To determine the effects of long-term thyroxine treatment, histomorphometric analysis was performed on the pituitary and thyroid glands of healthy dogs, dogs treated for 9 weeks with a replacement dose of L-thyroxine, and dogs at 6 weeks after cessation of thyroxine treatment. In treated dogs, the volume density of thyrotropes decreased during thyroxine treatment and increased 6 weeks after cessation of treatment, compared with thyrotropes of healthy nontreated dogs. The activity of the thyroid gland was decreased in dogs during thyroxine treatment, as evidenced by decreases in epithelial volume density, epithelial height, and follicular area, and increase in colloid volume density, compared with thyroid gland activity in nontreated dogs. After cessation of thyroxine treatment, the thyroid gland had decreased colloid area, follicular area, and epithelial volume density, and increased interstitial volume density, compared with the thyroid gland of healthy nontreated dogs. Thyroxine treatment resulted in suppression of pituitary thyrotropes and thyroid follicular activity.

The response of blood neutrophils to the chemotactic peptide formyl-methyl-leucyl-phenylalanine varies among species. Our results indicate that this peptide does not activate the respiratory burst of porcine neutrophils. Specifically, concentrations less than or equal to 10-6M did not cause production of either superoxide or hydrogen peroxide. Studies designed to delineate the biochemical deficit responsible for these results indicated that these cells do not express specific chemotactic peptide receptors on the external surface of the plasma membrane. Although these data do not rule out the possibility that internal stores of chemotactic peptide receptor exist, attempts to induce expression of the receptor by priming the cells with either lipopolysaccharide or calcium ionophore were unsuccessful.

This work was an attempt to develop an in vitro adherence model for Mycoplasma hyopneumoniae, using monolayers of human and porcine lung fibroblasts and porcine kidney cells. Mycoplasma hyopneumoniae grown in Friis mycoplasma broth was radiolabeled with 35[S]-methionine, washed, concentrated, and inoculated on the monolayers. After 15 minutes of centrifugation to facilitate adherence, monolayers were washed 3 times, dissolved with 0.1N NaOH, and suspended in scintillation liquid, and the radioactivity was determined in a liquid scintillation counter. Adherence, measured as a percentage of counts added, varied according to the mycoplasma strain and the cell line used. Comparison of strains J, 144L, and 232 of M hyopneumoniae revealed 7.5 +/- 5.9, 31.9 +/- 13, and 9.6 +/- 5% adherence to porcine kidney cells, respectively. Slightly different, but proportionally the same relationships were obtained with swine or human fibroblasts. Adherence was decreased slightly by repeated washings of the mycoplasma-treated cell monolayers; however, a plateau was reached, indicating irreversibility of the adherence process. Pretreatment of cell monolayers with nonlabeled organisms substantially blocked adherence by labeled organisms. Dilution of labeled organisms resulted in an increased proportion adhering. Therefore, it appears that the adherence was a receptor-dependent event. Treatment of the mycoplasmas with trypsin prior to the inoculation of monolayers resulted in a marked reduction in adherence. Treatment of the mycoplasmas with hyperimmune swine serum against M hyopneumoniae or normal swine serum resulted in 80 to 90% reduction of adherence; however, no inhibition occurred when mycoplasmas were treated with purified IgG from the hyperimmune serum.

