In an effort to better understand the role of vasodilators in the management of pulmonary hypertension associated with chronic heartworm disease (HWD), pulmonary hemodynamic measurements were obtained from 7 experimentally infected, anesthetized dogs before and after hydralazine administration (mean dose, 1.96 mg/kg of body weight). Five dogs were maintained on room air, while 2 were maintained on 100% oxygen during the hydralazine study. The hemodynamic effect of hydralazine in dogs with HWD was evaluated, using heart rate, cardiac index, mean pulmonary artery pressure, mean arterial pressure, total pulmonary resistance, total systemic resistance, total systemic resistance/total pulmonary resistance, left ventricular dP/dt(max), left ventricular end diastolic pressure, and left and right ventricular double products ([mean arterial pressure X heart rate] and [mean pulmonary artery pressure X heart rate], respectively). Responders were defined as those in which total pulmonary resistance decreased greater than or equal to 20% without an increase in mean pulmonary arterial pressure and in which heart rate increase was less than or equal to 10%. Comparison was also made between maximal hemodynamic effect of hydralazine with that after 100% oxygen administration for 15 minutes to previously normoxemic dogs (n = 5). Significance was determined if P < 0.05, using the paired t-test. Hydralazine induced significant reductions in mean pulmonary and systemic arterial pressures and total pulmonary resistance, with no significant change in heart rate, cardiac index, total systemic resistance, left ventricular dP/dt(max), left ventricular end diastolic pressure, or right and left ventricular double products. Four (57%) of the 7 dogs studied were considered responders. Pretreatment cardiac index, mean pulmonary artery pressure, and total pulmonary resistance did not allow differentiation of responders from nonresponders. However, pretreatment right ventricular end diastolic pressure was significantly less in responders than in nonresponders. Two dogs sustained hypotension after hydralazine administration, but no dogs had significant tachycardia. In dogs with experimentally induced HWD, treatment with hydralazine had significantly greater effect on cardiac index and mean pulmonary and systemic arterial pressures and resistance than did administration of 100% oxygen. These data indicate that further study of vasodilators for treatment of HWD-induced pulmonary hypertension may be warranted.

We evaluated the effectiveness of 2 dopamine antagonists as treatments for fescue toxicosis in horses. Sixteen gravid mares were assigned by breed and expected foaling date to 1 of 3 treatment groups: endophyte-infested control 1.1 mg of domperidone/kg of body weight/d; and 3.3 mg of sulpiride/kg/d. Mares were pastured on endophyte-infected fescue and received 0.454 kg of a corn and dried molasses carrier containing the drug treatment. Treatment started 30 days prior to expected foaling date and continued until parturition. Blood samples were collected, and mammary gland scores were recorded every 5 days. Body weight and body condition scores were obtained every 28 days. Serum was analyzed for prolactin, progesterone, and estradiol-17beta concentrations. Domperidone-treated mares had shorter (P = 0.09) gestation duration and foaled closer (P = 0.07) to their expected parturition date than did control mares. Mammary gland scores were higher (P < 0.05) for domperidone-treated mares than for control mares. By 4 and 9 days after the start of treatment, serum prolactin concentration was higher P < 0.05) in domperidone-treated mares and sulpiride-treated mares, respectively, than in control mares. Domperidone- and and sulpiride-treated mares had higher (P < 0.05) serum progesterone and lower (P < 0.01) estradiol-17beta concentrations than did control mares. These results indicate that domperidone may offer considerable potential as a treatment for fescue toxicosis in horses.

Binding of endogenous and exogenous homologous IgG, and IgM to bovine neutrophils before and after in vitro migration through micropore filters, and in vivo migration through mammary tissues after intramammary injection of endotoxin was evaluated by use of flow cytometry. Immunoglobulin binding to neutrophils at 4 and 37 C was also evaluated. Before and after in vitro migration, neutrophils with endogenously bound IgG, and IgM averaged 1 and 2% and 23 and 7%, respectively. Before and after in vivo migration, IgG2 and IgM binding averaged 1 and 7% and 26 and 15%, respectively. Before and after in vitro migration, binding of purified IgG2 and IgM averaged 75 and 67% and 8 and 24%, respectively. Before and after in vivo migration, percentage of neutrophils binding purified IgG2 and IgM averaged 92 and 98% and 54 and 70%, respectively. When serum was used as a source of exogenous immunoglobulins, binding of total Igg after in vitro migration increased from 5% to 28% and of IgM from 4% to 20%. After in vivo migration, binding increased from 21% to 47% and from 24% to 56%, respectively. Exogenous binding of IgG2 at 4 and 37 C averaged 75 and 84%, and binding of IgM averaged 8% at either temperature. Endogenous IgG2 was unaffected by temperature; however, binding of IgM decreased from 23% at 4 C to 2% at 37 C. These data indicate that endogenous binding was higher for IgM before migration than after migration, in vitro and in vivo. Furthermore, migration in vivo through cellular matrices induced receptor upregulation for IgG and IgM. Source and concentration of ligand and serum components, other than immunoglobulins, appeared to contribute to receptor expression and availability. Neutrophils that were exposed to endotoxin and migrated into milk expressed more receptors than did unstimulated and nonmigrating neutrophils. The association of IgM with its receptor was temperature-dependent.

