Hella Gergely

Increased expression of epidermal growth factor receptor during gastric ulcer healing in rats

Expression of epidermal growth factor receptor (EGFR) was studied immunohistochemically in rat gastric mucosa during healing of acetic acid-induced ulcers. In normal control gastric oxyntic mucosa, EGFR was expressed in proliferative zone cells and in some parietal cells. In mucosa of the ulcer margin, at 3, 7, and 16 days after ulcer induction, there was a 75-fold increase (over controls) in the number of cells expressing EGFR. Seventy percent of ulcers healed by the 16th day, and all were healed by the 25th day. The mucosal scar that replaced the ulcer was composed of dilated glands lined with poorly or aberrantly differentiated cells showing persistence of increased EGFR expression. An increased EGFR expression indicates an important role of EGF in ulcer healing and scar formation.

Protective Effect of Sucralfate Against Alcohol-Induced Gastric Mucosal Injury in the Rat: Macroscopic, Histologic, Ultrastructural, and Functional Time Sequence Analysis

Histologic or ultrastructural evidence of the ability of sucralfate to protect the gastric mucosa against ethanol injury is lacking. Therefore we analyzed morphologic and functional changes in the mucosa of 120 rats receiving, intragastrically, 2 ml of either sucralfate 500 mg/kg body wt or a control solution and 1 h later 2 ml of 100% ethanol. At 15 min, 1, 4, 6, and 24 h after ethanol instillation, mucosal changes were assessed by macroscopic examination, quantitative histology, scanning electron microscopy, recordings of gastric potential difference, and measurements of volume, pH, and electrolytes in the gastric contents. Between 15 min and 24 h after ethanol instillation, macroscopic necrotic lesions in controls involved greater than 33% of mucosal area and in the sucralfate-treated group less than 4% (p less than 0.001 for each period). In controls, ethanol instillation produced surface epithelial cell disruption and deep (greater than 0.2 mm) mucosal necrosis involving greater than 55% +/- 3% of the mucosal length. In sucralfate-pretreated animals, disruption of the surface epithelium was present at 15 min, 1 h, and 4 h after ethanol instillation, but deep necrotic lesions were virtually absent (0%-2%; p less than 0.001 vs. controls) during the entire study period. The surface epithelium was mostly reestablished by 6 h after ethanol instillation in the sucralfate group but not in the controls. We concluded that sucralfate protects the gastric mucosa against ethanol-induced injury by preventing deep mucosal necrosis and as a consequence the mucosal proliferative zone cells rapidly restitute mucosal integrity.

Quality of gastric ulcer healing: a new, emerging concept.

Assessment of gastric ulcer healing is usually based on a visual examination (by endoscopy in patients, or the evaluation of ulcer size in experimental studies), and not on histologic and ultrastructural assessment of subepithelial mucosal healing. This approach has led to the assumption that the mucosa of grossly “healed” gastric and/or duodenal ulcers returns to normal, either spontaneously or following treatment. However, the re-epithelialized mucosa of grossly “healed” experimental gastric ulcer has recently been found to have prominent histologic and ultrastructural abnormalities, including reduced height, marked dilation of gastric glands, poor differentiation and/or degenerative changes in glandular cells, increased connective tissue, and disorganized microvascular network. It has been postulated that these residual abnormalities might interfere with mucosal defense and may be the basis of ulcer recurrence. In the present article, the ulcer healing process and the role of luminal factors, transitional zone at the ulcer margin, and granulation tissue are discussed. The healing of an ulcer is accomplished by filling of the mucosal defect with epithelial cells and connective tissue to reconstruct mucosal architecture. Under influence of growth factors [predominantly epidermal growth factor (EGF) and transforming growth factor (TGFα)], the epithelial cells at the ulcer margin dedifferentiate and proliferate, supplying cells for re-epithelialization of the mucosal scar surface and reconstruction of glandular structures. Granulation tissue at the ulcer base supplies connective tissue cells to restore the lamina propria and endothelial cells and microvessels for mucosal microvasculature reconstruction. The final outcome of healing reflects a dynamic interaction between an “epithelial” component from the ulcer margin and a connective tissue component including microvessels originating from granulation tissue. Angiogenesis—the formation of new microvessels in granulation tissue—appears to be critical for the ulcer healing process. Indomethacin delays healing of experimental gastric ulcer and impairs the overall quality of ulcer healing by distorting restoration of mucosal architecture, blocking differentiation and maturation of glandular and surface epithelial cells, and inhibiting angiogenesis in granulation tissue. Aluminum-containing antacid (Maalox-70) accelerates healing of experimental gastric ulcer, improves the quality of mucosal structure reconstruction, and partly reverses the deleterious effect of indomethacin on the rate and quality of ulcer healing.

