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Table 1 Effect of aging on two-dimensional muscle fiber and endplate structures

From: Age-related changes in two- and three-dimensional morphology of type-identified endplates in the rat diaphragm

2-D Age (month) Muscle fiber type
I IIa IIx/b
Endplate area (μm2) 2 238 ± 62 314 ± 64 384 ± 77a
10 378 ± 90 496 ± 130 790 ± 145a,b
24 327 ± 94 457 ± 122 741 ± 218a,b
30 284 ± 83 434 ± 160 780 ± 240b
Endplate surrounding area (μm2) 2 321 ± 95 439 ± 115 543 ± 132a
10 588 ± 195 800 ± 300 1,435 ± 358a,b
24 529 ± 157 784 ± 234 1,344 ± 411a,b
30 462 ± 142 779 ± 281 1,475 ± 493a,b
Endplate density (%) 2 74.1 ± 7.7 71.5 ± 7.5 70.7 ± 8.5
10 64.3 ± 11.0 62.0 ± 11.8 55.1 ± 5.6
24 61.8 ± 8.0 58.3 ± 7.3 55.1 ± 7.1
30 61.5 ± 7.5 55.7 ± 7.4 52.9 ± 5.1b
Muscle fiber diameter (μm) 2 21.1 ± 2.9 30.3 ± 2.8a 39.1 ± 3.5a
10 25.2 ± 3.2 34.5 ± 3.1a 51.3 ± 7.4a
24 23.4 ± 3.2 33.6 ± 3.4a 47.6 ± 7.3a
30 21.3 ± 4.0 33.2 ± 3.3a 51.3 ± 6.5a,b
Normalized endplate area (μm2/μm) 2 11.3 ± 2.6 10.4 ± 2.0 9.8 ± 1.7
10 15.0 ± 3.6 14.4 ± 4.7 15.4 ± 3.3b
24 14.0 ± 3.4 13.6 ± 3.0 15.6 ± 3.2b
30 13.3 ± 2.8 13.1 ± 3.3 15.2 ± 2.6b
  1. Values are means ± standard deviation
  2. aSignificant difference (P < 0.05) vs. type I
  3. bSignificant difference (P < 0.05) vs. 2-month-old group