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Figure 5: Geometric and structural response of a 10-month-old desmin-null fiber to tensile loading. The same region of the fiber, imaged using phase-contrast microscopy, is shown at five different deformations. Fiber strains, radial strains, and sarcomere lengths are reported to the right of the fiber for each deformation. The fiber displays misaligned Z-lines, but consistently increasing sarcomere strain and decreasing fiber diameter with increased fiber deformation with increased fiber deformation. Misalignment is characterized by a striking basketweave pattern where no clear Z-line orientation may be inferred. A sample region of the fiber that displays this pattern is marked with a white box, and may be compared to the well aligned region shown in Figure 4. The boxed region has been computationally enlarged 2x for clarity. Desmin-null fibers display dramatically more debris on their external membrane compared to wild-type fibers. This observation is consistent with the increased “stickiness” experienced during fiber dissection, possibly resulting from differences in extracellular matrix composition. Bar = 50 μm.