Application of a galactosylceramidase microassay method to early prenatal diagnosis of Krabbe's disease

Changes of phospholipid-metabolizing and lysosomal enzymes in hypoglossal nucleus and ventral horn motoneurons during regeneration of craniospinal nerves

In order to study the biochemical changes associated with the cell body response to axonal crush injury, two systems, hypoglossal nucleus and spinal cord ventral horn, were used. The time intervals chosen were 7, 14, and 28 days after unilateral crushing of the right hypoglossal nerve and cervicothoracic nerves of the rabbit. Non-crushed, contralateral nerves were used as controls. Three groups of enzyme activities were tested: (a) phospholipase A2, acyl CoA:2-acyl-sn-glycero-3-phosphocholine acyltransferase, and choline phosphotransferase, as indicators of phospholipid degradation and biosynthesis; (b) seven hydrolases, namely, beta-D-glucuronidase, beta-N-acetyl-D-hexosaminidase, arylsulfatase A, galactosylceramidase, GM1-ganglioside beta-galactosidase, and acid RNase, as indicators of lysosomal activity; and (c) free and inhibitor-bound alkaline RNase, as an index of RNA metabolism. Changes could be grouped into three distinct patterns. Compared to contralateral control, choline phosphotransferase showed a slight increase, whereas phospholipase A2 and most lysosomal hydrolases showed a significant increase of activity, especially evident in the ventral spinal cord neurons 14-28 days after crushing. These changes correlate with known increases of membrane and organelle numbers, including lysosomes, in motor and sensory neurons during peripheral regeneration. In contrast, free and acid alkaline RNase activity significantly decreased in the injured sides compared to the controls. This change can probably be correlated with a stabilization of RNAs needed for increased protein synthesis. No changes in total alkaline RNase and acyltransferase activities in either regeneration model were observed.

Use of a fluorescent analogue of galactocerebroside for assay of galactocerebroside beta-galactosidase activity in skin fibroblasts from patients with Krabbe's disease

In order to diagnose Krabbe's disease (globoid cell leukodystrophy) or its carrier state in patients, galactocerebroside beta-galactosidase (galactosylceramidase) activity in cultured skin fibroblasts was measured with high-performance liquid chromatography using a fluorescent analogue of galactocerebroside, 1-O-galactosyl-2-N-(1-dimethylaminonaphthalene-5-sulfonyl)-sphingosine, as substrate. The enzyme activities in skin fibroblasts of the patients were found to be dramatically reduced when compared with those of controls. The assay can be adopted for diagnostic use in place of assays using radioisotope-labeled natural substrate.