Figure 1. Electron micrographs from cardiac atria of control rats. A. A semithin section showing clarified intercalated discs (arrows), typical cross striations of muscle fibres (star), and many rows of mitochondria (double arrows). (B) blood capillary. B. The striation pattern (stars) with its typical alteration and dense mitochondria (M) rich in cristae (Bar = 200 nm). C. The striation pattern (stars) with its typical alteration and dense mitochondria (M) rich in cristae, euchromatic nucleus (N) with its nucleolus (n) and closely packed atrionatriuretic factor (ANF) granules (An) (Bar =1 µm). D. The striation pattern (stars) with its typical alteration and step-like intercalated disc (arrow) with adherent fascia (Bar = 500 nm). (x: 1000).