The influence of variable zinc content (29.1, 250, 1,000 and 2,000 mg/kg of dry weight) in a basic diet containing 7.7 mg of copper/kg on the ability of weanling foals to maintain normal copper balance was investigated. Serum copper and zinc concentrations were monitored, and terminal hepatic copper and zinc contents were measured in 4 weanling foals fed the basic diet containing 29.1 mg of zinc/kg and in 2 foals each fed the higher-zinc diets. Foals fed the lower-zinc diets (29.1 and 250 mg/kg) maintained normal serum copper and zinc concentrations for 14 to 15 weeks, whereas those fed the 2 higher-zinc diets became hypocupremic within 5 to 6 weeks and were lame within 6 weeks, owing to cartilaginous disease characteristic of osteochondritis dissecans. Serum zinc concentration in the foals fed the 2 higher-zinc diets increased to > 2 microgram/ml within 2 weeks. Foals fed the high-zinc diets became lame after serum copper concentration had remained at 0.3 microgram/ml for > 1 week. Serum copper concentration in these arthritic foals was less than or equal to 0.2 microgram/ml at the end of the study. In lame foals, fractures of the cartilage of the articular and growth physes occurred through the zone of hypertrophic cells, and varied from bilateral to unilateral and from small to large. Free masses and flaps of cartilage attached to one side were numerous.

Eight adult female cattle (6 Holstein, 1 Jersey, 1 Brown Swiss) were used to determine the antagonistic effects of tolazoline, an alpha 2-adrenoceptor antagonist, on xylazine-induced (via caudal epidural administration) depression of CNS, respiratory, and cardiovascular activity and rumen motility. A 2% solution of xylazine HCl was injected into the epidural space at the first coccygeal interspace, using a dosage of 0.05 mg/kg of body weight, diluted to a 5-ml volume with sterile water, and administered at a rate of approximately 1 ml/30 s. Eight minutes after xylazine injection, either tolazoline (0.3 mg/kg) or saline solution (4 ml) was administered IV. All 8 cattle were treated, using both regimens in a random sequence; at least 1 week elapsed between treatments. Epidurally administered xylazine induced caudal analgesia (S3 to coccyx), as evaluated by no response to superficial and deep muscular pinprick, and induced sedation, cardiopulmonary depression, and inhibition of rumen motility, but all cattle remained standing. Tolazoline effectively reversed xylazine-induced rumen hypomotility, and partially antagonized xylazine-induced cardiopulmonary depression without affecting sedation and desirable local (S3 to coccyx) analgesic effects.

A radiopaque marker was injected, using needles of various lengths, into the cervical musculature, the lumbar epaxial musculature, and the cranial and caudal muscular masses of the thighs of anesthetized dogs. After this procedure, the dogs were euthanatized and deep-frozen. The bodies were then sectioned, and the slices were radiographed to determine the fate of the injected material. Material that was injected into the neck or caudal region of the thigh was determined to be located in the muscle bellies or dispensed throughout the intermuscular fascial sheaths. In contrast, material injected into the lumbar area and cranial region of the thigh was located entirely in the muscle bellies. It was concluded that the best sites for injection in dogs are the lumbar epaxial musculature or the quadriceps femoris muscle when IM administration is imperative.

Samples of pleural fluid from 20 horses with effusive pleural diseases of various causes were evaluated; samples from 19 horses were used for the study. There were differences for pH (P = 0.001) and partial pressure of oxygen (P(O2)) between arterial blood and nonseptic pleural fluid (P = 0.0491), but there were no differences for pH, P(O2), partial pressure of carbon dioxide (P(CO2)) and concentrations of bicarbonate (HCO3-), lactate, and glucose between venous blood and nonseptic pleural fluid. Paired comparisons of venous blood and nonseptic pleural fluid from the same horse indicated no differences. There were differences (P = 0.0001, each) for pH, P(O2), P(CO2), and concentrations of HCO3- between arterial blood and septic pleural fluid. Differences also existed for pH (P = 0.0001), P(CO2) (P = 0.0003), and concentrations of HCO3- (P = 0.0001), lactate (P = 0.0051), and glucose (P = 0.0001) between venous blood and septic pleural fluid. Difference was not found for values of P(O2) between venous blood and septic pleural fluid, although 4 samples of septic pleural fluid contained virtually no oxygen. Paired comparisons of venous blood and septic pleural fluid from the same horse revealed differences (P < 0.05) for all values, except those for P(O2). These alterations suggested functional and physical compartmentalization that separated septic and healthy tissue. Compartmentalization and microenvironmental factors at the site of infection should be considered when developing therapeutic strategies for horses with septic pleural disease.

