Objective: To determine the tissue distribution of enrofloxacin after intramammary or simulated systemic administration in isolated perfused sheep udders by measuring its concentration at various sample collection sites. Sample: 26 udders (obtained following euthanasia) from 26 healthy lactating sheep. Procedures: For each isolated udder, 1 mammary gland was perfused with warmed, gassed Tyrode solution. Enrofloxacin (1 g of enrofloxacin/5 g of ointment) was administered into the perfused gland via the intramammary route or systemically via the perfusion fluid (equivalent to a dose of 5 mg/kg). Samples of the perfusate were obtained every 30 minutes for 180 minutes; glandular tissue samples were obtained at 2, 4, 6, and 8 cm from the teat base after 180 minutes. The enrofloxacin content of the perfusate and tissue samples was analyzed via high-performance liquid chromatography with UV detection. Results: After intramammary administration, maximun perfusate enrofloxacin concentration was detected at 180 minutes and, at this time, mean tissue enrofloxacin concentration was detected and mean tissue enrofloxacin concentration was 123.80, 54.48, 36.72, and 26.42 μg/g of tissue at 2, 4, 6, and 8 cm from the teat base, respectively. Following systemic administration, perfusate enrofloxacin concentration decreased with time and, at 180 minutes, tissue enrofloxacin concentrations ranged from 40.38 to 35.58 μg/g of tissue. Conclusions and Clinical Relevance: By 180 minutes after administration via the intramammary or systemic route in isolated perfused sheep mammary glands, mean tissue concentration of enrofloxacin was greater than the minimum inhibitory concentration required to inhibit growth of 90% of many common mastitis pathogens in sheep. Use of either route of administration (or in combination) appears suitable for the treatment of acute mastitis in sheep.

Objective: To determine the effects of meloxicam on values of hematologic and plasma biochemical analysis variables and results of histologic examination of tissue specimens of Japanese quail (Coturnix japonica). Animals: 30 adult Japanese quail. Procedures: 15 quail underwent laparoscopic examination of the left kidneys, and 15 quail underwent laparoscopic examination and biopsy of the left kidneys. Quail in each of these groups received meloxicam (2.0 mg/kg, IM, q 12 h; n = 10) or a saline (0.9% NaCl) solution (0.05 mL, IM, q 12 h; control birds; 5) for 14 days. A CBC and plasma biochemical analyses were performed at the start of the study and within 3 hours after the last treatment. Birds were euthanized and necropsies were performed. Results: No adverse effects of treatments were observed, and no significant changes in values of hematologic variables were detected during the study. Plasma uric acid concentrations and creatine kinase or aspartate aminotransferase activities were significantly different before versus after treatment for some groups of birds. Gross lesions identified during necropsy included lesions at renal biopsy sites and adjacent air sacs (attributed to the biopsy procedure) and pectoral muscle hemorrhage and discoloration (at sites of injection). Substantial histopathologic lesions were limited to pectoral muscle necrosis, and severity was greater for meloxicam-treated versus control birds. Conclusions and Clinical Relevance: Meloxicam (2.0 mg/kg, IM, q 12 h for 14 days) did not cause substantial alterations in function of or histopathologic findings for the kidneys of Japanese quail but did induce muscle necrosis; repeated IM administration of meloxicam to quail may be contraindicated.

Objective: To examine the effect of endotoxins on metabolism and histopathologic changes of isolated perfused equine forelimbs. Sample: Forelimbs (comprising the metacarpus and digit) were collected from cadavers of 12 healthy adult horses after slaughter at an abattoir (14 limbs; 1 forelimb of 10 horses and both forelimbs of 2 horses). Procedures: Forelimbs were perfused for 10 hours with autologous blood, with and without the addition of endotoxin (80 ng of lipopolysaccharide [LPS]/L). Two limbs of the endotoxin exposure group and 2 nonperfused limbs were loaded to failure of the suspensory apparatus of the pedal bone to evaluate the effect of body weight. Metabolic and histologic variables were evaluated. Results: Blood pressure increased during the first hour and did not differ between groups. Lactate dehydrogenase activity was similar in both groups and increased significantly during the 10-hour period; glucose consumption at 5 hours and lactate concentration at 8 hours were significantly higher in limbs exposed to endotoxin. The width of secondary epidermal lamellae was greater in LPS limbs. In the primary dermal lamellae of LPS limbs, there were significantly more vessels with an open lumen and aggregates of intravascular neutrophils. Conclusions and Clinical Relevance: In the blood-perfused isolated forelimbs of equine cadavers, exposure to LPS led to significant changes in the laminar tissue as well as to metabolic changes. Therefore, endotoxin should be considered as a causative factor for laminitis and not merely as a risk factor.

