Objective: To determine the effects of clenbuterol, at a dosage of up to 3.2 μg/kg for 14 days, PO, on skeletal and cardiac muscle in healthy horses undergoing treadmill exercise. Animals: 12 healthy horses from 3 to 10 years old. Procedures: Horses were randomly assigned to a control group (n = 6) or clenbuterol group (6) and received either saline (0.9% NaCl) solution or clenbuterol, PO, every 12 hours for 14 days. Horses were subjected to submaximal treadmill exercise daily during treatment. Muscle biopsy specimens were collected before and after treatment for determination of apoptosis. Echocardiographic measurements, serum clenbuterol and cardiac troponin I concentrations, and serum activities of creatine kinase and aspartate aminotransferase were measured before, during, and after treatment. Jugular venous blood samples were collected every 3 days during treatment. Echocardiography was repeated every 7 days after beginning treatment. Response variables were compared between treatment groups and across time periods. Results: No significant effect of clenbuterol or exercise on response variables was found between treatment and control groups at any time point or within groups over time. Conclusions and Clinical Relevance: Results did not reveal any adverse effects of treatment with an approved dose of clenbuterol on equine cardiac or skeletal muscle in the small number of horses tested.

Objective: To compare results of single-point kinetic gait analysis (peak and impulse) with those of complete gait waveform analysis. Animals: 15 healthy adult mixed-breed dogs. Procedures: Dogs were trotted across 2 force platforms (velocity, 1.7 to 2.1 m/s; acceleration and deceleration, 0.5 m/s2). Five valid trials were recorded on each testing day. Testing days 1 and 2 were separated by 1 week, as were days 3 and 4. Testing days 1 and 2 were separated from days 3 and 4 by 1 year. A paired t test was performed to evaluate interday and interyear differences for vertical and craniocaudal propulsion peak forces and impulses. Vertical and craniocaudal propulsion force-time waveforms were similarly compared by use of generalized indicator function analysis (GIFA). Results: Vertical and craniocaudal propulsion peak forces and impulses did not differ significantly between days 1 and 2 or days 3 and 4. When data were compared between years, no significant differences were found for vertical impulse and craniocaudal propulsion peak force and impulse, but differences were detected for vertical peak force. The GIFA of the vertical and craniocaudal force-time waveforms identified significant interday and interyear differences. These results were identical for both hind limbs. Conclusions and Clinical Relevance: Findings indicated that when comparing kinetic data overtime, additional insight may be gleaned from GIFA of the complete waveform, particularly when subtle waveform differences are present.

Objective: To determine the effects of hypothyroidism on insulin sensitivity, glucose tolerance, and concentrations of hormones counter-regulatory to insulin in dogs. Animals: 8 anestrous mixed-breed bitches with experimentally induced hypothyroidism and 8 euthyroid control dogs. Procedures: The insulin-modified frequently sampled IV glucose tolerance test and minimal model analysis were used to determine basal plasma insulin and glucose concentrations, acute insulin response to glucose, insulin sensitivity, glucose effectiveness, and disposition index. Growth hormone response was assessed by stimulation and suppression tests. Additionally, basal serum growth hormone (GH) and insulin-like growth factor-1 (IGF-1) concentrations and urine cortisol-to-creatinine concentration ratios were measured and dual energy x-ray absorptiometry was performed to evaluate body composition. Results: Insulin sensitivity was lower in the hypothyroid group than in the euthyroid group, whereas acute insulin response to glucose was higher. Glucose effectiveness and disposition index were not different between groups. Basal serum GH and IGF-1 concentrations as well as abdominal fat content were high in hypothyroid dogs, but urine cortisol-to-creatinine concentration ratios were unchanged. Conclusions and Clinical Relevance: Hypothyroidism appeared to negatively affect glucose homeostasis by inducing insulin resistance, but overall glucose tolerance was maintained by increased insulin secretion in hypothyroid dogs. Possible factors affecting insulin sensitivity are high serum GH and IGF-1 concentrations and an increase in abdominal fat. In dogs with diseases involving impaired insulin secretion such as diabetes mellitus, concurrent hypothyroidism can have important clinical implications.

