Distal airway segments (ID, 3 to 4 mm; length, 5 mm) from 2 groups of horses were isolated and suspended in tissue baths filled with Krebs solution, aerated with 5% CO2 in oxygen and maintained at 37 C. Responses to exogenous acetylcholine, isoproterenol, or electrical field stimulation were compared. Control horses (n = 30) had no history of recurrent airway obstruction, whereas principal horses (n = 15) had recurrent airway obstruction and were studied during an acute episode of airway obstruction. Although the distal airways contracted in response to the cumulative half-logarithmic addition of acetylcholine (10(-10)M to 10(-3)M) in both groups, bronchi obtained from principals were less sensitive to acetylcholine than were bronchi obtained from controls. Tetrodotoxin-sensitive electrical field stimulation-induced contractions were observed in both groups of airways, but the tension achieved in principal bronchi was less than in controls. All electrical field stimulation-induced contractions were abolished by atropine, indicating that the only excitatory innervation of equine distal airways is through the parasympathetic system. To examine the effect of isoproterenol and determine inhibitory innervation, bronchi were precontracted with histamine. Electrical field stimulation did not cause relaxation of precontracted bronchi in either group, thus indicating that distal airways lack inhibitory innervation. Isoproterenol caused similar, dose-dependent relaxation in both groups.

Hematologic reference values were determined for a captive population of 11 Mexican wolves (Canis lupus baileyi). Wolf pups from 4 to 24 weeks old had progressive age-related increases in PCV, hemoglobin concentration, mean cell volume, and RBC counts similar to those seen in domestic dog pups (C familiaris). Hematologic indices in wolves older than 24 weeks were comparable to those of the adult domestic dog; however, PCV, hemoglobin concentration, and RBC counts were higher.

Three studies were conducted to determine the efficacy of milbemycin oxime in the prevention of Dirofilaria immitis infection in dogs. Dogs were given single or multiple experimental inoculations with infective third-stage D immitis larvae and were treated with milbemycin oxime at a target dosage of 0.5 mg/kg of body weight either once or at monthly intervals at various times after inoculation. The compound was effective in preventing infection when 1 dose was administered 30 or 45 days after inoculation. Significant, but incomplete, protection was achieved when single treatments were administered 60 or 90 days after inoculation. Multiple monthly treatments beginning 60 days after inoculation appeared to provide additive effects that resulted in restoration of complete efficacy.

The purpose of this in vitro study was to determine whether Pasteurella haemolytica capsular extract (CE) damages bovine pulmonary endothelial cells (EC) directly or through neutrophil-mediated mechanisms. Chromium 51-labeled EC were treated with the following variables: CE (1, 10, and 100 ng of protein/ml), CE and bovine neutrophils (10(6) cells/well), and CE and polymyxin B (500 U/ml). Although only minimal damage to EC occurred by 5 hours after treatment, by 22 hours after treatment, the 10-ng and 100-ng CE dose produced severe damage to EC, as indicated by 51Cr release, cellular detachment, and loss of monolayer confluency. The component in the CE that was toxic to the EC was lipopolysaccharide, evidenced by effective neutralization of the toxic effect with polymyxin B. Neutrophils inhibited the CE-mediated EC toxicity and were activated, as indicated by shape change and adhesion to EC monolayers. We concluded that the lipopolysaccharide component of CE causes direct damage to EC, which can be attenuated by neutrophils and polymyxin B.

Twelve ponies were used to evaluate the reliability of an abdominal adhesion model and the efficacy of intraperitoneal infusion of sodium carboxymethylcellulose in preventing abdominal adhesions. A celiotomy was performed on each of the 12 ponies and the serosa of the distal portion of the jejunum was abraded with a dry gauze sponge at 5 locations. In addition to the serosal damage, a single 2-0 chromic gut suture was placed through the seromuscular layer of the jejunum in the center of the abraded area. After closure of the celiotomy, a 1% solution of sodium carboxymethylcellulose (7 ml/kg of body weight) was infused into the peritoneal cavity of 6 ponies. The other ponies served as untreated controls. All ponies were euthanatized 14 days after surgery. All ponies in the control group had abdominal adhesions at the time of necropsy. Four of the 6 ponies in the treatment group were free of adhesions. There was a significant (P < 0.0001) difference in the total number of adhesions between the 2 groups.

A dose titration study was undertaken to determine the efficacy of clorsulon against the adult stage of Fasciola hepatica in goats. Thirty-nine goats were experimentally infected with metacercariae of F hepatica. At 14 weeks after infection, each goat was assigned randomly to 1 of 5 groups. Goats in groups 1 to 4 received a single oral administration of clorsulon at dosages of 3.5, 7, 11, and 15 mg/kg of body weight, respectively. The fifth group of goats (control group) was infected with F hepatica, but were not treated with clorsulon. Postmortem examination of goats at 3 weeks after treatment revealed mean reductions in numbers of flukes of 83, 98, 99, and 100% for groups 1 to 4, respectively. Mean percentage of reduction in eggs following treatment of groups was 82, 98, 100, and 100%, respectively. The clinical effects of clorsulon in 24 goats that were not infected with F hepatica were studied. Goats in groups 1 to 3 received a single oral administration of clorsulon at dosages of 7, 21, and 35 mg/kg, respectively, every other day for a total of 3 doses/goat. Group-4 goats (control group) received a vehicle placebo. Goats in group 3 were subject to postmortem examination at 14 days after dosing. Abnormal signs or lesions that could be attributed to clorsulon were not found in any goat.

