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Abstract

Objective

To determine whether xanthine oxidase and dehydrogenase activities are altered during low flow ischemia and reperfusion of the small intestine of horses.

Animals

5 clinically normal horses without histories of abdominal problems.

Procedure

With the horse under general anesthesia, a laparotomy was performed and blood flow to a segment of the distal jejunum was reduced to 20% of baseline for 120 minutes and was then reperfused for 120 minutes. Biopsy specimens were obtained before, during, and after ischemia for determination of xanthine oxidase and dehydrogenase activities, and for histologic and morphometric analyses.

Results

Percentage of xanthine oxidase activity (as a percentage of xanthine oxidase and dehydrogenase activity) was not altered during ischemia and reperfusion. An inflammatory response developed and progressed during ischemia and reperfusion. Mucosal lesions increased in severity after ischemia and reperfusion. Mucosal surface area and volume decreased during ischemia and continued to decrease during reperfusion. Submucosal volume increased slightly during ischemia, and continued to increase during reperfusion.

Conclusions and Clinical Relevance

Evidence for conversion of xanthine dehydrogenase to xanthine oxidase during ischemia was not found. Factors other than production of reactive oxygen metabolites may be responsible for progressive epithelial loss, decrease in mucosal surface area and volume, and increase in submucosal volume observed in this study. Other methods of determining xanthine oxidase activity that detect the enzyme in sloughed epithelial cells should be used to better define the importance of this pathway in jejunal reperfusion injury in horses. (Am J Vet Res 1998;59:772-776)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine the effects of the 21-amino-steroid, U-74389G, on reperfusion of the equine jejunum, using total (TVO) and partial (PVO) vascular occlusion during the ischemic period.

Design

TVO: 16 healthy horses were randomly allotted to 3 groups—4 horses received the vehicle alone, 6 horses received a low dosage (3 mg/kg of body weight), and 6 horses a high dosage (10 mg/kg) of U-74389G. PVO: 10 healthy horses were randomly allotted to 2 groups—5 horses received the vehicle alone, and 5 horses received the low dosage (3 mg/kg) of U-74389G.

Procedure

TVO was induced for 1 hour followed by 2 hours of reperfusion. During PVO, blood flow was reduced to 20% of baseline for 2 hours, followed by 2 hours of reperfusion.

For both models, either the vehicle alone or the drug was given 15 minutes prior to reperfusion. Samples were obtained before, during, and after ischemia for determination of myeloperoxidase (MPO) activity, malondealdehyde (MDA) concentration, concentration of conjugated dienes (PVO experiment only), and morphometric analysis.

Results

TVO: tissue concentration of MDA and MPO activity were not altered in any group by ischemia or reperfusion. During ischemia, mucosal volume and surface area were reduced. After reperfusion, no further reduction occurred. After initial decrease in submucosal volume during ischemia, there was a significant increase after reperfusion in the vehicle-only group (P < 0.05). PVO: there were no alterations in the concentration of either MDA or conjugated dienes. There was a significant increase in the activity of MPO during ischemia and reperfusion (P< 0.05). These effects were similar for the vehicle-only and drug groups. During ischemia, there was a significant decrease in mucosal surface area and volume (P< 0.05), that was continued during reperfusion for the vehicle-only group (P< 0.05). Submucosal volume increased during reperfusion (P< 0.05). Serosal volume was increased during ischemia and reperfusion.

Conclusions and Clinical Relevance

Reduced blood flow during ischemia (PVO group) caused continued loss in mucosal volume and surface area during reperfusion. At the dosage given, the 21-aminosteroid, U-74389G, was not effective in preventing continued reduction in mucosal volume and surface area after restoration of blood supply in the horses subjected to reduced blood flow. (Am J Vet Res 1996; 57:762–770)

Free access
in American Journal of Veterinary Research