title: Modeling the 3-D RNA distribution in the Balbiani ring granule.
abstract: Mature Balbiani Ring (BR) granules in situ were stained with the nucleic acid specific stain, osmium ammine-B, recorded by electron spectroscopic imaging and reconstructed by electron microscope tomography to examine the three-dimensional (3-D) distribution of BR heterogeneous nuclear RNA (hnRNA). The BR2 granules contain ca. 37 kb of mRNA. Reconstructed BR granules were selected to emphasize one of the prevalent conformations seen in the sectioned salivary glands, the en face or "pin-wheel" conformation. A variety of image processing and volume-rendering operations were applied to the set of reconstructed BR granules. Some of the conclusions of this study are the following: (1) RNA distribution is not uniform throughout the granule; (2) RNA is condensed into about ten particles per granule, which all appear to possess approximately the same RNA stain density; (3) heterogeneity exists in the positions and sizes of particles within the various BR granules. These data argue for the folding of a beaded ribbon, consisting of connected particulate condensations of BR mRNA, possessing considerable 3-D flexibility, even in the packaged state. A comparison of this beaded-ribbon model and a prior folded hnRNP fiber model is also presented.
authors: University of Tennessee-Oak Ridge Graduate School of Biomedical Sciences 37831-8077.
authors: A L
authors: AL
authors: Olins
authors: D E
authors: DE
authors: Olins
authors: V
authors: V
authors: Olman
authors: H A
authors: HA
authors: Levy
authors: D P
authors: DP
authors: Bazett-Jones
mesh_terms: D000818:Animals; D002683:Chironomidae; D002875:Chromosomes / Q000737:chemistry / Q000648:ultrastructure*; D004396:Coloring Agents; D003198:Computer Simulation; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron / Q000379:methods; D008958:Models, Molecular; D017892:Osmium Compounds; D000644:Quaternary Ammonium Compounds; D012332:RNA, Heterogeneous Nuclear / Q000032:analysis / Q000648:ultrastructure*; D012469:Salivary Glands / Q000648:ultrastructure; D014054:Tomography / Q000379:methods
chemical_list: D004396:Coloring Agents; D017892:Osmium Compounds; D000644:Quaternary Ammonium Compounds; D012332:RNA, Heterogeneous Nuclear; C058639:osmium ammine B