Does Sucralfate Affect the Normal Gastric Mucosa

Although the action of sucralfate on ulcerated mucosa has been demonstrated, its effect on the histology, ultrastructure, and function of normal gastric mucosa is unknown. We investigated the effect of acute administration of sucralfate on the gastric mucosal history, ultrastructure, mucosal potential difference, and luminal release of prostaglandin E2. At 15 min, 1 h, and 3 h after intragastric instillation of sucralfate, whitish incrustations of the drug were firmly adhering to the glandular mucosa. Mucosal histology after sucralfate administration demonstrated the following: disruption and exfoliation of some of the surface epithelial cells, mucosal hyperemia, prominent release of mucus from the surface epithelial cells, and edema of lamina propria and submucosa. These changes were most prominent in the areas where sucralfate was in contact with the mucosal surface. Scanning and transmission electron microscopy confirmed the above changes. Sucralfate produced a drop in gastric mucosal potential difference and a significant increase in luminal release of prostaglandin E2. Sucralfate produces distinct morphologic and functional changes in the normal gastric mucosa, which may account for its preventive and therapeutic efficacy.

Vascular and Microvascular Changes—Key Factors in the Development of Acetic Acid-Induced Gastric Ulcers in Rats

The present study examined the time sequence and histologic and ultrastructural features of the formation and evolution of experimental, acetic acid-induced gastric ulcerations in rats. One hundred percent acetic acid was applied to the gastric serosa of 140 fasted male Sprague-Dawley rats through a polyethylene tube for 30 s. Gastric mucosal changes were evaluated at 1, 5, 15, and 30 min, 1 and 3 h, and 1, 2, 3, 5, 8, and 11 days after acetic acid application by visual inspection, by quantitative and qualitative light microscopy, and by transmission electron microscopy. Following exposure to acetic acid, the earliest morphologic changes occurred at 1 min and consisted of dilatation of large submucosal veins and arteries and mucosal collecting venules. Five to 15 minutes after injury, thrombi developed in submucosal veins and collecting venules, leading to microvascular stasis and mucosal necrosis. By 3 h, necrotic masses started to detach. By 24–48 h, necrotic changes penetrated the submucosa. By 72 h, most ulcers underwent transition into a “chronic” stage characterized histologically by the presence of granulation tissue at the bottom, and the appearance of a transitional healing zone at the margins. By 5 days, an increased amount of granulation tissue was observed and the gastric glands in transitional zones at the ulcer margin displayed cystic dilatation. Based on this study, we conclude that a key feature of acetic acid-induced ulcer formation is the early vascular and microvascular injury, which precedes glandular cell necrosis.

Healed experimental gastric ulcers remain histologically and ultrastructurally abnormal

The present study was designed to assess histologic and iltrastructural features of gastric mucosa in the areas of rossly healed ulcers (acetic acid-induced gastric ulcers) in ats. The specific question we studied was whether the tructure and cellular composition of the gastric mucosa in n area of grossly healed ulcer were fully restored. Eighty prague-Dawley rats underwent laparotomy; 100% acetic cid was applied to the lower gastric corpus serosa for 30 s nd the abdomen was closed. The stomachs were reopened ter 2 weeks or after 2, 3, or 4 months. Standardized gastric all specimens from the area of grossly healed ulcers were btained, processed, and evaluated by light microscopy and y transmission electron microscopy. The gastric mucosa f grossly healed ulcers demonstrated re-epithelialization at ach study time but the mucosa beneath the surface epitheium displayed prominent histologic and ultrastructural abormalities. Two different patterns of scar could be distinuished: (a) the mucosa in the area of healed ulcer was hinner (25–45% reduction vs. normal), with increased onnective tissue and poor differentiation and/or degenerative changes in the glandular cells; or (b) the mucosa dislayed ballooning dilatation of gastric glands, reduction in he microvascular network, and poor differentiation of landular cells. We conclude that (i) the subepithelial muosa of grossly healed gastric ulcer displays disorganized estoration of glandular and vascular structures and renains histologically and ultrastructurally abnormal; (ii) hese abnormalities may interfere with oxygenation, nurient supply, and with mucosal resistance and defense, and herefore could be the basis for ulcer recurrence.

