(c) Electron microscopy from ultrathin sections of resin-embedded heart biopsies of fed and starved WT, miR-212/132 null (KO) and cardiomyocyte-specific miR-212/132-overexpressing (TG) mice. White spots around the mitochondria (dark grey structures) are autophagic vacuoles. The electron-dense black spots shown with white arrows are autophagosomes. Scale bars, 4 μm. 