Fig. 1. Nuclear membranes and lamina detach from bulk nucleoplasm during swelling. (A) Two unswollen nuclei were imaged at 4x magnification by bright-field microscopy and stained with YO-PRO to visualize DNA/RNA in the nucleoplasm. The nucleoplasm in the unswollen nuclei completely fills the nucleus. Fluorescent antibodies against B-type lamins show the peripheral lamina of a different nucleus. (B) A single swollen nucleus was imaged by bright-field and fluorescence microscopy to reveal DNA/RNA in the nucleoplasm with YO-PRO (green) and lamins (red). The nuclear envelope, with attached lamina, detaches from the constant-size nucleoplasm during swelling. (C) A swollen nucleus imaged with bright-field optics (left) and with fluorescent phalloidin to visualize F-actin (right). Extensive actin polymerization as seen here is an artifact of nuclear isolation. Scale bars: 250 µm.