Administration of an N-lauroylsarcosine-derived outer membrane protein fraction of Pasteurella haemolytica A1 (SCI-1) induced a protective response in calves against intrathoracic challenge exposure with the homologous serovar. Outer membrane proteins from heterologous serovars, A6 and A9, induced partial protection that was associated with their respective similarities to serovar A1 in outer membrane protein profiles derived by use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Calves vaccinated with SCI preparations did not have detectable neutralizing antibody to P haemolytica A1 leukotoxin. Antibodies to whole-cell antigens, carbohydrate-protein subunit antigen, and SCI-1 were associated with resistance, which indicates that protein antigens shared among cell surface, carbohydrate-protein subunit, and SCI preparations are immunogenic and enhance resistance to experimental challenge exposure.

Casein has been used as a protein source in diets designed to dissolve canine ammonium urate uroliths and to prevent their recurrence, because it contains fewer purine precursors than do many other sources of protein. However, an important question is whether reduced quantities of dietary casein have any benefit in modifying saturation of urine with urates. To answer this question, activity product ratios of uric acid, sodium urate, and ammonium urate were determined in 24-hour urine samples produced by 6 healthy Beagles during periods of consumption of a 10.4% protein, casein-based (10.4% casein) diet and a 20.8% protein, casein-based (20.8% casein) diet. Significantly lower activity product ratios of uric acid, sodium urate, and ammonium urate were observed when dogs consumed the 10.4% casein diet. Significantly lower 24-hour urinary excretions of ammonia and phosphorus were observed when dogs consumed the 10.4% casein diet. Twenty-four-hour urinary excretions of magnesium and 24-hour urine pH values were significantly higher when dogs were fed the 10.4% casein diet. These results suggest that use of the 10.4% casein diet in protocols designed for dissolution and prevention of uric acid, sodium urate, and ammonium urate uroliths in dogs may be beneficial.

Bovine immunodeficiency virus (BIV), a lentivirus, is prevalent in dairy and beef cattle in southeastern United States and may be associated with a lymphoproliferative disease. The mode(s) of BIV transmission are undefined. Because artificial insemination is a common practice in dairy production, contaminated stud semen could serve as an important source of infection if the virus is harbored in seminal fluids. To evaluate this possibility, we procured 11 cryopreserved semen specimens from a stud semen repository. Leukocytes were purified from the specimens, and the leukocyte DNA was used as template in a polymerase chain reaction procedure that targeted a 235-base pair, highly conserved domain of the BIV pol gene. The target sequence was amplified from the seminal leukocyte DNA of 9 of the specimens (82%), and nucleotide sequencing confirmed the BIV specificity of the fragment. This finding provides evidence that stud bull semen may serve as an important reservoir of BIV, suggesting the possibility that artificial insemination of dairy cows may have a major role in transmission and wide-spread dissemination of this bovine lentivirus.

Toxoplasma gondii-specific IgA, IgM, and IgG were measured by ELISA in the serum and aqueous humor of 29 client-owned cats with indigenous aviates and 7 specific-pathogen-free cats tested sequentially for 20 weeks after inoculation with T. gondii. Local antibody production in aqueous humor was estimated by multiplying the aqueous humor-to-serum T gondii-specific antibody ratio by the serum-to-aqueous humor total IgG (C value) or IgG (C value) ratio. Evidence for local production of antibody in aqueous humor was defined as C value greater than 8 or CTC value greater than 1. Toxoplasma gondii-specific IgM CTC values, IgG CTC values, or IgA CTC values greater than 1 were detected in the aqueous humor of 18 of 29 (62.1%) client-owned cats with endogenous uveitis; 2 cats had IgA CTC values greater than 1 without detectable IgM or IgG in aqueous humor. Toxoplasma gondii-specific IgM was not detected in the aqueous humor of experimentally inoculated cats before or after inoculation. Immunoglobulin G C values greater than 8 were detected in all 7 experimentally inoculated cats and ranged from 10.4 to 145.5. Immunoglobulin G C values greater than 8 were first detected 4 to 8 weeks after T gondii inoculation and were undetectable by week 16 after inoculation. Immunoglobulin A C values greater than 8 were detected in 4 of 7 cats and ranged from 12.7 to 264.3. Immunoglobulin A C values greater than 8 were first detected 4 to 8 weeks after inoculation, and were detected in 2 cats during week 20 after inoculation. It was concluded that some cats infected with T gondii develop detectable concentrations of T gondii-specific IgA in aqueous humor.

