Gregory L. Eastwood

EPITHELIAL CELL RENEWAL IN CULTURED RECTAL BIOPSIES IN ULCERATIVE COLITIS

Epithelial cell proliferation and migration were studied in cultured mucosal biopsies of the rectum from 14 patients with ulcerative colitis (DC) and eight normal volunteers. More than twice as many epithelial cells in the proliferative zone of the rectal crypts were labeled in autoradiographs of DC biopsies cultured for 6 hr over thymidine-3H-containing medium than in normal biopsies. Moreover, after 18 hr of additional culture over isotope-free medium, many more labeled cells had migrated to the upper crypts and the absorptive surface in the DC biopsies than in the normal biopsies. Electron microscopy of the surface epithelium of uncultured and cultured biopsies showed that the cytological abnormalities seen in freshly fixed DC biopsies persisted after 24 hr of culture. These studies indicate that epithelial cell proliferation is increased and the migration is accelerated in the rectal mucosa in patients with UC.

Organ Culture of Human Rectal Mucosa

Mucosal biopsies from human rectum were cultured in vitro using a simple organ culture system. Light microscopy consistently revealed good preservation of rectal mucosa in biopsies cultured for up to 24 hr. Moreover, mucosal morphology was well preserved in some but not all biopsies cultured for as long as 48 hr. Electron microscopy revealed preservation of surface epithelial cell structure in biopsies cultured for 24 hr. Autoradiographs of biopsies cultured over thymidine-3H-containing medium for 6 hr showed labeling of proliferating cells in the lower two-thirds of the rectal crypts. In biopsies subsequently cultured for an additional 18 hr over isotope-free medium, some of the labeled cells had migrated to the upper crypts and the absorptive surface. These studies show that mucosal morphology is maintained and that some epithelial cell proliferation continues for at least 24 hr in rectal mucosal biopsies cultured in vitro in this organ culture system.

Effect of pH on bile salt injury to mouse gastric mucosa. A light- and electron-microscopic study.

Bile salts break the gastric mucosal barrier. To explain this, the suggestion has been made that bile salts may disrupt surface epithelial cell membranes or break the tight junctions between cells, but appropriate ultrastructural studies are lacking. We therefore instilled control and bile salt-containing solutions into the stomachs of fasted mice at pH, 1, 3, 5, AND 7. Taurocholate (pKa equals 1.8) caused mucosal injury only at pH 1, whereas glycochenodeoxycholate (pKa equals 4.2) injured the mucosa at pH 1 and 3. By electron microscopy, areas of mild mucosal injury were characterized by clumping of nuclear chromatin and loss of cytoplasmic density within surface mucous cells. The apical cell membranes and tight junctions remained intact. In areas of severe damage surface cells were ruptured but tight junctions still appeared unbroken. These studies indicate that acid pH markedly augments the damaging effects of bile salts on mouse gastric mucosa. Moreover, as an initial step in the mechanism of bile salt-induced gastric injury, the nonionized moiety of a given bile salt which exists below its pKa may be important in altering the gastric surface epithelial cell in a way which allows the ingress of bile salt and/or hydrogen ion to cause intracellular damage.

Active Smoking Depresses Prostaglandin Synthesis in Human Gastric Mucosa

To determine the effect of smoking on gastroduodenal mucosal prostaglandin synthesis, endoscopies were done after an overnight fast on 10 nonsmokers, 12 active smokers who smoked four cigarettes in the hour before endoscopy, and then 11 of the smokers who refrained from smoking for 12 hours. Biopsy samples of fundic, antral, and duodenal mucosae were incubated, and the accumulation of prostaglandin E2 and 6-keto-prostaglandin F1 alpha in the incubation medium was measured by radioimmunoassay. We assumed that accumulation of prostaglandins in the medium reflected mucosal synthesis. Comparison of active and inactive smoking showed that active smoking significantly depressed 6-keto-prostaglandin F1 alpha synthesis in antral and fundic mucosa and prostaglandin E2 synthesis in antral mucosa. Comparison of nonsmokers and inactive smokers showed no difference in prostaglandin synthesis. Active smoking causes a transient decrease in prostaglandin synthesis in fundic and antral mucosae. This depression of prostaglandin synthesis may help explain slower ulcer healing and predisposition to ulcer recurrence in smokers.

smoking and peptic ulcer in the helicobacter pylori era

Before the recent understanding of the central importance of Helicobacter pylori in the pathogenesis of peptic ulcer disease, smoking had been regarded as an important contributor to the cause and perpetuation of the disease. In this review, we find that (1) clinical observations indicate that smokers are more likely to develop ulcers, ulcers in smokers are more difficult to heal, and relapse of ulcer disease is more likely in smokers, (2) smoking adversely affects the gastroduodenal mucosal protective mechanisms, thus predisposing to ulcer disease, (3) smoking adversely affects gastroduodenal motility, allowing reflux of harmful duodenal contents into the stomach, (4) smokers appear to be at higher risk of becoming infected with H. pylori and this increased risk may be due to the adverse effects of smoking on antioxidants or the immune system that may interfere with the normal protection against H. pylori, and (5) once H. pylori is eradicated in smokers, they appear to be at no greater risk of peptic ulcer disease. We conclude that smoking in itself appears not to be an independent ulcerogen, but may act by augmenting the harmful effects of H. pylori, both by adversely affecting upper gastrointestinal mucosal protection and physiology and by increasing the risk of H. pylori infection. Thus, we recommend that appropriate advice to ulcer patients who smoke continues to be: stop smoking.

