Figure 11.

Ultrastructural changes of the intercalated disk of 2-day overloaded hearts followed by overload removal. A 2-day overloaded heart shows thin and flat disks as observed in Figure 10 (A [2 days]) (I-mode). At 12 hours of overload removal, the ICD is thin with mostly short interdigitations, but there appear sporadic one-sarcomere-long interdigitations (B [2 days + 12 hours]) (r-V-mode). There appear “spaces” (S) surrounded by several spikes. At 1 day of overload removal, interdigitations elongate up to one sarcomere long bilaterally so that the ICD is folded to form one-sarcomere-deep grooves (G) and contra-grooves (G). Elongated interdigitation plus grooves results in ∼two-sarcomere-wide broad ICDs (C [2 days + 1 day]) (r-IV-mode). At 1.5 days of overload removal, the ICD is folded with short interdigitations keeping one-sarcomere-deep grooves and contra-grooves (G) (D [2 days + 1.5 days]) (r-III-mode). At 1.75 days of overload removal, the ICD is flat with one-sarcomere-long interdigitations (E [2 days + 1.75 days]) (r-II-mode). At 2 days of overload-removal, the ICD is thin and flat with short interdigitations, finishing one cycle of ICD changes during overload removal (F [2 days + 2 days]) (r-I-mode). Modes appeared in overload removal are similar and indistinguishable from those after overload. Longitudinal section to myocytes.