Human Reproduction, Vol 12, 1062-1068, Copyright © 1997 by Oxford University Press
L Meng and DP Wolf
Intracytoplasmic sperm injection (ICSI) has increased the potential of the
assisted reproductive technologies to propagate mammalian species and has
provided an opportunity for research into cell cycle control and the
mechanisms involved in sperm-induced oocyte activation. We have
investigated the efficacy of ICSI in the rhesus monkey, the mechanism of
fertilization following sperm injection and the cytoskeletal rearrangement
that occurs upon oocyte activation. These studies were conducted on mature,
and to a lesser extent, immature oocytes. Ejaculated spermatozoa, washed,
capacitated and activated before immobilization, were injected into oocytes
using conventional ICSI methodology. Sperm injection into mature oocytes
induced oocyte activation (19/22; 86%) and pronuclear formation. In
contrast, sham- injected oocytes did not activate readily (2/16; 13%). To
localize oocyte activation factor(s), spermatozoa were separated
mechanically into heads and tails which were then injected individually
into mature oocytes. Activation occurred in 87% (20/23) of oocytes
receiving heads. After tail injection, a single microtubule aster was
nucleated and one pronucleus (PN) was seen in four of 21 oocytes.
Intracytoplasmic injection of sperm extract (SE) resulted in oocyte
activation at a significantly higher rate than occurred following sham
injection (76 versus 13%). Sperm-induced oocyte activation was also
evaluated in immature metaphase (MI) oocytes; activation occurred in 46%
(12/26) of cases; however, only 8% of the activated oocytes exhibited 2 PN.
Finally, beta-tubulin localization in untreated and taxol-treated oocytes
was established as a marker for cytoplasmic changes associated with oocyte
activation. These results are consistent with the hypothesis that
spermatozoa contain an oocyte activating factor(s) which is primarily
localized in the sperm head. Moreover, an activation response is limited to
mature oocytes and is accompanied by cytoskeletal changes analogous to
those seen following conventional fertilization.
ARTICLES
Sperm-induced oocyte activation in the rhesus monkey: nuclear and cytoplasmic changes following intracytoplasmic sperm injection
Oregon Regional Primate Research Center, Beaverton, USA.
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