The growth hormone (GH) secretagogue activity of variable dosages of clonidine (16.5, 50, 150, and 450 microgram/kg of body weight), given orally mixed with the daily food ration, was evaluated in young and old dogs. Significant (P < 0.05) increase in plasma GH concentration was detected at all dosages tested in young dogs and in response to all but the lowest dose tested in the old dogs fed the clonidine-containing diet. Old dogs had plasma GH concentration that exceeded that of young dogs when higher doses of clonidine were used. A clonidine (100 microgram/kg)-supplemented diet was fed to middle-aged dogs twice daily for 30 days. Significant (P < 0.01) increase of plasma GH concentration was observed on the first day of the feeding trial, but was undetectable by day 30. After feeding the clonidine-enhanced diet for 30 days, the effects on thymic morphology were variable, and there was no effect on plasma thymulin titer. Clonidine-fed dogs had significantly increased lymphocyte blastogenic responsiveness to mitogens, compared with that of control dogs, when evaluated as stimulation index.

Samples of pleural fluid from 20 horses with effusive pleural diseases of various causes were evaluated; samples from 19 horses were used for the study. There were differences for pH (P = 0.001) and partial pressure of oxygen (P(O2)) between arterial blood and nonseptic pleural fluid (P = 0.0491), but there were no differences for pH, P(O2), partial pressure of carbon dioxide (P(CO2)) and concentrations of bicarbonate (HCO3-), lactate, and glucose between venous blood and nonseptic pleural fluid. Paired comparisons of venous blood and nonseptic pleural fluid from the same horse indicated no differences. There were differences (P = 0.0001, each) for pH, P(O2), P(CO2), and concentrations of HCO3- between arterial blood and septic pleural fluid. Differences also existed for pH (P = 0.0001), P(CO2) (P = 0.0003), and concentrations of HCO3- (P = 0.0001), lactate (P = 0.0051), and glucose (P = 0.0001) between venous blood and septic pleural fluid. Difference was not found for values of P(O2) between venous blood and septic pleural fluid, although 4 samples of septic pleural fluid contained virtually no oxygen. Paired comparisons of venous blood and septic pleural fluid from the same horse revealed differences (P < 0.05) for all values, except those for P(O2). These alterations suggested functional and physical compartmentalization that separated septic and healthy tissue. Compartmentalization and microenvironmental factors at the site of infection should be considered when developing therapeutic strategies for horses with septic pleural disease.

A study was conducted to determine whether subcomponent proteins (previously identified as BCSP20, BCSP3l, and BCSP45, and the corresponding recombinant proteins rBCSP20, rBCSP31, and rBCSP45) that were recovered from the cell surface of Brucella abortus strain 19 were immunogenic and protective for mice when compared with Brucella cell surface protein (BCSP) and with a proteinase K-treated lipopolysaccharide (PKLPS) extracted from B abortus strain 2308. Protection was evaluated after challenge exposure with a virulent culture of B abortus strain 2308, using CD-1 or BALB/c mice or both inoculated with vaccines of various combinations and concentrations, with and without PKLPS or BCSP. Protection was assessed by enumeration of splenic colony-forming units, reduced mean splenic weight relative to controls, and the relative serologic responses (immune response) in an ELISA. The general results indicate that BCSP, PKLPS, BCSP20, and BCSP31 are immunogenic or protective or both. Protectiveness was not observed for each of the recombinant proteins; however, results from the combined recombinant protein vaccine study suggest the immunogenicity of the recombinant proteins. The apparent immune-inducing properties of BCSP20 and BCSP3l are thought to be attributable to the presence of an immunogenic and protective BCSP fraction (possibly lipopolysaccharide) still associated. Serologic results support our conclusion that each of the recombinant protein vaccines did not induce a protective response comparable to that of BCSP or PKLPS, even when the subcomponents were combined. Although the results suggest that the subcomponents of BCSP apparently induced partial protection, they are thought to be only a part of the antigens contained in BCSP that influence the serologic response. Our findings may serve as an experimental model to determine the mechanisms involved in the protective responses induced by Brucella antigens.

