Objective: To evaluate the use of midazolam, ketamine, and xylazine for total IV anesthesia (TIVA) in horses. Animals: 6 healthy Thoroughbred mares. Procedures: Horses were sedated with xylazine (1.0 mg/kg, IV). Anesthesia was induced with midazolam (0.1 mg/kg, IV) followed by ketamine (2.2 mg/kg, IV) and was maintained with an IV infusion of midazolam (0.002 mg/kg/min), ketamine (0.03 mg/kg/min), and xylazine (0.016 mg/kg/min). Horses underwent surgical manipulation and injection of the palmar digital nerves; duration of the infusion was 60 minutes. Additional ketamine (0.2 to 0.4 mg/kg, IV) was administered if a horse moved its head or limbs during procedures. Cardiopulmonary and arterial blood variables were measured prior to anesthesia; at 10, 20, 30, 45, and 60 minutes during infusion; and 10 minutes after horses stood during recovery. Recovery quality was assessed by use of a numeric (1 to 10) scale with 1 as an optimal score. Results: Anesthesia was produced for 70 minutes after induction; supplemental ketamine administration was required in 4 horses. Heart rate, respiratory rate, arterial blood pressures, and cardiac output remained similar to preanesthetic values throughout TIVA. Arterial partial pressure of oxygen and oxygen saturation of arterial hemoglobin were significantly decreased from preanesthetic values throughout anesthesia; oxygen delivery was significantly decreased at 10- to 30-minute time points. Each horse stood on its first attempt, and median recovery score was 2. Conclusions and Clinical Relevance: Midazolam, ketamine, and xylazine in combination produced TIVA in horses. Further studies to investigate various dosages for midazolam and ketamine or the substitution of other α2-adrenoceptor for xylazine are warranted.

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.

Objective: To investigate forelimb hoof wall strains and shape changes in unshod horses undergoing regular moderate exercise on a treadmill at selected speeds and gaits. Animals: 6 horses of various body types. Procedures: Each horse was exercised on a treadmill (walking, trotting, and cantering, with or without galloping at 12.5 m/s) 3 times a week for 4 consecutive weeks; duration of each exercise session ranged from 10 to 14 minutes. During the 4-week period, the proximal hoof circumference (PHC) and toe angle (TA) of each forelimb hoof were measured weekly with a flexible measuring tape and a hoof gauge, respectively. Forelimb hoof wall strains were measured bilaterally at the toe and each quarter (3 strain gauges) immediately before the first and after the last exercise session. Results: Strain measurements revealed a consistent pattern of deformation of the hoof wall in both forelimbs at all gaits; strains increased during the stance phase of the stride. Strain values were dependent on site and gait. Compared with initial findings, mean TA increased significantly, whereas mean PHC did not, after the 4-week exercise period. A relationship between TA changes and hoof wall strains could not be established. Conclusions and Clinical Relevance: In unshod horses, forelimb hoof wall strains were affected by site and gait, but not by discrete changes in TA; PHC did not change in response to moderate regular exercise. The pattern of hoof loading was consistent despite significant changes in TA.

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 morphological and mechanical properties of trabecular bone of horses with a bone fragility syndrome (BFS; including silicate-associated osteoporosis). Sample: Cylindrical trabecular bone samples from the distal aspects of cadaveric third metacarpal bones of 39 horses (19 horses with a BFS [BFS bone samples] and 20 horses without a BFS [control bone samples]). Procedures: Bone samples were imaged via micro-CT for determination of bone volume fraction; apparent and mean mineralized bone densities; and trabecular number, thickness, and separation. Bone samples were compressed to failure for determination of apparent elastic modulus and stresses, strains, and strain energy densities for yield, ultimate, and failure loads. Effects of BFS and age of horses on variables were determined. Results: BFS bone samples had 25% lower bone volume fraction, 28% lower apparent density, 18% lower trabecular number and thickness, and 16% greater trabecular separation versus control bone samples. The BFS bone samples had 22% lower apparent modulus and 32% to 33% lower stresses, 10% to 18% lower strains, and 41 % to 52% lower strain energy densities at yield, ultimate, and failure loads, compared with control bone samples. Differences between groups of bone samples were not detected for mean mineral density and trabecular anisotropy. Conclusions and Clinical Relevance: Results suggested that horses with a BFS had osteopenia and compromised trabecular bone function, consistent with bone deformation and pathological fractures that develop in affected horses. Effects of this BFS may be systemic, and bones other than those that are clinically affected had changes in morphological and mechanical properties.

Objective: To evaluate the use of the oxygen content–based index, Fshunt, as an indicator of venous admixture (Qs/Qt) at various fractions of inspired oxygen (Fio2s) in anesthetized sheep undergoing Flung or 2-lung ventilation. Animals: 6 healthy adult female sheep. Procedures: Sheep were anesthetized and administered 5 different Fio2s (0.21, 0.40, 0.60, 0.80, and 1.00) in random order during 2-lung mechanical ventilation. Arterial and mixed venous blood samples were obtained at each Fio2 after a 15-minute stabilization period. Vital capacity alveolar recruitment maneuvers were performed after blood collection. The previously used Fio2 sequence was reversed for sample collection during Flung ventilation. Blood samples were analyzed for arterial, pulmonary end-capillary, and mixed venous oxygen content and partial pressure and for hemoglobin concentration. Oxygen hemoglobin saturation, Qs/Qt, Fshunt, and oxygen tension–based indices (OTIs; including Pao2:Fio2, alveolar-arterial difference in partial pressure of oxygen [Pao2 – Pao2], [Pao2 – Pao2]:Fio2, [Pao2 – Pao2]:Pao2, and Pao2:Pao2) were calculated at each Fio2; associations were evaluated with linear regression analysis, concordance, and correlation tests. Intermethod agreement between Qs/Qt and Fshunt was tested via Bland-Altman analysis. Results: Strong and significant associations and substantial agreement were detected between Fshunt and Qs/Qt. Relationships between OTIs and Qs/Qt varied, but overall correlations were weak. Conclusions and Clinical Relevance: Whereas OTIs were generally poor indicators of Qs/Qt, Fshunt was a good indicator of Qs/Qt at various Fio2s, regardless of the magnitude of Qs/Qt and could be potentially used as a surrogate for Qs/Qt measurements in healthy sheep.

