Table 1.
Quantitative analysis of mitochondria, CRUs and maturation of SR-mitochondrial connectivity in FDB fibers (0.5 – 4 months of age)
| A | Ba | Ca | Da | Ea | |
|---|---|---|---|---|---|
| Age | Nearest distance between RyRs and mitochondrial outer membrane (nm)b | No. of CRUs/100 μm2c | No. of mitochondria/100 μm2c | % of mitochondria at the I bandd | No. of mito-CRU pairs/100 μm2e |
| 0.5 mo | —f | 21 ± 5 | 27 ± 7 | 52 | 7 ± 2 (26) |
| 1 mo | — | 43 ± 9 | 32 ± 9 | 76 | 13 ± 3 (41) |
| 2 mo | 131 ± 50 (269) | 69 ± 12 | 59 ± 13 | 88 | 38 ± 5 (64) |
| 4 mo | 128 ± 38 (297) | 88 ± 25 | 75 ± 24 | 99 | 60 ± 9 (80) |
| Average ± SD | 130 ± 45 (566) |
(Column A) The distance between sites of Ca2+ release and the nearest outer mitochondrial membrane was measured at 2 and 4 months of age by drawing a curved line as shown in Figure 1D. (Columns B and C) The number of CRUs and mitochondria per unit area increases progressively from 2 weeks to 4 months of age. Data are given as mean (± SD) number of CRUs and mitochondria per 100 μm2. (Columns D and E) Percentages of mitochondria located at the I band and number next to a CRUs. In Column E, the percentage of mitochondria coupled to CRUs is reported in parentheses. Both values increase progressively with age, indicating that in addition to an increase in number of mitochondria and triads, positioning of mitochondria to the I band and their association with triads also increase steadily during postnatal development.
a Sample size is 80 pictures/10 fibers/2 animals per time point.
b Values are the mean± SD, with the number of measurements in parentheses.
c Values are mean± SD.
d Values are the percentage of the total.
e Values are the mean± SD of the number of measurements, with the percentage of the total number of mitochondria paired to CRUs.
f —, not measured.