Effects of D-galactose on the structure of nerve fibers in cerebellar white matter

Chronic administration of d-galactose (d-gal) has been widely reported to mimic brain aging,however,the potential mechanism underlying this phenomenon remains largely unclear. here,we investigated whether and how the nerve fibers are altered by long-term d-gal exposure. after mice were treated with d-gal (100 mg/kg/day,s.c.) for 8 weeks,the cerebellar white matter was processed for transmission electron microscopy. the mean diameter of the myelinated fibers and axons,as well as the mean thickness of the myelin sheaths,was measured. the fiber diameter was 6.80% higher in the d-gal group compared with the controls (p <0.01),with the peak diameter distribution shifting from1.0-1.2 μm in the control to 1.2-1.4 μm in the d-gal-treated group. such an increase was principally due to the increase in the myelin sheath (19.43%) and less in the axon (6.68%). myelin sheath thickening in d-gal-treated fibers may result from intra-myelin degeneration,such as loosening or splitting of the myelin lamellae,which ultimately alters the ratio of the sheath thickness to the fiber diameter. this is likely to impair impulse conduction velocity and play an important role in neural dysfunction in d-gal-treated animals. copyright © 2015 zoological society of pakistan.