Fig. 1. Micronucleus and macronucleus morphology. View of four micronuclei and one macronucleus. To display the spherical organization of nuclei, a series of equidistant images (optical sections) were collected using laster-scanning-microscopy. (a) Average intensity planar projections (green) from a series of 42 optical sections were displayed onto planes between the XY-, XZ-, YZ-coordinate axes. 3D reconstruction (red) of the nuclear surface was rendered using To-Pro-3 counterstaining. The surface was partly cut to look inside, above the level of the yellow cutting line marked in planes XZ and YZ. (b) One optical section was selected from the middle of a series of equidistant images to display structural details of a macronucleus (M) and four micronuclei (m) stained with To-Pro-3. The nucleoplasmic connection between the ovoid distal parts of the macronucleus is not visible because it makes a turn, out of the single optical section. (Inset b1) Image taken from another mid optical section; magnification 2.5x. Red arrowhead indicates a central delimitated zone of stained chromatin within an unstained spherical putative nucleolus. (c) Stylonychia lemnae DNA on an agarose gel. Left, DNA size marker. Middle, macronuclear gene-sized DNA molecules of 0.4-20 Kbp. Arrow marks ribosomal DNA. Right, micronuclear DNA.