Table 1.
Characteristics of the three myelinated fiber sizes in the young and elderly groups
| Fiber size | Large myelinated fiber | Medium myelinated fiber | Small myelinated fiber | Regression coefficient | Intercept | R2 | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Group | Young (20 weeks old) | Elderly (90 weeks old) | Medium myelinated fiber | Elderly (90 weeks old) | Young (20 weeks old) | Elderly (90 weeks old) | Young (20 weeks old) | Elderly (90 weeks old) | Young (20 weeks old) | Elderly (90 weeks old) | |
| Fiber diameter (μm)a,b,c | 7.67 ± 0.54 | 4.42 ± 0.27** | 3.96 ± 0.09 | 2.33 ± 0.09** | 3.12 ± 0.06 | 1.50 ± 0.04** | −2.27 | −1.46 | 9.46 | 5.67 | 0.54 |
| Myelin thickness (μm)a,b,c | 1.13 ± 0.06 | 0.81 ± 0.04** | 0.65 ± 0.03 | 0.51 ± 0.01** | 0.50 ± 0.01 | 0.37 ± 0.01** | −0.32 | −0.22 | 1.40 | 1.00 | 0.52 |
| Axon diameter (μm)a,b,c | 5.02 ± 0.45 | 2.81 ± 0.21** | 2.23 ± 0.07 | 1.31 ± 0.06** | 1.63 ± 0.05 | 0.76 ± 0.03** | −1.69 | −1.02 | 6.34 | 3.67 | 0.46 |
| Myelin perimeter (μm)a,b,c | 21.85 ± 1.76 | 14.08 ± 0.80** | 10.99 ± 0.38 | 7.89 ± 0.22** | 7.69 ± 0.26 | 5.41 ± 0.13** | −6.57 | −4.34 | 26.99 | 17.80 | 0.47 |
| Axon perimeter (μm)a,b,c | 16.06 ± 1.40 | 9.29 ± 0.65** | 7.43 ± 0.35 | 4.46 ± 0.19** | 5.63 ± 0.29 | 2.70 ± 0.08** | −5.21 | −3.3 | 20.12 | 12.07 | 0.46 |
| G-ratioa | 0.62 ± 0.01 | 0.61 ± 0.01 | 0.56 ± 0.01 | 0.56 ± 0.01 | 0.52 ± 0.01 | 0.51 ± 0.01 | −0.05 | −0.05 | 0.67 | 0.66 | 0.21 |
Fiber diameter, myelin thickness, axon diameter, myelin perimeter, axon perimeter and G-ratio of the young and elderly groups for the three myelinated fiber sizes (large, medium, and small myelinated fibers). Regression coefficients and intercepts indicate those of regression lines on total fiber diameter, myelin thickness, axon diameter, myelin perimeter, axon perimeter, and g-ratio for the young and elderly groups. R2 indicates determination coefficient of a two-way ANOVA
** Significant difference between the young and elderly groups with Tukey–Kramer post hoc test (P < 0.01). Values of fiber diameter, myelin thickness, axon diameter, myelin perimeter, axon perimeter and g-ratio for the young and elderly groups according to fiber size (large, medium, and small myelinated fibers) are presented as mean ± SEM
aMain effect on the size myelinated fiber with a two-way ANOVA (P < 0.0001)
bMain effect on the group with a two-way ANOVA (P < 0.0001)
cInteraction of the size myelinated fiber and group with a two-way ANOVA (P < 0.01)