THE EARLY DEVELOPMENT AND DNA CONTENT OF ACTIVATED HUMAN OOCYTES AND PARTHENOGENETIC HUMAN EMBRYOS

A total of 297 human oocytes that had failed to fertilize during in-vi tro fertilization (IVF) cycles were exposed to the calcium ionophore A 23187 to induce parthenogenetic activation. Of these oocytes, 192 (65% ) activated, the majority (63%) exhibiting a single pronucleus and ext ruding a second polar body. The appearance of two pronuclei (18%) was generally associated with a failure to extrude the second polar body. Oocytes obtained from patients who were greater than or equal to 35 ye ars had a significantly reduced activation rate (53%). The timing of d evelopmental events, such as extrusion of the second polar body, appea rance and disappearance of pronuclei and the first two cleavage divisi ons, is broadly similar to that seen in fertilized oocytes. However, t he developmental potential of human parthenogenetic embryos was reduce d, as the majority of those allowed to continue in culture arrested be tween the 2-cell and 8-cell stages. Measurements of cellular DNA conte nt using a computerized image analysis system showed that activated oo cytes with one pronucleus had a DNA content compatible with a haploid number of chromosomes, while those with two pronuclei were diploid. Th e ability of parthenogenetically activated oocytes to replicate their DNA was also demonstrated.