Abstract
The difficulties and hazards of prolonged tissue culture (3-6 wks.) needed to establish the prenatal diagnoses of the hereditary biochemical disorders of metabolism are well recognized. Direct fetal blood sampling for study of lysosomal enzymes should allow the prenatal diagnosis of many ‘storage’ disorders within 24 hours of amniocentesis. The normal range of specific activity (SA) for these enzymes in fetal serum need be established. The minimum volume of fetal serum required for, assay was 2.5-100 μl. Assays using 4-methylumbilliferyl glycosides as substrates, for hexosaminidase, glucuronidase, arylsulfatase, and mannosidase, were performed on 5 fetal sera (12-20 wks. gestation), 3 second trimester pregnancy sera, and 4 healthy adult sera. The total fetal serum protein (mean 40.7 mg/ml) was less than half the level of normal adult serum (91.0 mg/ml) and lower than mid-trimester pregnancy serum (74.7 mg/ml). The SA's of hexosaminidase in fetal serum (mean 38.4) was more than 3 times the adult control SA (11.4) and significantly more than the pregnancy sera (23.5). similar observations of increased SA for mannosidase were made in fetal serum. The SA of arylsulfatase was similar in fetal and pregnancy serum which were each almost 4 times the SA of normal adult serum. No difference was observed in the SA of glucuronidase in the 3 groups studied.
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