Sperm penetration into immature mouse oocytes and nuclear changes during maturation: an EM study

The ultrastructure of oocyte and sperm nuclei was studied in mouse ovarian oocytes inseminated in vitro and cultured for 1 1 2 and 3 h in a medium containing dbcAMP or lacking the maturation inhibitor. In oocytes blocked at the germinal vesicle (GV) stage, certains maturation-linked changes were not...

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Bibliographic Details
Published in:Biology of the cell 1990, Vol.69 (1), p.53-64
Main Authors: Szöllösi, Daniel, Szöllösi, Maria S, Czolowska, Renata, Tarkowski, Andrzej K
Format: Article
Language:English
Subjects:
Animals
Bucladesine - pharmacology
Female
Fertilization in Vitro
germinal vesicle
Life Sciences
Male
Mice
nuclear envelope
Nuclear Envelope - metabolism
oocyte maturation
Oocytes - drug effects
Oocytes - ultrastructure
ovarian oocyte
Sperm Head - ultrastructure
sperm penetration
Sperm-Ovum Interactions - physiology
Spermatozoa - ultrastructure
Zygote - ultrastructure
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Summary:The ultrastructure of oocyte and sperm nuclei was studied in mouse ovarian oocytes inseminated in vitro and cultured for 1 1 2 and 3 h in a medium containing dbcAMP or lacking the maturation inhibitor. In oocytes blocked at the germinal vesicle (GV) stage, certains maturation-linked changes were noted. Sperm apposition and sperm-oocyte fusion were similar to that during fertilization of ovulated oocytes. The sperm nucleus and its nuclear envelope remained intact after penetrating into the ovarian oocyte. One and a half h after removal of the drug (time 0 of maturation) the germinal vesicle (GV) and sperm nucleus remained intact. In oocytes maturing for 3 h, the nuclear envelopes of the GV and sperm nucleus had fragmented. The NE of the oocyte formed quadruple membranes while the NE of the sperm remained as flat vesicles. Oocyte chromatin condensed to form chromosomes, whereas at the same time the sperm chromatin was in the process of decondensation and was surrouded by fragments of the sperm NE. The sperm chromatin, composed of DNA complexed with protamines, consisted of thin fibrils; the individual fibrils measured 3.8 nm in diameter. Near the penetrated spermatozoa only occasional Mts were detected which were not related to the proximal centriole which was recognizable in the neck-piece of the flagellum. Thus in mouse oocytes the introduced sperm centriole is not capable of behaving as a centrosome and organizing microtubules in the form of an aster.
ISSN:0248-4900
1768-322X
DOI:10.1016/0248-4900(90)90328-Z