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Mol Biol Cell January 1, 2005; 16 (1): 202-11.
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Cajal bodies, nucleoli, and speckles in the Xenopus oocyte nucleus have a low-density, sponge-like structure.

Handwerger KE , Cordero JA , Gall JG .

Nuclear organelles, unlike many cytoplasmic organelles, lack investing membranes and are thus in direct contact with the surrounding nucleoplasm. Because the properties of the nucleoplasm and nuclear organelles influence the exchange of molecules from one compartment to another, it is important to understand their physical structure. We studied the density of the nucleoplasm and the density and permeability of nucleoli, Cajal bodies (CBs), and speckles in the Xenopus oocyte nucleus or germinal vesicle (GV). Refractive indices were measured by interferometry within intact GVs isolated in oil. The refractive indices were used to estimate protein concentrations for nucleoplasm (0.106 g/cm3), CBs (0.136 g/cm3), speckles (0.162 g/cm3), and the dense fibrillar region of nucleoli (0.215 g/cm3). We determined similar protein concentrations for nuclear organelles isolated in aqueous media, where they are no longer surrounded by nucleoplasm. To examine the permeability of nuclear organelles, we injected fluorescent dextrans of various molecular masses (3-2000 kDa) into the cytoplasm or directly into the GV and measured the extent to which they penetrated the organelles. Together, the interferometry and dextran penetration data show that organelles in the Xenopus GV have a low-density, sponge-like structure that provides access to macromolecules from the nucleoplasm.

PubMed ID: 15509651
PMC ID: PMC539164
Article link: Mol Biol Cell

References [+] :
BATTIN, The osmotic properties of nuclei isolated from amphibian oocytes. 1959, Pubmed