Objective-To evaluate the effect of prolonged water exposure on tissue mass and solutes of outer and inner layers of the stratum medium, sole, frog, and the stratum medium (SMZA) zona alba layer of horses' hooves. Specimen Population-10 hooves from 10 horses without foot abnormalities. Procedure-Hoof wall tissue specimens were obtained and immersed for 10 days in distilled deionized water. Serial changes in mass were recorded during the immersion period. Subsequently, osmolarity and Na+, K+, Cl-, and protein concentrations of the immersion solution were quantified. Results-Fully cornified outer hoof wall, sole, and frog epidermal structures increased in mass, whereas the SMZA lost mass when immersed in water. All hoof structures had a variable loss of crystalloids during immersion, but none of the specimens lost proteins. The frog epidermis was distinct in that total solute lost during immersion could not be ascribed to Na+, K+, and Cl-. Conclusions and Clinical Relevance-Data support a 2-compartment model for the fully cornified outer stratum medium, frog, and sole that permits the exchange of crystalloids, but not proteins, across the cell membrane and infers that topical agents containing proteins cannot benefit the hoof. The unique osmotic behavior of the SMZA relative to other hoof structures suggests the hypothesis that it is composed of transitional epithelial cells. The solutes lost from frog epithelium are interpreted to reflect its unique lipid composition.

Objective-To develop polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis for molecular typing of strains of Streptococcus zooepidemicus and to use the new typing method to analyze a collection of isolates from the respiratory tract of Thoroughbreds. Sample Population-10 strains of S zooepidemicus, 65 isolates from the respiratory tract of 9 yearlings following long distance transportation, and 89 isolates from tracheal aspirates of 20 foals with pneumonia. Procedure-Phenotypic variations in the SzP protein were detected by western immunoblot analysis. Using PCR-RFLP analysis, genotypes were obtained with primer sets from the SzP gene, followed by restriction endonuclease digestion of the amplicons. Results-Unique genotypic patterns were obtained with a primer set designed from both ends of the structural gene and the restriction endonuclease Dde I. Forty-five isolates from the lymphoid tissue within the pharyngeal recess (ie, pharyngeal tonsil) of yearlings included 10 SzP genotypes and SzP phenotypes. Isolates from the trachea of each yearling were of a single genotype that was also present among isolates from the pharyngeal tonsil of the same horses. Isolates from tracheal aspirates of foals belonged to 14 genotypes. Conclusion and Clinical Relevance-Analysis of the SzP gene by use of PCR-RFLP was effective for molecular typing of strains of S zooepidemicus in the study of respiratory tract disease in horses. Results of PCR-RFLP analysis indicate that a single strain of S zooepidemicus can migrate from the pharyngeal tonsil to the trachea at a high rate in horses undergoing long distance transportation.

Objective-To determine plasma concentrations of adrenocorticotrophic hormone (ACTH) and alpha-melanocyte stimulating-hormone (α-MSH) in healthyferrets and ferrets with hyperadrenocorticism. Animals-16 healthy, neutered, privately owned ferrets, 28 healthy laboratory ferrets (21 sexually intact and 7 neutered), and 28 ferrets with hyperadrenocorticism. Procedures-Healthy ferrets were used for determination of reference plasma concentrations of ACTH and alpha-MSH. Diagnosis of hyperadrenocorticism was made on the basis of history, clinical signs, urinary corticoid-to-creatinine ratios, ultrasonography of the adrenal glands, and macroscopic or microscopic evaluation of the adrenal glands. Blood samples were collected during isoflurane anesthesia. Plasma concentrations of ACTH and α-MSH were measured by radioimmunoassay. Results-Plasma concentrations of ACTH in 23 healthy neutered ferrets during the breeding season ranged from 4 to 145 ng/L (median, 50 ng/L). Plasma concentrations of α-MSH in 44 healthy neutered or sexually intact ferrets during the breeding season ranged from < 5 to 617 ng/L (median, 37 ng/L). Reference values (the central 95% of the values) for ACTH and α-MSH were 13 to 100 ng/L and 8 to 180 ng/L, respectively. Plasma concentrations of ACTH and α-MSH in ferrets with hyperadrenocorticism ranged from 1 to 265 ng/L (median, 45 ng/L) and 10 to 148 ng/L (median, 46 ng/L), respectively. These values were not significantly different from those of healthy ferrets. Plasma ACTH concentrations of sexually intact female ferrets in estrus were significantly higher than those of neutered females. Conclusions and Clinical Relevance-Ferrets with hyperadrenocorticism did not have detectable abnormalities in plasma concentrations of ACTH or α-MSH. The findings suggest that hyperadrenocorticism in ferrets is an ACTH and α-MSH-independent condition.

