Dpx mounting medium for histology

EDL muscles were quickly dissected from sacrificed mice or rats, pinned on Sylgard dishes, fixed at room temperature with 3.5% glutaraldehyde in 0.1 M NaCaCO buffer (pH 7.2), and stored in the fixative at 4 °C before embedding. Fixed muscles were then post-fixed, embedded, stained en-block, as described previously [15 (link)]. For TT staining, specimens were post-fixed in a mixture of 2% OsO₄ and 0.8% K₃Fe (CN)₆ for 1–2 h followed by a rinse with 0.1M NaCaCO buffer with 75 mM CaCl₂. For histological examination, 700 nm thick sections were stained in a solution containing 1% Toludine blue O and 1% Sodium Borate Tetra in distilled water for 3 min on a hot plate at 55–60 °C. After washing and drying, sections were mounted with DPX mounting medium for Histology (Sigma-Aldrich, Milan, Italy) and observed with a Leica DMLB light microscope (Leica Microsystem, Vienna, Austria). For EM, ultrathin sections (~50 nm) were cut using a Leica Ultracut R microtome (Leica Microsystem, Vienna, Austria) with a Diatome diamond knife (Diatome, Biel, Switzerland) and double-stained with uranyl acetate and lead citrate. Sections were viewed in a FP 505 Morgagni Series 268D electron microscope (FEI Company, Brno, Czech Republic), equipped with Megaview III digital camera (Olympus Soft Imaging Solutions, Munster, Germany) and Soft Imaging System at 60 kV.