Figure 3.

Frozen muscle biopsies stored in liquid nitrogen for three (a, c, d) or four (b) years, then fixed with 2% paraformaldehyde and 0.5% glutaraldehyde, and embedded in LR White. a. In the cytoplasm, the sarcomeric organization is still recognizable and mitochondria are arranged in longitudinal lines. b. Myonuclei show excellent ultrastructural preservation and an EDTA-like effect (bleaching of condensed chromatin revealing ribonucleoprotein structural constituents). In the inset perichromatin fibrils (arrow), perichromatin granules (arrowheads) and interchromatin granules (IG) are clearly visible. c. Mitochondria are shrunken and homogeneously electron dense, devoid of any sign of membranous structures. d. The addition of CaCl₂ to the fixative solution did not significantly improve the ultrastructural preservation of mitochondria and only some mitochondria showed hardly recognizable cristae. Bars: a, b 1 µm; c, d, inset 0.5 µm.