Effect of prostaglandin E2, cAMP and histamine on glycoprotein synthesis in isolated cells of the rat gastric mucosa

It was discovered that prostaglandin E2 (PGE2), but not histamine, increased the incorporation of 3H-N-acetyl-D-glucosamine and 14C-amino acids into the acid-insoluble protein fraction of isolated, mainly mucoid cells of rat gastric mucosa. The cAMP at the dose of 1 mM enhanced, like the PGE2, the synthesis of gastric mucoids. Cycloheximide inhibited the basal incorporation of labelled N-acetyl-D-glucosamine and the amino acid mixture by 28 and 72%, respectively, and blocked completely the PGE2 effect on glycoproteins formation. It is suggested that the PGE2, unlike histamine, enhances the biosynthesis of glycoproteins in the mucoid cells of rat gastric mucosa. The cAMP is believed to be a messenger of the PGE2 effect.     

Taenia taeniaeformis: Increased cell growth and neutral mucus production in the gastric mucosa of the rat with a larval infection

Gross hyperplasia of the gastric mucosa and excessive mucus production in the stomach occur in rats heavily parasitized with larvae of Taenia taeniaeformis. In this study, a positive correlation between the number of larvae recovered from hepatic cysts and the weight of the stomachs of infected rats was found. By light microscopy, the hyperplasia was restricted to the glandular mucosa. Parietal and chief cells were very rare, and densely PAS-positive mucous cells were the major cell types in the hyperplastic stomach while, in comparison, alcian blue-positive cells were much fewer in number. The isolated gastric mucosa in organ culture had an increased [³H]thymidine incorporation rate in rats infected with T. taeniaeformis. The hexosamine concentration per milligram protein in the hyperplastic stomach mucosa was twice that in the control rat stomach mucosa. By electron microscopy, the apical cytoplasm of the mucous cells was found to be filled with small dark granules. These results indicate that the gastric hyperplasia is caused by stimulation of growth and major differentiation of stem cells to neutral mucus-producing cells.     

De novo biosynthesis and localization of immunoreactive inhibin (10.7 kDa) in normal human stomach.

We have previously reported the occurrence of inhibin-like peptide in gastric juice of normal men. In the present investigation, normal gastric mucosa was shown to synthesize inhibin, in vitro, as measured by 3H-leucine incorporation (Maximum at 18 h). Furthermore, the immunohistochemical localization studies demonstrated its presence in the acid secreting parietal cells and basal region of foveolar epithelium of gastric mucosa. Surprisingly, the protein secreting zymogen cells remained unstained.     

Light and Electron Microscopy of the European Beaver (Castor fiber) Stomach Reveal Unique Morphological Features with Possible General Biological Significance

Anatomical, histological, and ultrastructural studies of the European beaver stomach revealed several unique morphological features. The prominent attribute of its gross morphology was the cardiogastric gland (CGG), located near the oesophageal entrance. Light microscopy showed that the CGG was formed by invaginations of the mucosa into the submucosa, which contained densely packed proper gastric glands comprised primarily of parietal and chief cells. Mucous neck cells represented <0.1% of cells in the CGG gastric glands and 22–32% of cells in the proper gastric glands of the mucosa lining the stomach lumen. These data suggest that chief cells in the CGG develop from undifferentiated cells that migrate through the gastric gland neck rather than from mucous neck cells. Classical chief cell formation (i.e., arising from mucous neck cells) occurred in the mucosa lining the stomach lumen, however. The muscularis around the CGG consisted primarily of skeletal muscle tissue. The cardiac region was rudimentary while the fundus/corpus and pyloric regions were equally developed. Another unusual feature of the beaver stomach was the presence of specific mucus with a thickness up to 950 µm (in frozen, unfixed sections) that coated the mucosa. Our observations suggest that the formation of this mucus is complex and includes the secretory granule accumulation in the cytoplasm of pit cells, the granule aggregation inside cells, and the incorporation of degenerating cells into the mucus.     

