Fig. 4.

The presence of an intact cumulus layer on oocytes increases the fertilizing ability of capacitated spermatozoa. Asterisks denote cumulus-free oocytes from transgenic females whose oocytes express red fluorescence. (A and B) Approximately 10–20 cumulus-free oocytes incubated with or without cumulus-enclosed oocytes (A) or with cumulus–oocyte complex conditioned medium (B) were inseminated at a final concentration of 2 × 10⁴ sperm/mL. The numbers of two-cell embryos per total oocytes examined was scored after 24 h. Shown are the percentages obtained from seven independent experiments. The total number of oocytes scored is indicated in parentheses.