Bronchoalveolar lavage (BAL) was performed on 16 horses to determine whether it caused local or diffuse inflammation in the lungs. In 7 horses, BAL was performed in both lungs twice, 48 hours apart. Although total cell counts of the BAL samples did not change significantly, there were increased numbers and percentage of neutrophils in the second lavage fluid samples. In 5 horses, BAL was performed in 1 lung and repeated 48 hours later in the same lung and in the corresponding airway in the contralateral lung. The absolute cell count and percentage of neutrophils were significantly (P = < 0.05) increased in the second sample from the lung that was lavaged twice. In 4 horses, BAL was performed in 1 lung and 48 hours later, repeated in an adjacent airway to the first BAL site, and in the corresponding airway in the contralateral lung. Significant differences were not detected in the total or differential cell counts of the BAL fluid recovered at any time, except for an increase in neutrophil percentage in the second sample in the contralateral lung. The increased neutrophil percentage values were within the range of normal for healthy horses. Results of the study suggested that, in horses, BAL induces a localized pulmonary neutrophil influx that persists at least 48 hours and is characterized by a relative and absolute increase in the number of neutrophils in the lavage fluids.

We used monoclonal antibodies and immunohistologic examination of lymph nodes, to elucidate the pathogenesis of lymphosarcoma induced by, infection with bovine leukemia virus (BLV). The superficial cervical lymph nodes from 3 BLV-infected but apparently healthy sheep and 5 sheep with full-blown lymphosarcoma were examined. We also investigated the integration of bovine leukemia provirus by use of Southern blotting. In lymph nodes from sheep lacking clinical signs of infection, in which the provirus had been integrated at multiple sites in the genome, many large hypertrophic follicles were observed in the cortex. These follicles had germinal centers consisting of CD4+T cells and B cells that expressed surface IgM (sIgM) and major histocompatibility complex (MHC) class-II antigens, but not B cell-specific B2 molecule. The percentage of CD4+T cells in the cortex was significantly (P < 0.05) higher than that of the controls and sheep with lymphosarcoma. In all sheep with lymphosarcoma, the lymph nodes were completely destroyed by proliferating neoplastic cells, and in addition, small atrophic follicles, which consisted of normal B-cell marker-positive cells, were seen near the trabecula and the subcapsule. In these instances, neoplastic cells appeared to be a monoclonal population derived from a single CD5- B-cell lineage and to be classified as 2 types, CD5-CD4-CD8-B2+MHC class-II+sIgM+ and CD5-CD4-CD8-B2+MHC class-II+sIgM-. Moreover, CD8+T cells infiltrated diffusely throughout the tumorous lymph nodes apart from the atrophic follicles, and CD4+T cells were observed around atrophic follicles. Both types of T cells were small-size, normal lymphocytes with round and noncleaved nuclei, and were apparently non-neoplastic cells. In fact, after separation by use of a panning method, it seems that, in blood mononuclear cells from BLV-infected sheep without clinical signs of infection, but in lymphosarcomatous stages, the proviral genome was integrated only in B cells and not in T cells. Thus, we conclude that the host's immune response may be still maintained at a lymphosarcomatous stage.

To differentiate Mycoplasma hyopneumoniae, the cause of mycoplasmal pneumonia in pigs, from M flocculare and M hyorbinis, an assay, using the polymerase chain reaction to amplify a segment of the 16S rRNA gene sequence, was developed. The assay was found to be useful for identification of field isolates, as well as for identification of laboratory-adapted strains. Amplification of DNA from M hyopneumoniae and M flocculare resulted in products of 200 and 400 base pairs, respectively. The DNA from M hyorbinis was not amplified. The assay was sensitive enough to detect as little as 1,000 genome equivalents of M hyopneumoniae and M flocculare DNA. Sensitivity was increased 100-fold by increasing the concentration of magnesium ion in the reaction buffer from 2 to 4 mM; however, DNA from M hyorbinis was also amplified under these conditions. The DNA from several walled bacteria and from other mycoplasmas was also tested, but none of these DNA samples was amplified, suggesting that the assay was specific for porcine mycoplasmas.

