A) Ca2+ oscillation profiles following the injection of sperm from normal fertile humans (top panel) and infertile patients who had previously failed or exhibited low fertilisation rates following ICSI (bottom panel). Arrows denote time of sperm injection, and n indicates the number of mouse oocytes exhibiting the corresponding Ca2+ oscillation profile. B) Reduced PLCζ immunostaining (red) in sperm from infertile ICSI failed patients exhibiting abnormal morphology (in this case globozoospermia; acrosome-less, round-headed sperm) (i), and normal morphology (ii). Fluorescein isothiocyanate-conjugated peanut agglutinin (FITC-PNA)-lectin staining (green) identifies the acrosome, and Hoescht-33342 staining (blue) identifies the nuclei. Arrow indicates reduced PLCζ immunolocalisation within the equatorial segment. Scale bars indicate 5 μm. Reproduced from Yoon et al. (2008) and Heytens et al. (2009) with permission.