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Mouse oocytes and parthenogenetic eggs lose the ability to be penetrated by spermatozoa after fusion with zygotes

Published online by Cambridge University Press:  01 November 1998

Anna Krukowska
Affiliation:
Department of Embryology, Institute of Zoology, University of Warsaw, Poland
Ewa Wielkopolska
Affiliation:
Department of Embryology, Institute of Zoology, University of Warsaw, Poland Present address: Nencki Institute of Experimental Biology, Department of Neurophysiology, Pasteura 3, Warsaw, Poland.
Renata Czolłwska
Affiliation:
Department of Embryology, Institute of Zoology, University of Warsaw, Poland
M. Maleszewski
Affiliation:
Department of Embryology, Institute of Zoology, University of Warsaw, Poland
A.K. Tarkowski
Affiliation:
Department of Embryology, Institute of Zoology, University of Warsaw, Poland

Abstract

Fertilised mouse eggs develop the oolemma block to sperm penetration within 1 h. This block makes zona-free eggs at the pronuclear stage (zygotes) fully resistant to sperm penetration. In this study we investigated whether this block can spread – as a result of cell fusion – to the oolemma of eggs that are competent to be penetrated by spermatozoa. Preovulatory (GV) oocytes, ovulated oocytes in metaphase II (MII) and 1-cell parthenotes were fused with zygotes and the hybrid cells inseminated at various intervals after fusion. Sperm penetration was assessed on the basis of the presence of Giemsa-positive sperm heads in the air-dried preparations. The oolemma block to sperm penetration develops in all types of hybrids although at different speeds: it develops fast (2–3 h) in oolemma derived from MII oocytes and artificially activated eggs, and slowly in oolemma derived from GV oocytes. In the GV oocyte–zygote hybrids the time of formation of the block varied: while 50% of cells lost the ability to fuse with sperm by 2 h after fusion, in the remaining cells the block must have developed some time between 5 and 18 h after fusion. How these sperm-induced modifications of the oolemma of fertilised egg spread in the hybrid cell and render the ‘virgin’ part of oolemma resistant to sperm penetration remains unknown.

Type
Research Article
Copyright
1998 Cambridge University Press

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