Three-week-old weaned and colostrum-deprived neonatal (< 1 day old) pigs were inoculated to determine the pathogenicity of 2 enterotoxigenic Escherichia coli isolates that do not express K88, K99, F41, or 987P adhesins (strains 2134 and 2171). Strains 2134 and 2171 were isolated from pigs that had diarrhea after weaning attributable to enterotoxigenic E coli infection. We found that both strains of E coli adhered in the ileum and caused diarrhea in pigs of both age groups. In control experiments, adherent bacteria were not seen in the ileum of pigs < 1 day old or 3 weeks old that were noninoculated or inoculated with a nonpathogenic strain of E coli. These control pigs did not develop diarrhea. Antisera raised against strains 2134 and 2171 and absorbed with the autologous strain, grown at 18 C, were used for bacterial-agglutination and colony-immunoblot assays. Both absorbed antisera reacted with strains 2134 and 2171, but not with strains that express K99, F41, or 987P adhesins. A cross-reaction was observed with 2 wild-type K88 strains, but not with a K12 strain that expresses K88 pili. Indirect immunofluorescence with these absorbed antisera revealed adherent bacteria in frozen sections of ileum from pigs infected with either strain. We concluded that these strains are pathogenic and express a common surface antigen that may be a novel adhesin in E coli strains that cause diarrhea in weaned pigs.

The hexon subunit of bovine adenovirus serotype 3 (BAV-3) was purified by use of anion-exchange chromatography. A vaccine composed of the purified hexon in immune-stimulating complexes was administered and induced high titer of virus-neutralizing antibody in rabbits and calves.

The aerobic bacterial flora of the genital tract was characterized in 15 stud dogs in an 18-month study. The dogs represented 4 breeds and were from 3 kennels. Bacterial samples from the prepuce and semen were collected every month, except in connection with matings, when they were collected weekly (464 samples). The dogs that were included all mated at least once during the study. The mean pregnancy rate, litter size, and pup mortality for the bitches with which they had mated were all within normal limits. The most frequent bacteria isolated from the prepuce and semen were Pasteurella multocida, beta-hemolytic streptococci, and Escherichia coli. There was a tendency for breeds to differ in frequency of the most common bacterial species. Bacterial culture yielded no aerobic growth in 14.2% of the preputial samples and 69.8% of the semen samples. Bacteria were transferred between dog and bitch at mating. In this study of healthy breeding dogs, neither the fertility of the dog nor that of the bitch was affected by the bacteria transferred.

Concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured in serum samples obtained from 100 dogs. Groups (n = 25/group) consisted of sexually intact and ovariohysterectomized bitches and sexually intact and castrated male dogs. Mean (+/- SD) concentrations of LH in the serum of sexually intact and ovariohysterectomized bitches were 1.2 (+/- 0.9) and 28.7 (+/- 25.8) ng/ml, respectively. Mean concentrations of FSH in the serum of sexually intact and ovariohysterectomized bitches were 98 (+/- 49) and 1,219 (+/- 763) ng/ml, respectively. Mean concentrations of LH in the serum of sexually intact and castrated male dogs were 6.0 (+/- 5.2) and 17.1 (+/- 9.9) ng/ml, respectively. Mean concentrations of FSH in the serum of sexually intact and castrated male dogs were 89 (+/- 28) and 858 (+/- 674) ng/ml, respectively. In addition to history, physical examination results, and other laboratory values, the measurement of serum gonadotropin concentrations may aid in determining whether dogs have been neutered.

