Eighteen dogs undergoing lateral thoracotomy at the left fifth intercostal space were randomly assigned to 1 of 3 postoperative analgesic treatment groups of 6 dogs each as follows: group A, morphine, 1.0 mg/kg of body weight, IM; group B, 0.5% bupivacaine, 1.5 mg/kg given interpleurally; and group C, morphine, 1.0 mg/kg given interpleurally. Heart rate, respiratory rate, arterial blood pressure, arterial blood gas tensions, alveolar-arterial oxygen differences, rectal temperature, pain score, and pulmonary mechanics were recorded hourly for the first 8 hours after surgery, and at postoperative hours 12, 24, and 48. These values were compared with preoperative (control) values for each dog. Serum morphine and cortisol concentrations were measured at 10, 20, and 30 minutes, hours 1 to 8, and 12 hours after treatment administration . All dogs had significant decreases in pHa, PaO2, and oxygen saturation of hemoglobin, and significant increases in PaCO2 and alveolar-arterial oxygen differences in the postoperative period, but these changes were less severe in group-B dogs. Decreases of 50% in lung compliance, and increases of 100 to 200% in work of breathing and of 185 to 383% in pulmonary resistance were observed in all dogs after surgery. Increases in work of breathing were lower, and returned to preoperative values earlier in group-B dogs. The inspiratory time-to-total respiratory time ratio was significantly higher in group-B dogs during postoperative hours 5 to 8, suggesting improved analgesia. Blood pressure was significantly lower in group-A dogs for the first postoperative hour. Significant decreases in rectal temperature were observed in all dogs after surgery, and hypothermia was prolonged in dogs of groups A and C. Significant differences in pain score were not observed between treatment groups. Cortisol concentration was high in all dogs after anesthesia and surgery, and was significantly increased in group-B dogs at hours 4 and 8. Significant differences in serum morphine concentration between groups A and C were only observed 10 minutes after treatment administration. In general, significant differences in physiologic variables between groups A and C were not observed. Results of the study indicate that anesthesia and thoracotomy are associated with significant alterations in pulmonary function and lung mechanics. Interpleurally administered bupivacaine appears to be associated with fewer blood gas alterations and earlier return to normal of certain pulmonary function values. Interpleural administration of morphine does not appear to provide any advantages, in terms of analgesia or pulmonary function, compared with its IM administration.

Pseudorabies virus (PRV) nucleic acids in the trigeminal ganglia and tonsils of swine latently infected with the virus were analyzed. By use of DNA-polymerase chain reaction (PCR), 14 of 14 trigeminal ganglia and 12 of 14 tonsils were positive for PRV genomes. By use of RNA-PCR, RNA containing the large latency transcript splice junction were detected in 4 of 4 trigeminal ganglia and 4 of 5 tonsils. In general, results of both PCR procedures indicated that the amounts of PRV DNA and RNA per microgram of cellular nucleic acids were higher in trigeminal ganglia than in tonsils. Identification of peripheral tissues that harbor latent PRV is an important asset for PRV research. The presence of large latency transcript in tonsil tissues, in the absence of virus replication, is a critical characteristic, which indicates that the tonsil is a site of PRV latency. For diagnostic purposes, animals need not be euthanatized to obtain their nervous tissue to determine latency; instead, tonsil biopsy specimens could be obtained from live animals for analysis. For pathogenesis studies, multiple specimens obtained sequentially from the same animal would be available for examination for the duration of the experiment.

Two techniques for evaluating argyrophilic nucleolar organizer regions (AgNOR) were compared on 74 canine mammary tumors to discriminate between benign and malignant lesions. For each lesion, direct counting of AgNOR on at least 100 cell nuclei was compared with area, perimeter, and integrated optical density AgNOR dot values determined by image analysis. Significant differences between benign and malignant tumors were observed with both methods; however, lesions determined as aggressive or proliferative by histologic evaluation were only singled out by image analysis measurements. Image analysis, in our hands, was a reliable, precise, and convenient technique to characterize malignancy in canine mammary tumors.

