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Spermatozoon Acrosome-reacted bull sperm on the surface of zona pellucida-free bovine oocytes. (A) Microvilli can be seen uniformly distributed over the oocyte surface. After a 10-min exposure to sperm, microvilli from the oocyte can be seen making contact with the sperm over the anterior head in the vesiculated outer acrosomal membrane and equatorial segment membrane areas. Several spherical structures are apparent around the sperm head, most likely the products of cortical granule release. (B,C) Microvilli on the oolemma surface are in contact with the sperm head after 20 min of sperm exposure. It is at this time-point that the earliest images of membrane fusion can be seen in the LVSEM. This fusion event appears to begin primarily over the area of the sperm head corresponding to the equatorial segment. (D) At 30 min after sperm addition, the area over the equatorial segment appears to be completely fused with the oolemma membrane, yet the oocyte microvilli are seen interacting with the acrosomal and postequatorial domains. A portion of the sperm membrane is still exposed to the media. Images originally published in: Tengowski, MW (2004) Microscopic techniques for studying sperm-oocyte interaction during fertilization and early embryonic development. Methods in Molecular Biology (Clifton, N.J.), 253, 165-99. |
