Continuous versus intermittent acid exposure in production of esophagitis in feline model.

Our morphometric feline model of acid-induced esophageal damage histologically resembles human reflux esophagitis. The histologic scoring system includes intensity and linear extent of basal cell hyperplasia, intraepithelial and subepithelial segmented leukocytes, and ulcers. Each of these four categories is scored from 0 to 4, for a potential total score of 16. Some reports have indicated that the long-duration acid exposure episodes during recumbent nighttime reflux are apt to be associated with greater injury than shorter episodes during daytime upright exposure. We tested the hypothesis that longer single exposures to acid would incite greater morphologic damage in the cat than would multiple, shorter acid exposures. To study the influence of continuous versus intermittent hydrochloric acid exposure, groups of six cats each were infused continuously (single infusion) for 15, 20, or 30 min, and compared with cats infused for 2-min acid infusion times. Our studies indicate that total acid exposure and mucosal damage are more likely to be greater after multiple episodes of the same total duration with adequate clearing (ie, awake upright reflux) than after single long episodes of acid exposure that are poorly cleared (ie, sleeping).

Piroxicam decreases postirradiation colonic neoplasia in the rat.

This study evaluated the effects of the nonsteroidal antiinflammatory agent piroxicam on chronic radiation proctitis in the rat. Forty female Wistar rats received a 2250-cGy dose of irradiation to the distal 2 cm of the colon. Twenty received piroxicam 8.0 mg/kg orally 30 minutes before exposure and 24 hours after exposure; 20 rats served as irradiated controls. All animals were evaluated by colonoscopy 1 and 3 weeks postexposure and every third week until death or killing at 1 year. At killing, colons were removed for light microscopic examination. One year postirradiation results showed no differences in mortality, vascular changes, acute inflammation, colitis cystica profunda, or rectal stricture between the control and piroxicam-treated groups. However, at 1 year postirradiation the control group demonstrated neoplasia in 15 of 19 animals compared with eight of 20 animals in the piroxicam-treated group. The first endoscopic appearance of colonic neoplasm occurred at 15 weeks postirradiation in one control irradiated rat whereas the first evidence of endoscopic neoplasm in the piroxicam-treated group did not occur until 36 weeks postirradiation. Histologic examination documented a tendency toward a greater presence of adenocarcinomas in the control group compared with the piroxicam-treated group. The authors conclude that piroxicam treatment significantly decreased the incidence of colonic neoplasia in general as well as delayed the endoscopic appearance of colonic neoplasia in rats after pelvic irradiation.

The histologic development of acid-induced esophagitis in the cat.

Acute reflux esophagitis in man is characterized histologically by infiltrates of segmented leukocytes, epithelial proliferation, and ulcers. Our feline model, which includes each of these features, is produced by the infusion of 0.1 N HCl at a rate of 1 ml per min into the distal esophagus of adult cats for varying periods of time. Our histologic scoring system includes both the intensity and the distribution of four morphologic features, namely basal cell hyperplasia (BCH), intraepithelial segmented leukocytes (IEL), subepithelial leukocytes (SEL), and ulcers. Each of these four categories are scored from 0 to 4, with a potential score of 16. We evaluated the effects of duration of acid exposure by infusing cats with HCl for 5 min (N = 4), 15 min (N = 12), 20 min (N = 12), and 30 min (N = 6), followed by autopsy 24 h later. Mean scores (+/- SE) were as follows: 5 min, 3.0 (+/- 1.7); 15 min, 9.0 (+/- 1.0); 20 min, 11.17 (+/- 1.06); 30 min, 15.17 (+/- 0.54). Differences between 5 and 15 min, 15 and 30 min, and 20 and 30 min were significant (P less than 0.05). Basal cell hyperplasia appeared to be the most sensitive marker of acid injury; ulcers denoted severe injury associated with longer exposure periods. Although an occasional eosinophil was seen, the majority of the segmented leukocytes were neutrophils. We also studied healing histologically by examining cats at 1 d (N = 6), 2 d (N = 6), 3 d (N = 11), and 4 d (N = 6) after a 30 min exposure to HCl.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiation-induced proctitis cystica profunda in the rat.

Therapeutic pelvic irradiation is notorious for the production of clinically significant sequela after a long latency. One of the rarest of these complications is proctitis cystica profunda (PCP). To study the histologic changes of chronic radiation proctitis, we evaluated 35 female Wistar rats that had received a single exposure of 22.5 Gy of radiation to the rectum and were then followed for one year. We identified PCP and its precursor lesions in 18 rats. The fully developed lesion consisted of a focal expansion of the submucosa by dilated cystic spaces lined by a single layer of benign epithelial cells. Usually, PCP evolved as glands herniated between small defects in the muscularis mucosae. Mitotic figures were not recognized in the cells lining the herniating glands. In two rats, the radiation had apparently caused large ulcers, which had subsequently reepithelialized, resulting in prominent submucosal glandular tissue. Although the number of goblet cells in the displaced epithelium was reduced, the cells had rather mature appearances ultrastructurally. Glands displaced into the submucosa were encased by an intact basal lamina but lacked in muscularis.