Effect of chronic cimetidine ingestion on fundic and antral epithelial proliferation in the rat.

Recent reports of the association of cimetidine treatment with the development of gastric carcinoma stimulated us to study the effect of chronic cimetidine ingestion on epithelial proliferation in the stomach of male Wistar/Lewis rats. One group of rats received cimetidine in the drinking water to deliver 150–200 mg/kg/day. Control rats received plain water. To label proliferating cells, the rats were injected by tail vein with tritiated thymidine 1 hr before sacrifice at 1, 6, and 12 months. Sections of fundus and antrum were processed for light autoradiography. We found no histological evidence for malignant change and no effect on the measurements of epithelial proliferation by cimetidine in either fundus or antrum at any of the times studied, with the possible exception of an upward shift in the distribution of labeled cells within the proliferative zone of the fundus after 6 months. Thus, under the conditions of our experiments we have been unable to identify an effect of cimetidine on epithelial proliferation which would implicate it as a chemical carcinogen.

Cell proliferation in three types of Barrett's epithelium

Barretts epithelium is a columnar, possibly premalignant, metaplasia of the oesophagus. To study the pattern of epithelial renewal in this disorder, we localised the lower oesophageal sphincter by manometry in 12 patients with known Barretts epithelium, obtained multiple suction biopsies above the sphincter, and organ cultured the biopsies over 3H-TdR-containing medium to label proliferating cells. Of 23 biopsies from the 12 patients, 13 were specialised columnar type, three were junctional type, and seven were fundic type. None of the patients showed clinical evidence of oesophageal carcinoma, and oesophageal cytological examinations were uniformly negative for neoplastic cells. When compared with control gastric fundic biopsies from normal volunteers, mean values for the labelling index and the proportion of the pit which was occupied by the proliferative zone in Barretts biopsies were not significantly different. However, four individual Barretts biopsies (three specialised columnar type and one junctional type) did have a proliferative zone which occupied a greater proportion of the pit than did the widest control zone. We propose that the pattern of epithelial proliferation in Barretts epithelium in general is similar to that found in other gastrointestinal columnar epithelia. However, a minority of patients with Barretts epithelium may have an expanded proliferative zone. The clinical implications of an expanded proliferative zone with regard to the subsequent development of oesophageal carcinoma require further investigation.

Studies on the Mechanism of Esophagitis-Induced Lower Esophageal Sphincter Hypotension in Cats

Perfusion of 0.1 n HC1 5 cm above the lower esophageal sphincter (LES) in cats for 30 min on 4 consecutive days produced biopsy-documented esophagitis and marked decreases in LES pressure. Using this model the effects of experimental esophagitis on the LES response to edrophonium, pentagastrin, and bethanechol were determined. The sphincter response to both edrophonium and pentagastrin after esophagitis was induced was significantly less than preperfusion responses. When the esophagitis had resolved, the pressure response to edrophonium and pentagastrin returned to preperfusion levels. In contrast, the sphincter response to bethanechol during esophagitis was not different from the preperfusion response and remained unchanged after resolution of the esophagitis. Lower esophageal smooth muscle taken from cats with active esophagitis appeared normal by both light and electron microscopy. These studies indicate that besides decreasing resting LES tone, esophageal inflammation causes functional impairment of a cholinergic mechanism regulating LES pressure. In contrast, the smooth muscle appears to be unaffected by inflammation despite the LES hypotension.

Effects of Water Immersion Restraint Stress and Chronic Indomethacin Ingestion on Gastric Antral and Fundic Epithelial Proliferation

We studied the effects on gastric fundic and antral epithelial proliferation of acute water immersion restraint stress in rats and of chronic indomethacin ingestion in rats and humans using autoradiographic methods. Acute stress appeared to inhibit fundic epithelial proliferation but had no effect on antral proliferation in rats. We conjecture that this inhibition of fundic epithelial proliferation may help explain the development of stress-related mucosal lesions, which are more likely to occur in fundic mucosa. Chronic indomethacin ingestion stimulated fundic epithelial proliferation but had no effect on antral proliferation in both rats and humans. From these observations we conjecture that the failure of antral epithelial proliferation to respond to indomethacin may account in part for the ulcerogenic action of this drug.

Use of Ergonovine to Identify Esophageal Spasm in Patients with Chest Pain

We administered intravenous ergonovine maleate to 14 patients with chest pain resembling angina pectoris and to four healthy volunteers. Five of the patients experienced their typical chest pain after ergonovine, and manometric signs of esophageal spasm also developed. The remaining nine patients and the four volunteers did not experience chest pain, but all subjects except one had some symptomatic response to ergonovine, including chest warmth or heaviness, headache, mild choking sensation, facial numbness, flushing, or nausea. Two of the nine patients and one of the four volunteers developed manometric signs of esophageal spasm after ergonovine but experienced no chest pain. Intravenous ergonovine may be useful to identify esophageal spasm in selected patients with chest pain who have normal coronary arteries or in whom coronary artery disease is insufficient to explain symptoms. However, we believe that the potential risks of ergonovine do not justify its routine use as a provocative agent for esophageal spasm.