The cytotoxic effect of Moraxella bovis 118F on bovine neutrophils was evaluated and characterized by use of a 51Cr release assay. Neutrophils harvested from healthy adult cattle were labeled with 51Cr. The leukocidic activity produced by M bovis 118F, a hemolytic strain of M bovis, was heat-labile. A live culture of strain 118F, at a ratio of 100 bacteria/neutrophil, released 97.7% of the 51Cr from labeled neutrophils. Neither a heat-killed preparation of M bovis 118F nor a live or heat-killed preparation of M bovis IBH63 (a nonhemolytic and nonpathogenic strain) induced significant (P > 0.05) release of 51Cr. Moraxella bovis 118F broth culture filtrates prepared for evaluation of leukocidic activity also were evaluated for hemolytic activity. These 2 toxic activities had several characteristics in common. Both were filterable, heat-labile, produced by a hemolytic strain, and were released during early logarithmic phase growth from broth cultures. Leukocidic and hemolytic activities were protected from degradation by phenylmethyl sulfonyl fluoride, a serine protease inhibitor. Leukocidic and hemolytic activities were dependent on calcium ions. Filtrate resulted in 54.1% 51Cr release from labeled neutrophils and contained 646.7 hemolytic U/ml, respectively, when saline (0.85% NaCl) + 10 mM CaCl2 solution was used as diluent. Neither saline solution nor saline + 10 mM MgCl2 solution supported leukocidic or hemolytic activity. Serum, obtained from several calves 10 to 38 days after M bovis inoculation, substantially neutralized leukocidic and hemolytic activities, compared with paired preinoculation serum samples. In addition, no significant difference (P > 0.05) was detected when the ability of each calf's postinfection serum to neutralize leukocidic activity was compared with the ability of the serum to neutralize hemolytic activity.

Canine gastric dilatation-volvulus (GDV) is a naturally acquired condition of large-breed dogs primarily and is associated with high mortality. The clinical course suggests that reperfusion injury may be important in the pathogenesis of GDV. To evaluate the role of xanthine oxidase and iron-dependent lipid peroxidation (which are purported mechanisms of reperfusion injury) in the pathogenesis of GDV-related mortality, we created experimental GDV in 21 dogs. These dogs were then treated with either allopurinol (a xanthine oxidase inhibitor), U74006F (an experimental lipid peroxidation inhibitor), or saline solution (NaCl, 0.85%). Three of 8 dogs died in the allopurinol-treated group, none of 5 died in the U74006F-treated group, and 4 of 8 died in the saline solution-treated group. Tissue malondialdehyde concentration, a nonspecific indicator of lipid peroxidation, was significantly (P < 0.05) greater in the duodenum, jejunum, colon, liver, and pancreas of the saline-solution treated and allopurinol-treated dogs than in the same tissues of the U74006F-treated dogs after surgical correction of the GDV (ie, during reperfusion), compared with malondialdehyde concentrations determined before inducing GDV. The results of this study support the concept that lipid peroxidation associated with reperfusion injury is important in the pathogenesis and high mortality of canine GDV. Furthermore, this lipid peroxidation and mortality may be preventable by appropriate and timely treatment.

Ceftiofur hydrochloride was tested for effectiveness against induced colibacillosis in neonatal swine. In this model, pigs < 12 hours old were inoculated via stomach tube with a virulent, K99+, nalidixic acid-resistant strain of Escherichia coli. Six hours after challenge exposure, 1 dose of ceftiofur was administered either IM or orally in experiment 1 and orally only in experiment 2. Mortality, shedding of bacteria, fecal consistency scores, and body weight changes were monitored for 10 days. In experiment 1 (n = 383 pigs), all treatments at dosage that ranged between 0.5 and 64.0 mg of ceftiofur/kg of body weight significantly (P < 0.001) reduced mortality, bacterial shedding, and diarrhea and increased weight gain, compared with findings in untreated controls. There were no detectable differences between oral and IM routes, except that there was greater reduction in bacteria shedding associated with the oral route of administration. In experiment 2 (n = 505 pigs), ceftiofur was administered orally either once at 6 hours after challenge exposure or twice at 6 and at 48 hours after the first dose. Dosage of ceftiofur was 0, 5, 10, 20, 30, or 60 mg/kg administered once, or half the same dose was administered at each of 2 times. At the optimal dosage (10 mg/kg), a single dose was as effective as 2 doses. The single administration at all dosages reduced mortality, bacterial shedding, and diarrhea scores and increased body weight gain, compared with findings in untreated pigs (P < 0.01). In this induced infection model, the optimal treatment dosage was determined to be 10 mg/kg administered once.

