Figure 4.

Frozen muscle biopsies stored in liquid nitrogen for one (a, b) or four (c, d) years, then fixed with 2% paraformaldehyde and 0.5% glutaraldehyde, embedded in LR White and processed for immunocytochemistry. Immunolabelling with anti-actin (a) and anti-myosin (b): both probes bind specifically myofibrils. The anti-polymerase II antibody (c) labels perichromatin fibrils (arrows), even when they associate to perichromatin granules (arrowhead); anti-snRNP antibody (d) is associated with perichromatin fibrils (arrows) and interchromatin granules (IG). Nu: nucleolus. Bars: 0.5 µm.