Figure 2.
Axonal calibers and axon number in lumbar roots of aging NF-null mutant animals. (A) Diameters of all myelinated axons were measured in the L4 ventral roots of the 2-yr-old animals shown in Fig. 1. Note the marked reduction of axons >5 μm in diameter in the NF-M and NF-M/H mutants accompanied by an increase in smaller diameter fibers. (B) Diameters of myelinated axons in the dorsal roots shown in Fig. 1 were obtained by randomly sampling at least 300 myelinated axons in each root as described in Materials and Methods. Note that in contrast to the ventral roots, the distribution of axonal diameters in the NF-M–null mutant is more similar to the NF-H and wild-type than to the NF-M/H. (C) Myelinated axons were counted in the 
ventral lumbar roots or the L4 dorsal roots 
of 2-yr-old wild-type and mutant animals. There were no statistically significant differences between the mutants and controls in any root.