Immunoturbidimetric determination of serum IgG concentration in foals was compared with the reference methods of single radial immunodiffusion and serum protein electrophoresis. High positive correlations were discovered when the technique was compared with either of these reference methods. The zinc sulfate turbidity test for serum IgG estimation was also evaluated. Although a positive correlation was discovered when the latter method was compared with reference methods, it was not as strong as the correlation between reference methods and the immunoturbidimetric method. The immunoturbidimetric method used in this study is specific and precise for equine serum IgG determination. It is rapid and, thus, is advantageous when timely evaluation of critically ill foals is necessary. The technique should be adaptable to various spectrophotometers and microcomputers for widespread application in veterinary medicine.

Seventeen sows were fed 1,000 Toxoplasma gondii oocysts of isolates GT-1 or PT-1 at 32 to 92 days of gestation, and the products of conception were examined for T gondii antibodies and parasites. Twelve of these sows were euthanatized near term between 21 and 62 days after being fed T gondii; fetal body fluids or fetal sera were examined for agglutinating T gondii antibodies, and tissues were bioassayed in mice for T gondii parasites. Six sows produced pigs that had been transplacentally infected with T gondii; one of them aborted a T gondii-infected fetus 17 days after ingesting oocytes. Agglutinating antibodies were detected in fetuses infected in utero, but transplacental transfer of T gondii antibodies was not observed in noninfected fetuses. Transcolostrally acquired T gondii antibodies disappeared by 3 months of age. Diagnosis of transplacental toxoplasmosis was confirmed on the basis of detection of T gondii organisms in fetal tissues by use of histologic examination and bioassay in mice. In conclusion, finding of T gondii antibodies in body fluids could serve as a rapid screening test for transplacental T gondii infection in pigs.

Polioencephalomalacia (PEM) was induced in calves by feeding a semipurified, low-roughage diet of variable copper and molybdenum composition. Two formulations resulting in Cu-insufficient and Cu-sufficient forms of the diet were fed (n = 10 and 4 calves, respectively); both diets induced PEM. Clinical signs of disease developed as early as 15 days after transition to the experimental diets and included impaired vision, decreased response to external stimuli, and abnormal gait. Grossly evident cerebrocortical lesions consisted of laminar areas of cavitation and/or autofluorescence seen under UV illumination. Hepatic Cu concentration was decreased in calves fed the Cu-insufficient diet, but not below normal range. During the course of feeding either diet, rumen pH decreased, rumen volatile fatty acid concentrations increased, rumen and blood lactic acid concentrations increased, and rumen and plasma thiamine concentrations increased. The thiamine pyrophosphate effect on erythrocyte transketolase activitywas unaltered in calves of either diet group. This nutritionally induced form of PEM does not appear to be related to Cu deficiency or reduction in plasmaor rumen thiamine concentration.

We tested the hypothesis that lymphocytes from swine with susceptibility to malignant hyperthermia (MH) had calcium extrusion activity higher than unaffected swine. Cytoplasmic concentration of ionized calcium was determined by use of dual emission spectrofluorometry and measurement of the ratio of free to calcium-bound form of the fluorescent calcium dye indo-1. Net calcium accumulation and unidirectional calcium extrusion rate were dependent on intracellular calcium concentration. Calcium extrusion from calcium-loaded lymphocytes was monitored while calcium influx was inhibited by suspending the cells in calcium-free medium with a calcium chelator. Net calcium accumulation of untreated lymphocytes was monitored in calcium-replete medium. A novel method of calculation of ionized calcium was used. This method confirmed our previous findings of lower ionized calcium concentration (86 +/- 40 and 370 +/- 216 nmol/L; P < 0.01) and slower rates of calcium accumulation (39 +/- 16 and 127 +/- 52 nmol/L/min) in untreated lymphocytes from MH-susceptible swine compared with controls. These changes were attributable to calcium extrusion activity two- to three-fold higher in lymphocytes of MH-susceptible swine (154 +/- 36 and 408 +/- 47 nmol/L/min at 175 nmol/L; 972 +/- 111 and 1,690 +/- 505 nmol/L/min at 425 nmol/L). These data were compatible with our model of higher calcium extrusion activity being a compensatory adaptation of MH-susceptible swine lymphocytes to their hypersensitivity to stimuli that increase cytoplasmic calcium concentration.

