. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FERTILIZATION PROCESSES IN OYSTER EGGS 207. Figure 10. (a, b) Formation of the male pronuclear envelope, (a) Following polar body formation, cisternae (C) surround the dispersed sperm chromatin (D) and (b) fuse to form a nuclear envelope (arrow). Scale bar = 1 ^m. This structure did not appear to diminish appreciably in size throughout the period of fertilization (up to 1 h). In mitotic cells, loss of the nucleolus is due to the cessation of rRNA synthesis, coupled with the continued processing of ribosomal precursors (Anast
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FERTILIZATION PROCESSES IN OYSTER EGGS 207. Figure 10. (a, b) Formation of the male pronuclear envelope, (a) Following polar body formation, cisternae (C) surround the dispersed sperm chromatin (D) and (b) fuse to form a nuclear envelope (arrow). Scale bar = 1 ^m. This structure did not appear to diminish appreciably in size throughout the period of fertilization (up to 1 h). In mitotic cells, loss of the nucleolus is due to the cessation of rRNA synthesis, coupled with the continued processing of ribosomal precursors (Anastassova-Kristeva, 1977; Hadjiolov, 1985). Failure of these events presumably would lead to the retention of a nucleolus as seen here. Major events in the breakdown of the germinal vesicle are the loss of nuclear pore complexes and the vesiculation of the nuclear envelope into cisternae that are structurally reminiscent of elements of the endoplasmic reticulum. Concomitant with the breakdown of the nuclear envelope is the formation of networks and aggregations of endo- plasmic reticulum. Although the surface area of the nu- clear envelope measures about 2900 nm2, it is doubtful that all membranous elements comprising the networks and aggregations that appear with germinal vesicle break- down are, in fact, derived from the nuclear envelope. This impression is based on preliminary observations (F. J. Longo, pers. obs.) indicating that the number and size of endoplasmic reticulum aggregation's comprise a greater area than can be accommodated by the nuclear envelope of the germinal vesicle. Hence, we suggest that concom- itant with germinal vesicle breakdown, cisternae of en- doplasmic reticulum throughout the egg are organized into dense aggregations and networks. Cisternae derived from the breakdown of the nuclear envelope may be a part of these membranous arrays. Alterations in the endoplasmic reticulum seen in C. gigas eggs/zygotes are similar to those described for starfish oocy
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