Objective: To optimize the use of CT-guided modeling for the calculation of body surface area (BSA) in domestic rabbits (Oryctolagus cuniculus). Animals: 12 domestic rabbits. Procedures: Adult rabbits (body weight, 1 to > 4 kg) that were client-owned animals undergoing CT for disease diagnosis or deceased laboratory animals donated from other research projects were scanned with a CT scanner. Images were transferred to a radiation therapy planning software program. Image slices were captured as contiguous slices at 100 kVp and 100 mA and processed to 0.1-cm-thick sections. The length of each contoured slice was summed to calculate a final BSA measurement. Nonlinear regression analysis was then used to derive an equation for the calculation of BSA in rabbits. Results: The constant calculated by use of this method was 9.9 (range, 9.59 to 10). The R2 for the goodness of fit was 0.9332. The equation that best described BSA as a function of body weight for domestic rabbits with this method was as follows: BSA = (9.9 × [body weight {in grams}]2/3)/10,000. Conclusions and Clinical Relevance: The BSA calculated via the CT-guided method yielded results similar to those obtained with equations for other similarly sized mammals and verified the use of such equations for rabbits. Additionally, this technique can be used for species that lack equations for the accurate calculation of BSA.

The Streptococcus suis 103 gene product is an immunogenic and protective lipoprotein that is a component of an ATP-binding cassette transporter implicated in zinc uptake. Belonging to the same transcriptional unit and downstream of the 103 gene is a gene that encodes a homologue of the pneumococcal histidine triad (Pht) protein Pht309. In an intraperitoneal mouse model the virulence of a mutant lacking the 103 gene was more than 50 times lower than that of the wild-type (WT) parent strain, S. suis serotype 2 strain P1/7. In addition, the immunogenicity of this mutant was dramatically decreased. In striking contrast, the virulence and immunogenicity of a P1/7 mutant lacking the Pht309 gene were similar to those of the parent strain. These results demonstrate that the 103 lipoprotein is strongly involved in S. suis virulence and support the hypothesis that this lipoprotein might be an excellent candidate for vaccines aiming to achieve broad protection against streptococci.

This retrospective study was done to characterize the levels of vascular endothelial growth factor (VEGF) and hypoxia inducible factor 1 (HIF-1α) in dog brains with neo-vascularization in the cerebral cortex of frontal, temporal, and parietal lobe by using immunohistochemistry (IHC) and Western blot. In neo-vascularized (NV) brains, we analyzed the number and area of blood vessels and the expression of VEGF and HIF-1α. The IHC results showed that the number and area of blood vessels, as assessed by immunolabeling for von Willebrand factor, was higher in the NV brain than in the control brain. The Western blot results showed that the level of VEGF was increased, predominantly in NV brain of the cerebral cortex relative to the clinically normal cerebral cortex, whereas the expression of HIF-1α in NV brains was not different from the control brains. Our study showed that dilatation of vessels and development of new vessels in the cerebral cortex were observed in cases of canine CNS disease and found increased expression of VEGF in canine brains with neo-vascularization.

The objective of this study was to compare bone marrow (BM) aspirates from the sternum and the tuber coxae of middle-aged horses. Bone marrow was obtained from the sternum and both tubera coxae of 12 healthy, 13-year-old geldings. Two different puncture techniques were used for the tuber coxae. The 2 syringes used for sternal sampling were evaluated separately. The mononuclear cell (MNC) fraction of the BM was isolated and the mesenchymal stem cells (MSCs) were culture-expanded. At the sternum, BM aspiration was always possible. Bone marrow aspiration at the tuber coxae required straight and deep needle penetration combined with high negative pressure. With this technique a median sample amount of 11.0 mL with large individual variation was obtained. A median of 3.06 × 10(6) MNC/mL BM (1st syringe) and 2.46 × 10(6) MNC/mL BM (2nd syringe) was isolated from sternal samples. In contrast, the tuber coxae yielded a median of 0.27 × 10(6) MNC/mL BM. The first passage yielded a median of 2.19 × 10(6) MSC (1st syringe) and 1.13 × 10(6) MSC (2nd syringe) from sternal samples, compared to a significantly lower median number of MSC from tuber coxae BM (0.06 × 10(6) MSC). The number of MNC and MSC obtainable from the BM aspirates taken from the tuber coxae is significantly lower than that obtained from the sternal BM aspirates. Autologous BM for the equine athlete is particularly clinically relevant at an advanced age. Based on our findings, the tuber coxae cannot be recommended for BM aspiration in middle-aged horses.