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Abstract

Objective—To determine effects of leukotriene (LT) C4 on ion transport across equine tracheal epithelium.

Sample—Tracheal epithelium from cadavers of 24 horses considered free of respiratory tract disease.

Procedures—Mucosae were mounted into Ussing chambers, and short-circuit current (Isc) was monitored over time. Effects of LTC4 were examined for various conditions, including addition of amiloride (10μM) to the mucosal bath solution, addition of bumetanide (10μM) to the serosal bath solution, addition of barium (1mM) to the serosal bath solution, and substitution of gluconate for chloride and HEPES for bicarbonate in bath solutions. Electrolyte transport was assessed via 22Na and 36Cl isotope fluxes.

Results—Addition of LTC4 (50nM) to the serosal bath solution caused an increase in Isc for basal conditions and a larger increase after pretreatment with amiloride. The increase was negated in part by the addition of bumetanide to the serosal bath solution and further reduced by substitution of HEPES for bicarbonate in bath solutions. Remaining current was reduced to values less than those before treatment with LTC4 by the addition of barium to the serosal solution. There was a small increase in Isc after the addition of amiloride and substitution of gluconate for chloride. Radioisotope flux indicated that addition of LTC4 to the serosal bath solution increased chloride secretion and reduced sodium absorption.

Conclusions and Clinical Relevance—LTC4 stimulated chloride secretion through a predominately bumetanide-sensitive pathway, with a smaller contribution from a bicarbonate-dependent pathway. Thus, LTC4 appears to be a potential mediator of airway hypersecretion in horses.

Full access
in American Journal of Veterinary Research

Abstract

Objectives

To examine effect of pre-exercise administration of furosemide (FUR) on mean pulmonary arterial pressure (PAP) during work and RBC concentration in bronchoalveolar lavage fluid (BALF) collected 40 minutes after exercise.

Animals

10 adult Thoroughbreds.

Procedure

A modified 10 × 10 crossover design comprising 10 horses during 10 weeks was used. Each horse received each of 5 treatments twice. Treatment structure included a control plus a 2 × 2 factorial and consisted of the following: A, control; B, FUR, 250 mg, IV, 30 minutes before exercise; C, FUR, 250 mg, IV, 240 minutes before exercise; D, FUR, 250 mg, nebulized, 30 minutes before exercise; and E, FUR, 250 mg, nebulized, 240 minutes before exercise. Mean PAP data were collected, and each horse, after a 500-m warm-up, was galloped at maximal speed for 1,600 m. BALF RBC concentration was determined by hemocytometer.

Results

Interaction between treatment method and time of administration was significant (P = 0.04). Treatment B resulted in significantly (P = 0.01) lower BALF RBC concentration than did treatment C. Only BALF RBC count after treatment B was significantly lower than the control value. Horses that received FUR IV had significantly lower peak mean PAP than did those that received the drug by nebulization, regardless of administration time. Only treatment B resulted in peak mean PAP that was significantly lower than that of control. Exercise time was not influenced by treatment.

Conclusions

FUR, administered IV 30 minutes before exercise, significantly reduced peak mean PAP and BALF RBC concentration. (Am J Vet Res 1999; 60:22–28)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effects of a dose of caffeine (2.5 mg/kg, IV) administered to physically fit Thoroughbreds during incremental exercise testing to fatigue on a treadmill.

Animals—10 conditioned Thoroughbreds.

Procedure—Horses were randomly assigned to receive caffeine or a control solution. Each horse received both treatments in a crossover design with a 3-week interval between treatments. Each horse was administered caffeine (2.5 mg/kg) or an equivalent amount of a control solution IV. One hour after injection, each horse performed an incremental exercise test to exhaustion. Hematologic values, heart rate, oxygen consumption, carbon dioxide production, plasma lactate concentration, urine and serum concentrations of caffeine and metabolites, and time until exhaustion were monitored. Statistical analysis was performed by use of a mixed-effects linear model.