The feasibility of renal arterial infusion of nonbiodegradable microspheres as a model of chronic renal disease in dogs was evaluated. Resin-coated, styrene-divinyl benzene copolymer microspheres were infused into the kidneys of healthy adult Beagles by direct injections of both renal arteries in a single surgical procedure. Injections of 25-micrometer diameter microspheres had minimal effect on either the clinical status or serum values of the dogs. Histologic examination revealed the majority of the microspheres lodged within the capillary beds of the glomeruli, and little change to the kidneys. However, injections of 50-micrometer diameter microspheres caused significant increases in serum concentrations of urea nitrogen and creatinine. Histologically, the larger microspheres obstructed afferent arterioles and small arteries, which caused diffuse glomerular necrosis and nephron damage. With doses ranging from 1 to 3 million microspheres/dog, a correlation between the quantity of microspheres injected and severity of renal damage was observed. The optimal dose for producing a model of moderate renal disease was determined to be 1.8 million microspheres/dog (0.9 million microspheres/kidney). During long-term studies, microsphere-injected dogs fed a moderately restricted protein ration remained relatively azotemic, compared with control dogs on the identical ration. During the 5-month postsurgical period, the serum urea nitrogen concentration averaged 18.41 +/- 1.59 mg/dl (mean +/- SE) for the microsphere-injected dogs vs 9.31 +/-0.38 for the control dogs (P < 0.001). Similarly, the mean serum creatinine value was significantly higher (P = 0.020) for the microsphere-injected dogs, compared with the controls (1.23 +/- 0.12 mg/dl vs 0.94 +/- 0.03). In addition, the difference in mean endogenous creatinine clearance rates was statistically significant (microsphere-injected 1.02 0.05 ml/min/kg, vs control 1.53 +/- 0.06, P < 0.001).

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.

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.

L-lactic acid and D,L-lactic acid infusion in ponies resulted in metabolic acidosis with high anion gap (AG). Increased AG was explained entirely by increased blood L- and D-lactate concentrations. Hydrochloric acid infusion caused metabolic acidosis with decreased AG. Saline (NaCl) infusion caused mild metabolic acidosis, with no significant change in AG. Plasma K+ concentration was decreased by all types of infusions, with a maximum of 0.50, 0.25, 0.40, 0.50 mmol/L below baseline at the end of infusion in the L-lactic acid-, D,L-lactic acid-, HCl-, and NaCl-infused ponies, respectively. Only hydrochloric acid had a tendency to increase plasma K+ concentration. Hypophosphatemia developed in NaCl- and HCl-infused ponies, but not in the D,L-lactic acid-infused ponies. Serum inorganic phosphate concentration in L-lactic acid-infused ponies increased initially, but was significantly (P < 0.05) lower than values in the other ponies at 4 hours after onset of infusion. In ponies, the effect of acidemia on plasma K+ and serum inorganic phosphate concentrations was similar to that reported for other species. Changes were small in magnitude and depended on the nature of the acid anion. Results indicate that large changes in plasma K+ and serum inorganic phosphate concentrations during acidosis are probably not a direct result of acidemia.

Streptococcal species isolated from dairy cows with clinical mastitis were obtained from mastitis research workers in Florida, Louisiana, New York, Vermont, Washington, and West Virginia. Seventy-one streptococcal isolates were tested, including 39 strains of Streptococcus agalactiae, 21 strains of S dysgalactiae, and 11 strains of S uberis. The minimal inhibitory concentration of erythromycin, lincomycin, oxytetracycline, penicillin, spectinomycin, streptomycin, and tetracycline was determined for each isolate. Differences were not detected among strains with respect to geographic origin. None of the strains was resistant to penicillin. Lincomycin was the next most effective antimicrobial, with only 2 resistant strains of each streptococcal species. There were no differences among the streptococcal species with respect to resistance to either penicillin or lincomycin. Streptococcus uberis was more likely to be resistant to erythromycin than were S agalactiae and S dysgalactiae (P < 0.02). Streptococcus agalactiae and S uberis had similar distributions for resistance to oxytetracycline, tetracycline, spectinomycin, and streptomycin. Strains of S dysgalactiae were more likely to have intermediate resistance to oxytetracycline and streptomycin than were strains of S agalactiae and S uberis, which were highly resistant to oxytetracycline and streptomycin (P < 0.001). Differences were not detected among the streptococcal species with respect to resistance to spectinomycin. Resistance to multiple antimicrobials was observed in all streptococcal species tested. Although S dysgalactiae appeared to have a greater percentage of strains (73%) that were resistant to multiple antimicrobials than did S agalactiae (31%) or S uberis (45%), differences were not statistically significant.

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.

The in vivo effects of a single prophylactic dose of recombinant bovine interferon (rBoIFN)-alphaI1 in calves with salmonellosis were investigated, using a Salmonella typhimurium infection model. Treatment with rBoIFN-alphaI1 reduced the degree of septicemia compared with that in control groups, and, in one experiment, using disease of reduced severity, body temperature was lower in treated calves than in controls.