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in Journal of the American Veterinary Medical Association

Abstract

Objective—To develop a protocol to induce and maintain gastric ulceration in horses and to determine whether gastric ulceration affects physiologic indices of performance during high-speed treadmill exercise.

Animals—20 healthy Thoroughbreds.

Procedures—Each horse was acclimatized to treadmill exercise during a 2-week period. Subsequently, baseline data were collected (day 0) and each horse began an incrementally increasing exercise training program (days 1 through 56). Beginning on day 14, horses were administered omeprazole (4 mg/kg, PO, q 24 h until day 56) or no drug (10 horses/group) and underwent alternating 24-hour periods of feeding and feed withholding for 10 days to induce gastric ulceration. Extent of gastric ulceration was assessed weekly thereafter via gastroscopy. Physiologic indices of performance were measured at days 0 and 56. Gastric ulceration and exercise performance indices were compared within and between groups.

Results—In untreated horses, gastric ulcers were induced and maintained through day 56. Gastric ulcer formation was prevented in omeprazole-treated horses. There were significant interactions between time (pre- and post-training data) and treatment (nonulcer and ulcer groups) for mass-specific maximal O2 consumption ( O 2max/Mb) and mass-specific maximal CO2 production ( CO 2max/Mb). Post hoc analysis revealed a difference between groups for O 2max/Mb at day 56. Within-group differences for O 2max/Mb and CO 2max/Mb were detected for omeprazole-treated horses, but not for the horses with ulcers.

Conclusions and Clinical Relevance—In horses, gastric ulcers were induced and maintained by use of alternating periods of feeding and feed withholding in association with treadmill exercise (simulated racetrack training). Gastric ulcers adversely affected physiologic indices of performance in horses.

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in American Journal of Veterinary Research

Objective

To characterize, in mares, changes in peritoneal fluid that occurred within the first 7 days after routine foaling.

Design

Prospective observational trial.

Animals

15 mares.

Procedure

Abdominocentesis was performed within 10 days before foaling and again 12 hours, 3 days, and 7 days after each horse foaled. Data recorded for each sample included total nucleated cell count, differential cell count, specific gravity, fibrinogen concentration, and total protein concentration. Smears of each sample were examined by a single clinical pathologist.

Results

There were not any significant differences over time in specific gravity, total protein concentration, fibrinogen concentration, total nucleated cell count, or number of small mononuclear cells. Mean numbers of neutrophils and large mononuclear cells in samples collected after foaling were significantly higher than mean numbers in samples collected before foaling. For 11 of 14 horses, all samples were characterized cytologically as transudates without cytologic abnormalities.

Clinical Implications

Results of analysis of peritoneal fluid from peripartum mares suggest that nucleated cell count, protein concentration, and specific gravity of peritoneal fluid from mares that have recently foaled should be normal. Thus, peritoneal fluid abnormalities detected in mares within a week after foaling should usually be attributed to a systemic or gastrointestinal problem and not to the foaling process itself. (J Am Vet Med Assoc 1996;209:1280–1282)

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in Journal of the American Veterinary Medical Association

Summary

Twenty-two horses were examined because of firearm injuries. Nine had been shot with .22- caliber bullets, 2 with BB pellets, 6 with buckshot, 1 with a, 35-caliber bullet, and 1 with an airgun pellet. Injury was confined to the skin or skeletal muscles in 8 horses. Of these, 7 returned to their previous use. In 14 horses, injuries to additional structures were incurred, including the sinus and pharynx (n = 2), mandible (n = 1), tooth (n = 1), aorta (n = 1), eye (n = 3), tibia (n = 1), gastrointestinal tract (n = 3), joint (n = 1), and trachea (n = 1). The 3 horses that had only eye injuries were discharged to their owners. Of the other 11 horses with injuries to deep/vital structures, 3 died, 5 were euthanatized, and 3 survived.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine efficacy of an extracorporeal circuit to maintain a segment of equine large colon for 3.5 hours and to evaluate the effect of low arterial flow on histologic and metabolic variables.

Sample Population—Segments of large colon from 15 healthy adult horses.

Procedure—The pelvic flexure was surgically removed and maintained in an isolated circuit. In the control group, tissue was evaluated for 3.5 hours, whereas in the low-flow group, arterial flow was reduced to 20% of baseline for 40 minutes followed by 2 hours of reperfusion. Various metabolic and hemodynamic variables were evaluated at 30-minute intervals. Effects of nitric oxide (NO) and L-N-nitro-arginine- methyl-ester (L-NAME) on contractile activity were determined, and histomorphologic evaluation was performed at the completion of the study.

Results—Low-flow ischemia with reperfusion caused significant histomorphologic differences, compared with the control group. In the low-flow group, significant differences included reduction in PaCO2, reduction in bicarbonate concentrations, increase in PaO2, and an increase in base deficit in arterial and venous blood samples. Other significant differences included increases in PCV, protein concentration, total WBC count, and albumin clearance for the low-flow group. Differences were not detected in inhibitory activity of the low-flow group relative to the control tissue with or without addition of NO and L-NAME.