Gastric microvascular endothelium: a major target for aspirin-induced injury and arachidonic acid protection. An ultrastructural analysis in the rat.

Abstract. Exposure of the gastric mucosa to aspirin results in exfoliation of the surface epithelium and deep mucosal necrosis. We assessed the changes in the mucosal microvessels during aspirin‐induced injury and arachidonic acid protection of the gastric mucosa using transmission electron microscopy. Male Spra‐gue‐Dawley rats received intragastric pretreatment with either solubilizer (control) or detergent solubi‐lized arachidonic acid (148 mg kg‐1). One hour later 1‐ml suspension of 200 mg kg‐1 body weight acidified aspirin was administered intragastrically. The ultra‐structure of mucosal microvasculature was assessed at 15 min and 4 h after aspirin administration both qualitatively and quantitatively by determining the number of necrotic or damaged capillaries in standardized mucosal sections. In addition, mucosal specimens were immunostained with a specific antiserum against vimentin, an endothelial marker, and fluorescence intensity was measured with a Nikon FX microscopic photometric system. In control rats, aspirin produced significant damage to both superficial and deeper microvessels consisting of: rupture of capillary walls, necrosis of endothelial cells, damage to endothelial organelles, deposition of fibrin and adherence of platelets to damaged endothelium. Vimentin fluorescence was reduced three‐fold. Microvascular injury preceded the development of deep necrotic lesions. Microvascular damage and deep mucosal necrosis were significantly reduced by arachidonic acid pretreatment. We conclude that gastric mucosal microvessels are the major target for aspirin‐induced injury and arachidonic acid protection.,

Morphologic changes in gastric mucosa of aging rats

We examined histologic and ultrastructural changes in the gastric mucosa of aging rats. Standardized gastric specimens from Sprague-Dawley rats 3 months of age (young) and 24 months of age (old) were evaluated by qualitative and quantitative histology and transmission electron microscopy. Old rats had the following histologic changes: (1) partial atrophy of the gastric glands and their replacement with hyalinlike connective tissue; (2) cystic dilatation of the gastric glands at the bases with occasional squamous cell metaplasia; and (3) extensive perivascular depositions of PAS-positive material, negative for amyloid. The total mucosal thickness was 484±100 μm in young rats vs 1122 ±240μm in old rats (P<0.01). Electron microscopy demonstrated degenerative changes in parietal and chief cells, hyperplasia of surface and foveolar mucous cells, and prominent accumulation of disorganized collagen fibrils in perivascular connective tissue. This study indicates that the gastric mucosa of aging rats that have not been exposed to damaging agents does show definite histologic and ultrastructural changes.

Microvascular endothelium--a major target for alcohol injury of the human gastric mucosa. Histochemical and ultrastructural study.

In healthy volunteers, we studied the effect in intragastric administration of 100 ml 40% alcohol or isotonic saline on the ultrastructure of gastric oxyntic mucosa with emphasis on gastric mucosal microvasculature. We found that a single dose of 40% alcohol produces exfoliation of the surface epithelium, damage to the mucosal micro-vessels, extravasation of red blood cells and plasma from disrupted microvessels, and extensive edema of superficial lamina propria. The ultrastructural changes were seen as early as 5 min after alcohol administration and occurred in the mucosal areas where glandular cells did not show necrotic changes. Alcohol-induced injury was localized predominantly to interfoveolar mucosal areas and only occasionally extended to the neck areas. This study demonstrates that the mucosal microvasculature is a primary target for alcohol-induced injury of the human gastric mucosa.

Campylobacter pylori Interactions with Gastric Cell Tissue Culture

Many investigators have reported that gastric mucosal biopsies of patients with chronic gastritis and peptic ulcer disease show the presence of Campylobacter pylori in a large majority of cases. Histologic examinations of such tissues indicate a close approximation of C. pylori with gastric surface epithelial cells. A recent report has described both adherence and cell invasion of gastric cells by C. pylori. Using a transmission electron microscope, we have examined the interaction between C. pylori, C. jejuni, and E. coli in vitro with a gastric cancer cell line, Kato III. Our results indicate marked toxicity of E. coli and moderate toxicity of C. jejuni for Kato III cells. C. pylori had only a minor effect on tissue culture viability. C. pylori was found to have a strong association with the Kato III cell membranes and evidence of occasional cell invasion. Both C. tejuni and E. coli showed no attachment or association with the Kato III cells. We interpret these findings as indicating that C. pylori may have a specific adhesion for gastric cells.