To investigate whether arthrographic findings had any prognostic value with respect to treatment and outcome of bilateral osteochondrosis, shoulder arthrograms (n = 80) from 40 dogs with bilateral lesions were evaluated. Arthrography was performed, using 1.5 to 4 ml of a 25% solution of meglumine-sodium diatrizoate, with admixture of 0.2 mg of epinephrine. A shoulder with signs of pain and lameness was surgically treated. The contralateral shoulder was treated conservatively, and the final outcome was compared with the arthrographic findings. In 37 dogs, signs of lameness and pain were associated with a loose cartilage flap and, in 3, with a detached cartilage flap. In 2 dogs, admitted with bilateral lameness, a loose cartilage flap was detected in both shoulders. Of 12 dogs with a detectable loose cartilage flap in the contralateral shoulder joint, 6 became lame 2 to 4 months after initial surgical intervention and needed bilateral surgery. In the contralateral joint, development of thick articular cartilage over the subchondral defect or a detached cartilage flap lodged in the caudal pouch of the shoulder joint was a favorable prognostic sign. Such dogs had no signs of lameness on the contralateral side during a follow-up period that ranged from 1 to 7 years.

Two African swine fever virus (ASFV) antigens were tested for use in an ELISA to detect antibody to ASFV. Antigens used were the cytoplasmic soluble fraction (CS-P) of infected cells grown in the presence of porcine serum and the semipurified viral structural protein VP73 (SVP73). Both antigens were tested by ELISA against 72 sera obtained during several ASF field episodes and from ASFV-inapparent carriers. Of the 72 sera, only 2.8% had positive results by ELISA against CS-P antigen; 60% of positive-reacting sera (to both antigens) had higher ELISA values when the CS-P antigen was used. Samples (with positive results) that reacted only to CS-P antigen had results confirmed by immunoblot analysis. Such sera reacted against ASFV-infection proteins IP25, IP25.5, and IP30, but not against IP73. In time-course experiments to detect appearance of ASFV-antibodies in infected miniature pigs, antibodies were detected by immunoblot analysis on postinoculation day (PID) 8. At that time, only the polypeptides IP25, IP25.5, IP30, and IP31 were recognized; IP73 and IP12 were first detected 3 and 4 days later, respectively. In the same experiments, ASFV antibodies were detected by ELISA, using CS-P or SVP73 antigens, on PID 7 and 9, respectively. These results could explain the percentage of sera not having positive results by ELISA using SVP73 antigen, if the sera were obtained from ASFV-infected pigs during the first days of infection before induction of antibody response against the IP73 protein. This feature makes the use of CS-P antigen advantageous in early serologic detection of AFSV-infected pigs.

Enzyme-linked immunosorbent assays were established to detect Breda virus antigen in feces and homologous antibodies of the IgG1, IgM, and IgA isotypes in serum. With the aid of solid-phase immune-electron microscopy, torovirions in fecal material were observed. The course of natural infection was studied in 10 sentinel calves that had been obtained from different farms, and housed together at 1 week of age. They were separated from other cattle until the age of 10 months. Up to the age of 4 months, all calves regularly excreted Breda virus in the feces. Irrespective of the existence of IgG1 isotype maternal antibodies, all calves had early IgM responses in serum, but lack of IgA seroconversion. In 7 calves, antibody titer decreased below detection, whereas 3 calves had an isotype switch, resulting in persistent IgG1 titer. After introduction into the dairy herd at 10 months of age, all calves had diarrhea, and shedding of Breda virus was observed in 8 of them. Seroconversion for all antibody isotypes was observed, indicating lack of mucosal memory. In contrast, coronavirus infection in the presence of maternal antibodies led to isotype switch in all calves but one, and a memory response was observed after introduction into the dairy herd.