The mucin biosynthesis stimulated by epidermal growth factor occurs in surface mucus cells, but not in gland mucus cells, of rat stomach

Although epidermal growth factor (EGF) accelerates gastric mucin biosynthesis, information on whether its activation is limited to the specific mucus-producing cells is lacking. In this paper, we investigated the effects of EGF on mucin biosynthesis and the expression of its receptor in distinct layers of rat gastric mucosa, including the possible participation of nitric oxide (NO). EGF enhanced the incorporation of [3H]glucosamine and [14C]threonine into the mucin in the full-thickness tissues of the gastric mucosa. This stimulation disappeared on the removal treatment of the surface mucosal layer chiefly consisting of surface mucus cells. The EGF-induced increase in [3H]-labeled mucin in the full-thickness mucosa was not suppressed by either NG-nitro-L-arginine (10(-5) M) or 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (10(-5) M). The EGF-receptor-mRNA expression was high in the surface mucosal layer but low in the deep and muscle layers of the stomach. These results suggest that EGF-induced stimulation of mucin biosynthesis is limited to the surface mucus cells of the rat gastric mucosa and is independent of the NO pathway.     

Mast cells in the rat gastric mucosa are not primarily responsible for PGD2 generation

The present study investigates the contribution of gastric mast cells on PGD2 generation in rat gastric mucosa. Cold-restraint induced stress or i.v. carbachol injection methods were used for gastric mast cell degranulation. In 19 stressed, 15 carbachol-infused and 14 control rats, gastric mast cell counts and gastric mucosa PGD2 assay were performed. Gastric mucosal content of PGF2 alpha was also determined in carbachol infused and control rats. The mean number of gastric mast cells was significantly lower in stressed and carbachol infused than in control rats. Despite these differences in gastric mast cell counts, neither PGD2 or PGF2 alpha contents in the gastric mucosa were significantly different in mast cells degranulated rats than in control animals. These results suggest another source of PGD2 in the rat gastric mucosa other than mast cells.     

Cellular localization of dopamine receptors in the gastric mucosa of rats

Dopamine (DA) plays a critical role in the protection of gastric mucosa and is mediated through corresponding receptors. However, the details of the expression of DA receptors (D1-D5) in the gastric mucosa are lacking. The present study investigated the expression and cellular localization of DA receptors in rat gastric mucosa by means of real-time PCR and immunofluorescent techniques. The results indicated that the mRNA expressions of all five subtypes of DA receptors were found in the gastric mucosa, among which the D2 level was the highest. The immunopositive cells of D1-D3 and D5 were primarily localized to the basilar gland of the epithelial layer in gastric corpus, but D4 immunoreactivity (IR) was only observed in the enteric nerve plexus. The D1, D2, and D5 IR were found in pepsin C-IR cells except D3. No IR of any DA receptor was detected in the H(+)/K(+)-ATPase- or mucin 6-IR cells. In conclusion, for the first time, this study demonstrates the predominant distribution of DA receptors in the chief cells, not the parietal and mucous neck cells, in rat gastric mucosa, thus suggesting that DA may not directly regulate the function of parietal cells or mucous neck cells, but it may modulate the function of chief cells through the D1, D2, and D5 receptors.     

应激状态下NO的胃粘膜保护作用及其与壁细胞泌酸的关系

目的:探讨应激状态下一氧化氮(NO)的胃粘膜保护作用及其与壁细胞泌酸的关系.方法:采用水浸-束缚应激(WRS)方法制备应激性溃疡(SU)动物模型,检测胃粘膜溃疡指数(UI)、胃粘膜NO含量和壁细胞H ,K -ATPase活性,观察L-硝基精氨酸甲酯(L-NAME)和L-精氨酸(L-Arg)对应激后大鼠壁细胞H ,K -ATPase活性及胃粘膜损伤的影响.结果:L-NAME(20 mg·kg-1)可使胃粘膜NO含量减少(P＜0.01),壁细胞H ,K -AT-Pase活性增加(P＜0.05),并加重应激所致的胃粘膜损伤;L-Arg(300 mg·kg-1)则使胃粘膜NO含量增加(P＜0.01),壁细胞H ,K -ATPase活性下降(P＜0.05),减轻应激所致胃粘膜损伤.结论:NO对应激状态下大鼠胃粘膜具有保护作用,其机制与抑制壁细胞H ,K -ATPase活性有关.     