A subcutaneous soft tissue infection model in calves was used to study the in vivo response of Pasteurella haemolytica to erythromycin and dexamethasone. Two tissue chambers were implanted SC in each of 12 calves. At 45 days after implantation, all tissue chambers were inoculated with an erythromycin-sensitive strain of P haemolytica. Starting 24 hours after inoculation, calves were allotted to 4 groups of equal size and a 2 X 2-factorial arrangement of treatments was applied: 3 calves were given erythromycin (30 mg/kg of body weight, IM, for 5 days), 3 calves were given dexamethasone (0.05 mg/kg, IM, for 2 days), 3 calves were given erythromycin and dexamethasone, and the remaining calves served as nontreated controls. Chamber fluids were tested daily, and the response to treatment was measured. Neither erythromycin nor dexamethasone affected viability or growth of bacteria within tissue chambers. Dexamethasone had no effect on the influx of neutrophils into infected chambers. Despite repeated administration of a high dose of erythromycin and attainment of adequate concentration in serum, erythromycin concentration in chamber fluids did not exceed the minimal inhibitory concentration established in vitro. These results indicate that the clinical efficacy of erythromycin against P haemolytica sequestered in consolidated pneumonic lesions may not be well correlated with predictions based on serum pharmacokinetic and in vitro susceptibility data.

Distribution of blood flow among various respiratory muscles was examined in 8 healthy ponies during submaximal exercise lasting 30 minutes, using radionuclide labeled 15-micrometers diameter microspheres injected into the left ventricle. From the resting values (40 +/- 2 beats/min; 37.3 +/- 0.2 C), heart rate and pulmonary arterial blood temperature increased significantly at 5 (152 +/- 8 beats/min; 38.6 +/- 0.2 C), 15 (169 +/- 6 beats/min; 39.8 +/- 0.2 C), and 26 (186 +/- 8 beats/min; 40.8 +/- 0.2 C) minutes of exertion, and the ponies sweated profusely. Mean aortic pressure also increased progressively as exercise duration increased. Blood flow increased significantly with exercise in all respiratory muscles. Among inspiratory muscles, perfusion was greatest in the diaphragm and ventral serratus, compared with external intercostal, dorsal serratus, and scalenus muscles. Among expiratory muscles, blood flow in the internal abdominal oblique muscle was greatest, followed by that in internal intercostal and transverse throacic muscles, in which the flow values remained similar. The remaining 3 abdominal muscles had similar blood flow, but these values were less than that in the internal intercostal, transverse thoracic, and internal abdominal oblique muscles. Blood How values for all inspiratory and expiratory muscles remained similar for the 5 and 15 minutes of exertion. However, at 26 minutes, blood flow had increased further in the diaphragm, external intercostal, internal intercostal, transverse thoracic, and the external abdominal oblique muscle as vascular resistance decreased. On the basis of our findings, all respiratory muscles were activated during submaximal exercise and their perfusion had marked heterogeneity. Also, blood flow in respiratory muscles was well maintained as exercise duration progressed; in fact, several muscles had a further increase in perfusion late during exercise.

Glomerular filtration rate (GFR) was measured in 12 clinically normal horses, using the standard inulin clearance method, and values were compared with values for 2 methods, using a single rapid IV injection of (99m)Tc-labeled diethylenetriaminepentaacetic acid ((99m)Tc-DTPA). The first (99m)Tc-DTPA method used a 2-compartment model to calculate GFR blood clearance of the tracer. The second method used sequential digital gamma camera images of the kidneys to determine fractional accumulation of the total dose of the tracer in the kidneys (percentage of injected dose, gamma camera) from 0 to 10 minutes after radionuclide administration. Linear correlation among the 3 methods was determined. Mean (+/- SD) GFR, using the inulin clearance method, was 154.67 +/- 42.28 ml/min/100 kg of body weight. Mean GFR, using the 2-compartment blood clearance curve, was 146.92 +/- 27.49 ml/min/100 kg. Mean GFR, using percentage of injected dose (gamma camera method) was 154.7 +/- 22.00 ml/min/100 kg. The percentage of injected dose (gamma camera method) did not correlate significantly to the inulin clearance results. However, a significant (r = 0.666, P < 0.018) correlation was observed between the inulin method and the (99m)Tc-DTPA blood clearance method. Significant (P < 0.0001) difference also was observed in the split function of the equine kidneys, with GFR of the right kidney contributing 60.1 +/- 9.12% of the total function, as determined by (99m)Tc-DTPA gamma camera imaging. Because the (99m)Tc-DTPA blood clearance method does not require urine collection, it may be a more practical procedure to measure GFR in the horse.

