Fraction of NMJs exhibiting one or more age-related alterations.

Columns 2 and 3 show the percentage of NMJs in young adult and old muscles that exhibit one or more of five structural features that characterize old NMJs in limb muscles: decreased AChR density, partial denervation, complete denervation, nerve terminal sprouting, fragmentation of the postsynaptic membrane. Column 4 and 5 show values for only the first four of these features, taking account of the fact that the postsynaptic membrane is fragmented in young adult NMJs in some muscles. Column 6 shows difference between values in columns 4 and 5. Values represent average (and SD) from at least 3 animals, with at least 100 NMJs counted per animal.