Table 4.
Effects of chronic overload on fast-twitch neuromuscular junctions in young adult and aged plantaris muscles.
| Pre-synaptic nerve terminal branching | |||||
|---|---|---|---|---|---|
| Variable | Young Control | Young Overload | Aged Control | Aged Overload | P value |
| Branch number | 7.8 ± 0.4 | 7.7 ± 0.4 | 7.6 ± 0.4 | 7.8 ± 0.5 | 0.98 |
| Total length of branching (µm) | 287.0 ± 20.3 | 290.7 ± 15.6 | 282.0 ± 23.6 | 298.3 ± 21.2 | 0.95 |
| Average length/branch (µm) | 41.1 ± 1.5 | 37.7 ± 2.4 | 37.1 ± 2.1 | 38.7 ± 1.8 | 0.93 |
| Branching complexity | 25.6 ± 3.1 | 26.0 ± 2.7 | 24.4 ± 2.9 | 26.3 ± 3.0 | 0.97 |
| Post-synaptic endplate structure | |||||
| Variable | Young Control | Young Overload | Aged Control | Aged Overload | P value |
| Total perimeter (µm) | 133.2 ± 28.1 | 142.0 ± 27.3 | 139.8 ± 38.1 | 186.1 ± 43.5 | 0.68 |
| Stained perimeter (µm) | 254.7 ± 9.6 | 259.7 ± 10.5 | 260.2 ± 15.3 | 272.6 ± 16.9 | 0.80 |
| Total area (µm²) | 660.7 ± 46.1 | 689.7 ± 64.5 | 671.7 ± 62.1 | 782.1 ± 97.5 | 0.60 |
| Stained area (µm²) | 528.1 ± 15.1 | 551.7 ± 15.2 | 528.4 ± 15.9 | 615.6 ± 22.3 | 0.72 |
| Dispersion (%) | 78.2 ± 2.3 | 81.4 ± 1.4 | 73.9 ± 3.2 | 70.0 ± 2.6 | 0.44 |
| Pre- to post-synaptic coupling | 2.0 ± 0.8 | 1.9 ± 0.5 | 1.9 ± 0.9 | 2.1 ± 0.8 | 0.99 |
Values are means ± SE.
Branching complexity = branch number × total branch leangth/100.
Dispersion = stained area/total area
Pre- to post-synaptic coupling = endplate’s stained area/total nerve terminal branch length.