after the hamster oocytes have been scored for sperm penetration by observing for the presence of swollen sperm heads , they are incubated in serum followed by either a 20-minute treatment with rhodamine-conjugated protein a ( which binds to most subclasses of iga , igg , and igm ) or a 2-hour incubation in guinea pig serum ( complement ) .
C0229671
serum
C0009498
complement