Metabolic labeling of lipids with radioactive serine in lymphoblastoid cells from HSN1 and healthy controls. Cells were incubated with L-[3H(G)]serine for 2.5 hours. Lipids were isolated by high-performance TLC as described in Methods. Lipid synthesis was expressed as counts per minute per milligram of protein. The mean values with SD from triplicate experiments are shown. *P < 0.01 vs. the healthy control levels. TSLs, total sphingolipids.