hyperplasia is more consistent with a reactive expansion of mucous cells than with a response to chronic injury.

[The differentiation of the surface mucous-cell line in the abomasum of the adult cow]

The differentiation of the surface mucous-cell lineage during physiological cell renewal was investigated using light and electron microscopy in the abomasal mucosa of adult cattle. The surface mucous cells constitute a morphologically and functionally heterogeneous population, whose members correspond to different developmental stages, OFFanged in a distoproximal gradient from the depth of the pit towards the free luminal surface. The cell lineage comprises immature pre-pit cells near the proliferative isthmus, mature pit cells within the foveola, and older interfoveolar cells lining the free surface. Ultrastructurally, differentiation can be traced towards a predominantly mucus-producing cell type and finally towards a surface-protective cell variant, which degenerates in situ and is extruded into the lumen without affecting epithelial integrity.

Differential expression of extracellular matrix components during the morphogenesis of human gastric mucosa

BACKGROUND

Components of extracellular matrix play a crucial role in morphogenesis and epithelial cell differentiation. In this study, we examined the spatiotemporal expression and distribution of several major extracellular macromolecules of developing and adult human gastric mucosa, with particular emphasis on the pit-gland axis.

METHODS

Indirect immunofluorescence was performed on cryosections of developing and adult gastric tissues by using specific antibodies.

RESULTS

From 8 weeks of gestation onward, including adults, heparan sulfate proteoglycan, type IV collagen, and laminin alpha 1, beta 1, and gamma 1 chains were systematically and uniformly located at the basement membrane of the stratified epithelium (8-11 weeks) and of surface and pit-gland epithelia. Between 8 and 20 weeks of gestation, fibronectin and tenascin were colocalized throughout the entire mesenchyme. In adult mucosa, fibronectin was distributed at all levels of surface and glandular epithelium, whereas tenascin expression was restricted to surface and pit epithelial cells. The expression of the alpha 2 laminin chain was first detected at 12 weeks at the base of forming gastric glands. In the adult, the alpha 2 as opposed to the alpha 1 chain of laminin was confined to the basement membrane of the glandular and lower part of gastric pit epithelia.

CONCLUSIONS

This analysis of the composition of the extracellular matrix in human gastric mucosa suggests an important role for some of its components in morphogenesis and maintenance of gastric glands.

A light and electron microscopic radioautographic study on RNA synthesis in the retina of chick embryo

The incorporation of 3H-uridine into RNA of chick embryo retina was studied by light and electron microscopic radioautography. The numbers of silver grains were counted over the nucleus, nucleolus and cytoplasm of the cells in three different regions of the same retina of 2, 3, 4, and 7 day chick embryos. The results showed an increase of 3H-uridine incorporation from embryonic day 2 to 7. In every stage of development of the chick embryo retina, the number of silver grains was higher in the anterior than in the other two regions of the retina. In the three cell compartments of every embryo group, the number of silver grains was higher in the nucleus than in the nucleolus and cytoplasm. The results show further that the grains were less in the cytoplasm of the retinal cells of the day 2 embryo group and higher in the other groups especially in the day 7 embryos. Ultrastructural changes were also observed during the studied period of retina development.

Involvement of BCL-2 oncoprotein in the development of enterochromaffin-like cell gastric carcinoids

To evaluate the involvement of the apoptosis-suppressing protein BCL-2 in the gastrin-dependent mechanism of induction of gastric enterochromaffin-like (ECL) cell carcinoids, the endocrine cell of the oxyntic mucosa were immunohistochemically investigated in (a) 10 normogastrinemic subjects with histologically normal gastric mucosa; (b) 22 patients with endocrine cell hyperplasia and affected by hypergastrinemic conditions with different risk of gastric carcinoid development, such as sporadic Zollinger-Ellison syndrome (sZES; n = 9), ZES associated with multiple endocrine neoplasia-1 (MEN-1; n = 4), and atrophic fundal gastritis (AFG; n = 9); (c) 14 patients with ECL gastric carcinoids accounting for a total of 31 tumors investigated. In the normal oxyntic mucosa, BCL-2 was consistently expressed by a subset of endocrine cells accounting for 50.0% (median; range, 24.6-74.0%) of the total number of endocrine cells immunostained for chromogranin A (CgA) in consecutive sections. BCL-2 immunoreactive cells were located mostly in the middle mucosal layer, suggesting a role for the protein during downward migration of maturing endocrine cells. No BCL-2 immunoreactivity was found in other specialized gastric epithelial cells. Expression of BCL-2 by hyperplastic oxyntic endocrine cells (mostly ECL cells) varied in parallel with the risk of carcinoid development. In fact, the ratio of BCL-2- to CgA-immunoreactive cells was reduced (median, 4.6%; p less than 0.0001; range, 0.9-42.0%) in sZES, a condition showing virtually no risk, unchanged (median, 55.6%; range 29.4-83.8 %) in cases of MEN-1/ZES with intermediate risk, and increased (median 87.6%; p less than 0.014; range, 48.8-199.4%) in cases of AFG, a condition at the highest risk of carcinoid. In ECL cell carcinoids, BCL-2 expression varied markedly from one tumor to another even in the same patient and was low or absent in most cases. In both hyperplastic and neoplastic ECL cells, an inverse relation between BCL-2 expression and CgA immunoreactivity, that is, the cell granule content, was found. These results suggest that BCL-2 expression by hyperplastic ECL cells is independent of the influence of serum gastrin and may contribute to the development of ECL cell carcinoid tumors by extending cell exposure to oncogenic factors. Once a carcinoid tumor is established, BCL-2 expression becomes inconsistent.

