Diabetes, Vol 29, Issue 1 60-67, Copyright © 1980 by American Diabetes Association
Diabetic neuropathy in the mutant mouse [C57BL/ks(db/db)]: a morphometric study
DM Robertson and AA Sima
Detailed studies of peripheral nerves were undertaken in the mutant
diabetic mouse of the [C57BL/ks(db/db)] strain using electrophysiologic and
morphometric techniques. Electrophysiologic studies showed severely
impaired motor nerve conduction velocity (MNCV), which developed promptly
during the early phase of the diabetic syndrome. Morphometric changes
occurred first after 20 wk of diabetes in both myelinated and unmyelinated
fibers. There were both loss and shrinkage of myelinated fibers, most
pronounced in the sural nerve and the ventral root. Changes appeared late
in the dorsal root and in the peroneal and vagus nerves. Unmyelinated
fibers showed both shrinkage and loss of axons, presumably involving
sympathetic and afferent somatic fibers. Teased fiber studies and
calculations of axon-myelin ratios confirmed our earlier suggestion that
the neuropathy is primarily axonal in nature. The temporal discrepancy
between functional and structural impairments in the present model strongly
suggests a metabolic cause of the early neuropathy. This was further
supported by the positive effect of insulin treatment on MNCV during the
early phase of diabetes, whereas, during the late phase, treatment failed
to show any effect.