Abstract
Investigaltions to determine the effect of sample storage on the concentration of copper in liver tissue and on the activity of erythrocyte superoxide dismutase were undertaken in preparation for a study of blesbok (Damaliscus pygargus phillipsi) that were suspected to be suffering from copper deficiency. Two liver samples were collected from each of 20 culled blesbok in a manner that simulated the collection of biopsies from the live animal. These samples were stored either in 10% formalin or frozen at -20 degrees C until analysed 4 1/2 months later. The effect of different methods of sample storage on superoxide dismutase activity was determined. Erythrocytes collected from 3 Jersey cows and 5 culled blesbok were washed and divided into 0.5 ml portions, stored at room temperature (approximately 20 degrees C), in a refrigerator (4 degrees C), frozen at -20 degrees C in a freezer, and in liquid nitrogen (-200 degrees C). An analysis of superoxide dismutase activity was undertaken using a commercial assay kit at intervals of 2-4 days until the levels of activity had fallen significantly. The copper concentration in formalin-preserved liver samples was significantly lower than that measured in frozen liver tissue apparently as a result of leaching. The activity of superoxide dismutase in cattle blood was unchanged for 4 days at room temperature but fell appreciably after 2 days at 4 degrees C and -20 degrees C. Enzyme activity remained unchanged for 200 days in erythrocytes stored in liquid nitrogen. Superoxide dismutase activity levels in healthy blesbok were considerably lower than those measured in Jersey cows and remained unaffected for up to 6 days in samples stored at 4 degrees C and 20 degrees C. The level of activity fell significantly thereafter. Samples stored in liquid nitrogen were unchanged after 40 days.
Highlights
A condition similar to ‘swayback’ was observed in blesbok (Damaliscus pygargus phillipsi) in the Karoo Nature Reserve, Graaff Reinet (32°18’S, 24°32’E)
The mean liver copper concentration in formalin (2094.6 mmol/kg, SD = 927.4, n = 19) was significantly lower than the mean copper concentration measured in frozen livers (2274.4 mmol/kg, SD = 935.0, n = 19)
As the degree of leaching over time is likely to be variable, samples should be frozen if the liver copper concentration is to be measured
Summary
A condition similar to ‘swayback’ was observed in blesbok (Damaliscus pygargus phillipsi) in the Karoo Nature Reserve, Graaff Reinet (32°18’S, 24°32’E). Affected animals developed signs of posterior paresis that became more severe when they bolted at the approach of a vehicle. An animal was shot and found to be suffering from chronic copper deficiency with typical lesions of myelopathy and an apparently low copper concentration in the liver at autopsy[12]. Copper plays an essential role in the biochemistry of living organisms. The amounts needed are minuscule, it is an essential component of many enzymes and biological catalysts. A deficiency in copper can cause a range of clinical diseases, such as ‘swayback’, synonymous with ‘lamkruis’ or enzootic aWildlife Unit, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110 South Africa
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