Effective uptake of NgHexA by Sandhoff disease (SD) fibroblasts. The uptake by WT- and NgHexA into fibroblasts derived from an SD patient was analyzed as described under “Materials and Methods”. WTHexA and NgHexA were administered to SD fibroblasts. (a) The time-course was measured at 24-hour intervals for 72 hours [4-methylumbelliferyl N-acetyl-β--glucosaminide (4-MUG) activity, 200 nmol/hour]. (b) Dose dependency was analyzed for 72 hours after administration (4-MUG activity, 200, 400, or 600 nmol/hour). In another experiment, HexA (600 nmol/hour) was administered after treatment with 10 mmol/l M6P for 30 minutes. Error bars show ±SEM, ***P < 0.005 (Tukey's post hoc test).