Overexpression of transforming growth factor-alpha alters differentiation of gastric cell lineages

Overexpression of transforming growth factor-alpha (TGF-alpha) in the gastric fundic mucosa of metallothionein promoter/enhancer-TGF-alpha(MT-TGF-alpha) transgenic mice produces a phenotype of foveolar hyperplasia similar to that observed in Ménétrier's disease. We have investigated the dynamics involved in the alterations of gastric mucosal morphology in the MT-TGF-alpha mouse model. The fundic mucosa of MT-TGF-alpha mice and nontransgenic littermates was evaluated in animals treated with cadmium sulfate. To mark the mucosal proliferative zone, 8-bromodeoxyuridine (BrdU) was administered 2 hr prior to killing. Gastric mucosa was examined by diastase-resistant, periodic acid-Schiff-positive (DR-PAS) staining and immunohistochemistry for H/K-ATPase an BrdU. MT-TGF-alpha mice demonstrated increased numbers of DR-PAS-staining mucous cells and lower parietal cell numbers per gland unit. While the proliferative zone in nontransgenic mice was located in the upper half of the gland, the zone in MT-TGF-alpha mice was located in the basal region. Overexpression of TGF-alpha in MT-TGF-alpha mice leads to an alteration in the development of mucosal lineages from the fundic progenitor zone, which is biased towards the predominant differentiation of foveolar mucous cells.

Genetic ablation of parietal cells in transgenic mice: a new model for analyzing cell lineage relationships in the gastric mucosa

The gastric mucosa of mammalian stomach contains several differentiated cell types specialized for the secretion of acid, digestive enzymes, mucus, and hormones. Understanding whether each of these cell lineages is derived from a common stem cell has been a challenging problem. We have used a genetic approach to analyze the ontogeny of progenitor cells within mouse stomach. Herpes simplex virus 1 thymidine kinase was targeted to parietal cells within the gastric mucosa of transgenic mice, and parietal cells were ablated by treatment of animals with the antiherpetic drug ganciclovir. Ganciclovir treatment produced complete ablation of parietal cells, dissolution of gastric glands, and loss of chief and mucus-producing cells. Termination of drug treatment led to the reemergence of all major gastric epithelial cell types and restoration of glandular architecture. Our results imply the existence of a pluripotent stem cell for the gastric mucosa. Parietal cell ablation should provide a model for analyzing cell lineage relationships within the stomach as well as mechanisms underlying gastric injury and repair.

Oxyntic cell differentiation during physiological cell renewal in abomasal mucosa of adult cattle

The origin and differentiation of the oxyntic cell lineage during physiological cell renewal was investigated by light and electron microscopy in the abomasal mucosa of adult cattle. The morphologically heterogeneous oxyntic cell population exhibits various developmental subtypes depending on the position within the oxyntic unit. Pre-oxyntic cells of the isthmus and neck represent the immature precursors. Though heterogeneous with respect to the degree of canalicular and tubulovesicular membrane development, they all contain secretory granules resembling those of either isthmus cells, immature surface mucous cells, neck cells or young chief cells. A secretory granule-free stem cell is not present in the bovine. Downward to the gland base genesis of canalicular as well as tubulovesicular membranes is gradually completed; thus pre-oxyntic cells give rise to mature oxyntic cells. Older degenerative oxyntic cells, primarily located within the gland bottom, are characterized by progressive involution of canalicular and tubulovesicular membranes. Towards the pit, differentiation of pre-oxyntic cells is associated with atypical and incomplete development of canaliculi and tubulovesicles. In consequence, these superficial oxyntic cells have a reduced secretory capacity from a morphological point of view.

Diphtheria toxin-mediated ablation of parietal cells in the stomach of transgenic mice

The self-renewing epithelial populations present in the gastric units of the mouse stomach are descended from a multipotent stem cell and undergo an orderly migration-associated differentiation followed by apoptosis. The steady state census of the three principal cell types (acid-producing parietal cells, mucus-producing pit cells, and pepsinogen and intrinsic factor-producing zymogenic cells) is accurately controlled, despite marked differences in the rates of migration of each lineage. A transgenic mouse model has been created to define functional interrelationships between the proliferation, differentiation, and death programs of these lineages. Nucleotides -1035 to +24 of the noncatalytic beta subunit gene of mouse H+/K+-ATPase were used to direct expression of an attenuated diphtheria toxin A subunit in the parietal cell lineage. These transcriptional regulatory elements are not active in members of the pit and zymogenic lineages. Stomachs, prepared from postnatal day 28-80 transgenic mice and their normal littermates, were subjected to single- and multilabel immunohistochemical studies as well as qualitative and quantitative light and electron microscopic morphologic analyses. The toxin produced complete ablation of differentiated parietal cells. Loss of parietal cells was accompanied by a 5-fold increase in the number of undifferentiated granule-free cells located in the proliferative compartment of gastric units. This amplified population of granule-free cells included the multipotent stem cell as well as committed precursors of the pit and zymogenic lineages. Loss of mature parietal cells was also associated with (i) a block in the differentiation program of the zymogenic lineage with an accumulation of pre-neck cells and a depletion of their neck and mature zymogenic cell descendants, and (ii) an approximately 2-fold amplification of pit cells. These findings are consistent with the notion that epithelial homeostasis within gastric units is maintained by instructive interactions between their different cell lineages. Unlike pit and zymogenic cells, parietal cells complete their differentiation in the gastric unit's proliferative compartment before undergoing a bipolar migration along the unit. Thus, the mature parietal cell is in a strategic position to influence decision-making among gastric epithelial cell precursors and to modulate the migration-associated terminal differentiation programs of the pit and zymogenic lineages.