Fig. 8. (A-C) A cardiomyocyte with sarcomeres containing varying amounts of GFP-tagged LIM-IB at the Z-lines. (A) GFP-LIM-IB fluorescence appears to increase from left to right in this field. (B) Actin staining is strong in the sarcomeres at the left side of the field (arrowheads), but decreases as GFP fluorescence increases (asterisk). (C) The merged LIM-IB fluorescence and actin staining are shown in the green and red channels, respectively. (D) Line plots along the long axis of the myofibril were used to quantitate fluorescence intensity of GFP incorporation and actin staining. Plots from the region marked by a white line in C are shown in D. The peak GFP intensity at the Z-line was measured, and the actin peaks in the associated half sarcomeres around the Z-line were measured along with the actin background staining intensity. The specific actin staining was taken as the difference between the peak and background levels. (E) Specific actin staining intensity is plotted versus the peak GFP-LIM-IB fluorescence at the Z-line for sarcomeres in the cell in A-C. There is a significant negative correlation between LIM-IB incorporation at the Z-line and actin content in the associated half sarcomeres (P<0.05).