A (from [113]), The intracellular distribution of total and active CaMKII in SANC. A top panel shows a uniform distribution of the total CaMKII immunolabeling; middle panel shows the localization of active CaMKII beneath the sarcolemmal membrane; bottom panel shows the negative control, i.e., in the absence of the primary antibodies. B (from [123]), RyR in single cells isolated from the guinea-pig SA node. C, Confocal image of SANC doubly immunolabeled for NCX and RyR. D, pixel-by-pixel fluorescence intensities of labeling along an arbitrary (white) line in panel C. The horizontal dashed lines show the average pixel intensity. E, Topographical profiles of the pixel intensity levels of each antibody labeling and overlay in the small SANC in panel C. The maximum height represents the brightest possible pixel in the source image. C-E from [122].