ULTRASTRUCTURE OF GAMETES AFTER INTRACYTOPLASMIC SPERM INJECTION

The ultrastructure of 18 metaphase-II, oocytes after intracytoplasmic sperm injection (ICSI) was analysed from 30 min to 8 h following the m icroinjection, Three control metaphase-II oocytes were not injected. T he 21 oocytes were embedded individually and examined in serial pole-t o-pole sections. Seventeen oocytes had been matured in vitro from the germinal vesicle stage and showed ultrastructural alterations due to l ong-term culture, In microinjected oocytes, membrane-bound vacuoles an d oolemma inclusions were found at the injection site, The ICSI oocyte s showed evidence of plasma-membrane damage and increased oocyte excha nge processes with residual and multivesiculated bodies. Gamete membra ne fusion was not observed. Acrosome reaction was observed within the ooplasm 15 min after ICSI, Sperm elements were not incorporated into a ny oocyte vacuole, Onset of oocyte activation was associated with sper m chromatin decondensation, Cortical granules were released at 60 min and two pronuclei mere formed at 6 h after ICSI, The male and female p ronucleus formation was asynchronous, The findings suggest specific IC SI-related morphological features of early fertilization.