3D IMAGE PROCESSING OF WHOLE MOUNTED CHROMOSOMES BY COMPUTER ANIMATION FROM TILTED SERIAL ELECTRON MICROSCOPIC PROJECTIONS. Peter Engelhardt Dept. of Virology, University of Helsinki, Haartmaninkatu 3, 00290 Helsinki, Finland. (Peter.Engelhardt@Helsinki.Fi)

Image, a public domain program (available from National Institute of Health, USA) for the Macintosh computers was used to study the higher order chromosome structure of eukaryotic cells. In our preparations of metaphase chromosomes from Chinese hamster ovary cells the chromosomal coilings were visible and could be observed from different turnings from 0 to + and - 60 degree as cork-screw-like structures composed of linear arrays of chromomeres. Centers of the chromomeres were visualized as perforations or small rings (diameter 50-100 nm) around which the chromatin fibers were condensed. The animations were best visualized as serial stereo pairs that gave better resolution and a 3-dimensional appearance. Similar animation could be done for whole mounted critical-point-dried polytene chromosomes of Drosophila. In these the bands could be visualized as discs composed of masses of similar looking chromomeres. These structures could further be compared to those found in interphase chromatin of whole mounted somatic and meiotic nuclei as they progressed to prophase, specially as detachable units from the nuclear envelope. The 3D image processing visualization methods support our earlier observations from sectioned and spread material and our loop-and-rosette model of chromatin folding. In this model the center of the rosette is the cyclomere, the detachable nucleoplasmic part of the nuclear pore complex and the loop origins are the cyclosomes, the nucleoplasmic subunits of the pore complexes, which forms the scaffold around which the nucleosome fibers are folded to higher order structures.


Presented in: 
3D Imaging Sciences in Microscopy: Joint Conference: 4th International Conference on Confocal Microscopy and 5th International Conference on 3D Image Processing in Microscopy, 
March 9- 11, 1992 Amsterdam (Book of Abstracts).