| dc.description.abstract |
There is debate as to whether the acrosome reaction is necessary for spermincorporation after intra-cytoplasmic sperm injection (ICSI). Ultrastructuralevidence is presented to show that the acrosome reaction could occur in theooplasm before sperm incorporation in mature human oocytes or the acrosomecould be discarded intact before sperm incorporation in immature oocytes,matured in vitro. Both germinal vesicle and growingfollicular oocytes showed sperm chromatin decondensation, with discardedacrosomes close to the sites of incorporation, and were able to form malepronuclei. This is probably the first report of microfertilization of agrowing oocyte with a reticulate nucleolus by ICSI. The acrosome reaction,when it occurs, is preceded by acrosome swelling and is followed byvesiculation of surface membranes exposing the inner acrosome membrane, asobserved on the surface of the zona during IVF or in the perivitelline spaceafter subzonal sperm injection. These sperm were probably capacitated at thetime of ICSI. There was subtle evidence of leaching of the acrosomal matrixfrom intact discarded acrosomes and from partially depleted acrosomes attachedto decondensing spermheads. These sperm were probably not fully capacitated atthe time of ICSI. It is concluded that both the acrosome reaction and acrosomedeletion are possible prerequisites to sperm incorporation after ICSI. |
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