Incorporation of radioactivity from U-14C-glucose into oligodendrocytes and myelin of quaking mice and their littermate controls.

Oligodendrocytes and myelin were purified from the cerebra of quaking mice and their littermate controls (11-60 days of age) after injecting the animals intraperitoneally with U-14C-glucose. A peak of incorporation of radioactivity in the lipid extract of oligodendrocytes of both quaking and normal mice at 16-18 days of age was found, suggesting that the onset of myelination in the cerebra starts approximately at the same time for quaking mice and their littermate controls. Nevertheless the level of incorporation per cell was lower in the oligodendrocytes of quaking mice (50% of the control). The pattern of incorporation into myelin during development was similar between the two strains, but the specific activity as measured in dpm/mg protein was higher in the myelin of young quaking animals (up to 16 days). Peaks of incorporation were found in cerebrosides and sulfatides of oligodendrocytes and myelin in normal controls at 18 days. In the quaking mice these peaks were absent in oligodendrocytes and much delayed in the myelin of the mutant. The results would suggest that the defect in the quaking mutant in respect to myelination is in oligodendrocyte metabolism and thus in an early stage of the assembly of the myelin membrane.