Objective—To evaluate the effect of multiple hydrogen peroxide gas plasma (HPGP) sterilizations on the rate of closure of ameroid constrictors. Sample—Thirty-six 5.0-mm ameroid constrictors. Procedures—Ameroid constrictors were randomly allocated to 6 groups. Each group underwent 1, 2, 3, 4, 5, or 6 HPGP sterilizations. Ameroid constrictors were then incubated for 35 days in canine plasma and digitally imaged at predetermined times during incubation. One individual, who was unaware of the group to which each ameroid constrictor was assigned, measured the lumen area of the constrictor on each digital image. Mean lumen area was compared among groups. Results—No ameroid constrictors were completely closed after 35 days of incubation in canine plasma. Mean lumen area after incubation did not differ among constrictors that underwent 1, 2, and 3 sterilizations. Constrictors that underwent 4 sterilizations were closed significantly more than were those that underwent 1, 2, or 3 sterilizations. Mean lumen area after incubation did not differ significantly between constrictors that underwent 5 and 6 sterilizations, although the final lumen areas for those constrictors were significantly smaller than those for constrictors that underwent 1, 2, 3, and 4 sterilizations. Conclusions and Clinical Relevance—Ameroid constrictors that underwent 5 and 6 HPGP sterilizations had a 9% to 12% decrease in lumen area, compared with that of constrictors that underwent ≤ 4 plasma sterilizations, and the use of such constrictors could increase the risk of portal hypertension and secondary acquired shunting or decrease the risk of persistent shunting.

Objective—To determine the effects of protamine sulfate on clot formation time and clot strength thromboelastography variables for canine whole blood samples. Animals—Blood samples obtained from 11 healthy dogs. Procedures—Blood samples were collected from jugular veins of dogs into syringes with 3.2% sodium citrate (blood to citrate ratio, 9:1). Blood samples were divided into aliquots, and protamine sulfate was added to various concentrations (0 [control], 22, 44, and 66 μg/mL). Prepared samples were activated with kaolin (n = 8) or not activated (8), CaCl2 was added, and thromboelastography was performed. Reaction time (R), clot formation time (K), rate of clot formation (α angle), and maximum amplitude (MA) were measured. Results—For kaolin-activated and nonactivated blood samples, protamine (66 μg/mL) significantly increased R and K and decreased α angle and MA, compared with values for control samples. Also, protamine (44 μg/mL) decreased MA in nonactivated blood samples and increased K and decreased α angle in kaolin-activated samples, compared with values for control samples. Conclusions and Clinical Relevance—Results indicated protamine prolonged clot formation time and decreased overall clot strength in a dose-dependent manner; such effects may contribute to a hypocoagulable state in dogs. Kaolin-activated and nonactivated blood samples were appropriate for measurement of the effects of protamine on coagulation. Administration of protamine to reverse the effects of heparin should be performed with caution.

Objective- To evaluate the effects of tylosin on C-reactive protein concentration, carriage of Salmonella enterica, and antimicrobial resistance genes in commercial pigs. Animals-120 pigs on 2 commercial farms. Procedures- A cohort of sixty 10-week-old pigs in 4 pens/farm (15 pigs/pen) was randomly selected. Equal numbers of pigs were given feed containing tylosin (40 μg/g of feed) for 0, 6, or 12 weeks. C-reactive protein concentrations were measured, microbial culture for S enterica in feces was performed, and antimicrobial resistance genes in feces were quantified. Results- No significant associations were detected between C-reactive protein concentration or S enterica status and tylosin treatment. During the 12 weeks of tylosin administration, increased levels of 6 antimicrobial resistance genes did not occur. Conclusions and Clinical Relevance-Treatment of pigs with tylosin did not affect C-reactive protein concentration or reduce carriage or load of S enterica. There was no evidence that pigs receiving tylosin had increased carriage of the 6 antimicrobial resistance genes measured. Impact for Human Medicine-S enterica is a public health concern. Use of the antimicrobial growth promoter tylosin did not pose a public health risk by means of increased carriage of S enterica.

Objective- To compare pharmacokinetics after a single IM or SC injection of ceftiofur crystalline-free acid (CCFA) to bearded dragons (Pogona vitticeps). Animals- 8 adult male bearded dragons. Procedures- In a preliminary experiment, doses of 15 and 30 mg/kg, SC, were compared in 2 animals, and 30 mg/kg resulted in a more desirable pharmacokinetic profile. Then, in a randomized, complete crossover experimental design, each bearded dragon (n = 6) received a single dose of 30 mg of CCFA/kg IM or SC; the experiment was repeated after a 28-day washout period with the other route of administration. Blood samples were collected at 10 time points for 288 hours after injection. Plasma concentrations of ceftiofur and desfuroylceftiofur metabolites were measured via reverse-phase high-performance liquid chromatography. Data were analyzed with a noncompartmental model. Results-No adverse effects were observed. Plasma concentrations greater than a target minimum inhibitory concentration of 1 μg/mL were achieved by 4 hours after administration by both routes. Mean plasma concentrations remained > 1 μg/mL for > 288 hours for both routes of administration. Conclusions and Clinical Relevance-A single dose of CCFA (30 mg/kg) administered IM or SC to bearded dragons yielded plasma concentrations of ceftiofur and its metabolites > 1 μg/mL for > 288 hours. The SC route would be preferred because of less variability in plasma concentrations and greater ease of administration than the IM route. Future studies should include efficacy data as well as evaluation of the administration of multiple doses.