Conclusion—The extracorporeal circuit maintained a segment of equine intestine for 3.5 hours and can be used to simulate ischemic injury. The extracorporeal circuit provides the potential to investigate pharmaceutic agents that can minimize intestinal injury. (Am J Vet Res 2000;61:1042–1051)

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in American Journal of Veterinary Research

Abstract

Objective—To use an extracorporeal circuit to evaluate effects of intraluminal distention on the jejunum of healthy horses.

Sample Population—2 jejunal segments from each of 5 horses.

Procedure—Jejunal segments were harvested and maintained in an extracorporeal circuit. One segment was subjected to distention (intraluminal pressure, 25 cm H2O) followed by decompression, and 1 segment was maintained without distention. The influence of distention-decompression on vascular resistance was calculated. Mucosal permeability was evaluated by measuring the clearance of albumin from blood to lumen. After distention and decompression, tissue specimens were collected for histomorphologic evaluation. In addition, the contractile response of the circular smooth muscle layer was determined following incubation with 3 prokinetic agents.

Results—Intestinal vascular resistance increased during intraluminal distention and returned to baseline values after decompression. Albumin clearance rate increased after distention, compared with baseline and control values. Histologic examination of the distended segments revealed grade-1 and -2 lesions of the mucosal villus. Edema and hemorrhage were evident in the submucosa and muscular layers. Mesothelial cell loss, edema, and hemorrhage were also evident in the serosa. Mucosal surface area and villus tip height decreased and submucosal volume increased in the distended tissue. Compared with responses in control specimens, distention decreased the contractile response induced by cisapride, erythromycin, and metoclopramide.

Conclusions and Clinical Relevance—Intraluminal distention of the jejunum followed by decompression increased mucosal permeability and injury and decreased responses to prokinetic agents. Horses with intraluminal intestinal distention may have a decreased response to prokinetic agents. (Am J Vet Res 2002;63:267–275)

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in American Journal of Veterinary Research

Objective

To determine the clinical outcome of horses treated for infection of the intertubercular bursa (infectious bicipital bursitis).

Design

Retrospective analysis of case records.

Animals

Four horses referred for treatment of infectious bicipital bursitis.

Procedure

Medical records of horses that were severely lame on admission were reviewed.

Results

In 3 horses, palpation over the bicipital bursa as well as flexion and extension of the scapulohumeral joint were resented. Ultrasonography performed in 1 horse revealed that the bicipital bursa was large and that excessive amounts of fluid containing hyperechoic material were evident within the bicipital bursa. Two horses were treated by the administration of antimicrobial and nonsteroidal antiinflammatory drugs. Both remained lame and failed to resume their former activity. Two horses additionally were treated surgically by means of a partial synovectomy. Both resumed their former activity although a subtle lameness remained in 1 horse.

Clinical Implications

Partial synovectomy may be useful in the treatment of horses with infectious bicipital bursitis. (J Am Vet Med Assoc 1996;208:1434-1437)

Free access
in Journal of the American Veterinary Medical Association

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

Summary

Sixteen horses were allotted at random to 3 groups: vehicle only; low dosage (vehicle and 3 mg of U-74389G/kg of body weight); high dosage (vehicle and 10 mg of U-74389G/kg). These solutions were given prior to reperfusion. The ascending colon was subjected to 2 hours of ischemia followed by 2 hours of reperfusion. Before, during, and after ischemia, full-thickness colonic tissue biopsy specimens were obtained for measurement of malondealdehyde (mda) concentration and myeloperoxidase activity and for morphologic evaluation.

Although increases were not significant, mda concentration and myeloperoxidase activity increased during ischemia and reperfusion. Administration of U-74389G did not have significant effects on mda concentration and myeloperoxidase activity. However, the lower dosage tended (P = 0.08) to reduce myeloperoxidase activity at 30 and 60 minutes of reperfusion.

In horses of the vehicle-only group, ischemia induced a decrease in mucosal surface area that was continued into the reperfusion period (P ≤ 0.05). Administration of U-74389G at both dosages (3 and 10 mg/kg) prevented the reperfusion-induced reduction in mucosal surface area, which was significant at 60 minutes (high dosage; P = 0.05) and 90 minutes (low and high dosages; P = 0.02). After initial reduction in horses of all groups, mucosal volume increased for the initial 60 minutes of reperfusion.

Our results indicate that lipid peroxidation may be partially involved in continued cellular death after ischemia of the ascending colon of horses. The 21-aminosteroid, U-74389G, prevented further loss of mucosa and partially attenuated the induced increase in myeloperoxidase activity during reperfusion of the ascending colon.

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