Pharmacologically induced splenic contraction might be useful during certain medical or surgical procedures in horses. The effects of phenylephrine, an alpha 1-adrenergic receptor agonist, on hemodynamic function and splenic dimensions were examined in 6 healthy adult horses. Phenylephrine infusion (1, 3, or 6 microgram/kg of body weight/min for 15 minutes) resulted in a dose-related increase in mean pulmonary artery pressure; right atrial pressure; systolic, mean, and diastolic arterial pressures; and packed cell volume (P = 0.0001). Concurrent decreases in heart rate and specific cardiac output (P = 0.0001) were detected, but stroke volume did not vary significantly. The rate-pressure product was increased only at the highest phenylephrine dosage (P = 0.012). Bradycardia was observed at all dosages during drug infusion, and second-degree atrioventricular block was detected in 88% of horses during infusion. Phenylephrine administration caused dose-dependent splenic contraction, as detected by ultrasonographic measurements of splenic area and thickness (P = 0.0001). At the 3- and 6-microgram/kg/min infusion rates, splenic area was reduced to 28 and 17% of baseline measurement, respectively. Splenic dimensions had returned to baseline values by 35 minutes after the end of infusion. Infusion of phenylephrine at a dosage of 3 microgram/kg/min for 15 minutes can be used to induce splenic contraction in horses.

Equine oxyntic mucosal cells were obtained by sequential exposure to pronase and collagenase. Acid production by parietal cells was assessed by uptake of [14C]aminopyrine (AP), a weak base that accumulates in intracellular acidic spaces. Incubation for various times revealed a maximal AP uptake at 10 minutes for histamine and carbachol. Similar secretagogue responses were observed for parietal cells from the mucosal cell preparation or after enrichment by elutriation. Histamine and isobutyl-methylxanthine (IBMX) stimulated AP uptake with a dose-dependent response and maximal effective concentration of 100 micromolar. Carbachol, 1 to 100 micromolar, and pentagastrin (PG), 1 to 1,000 nM, were ineffective stimulants of AP uptake. The AP uptake values for 100 micromolar IBMX, 1 micromolar carbachol, or 100 nM PG were 77 +/- 6%, 50 +/- 3.2%, and 40 +/- 4.5%, respectively, of that observed with maximal stimulation by 100 micromolar histamine (mean SEM, n = 4 to 14). Uptake of AP by nonstimulated control cells was 36 +/- 3.6% of maximal histamine stimulation. The AP accumulations during control conditions and after stimulation with 100 micromolar histamine and IBMX, 1 micromolar carbachol, or 100 nM PG were 1.18 +/- 0.39, 2.81 +/- 0.85, 1.93 +/- 0.48, 1.44 +/- 0.36, and 1.23 +/- 0.33 pmol of AP/10(5) parietal cells, respectively. Individual histamine dose-response curves were shifted to the right by increasing ranitidine and cimetidine concentrations (0.1 to 50 micromolar). These results indicate that isolated equine parietal cells are maximally stimulated by histamine and minimally stimulated by carbachol and PG.

Environmental variables in 10 commercial turkey confinement buildings, representing 2 natural ventilation designs, were measured during summer and the following winter. Sliding doors spaced at intervals along the walls of 5 of the buildings provided about 35% opening, and continuous wall curtains provided 60 to 80% opening in the other 5 buildings. Environmental variables assessed included airspeed; temperature; relative humidity; gases; particle number, size, and mass per cubic meter of air; and colonies of bacteria, yeasts, and other fungi per cubic meter of air. Colonies of yeasts and other fungi were quantitated in feed and litter. For most of the variables evaluated, significant differences were not attributable to building ventilation design; however, in winter, the total mass of particulate matter per cubic meter of air was higher in the curtain-type houses, compared with sliding door-type houses. Ammonia concentration in the air of sliding door-type houses progressively increased during summer and winter sampling periods. A significant effect of building ventilation design on turkey performance was not detected when using mortality, average daily gain, feed conversion, condemnations at slaughter, or average individual bird weight as measures of production.

