Atomic force microscopy of the cell nucleus

In mammals and plants, the cell nucleus is organized in dynamic macromolecu lar domains involved in DNA and RNA metabolism. These domains can be visual ized by light and electron microscopy and their composition analyzed by usi ng several cytochemical approaches. They are composed of chromatin or ribon ucleoprotein structures as interchromatin and perichromatin fibers and gran ules, coiled bodies, and nuclear bodies. In plants, DNA arrangement defines chromocentric and reticulated nuclei. We used atomic force microscopy to s tudy the in situ structure of the plant cell nucleus. Samples of the plants Lacandonia schismatica and Ginkgo biloba were prepared as for electron mic roscopy and unstained semithin sections were mounted on glass slides. For c omparison, we also examined entire normal rat kidney cells using the same a pproach, Samples were scanned with an atomic force microscope working in co ntact mode. Recognizable images of the nuclear envelope, pores, chromatin, and nucleolus were observed. Reticulated chromatin was observed in L. schis matica. Different textures in the nucleolus of G. biloba were also observed , suggesting the presence of nucleolar subcompartments. The observation of nuclear structure in situ with the atomic force microscope offers a new app roach for the analysis of this organelle at high resolution. (C) 2000 Acade mic Press.