ISSN:
1432-0878
Keywords:
Annulate lamellae
;
Freeze fracture
;
Oocyte
;
Pores
;
Zebrafish
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary The zebrafish oocyte contains prominent stacks of annulate lamellae (AL) located primarily in a subcortical position of the ooplasm. Many lamellae comprising a stack eventually exhibit continuity with the rough-surfaced endoplasmic reticulum which is present in abundance in larger oocytes. Pore structure of both AL and nuclear envelope (NE) was studied and compared by use of freeze-fracture electron microscopy. In freeze-fracture replicas, the NE and AL pores were easily distinguished, and a variety of fracture planes with respect to the stacked AL were generated. The pore diameter of NE and AL is similar (∼100nm). The number of nuclear pores varied from an average of ∼40 pores/μm2 in early stage oocytes to nearly double this number in later stage oocytes. For AL, the center-to-center spacing (∼120–130 nm) and the number of pores per square micrometer (∼56–67) did not change markedly regardless of oocyte developmental stage examined. Hexagonal packing of AL pores is a common feature. The AL pores have an angular margin with octagonal symmetry suggested in some cases. The AL pore interior contains fibrillar and particulate components and, depending upon the fracture plane, may appear to be filled with a “plug” of material. Both P- and E-membrane fracture faces of AL have a relative scarcity of intramembranous particles. The non-porous membranes that extend from the AL, however, have a higher concentration of intramembranous particles.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00222338
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