title: Donut-shaped "miniparticles" in nuclei of human and rat cells.
abstract: Donut-shaped "miniparticles" were extracted from nuclei of various types of human and rat cells. Electron-microscopic investigation showed these particles were predominantly in sucrose density gradient fractions that had an approximate sedimentation coefficient of 21S. These particles were 113 +/- 8A in diameter and had an electron dense center of 29 +/- 6A. They appeared to be composed of 8 subunits. Quantitative analysis of the number of these particles by electron-micrographic field counting showed nuclei of tumor samples had a larger amount of the particles than the cytosol. However, normal cell cytosol had a larger number of particles than the nuclei. A group of proteins in the 25,000-33,000 molecular weight range was shown to be the main protein component by two dimensional gel electrophoresis.
mesh_terms: D000818:Animals; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000648:ultrastructure*; D002499:Centrifugation, Density Gradient; D005260:Female; D006801:Humans; D008099:Liver / Q000648:ultrastructure; D008223:Lymphoma / Q000648:ultrastructure; D008854:Microscopy, Electron; D010920:Placenta / Q000648:ultrastructure; D011247:Pregnancy; D051381:Rats