Objective-To determine the effect of caprine arthritis-encephalitis virus (CAEV) infection on expression of interleukin-16 (IL-16). Animals-6 goats experimentally infected with CAEV and 6 age-matched healthy uninfected control goats. Procedure-Peripheral blood mononuclear cells (PBMCs) and synovial membrane cells from infected and control goats cultured with or without phytohemagglutinin were analyzed for IL-16 mRNA by use of a reverse transcriptase-polymerase chain reaction assay with goat-specific primers, after cloning and sequencing of a 384-bp fragment of the goat IL-16 gene. Synovial fluid, serum, and culture supernatants of PBMCs and synovial cells of control and CAEV-infected goats were analyzed for IL-16 by use of an ELISA. Results-The 384-bp product was 86% homologous to the corresponding human IL-16 nucleotide sequence. Higher expression of IL-16 mRNA in PBMCs (unstimulated or stimulated with phytohemagglutinin) was detected in samples from CAEV-infected goats, compared with control goats, but the difference was not significant. Synovial membrane cells infected in vitro had higher expression than uninfected control cells. Higher IL-16 concentration was detected in synovial fluid, serum, and culture supernatants of PBMCs of infected goats than in samples from control goats. Conclusions and Clinical Relevance-Infection with CAEV increases expression of IL-16, a proinflammatory and chemotactic cytokine. This cytokine appears to be constitutively expressed at low concentrations in normal uninfected PBMCs and synovial membrane cells. Increased production of IL-16 in CAEV infection may partly be responsible for increased lymphoid cell infiltrations observed in arthritic joints and other tissues of CAEV-infected goats.

Objective-To evaluate a model for atopic dermatitis (AD) and to measure the effect of sensitization in Beagles genetically predisposed to produce high serum concentrations of allergen specific IgE. Animals-22 laboratory Beagles. Procedure-Seventeen dogs were sensitized from birth to 3 allergens (recombinant birch pollen, Dermatophagoides pteronyssinus, and D farinae). Five nonsensitized dogs from the same litters served as controls. Clinical scoring, regular intradermal testing, measurement of serum concentrations of allergen-specific IgE, and collection of biopsy specimens of skin at 23, 32, and 43 weeks of age were performed. Serial tissue sections were stained for identification of IgE+ cells, mast cells and their subtypes, T-cells, Langerhans cells, and major histocompatibility complex class-II+ cells. At the age of 15 months, dogs were continuously exposed to 2 µg of mite allergen/ g of dust. Results-Sensitized dogs had positive intradermal test reactions and significantly higher serum concentrations of allergen specific IgE, compared with nonsensitized dogs. In sensitized and nonsensitized dogs, a significantly higher number of mast cells was found at predilection sites, compared with the control biopsy site. The number of mast cells at predilection sites increased with age. Sensitization significantly increased the number of epidermal Langerhans cells by 23 weeks of age. The number of epidermal Langerhans cells significantly increased in nonsensitized dogs by 32 weeks of age. Clinical scoring only revealed mild transient erythema in some dogs. Conclusion and Clinical Relevance-Increases in concentrations of serum allergen-specific IgE and exposure to allergens is not sufficient to induce clinical signs of AD in genetically predisposed dogs.

Objective-To determine the effect of glucocorticoids on the induction of alkaline phosphatase (ALP) isoenzymes in the liver, kidneys, and intestinal mucosa, 3 tissues that are principally responsible for ALP synthesis in dogs. Sample Population-Tissues from the liver, kidneys, and intestinal mucosa of 6 dogs treated with 1 mg of prednisone/kg/d for 32 days and 6 untreated control dogs. Procedure-Using canine-specific primers for the ALP isoenzymes, a reverse transcription-polymerase chain reaction assay was designed to measure liver ALP (LALP) and intestinal ALP (IALP) mRNA and heterogeneous nuclear RNA (hnRNA) expression in tissues from the liver and kidneys and intestinal mucosa of glucocorticoid-treated and control dogs. Tissue ALP isoenzyme activities were compared between the groups. Results-The LALP activity and mRNA concentrations increased in tissues of the liver and kidneys in dogs treated with prednisone, whereas LALP hnRNA increased only in liver tissues. The IALP activity and mRNA expression increased in intestinal mucosa and liver tissues in prednisone-treated dogs. We did not detect an increase in IALP hnRNA expression in these tissues. Conclusions and Clinical Relevance-Synthesis of ALP is increased in the liver, kidneys, and intestinal mucosa of dogs in response to prednisone treatment. This response appears to be regulated at the transcriptional level, but mechanisms may differ between LALP and IALP.

Objective-To determine the effect of a commercially available nasal strip on airway mechanics in exercising horses. Animals-6 horses (5 Standardbreds and 1 Thoroughbred). Procedure-Horses exercised on a treadmill at speeds corresponding to 100 and 120% of maximal heart rate with and without application of a commercially available nasal strip. Concurrently, tracheal pressures, airflow, and heart rate were measured. Peak inspiratory and expiratory tracheal pressures, airflow, respiratory frequency, and tidal volume were recorded. Inspiratory and expiratory airway resistances were calculated by dividing peak pressures by peak flows. Endoscopic examination of the narrowest point of the nasal cavity (ie, nasal valve) was performed in 1 resting horse before, during, and after application of a nasal strip. Results-During exercise on a treadmill, peak tracheal inspiratory pressure and inspiratory airway resistance were significantly less when nasal strips were applied to horses exercising at speeds corresponding to 100 and 120% of maximal heart rate. Application of the nasal strip pulled the dorsal conchal fold laterally, expanding the dorsal meatus. Conclusions and Clinical Relevance-The commercially available nasal strip tented the skin over the nasal valve and dilated that section of the nasal passage, resulting in decreased airway resistance during inspiration. The nasal strip probably decreases the amount of work required for respiratory muscles in horses during intense exercise and may reduce the energy required for breathing in these horses.