Objective: To assess the transmission of bovine viral diarrhea virus (BVDV) from experimentally infected white-tailed deer fawns to colostrum-deprived calves by use of a BVDV strain isolated from hunter-harvested white-tailed deer. Animals: 5 white-tailed deer (Odocoileus virginianus) fawns and 6 colostrum-deprived calves. Procedures: Fawns were inoculated intranasally with a noncytopathic BVDV-1a isolate (2 mL containing 10(6.7) TCID(50)/mL), and 2 days after inoculation, animals were commingled until the end of the study. Blood and serum samples were obtained on days −6, 0, 7, 14, and 21 after inoculation for reverse transcriptase PCR assay, virus neutralization, and BVDV-specific antibody ELISA. Nasal, oral, and rectal swab specimens were collected on days 0, 3, 7, 14, 17, and 21 for reverse transcriptase PCR testing. By 21 days after inoculation, all animals were euthanized and necropsied and tissues were collected for histologic evaluation, immunohistochemical analysis, and virus isolation. Results: All fawns became infected and shed the virus for up to 18 days as determined on the basis of reverse transcriptase PCR testing and virus isolation results. Evidence of BVDV infection as a result of cohabitation with acutely infected fawns was detected in 4 of the 6 calves by means of reverse transcriptase PCR testing and virus isolation. Conclusions and Clinical Relevance: On the basis of these findings, BVDV transmission from acutely infected fawns to colostrum-deprived calves appeared possible.

Objective: To immunohistochemically evaluate matrix metalloproteinase (MMP)-9 expression in benign and malignant mammary gland tumors (MMTs) in dogs and relate expression to prognostic factors and patient outcome. Animals: 118 female dogs with naturally occurring mammary gland tumors and 8 dogs without mammary gland tumors. Procedures: 24 benign mammary gland tumors and 94 MMTs (1/affected dog) were obtained during surgical treatment; control mammary gland tissue samples were collected from unaffected dogs after euthanasia for reasons unrelated to the study. Tumors were evaluated for proliferation, invasive growth, histologic grade, and metastatic capacity; expression of MMP-9 was determined immunohistochemically, and its relationship with clinical and histologic findings was investigated. For dogs with MMTs, follow-up continued for 2 years; data were used to compute overall survival time and disease-free interval and construct survival curves. Results: MMTs had significantly higher MMP-9 expression in stromal cells and in neo-plastic cells than did the benign neoplasms. Stromal MMP-9 expression was also higher in highly proliferative tumors and in tumors with invasive growth, high histologic grade, and metastatic capacity. Furthermore, tumors from patients with shorter overall survival times and disease-free intervals had higher expression of MMP-9 in stromal cells. Conclusions and Clinical Relevance: In dogs with MMTs, level of MMP-9 expression by stromal cells was related to factors of poor prognosis and shorter overall survival times and disease-free intervals. These results suggested that MMP-9 produced by tumor-adjacent stromal cells contributed to MMT progression in female dogs and that assessment of MMP-9 expression may be a valuable prognostic factor.

Objective: To determine reference values for kaolin-activated thromboelastography in echocardiographically normal cats. Animals: 30 healthy cats without evidence of cardiomyopathy on echocardiographic examination. Procedures: All cats underwent echocardiographic examination, the findings of which were reviewed by a board-certified cardiologist. Cats that struggled (n = 10) received mild sedation with butorphanol and midazolam IM to permit phlebotomy without interruption in jugular venous blood flow. Blood samples were collected for analysis of thromboelastography variables, PCV, total solids concentration, platelet count, activated partial thromboplastin time, prothrombin time, fibrinogen concentration, and antithrombin concentration. Results: All 4 thromboelastography variables had < 5% mean intra-assay variability. Mean values were as follows: reaction time, 4.3 minutes; clotting time, 1.6 minutes; α angle, 66.5°; and maximum amplitude, 56.4 mm. Compared with nonsedated cats, cats that required sedation had a significantly shorter clotting time and greater α angle, whereas reaction time and maximum amplitude were not significantly different. Conclusions and Clinical Relevance: Kaolin-activated thromboelastography was a reliable test with unremarkable intra-assay variability in echocardiographically normal cats. Sedation may affect certain thromboelastography variables, but the effect is unlikely to be clinically important. It remains unknown whether subclinical cardiomyopathy has a significant effect on thromboelastography variables in cats.

