Structural alterations of the intramuscular nerves and junctional region in extraocular muscles of C57BL/Ks (db/db) diabetic mice.

The extraocular muscles of the C57BL/Ks (db/db) diabetic mutant mouse were examined by electron microscopy. The intramuscular myelinated nerves and the junctional apparatus of the singly and multiply innervated muscle fibers were found to exhibit various anomalies. Lamellated inclusion bodies were found in many of the Schwann cells of the myelinated nerve fibers; intra-axonal inclusion bodies resembling polyglucosan bodies were also observed. Junctional abnormalities consisted of various types of inclusion bodies within the junctional sarcoplasm and within sole-plate nuclei; in addition, hypertrophied endplates were observed and often penetrated by networks of axonal terminal branches. At times, pseudopod-like extensions of the junctional sarcoplasm encompassed and made protracted synaptic contacts with the incoming axons.