Effect of low pH on the morphology and viability of Cryptosporidium andersoni sporozoites and histopathology in the stomachs of infected mice

The genus Cryptosporidium includes many common parasites infecting animals and humans, and is a major cause of diarrheal illness worldwide. The biology of gastric Cryptosporidium spp., including replication in the stomach, has not been well documented. This study evaluated the viability of Cryptosporidium andersoni sporozoites in gastric environments after excystation and examined the endogenous development and histopathological changes in the stomachs of infected mice, using a novel type of C. andersoni. Sporozoites were affected by low pH (61.6% viability after 3h at pH2.0). Electron microscopy revealed developmental parasites on the gastric foveolae but not on the surface of the gastric mucosa. Histopathological examinations at 1, 2, 4 and 12 weeks p.i. uncovered three different lesions. The gastric mucosa of foveolae filled with parasites was extended and the amount of neutral mucopolysaccharide at the mucosal surface was decreased with the first type of lesion. The gastric mucosa was atrophied, some gastric glands were disrupted and the amount of acid mucopolysaccharide at the mucosal surface was increased with the second type. Finally, the gastric mucosa was slightly extended and goblet cells were present in the gastric mucosa, indicating intestinal metaplasia, in the third type. No parasites were detected in these areas with increased acidic mucin and indications of metaplasia. The results suggest that C. andersoni parasites could not survive in acidic environments for a long period before invading host cells and preferentially develop in neutral sites of the gastric mucosa, resulting in histopathological changes and chronic shedding of oocysts.     

Mucosal nerves and smooth muscle relationships with gastric glands of the opossum: an ultrastructural and three-dimensional reconstruction study

The precise anatomical relation by which autonomic nerve endings contact gastric epithelial cells to enhance the rate of gastric secretions is not fully understood. The aim of the present study was to clarify this issue by using the technique of serial section reconstruction of areas of the gastric mucosa. The work also explored the possibility of a functional role for a system of smooth muscle strands in the gastric mucosa that emanate from the muscularis mucosa, run in the lamina propria, and are associated in a unique manner with the gastric glands. Electron microscopic serial sections of the gastric mucosa were performed to visualize the entire limiting membrane of gastric epithelial cells to determine any nerve associations (especially varicose endings) with these cells. Evaluation of serial sections of five separate parietal cells showed that their basal membrane did not come in close contact (nearest distance 500 nm) with any nerve axon or varicosity. Moreover, the axons passing in the area of these cells ultimately showed varicose endings associated with smooth muscle cells in the adjacent connective tissue (often separated by only 20 nm), with mast cells or with vascular elements. Additionally, the lateral membrane of these five parietal cells did not contact any endocrine cell in the epithelium, although other parietal cells in the area were adjacent to endocrine cells. Chief cells in the immediate area also did not form any close associations with nerve varicosities. Random analysis of 5,000 additional epithelial cells in these sections showed no close associations to nerve elements with significant accumulations of neurosecretory vesicles (varicosities). Because of the observed existence of innervation to the smooth muscle strands in the area of the gastric glands, serial 1-micron epoxy sections of the gastric mucosa were prepared, and profiles of smooth muscle and gastric glands were entered into a computer-assisted reconstruction system. Three-dimensional reconstruction techniques were employed to reveal the existence of a unique association between the mucosal smooth muscle strands and the gastric glands. The muscle strands arose from the muscularis mucosa at regular intervals and became branched to form an intricate wrap around a series of gastric glands that empty into one gastric pit.(ABSTRACT TRUNCATED AT 400 WORDS)     

Lysosomal enzyme activity of the gastric mucosa in rats during experimental ulcer formation

Lysosomal membrane stability has been studied in the gastric mucosa in response to mechanical damage caused by lysosomal fractionation and release of lysosomal enzymes from mucous cells into the gastric cavity of alive animals during induction of acetic ulcer or erosive damage of the gastric mucosa resulting from intraperitoneal introduction of histamine and serotonin. It has been found that all types of ulcerogenesis in the gastric mucosa led to the decrease in lysosomal membrane stability to mechanical stress in the course of lysosomal fractionation. In addition there was a substantial release of lysosomal enzymes into the gastric cavity in different types of ulcerogenesis. The decrease in lysosomal membrane stability combined with a subsequent development of ulcers and erosions in the gastric mucosa seems indicative of the fact that lysosomal enzymes take part in the initial formation of ulcers in the gastric mucosa.     

