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Figure 1 Representative electron micrographs of biopsies taken before cardiac arrest from non-contracting areas of the anterior wall in two hibernation patients (magnification x 8,000). (A) Loss of contractile material in the vicinity of the nucleus (bottom right); sarcoplasmic reticulum is absent, as well as T-tubules. This space is filled with amorphous material (*). Only two rows of regularly arranged sarcomeres are visible. Small mitochondria are scattered throughout the cytoplasm, intermingled with irregularly shaped mitochondria; mitochondrial structure is preserved. A tortuous nucleus projecting (arrow) into the cytoplasm is observed. (B) Marked sarcomere disorganization, with abnormal Z-bands.