The structural aspects of sperm penetration in the rat egg were investigated by electron microscopy. Eggs were recovered at intervals between 8 and 10:30 A.M. from females which had mated during the previous night. The oviducts were flushed with hyaluronidase and the eggs transferred into a 2 per cent osmium tetroxide solution, buffered at pH 7.8. After fixation, the eggs were mounted individually in agar, dehydrated in ethyl alcohol, and embedded in butyl-methyl methacrylate (3:1). The sperm penetrating the egg is covered by a plasma membrane which is present only on the side facing toward the zona pellucida; no membrane is visible on the side facing toward the vitellus. The sperm plasma membrane becomes continuous with the egg plasma membrane and forms a deep fold around the entering sperm. Cross-sections through the sperm midpiece in the perivitelline space show an intact plasma membrane. At the place of entrance, the plasma membrane of the sperm appears to fuse with the egg plasma membrane. After the sperm has penetrated the vitellus, it has no plasma membrane at all. The nuclear membrane is also absent. These observations suggest a new hypothesis for sperm penetration. After the sperm has come to lie on the plasma membrane of the egg, the egg and sperm plasma membranes rupture and then fuse with one another to form a continuous cell membrane over the egg and the outer surface of the sperm. As a result the sperm comes to lie inside the vitellus, leaving its own plasma membrane incorporated into the egg membrane at the surface of the egg.
Article|
June 01 1961
OBSERVATIONS ON SPERM PENETRATION IN THE RAT
Daniel G. Szollosi,
Daniel G. Szollosi
From the Department of Zoology, University of Wisconsin, Madison
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Hans Ris
Hans Ris
From the Department of Zoology, University of Wisconsin, Madison
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Daniel G. Szollosi
From the Department of Zoology, University of Wisconsin, Madison
Hans Ris
From the Department of Zoology, University of Wisconsin, Madison
Received:
February 01 1961
Copyright, 1961, by The Rockefeller Institute Press
1961
J Biophys and Biochem Cytol (1961) 10 (2): 275–283.
Article history
Received:
February 01 1961
Citation
Daniel G. Szollosi, Hans Ris; OBSERVATIONS ON SPERM PENETRATION IN THE RAT . J Biophys and Biochem Cytol 1 June 1961; 10 (2): 275–283. doi: https://doi.org/10.1083/jcb.10.2.275
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