Identification of mannosidosis heterozygotes — Factors affecting normal plasmaα-mannosidase levels

Publisher Website
Google Scholar
Abstract
Extract Mannosidosis is a lethal lysosolmal storage disease of Angus cattle, inherited as an autosomal recessive and assolciated with a deficiency elf the lysoso,mal enzyme α-mannosidase (Jolly, 1971 Finney, D. J. 1952. “The estimation of the median effective dose”. In Probit Analysis, 20–47. London: Cambridge University Press. In [Google Scholar] ; Holcking et al., 1972 Fisher, R. A. and Yates, F. 1963. Statistical Tables for Biological Agricultural and Medicine Research, 6th ed., 94–94. Edinburgh: Oliver and Boyd. [Google Scholar] ; Jolly et al., 1973 Hocking, J. D. , Jolly, R. D. and Batt, R. D. 1972. Deficiency of α-mannosidase in Angus cattle. Biochem. J., 128: 69–78. [Google Scholar] ). Affected calves fail to thrive and die usually within the first year of life. Many develop ataxia, into-ordination, head tremor and an aggressive tendency (Whittem and Walker, 1957 Jolly, R. D. 1970. Diagnosis and control of pseudolipidosis of Angus calves. N.Z. vet. J., 18: 228–229. [Taylor & Francis Online] [Google Scholar] ; Jolly, 1970 Jolly, R. D. 1971. The pathology of the central nervous system in pseudolipidosis of Angus cattle. J. Path., 103: 113–121. [Google Scholar] ). Investigations have shown that the genotype is very frequent in New Zealand and occurs also in Australia and Scotland (Jolly et al., 1973 Hocking, J. D. , Jolly, R. D. and Batt, R. D. 1972. Deficiency of α-mannosidase in Angus cattle. Biochem. J., 128: 69–78. [Google Scholar] and unpublished data). Whereas diseased calves have negligible levels of tissue and plasma α-mannosidase. heterozygous animals have less than half the normal plasma level elf this enzyme (Hocking et al., 1972 Jolly, R. D. , Tse, C. A. and Greenway, R. M. 1973. Plasma α-mannosidase activity as a means of detecting mannosidosis heterozygotes. N.Z. vet. J., 21: 64–69. [Taylor & Francis Online] [Google Scholar] ; Jolly et al., 1973 Hocking, J. D. , Jolly, R. D. and Batt, R. D. 1972. Deficiency of α-mannosidase in Angus cattle. Biochem. J., 128: 69–78. [Google Scholar] ). This observation has formed the basis for a test to identify animals heterozygous for this lethal disease from otherwise phenotypically normal animals. During evaluation studies, it has become evident that various factors influence the normal range of plasma α-mannosidase values and that this variability must be taken into account in interpretation of tests. Some of these factors, such as age and sex, have previously been reported (Jolly et al., 1973 Hocking, J. D. , Jolly, R. D. and Batt, R. D. 1972. Deficiency of α-mannosidase in Angus cattle. Biochem. J., 128: 69–78. [Google Scholar] ). The present paper extends this information and discusses ways of minimizing these variations in regard to heterozygote testing.