Objective-To evaluate postexposure prophylaxis (PEP) in dogs experimentally infected with rabies. Procedure-29 Beagles. Procedure-Dogs were sedated and inoculated in the right masseter muscle with a salivary gland homogenate from a naturally infected rabid dog (day 0). Six hours later, 5 dogs were treated by administration of 2 murine anti-rabies glycoprotein monoclonal antibodies (mAb) and commercial vaccine; 5 received mAb alone; 5 received purified, heat-treated, equine rabies immune globulin (PHT-ERIG) and vaccine; 5 received PHT-ERIG alone; 4 received vaccine alone; and 5 control dogs were not treated. The mAb or PHTERIG was administered at the site of rabies virus inoculation. Additional vaccine doses for groups mAb plus vaccine, PHT-ERIG plus vaccine, and vaccine alone were administered IM in the right hind limb on days 3, 7, 14, and 35. Results-All control dogs and dogs that received only vaccine developed rabies. In the PHT-ERIG and vaccine group, 2 of 5 dogs were protected, whereas none were protected with PHT-ERIG alone. Use of mAb alone resulted in protection in 4 of 5 dogs. Administration of mAb in combination with vaccine provided protection in all 5 dogs. Conclusions and Clinical Relevance-Current national guidelines recommend euthanasia or a 6- month quarantine for unvaccinated animals exposed to rabies. Findings from this study document that vaccine alone following severe exposure was unable to provide protection from rabies. However, vaccine combined with mAb resulted in protection in all treated dogs, revealing the potential use of mAb in PEP against rabies in naïve dogs.

Objective-To assess gastric tone in the proximal portion of the stomach in horses during and after ingestion of 4 diets (2 diets of grain and 2 diets of hay). Animals-6 adult horses. Procedure-A polyester bag with a volume of approximately 1,600 ml was inserted through a gastric cannula into the proximal portion of the stomach of each horse. Internal pressure of the bag was maintained at 2 mm Hg by use of an electronic barostat, and changes in bag volume were recorded before, during, and after horses consumed diets of grain or hay. Each horse was fed 0.5 and 1.0 g of grain/kg and 0.5 and 1.0 g of hay/kg. Changes in bag volume measured by use of the barostat were indirectly related to changes in tone of the gastric wall. Results-Food intake caused a distinctly significant biphasic increase in volume. The first phase was during active ingestion, which was followed shortly by a second, more prolonged postprandial phase. The ingestion-related phase of the response to intake of a diet of 1 g of hay/kg was significantly greater than that for the other diets. Conclusion and Clinical Relevance-Ingestion of a solid meal induces a biphasic relaxation response in the proximal portion of the stomach of horses. Magnitude of the ingestion-related phase may be determined by size of the meal.

Objective-To evaluate in vivo activityin dogs of meloxicam or aspirin, previously shown in vitro to be a selective cyclooxygenase-2 (COX-2) inhibitor (COX-1 sparing drug), or a nonselective COX inhibitor, respectively. Animals-12 male dogs with unilateral osteoarthritis of the stifle joint. Procedure-Each dog was treated in a crossover design with aspirin or meloxicam for 21 days. Prostaglandin E2 (PGE2) concentrations were measured at days 0 (baseline), 7, and 21 of each treatment period in lipopolysaccharide (LPS)-stimulated blood, synovial fluid collected by arthrocentesis, and endoscopic gastric mucosal biopsy specimens. Thromboxane B2 (TXB2) was evaluated in blood on days 0, 7, and 21 of each treatment period. Results-Aspirin administration significantly suppressed PGE2 concentrations in blood, gastric mucosa, synovial fluid, and suppressed TXB2 concentration in blood at days 7 and 21. Meloxicam administration significantly suppressed PGE2 concentrations in blood and synovial fluid at days 7 and 21, but had no effect on concentrations of TXB2 in blood or PGE2 in gastric mucosa. Suppression of LPS-stimulated PGE2 concentrations in blood and synovial fluid by aspirin and meloxicam administration is consistent with activity against the COX-2 isoenzyme. Suppression of concentrations of PGE2 in the gastric mucosa and TXB2 in blood by aspirin administration is consistent with activity against COX-1. Meloxicam, in contrast, had a minimal effect on functions mediated by COX-1. Conclusions and Clinical Relevance-Meloxicam acts in vivo in dogs as a COX-1 sparing drug on target tissues by sparing gastric PGE2 synthesis while retaining antiprostaglandin effects within inflamed joints.