Zafer Atayurt: Just 10 Seconds Can Make All the Difference in Fertilization
Zafer Atayurt, IVF Laboratory Director at Ventus IVF Center, shared a post on LinkedIn about a paper by Yasuyuki Mio et al. published in the Journal of Assisted Reproduction and Genetics:
“Just 10 seconds can make all the difference.
While reviewing the literature on fertilization abnormalities, I came across a fascinating observation that I wanted to share.
This remarkable time-lapse recording below captures a rarely observed moment during conventional IVF in a human oocyte.
A leading sperm penetrates the zona pellucida, crosses the perivitelline space, and attaches to the oocyte membrane. Within 10 seconds, a second sperm already advancing through the zona pellucida stops progressing, even though its tail remains actively motile.
The authors considered this phenomenon distinct from the classical zona reaction, a slower process mediated by cortical granule exocytosis.
An oocyte membrane block could not explain it either, since the second sperm was arrested within the zona pellucida before reaching the oocyte membrane.
They therefore proposed the possible existence of a fast zona block to polyspermy.
This phenomenon was observed in only three oocytes, and its underlying mechanism remains unknown.
Nevertheless, the recordings offer a striking glimpse into how rapidly and precisely the human oocyte may respond to fertilization.”
Title: Possible mechanism of polyspermy block in human oocytes observed by time-lapse cinematography
Authors: Yasuyuki Mio, Kyoko Iwata, Keitaro Yumoto, Yoshiteru Kai, Haruka C. Sargant, Chizuru Mizoguchi, Minako Ueda, Yuka Tsuchie, Akifumi Imajo, Yumiko Iba, Kyoko Nishikori
You can read the Full Article in the Journal of Assisted Reproduction and Genetics․

Proceed to the video attached to the post.
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