Efficacy of fenbendazole at 2 dosages for treating naturally acquired giardiasis in dogs was assessed. Giardia cysts were not detected in the feces of 6 of 6 group-1 dogs (as determined by use of the zinc sulfate concentration technique) after fenbendazole treatment (50 mg/kg of body weight, PO, q 24 h, for 3 doses). Cysts were not detected in the feces of 6 of 6 group-2 dogs after fenbendazole treatment (50 mg/ kg of body weight, PO, q 8 h, for 3 days). However, cysts were not detected in the feces of only 1 of 6 group-3 (nontreated control) dogs. Signs of toxicosis were not observed in any dog. These results indicate that the current label dosage (for the treatment of Toxocara canis, Toxascaris leonina, Ancylostoma caninum, Uncinaria stenocephala, Trichuris vulpis, and Taenia pisiformis, but not Giardia spp) of fenbendazole (50 mg/kg, PO, q 24 h, for 3 doses) is also effective for treating giardiasis in dogs.

We determined whether administration of cryoprecipitate or fresh-frozen plasma (FFP) would enhance glass bead platelet retention and shorten the bleeding time in von Willebrand factor (vWf)-deficient Doberman Pinschers. Plasma concentration of vWf was < 15% of the reference value in these dogs and, on the basis of multimeric analysis of vWf, these dogs had type-I von Willebrand's disease (vWd). Concentration of vwf in cryoprecipitate (prepared from FFP of clinically normal dogs) was enriched almost 20 times, and the preparation was a concentrate of the largest and most physiologically active multimers. Administration of a dose of cryoprecipitate calculated to increase plasma vWf concentration of recipient dogs to 50 U/dl increased plasma vWf concentration in recipient dogs to about 40 U/dl. Mean buccal mucosal bleeding time (BMBT) shortened from 6.7 minutes before treatment to 3.8 minutes at 2 hours after treatment. Cryoprecipitate from donor dogs treated with deamino-8-D-arginine vasopressin (1 microgram/kg of body weight) effectively shortened mean BMBT from 6.4 minutes to 3.1 minutes. Administration of cryoprecipitate from vWf-deficient dogs prolonged, rather than shortened, the BMBT. After FFP (450 ml) infusion, plasma vwf concentration increased in recipient dogs, but the BMBT did not shorten. Glass bead platelet retention did not change after administration of cryoprecipitate or FFP. Thus, cryoprecipitate, especially from deamino-8-d-arginine vasopressin-treated donor dogs, is a concentrate of the most hemostatically active multimers of vWf and decreases the BMBT in dogs with vWd.

A regional prospective study of the epidemiology of bluetongue virus (BTV) serotypes covering 11 countries in Central America and the Caribbean took place between 1987 and 1992. Active surveillance revealed BTV infection to be endemic in the absence of confirmed indigenous cases of bluetongue. During the 6-year span of the study, over 300 BTV isolations were obtained from cattle and sheep. Results of the earlier years of the study were summarized, and surveillance activities in the concluding months of the study from November 1990 to February 1992 were evaluated. Forty-five BTV isolations were made during this time, 44 from sentinel cattle and 1 from a ram with clinical signs compatible with contagious ecthyma. Virus isolation from potential vectors also was attempted, yielding a further 9 BTV isolates from parous Culicoides insignis and C pusillus, 2 BTV isolates from blood-engorged C filarifer, and 1 epizootic hemorrhagic disease virus type-2 isolate from parous C pusillus. Our extensive network of sentinel herds in the region detected BTV-1 as the predominant serotype in Central America in 1991, after an apparent absence of 1 year in the sentinel animals. Other serotypes in Central America at that time included BTV-3 and BTV-6. In Puerto Rico and the Dominican Republic, BTV-4 became the predominant serotype, without detection of BTV-8 and BTV-17, which were common in recent years of the study. The serotypes found in the Caribbean Basin continued to have marked differences from those in North America. The importance of viewing bluetongue as an infection, the distribution of which is determined principally by ecologic factors, is emphasized.

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.