A novel method to produce extensive gastric antral ulcer in rats: pharmacological factors involved in the etiology of antral ulceration

Invited review: Abomasal damage in veal calves

Within all cattle production systems, veal calves are the most severely affected by abomasal damage, with current prevalence at slaughter ranging from 70 to 93% of all animals affected. Although most damage is found in the pyloric region of the abomasum, fundic lesions are also found. Despite past research into the etiology of abomasal damage and the many risk factors that have been proposed, consensus on the causal factors of abomasal damage in veal calves has not yet been reached. The aim of this review was to integrate and analyze available information on the etiology of, and possible risk factors for, abomasal damage in veal calves. We describe various proposed pathways through which risk factors may contribute to damage formation and conclude that the etiology of abomasal damage is most likely multifactorial, with diet being a main contributor. Pyloric lesions, the most common type of damage in veal calves, are likely the result of large and infrequent milk and solid feed meals, whereas fundic lesions may be caused by stress, although the evidence for this is inconclusive. Providing calves with multiple smaller milk and solid feed meals (or ad libitum provision) may decrease abomasal damage. In future research, ulcers, erosions, and scars as well as fundic and pyloric lesions should be recorded separately, because etiologies of these may differ. Further research is required to understand the exact pathway(s) by which milk replacer causes abomasal damage in veal calves; that is, whether low abomasal pH, overloading, or composition are important. Further research is also required to elucidate whether rapid intake of milk replacer and solid feed, which is influenced by restricted amounts fed, inter-calf competition, and calf breed, increases abomasal damage. Research is also needed into the effect of medication and nutrient deficiencies other than iron. The types of experimental designs that can be used for future research could be enhanced if a means to assess abomasal damage antemortem is developed. We conclude that it is unlikely that abomasal or ruminal hairballs, iron deficiency, water provision, and various infections and diseases are significant contributors to abomasal damage in veal calves.

Pathological quantification of experimental gastric ulcer in mice

AIM: To develop a method of quantifying the pathological changes gastric ulcer in the experimental mice.

METHODS: The experimental mice were fed with alcohol to establish the model of gastric ulcer. The area of the ulcer was quantified by weight and picture integration. Then the ratio of ulcer area to total stomach area (ulcer area ratio, UAR) was calculated to assess the degrees of the ulcers on the stomach wall. Furthermore, the methods of weighing, picture integration, marking, and grading were compared.

RESULTS: The mark indexes and the UAR by weight and picture integration were significantly different between different grading groups (Grade 4 vs Grade 2 vs Grade 1: 84.0±27.8 vs 19.6±8.1 vs 4.0±1.0, P<0.05; 40.74±0.26% vs 4.22±0.01%vs 1.03±0.01%, P<0.05; 31.57 ±0.16% vs 4.36±0.02% vs 2.43±0.02%, P<0.05) respectively, but the petechiae have no significant difference (P>0.05). Except in one mouse, the differences of UAR between by weight and picture integration in other five mice were 0.69, 4.89, 7.41, 1.26 and 2.76 respectively, which showed UAR had no marked difference between the two methods. In comparison of model I with model II, there were no obvious differences in the mark indexes, grading indexes and the numbers of petechiae while the UARs between by weight and picture integration were significantly different (6.14±0.08%vs 27.64±0.31%, P<0.05; 6.56±0.07% vs 21.22±0.21%, P<0.05).

CONCLUSION: The degrees of the gastric ulcer can be accessed by weight, picture integration, marking and grading. Weighing is better for measuring the ulcer over the fourth grade while picture integration can be used in all the degrees. The sensitivity and accuracy of picture integration and weighing are higher than those of traditional marking and grading.

Yogurt containing Lactobacillus gasseri OLL2716 exerts gastroprotective action against [correction of agaisnt] acute gastric lesion and antral ulcer in rats

Yogurt containing Lactobacillus gasseri OLL2716 (LG21 yogurt) is reported to improve Helicobacter pylori-induced gastric mucosal inflammation in clinical studies. However, other beneficial effects of LG21 yogurt have not been clarified. Therefore, we examined whether LG21 yogurt exhibits a gastroprotective action against acute gastric lesion or antral ulcer in rats. Moreover, the mechanism of gastroprotective action was also evaluated. After fasting, acute gastric lesions were induced by 0.6 M HCl. Gastric mucosal folds were stained by oral administration of methyl violet. Antral ulcers were induced by the combined administration of diethyldithiocarbamate and HCl in refed rats after fasting. LG21 yogurt was orally administered before HCl treatment or staining the mucosal folds. LG21 yogurt significantly and dose-dependently inhibited the formation of acute gastric lesions, and this gastroprotective action was attenuated by pretreatment with indomethacin. LG21 yogurt also significantly increased prostaglandin E2 generation in the gastric mucosa. Stained length of gastric mucosal fold was reduced by LG21 yogurt. Antral ulcer formation was also significantly inhibited by LG21 yogurt. From the above results, it was found that the ingestion of LG21 yogurt is useful for the prevention of gastric ulcer. Moreover, endogenous prostaglandin was suggested to be one of the gastroprotective mechanisms of LG21 yogurt.