Comparative study of histological and kinetic variations of the digestive mucosa and pancreatic parenchyma after hypophysectomy in the rat. Light and electron microscopic study

Variations of the pancreatic parenchyma, the gastric mucosa and the intestinal mucosa were studied in adult male Wistar rats on day 8 and 15 after hypophysectomy. All results were compared with those obtained in pair-fed control rats. Hypophysectomy affected small intestine as well as gastric mucosa. Hypotrophy was observed on day 8 as most of the morphological parameters reached the maximal decrease. By contrast, hypoplasy occurred on day 15, when the labeling index (LI) decreased significantly. In the intestine, however, a decrease of the LI was observed only for the upper proliferative cells of the crypts. In the gastric mucosa, the LI was reduced only in the proliferative zone containing progenitor cells (isthmic region). Consequently, the cell differentiation is not similarly affected on all levels of the digestive tract.     

慢性溴氰菊酯摄取对大鼠胃黏膜损伤及P物质的表达的影响

目的:探索溴氰菊酯慢性中毒对大鼠胃黏膜的病理损伤及损伤后P物质表达的影响.方法:实验组大鼠分别给予不同荆量溴氰菊酯灌胃,对照组仅给予橄榄油.取胃体部组织,制成石蜡切片,HE及免疫组织化学染色,镜下观察胃黏膜损伤及胃黏膜组织P物质的表达情况,并对损伤程度进行累计积分、壁细胞计数.结果:高剂量组大鼠胃粘膜慢性损害病理积分与各组相比差异均有显著性(P＜0.05);壁细胞计数与对照组相比较其差异有P＜0.05).免疫组化发现SP在实验组大鼠胃黏膜组织中呈强阳性表达,在对照组则呈弱阳性表达;平均光密度(OD)值显示高、中剂量组之间及与其余各组之间差异均有显著(P＜0.05l.结论:溴氰菊酯对大鼠胃黏膜有较明显的慢性损伤,SP可能参与胃黏膜局部病变.     

Ultracytochemical study of oxidoreductases in the parietal cells of the gastric mucosa in gastric cancer

Ultracytochemistry was used to study and compare cytochromooxidase, succinate dehydrogenase and NADH-dehydrogenase activity in gastric mucosa parietal cells in health and in gastric carcinoma associated with decreased acidity of gastric juice. The study demonstrated the reduced activity of the enzymes listed in the mucosal parietal cells in gastric carcinoma. This finding is interpreted as a consequence of disturbed energy supply of hydrochloric acid secretion in gastric carcinoma.     

Effect of long-term prostacyclin treatment on the gastric mucosa of rat

According to Bálint and Varró, oral administration of prostacyclin (PGI2) resulted in a significant increase of the DNA-content of the gastric mucosa within a short period of time. In the present study, there was no change in the protein content of the gastric mucosa after oral administration of 100 micrograms/kg/day of PGI2 for 80 days, while the DNA-content increased significantly. The RNA/DNA ratio decreased. Histologically a significant increase in the thickness of the gastric mucosa, as well as in the number of parietal and epithelial cells were found. The cell hyperplasia in the corpus mucosa was accompanied by a decreased number of G-cells of the antral mucosa. The increase of parietal cell number and the decrease of G-cell number after long term PGI2 administration might be explained by the divergent effect of treatment on the kinetics of the different cell types in the gastric mucosa.     

