Accessing nuclear structure for field emission, in lens, scanning electronmicroscopy (FEISEM)

Scanning electron microscopy (SEM) has had a shorter time course in biology than conventional transmission electron microscopy (TEM) but has neverthel ess produced a wealth of images that have significantly complemented our pe rception of biological structure and function from TEM information. By its nature, SEM is a surface imaging technology, and its impact at the subcellu lar level has been restricted by the considerably reduced resolution in con ventional SEM in comparison to TEM. This restriction has been removed by th e recent advent of high-brightness sources used in lensfield emission instr uments (FEISEM) which have produced resolution of around 1 nanometre, which is not usually a limiting figure for biological material. This communication reviews our findings in the use of FEISEM in the imaging of nuclear surfaces, then associated structures, such as nuclear pore comp lexes, and the relationships of these structures with cytoplasmic and nucle oplasmic elements. High resolution SEM allows the structurally orientated c ell biologist to visualise, directly and in three dimensions, subcellular s tructure and its modulation with a view to understanding its functional sig nificance. Clearly, intracellular surfaces require separation from surround ing structural elements in vivo to allow surface imaging, and we review a c ombination of biochemical and mechanical isolation methods for nuclear surf aces.