An ELISA was developed and tested for its ability to detect antibodies against Salmonella enteritidis in chickens. Various features of the ELISA were evaluated and optimized. The outer membrane protein antigens selected by use of the protein immunoblotting method made the assay specific and sensitive. The assay was evaluated in chickens experimentally infected with S enteritidis. Blood samples collected at weekly intervals after experimental infection with S enteritidis were analyzed by ELISA. Results of the ELISA were compared with those of conventional serum plate and microagglutination tests. The ELISA was more sensitive and specific in the detection of S enteritidis infection than the other 2 conventional tests.

Sheep had viremias that were first detected on day 3 (+/- 1) after infection with several strains of bluetongue virus (BTV) representing United States serotypes 10, 11, 13, and 17. Diphasic peaks of infectivity were attained on days 6 and 10 (+/- 2). Interferon (IFN) was first detected in serum samples on day 5 (+/- 1), and reached greatest concentrations on day 6 (+/- 2), which coincided with the first viremic peak; IFN concentrations then decreased toward zero by day 10 (+/- 2). Interferon peak concentrations induced approximately a 90% decrease in virus titer. The decrease in IFN concentrations by day 9 (+/- 2) corresponded with the second viremic peak on day 10 (+/- 2). Onset of the decrease in detectable concentrations of virus after the second peak of viremia corresponded to the initial detection of serum antibody to BTV by day 10 (+/- 2). Virus titer decreased and antibody production increased until approximately days 21 to 28, when the titers plateaued and virus was not detected. Febrile responses peaked on day 7 (+/- 1) during the peak viremic period. The WBC count was depressed at the time the virus titer increased, but returned to normal values while the sheep were still viremic. Diphasic viremias in BTV-infected sheep were attributed to induction of high concentrations of IFN concurrent with the first virus titer peak, followed by production of antibody to specific BTV strains and a subsequent reduction in viremia at the second virus titer peak.

Eighteen dogs with naturally acquired helminth infections were used to evaluate the efficacy of nitroscanate against Ancylostoma caninum, Dipylidium caninum, and Trichuris vulpis. Approximately 15 minutes before treatment, the dogs were given 100 to 200 g of canned dog food. Ten dogs were treated with nitroscanate (50 mg/kg of body weight, PO), and 8 dogs were given placebo tablets PO. The dogs were euthanatized and necropsied 10 days after treatment and helminths were recovered from the small intestine and cecum. On the basis of the number of worms recovered from treated dogs vs the number recovered from control dogs, we determined the efficacy of nitroscanate to be 99.6% against A caninum, 99.8% against D caninum, and 0% against T vulpis.

Phosphonoformate (PFA), a noncompetitive inhibitor of reverse transcriptase (RT), inhibited feline leukemia virus FeLV) infection of 2 feline cell lines and inhibited progeny virus RT activity in a chronically FeLV-infected cell line. Feline leukemia virus infection of 3201 cells, an FeLV-negative lymphoma cell line, was inhibited by > 70% at a concentration of only 1 micromole PFA and by > 90% at concentrations of 64 to 256 micromole PFA, as evidenced by RT activity. However, FeLV antigen expression by 3201 cells remained relatively constant over noncytotoxic concentrations of PFA. Because the persistence of viral antigen expression with concomitant suppression of RT activity appears to be unique and because 3201 cells express small amounts of an endogenous retrovirus (RD and 114) contain endogenous FeLV proviral sequences, a possible role of endogenous retroviruses acting as helper viruses was suggested. Feline leukemia virus infection of 81C cells, a sarcoma-positive, leukemia-negative fibroblast cell line, was inhibited by > 50% at a concentration of 64 micromole PFA and by > 98% at concentrations of 256 to 512 micromole PFA, as indicated by suppression of focus formation. The feline lymphoid cell line FL-74 is a large producer of FeLV. When FL-74 cells were cultured in the presence of 256 micromole PFA, virus production (virus budding and viral antigen) was not affected, but progeny virus lost RT activity and infectivity. Direct addition of PFA (256 micromole to FeLV also reduced RT activity and infectivity. These data indicate that PFA can directly and rapidly inactivate retrovirus independent of cellular processing, presumably by inhibiting RT. Long-term PFA administration may curtail spread of retroviral infections within and between hosts via extracellular inactivation of newly produced virus particles. Results of this study also suggest that PFA might be used prophylactically to treat materials potentially contaminated with retroviruses.