Development of an arthroscopic approach to the caudal pouches of the equine stifle has been necessary because cranial approaches do not allow access to articular lesions in the caudal aspect of the joint. Therefore, the anatomy of the caudal region was examined in 52 cadaver limbs by use of gross dissection, x-ray-computed tomography, fluoroscopy, or arthroscopy. Additionally, using arthroscopic techniques developed in equine cadaver limbs, 3 stifles from 2 anesthetized horses were arthroscopically explored. Fluoroscopy was used to verify needle placement for joint injection and filling patterns of each femorotibial joint. The medial femorotibial joint sac (n = 4) held a mean +/- SD 41.67 +/- 5.77 ml of injection fluid, and the lateral femorotibial joint sac (n = 4) held a mean 61.67 +/- 2.89 ml of injection fluid. Vital structures that inadvertently could be damaged during arthroscopy of the caudal pouches of the stifle included the peroneal nerve (located approx 7 cm caudal to the lateral collateral ligament), the popliteal artery and vein (situated directly between the medial and lateral femoral condyles), and the lateral femoral condyle (most often traumatized during arthroscopy). The tendon of the popliteus muscle, which is contiguous with the joint capsule of the caudal pouch of the lateral femorotibial joint, made arthroscopic exploration of this pouch particularly difficult.

Sixteen IgA-deficient German Shepherd Dogs with small intestinal bacterial overgrowth were randomized into 2 groups. One group was fed a chicken-based kibble diet; the other was fed the same diet, but with 1% fructo-oligosaccharides supplemented at the expense of cornstarch. After being exposed to the diets for 46 to 51 days, the group that ate the supplemented diet had significantly (P = 0.04) fewer aerobic/facultative anaerobic bacterial colony-forming units in fluid from the duodenum/proximal part of the jejunum, as well as in the duodenal mucosa. We could not detect significant differences in the species of bacteria found in the intestine of these 2 groups of dogs. We conclude that at least some dietary carbohydrates can affect small intestinal bacterial populations in dogs with small intestinal bacterial overgrowth.

We characterized the clinicopathologic manifestations of experimentally induced endotoxin-induced mastitis. Responses to hypertonic fluid therapy also were assessed. Eight cows received 1 mg of endotoxin by in infusion in the left forequarter. Four hours after endotoxin administration, cows received 0.9% NaCl, 5 ml/kg of body weight (n = 4) or 7.5% NaCl, 5 ml/kg (n = 4) IV. Endotoxin-infused cows had expanded plasma volume, hyponatremia, transient hyperchloremia and hypophosphatemia, increased serum glucose concentration, and decreased serum activities of liver- and muscle-specific enzymes. Calculated plasma volume increased at 6 hours in cows receiving hypertonic NaCl, and at 12, 24, and 48 hours after endotoxin infusion in both groups. Concurrent observations of decreased serum protein concentration, erythrocyte count, and hematocrit supported observations of increased plasma volume. Relative plasma volume was greater in cows receiving hypertonic NaCl (124.3%) than in cows receiving isotonic NaCl (106.6%) at 6 hours after endotoxin infusion. Cattle receiving hypertonic NaCl had increased voluntary water intake after IV fluid administration. Increased water consumption was not accompanied by increased body weight, indicating probable occurrence of offsetting body water loss. Serum sodium concentration in cows receiving hypertonic NaCl was increased 2 hours after fluid administration, but the magnitude of the change was minimal (< 4 mmol/L) and transient, indicating rapid equilibration with either interstitial or intracellular spaces. Serum sodium concentration was decreased in cows receiving isotonic NaCl at 12, 24, and 48 hours after endotoxin administration, compared with concentration prior to endotoxin administration, indicating selective loss of sodium.

