Equine articular chondrocytes were isolated from explant cartilage cultures by digestion in a 0.075% collagenase solution for 15 to 19 hours. Cartilage from late-term fetal and neonatal foals resulted in mean chondrocyte yield of 51.99 X 10(6) cells/g of cartilage (wet weight), compared with a yield of 17.83 X 10(6) cells/g for foals 3 to 12 months old. Propagation of chondrocytes in monolayer and 3-dimensional culture was accomplished, using Ham's F-12 as the basal medium, with supplements of fetal bovine serum (10%), ascorbic acid, alpha-ketoglutarate, and L-glutamine. The medium was buffered with HEPES, and penicillin and streptomycin were added for microorganism control. In primary monolayer cultures of freshly isolated chondrocytes, the population doubling time was approximately 6 days. Dedifferentiation of chondrocytes toward a more fibroblastic-appearing cell was observed after the fifth passage (subculture), but was hastened by lower cell-plating density. Chondrocytes were frozen for periods of up to 9 months, using 10% dimethyl sulfoxide as the cryoprotectant. Cell viability of late-term fetal and neonatal foal chondrocytes after storage at -196 C decreased from 86% at 3 weeks to 31% at 12 weeks. Viability of cells derived from older foals and young adult horses was considerably better than that of cells from neonatal foals. Frozen chondrocytes can be stored for extended periods and thawed for immediate implantation or can be sustained in vitro in monolayer or 3-dimensional culture. Such cultures would be suitable for cartilage resurfacing experiments or in vitro assessment of various pharmaceuticals.

Affinity chromatography on heparin sepharose was used to identify 2 lipolytic enzymes in heparinized plasma from horses. One enzyme was typical of hepatic triglyceride lipase (HTGL), because it was resistant to inactivation by high concentrations of NaCl, and it did not require the addition of serum for activity. The other enzyme was identified as lipoprotein lipase (LPL), because of its inactivation at NaCl concentrations in excess of 0.2M, and its dependency on addition of serum as a source of apolipoprotein C-II activator. The enzymes were purified by 347- (HTGL) and 442- (LPL) fold, with yields of 54 and 58%, respectively. The partially purified enzymes were used to design incubation conditions that gave optimal activities for each enzyme in vitro. A selective assay was then developed for direct measurement of LPL and HTGL activities in heparinized plasma from horses. Analysis of HTGL took advantage of the almost complete inactivition of LPL when serum cofactor was excluded from the assay at the NaCl concentration that gave optimal HTGL activity. Prior incubation of heparinized plasma with sodium dodecyl sulfate to inhibit HTGL was necessary for measurement of LPL, because HTGL retained 67% of its activity at the NaCl concentration required for optimal LPL activity. Activity of each enzyme was measured in heparinized plasma from 12 Shetland ponies. The mean activity +/- SD for LPL was 3.22 +/- 1.04 micromoles of fatty acids/ml of heparinized plasma/h (micromoles of FA/ml/h). The mean activity for HTGL was 4.9 +/- 1.56 micromoles of FA/ml/h. The performance of the assay was assessed by replicate analysis of pools of each enzyme with high and low activities. The intra-assay coefficient of variation ranged between 3.4 and 8.7% (n = 10), and the interassay coefficient of variation ranged between 5.2 and 10.7% (n = 7) for the same pools analyzed over 7 weeks.

The ultrastructural injury that develops sequentially in the ascending colon during experimentally induced ischemia was examined in 6 halothane-anesthetized horses. Colonic ischemia was created by 2 types of vascular occlusion 24 cm proximal and distal to the pelvic flexure. In all horses, transmural vascular compression was created. The colonic venous circulation was obstructed in 3 horses, whereas in the other 3 horses, arterial and venous circulation was obstructed. Two additional horses were anesthetized as controls for determination of any morphologic alterations associated with the experimental protocol. Full-thickness colonic biopsy specimens were obtained from the antimesenteric border of the pelvic flexure at 0, 0.25, 0.5, 1, 1.5, 1.75, 2, 2.25, 2.5, 3, 3.5, 4, 4.5, and 5 hours during occlusion, and were studied by light and transmission electron microscopy. Morphologic alterations did not develop in the colon of control horses. Mucosal congestion was observed by light microscopy in the colon of horses with experimentally induced ischemia, but congestion developed early in those with obstructed colonic venous circulation, compared with those having arterial and venous obstruction. Inter- and intracellular vacuolation and loss of staining initially resulted in groups of 3 to 5 superficial luminal epithelial cells. Alterations in the glandular epithelium lagged behind those in the superficial epithelium, but were observed in both groups by 2 hours of obstruction. These changes progressed to 100% sloughing of all epithelium by 4.5 to 5 hours. The initial cellular alterations, which were observed by transmission electron microscopy, developed at 0.25 hour in horses with colonic venous obstruction and was characterized by inter- and intracellular edema. By 1 hour in horses with colonic venous obstruction, vacuoles were observed within the basal lamina and some vacuoles contained intracellular organelles. These cellular changes were followed by increases in the intercellular gap and breaks between degenerating and more normal-appearing superficial epithelium, which led to sloughing of the epithelium. Endocrine cells by 1 hour also had evidence of ischemic injury. Injury to the vascular circulation, including congestion and platelet accumulations within the mucosal capillaries was apparent by 0.25 hour in horses with venous obstruction. By 1 to 1.5 hours in both groups of horses with experimentally induced ischemia, loss of vascular integrity and leukocyte migration frequently were observed. Platelets, proteinaceous material, and cellular debris continued to accumulate, and by 2.25 hour capillary plugging frequently was observed. These results indicated that the initial ultrastructural injury in the ischemic colon consisted of degenerative changes in epithelial cells, which led to sloughing of degenerating and necrotic cells. Although injury between the 2 types of vascular obstruction differed, end results were similar. Ischemic vascular injury may lead to further vascular thrombosis and necrosis, resulting in an irreversible injury or contribute to difficulty in medically managing horses with natural ischemia during the perioperative period.