Objective: To determine whether the reported drug-drug interaction between the flea medication spinosad and ivermectin is attributable to inhibition of P-glycoprotein by spinosad. Animals: 6 healthy adult dogs with the ABCB1 wildtype genotype. Procedures: The study was conducted as a prospective, masked, randomized crossover design. Six dogs were allocated to 2 groups; each dog served as its own control animal. Dogs in one of the groups received spinosad at the manufacturer's recommended dose; the other group received no treatment. Forty-eight hours later, scintigraphic imaging of the head and abdomen were performed with the radiolabeled P-glycoprotein substrate methoxy-isobutyl-isonitrile (sestamibi) in both groups of dogs. After a washout period of 60 days, the dogs in each group received the alternate treatment, and scintigraphic imaging again was performed 48 hours later. Gallbladder-to-liver and brain-to-neck musculature ratios of technetium Tc 99m sestamibi were calculated for each dog and compared between treatments. Results: No significant differences in gallbladder-to-liver or brain-to-neck musculature ratios were found between treatments. Conclusions and Clinical Relevance: Results provided evidence that spinosad did not inhibit P-glycoprotein function 48 hours after spinosad was administered at the manufacturer's recommended dose. Further investigations will be necessary to elucidate the mechanism of the reported toxic interaction between spinosad and ivermectin.

Objective: To compare estimation of glomerular filtration rate determined via conventional methods (ie, scintigraphy and plasma clearance of technetium Tc 99m pentetate) and dynamic single-slice computed tomography (CT). Animals: 8 healthy adult cats. Procedures: Scintigraphy, plasma clearance testing, and dynamic CT were performed on each cat on the same day; order of examinations was randomized. Separate observers performed GFR calculations for scintigraphy, plasma clearance testing, or dynamic CT. Methods were compared via Bland-Altman plots and considered interchangeable and acceptable when the 95% limits of agreement (mean difference between methods ± 1.96 SD of the differences) were ≤ 0.7 mL/min/kg. Results: Global GFR differed < 0.7 mL/min/kg in 5 of 8 cats when comparing plasma clearance testing and dynamic CT; the limits of agreement were 1.4 and −1.7 mL/min/kg. The mean ± SD difference was −0.2 ± 0.8 mL/min/kg, and the maximum difference was 1.6 mL/min/kg. The mean ± SD difference (absolute value) for percentage filtration by individual kidneys was 2.4 ± 10.5% when comparing scintigraphy and dynamic CT; the maximum difference was 20%, and the limits of agreement were 18% and 23% (absolute value). Conclusions and Clinical Relevance: GFR estimation via dynamic CT exceeded the definition for acceptable clinical use, compared with results for conventional methods, which was likely attributable to sample size and preventable technical complications. Because 5 of 8 cats had comparable values between methods, further investigation of dynamic CT in a larger sample population with a wide range of GFR values should be performed.

Objective: To determine whether vaccine virus can be detected by use of reverse transcriptase (RT)-PCR assays for pooled and individual skin samples obtained from cattle after vaccination with a commercially available modified-live bovine viral diarrhea virus (BVDV) vaccine. Animals: 12 BVDV-seropositive steer calves and 7 BVDV-seronegative (antibody titer < 1:4) heifers; all cattle were free of persistent infection with BVDV. Procedures: 2 experiments were conducted. Cattle were vaccinated on day 0 with a commercially available modified-live BVDV vaccine. Skin samples were collected on days 0, 3 to 14, 16, and 18 for virus detection by use of RT-PCR assay on individual and pooled samples. In addition, blood samples and nasal swab specimens were collected for virus isolation. Results: All cattle, regardless of serologic status, had negative results for BVDV as determined by use of RT-PCR assay of individual and pooled skin samples. Virus was detected via virus isolation in serum or the buffy coat in 5 of 7 heifers that were seronegative when vaccinated. Conclusions and Clinical Relevance: These findings indicated that it would be unlikely to detect BVDV vaccine virus in skin by use of RT-PCR assay of individual or pooled skin samples obtained from cattle after vaccination with a commercially available modified-live BVDV vaccine. Veterinarians and producers should be confident that positive test results for BVDV on skin samples would not likely be caused by the vaccination virus after administration of a modified-live virus vaccine.

Objective: To determine aqueous humor flow rate (AHFR) in an avian species by use of anterior segment fluorophotometry. Animals: 9 healthy red-tailed hawks (Buteo jamaicensis; 4 males and 5 females) that ranged from 8 months to 8 years of age. Procedures: A protocol was developed for fluorophotometric determination of AHFR. Topical administration of 10% fluorescein was used to load the corneas, and corneal and aqueous humor fluorescein concentrations were measured approximately 5, 6.5, and 8 hours later. Concentration-versus-time plots were generated, and slopes and cornea-to-aqueous humor concentration ratios from these plots were used to manually calculate flow rates. Results: Mean ± SD AHFRs for the right eye, left eye, and both eyes were 3.17 ± 1.36 μL/min (range, 1.67 to 6.21 μL/min), 2.86 ± 0.88 μL/min (range, 2.04 to 4.30 μL/min), and 2.90 ± 0.90 μL/min (range, 1.67 to 4.42 μL/min), respectively. The AHFRs were similar for right and left eyes. These flow rates represented a mean aqueous humor transfer coefficient of 0.0082/min, which is similar to that of mammalian species. Conclusions and Clinical Relevance: The AHFR in red-tailed hawks was similar to that of most mammalian species, and the fractional egress was almost identical to that of other species. This information will allow a greater understanding of aqueous humor flow in avian eyes, which is crucial when evaluating diseases that affect avian eyes as well as medications that alter aqueous humor flow.

