Figure 8. Ultrastructure of optic nerve axonal loss. A: One year after injection of scAAV-GFP, transmission electron micrographs disclosed optic nerve axons (a) of various sizes enveloped by myelin sheaths. Astroglial cell processes (g) coursed between fibers of the optic nerve. B: In this same animal, the opposite eye injected with the MTS scAAV mutant ND4 had a marked decrease in axonal density. Many empty spaces (e) were present where axons were apparently lost in these atrophic optic nerves and degenerating axonal profiles were evident (d). C: In a different animal, the optic nerve of the control eye injected with scAAV-GFP had normal axons (a) with the only empty space the lumen of a blood vessel (L). D: In this animal, the opposite eye injected with the MTS scAAV mutant ND4 had a marked decrease in axonal density. Many empty spaces (e) were present where axons were lost. a=optic nerve axon, e=empty space, g=astroglial process, d=degenerating axon, L=lumen.