Objective-To characterize the pharmacokinetics of dexmedetomidine after IV administration of a bolus to conscious healthy cats. Animals-5 healthy adult spayed female cats. Procedures-Dexmedetomidine was administered IV as a bolus at 3 doses (5, 20, or 50 μg/kg) on separate days in a random order. Blood samples were collected immediately before and at various times for 8 hours after drug administration. Plasma dexmedetomidine concentrations were determined with liquid chromatography–mass spectrometry. Compartment models were fitted to the concentration-time data by means of nonlinear regression. Results-A 2-compartment model best fit the concentration-time data after administration of 5 μg/kg, whereas a 3-compartment model best fit the data after administration of 20 and 50 μg/kg. The median volume of distribution at steady-state and terminal half-life were 371 mL/kg (range, 266 to 435 mL/kg) and 31.8 minutes (range, 30.3 to 39.7 minutes), respectively, after administration of 5 μg/kg; 545 mL/kg (range, 445 to 998 mL/kg) and 56.3 minutes (range, 39.3 to 68.9 minutes), respectively, after administration of 20 μg/kg; and 750 mL/kg (range, 514 to 938 mL/kg) and 75.3 minutes (range, 52.2 to 223.3 minutes), respectively, after administration of 50 μg/kg. Conclusions and Clinical Relevance-The pharmacokinetics of dexmedetomidine was characterized by a small volume of distribution and moderate clearance and had minimal dose dependence within the range of doses evaluated. These data will help clinicians design dosing regimens once effective plasma concentrations are established.

Objective-To determine the prevalence of circumcaval ureters and other caudal vena cava variations in cats and determine whether circumcaval ureters were associated with macroscopic evidence of ureteral obstruction. Sample-301 domestic cat cadavers obtained from an animal shelter. Procedures-All cat cadavers were examined, and anatomic variations of the ureters and caudal vena cava were recorded. In cadavers with a circumcaval ureter, kidney length, width, and height were measured, and the ureters were examined macroscopically to determine whether there was gross evidence of ureteral obstruction in cats with circumcaval ureters. Results-At least 1 circumcaval ureter was present in 106 of the 301 (35.2%) cats, with a right circumcaval ureter identified in 92 (30.6%) cats, a left circumcaval ureter identified in 4 (1.3%), and bilateral circumcaval ureters identified in 10 (3.3%). Twenty-one (7.0%) cats had a double caudal vena cava, including 2 cats in which the double caudal vena cava was the only anatomic abnormality identified. No sex predilection for anatomic abnormalities was found. Mean right kidney length was significantly greater than mean left kidney length in cats with a right circumcaval ureter. Conclusions and Clinical Relevance-Circumcaval ureter was present in approximately a third of cats in this study. Variation in the development of the caudal vena cava is the proposed cause. The clinical relevance of this variation is unknown.

Objective—To determine the effect of short-term hyperinsulinemia on the localization and expression of endothelin receptor (ETR)-A and ETR-B in lamellar tissue of the forelimbs of horses. Samples—Distal portion of 15 cadaveric forelimbs from healthy adult horses (1 limb/horse) obtained immediately after slaughter at an abattoir. Procedures—Each forelimb was assigned to 1 of 3 treatment groups (perfused with autologous blood for 10 hours [control perfusion; n = 5], perfused with an insulin [142 ± 81 μU/mL] perfusate for 10 hours [insulinemic perfusion; 5], or not perfused [unperfused control; 5]). Immunohistochemical evaluation of lamellar tissue was performed to assess localization of ETR-A and ETR-B. Expression of ETR-A and ETR-B was measured semiquantitatively on a scale of 0 to 3 (0 = none, 1 = mild, 2 = moderate, and 3 = high-intensity staining) and quantitatively by means of gray value analysis with imaging software. Results—In all specimens, ETR-A and ETR-B were localized in endothelium, smooth muscle cells, axons, and keratinocytes. Quantitative expression of ETR-A in the midportion of the primary epidermal lamellae for the insulinemic perfusion group (149 ± 16) was lower than that for the control perfusion group (158 ± 15). Expression of ETR-B in the primary epidermal lamellae tips for the insulinemic perfusion group (140 ± 29) was higher than that for the control perfusion group (114 ± 8). Conclusions and Clinical Relevance—Hyperinsulinemia caused significant changes in endothelin receptor expression, which suggested that ETR antagonists might be beneficial for treatment of laminitis in horses.

