Image analysis of the acetic acid-alcohol fixed metaphase chromosome

Electron micrographs of acetic acid-alcohol fixed, unstained human metaphase chromosomes have been analyzed with an image system. Electron micrographs were first digitized from over a million picture elements into a range of 64 gray levels which correspond to mass distribution. The obtained numerical data were then processed by programs which increased contrast and permitted enhancement and expansion of the original image. Despite the disruptive nature of such preparations, analysis of their TEM images reveals structural features previously reported from other preparative methods as well as morphological properties previously reported in metaphase chromosomes which required special pretreatments and staining for demonstration. Familial features included low density centromeres and secondary constrictions, higher density telomeres and paracentromeric regions, and G-band-like differential densities along chromatids. In addition, structural components were observed in a size range 25-56 nm. These masses appeared to have linear and circular forms oriented in perpendicular, diagonal and longitudinal arrays. They appeared in a nonrandom fashion and can be interpreted as demonstrating a relatively ordered chromosome.