(A) Micrographs of HeLa nuclei with fluorescently labeled chromatin (H2B-GFP, green) and nucleoli (NPM-DsRed, red), and the overlay, under the following conditions: control, upon addition of blebbistatin, latrunculin A, nocodazole, -amanitin, flavopiridol, trichostatin A, and cycloheximide (at 30 min and 6.5 hr). (B) Histograms of the following measurements for all conditions (width indicates probability): nucleolar area normalized by nuclear area, , nucleolar eccentricity, , angle between the major nuclear and nucleolar axes, , the shortest distance from the nucleolar centroid to the nuclear envelope normalized by the nuclear circumference, , fraction of the nucleolar contour with negative curvature, , and number of continuous regions of negative curvature along the nucleolar contour, . All data collected in the nucleolar focal plane. Red dot, solid red line and dotted red lines indicate the mean, median and quartiles, respectively. Table 1 provides -values for all measured data with respect to the control. The number of nucleoli and cells are as follows: control ( 648, 208), blebbistatin ( 399, 127), latrunculin A ( 307, 104), nocodazole ( 310, 106), -amanitin ( 268, 95), flavopiridol ( 309, 105), trichostatin A ( 278, 95), and cycloheximide at 30 min ( 291, 91), and cycloheximide at 6.5 hr ( 294, 105). Scale bar, 5 µm.