Ochratoxin A (OA) was incorporated in the diets of growing gilts (mean body weight, 20.1 kg) at a concentration of 2.5 mg of OA/kg of feed and was fed continuously for 35 days. Humoral and cell-mediated immunologic measurements were evaluated to determine the effects of OA on immune function in swine. Cutaneous basophil hypersensitivity to phytohemagglutinin (PHA), delayed hypersensitivity to tuberculin, PHA-induced lymphocyte blastogenesis, interleukin-2 production, total and isotype immunoglobulin concentrations, antibody response to chicken RBC, and macrophage activation were used to evaluate immune function. Gilts treated with OA had reduced cutaneous basophil hypersensitivity response to PHA reduced delayed hypersensitivity to tuberculin, decreased stimulation index for lymphoblastogenesis, decreased interleukin-2 production when lymphocytes were stimulated with concanavalin A, and decreased number and phagocytic activity of macrophages. Differences were not observed for total and isotype immunoglobulin concentrations, or humoral hemagglutination (chicken RBC) titer. These data indicate that OA may suppress cell-mediated immune response in growing swine.

Hematologic values arid cellular morphologic features were evaluated for 38 healthy adult llamas. Reference ranges were determined for PCV, reticulocyte concentration, leukocyte concentration, and leukocyte differential counts. The approach used in this study was to focus on hematologic values that may be determined by use of techniques readily available to the practicing veterinarian and nonveterinary laboratory. Unique cellular morphologic features commonly observed and interpreted as normal included large granular lymphocytes, hyposegmented eosinophil nuclei, folded erythrocytes, and hemoglobin crystals.

The effect of IV administration of the alpha2-adrenoceptor agonist xylazine hydrochloride (0.5 mg/kg of body weight) was examined in ponies with recurrent obstructive pulmonary disease, commonly called heaves. Six ponies with the disease (principals) were studied during clinical remission and during an acute attack of airway obstruction precipitated by stabling and feeding of dusty hay. Six control ponies were also studied. In principal ponies with airway obstruction, xylazine administration significantly (P < 0.05) decreased pulmonary resistance and increased dynamic compliance, but did not affect PaO2 or PaCO2. The alpha 2-antagonist yohimbine blocked the pulmonary effects of xylazine. Administration of saline solution was without effect in both groups of ponies at all periods and xylazine did not have effect in controls or in principals in clinical remission.

