Growth of Pasteurella haemolytica A1 in RPMI 1640 medium containing 0.5% bovine serum albumin (BSA) for 2.5 hours enhanced culture supernatant leukotoxic activity [30,700 +/- 12,900 toxic units/ml, compared with leukotoxic activity of culture supernatants produced in RPMI 1640 medium alone (120 +/- 40 toxic units/ml)]. Gel filtration chromatography of the leukotoxic activity from RPMI 1640 medium supernatants in buffer containing 50 mM NaCl indicated a single leukotoxic activity peak (peak I) eluting near the gel resin molecular mass exclusion limit (estimated molecular mass of approx 8,000 kd). In contrast, culture supernatants produced in RPMI 1640 plus bovine serum albumin medium (RPMI + BSA) had peak I and 2 additional leukotoxic activity peaks (peaks II and III) with estimated molecular mass of approximately 80 and < 30 kd, respectively. All leukotoxic activity peaks were composed of approximately 100-kd molecular mass leukotoxin protomer, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting with a monoclonal antibody against leukotoxin. Subjecting culture supernatant leukotoxic activity produced in RPMI + BSA to gel filtration chromatography in buffer containing 500 mM NaCl or 6M urea resulted in detection of only a single leukotoxic activity peak with estimated approximate molecular mass of 250 and 800 kd, respectively. These findings suggest that P haemolytica exists as a high molecular mass aggregate with low leukotoxic activity which, in the presence of BSA, partially disaggregates to multiple toxin forms with enhanced leukotoxic activity. Some of these leukotoxin forms interact with dextran-based gel resins at low ionic strength.

High molecular weight (MW) hyaluronate (HA) is an integral part of synovial fluid (SF), regulating many important physiologic and pathophysiologic mechanisms. Many of its effects depend on, or are reflected in, the concentration and MW of HA. High-performance liquid chromatography was used to assess simultaneously the concentration and MW of HA in SF obtained from horses with various arthritides: acute traumatic arthritis; chronic traumatic arthritis, including degenerative joint disease (DJD); and infectious arthritis. The size-exclusion column was calibrated, using appropriate HA concentration and MW standards, before the high-performance liquid chromatographic assays of the SF samples. Calibration of the column disclosed that the maximal limit for MW estimation of HA was around 3 million. In control joints, MW of HA ranged from 2 to 3 X 10(6) (mean 2.5 X 10(6)) and did not differ significantly from MW of HA in SF from horses with acute or chronic traumatic arthritis (mean 2 x 10(6); range 1.5 to 3 x 10(6)). Interestingly, a small amount of HA of moderately high MW (approx 1 to 1.5 x 10(6)) was detected in chromatograms of SF from infected joints. This degree of polymerization of SF HA was significantly (P < 0.01) lower, compared with that for control joints. There was no difference in mean (+/- SD) concentration of HA between control joints and joints with acute or chronic traumatic arthritis (0.33 +/- 0.12 g/L vs 0.18 +/- 0.03 g/L or 0.23 +/- 0.12 g/L), indicating that SF HA concentration probably should not be used as a diagnostic marker for the condition. However, the SF HA concentration was significantly (P < 0.01) lower in joints with infectious arthritis (0.07 +/- 0.03 g/L) and in the joints with radiographic evidence of DJD (0.12 +/- 0.01 g/L), compared with control joints.