High-performance liquid chromatography (HPLC) was used to determine the phospholipid (PL) composition of ovine, equine, bovine, porcine, and canine RBC membranes. Procedural modifications of established techniques provided for separation of 7 PL within a 15- to 20-minute sample run. Significant (P < 0.05) differences were detected in RBC membrane PL composition among the various species. The concern for physiologic properties associated with hemolysis and/or sedimentation rate must include evaluation of differences in the PL bilayer structure.

Logistic regression was used to develop models predicting preweaning survival in 334 neonatal swine. Measured risk factors included birth weight, litter size (live born), dam parity, serum IgG concentration, serum ELISA titers recognizing common gram-negative core antigens, and serum concentrations of the third component of complement. Larger birth weights were associated with increased probability of preweaning survival. The highest mortality was observed in litters with more than 12 pigs. Pigs with serum concentration of the third component of complement (C3) in the lowest stratum, < 20% adult pooled C3 standard (APC3), had reduced mortality, compared with high (> 38% APC3) and middle (20 to 38% APC3) groups. Associations between all other variables, including total serum IgG concentration and preweaning survival were not significant. Few pigs had hypogammaglobulinemia, < 3% of the study population had serum IgG concentrations < 1 g/dl. Of all measured variables, only birth weight and dam parity were significant predictors of preweaning gain. Larger pigs and pigs born to third or greater parity dams had more preweaning gain than other pigs.

The pharmacokinetics of flunixin were studied in 6 adult lactating cattle after administration of single IV and IM doses at 1.1 mg/kg of body weight. A crossover design was used, with route of first administration in each cow determined randomly. Plasma and milk concentrations of total flunixin were determined by use of high-pressure liquid chromatography, using an assay with a lower limit of detection of 50 ng of flunixin/ml. The pharmacokinetics of flunixin were best described by a 2-compartment, open model. After IV administration, mean plasma flunixin concentrations rapidly decreased from initial concentrations of > 10 micrograms/ml to nondetectable concentrations at 12 hours after administration. The distribution phase was short (t1/2 alpha, harmonic mean = 0.16 hours) and the elimination phase was more prolonged (t1/2 beta, harmonic mean = 3.14 hours). Mean +/- SD clearance after IV administration was 2.51 +/- 0.96 ml/kg/min. After IM administration, the harmonic mean for the elimination phase (t1/2 beta) was prolonged at 5.20 hours. Bioavailability after IM dosing gave a mean +/- SD (n = 5) of 76.0 +/- 28.0%. Adult lactating cows (n = 6) were challenge inoculated with endotoxin as a model of acute coliform mastitis. After multiple administration (total of 7 doses; first IV, remainder IM) of 1.1 mg/kg doses of flunixin at 8-hour intervals, plasma flunixin concentrations were approximately 1 microgram/ml at 2 hours after each dosing and 0.5 microgram/ml just prior to each dosing. Flunixin was not detected in milk at any sampling during the study. Flunixin concentrations necessary to induce therapeutic effects in cattle are unknown. Results of our study indicate that administration of 1.1 mg/kg doses of flunixin meglumine at 8-hour intervals would produce plasma concentrations similar to those demonstrated to be effective clinically in treatment of equine musculoskeletal disorders and colic.