Results—Significant differences in measured values when horses were treated with caffeine or the control solution were not detected.

Conclusions and Clinical Relevance—A dose of caffeine (2.5 mg/kg, IV) appears to have no effect on any performance variable of physically fit Thoroughbreds during incremental exercise testing to fatigue. (Am J Vet Res 2005;66:569–573)

Full access
in American Journal of Veterinary Research

Abstract

Objective

To determine effect of xylazine hydrochloride (XYL), yohimbine hydrochloride (YOH), bethanechol chloride (BET), neostigmine methyl sulfate (NEO), or flunixin meglumine (FLU) on ileocecocolic myoelectric activity and passage of radiolabeled markers from the cecum.

Animals

6 healthy adult ponies.

Procedure

A cecal cannula was surgically implanted, and 12 were sutured to the ileum, cecum, and right ventral colon. After a 12-hour nonfeeding period, 370 MBq of technetium 99m-labeled sulfur colloid in egg albumen and 37 MBq of indium 111-labeled diethyltriaminepentaacetic acid in 60 ml of water were injected into the cecal apex. All drugs were administered IV as a bolus, with the exception of NEO, which was given SC: XYL, 0.5 mg/kg of body weight; YOH, 0.075 mg/kg; BET, 0.025 mg/kg; NEO, 0.025 mg/kg; FLU, 1.1 mg/kg; and saline solution (SAL), 10 ml. Drugs were administered in a randomized complete block design, each treatment was administered twice to each pony, and dual-phase scintigraphic images were obtained. The time to 50% emptying (t50) and the slope of the emptying curve (β) were derived from the calculated power exponential equation.

Results

The t50 after BET (184.8 ± 16.5 minutes) and NEO (124.7 ± 16.5 minutes) administration were significantly shorter than values after saline (230.2 ± 17.1 minutes) administration. The t50 after XYL administration (250.5 ± 18.6 minutes) was longer, and that after YOH administration (190.1 ± 16.2 minutes) was shorter, than the t50 after saline administration, but neither difference was significant. The t50 and β after FLU administration differed from those after saline administration. Myoelectric data appeared to be well correlated with drug-induced alterations in isotope clearance.

Conclusions and Clinical Relevance

Cholinergic agonists, BET and NEO, have significant effects on the myoelectric activity of ileum, cecum, and right ventral colon, with the net effect of hastening cecal emptying. (Am J Vet Res 1998;59:320–327)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine the effect of erythromycin lactobionate (ERY) on ileocecocolic myoelectric activity and passage of radiolabeled markers from the cecum.

Animals

6 healthy adult ponies.

Procedure

After a 12-hour nonfeeding period, 370 MBq of technetium 99m-labeled sulfur colloid in egg albumen and 37 MBq of indium 111-labeled diethyltriaminepentaacetic acid in 60 ml of water were administered directly into the cecal apex. The following drug concentrations were tested: ERY, 0.01, 0.10, 1.0, and 10.0 mg/kg of body weight; ERY, 0.10 mg/kg bolus; and saline (0.9% NaCl) solution, 10 ml. All treatments, with the exception of the 0.10-mg/kg bolus and saline solution, were infusions administered IV during a 60-minute period in a randomized complete block design. Each treatment was administered 2 times/pony. Dual-phase scintigraphic images were obtained, and the best-fit function was determined for each study, using data from the right side. Myoelectric data were collected before and after each treatment and analyzed for spike burst rate, relative activity, and burst duration.

Results

The time to 50% emptying (t50) after ERY administration was dose dependent, and all treatments, with the exception of the 0.01-mg/kg infusion, resulted in a significantly shorter t50 than that observed after saline administration (230.2 ± 17.12 minutes). The shortest t50 was observed after the 1.0 mg/kg dosage of ERY (76.9 ± 22.0 minutes). Although not significantly different, the t50 and β were shorter (108.6 ± 25.9 minutes) and steeper after a bolus dose of 0.10 mg/kg of ERY than after infusion at the same dosage (131.1 ± 18.7 minutes).

