Microscopic examination of the nasal mucosa of clinically normal specific-pathogen-free pigs and of toxicogenic type-D Pasteurella multocida toxin challenge-exposed specific-pathogen-free pigs indicated that the surface epithelium in pigs of both groups was microscopically normal; erosions or appreciable inflammatory changes were not evident. In pigs of both groups and in aU 3 regions of the nasal cavity, the endothelial lining of all blood vessels appeared normal without detectable changes to the walls at postinoculation day 10. Vascular injury in the cartilage or the bone was not discernible in control or challenge-exposed pigs. There were marked differences in the osseous structures of the conchae when the 2 groups were compared. In control pigs, active bone formation and remodeling were observed, and the septal cartilage was normal. In toxin challenge-exposed pigs, there likewise was normal bone formation and remodeling in the vestibular region, and the septal cartilage was normal. In marked contrast, conspicuous changes were observed in the osseous core of the conchae of the respiratory and, sometimes, the olfactory regions. These changes consisted of bone necrosis and resorption by large numbers of osteoclasts with variable replacement by dense mesenchymal stroma, which resulted in conchal atrophy. In the absence of any discernible damage or injury (angiopathy) to the nasal vessels, it appears that the action of the dermonecrotoxin of P multocida serotype D is on the most active osteoblasts and the associated organic matrix of the bone, with subsequent disruption of normal bone formation and remodeling of the nasal conchae.

Ouabain, a cardiac glycoside, binds to the Na+-K+i-adenosine triphosphatase (Na+ pump) and prevents active transport of Na+ and K+ across cell membranes. We used [3H]ouabain to quantify the number and affinity of Na+ pumps in skeletal muscle from Quarter Horses with the muscular disorder hyperkalemic periodic paralysis (HYPP). [3H]Ouabain-binding properties of gluteal muscle from clinically normal and affected horses were used to determine whether altered Na+ pump number or affinity could contribute to the pathologic features of muscle in affected horses. Foals and adult horses with HYPP were compared with age-matched clinically normal horses. The number of [3H]ouabain-binding sites in adult gluteal muscle was not different between the 2 types of horses (85.7 +/- 8.9 pmol of [3H]ouabain-binding sites/g [wet muscle weight] in horses with HYPP vs 100.2 +/- 8.8 pmol/g in clinically normal adult horses). Gluteal muscles in HYPP-affected and clinically normal foals also contained a similar number of [3H]ouabain-binding sites (222.3 +/- 21.0 pmol/g vs 225.3 +/- 24.2 pmol/g, respectively). The affinity of these binding sites for ouabain was not different, between adults or foals, in clinically normal or affected horses. Our results indicate that membrane events underlying the periodic episodes of paralysis in horses with HYPP are not attributable to quantitative changes in Na+ pump number or affinity. Our data cannot exclude the possibility that the specific activity of the Na+ pump is altered in muscle from HYPP-affected horses.

One hundred eight milking goats from a dairy that had been using a modified caprine arthritis-encephalitis virus (CAEV) eradication program were tested for CAEV antibodies by serologic methods and for proviral CAEV DNA by use of polymerase chain reaction (PCR) technology. All goats were free of clinical symptoms of CAEV infection. Twenty-seven of the 108 goats were considered seropositive, on the basis of ELISA results. Proviral CAEV DNA was detected, using PCR techniques, in mononuclear leukocytes in blood samples obtained from 25 of the these 27 seropositive goats. Twenty of the 81 seronegative goats also had positive PCR test results. Ten of these goats seroconverted by 8 months later, and virus was readily isolated from mononuclear leukocytes in venous blood samples after the goats had seroconverted. Virus was also isolated from mononuclear leukocytes in blood samples collected from 4 of 11 goats that were seronegative, but had positive PCR test results. These results indicated that seroconversion can be delayed for many months following natural infection with CAEV. Delayed seroconversion appears to be a feature of CAEV infection, which may have direct implications for CAEV eradication programs and epidemiologic studies that rely on serologic methods to detect infected goats.

We examined the effect of infusion of lipopolysaccharide (LPS) on serum tumor necrosis factor alpha (TNF alpha) concentration and clinical attitude in 2- to 3-day-old colostrum-fed (CF) and colostrum-deprived (CD) foals. Eleven CF and 8 CD neonatal foals were given a bolus IV infusion of Escherichia coli 055:B5 lipopolysaccharide (0.5 microgram/kg of body weight) in sterile saline (0.9% NaCl) solution. Four CF and 2 CD foals were given saline solution alone. Serum IgG concentration and serum anti-LPS IGG(T) antibody titer were determined for each foal prior to infusion. A depression index was used to score clinical abnormalities. Serum TNF alpha concentration was estimated by use of an in vitro cytotoxicity bioassay that used WEHI 164 clone 13 cells as targets. The cytotoxic serum factor was identified as TNF alpha by immunoprecipitation with caprine antisera raised against the 15 NH2-terminal amino acids of human TNF alpha. Tumor necrosis factor alpha was not detected in any preinfusion serum samples nor in any samples from foals given saline solution alone. Serum TNF alpha concentration increased in all LPS-infused foals and peaked between 60 and 90 minutes after infusion. Serum TNF alpha concentrations, expressed as mean percentage of peak serum TNF alpha concentration, persisted longer in CD foals given LPS than in CF foals given LPS. All LPS-infused foals displayed clinical signs of endotoxemia, but mean depression index scores of the CF and CD foals given LPS were not significantly different at any time. Serum TNF alpha concentrations were correlated with depression index scores in both LPS-infused groups. Mean rectal temperature increased by 1 hour and remained high for 4 hours after infusion in CF foals given LPS. Mean rectal temperature in CD foals given LPS was significantly less than that for CF foals given LPS 1 and 2 hours after infusion and was higher than mean rectal temperature prior to infusion 3 and 4 hours after.