Arterial blood samples were obtained at rest, just before, and 5 minutes after a 704-m race, to quantify changes in hematologic variables, plasma electrolyte and protein concentrations, osmolality, and acid/base variables. Changes in plasma volume were estimated from the change in plasma protein concentration. Immediately prior to the race, plasma volume decreased by 10% from rest and total circulating RBC volume increased by 60%, attributable to increased RBC number rather than size. Increases in blood volume (VB) by 24% and PCV by 29% also were detected before the race. Five minutes after the race, plasma volume was 21% below the resting value and total circulating RBC volume had increased 73% above the resting value, resulting in a 40% increase in PCV. Contraction of the spleen appeared responsible for increased PCV and VB before the race and maintenance of VB after the race. Plasma chloride concentration was the same before and after the race; the chloride content of the plasma decreased by the same fraction (22%) as did the plasma volume, indicating Cl- loss from the plasma. Plasma Na+ content decreased by a smaller fraction (13%), causing Na+ concentration to increase from 151 mEq/L at rest to 167 mEq/L after the race. Assuming that Na+ concentration was the same throughout the extracellular fluid, H20 likely moved into the intracellular compartment. As a consequence of these changes, the inorganic strong ion difference in plasma increased by about 16 mEq/L, tending to minimize the acid/base disturbance induced by the 33 mEq/L increase in lactate concentration. Results indicated that the physiologic changes taking effect during strenuous sprint exercise in Greyhounds enhance blood volume and aid in acid/base homeostasis, both of which are adaptive for this type of exercise.

Ocular biometry, using A-scan ultrasonography and ultrasonographic pachymetry, was performed in 52 Samoyeds, 2 months to 13 years old, without intraocular or systemic diseases. Furthermore, the relative depth of the opening of the ciliary cleft was estimated from goniophotographs. The values were analyzed, and statistical models of changes in ocular distances with increasing age were identified. It was found that the changes in corneal thickness, axial anterior chamber depth, lens thickness, relative lens position, length of the vitreous body, and axial length could best be described by 1 of the 2 nonlinear models (...). The course began with a period of rapid increase, after which the ocular distance either increased at a progressively slower rate toward infinity (corneal and lens thickness) or to a finite limit (relative lens position and axial length), or ceased to grow and finally started to decrease toward minus infinity (axial anterior chamber depth and length of the vitreous body). However, suitable model for determining relative depth of the opening of the ciliary cleft could not be established. Results indicated that age-related changes, mainly in lens thickness, cause a shallow anterior chamber, and it was suggested that this may be of importance for development of a relative pupillary block and, thus, primary angle-closure glaucoma, at least in preconditioned eyes of Samoyeds.

Exertion has an effect on plasma, serum, and/or urine prostanoid concentrations in many species. We investigated the effect of exercise intensity on plasma prostaglandin concentrations during and after exercise in horses. Six Thoroughbreds completed 4 trials: 3 exercise trials (low-, medium-, and high-speed) and 1 nonexercise (control) trial on a high-speed treadmill. Blood samples were collected from a jugular catheter before, during and after exercise. The PCV and blood lactate, plasma protein, plasma prostacyclin (6-keto-PGF1 alpha), thromboxane B2 (TXB2), and prostaglandin E2 (PGE2) concentrations were measured before, during, and after exercise. Exercise significantly (P = 0.001) increased plasma TXB2 concentration during and after exercise in the low-, medium-, and high-speed trials, although effect of exercise intensity was not detected. Exercise was associated with an increase in PCV and blood lactate and plasma protein concentrations. There was no effect of exercise on plasma 6-keto-PGF1 alpha concentrations; PGE2 was not detected in plasma from any horse in any trial.