Conclusions and Clinical Relevance

ERY may be a useful prokinetic for prevention or treatment of cecal motility dysfunction. The ability of ERY to evoke a similar response during the early postanesthetic or postoperative period remains to be determined. (Am J Vet Res 1998;59:328–334)

Free access
in American Journal of Veterinary Research

Summary

Effects of a change from a diet composed primarily of forage to a diet composed primarily of concentrate on abomasal antral and duodenal motility were assessed in 5 lactating Holstein cows. Antroduodenal motility was measured by use of 8 silver electrodes sutured to the abomasum and duodenum, and abomasal emptying was assessed by continuous measurement of intraduodenal pH. Both diets were fed to achieve a daily dry matter intake of 2.7 kg/100 kg of body weight. The abrupt change in diet did not alter antroduodenal myoelectric activity or abomasal emptying. Initiation of phase III of the migrating myoelectric complex in the proximal portion of the duodenum corresponded with a decrease in abomasal antral spiking activity and an increase in intraduodenal pH. Results suggest that a high concentrate diet alone does not adversely affect antroduodenal motility in adult dairy cattle.

Free access
in American Journal of Veterinary Research

Summary

Thirty-five newborn foals were assigned to 1 of 3 groups and treated with 0.9% NaCl solution (saline; group 1; n = 12), oxytetracycline (44 mg/kg of body weight; group 2; n = 12), or 2-pyrrolidone (oxytetracycline vehicle; group 3; n = 11) in saline solution during the first 36 hours after birth. Serum biochemical analyses were performed on samples obtained from group-1 and group-2 foals before treatment and 24 and 96 hours after treatment. Lateral to medial radiographic views of the forelimbs were obtained before treatment and 24 and 96 hours after treatment in all foals. Metacarpophalangeal and distal interphalangeal joint angles were measured from the radiographic images. Significant changes in blood chemistry values, other than those typically observed in newborn foals, were not detected. A significant decrease in mean metacarpophalangeal joint angle was observed in foals 24 hours after treatment with oxytetracycline, compared with that in foals of groups 1 and 3. The mean metacarpophalangeal joint angle returned to pretreatment values by 96 hours. Oxytetracycline appears to be an effective method for obtaining a short-term moderate decrease in metacarpophalangeal joint angle in newborn foals.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objectives

To determine normal cecal emptying curves for liquid- and solid-phase radiolabeled markers and to further define myoelectric patterns of the ileum, cecum, and colon in healthy ponies.

Animals

6 adult ponies.

Procedure

A cecal cannula and 12 bipolar Ag-AgCl recording electrodes were sutured to the ileum, cecum, and right ventral colon of the ponies. Radioisotopes, indium 111-labeled diethyltriaminepentaacetic acid (111In-DTPA) and technetium 99m (99mTc)-labeled sulfur colloid bound to egg albumen, were introduced through the cannula directly into the cecal body. Movement of these markers from the cecum was monitored by a gamma camera, and power exponential clearance curves were generated. Myoelectric data were collected before and after IV administration of isotonic saline (0.9% NaCl) solution, and were analyzed for spike burst (SB) rate, relative activity index, and mean burst duration. Myoelectric complexes were identified from observation of chart recordings or compressed, digitized data.

Results

Clearance curves were generated for liquid (111In-DTPA)- and solid (99mTc)-phase markers. Marker types were not different with respect to lag phase, but liquid markers emptied at a slightly faster rate than did solids. Baseline values were calculated after saline solution administration for each of the myoelectric variables investigated. A relation between ileal, cecal, and colonic myoelectric activity was identified. Activity consistent with the previously described colonic migrating myoelectric complex in the pelvic flexure was identified in the right ventral colon.

Conclusions and Clinical Relevance

Baseline data on normal cecal emptying was obtained; this technique could be used to evaluate the effect of postulated motility-modifying treatments used in equine practice. (Am J Vet Res 1998;59:313–319)

Free access
in American Journal of Veterinary Research