Optimization of assay conditions for leukotriene B4 synthesis by neutrophils or platelets isolated from peripheral blood of monogastric animals.

Neutrophils are involved in inflammation through leukotriene (LT) production. The predominant proinflammatory leukotriene released from neutrophils is LTB4, which serves as a biological marker of inflammation. The purpose of this study was to optimize the conditions ex vivo for LTB4 production by neutrophils from horses and dogs, and platelets from chickens. Optimal production of LTB4 was characterized by incubation time (2.5, 5, 10, 15 or 20 min), temperature (25 or 37 degrees C), and calcium ionophore A23187 concentration (0.1, 1, 10 or 20 microM). Incubation longer than 2.5 min did not increase production of LTB4 in chickens or horses; in dogs, incubation for 2.5 and 10 min resulted in the highest concentrations of LTB4 (P

Neonatal isoerythrolysis in mule foals.

Four mule foals received anti-RBC antibody from their dam's colostrum. Two foals developed anemia, 1 developed severe thrombocytopenia, and 1 did not develop any clinical or laboratory abnormalities. All foals had the same donkey sire. Seven mares, including the dams of foals 1 to 4, bred to the donkey sire produced anti-RBC antibody. Two mares produced anti-RBC antibody to the donkey RBC on the first mating. The donkey sire and 18 of its offspring were found to have an RBC antigen unique to mules and donkeys. Thus, all matings of this donkey to horse mares were incompatible. The reason for the high rate of sensitization of mares bred to this donkey is unknown.

Ventricular tachycardia and myocardial dysfunction in a horse.

Ventricular tachycardia develops less frequently than supraventricular dysrhythmias and generally is more indicative of cardiac disease. The horse in this report had clinical signs of lethargy and hypophagia and was determined to have sustained ventricular tachycardia. Echocardiography was a valuable diagnostic tool and revealed an echodense area in the left ventricle that had subnormal ventricular performance. A primary heart problem of an inflammatory nature was suspected. The horse responded favorably to treatment with lidocaine, antimicrobials, and aspirin, as well as stall rest. The horse was used successfully as a sire and hunter-jumper after treatment, but subsequently died 2.2 years later of massive hemoperitoneum. Necropsy revealed an extensive area in the left ventricle that appeared thin and fibrotic.

Multifocal myositis associated with Sarcocystis sp in a horse.

Multifocal myositis was diagnosed in a 7-year-old Quarter Horse gelding on the basis of history and findings on physical examination, serum biochemical analysis, electromyography, and microscopic examination of frozen sections of muscle biopsy specimens. Histologic examination of the muscle specimen revealed multifocal accumulations of histiocytes, lymphocytes, and plasma cells, with attendant myofiber degeneration and necrosis. Parasitic cysts with morphologic characteristics of Sarcocystis sp were found in regions of myocyte degeneration and necrosis, and in regions of normal muscle. Based on a tentative diagnosis of Sarcocystis sp-induced myositis, the horse was treated with trimethoprim/sulfamethoxazole and pyrimethamine for 28 days, phenylbutazone for 5 days, and paddock rest for 30 days. At the end of treatment, the horse had gained 35 kg, its appetite had returned to normal, and muscle mass was returning to normal. Sarcocystis fayeri is the only Sarcocystis sp reported in equine muscle in the United States and is rarely associated with acute myositis or muscle atrophy. The development of clinical signs in this horse could have been the result of an underlying immunosuppression or infection with a particularly pathogenic strain or large infective dose of S fayeri.

Comparison of transverse facial venous sinus and jugular blood values in healthy and critically ill horses.

REASONS FOR PERFORMING STUDY: The transverse facial venous sinus (TFVS) can be used for blood collection in horses, but information on the validity of blood values from this site is limited. OBJECTIVES: To determine if packed cell volume (PCV), total solids (TS) and blood lactate concentrations in blood drawn simultaneously from a TFVS and jugular vein of critically ill horses are correlated and determine the effect of serial TFVS sampling on the same parameters in healthy horses. STUDY DESIGN: Prospective observational study. METHODS: Critically ill horses had simultaneous blood samples drawn from a TFVS and jugular vein. Blood was also drawn from the left TFVS and jugular vein from 6 healthy, adult horses q. 6 h for 24 h, then q. 24 h for 72 h. Blood was drawn from the right TFVS and jugular vein q. 24 h for 96 h. All samples were analysed for PCV, TS and blood lactate concentration. Data were analysed with 2-way repeated measures ANOVA. Significance was set at P≤0.05. RESULTS: There were no significant differences in PCV, TS or blood lactate concentrations of TFVS samples compared with jugular blood in critically ill horses. Serial TFVS sampling in healthy horses had no significant effect on TS or blood lactate concentrations. Although PCV in the TFVS was significantly lower than in jugular blood on serial sampling, the difference was not considered clinically relevant. CONCLUSIONS: Packed cell volume, TS and blood lactate concentrations were comparable between the TFVS and jugular vein.