Fig. 59. High power TEM showing nuclear organization of a blastomere in a stage 2, 4-cell embryo in vitro 44 hours post-insemination (original magnification x33,380). The nucleus contains a dense, compact nucleolus and scattered clumps of heterochromatin but mainly euchromatin. The nuclear envelope is a two-layered membrane and is perforated by well-defined pores (small arrowheads). A dense, oval body is present in the perinuclear space and arises from the inner membrane where the outer membrane forms a bleb (large blue arrowhead).
M, mitochondrion; S, smooth endoplasmic reticulum.
(From: Trounson and Sathananthan, 1984. Reproduced with permission of Plenum Publishing Corporation.)
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