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A 19-year-old 555-kg (1,221-lb) warmblood gelding was evaluated because of poor performance and an irregular heart rhythm. The gelding was used as a jumper and had exercise intolerance of 1 week's duration. On evaluation, cardiac auscultation revealed a high heart rate (60 beats/min) with an irregularly irregular rhythm. No heart murmurs were detected via auscultation. The quality of the mandibular arterial pulses was considered normal. Irregular jugular venous pulsation was evident in the distal third of the jugular groove. Results of a CBC and serum biochemical analysis were unremarkable. A base-apex ECG examination revealed that the heart rate ranged from

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To compare effects of oxytocin, acepromazine maleate, xylazine hydrochloride-butorphanol tartrate, guaifenesin, and detomidine hydrochloride on esophageal manometric pressure in horses.

Animals—8 healthy adult horses.

Procedure—A nasogastric tube, modified with 3 polyethylene tubes that exited at the postpharyngeal area, thoracic inlet, and distal portion of the esophagus, was fitted for each horse. Amplitude, duration, and rate of propagation of pressure waveforms induced by swallows were measured at 5, 10, 20, 30, and 40 minutes after administration of oxytocin, detomidine, acepromazine, xylazine-butorphanol, guaifenesin, or saline (0.9% NaCl) solution. Number of spontaneous swallows, spontaneous events (contractions that occurred in the absence of a swallow stimulus), and high-pressure events (sustained increases in baseline pressure of > 10 mm Hg) were compared before and after drug administration.

Results—At 5 minutes after administration, detomidine increased waveform amplitude and decreased waveform duration at the thoracic inlet. At 10 minutes after administration, detomidine increased waveform duration at the thoracic inlet. Acepromazine administration increased the number of spontaneous events at the thoracic inlet and distal portion of the esophagus. Acepromazine and detomidine administration increased the number of high-pressure events at the thoracic inlet. Guaifenesin administration increased the number of spontaneous events at the thoracic inlet. Xylazine-butorphanol, detomidine, acepromazine, and guaifenesin administration decreased the number of spontaneous swallows.

Conclusions and Clinical Relevance—Detomidine, acepromazine, and a combination of xylazine butorphanol had the greatest effect on esophageal motility when evaluated manometrically. Reduction in spontaneous swallowing and changes in normal, coordinated peristaltic activity are the most clinically relevant effects. (Am J Vet Res 2002;63:1738–1744)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To characterize the in vitro effects of oxytocin, acepromazine, xylazine, butorphanol, detomidine, dantrolene, isoproterenol, and terbutaline on skeletal and smooth muscle from the equine esophagus.

Animals—14 adult horses without digestive tract disease.

Procedure—Circular and longitudinal strips from the skeletal and smooth muscle of the esophagus were suspended in tissue baths, connected to force-displacement transducers interfaced with a physiograph, and electrical field stimulation was applied. Cumulative concentration-response curves were generated for oxytocin, acepromazine, xylazine, detomidine, butorphanol, isoproterenol, terbutaline, and dantrolene. Mean maximum twitch amplitude for 3 contractions/min was recorded and compared with predrug-vehicle values for the skeletal muscle segments, and area under the curve (AUC) for 3 contractions/min was compared with predrug-vehicle values for the smooth muscle segments.

Results—No drugs caused a significant change in skeletal muscle response. In smooth muscle, isoproterenol, terbutaline, and oxytocin significantly reduced AUC in a concentration-dependent manner. Maximum reduction in AUC was 69% at 10–4M for isoproterenol, 63% at 10–5M for terbutaline, and 64% at 10–4M for oxytocin.

Conclusions and Clinical Relevance—Isoproterenol, terbutaline, and oxytocin cause relaxation of the smooth muscle portion of the esophagus. The clinical relaxant effects on the proximal portion of the esophagus reported of drugs such as oxytocin, detomidine, and acepromazine may be the result of centrally mediated mechanisms. (Am J Vet Res 2002;63:1732–1737)

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To evaluate optimal isolation of endothelial colony-forming cells (ECFCs) from peripheral blood of horses.

SAMPLE Jugular and cephalic venous blood samples from 17 adult horses.