Antigenic activation of Th1 cells in the gastric mucosa enhances dysregulated apoptosis and turnover of the epithelial cells

Colonization of Helicobacter pylori in the stomach leads to chronic gastritis with massive infiltration by Th1 cells. To assess a role played by those T cells in the remodeling of gastric epithelium, we activated gastric T cells utilizing mice with CD4 T cells bearing transgenic TCR with or without deficiency in either IL-4 or IFN-gamma or IL-12. Mice developed gastritis upon injection of an antigen into gastric mucosa. While neutrophil infiltration occurred even with a control antigen, infiltration by transgenic T cells was dependent on the specific antigen. The numbers of epithelial cells undergoing apoptosis and regeneration were increased in the mice with infiltrating T cells producing IFN-gamma and the alignment of those cells in the glands was markedly dysregulated. In contrast, mice deficient in Th1 response showed no increase in cell division and apoptosis of epithelial cells. Thus, Th1 type T cells infiltrating into gastric mucosa play an independent role in controlling turnover of epithelial cells.     

Role of Na-K-2Cl cotransporter-1 in gastric secretion of nonacidic fluid and pepsinogen

Na-K-2Cl cotransporter-1 (NKCC) has been detected at exceptionally high levels in the gastric mucosa of several species, prompting speculation that it plays important roles in gastric secretion. To investigate this possibility, we 1) immunolocalized NKCC protein in the mouse gastric mucosa, 2) compared the volume and composition of gastric fluid from NKCC-deficient mice and their normal littermates, and 3) measured acid secretion and electrogenic ion transport by chambered mouse gastric mucosa. NKCC was localized to the basolateral margin of parietal cells, mucous neck cells, and antral base cells. In NKCC-deficient mice, gastric secretions of Na+, K+, Cl-, fluid, and pepsinogen were markedly impaired, whereas secretion of acid was normal. After stimulation with forskolin or 8-bromo-cAMP, chambered corpus mucosa vigorously secreted acid, and this was accompanied by an increase in transmucosal electrical current. Inhibition of NKCC with bumetanide reduced current to resting levels but had no effect on acid output. Although prominent pathways for basolateral Cl- uptake (NKCC) and apical Cl- exit [cystic fibrosis transmembrane conductance regulator (CFTR)] were found in antral base cells, no impairment in gastric secretion was detected in CFTR-deficient mice. Our results establish that NKCC contributes importantly to secretions of Na+, K+, Cl-, fluid, and pepsinogen by the gastric mucosa through a process that is electrogenic in character and independent of acid secretion. The probable source of the NKCC-dependent nonacidic electrogenic fluid secretion is the parietal cell. The observed dependence of pepsinogen secretion on NKCC supports the concept that a nonacidic secretory stream elaborated from parietal cells facilitates flushing of the proenzyme from the gastric gland lumen.     

Helicobacter pylori infection and antioxidants can modulate the genotoxic effects of heterocyclic amines in gastric mucosa cells

Helicobacter pylori (H. pylori) infection plays an important role in gastric carcinogenesis. This bacterium may induce cancer transformation and change the susceptibility of gastric mucosa cells to various exogenous dietary irritants. The aim of the study was to evaluate the influence of H. pylori infection on the reaction of the stomach cells to a genotoxic effect of heterocyclic amines (HCAs). These well-known mutagens are formed during cooking of protein-rich foods, primarily meat. Taking into account that persons consuming a mixed-western diet are exposed to these compound nearly an entire lifetime and more than half of human population is infected with H. pylori, it is important to assess the combined effect of H. pylori infection and HCAs in the context of DNA damage in gastric mucosa cells, which is a prerequisite to cancer transformation. We employed 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) because these substances are present in a great amount in cooked and fried meat. Using alkaline comet assay, we showed that the extent of the DNA damage induced by HCAs was significantly higher in H. pylori infected gastric mucosa cells than in non-infected counterparts. We did not observed any difference in the efficiency of repair of DNA lesions induced by HCAs in both type of cells. Vitamin C reduced the genotoxic effects of HCAs in H. pylori infected and non-infected gastric mucosa cells. Melatonin more effectively decreased DNA damage caused by HCAs in H. pylori infected gastric mucosa cells as compared with control. Our results suggest that H. pylori infection may influence the susceptibility of gastric mucosa cells to HCAs and dietary antioxidative substances, including vitamin C and melatonin may inhibit the genotoxic effects of HCAs on gastric mucosa cells and may reduce the risk of carcinogenesis caused by food borne mutagens and H. pylori infection.