Figure 4: Representative views of ultrastructural organization of longitudinally sectioned sarcomeres of m. gastrocnemius (a, b) and cardiac muscle (c, d). (a, c) Control group; (b, d) flight group. The control m. gastrocnemius and cardiac muscle, as well as flight m. gastrocnemius, have similar ordered sarcomeric structures (Z-disks, M-lines, and A-, H-, and I-zones). In contrast, the flight cardiac muscle represents disorganized sarcomeric structure, with clearly visible interfilament holes (asterisks). M: mitochondria; g: glycogen granules; ER: endoplasmic reticulum. All scale bars = 500 nm.