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From the Department of Obstetrics and Gynecology, Tohoku University School of Medicine, Sendai, Japan.
| Correspondence to: Dr Yukihiro Terada, Associate Professor, Department of Obstetrics and Gynecology, Tohoku University School of Medicine, Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8574, Japan (e-mail: terada{at}mail.tains.tohoku.ac.jp). |
During mammalian fertilization, a centrosome is introduced by the sperm
during the first cell cycle to organize a radial array of microtubules known
as the sperm aster. In nature, multiple human sperm centrosomes may exist in
the same egg cytoplasm during polyspermy. However, critical information
concerning individual sperm centrosomal function with regards to the latter
case remains unknown. We subsequently examined the sperm aster formation after
injection of multiple human sperm into a bovine egg. When 2 fertile human
sperm were simultaneously microinjected into different regions of the same
bovine egg cytoplasm, no difference in sperm aster formation rate was observed
compared to cases in which a single sperm was injected. Two human sperm were
also microinjected into bovine eggs 30-, 60- and 120-minute intervals apart
from one another, and no difference in sperm aster formation rates were
observed. Among eggs in which 1 sperm aster was organized, there was no
observable bias towards the first or second injected sperm. These findings
indicated that when multiple human sperm are present in a single egg
cytoplasm, each centrosome can function independently from the other. This
fact suggests the possibility of transplanting a normal sperm centrosome into
an egg with a sperm known to have centrosomal dysfunction.
Key words: Fertilization, sperm aster, polyspermy, microtubules
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