PROCEDURES Each blood sample was divided; isolation was performed with whole blood adherence (WBA) and density gradient centrifugation (DGC). Isolated cells were characterized by uptake of 1,1’-dioctadecyl-3,3,3’,3’-tetramethylindocarbocyanine perchlorate–labeled acetylated low-density lipoprotein (DiI-Ac-LDL), vascular tubule formation, and expression of endothelial (CD34, CD105, vascular endothelial growth factor receptor-2, and von Willebrand factor) and hematopoietic (CD14) cell markers by use of indirect immunofluorescence assay (IFA) and flow cytometry.

RESULTS Colonies with cobblestone morphology were isolated from 15 of 17 horses. Blood collected from the cephalic vein yielded colonies significantly more often (14/17 horses) than did blood collected from the jugular vein (8/17 horses). Of 14 cephalic blood samples with colonies, 13 were obtained with DGC and 8 with WBA. Of 8 jugular blood samples with colonies, 8 were obtained with DGC and 4 with WBA. Colony frequency (colonies per milliliter of blood) was significantly higher for cephalic blood samples and samples isolated with DGC. Cells formed vascular tubules, had uptake of DiI-Ac-LDL, and expressed endothelial markers by use of IFA and flow cytometry, which confirmed their identity as ECFCs.

CONCLUSIONS AND CLINICAL RELEVANCE Maximum yield of ECFCs was obtained for blood samples collected from both the jugular and cephalic veins and use of DGC to isolate cells. Consistent yield of ECFCs from peripheral blood of horses will enable studies to evaluate diagnostic and therapeutic uses.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the isometric responses of isolated intrapulmonary bronchioles from cats with and without adult heartworm infection.

Animals—13 purpose-bred adult cats.

Procedures—Cats were infected with 100 third-stage larvae or received a sham inoculation, and the left caudal lung lobe was collected 278 to 299 days after infection. Isometric responses of intrapulmonary bronchiolar rings were studied by use of a wire myograph. Three cycles of contractions induced by administration of 10μM acetylcholine were followed by administration of the contractile agonists acetylcholine, histamine, and 5-hydroxy-tryptamine. To evaluate relaxation, intrapulmonary bronchiolar rings were constricted by administration of 10μM 5-hydroxytryptamine, and concentration-response curves were generated from administration of sodium nitroprusside, isoproterenol, and substance P.

Results—Compared with tissues from control cats, contractile responses to acetylcholine and 5-hydroxytryptamine were reduced in tissues from heartworm-infected cats. Relaxation to isoproterenol was significantly reduced in tissues from heartworm-infected cats. Relaxation to substance P was increased in tissues from heartworm-infected cats, but relaxation to sodium nitroprusside was unchanged.

Conclusions and Clinical Relevance—Results suggested that despite increased bronchiolar wall thickness in heartworm-infected cats, a hyperreactive response of the bronchiolar smooth muscle is not the primary mechanism of respiratory tract clinical signs. Reduced response of the airway to isoproterenol may indicate refractoriness to bronchiolar relaxation in heartworm-infected cats.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To investigate the effects of recombinant equine IL-1β on function of equine endothelial colony-forming cells (ECFCs) in vitro.

SAMPLE

ECFCs derived from peripheral blood samples of 3 healthy adult geldings.

PROCEDURES

Function testing was performed to assess in vitro wound healing, tubule formation, cell adhesion, and uptake of 1,1′-dioctadecyl-3,3,3′,3′ tetramethylindocarbocyanine perchlorate–labeled acetylated low-density lipoprotein (DiI-Ac-LDL) by cultured ECFCs. Cell proliferation was determined by 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide assay. Effects on function test results of different concentrations and exposure times of recombinant equine IL-1β were assessed.

RESULTS

Challenge of cultured ECFCs with IL-1β for 48 hours inhibited tubule formation. Continuous challenge (54 hours) with IL-1β in the wound healing assay reduced gap closure. The IL-1β exposure did not significantly affect ECFC adhesion, DiI-Ac-LDL uptake, or ECFC proliferation.

CONCLUSIONS AND CLINICAL RELEVANCE

These results suggested a role for IL-1β in the inhibition of ECFC function in vitro. Functional changes in ECFCs following challenge with IL-1β did not appear to be due to changes in cell proliferative capacity. These findings have implications for designing microenvironments for and optimizing therapeutic effects of ECFCs used to treat ischemic diseases in horses.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To isolate and characterize endothelial colony-forming cells (ECFCs; a subtype of endothelial progenitor cells) from peripheral blood samples of horses.

SAMPLE Jugular venous blood samples from 24 adult horses.