A technique for measuring upper airway resistance was developed in awake untrained dolichocephalic and mesaticephalic dogs. Twenty healthy dogs, 10 Collies (group dolichocehalic) and 10 mixed-breed dogs (group B-mesaticephalic), were studied. All dogs tolerated the procedure well and adverse effects were not observed. Mean (+/- SEM) value for upper airway resistance was 7.1 +/- 0.50 cm of H2O/L/s. There was a trend toward lower upper airway resistance (Ruaw) values in group-A dogs, compared with those in group-B dogs. Values of Ruaw were reproducible for an individual dog. The mean individual dog coefficient of variation for Ruaw was 7.5%. The overall Ruaw coefficient of variation for all 20 dogs was 31.4%. This technique for measuring upper airway resistance in dogs is clinically applicable for objectively assessing response to treatment of obstructive upper airway disorders.

Inoculation of 53 ewes after 35, 45, 60, or 80 days of gestation with bluetongue virus serotypes 10, 11, 13, or 17, or with epizootic hemorrhagic disease virus serotypes 1 or 2, resulted in overt clinical disease in the 47 ewes inoculated with bluetongue virus but not in the 6 ewes inoculated with epizootic hemorrhagic disease virus. None of the lambs produced by these ewes had developmental defects or any evidence of persistence of viremia.

The ability of IV administered hydroxyethyl-starch-deferoxamine to attenuate radical production in freshly procured cancellous bone specimens was investigated, using spin-trapping and electron spin resonance (ESR) techniques. A core cancellous bone specimen 10 mm long and 5.6 mm in diameter was obtained, using aseptic technique, from the proximal portion of the humerus of 30 adult mixed-breed dogs. After procurement of the initial bone specimen, 10 dogs received a 10% solution of hydroxyethyl-starch-deferoxamine in 0.9% NaCl (50 mg/kg of body weight, IV), 10 dogs received an equivalent volume (5 ml/kg, IV) of a 10% solution of hydroxyethyl-starch in 0.9% NaCl, and 10 dogs received 0.9% saline solution (5 ml/kg, IV). A second core cancellous bone specimen was obtained from the contralateral humerus of each dog 45 minutes after treatment. All specimens were individually incubated in the spin trap alpha-phenyl-N-tert-butylnitrone in Eagle's minimum essential medium, at 26 C for 45 minutes, then were frozen at -20 C until they were prepared for analysis by ESR spectroscopy. Each specimen was thawed, homogenized, and extracted in a low-dielectric organic solvent prior to obtaining an ESR spectrum, which was analyzed for hyperfine splitting constants for radical identification. Each first-derivative spectrum was digitally double-integrated to obtain an area; these areas were used to compare intensities of the spin adducts. Difference in the area obtained before and after treatment for each dog was expressed as a ratio of that dogs pretreatment area ([pretreatment - posttreatment]/pretreatment). The calculated ratios for saline-, hydroxyethyl-starch-, and hydroxyethyl-starch-deferoxamine-treated dogs were compared, using a Kruskal-Wallis (KW) nonparametric test for multiple comparisons of ranked data. Significance was determined at P less than or equal to 0.05. Ad hoc comparisons were performed, using the KW procedure for individual comparisons, with alpha set at 0.05. The mean +/- SD and median ratio for each of the treatment groups were: saline-treated dogs, 0.005 +/- 0.40 and 0.045; hydroxyethyl-starch-treated dogs, -0.063 +/- 0.27 and -0.025; hydroxyethyl-starch-deferoxamine-treated dogs, 0.261 +/- 0.278 and 0.335, respectively. There was a significant (P < 0.01, KW) difference in the ratios between treatment groups. Ratios for hydroxyethyl-starch-deferoxamine-treated dogs were significantly (P < 0.05, KW) higher than that for hydroxyethyl-starch-treated dogs but not for saline-treated dogs. The ratios for saline- and hydroxyethyl-starch-treated dogs were not significantly different. We could not associate significant attenuation of radical generation in freshly harvested core cancellous bone specimens with IV administration of hydroxyethyl-starch-deferoxamine. The potential for unconjugated hydroxyethyl-starch to function as an oxidant must considered.

A recombinant pseudorabies virus that is defective in the early protein 0 (EP0) and large latency transcript (LLT) genes was constructed. A portion of the EP0 and LLT genes was replaced by the lacZ gene of Escherichia coli that had been placed under the control of the pseudorabies virus gX gene promoter. This recombinant virus produces smaller size plaques and yields less virus than does the parent virus on Madin-Darby bovine kidney cells. Although the time course of virus replication and release into the medium of the recombinant and parent viruses are similar, the recombinant virus did not reach as high a titer. Similar to the parent virus, the recombinant virus replicates in the upper segment of the respiratory tract of swine, but the amount of progeny viruses produced is significantly reduced. The data indicated that the EP0 and LLT genes of pseudorabies virus are nonessential for replication. Virus that lacks these 2 genes has impaired growth in tissue culture and is attenuated for swine, compared with the parent virus.