Fig. 6. Nucleocytoplasmic shuttling of NFATc1-GFP visualized in muscles of living mice. TA muscle transiently expressing NFATc1-GFP was observed in situ by using two-photon microscopy as described in Materials and Methods, either during application or after suspension of low-frequency stimulation. (A,B) Micrographs depicting maximum-intensity projections of either 15 confocal sections of individual fibers taken at the indicated time points after start (A) or suspension of low-frequency stimulation (B); bar, 25 µm. (C) Graphs show the mean fluorescence intensity of 30 (import, n=3 fibers) or 49 nuclei (export, n=3 fibers). Data (mean ± s.e.m.) were obtained from background-corrected sum plots and were either normalized to the 60-minute values (import, left panel) or 0-minute values (export, right panel). (D) High-resolution confocal micrographs of individual nuclei showing the concentration of NFATc1-GFP in punctuate structures. Bar, 5 µm.