We tested the hypothesis that treatment of growing, susceptible (to hip dysplasia) pups by IM administration of glycosaminoglycan polysulfates would mitigate the signs of incipient hip dysplasia. In 1 experiment, 7 pups, selected at random from 2 litters, were administered glycosaminoglycan polysulfates (2.5 mg/kg of body weight, IM) twice weekly, and 7 control pups from the same litters were given sterile buffered 0.9% saline solution from the age of 6 weeks to 8 months. Hip joints were examined by radiography, with pups in the standard, limbs-extended position. At 8 months of age, all pups in this experiment did not manifest femoral head subluxation radiographically. The Norberg angle, a measure of coxofemoral congruity, improved from a mean +/- SEM value of 102 degrees +/- 1 degree in controls to 106 degrees +/- 1 degree in treated pups (P = 0.008). Pups were not subjected to necropsy. In the second experiment, 8 pups were selected at random from 2 litters and were administered 5 mg of glycosaminoglycan polysulfates/kg, IM, twice weekly from 6 weeks to 8 months of age. Similarly, 8 control pups were administered saline solution. At 8 months of age, hip joints were examined by radiography with pups in the standard position; at necropsy, intra-articular tissues were evaluated macroscopically and biochemically. Of 8 treated pups, none had subluxation radiographically, whereas 4 of 8 control dogs had femoral head subluxation. Mean Norberg angle on the radiographs was 109.7 degrees +/- 1.6 degrees for the treated group and was 101.5 degrees +/- 1.6 degrees for controls, representing a mean improvement in coxofemoral congruity of 8.2 degrees in the treated pups. The radiographic diagnosis (normal vs dysplastic) and the Norberg angle measurements were significantly (P = 0.04 and 0.002, respectively) different for treated and control pups. At necropsy, 1 of 8 treated pups had cartilage degeneration, whereas 4 of 8 control pups had cartilage degeneration. The mean pathologic score determined for the hip joints of treated pups was 1.6 +/- 0.8, whereas for those of controls, the score was 3.3 +/- 1.2 (P = 0.09). Normal (disease-free) pups had hip pathologic scores of zero. The mean fibronectin content of femoral head articular cartilage was reduced from 2.19 +/- 0.61 microg/mg in nontreated pups to 0.59 +/- 0.56 microg/mg for treated pups (P = 0.04). Fibronectin content was used as a measure of the extent of cartilage degeneration, and the cartilage of disease-free hip joints contained 0.32 +/- 0.03 microg/mg. The mean proteoglycan content of the cartilage was unaffected by drug treatment. A trend was evident for lower synovial fluid volume and lower ligament volume (more normal volumes) in treated pups, but the differences were not statistically significant. Hip joint laxity was assessed by use of a distraction method during radiogaphy of pups in experiments 1 and 2. The differences in laxity determinations between the treated and control pups were not statistically significant. Taken together, the data indicated that IM administration of gycosaminoglycan polysulfates from 6 weeks to 8 months of age in growing pups that were susceptible to hip dysplasia resulted in less sublaxation, as determined from the standard radiographic projection. Treated pups had closer coxofemoral congruity when they were 8 months old (P < 0.05); at necropsy, the joint pathologic scores of treated pups indicated a trend toward improvement (P < 0.09), but the differences were not statistically significant. The mechanism of action for this drug effect is unknown.

Determination of antibodies to specific nuclear antigens, termed extractable nuclear antigen (ENA), was investigated in healthy dogs and in dogs with autoimmune, inflammatory, and neoplastic diseases. Using a counter-immunoelectrophoresis method, the dogs' sera were tested for antibodies against the nuclear antigens single-stranded DNA, Sm, Ro, La, ribonucleoprotein, Scl, and proliferating cell nuclear antigen. Antibodies to the Ro antigen were found in 1 dog with discoid lupus erythematosus, in 1 dog with pemphigus erythematosus, and in 1 dog with facial pyoderma and chronic superficial keratitis. In 15 dogs, antibodies were detected to ENA, but the precipitin lines were too weak to identify the specific ENA. These antibodies were found in some dogs with systemic lupus erythematosus, discoid lupus erythematosus, pemphigus erythematosus, dermatomyositis, vitiligo, lymphoma; in the dog with facial pyoderma and chronic superficial keratitis; and in 1 healthy dog. The highest percentage of dogs with antibodies to ENA in a large series (> 8) of this study was in dogs with systemic lupus erythematosus (4 of 13; 31%).

Ovine progressive pneumonia (OPP) is a lentivirus-induced disease of sheep in the United States that is similar, if not identical, to maedi/visna in many other countries. Prevalence estimates of seropositivity to this virus in sheep in the United States have been confined to limited groups or flocks of sheep and have varied from 1 to 90%. In this study of detection of antibodies against OPP virus, we found a lower general prevalence of antibodies to OPP virus in sheep than was previously reported. Of 16,827 sheep from 29 states in the United States, 26% were seropositive and 48% of 164 flocks that were tested had 1 or more seropositive sheep. Seropositivity to OPP virus for sheep within special categories was determined, although nonrandom samples that were available may have biased the results. Within regions of the United States, prevalence was highest in the Rocky Mountain region at 49% and lowest in the northern Atlantic region at 9%. Seropositive sheep were not evenly distributed among flocks, but were clustered in a few flocks of sheep. A high number of flocks had no or few seropositive sheep. Prevalence increased with age from 4% at < 1 year to a plateau of 34% at 4 years. Seropositivity was variable among breeds and was not associated with sex, wool class, or place of origin of ancestors.

The accuracy of ultrasonography in detection of feline hepatic lipidosis was studied retrospectively. The following ultrasonographic criteria were associated positively with severe hepatic lipidosis: the liver hyperechoic, compared with falciform fat; the liver isoechoic or hyperechoic, compared with omental fat; poor visualization of intrahepatic vessel borders; and increased attenuation of sound by the liver. In a group of 36 cats with clinically apparent hepatobiliary disease and in which liver biopsy was done, liver hyperechoic, compared with falciform fat, was the best criterion for diagnosis of severe hepatic lipidosis with 91% sensitivity, 100% specificity, and 100% positive predictive value.