Objective: To identify cardiac mechanisms that contribute to adaptation to high altitudes in Tibetan antelope (Pantholops hodgsonii). Animals: 9 male Tibetan antelope and 10 male Tibetan sheep (Ovis aries). Procedures: Tibetan antelope and Tibetan sheep inhabiting a region with an altitude of 4,300 m were captured, and several cardiac variables were measured. Expression of genes for atrial natriuretic peptide, brain natriuretic peptide, and calcium-calmodulin–dependent protein kinase II δ was measured via real-time PCR assay. Results: Ratios of heart weight to body weight for Tibetan antelope were significantly greater than those of Tibetan sheep, but ratios of right-left ventricular weights were similar. Mean ± SD baseline heart rate (26.33 ± 6.15 beats/min) and systolic arterial blood pressure (97.75 ± 9.56 mm Hg) of antelope were significantly lower than those of sheep (34.20 ± 6.57 beats/min and 130.06 ± 17.79 mm Hg, respectively). The maximum rate of rise in ventricular pressure in antelope was similar to that in Tibetan sheep, but after exposure to air providing a fraction of inspired oxygen of 14.6% or 12.5% (ie, hypoxic conditions), the maximum rate of rise in ventricular pressure of the antelope increased significantly to 145.1% or 148.1%, respectively, whereas that of the sheep decreased to 68.4% or 70.5%, respectively. Gene expression of calcium-calmodulin–dependent protein kinase II δ and atrial natriuretic peptide, but not brain natriuretic peptide, in the left ventricle of the heart was significantly higher in antelope than in sheep. Conclusions and Clinical Relevance: Hearts of the Tibetan antelope in this study were well adapted to high-altitude hypoxia as shown by higher heart weight ratios, cardiac contractility in hypoxic conditions, and expression of key genes regulating cardiac contractility and cardiac hypertrophy, compared with values for Tibetan sheep.

Objective: To compare the pharmacokinetics of a novel bioadhesive gel formulation of midazolam after intranasal (IN) administration with that of midazolam solution after IN, IV, and rectal administration to dogs. Animals: 10 (5 males and 5 females) healthy adult Beagles. Procedures: Dogs were assigned to 4 treatment groups for a crossover study design. Initially, midazolam solution (5 mg/mL) was administered (0.2 mg/kg) IV to group 1, rectally to group 2, and IN to group 3; a 0.4% hydroxypropyl methylcellulose midazolam gel formulation (50 mg/mL) was administered (0.2 mg/kg, IN) to group 4. Each dog received all 4 treatments; there was a 7-day washout period between subsequent treatments. Blood samples were collected before and after midazolam administration. Plasma concentration of midazolam was determined by use of high-performance liquid chromatography. Results: The peak plasma concentration after IN administration of the gel formulation was significantly higher than that after IN and rectal administration of the solution. Mean ± SD time to peak concentration was 11.70 ± 2.63 minutes (gel IN), 17.50 ± 2.64 minutes (solution IN), and 39 ± 14.49 minutes (solution rectally). Mean bioavailability of midazolam was 70.4% (gel IN), 52.0% (solution IN), and 49.0% (solution rectally). Bioavailability after IN administration of the gel formulation was significantly higher than that after IN and rectal administration of the solution. Conclusions and Clinical Relevance: IN administration of midazolam gel was superior to both IN and rectal administration of midazolam solution with respect to peak plasma concentration and bioavailability.

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.

Objective: To measure the effect of induced myopia on field trial performance in dogs. Animals: 7 Labrador Retrievers and 1 Chesapeake Bay Retriever trained in field trial competition. Procedures: Dogs were commanded to retrieve targets at 137.2 m (150 yards). Each dog participated in 3 trials while their eyes were fitted with 0- (plano), +1.50-, or +3.00-diopter (D) contact lenses, applied in random order. Retrieval times were measured objectively, and dog performances were evaluated subjectively by masked judges. Results: Retrieval times were significantly faster with plano lenses than with +1.50- or +3.00-D lenses, but there were no significant differences in times between +1.50- and +3.00-D lenses. Masked judges assigned the best performance scores to dogs with plano lenses and the lowest scores to dogs fitted with +3.00-D lenses. Conclusions and Clinical Relevance: Even mild myopic defocusing had a significant negative impact on both the subjective and objective assessments of dogs' performances. Dogs with demanding visual tasks or signs of visual deterioration should be evaluated retinoscopically to determine the refractive state because they may have ametropia.