The effect of oxytetracycline (OTC) on bovine blood mononuclear cells and neutrophil functions was examined in vitro. Neutrophil functions tested include respiratory burst, peroxidase, and antibacterial activities. Neutrophils were treated with OTC (10 to 1,500 > microgram/ml) before exposure to either opsonized zymosan or bacteria. A dose-response inhibition of antibacterial activity to high concentrations of OTC (500 to 1,000 microgram/ml) was observed. Beginning at a concentration of 15 microgram/ml, OTC treatment of neutrophil Iysates resulted in decreased peroxidase activity. A dose response was not observed. In contrast, respiratory burst, measured by nitroblue tetrazolium dye reduction, increased after OTC exposure, but only at high concentrations (500 and 1,000 microgram/ml) of OTC. Mitogen-induced proliferation of blood mononuclear cells cocultured with OTC and concanavalin A, phytohemagglutinin-P, or pokeweed mitogen was inhibited at an OTC concentration of 100 microgram/ml at 48 and 72 hours of culture. These results indicate that blood mononuclear cells are more sensitive to the inhibitory effects of OTC than are neutrophils. Furthermore, the OTC-mediated inhibition of neutrophil antimicrobial activity is inversely related to the increase in nitroblue tetrazolium reduction. This suggests that OTC is uncoupling the hexose monophosphate shunt from production of secreted oxygen radicals. These results also suggest that the peroxidase enzyme system has a large biological reserve capacity.

Six horses, highly trained for dressage competition, were used to study the stride kinematics of the walk, and to compare the kinematics of the collected, medium, and extended walks. Horses were filmed in a sagittal plane at a rate of 150 frames/s; temporal, linear, and angular data were extracted from the films. Results of ANOVA and Duncan's multiple range test indicated that the speed of the collected walk (1.37 m/s) was significantly (P < 0.01) slower than that of the medium (1.73 m/s) and extended (1.82 m/s) walks, values for which were not significantly different from each other. The increase in speed was associated with a significant increase in stride length, from 157 cm in the collected walk to 193 am in the extended walk. This was a result of an increase in the over-tracking distance, whereas there was no significant difference in the distance between lateral placements of the limbs. Stride duration decreased (P < 0.01) from the collected walk (1,159 ms) to the extended walk (1,064 ms). Angles of the metacarpal and metatarsal segments, measured on the palmar/plantar aspect, were higher at impact and lower at lift off in the collected than in the extended walk (P < 0.01). This indicated greater range of angular motion of this segment during the stance phase in the extended walk. Only 1 of the 6 horses had a regular 4-beat rhythm of the footfalls, with equal time elapsing between the lateral and diagonal footfalls.

We examined the electromyographic activity of the costal portion of the diaphragm and the transverse abdominal and external oblique muscles in 6 chronically instrumented awake adult horses during eupneic breathing during 2 levels of hypercapnia (fractional concentration of inspired CO2; FICO2 = 0.4 and 0.6), and during 2 levels of hypocapnic hypoxia (FIO2 = 0.15 and 0.12). Using the inert gas technique, we also measured the end-expiratory lung volumes of the 6 horses during eupnea, 6% CO2 challenge, and 12% O2 breathing. During eupneic breathing, phasic electrical activity of these 3 muscles was always present and was preceded by the onset of mechanical flow. At progressive levels of hypercapnia, the magnitude of inspiratory and expiratory electrical activity increased, and for the expiratory muscles, this recruitment coincided with significant (P < 0.05) increases in peak expiratory gastric pressure. However, during hypocapnic hypoxia, differential recruitment patterns of the respiratory muscles were found. The electrical activity of the diaphragm increased in magnitude and occurred sooner relative to the onset of mechanical flow. The magnitude and onset of abdominal expiratory activity failed to increase significantly during these episodes of hyperpnea and this pattern of activity coincided with decrements in peak expiratory gastric pressure. Despite alterations in muscle recruitment patterns during these hyperpneic episodes, end-expiratory lung volume remained unchanged. Thus, we conclude that adult horses respond similarly to awake dogs during peripheral and central chemoreceptor stimulation.