TLC analysis of ceramides and gangliosides. (A) TLC analysis of free ceramides in myelin confirmed the presence of HFA-ceramide in Cgt-/- (lane 2) and its absence in Fa2h-/-/Cgt-/- myelin (lane 3). NFA-ceramide levels were slightly increased in Fa2h-/-/Cgt-/- mice (lane 3). Cer, ceramide. (B) The ganglioside pattern of purified myelin was not altered in Fa2h-/-/Cgt-/- (lanes 1 and 2) compared to Cgt-/- mice (lanes 3 and 4). The same amount of the major myelin ganglioside GM1 was found in both mouse lines, as well as in wild-type controls (lanes 5 and 6). The larger amount of the gangliosides GD1a, GD1b, and GT1b, which are major gangliosides of neuronal membranes, in the two mouse lines with less compact myelin are most likely caused by a higher proportion of axonal membranes in the myelin preparation.