[An overview of acetic acid ulcer models and their utility for drug screening]

Since Takagi et al. reported an experimental chronic gastric ulcer model [acetic acid ulcers induced by submucosal injection of acetic acid (Type 1)], we further modified the methodology and subsequently devised three more models. The second model involves inducing ulcers by serosal application of an acetic acid solution (Type 2) and the third model achieves ulcer induction by intragastric application of an acetic acid solution (Type 3). The forth model was modification of the third model by giving the acetic acid solution and the same volume of air to make one ulcer in the stomach (Type 4). In general, animals accepted the procedures without problems and no undesirable effects were noticed. More importantly, this experimental animal model allows production of ulcers that highly resemble human ulcers in terms of both pathology and healing. Indeed, relapse is even endoscopically observed for 360 days after ulceration. The ulcers produced not only respond well to various anti-ulcer medications, such as antisecretory and mucosal protective drugs and growth factors, but also demonstrate appropriate responses to ulcerogenic agents such as NSAIDs. In addition, we have recently demonstrated that H. pylori infection resulted in delayed ulcer healing and recurrence of healed acetic acid ulcers induced in Mongolian gerbils. The present article gives a brief summary of the ulcer history before establishment of acetic acid ulcers and characteristic features of acetic acid ulcer, including both their merits and shortcomings.

Role of acid back-diffusion, glutathione, oxyradical, and histamine in antral hemorrhagic ulcer in rats: the protective effect of lysozyme chloride and antioxidants

The pathogenesis of gastric antral hemorrhage and ulceration is unclear. This paper first proposes that antral hemorrhagic ulcers produced in rats are associated with attenuation of defensive parameters (such as mucosal glutathione levels and histamine release, as well as aggravation of aggressive factors) including gastric acid back-diffusion and oxyradical generation. The protective effects of lysozyme chloride and antioxidants on this ulcer model were also evaluated. After being deprived of food for 24 hours followed by refeeding for 1 hour, rats were injected with 1.0 mol HCl/L intragastrically under potent analgesia of diethylether-anesthesia to induce antral ulcer. Control rats received a normal saline solution only. Rats were then given free access to water and food for 4 days. Before the experiment began, rats were again deprived of food for 24 hours. Following anesthetization, their stomachs were irrigated for 3 hours with either normal saline or a physiological acid solution containing 100 mmol HCl/L and 54 mmol NaCl/L. Aggravation of various aggressive and defensive parameters in antral mucosa was observed in refed rats that had received 1.0 mol HCl/L. A high relationship of mucosal glutathione level (r = -0.8754, P <.05) or lipid peroxides generation (r = 0.8198) to antral ulceration was obtained in those ulcerated rats. Intragastric lysozyme chloride (50-200 mg/kg) injected three times daily produced a dose-dependent attenuation of various gastric parameters in the acid-irrigated stomachs of antral ulcer rats. Intraperitoneal injections of various antioxidants, including exogenous glutathione, allopurinol, or dimethylsulfoxide also attenuated antral ulcer. In conclusion, the imbalance of aggressive factors, such as acid back-diffusion and oxyradicals-as well as defensive factors including glutathione and histamine-is important in modulating antral hemorrhagic ulcers that can be ameliorated by lysozyme chloride or antioxidants in rats.

Effects of vanilloid receptor agonists and antagonists on gastric antral ulcers in rats

Defunctionalization of capsaicin-sensitive afferent nerves by pretreatment with a neurotoxic dose of capsaicin aggravates gastric ulcers in rats. In the present study, we investigated the roles of vanilloid receptors in gastric antral ulcers, using vanilloid receptor agonists and antagonists. Gastric antral ulcers were induced by a combination of diethyldithiocarbamate and 1 N HCl in refed rats. The administration of ruthenium red (1.5 mg/kg, s.c., twice daily) aggravated gastric antral ulcers (ulcer index: control, 33.7+/-13.7 mm(2); ruthenium red, 99.9+/-11.0 mm(2)). A similar result was observed in rats pretreated with a neurotoxic dose of capsaicin. On the other hand, capsaicin (1-10 mg/kg, p.o., twice daily) inhibited antral ulcer formation (ulcer index: control, 99.2+/-20.6 mm(2); capsaicin 10 mg/kg, 37.0+/-11.7 mm(2)). A similar effect was obtained in rats treated with the novel antiulcer drug, lafutidine (3-10 mg/kg, p.o., twice daily), which has gastroprotective activity mediated by capsaicin-sensitive afferent nerves. The antiulcer effects of capsaicin and lafutidine were abolished by ruthenium red and by pretreatment with a neurotoxic dose of capsaicin. These results suggest that vanilloid receptors play a gastroprotective role in gastric antral ulcers. In addition, treatment with ruthenium red may be an alternative tool for defunctionalization of capsaicin-sensitive afferent nerves.