The effects of hypertonic saline solution (HSS) and hyperosmotic dextrose (HD; 2,400 mosm/L, 4 ml/kg of body weight) on left ventricular afterload were determined in normovolumic, chloralose-anesthetized, autonomically blocked dogs (n = 8). Solutions were infused IV over 3 minutes. Left ventricular afterload was assessed by use of a dual-tipped micromanometer catheter with an electromagnetic fluid-velocity sensor located in the ascending aorta, and the impedance spectrum was calculated after Fourier analysis of signal-averaged aortic pressure and flow signals. Hypertonic saline solution and HD decreased peripheral resistance, reflection coefficient at zero frequency, and frequency of the first zero crossing of the phase angle for 3 to 5 minutes after either fluid was administered. Characteristic impedance was not altered by HSS or HD. These impedance spectrum changes indicate transient vasodilatation and afterload reduction. We conclude that the vascular effect of an ionic hyperosmotic solution (HSS) is similar to that of a nonionic hyperosmotic solution (HD), and that HSS and HD transiently decrease afterload in normovolumic dogs. The duration of the afterload reduction after HSS administration appeared to be too short to be of great clinical benefit.

During acute bouts of recurrent airway obstruction (heaves) in horses, neutrophils that are capable of increased production of reactive oxygen species accumulate in the airways. In the study reported here, the effect of hydrogen peroxide (H2O2; 1 micromolar to 0.1M), one of these reactive oxygen species products, on the responses of isolated trachealis muscle of horses was determined. Before and after incubation with H2O2, contractile responses to acetylcholine, electrical field stimulation (EFS), 127 mM KCl, and relaxation responses to isoproterenol and activation of the nonadrenergic noncholinergic inhibitory response (iNANC) were evaluated. Beginning at 1 mM, H2O2 contracted trachealis muscle in a concentration-dependent manner. This contraction was unaffected by atropine (1 micromolar), tetrodotoxin (1 micromolar), or 1 micromolar meclofenamate. Contraction of trachealis muscle in response to H2O2 is, therefore, not attributable to release of prostaglandins, acetylcholine, or other neurotransmitters. Above a concentration of 0.1 mM, H2O2 depressed the responses to EFS. acetylcholine, and KCl in a concentration-dependent manner. At 0.1M, H2O2 decreased the maximal responses to EFS, acetylcholine, and KCl by 62.7 +/- 7.2, 60.58 +/- 6.12, and 37.8 +/- 9.54%, respectively. In the presence of meclofenamate (1 micromolar), partial but significant protection against 1 to 100 mM H2O2 was observed. In tracheal strips contracted with 0.3 micromolar methacholine, H2O2 had no effect on the isoproterenol concentration-response curve. Up to a concentration of 100 mM, H2O2 had no effect on iNANC response. However, in the presence of 100 mM H2O2, this response was abolished in 2 of 4 horses. We conclude that high concentrations of H2O2 affected the responses of airway smooth muscle by actions on neurotransmission, muscarinic receptors, and downstream from receptors; some of the H2O2 effects were in part mediated by cyclooxygenase products; and H2O2 had no effect on beta-adrenergic- or iNANC-induced relaxation.

Bacampicillin hydrochloride is an ester prodrug that is hydrolyzed to ampicillin after its absorption from the gastrointestinal tract. It was administered intragastrically at a dose rate of 13.5 mg/kg of body weight to ponies and horses, and was highly bioavailable (F = 41.0%), compared with other penicillins in adult horses. The high peak ampicillin plasma concentration of 6.1 +/- 0.5 micrograms/ml achieved and persistence of the antibiotic at concentration of 0.3 +/- 0.1 micrograms/ml 6 hours after its intragastric administration, suggest that bacampicillin hydrochloride may reach suitable bactericidal concentrations for treatment of infections caused by susceptible microorganisms. In a separate experiment, dichlorvos, an organophosphate compound that inhibits some of the esterase activity in plasma, was administered orally to the same animals at a dose rate of 40 mg/kg followed by intragastric administration of bacampicillin hydrochloride at a dose of 13.5 mg/kg. Plasma pseudocholinesterase and erythrocyte acetylcholinesterase activities were reduced to < 5% of reference (predichlorvos) values after dichlorvos administration. However, rate of hydrolysis of bacampicillin into ampicillin was not affected. Consequently, the disposition and fate of bacampicillin when administered intragastrically 1 day after dichlorvos administration were similar to the values obtained after administration of bacampicillin alone. Intragastric coadministration of probenecid at a dose rate of 75 mg/kg and bacampicillin at 13.5 mg/kg limited absorption of the antibiotic from the gastrointestinal tract. This suggests existence of a common transport mechanism for bacampicillin and probenecid in the gastrointestinal wall, and precludes use of this combination for treatment. The bioavailable fraction of ampicillin after combination treatment indicated prolonged residence time in the plasma, presumably as a consequence of reduced renal tubular secretion.