Objective-To determine cellular changes associated with secondary epidermal laminae (SEL) in forefeet and hind feet of ponies with insulin-induced laminitis. Animals-8 ponies. Procedures-Laminitis was induced in 4 ponies by IV administration of insulin and glucose; 4 control ponies received saline (0.9% NaCl) solution IV. Laminar tissue samples obtained from the dorsal aspects of the hooves were histologically evaluated. Primary epidermal lamina (PEL) length and width and SEL length, width, and angle were determined. Numbers of epidermal cell nuclei per micrometer and per total length of SEL and numbers of apoptotic and proliferative cells in axial, middle, and abaxial laminar regions were determined. Results-SEL in treatment group ponies were significantly longer, were significantly narrower, and had a smaller angle relative to PEL in all laminar regions versus control ponies. In treatment group ponies, the number of epidermal cell nuclei per SEL was typically higher and the number of cells per micrometer of SEL was lower in laminar regions, apoptotic cell numbers were higher in abaxial and middle regions in forefeet and hind feet, and proliferating cell numbers were higher in axial laminar regions in forefeet and all laminar regions in hind feet, versus control ponies. Conclusions and Clinical Relevance-Results indicated SEL elongation, narrowing, and alteration in orientation developed in all feet of ponies with insulin-induced laminitis. This was primarily attributable to cell stretching that developed at the same time as an accelerated cell death-proliferation cycle; differences in cell cycle responses among laminar regions between forefeet and hind feet may have been attributable to differences in load bearing.

Objective-To determine the effects of interleukin (IL)-6 and IL-1β stimulation on expression of growth differentiation factor (GDF)-5 and Wnt signaling pathway genes in equine chondrocytes. Sample-Macroscopically normal articular cartilage samples from 6 horses and osteochondral fragments (OCFs) from 3 horses. Procedures-Chondrocyte pellets were prepared and cultured without stimulation or following stimulation with IL-6 or IL-1β for 1, 2, 12, and 48 hours; expression of GDF-5 was determined with a quantitative real-time PCR assay. Expression of genes in various signaling pathways was determined with microarrays for pellets stimulated for 1 and 2 hours. Immunohistochemical analysis was used to detect GDF-5, glycogen synthase kinase 3β (GSK-3β), and β-catenin proteins in macroscopically normal cartilage samples and OCFs. Results-Chondrocytes stimulated with IL-6 had significantly higher GDF-5 expression within 2 hours versus unstimulated chondrocytes. Microarray analysis of Wnt signaling pathway genes indicated expression of GSK-3β and coiled-coil domain containing 88C increased after 1 hour and expression of β-catenin decreased after 2 hours of IL-6 stimulation. Results of immunohistochemical detection of proteins were similar to microarray analysis results. Chondrocytes in macroscopically normal articular cartilage and OCFs had immunostaining for GDF-5. Conclusion and Clinical Relevance-Results indicated IL-6 stimulation decreased chondrocyte expression of the canonical Wnt signaling pathway transactivator β-catenin, induced expression of inhibitors of the Wnt pathway, and increased expression of GDF-5. This suggested IL-6 may inhibit the Wnt signaling pathway with subsequent upregulation of GDF-5 expression. Anabolic extracellular matrix metabolism in OCFs may be attributable to GDF-5 expression. This information could be useful for development of cartilage repair methods.

Objective—To determine the efficacy of a multivalent modified-live virus (MLV) vaccine containing a Mannheimia haemolytica toxoid to reduce pneumonia and mortality rate when administered to calves challenge exposed with virulent Bibersteinia trehalosi. Animals—74 Holstein calves. Procedures—Calves were assigned to 2 treatment groups. Calves in the control group (n = 36) were vaccinated by SC administration of 2 mL of a commercial 5-way MLV vaccine, and calves in the other group (38) were vaccinated by SC administration of a 2-mL dose of a 5-way MLV vaccine containing M haemolytica toxoid (day 0). On day 21, calves were transtracheally administered B trehalosi. Serum was obtained for analysis of antibody titers against M haemolytica leukotoxin. Nasopharyngeal swab specimens were collected from calves 1 day before vaccination (day −1) and challenge exposure (day 20) and cultured to detect bacterial respiratory pathogens. Clinical scores, rectal temperature, and death attributable to the challenge-exposure organism were recorded for 6 days after challenge exposure. Remaining calves were euthanized at the end of the study. Necropsy was performed on all calves, and lung lesion scores were recorded. Results—Calves vaccinated with the MLV vaccine containing M haemolytica toxoid had significantly lower lung lesion scores, mortality rate, and clinical scores for respiratory disease, compared with results for control calves. Conclusions and Clinical Relevance—Administration of a multivalent MLV vaccine containing M haemolytica toxoid protected calves against challenge exposure with virulent B trehalosi by reducing the mortality rate, lung lesion scores, and clinical scores for respiratory disease.