Pre-mRNA Processing Is Partially Impaired in Satellite Cell Nuclei from Aged Muscles
Figure 2
Transmission electron micrographs. (a) Satellite cell bordering a myofiber. (b) Detail showing the nucleolus mostly composed of granular component (G); whereas the dense fibrillar component (D) is less abundant, note the small fibrillar center (arrowhead). Satellite cell nuclei from adult (c, e and g) and old (d, f and h) rats. (c and d) Quadriceps muscles, anti-polymerase II (12 nm), and anti-DNA/RNA hybrid (18 nm) antibodies: both antibody probes specifically label perichromatin fibrils (arrows). Note the clustered perichromatin fibrils in (d) (arrowhead). The interchromatin granules (IG) are unlabeled. (e, f) Biceps muscles, anti-snRNP antibody: perichromatin fibrils (arrows) and interchromatin granules (IG) are labeled. (g, h) Quadriceps muscles, anti-CstF antibody: gold grains specifically label perichromatin fibrils (arrows) and RNP tails rising from perichromatin granules (inset). Note the cluster of perichromatin fibrils in (h) (arrowhead). Interchromatin granules (IGs) are unlabeled. Ch: condensed chromatin. Bars: (a) 1 m; (b–h) 250 nm; inset 100 nm.
