Assessment of cumulus mass dispersal and the efficiency of <i>in vitro</i> fertilization.

(A) Upper part: classification key used to assess the dispersion of cumulus cells surrounding eggs. If an egg was tightly packed with cumulus cells, it was classified into group 4. Eggs were classified into group 3 when they were clearly visible but were still associated with many layers of cumulus cells, albeit not as many as in group 4. In the eggs classified into group 2, between one and two layers of cumulus cells fully surrounding the cells were retained, albeit a few layers were present at some positions. Group 1 contained eggs with only a few attached cumulus cells. Lower part: the ability of WT and NWC-KO sperm to disperse cumulus cells at the indicated time periods. The set of bars located below a given image represents the percentage of a group. Data are presented as mean values with SD obtained from at least four independent experiments. In a single experiment, a pair of males of each genotype was used as sperm donors. (B) Ability of WT and NWC-KO sperm to fertilize cumulus-intact eggs. Data are presented as the results of five independent experiments. In a single experiment, a pair of males of each genotype was used as sperm donors.