Collagen type I was purified from equine skin and flexor tendon, and type II collagen was purified from equine articular cartilage. The proteoglycans in these tissues were extracted, using guanidine HCl; the collagens were solubilized, using pepsin digestion, then were selectively precipitated with Nacl. Gel electrophoresis indicated that the precipitates contained only type I or type II collagen. Amino acid analysis indicated that collagen constituted > 97% of the total protein in the precipitates. Hydroxylation of proline was 42.0 t 0.6% (mean SEM) in alpha 1(I) and alpha 2(I), and was 48.1 +/- 1.3% in alpha 1(II) chains. The hydroxylation of lysine was 23.2 +/- 0.7% in alpha 1(I) and 34.1 0.9% in alpha 2(I) chains from tendon, and 49.6 +/- 4.3% in alpha 1(II) chains from cartilage. The cyanogen bromide (CB)-peptide patterns of chromatographically purified equine alpha 2(I) and alpha 1(II) chains were similar to those published previously for rat, bovine, and human alpha 2 and alpha 1 chains. However, the CB-peptide pattern of the equine alpha 1(I) chain resembled the guinea pig alpha 1(I) chain, which has no methionine between CB7 and CB6. Purified equine alpha 1(I)CB7,6 contained no methionine, methionine sulfoxide, or homoserine lactone. Mass of 42.26 kd was determined by use of mass spectrometry, and N-terminal sequence analysis established that the first 12 amino acids of this CB7,6 were identical to the sequence of human alpha 1(I)CB7. Because of this species specific difference in structure of the alpha 1(I) chain, equine Cb-peptides should be used as standards in studies of variations in the proportions of type I and type II collagens in equine tissues expressing the phenotype of fibrous tissue and cartilage.

Dispositions of caffeine and antipyrine were compared as indicators of decreasing hepatic function in dogs with experimentally induced progressive liver disease. Dimethylnitrosamine, a hepatospecific toxin, was administered orally to 16 dogs; 6 dogs served as controls (group 1). Three classes of liver disease were defined by histologic features: mild (group 2; n = 5), moderate (group 3; n = 6), and severe (group 4; n = 5). Disposition of antipyrine, and 24 hours later, caffeine was studied 3 weeks after the last dose of toxin in each dog. For both drugs, rapid IV administration of 20 mg/kg of body weight was administered and serum samples were obtained at intervals for determination of at least 5 terminal-phase drug half-lives. For both drugs, clearance and mean residence time differed among groups (P less than or equal to 0.01). Clearance of antipyrine and caffeine was decreased in groups 3 and 4, compared with groups 1 and 2. Antipyrine and caffeine mean residence times were longer in group-3 dogs, compared with dogs of groups 1 and 2. Correction of caffeine and antipyrine clearances for hepatic weight increased discrimination between groups 3 and 4. The clearance and mean residence time ratios of antipyrine to caffeine were calculated for each group and, when compared with values for group-1 dogs, were used to test for differences between the 2 drugs in response to disease. Ratios did not differ among groups. These results indicate that the disposition of antipyrine and caffeine may change similarly with progression of dimethylnitrosamine-induced liver disease.

A specific, sensitive, reverse-phase high-performance liquid chromatographic assay for acepromazine, with analytic sensitivity as low as 5 ng/ml of plasma, and electrochemical detection with an oxidation potential of 0.7 V, was used to study the pharmacokinetics of acepromazine given at a dosage of 0.15 mg/kg of body weight in horses. The relation between effect and pharmacokinetics of the drug was examined. The effects studied included those on blood pressure, pulse, PCV, measures of respiration function, and sedation. Intravenously administered doses led to a biphasic concentration decay pattern with an alpha-phase distribution half-life of < 3 minutes. The beta-phase half-life was in the range of 50 to 150 minutes. The CNS effects peaked at 20 minutes after administration, and the hemodynamic effects peaked at 100 minutes. In all horses, the most sensitive variable was the PCV, which decreased by up to 20% (P < 0.0001). Systolic, diastolic, and mean blood pressures decreased (P < 0.0001); heart rate was unchanged (P > 0.05). Neither blood gas tensions nor blood pH changed noticeably (P > 0.05). In all horses studied, acepromazine had a significant (P < 0.0001) sedative effect, as observed by posture and alertness. None of the observed pharmacodynamic effects correlated well with plasma acepromazine concentration. These effects persisted beyond the time of detectable acepromazine concentration, indicating that they might be caused by active metabolites, or that their timing could result from complex pharmacokinetic compartment influences.