The antibiotic polymyxin B sulfate is a cationic polypeptide with a unique cyclical configuration and distinct cationic characteristics. In this investigation, polymyxin B was evaluated to determine its ability to prevent synthesis of lactic acid and tumor necrosis factor-alpha (TNF-alpha) by lipopolysaccharide-stimulated strain RAW 2647 macrophage-like cell populations. In this context, gradient concentrations of polymyxin B were formulated in the presence of fixed concentrations of lipopolysaccharide fractions from Escherichia coli (B4:0111), E. coli (J5), Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella minnesota, and S. typhimurium (Re). Quantitation of TNF-alpha was established by the application of a tissue culture-based biological assay system, using the WEHI 164 clone 13 indicator cell line. Investigations also included evaluation of the ability of gradient concentrations of lipopolysaccharide fractions from E. coli (B4:0111), E. coli (J5), K. pneumoniae, P. aeruginosa, S. minnesota, and S. typhimurium (Re) to form a complex with polymyxin B. This was established through application of high-performance thin-layer chromatography techniques. On the basis of the known molecular characteristics of lipopolysaccharide, its lipid A-core subfractions, and polymyxin B, these results imply that cytoprotective properties of polymyxin B are attributable to direct interaction and subsequent complex formation. More specifically, the mechanism by which polymyxin B exerts affinity for lipopolysaccharide fractions is proposed to occur through attractive ionic interactions established between the cationic diaminobutyric acid residues of polymyxin B and the mono- or diphosphate group(s) of the lipid A-core moiety. It is highly probable that this molecular phenomenon is accompanied by hydrophobic interactions established between the terminal methyloctanoyl or methylheptanoyl groups of polymyxin B and the saturated carbon chains of the lipid A-core subfraction of lipopolysaccharide fractions.

Foremilk, residual milk, and blood samples were studied for 10 days during acute mastitis episodes induced by endotoxin infused via the teat canal. Quarter milk and blood samples were collected frequently for 3 days after the infusion and thereafter once or twice daily. Leukocyte concentration in milk and blood was determined by flow cytometry. Within 2 hours after infusion of the endotoxin, clinical mastitis was observed. Total leukocyte concentration and proportion of neutrophils increased significantly (P < 0.05) by postinfusion hour (PIH) 2 in foremilk and by PIH 4 in residual milk. From PIH 2, serum albumin content and N-acetyl-beta-D-glucosaminidase activity were significantly increased in both fractions. Neutrophils were the predominant leukocyte population in both fractions until PIH 59. From PIH 72, lymphocytes were the predominant cell population until PIH 175 in foremilk and until PIH 223 in residual milk. Serum albumin content and N-acetyl-beta-D-glucosaminidase activity in residual milk was significantly lower than in foremilk from PIH 4 to 24 and from PIH 24 to 59, respectively. Regarding total and differential leukocyte counts, values for the 2 fractions followed the same pattern throughout the course of inflammation, probably owing to frequent sample collection. Total and differential cell counts tended to differ between the fractions during some periods, although differences were not statistically significant. When samples were taken less frequently, the total leukocyte concentration in residual milk was higher than that in foremilk. Although sample collections were frequent, clustering of immature neutrophils was not observed in the cytofluorogram of blood leukocytes in this study. Residual milk seems to be the fraction that best reflects the condition in the quarter at the particular time when the milk sample is taken. Results also indicate that residual milk reflects the condition of the secretory tissue, as well as the lower regions of the gland.

Ten coxofemoral joints from 5 dog cadavers were used to study the effect of coxofemoral positioning on passive hip laxity. A material test system was used to measure lateral translation when force was between 20 N of compression and 40 N of distraction. Using the orthogonal coordinate system imposed in this study, neutral position was empirically defined at 15 degrees of extension and 10 degrees of abduction, relative to the plane of the pelvis, and no internal or external rotation of the femur. The hips were mounted in a custom-designed jig that allowed 1 rotational degree of freedom (ie, either flexion/extension, adduction/abduction, or internal/external rotation), while holding the other 2 constant. Lateral translation of the hips was tested at 10 degrees intervals from 30 degrees of flexion to 70 degrees extension, 40 degrees of adduction to 60 degrees of abduction, and 30 degrees of internal rotation to 40 degrees of external rotation. Lateral displacement was maximal at 10 degrees of extension, 20 degrees of abduction, and 10 degrees of external rotation, approximating the neutral coxofemoral position during stance. As the hips were rotated into extreme positions, the amount of lateral displacement occurring with the same applied load decreased significantly to 32.0 to 65.3% of the maximal displacement. Determining the position of the hip associated with maximal passive laxity in vitro is essential to the design of a precise and accurate clinical stress-radiographic method to quantitate joint laxity in dogs. Our results confirm earlier work that passive hip joint laxity is at a maximum with the hip approximately in a neutral weight-bearing position.

