Fig. 3. Determining minimal intranuclear genomic locus-PML body distances. Images of three-dimensionally preserved fibroblast nuclei collected by confocal microscopy (A) were processed using the image3D program to determine the x,y,z centroid co-ordinates of each PML body, MHC and EDC region in the nucleus (B). Using these coordinates it was possible to calculate the distance between each genomic locus and its closest PML body: MHC¹-PML=1.3 µm; MHC²-PML=3 µm; EDC¹-PML=2.3 µm; EDC²-PML=1.7 µm. Note that these images are 2D representations of 3D images. Bar, 5 µm.