Summary
A reexamination of nuclear extrusion in preimplantation rabbit embryos led to new observations which were used to reconstruct details of this process. Small portions of both membranes of the nuclear envelope protrude toward the cytoplasm after cell division. The extrusions formed by the inner membrane are spherical or pear-shaped and their basal portion is constricted. The outer membrane of the nuclear envelope either follows the contours of the inner membrane or it forms large dilatations portions of which pinch off into the cytoplasm. A density appears at the constricted basal portion of the extrusions and is thought to close off the extrusion from the nucleoplasm. When the extrusions of the inner membrane separate from the nuclear envelope they may or may not be enveloped by the outer membrane. The fate of the extrusions in the cytoplasm is uncertain.
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Supported by NICHHD Postdoctoral Fellowship 1 FO2 HD-32, 621-01 A1. The author wishes to thank Dr. W. P. Norman for reviewing the manuscript. Many thanks are due to Mr. Frank Denys for the preparation of the electron micrographs for publication.
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Gulyas, B.J. Nuclear extrusion in rabbit embryos. Z. Zellforsch. 120, 151–159 (1971). https://doi.org/10.1007/BF00335533
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DOI: https://doi.org/10.1007/BF00335533