Cardiovascular and at accompany markedly long periods (12 hours) of halothane anesthesia were characterized. Eight spontaneously breathing horses were studied while they were positioned in left lateral recumbency and anesthetized only with halothane in oxygen maintained at a constant end-tidal concentration of 1.06% (equivalent to 1.2 times the minimal alveolar concentration for horses). Results of circulatory and respiratory measurements during the first 5 hours of constant conditions were similar to those previously reported from this laboratory (ie, a time-related significant increase in systemic arterial blood pressure, cardiac output, stroke volume, left ventricular work, PCV, plasma total solids concentration, and little change in respiratory system function). Beyond 5 hours of anesthesia, arterial blood pressure did not further increase, but remained above baseline. Cardiac output continued to increase, because heart rate significantly (P < 0.05) increased. Peak inspiratory gas flow increased significantly (P < 0.05) in later stages of anesthesia. There was a significant decrease in inspiratory time beginning at 4 hours. Although PaO2, and PaCO2, did not significantly change during the 12 hours of study, PVO2 increased significantly P < 0.05) and progressively with time, beginning 6 hours after the beginning of constant conditions. Metabolic acidosis increased with time significantly [P < 0.05] starting at 9 hours), despite supplemental IV administered NaHCO3. Plasma concentrations of eicosanoids: 6-ketoprostaglandin F1 alpha (PGF1 alpha, a stable metabolite of PGI2), PGF2 alpha, PGE, and thromboxane (TxB2, a stable metabolite of TxA2) were measured in 5 of the 8 horses before and during anesthesia. Significant changes from preanesthetic values were not Significant changes from preanesthetic values were not detected. Dynamic thoracic wall and lung compliances decreased with time.

Vaginal aerobic bacterial flora was studied in 5 healthy bitches before, during, and after a 10-day period of treatment with ampicillin and an equally long period of treatment with trimethoprim-sulfamethoxazole. Blood variables and antimicrobial drug susceptibility also were studied. Bacteria were isolated from all bitches before the first treatment period. Bitches from which only a sparse number of bacteria were isolated had flora that varied from day to day. In most instances when bitches were given an antibiotic to which their vaginal bacterial flora was susceptible, these bacteria were eradicated after only 1 day of treatment. This was true for pasteurellae, streptococci, and, in all but one case, Escherichia coli. Staphylococcus intermedius was more difficult to eradicate, and, although susceptible in vitro, it was unaffected by antibiotic treatment in 1 bitch and it took 7 days to eradicate in another. Eradication of aerobic bacteria in the vagina was total only in the bitch that had sparse flora from the beginning. Bacteria colonized within 0 (in 4/5 bitches) to 4 days after termination of treatment with ampicillin and within 0 (in 4/5 bitches) to 3 days for trimethoprim-sulfamethoxazole. Mycoplasmas emerged during and after both treatment periods, and E coli became apparent during treatment with trimethoprim-sulfamethoxazole. Because mycoplasmas may be genital pathogens in bitches and E coli is a common uropathogen, their appearance should be an argument against widespread use of antibiotics in healthy breeding bitches. Two bitches developed a vaginal discharge during treatment or shortly after. Blood variables did not change during the study, nor did antimicrobial drug resistance of the isolated bacteria.

The role of interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor a during endotoxin-induced mastitis in cows was characterized. Six cows had 10 microgram of Escherichia coli lipopolysaccharide infused into 1 mammary gland. Three other cows served as nontreated controls. Within 1.5 to 2.5 hours after infusion, endotoxin caused obvious edema of the mammary gland and increased serum albumin concentration in milk of infused glands 6 times. Milk somatic cell count began to increase 3 to 5 hours after infusion in all treated glands. At 7 hours after infusion, somatic cell counts were increased > 10 times, compared with counts in milk from control cows. Pyrexia of > 1 C developed in only 1 cow, but all treated cows had serum cortisol concentrations > 50 ng/ml in response to endotoxin treatment. High concentrations of IL-1 (10 to 600 U/ml) and IL-6 (2 to 22 U/ml) were detected in milk of infused glands beginning 2.5 to 4 hours after infusion. Endotoxin did not induce detectable amounts of tumor necrosis factor activity in milk or serum. Swelling and mammary gland permeability changes preceded any detectable increase in IL-1 and IL-6 activity, indicating that these clinical signs of inflammation were not mediated by these cytokines. Systemic responses and the leukocytic influx into endotoxin-infused glands developed after or concurrently with initial increases in IL-1 and IL-6 activities in milk. These results suggested that IL-1 and IL-6 may have a role in mammary gland defenses and in the pathophysiologic changes during endotoxin-induced mastitis.