Effects of isomeric butanols on ceramide formation in astrocytes. Astrocytes were prelabeled with [3H]-serine for 72 hours, washed and treated with 1-butanol ("1-But") or t-butanol ("t-But"). After (A) 1 hour and (B) 18 hours, the cells were extracted with methanol/chloroform (2:1), phospholipids were separated by TLC, and the radioactivity associated with ceramide and sphingomyelin was determined by liquid scintillation counting. Data (N = 8–10) are means ± S.E.M. and are expressed as [%] ceramide/sphingomyelin. Statistics: Repeated measures ANOVA, (A) F4,49 = 7.2, p = 0.0002; (B) F4,39 = 25.0, p < 0.0001. *, p < 0.05; **, p < 0.01 vs. controls ("Ctr"). #, p < 0.05; ##, p < 0.01 vs. effect of 1-butanol (Tukey-Kramer multiple comparisons test).