Sb. Shah et al., STRUCTURAL-CHANGES IN OOCYTE NUCLEOLI OF XENOPUS-LAEVIS DURING OOGENESIS AND MEIOTIC MATURATION, Chromosoma, 105(2), 1996, pp. 111-121
Immunoelectron microscopy with anti-nucleolin defined substructures wi
thin the multiple nucleoli of biosynthetically active stage II-III ooc
ytes and within the nucleoli of relatively quiescent stage VI oocytes
of Xenopus laevis. Dense fibrillar components (DFCs) of nucleoli from
stage II-III oocytes consisted of nucleolonemas that radiated from a c
ontinuous DFC sheath surrounding fibrillar centers (FCs). Discernible
granular regions (GRs) were absent in these same nucleoli. Conversely,
stage VI oocyte nucleoli displayed compacted DFCS and prominent GRs.
Immunofluroescence microscopy then tracked fibrillarin, nucleolin, and
condensed DNA through oogenesis and into progesterone-induced meiotic
maturation and nuclear breakdown. In stage II-III oocyte nucleoli, fi
brillarin was enriched near the FC-DFC boundaries, while nucleolin was
distributed throughout these same DFCs. Both proteins were enriched w
ithin the compacted DFCs of stage VI oocyte nucleoli. Staining with (D
API) 4',6-diamidino-2-phenyl-indole showed condensed DNA within nucleo
lar FCs of both stage II-III and stage VI oocyte. Upon nuclear breakdo
wn, we found fibrillarin and nucleolin in small particles and in the s
urrounding cytoplasm. Although we saw no trace of fibrillarin or nucle
olin in nuclear remnants prepared just minutes later, DAPI-stained par
ticles remained within these preparations, thus suggesting that FCs we
re at least slow to disassemble.