This project investigated the use of ultrasonography at first diagnosis of presumptive early bovine respiratory disease (BRD) in feedlot cattle from western Canada. One hundred seventy-four cattle (116 cases and 58 controls) at high risk of developing BRD were enrolled in a prospective longitudinal study over 2 y (2006-2007). Cattle with clinical signs relating to the respiratory system and assessed as sick at the time of feedlot arrival (arrival fever cases) or assessed as sick in the pen 3 to 30 d post-arrival (post-arrival fever cases, post-arrival no fevers cases) were eligible for enrollment. Control animals were identified at the time of case enrollments. Ultrasonography was done using a 3.5 sector transducer at enrollment and at 2, 4, and 6 wk post-enrollment. Lung lesions were identified at least 1 time over the course of the trial in 32/116 (28%) cases and 9/58 (16%) controls. At enrollment, lung lesions were identified in 20/115 (17%) cases and 2/55 (4%) controls (data unreadable n = 4). Post-arrival fever cases (14/48) were the most likely to have a lesion identified using ultrasound. In arrival fever cases, average daily gain (enrollment to last ultrasound, average 34 d) was improved (P = 0.007) in cattle identified with a lesion at enrollment using ultrasound compared with those not identified with a lesion at that time, potentially demonstrating the effects of gut fill at arrival weighing, as these sicker animals may have eaten less prior to arrival and, therefore, had more room for improvement in weight over time due to restoration of normal gut fill. None of the ultrasound time points explored (enrollment, 2, 4, or 6 wk post-enrollment) were associated with the animal health outcomes of interest (subsequent treatment, chronicity, wastage, or mortality) for cattle enrolled at arrival or post-arrival.

The objective of this study was to evaluate the bactericidal effect of shock waves (SWs) on gram-negative or gram-positive monocultured biofilms grown on an orthopedic implant in vitro. Cortical bone screws were individually cultured with Escherichia coli or Staphylococcus epidermidis to produce a biofilm. In each run of 8 screws, 6 screws were treated with shock waves and then sonicated to disrupt the biofilm. One screw was sonicated only and one was not shock waved or sonicated before sampling for plate count dilutions. Post-treatment serial dilutions and plate counts were done on an aliquot from the vial containing each screw to obtain the number of colony-forming units (CFUs). Shock waves were at a constant energy of 0.15 mJ/mm2. Pulse number and screw orientation were varied. A linear mixed-effects model was used with “treatment” as a fixed effect and “run” as a random effect. Pairwise comparisons of treatments were performed with Tukey-Cramer’s adjustment for P-values. Sonicated plate counts were greater than nonsonicated counts for each run. When all sonicated screws were compared to all nonsonicated screws, the counts were significantly increased (P = 0.0091). For each paired comparison between sonicated and shock wave treatment, the only significant difference was in the S. epidermidis biofilm treated at 2000 pulses in a horizontal position, which increased the post-treatment count (P = 0.0445). No bactericidal effects were seen on monocultured biofilms on cortical bone screws treated with shock waves.

Objective-To compare in vitro expansion, explant colonization, and matrix synthesis of equine tendon- and bone marrow-derived cells in response to insulin-like growth factor-I (IGF-I) supplementation. Sample-Cells isolated from 7 young adult horses. Procedures-Tendon- and bone marrow-derived progenitor cells were isolated, evaluated for yield, and cultured on autogenous cell-free tendon matrix for 7 days. Samples were analyzed for cell viability and expression of collagen type I, collagen type III, and cartilage oligomeric matrix protein mRNAs. Collagen and glycosaminoglycan syntheses were quantified over a 24-hour period. Results-Tendon- and bone marrow–derived cells required 17 to 19 days of monolayer culture to reach 2 passages. Mean +/- SE number of monolayer cells isolated was higher for tendon-derived cells (7.9 +/- 0.9 × 10(6)) than for bone marrow–derived cells (1.2 +/- 0.1 × 10(6)). Cell numbers after culture for 7 days on acellular tendon matrix were 1.6- to 2.8-fold higher for tendon-derived cells than for bone marrow-derived cells and 0.8- to 1.7-fold higher for IGF-I supplementation than for untreated cells. New collagen and glycosaminoglycan syntheses were significantly greater in tendon-derived cell groups and in IGF-I-supplemented groups. The mRNA concentrations of collagen type I, collagen type III, and cartilage oligomeric matrix protein were not significantly different between tendon- and bone marrow-derived groups. Conclusions and Clinical Relevance-In vitro results of this study suggested that tendon-derived cells supplemented with IGF-I may offer a useful resource for cell-based strategies in tendon healing.