Metabolic responses to ammonium acetate infusion in exercising horses.

The relationship between elevated plasma ammonia (NH3) levels, fatigue development and muscle metabolism were examined in horses during a submaximal fatigue test. Eight Quarter Horse mares were intravenously infused prior to exercise with either sodium acetate (control) or ammonium acetate (AMINF), and exercised to fatigue on an 11% grade treadmill, carrying 27 kg of lead. Time to fatigue was not different (P greater than 0.05) between groups. Intramuscular NH3 and lactate increased (P less than 0.001) during exercise; however, the treatment did not (P greater than 0.05) affect either. A treatment by exercise interaction (P less than 0.01) occurred for plasma NH3. The reciprocal relationship between changes in plasma and intramuscular alanine (ala) and glutamate (glu) indicated activation of the glucose-alanine cycle. Plasma glutamine (gln) increased (P less than 0.001) during exercise; however intramuscular gln was not (P greater than 0.05) altered. The excretion of urea-N was depressed as a result of exercise while the orotic acid/creatinine ratio did not (P greater than 0.05) change. The amino acids and urinary metabolites were not (P greater than 0.05) affected by treatment. These results did not show any metabolic evidence for a role of increased plasma NH3 levels in fatigue development. However this study did provide insight into other aspects of nitrogen metabolism during exercise in the horse.     

Serum liver enzyme and histopathologic changes in calves with chronic and chronic-delayed Senecio jacobaea toxicosis.

Progressive changes in serum enzyme activity and liver histologic features were monitored in calves fed tansy ragwort (Senecio jacobaea)-contaminated pellets. The experiments were designed to simulate natural intoxicant ingestion conditions in relationship to the dose and duration of exposure to the toxic plant to correlate early laboratory diagnostic changes with the natural progression of the disease, thereby facilitating early diagnosis and intervention by veterinary clinicians. Eight calves were fed tansy ragwort and 4 additional calves served as controls. In group 1, 4 calves were continuously fed dried tansy ragwort mixed in a pelleted feed at a 5% concentration by dry weight until terminal liver disease developed. Serum liver enzyme (alkaline phosphatase, glutamate dehydrogenase, and gamma-glutamyltransferase) activities were monitored at weekly intervals in these calves and in the 2 controls. In group 2, 4 calves were fed the same contaminated feed for only 60 days, with return to normal feed for the duration of the trial. Two additional calves served as controls. Their liver enzyme activities were monitored every other week in conjunction with percutaneous liver biopsies. All 8 calves fed tansy ragwort-contaminated pellets developed terminal hepatopathy in either a chronic pattern (n = 6) or a chronic-delayed pattern (n = 2), with the onset of a moribund state or sudden death at 11 to 17 weeks and 27 to 51 weeks, respectively. The calves were euthanatized when classic terminal signs of hepatic encephalopathy first became evident. The clinicopathologic patterns of chronic and chronic-delayed toxicoses were typical of over 5,000 cases of field tansy toxicosis diagnosed at the diagnostic laboratory. Serum glutamate dehydrogenase was the first enzyme to increase in most animals, with a short-term increase to peak values followed by a rapid return to normal. This enzyme change was followed by increases in alkaline phosphatase and gamma-glutamyltransferase. Serum enzyme changes preceded development of recognizable histologic lesions. Vacuolar changes in hepatocyte nuclei, biliary hyperplasia, and fibrosis sequentially developed in liver biopsy specimens from each animal, whereas megalocytosis was not a predominant feature until necropsy. On the basis of our findings, we suggest that the optimal tests for diagnosis of pyrrolizidine alkaloid intoxication should consist of liver biopsy and determination of concurrent serum liver-enzyme activities.     

Polymorphism of the CD4 and CD5 differentiation antigens in cattle.

Monoclonal antibodies (mAbs) specific for bovine CD4 and CD5 antigens have been found to identify polymorphic determinants on these molecules. In the case of CD5, mAb IL-A67 recognises one allotypic form of the antigen while four other CD5-specific mAbs in the workshop (CC17, CC29, BLT-1 and 8C11) recognise a second allotype. The CD4-specific mAbs submitted to the workshop reacted with the cells of all animals tested. However, a further two mAbs (CC26 and IL-A18) specific for CD4 were found to react with cells only from about 85% of animals tested. Sequential immuno-precipitation experiments together with family studies showed that the allotypes of CD4 and CD5 are both inherited in a simple Mendelian manner and are co-dominantly expressed. One of the CD5 allotypes was not detected in Bos taurus animals while the gene frequency of the second allotype was only about 10% in the B. indicus animals tested. The gene frequency of the CD4 allotype detected by CC26 and IL-A18 was similar in the two sub-species.     

Further studies on the antinociceptive activity and respiratory effects of buprenorphine in sheep

The thermal and mechanical analgesic profile of buprenorphine at a dose rate of 1.5 micrograms/kg i.v. was investigated in five sheep. This dose produced significant analgesia for 40 min against the thermal stimulus, but no mechanical antinociception. A higher dose rate of 12 micrograms/kg also failed to produce antinociception to a mechanical stimulus. In addition, the effect of the drug (6 micrograms/kg) on respiratory gas tensions was determined and no significant changes were observed.     

Laboratory testing in pet avian medicine.

The importance of employing laboratory diagnostics in the examination of avian patients cannot be overemphasized. The physical examination alone is grossly insufficient. Many avian illnesses do not display external signs, and laboratory work is imperative in detecting them. Only after the assessment of various laboratory parameters can an examination be considered complete.     

Intestinal cellular reaction of cattle after infection by Fasciola hepatica]

Defence reactions of cattle against Fasciola hepatica take place not only in the liver but also on a prehepatic level. The aim of the present experiments is to identify and quantify the cellular response in the small intestine. Five groups of two bulls (Simmental x Red Holstein, 6 months old) were infected by oesophageal probe with metacercariae of F. hepatica (MC) according to two experimental procedures. Two groups of bulls served as controls. In the first experiment both infected groups received 1000 MC once or twice at an interval of five weeks. The intestinal tissue was taken before infection and 5, 10 and 19 weeks p.i., respectively 5 and 14 weeks p. reinf. (p.ri.). In the second experiment, three infected groups received 400, 2 x 400 MC (at an interval of five weeks) and 800 MC respectively. Biopsies were taken one week ante infectionem, 6, 11 and 19 weeks p.i., respectively 1, 6 and 14 weeks post reinfectionem (p. ri.). The biopsies of the small intestine were prepared for histology and the tissue sections stained as follows: Astra blue for mucosal mast cells (MMC), Lendrum for eosinophils (EOS) and Periodic Acid Schiff (PAS) for goblet cells (GC). The density of the three cell populations in the mucosa was determined microscopically and quantified. In both experiments the density of the MMC and EOS increased with each reinfection and depended on the infectious dose. There was no significant variation of the GC-numbers. The described intestinal cellular reactions suggest a participation of the small intestinal wall in the immunity against the common liver fluke.