PROCEDURES Blood samples were cultured in endothelial cell growth medium. Isolated ECFCs were characterized by use of functional assays of fluorescence-labeled acetylated low-density lipoprotein (DiI-Ac-LDL) uptake and vascular tubule formation in vitro. Expression of endothelial (CD34, CD105, vascular endothelial growth factor receptor 2, and von Willebrand factor) and hematopoietic (CD14) cell markers was assessed through indirect immunofluorescence assay and flow cytometry. The number of passages before senescence was determined through serial evaluation of DiI-Ac-LDL uptake, vascular tubule formation, and cell doubling rates.

RESULTS Samples from 3 horses produced colonies at 12 ± 2.5 days with characteristic endothelial single layer cobblestone morphology and substantial outgrowth on expansion. Equine ECFCs formed vascular tubules in vitro and had uptake of DiI-Ac-LDL (74.9 ± 14.7% positive cells). Tubule formation and DiI-Ac-LDL uptake diminished by passage 5. Equine ECFCs tested positive for von Willebrand factor, vascular endothelial growth factor receptor 2, CD34, and CD105 with an immunofluorescence assay and for CD14 and CD105 via flow cytometry.

CONCLUSIONS AND CLINICAL RELEVANCE ECFCs can be isolated from peripheral blood of horses and have characteristics similar to those described for other species. These cells may have potential therapeutic use in equine diseases associated with ischemia or delayed vascularization.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To characterize adiponectin protein complexes in lean and obese horses.

Animals—26 lean horses and 18 obese horses.

Procedures—Body condition score (BCS) and serum insulin activity were measured for each horse. Denaturing and native western blot analyses were used to evaluate adiponectin complexes in serum. A human ELISA kit was validated and used to quantify high–molecular weight (HMW) complexes. Correlations between variables were made, and HMW values were compared between groups.

Results—Adiponectin was present as a multimer consisting of HMW (> 720-kDa), low-molecular weight (180-kDa), and trimeric (90-kDa) complexes in serum. All complexes were qualitatively reduced in obese horses versus lean horses, but the percentage of complexes < 250 kDa was higher in obese versus lean horses. High–molecular weight adiponectin concentration measured via ELISA was negatively correlated with serum insulin activity and BCS and was lower in obese horses (mean ± SD, 3.6 ± 3.9 μg/mL), compared with lean horses (8.0 ± 4.6 μg/mL).

Conclusions and Clinical Relevance—HMW adiponectin is measurable via ELISA, and concentration is negatively correlated with BCS and serum insulin activity in horses. A greater understanding of the role of adiponectin in equine metabolism will provide insight into the pathophysiology of metabolic disease conditions.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To describe misoprostol pharmacokinetics and anti-inflammatory efficacy when administered orally or per rectum in endotoxin-challenged horses.

ANIMALS

6 healthy geldings.

PROCEDURES

A randomized 3-treatment crossover design was performed with a minimum washout period of 28 days between treatment arms. Prior to endotoxin challenge (lipopolysaccharide, 30 ng/kg IV over 30 minutes), horses received misoprostol (5 µg/kg once) per os (M-PO) or per rectum (M-PR) or water as control (CON). Clinical parameters were evaluated and blood samples obtained to measure plasma misoprostol free acid concentration, leukocyte counts, and tumor necrosis factor-α (TNFα) and interleukin 6 (IL-6) leukocyte gene expression and serum concentrations.

RESULTS

In the M-PO treatment arm, maximum plasma concentration and area under the concentration-versus-time curve (mean ± SD) were higher (5,209 ± 3,487 pg/mL and 17,998,254 ± 13,194,420 h·pg/mL, respectively) and median (interquartile range) time to maximum concentration (25 min [18 to 34 min]) was longer than in the M-PR treatment arm (854 ± 855 pg/mL; 644,960 ± 558,866 h·pg/mL; 3 min [3 to 3.5 min]). Significant differences in clinical parameters, leukocyte counts, and TNFα or IL-6 gene expression or serum protein concentration were not detected. Downregulation of relative gene expression was appreciated for individual horses in the M-PO and M-PR treatment arms at select time points.

CLINICAL RELEVANCE

Considerable variability in measured parameters was detected among horses within and between treatment arms. Misoprostol absorption and systemic exposure after PO administration differed from previous reports in horses not administered LPS. Investigation of multidose administration of misoprostol is warranted to better evaluate efficacy as an anti-inflammatory therapeutic.

Open access
in American Journal of Veterinary Research