Zoometric measurements and bioelectrical impedance analysis were evaluated as methods of body composition determination in healthy cats. Zoometric and impedance measurements were taken on 22 anesthetized adult cats of various ages, genders, breeds, and body weights. The cats were then euthanatized. The bodies were processed through a tissue homogenizer and free-catch specimens were taken, freeze-dried, and analyzed for total body water, protein, fat, potassium, and ash content. Stepwise regression analysis was implemented to identify statistically significant relationships between the chemically determined dependent variables (total body water, protein, potassium, fat-free mass, fat mass, and percent body fat) and the zoometric measurements, with or without bioelectrical impedance analysis. Statistical analysis revealed high correlations between the dependent variables and the corresponding predicted values of those variables. Body weight alone was a poor predictor of body composition in these cats. On the basis of these findings, we suggest that zoometric and bioelectrical impedance measurements may serve as practical, noninvasive, simple, and accurate methods for estimating body composition in domestic cats.

Six nontrained mares were subjected to steady-state, submaximal treadmill exercise to examine the effect of exercise on the plasma concentration of atrial natriuretic peptide (ANP) in arterial, compared with mixed venous, blood. Horses ran on a treadmill up a 6 degree grade for 20 minutes at a speed calculated to require a power equivalent to 80% of maximal oxygen uptake. Arterial and mixed venous blood samples were collected simultaneously from the carotid and pulmonary arteries of horses at rest and at 10 and 20 minutes of exercise. Plasma was stored at -80 degrees C and was later thawed; ANP was extracted, and its concentration was determined by radioimmunoassay. Exercise caused significant (P < 0.05) increases in arterial and venous plasma ANP concentrations. Mean +/- SEM arterial ANP concentration increased from 25.2 +/- 4.4 pg/ml at rest to 52.7 +/- 5.2 pg/ml at 10 minutes of exercise and 62.5 +/- 5.2 pg/ml at 20 minutes of exercise. Mean venous ANP concentration increased from 24.8 +/- 4.3 pg/ml at rest to 67.2 +/- 14.5 pg/ml at 10 minutes of exercise and 65.3 +/- 13.5 pg/ml at 20 minutes of exercise. Significant differences were not evident between arterial or mixed venous ANP concentration at rest or during exercise, indicating that ANP either is not metabolized in the lungs or is released from the left atrium at a rate matching that of pulmonary metabolism.

Platelet aggregation and adenosine triphosphate (ATP) release were measured by use of the impedance method in blood samples obtained from 25 adult female Beagles before and after sedation with acepromazine (0.13 mg/kg of body weight) and atropine (0.05 mg/kg), and during general anesthesia. General anesthesia was induced by IV administration of thiamylal (average dosage, 2.1 mg/kg, range, 1.2 to 4.2 mg/kg) and was maintained with halothane in oxygen. Samples of jugular venous blood were obtained from each dog, using citrate as anticoagulant. Platelet count was done on each sample. Platelet aggregation and ATP released from the aggregating platelets were measured within 2.5 hours of sample collection, using a whole-blood aggregometer. Adenosine diphosphate (ADP) or collagen was used as aggregating agent. For each aggregating agent, platelet aggregation and ATP release were measured over 6 minutes. After sedation with acepromazine and atropine, significant (P < 0.01) reduction was observed in platelet count (from median values of 341,000 cells/microliter to 283,000 cells/microliter) and in the ability of platelets to aggregate in response to ADP (from 14.0 to 7.0 Ohms). During the same period, maximal release of ATP in response to collagen also was reduced (from 5.56 micromoles to 4.57 micromoles; P < 0.01); however, this difference ceased to be significant when ATP release was normalized for platelet count. During general anesthesia and surgery (200 minutes after sedation), platelet count and aggregation responses to ADP and collagen had returned to presedation values. None of the dogs in this study appeared to have hemostasis problems during surgery. In conclusion, sedation with acepromazine and atropine induces measurable inhibition of ADP-induced platelet aggregation that resolves during subsequent general anesthesia and surgery. Transient inhibition of platelet aggregation is not manifested by a change in gross hemostasis during surgery.