Delayed sperm incorporation into parthenogenetic mouse eggs: Sperm nucleus transformation and development of resulting embryos

Chromatin and microtubule organisation in maturing and pre-activated porcine oocytes following intracytoplasmic sperm injection

“…In the mouse, spermatozoa penetrating the oocyte 3 h or more after activation form abnormal chromatin and fail to form a normal pronucleus (Maleszewski et al, 1999). Similarly, we observed that much less sperm…”

Meiotic maternal chromosomes introduced to the late mouse zygote are recruited to later embryonic divisions

“…Transformation of both female and male chromatin during this phase may be crucial for proper regulation of parental imprinting. Previous experiments have demonstrated that male chromatin is able to form a functional pronucleus in the second rather than the first cell cycle, however, is unable to support development to term (Plusa et al, 1997;Maleszewski et al, 1999). No study has previously been performed to investigate whether female chromatin in the form of a metaphase plate of the second meiotic division can form a The differences between the groups (anaphase vs. anaphase/ telophase, for full sized and underdeveloped nuclei), as calculated using w 2 test, are statistically significant at P < 0.001 (1 degree of freedom).…”

Effects of Activation Timing on the Fertilization Rate and Early Embryo Development in Porcine ROSI Procedure

“…In addition, it was also reported that round spermatids injected 1 h after oocyte activation failed to undergo NEBD and their nuclei remained small (10,11). Finally, the increasing time interval between activation and insemination was known to dramatically decrease the ability of oocytes to promote the transformation of sperm nucleus into a fully formed male pronucleus in mouse (24) and pig (25), which may offer an additional explanation for the poor result in the preactivation group.…”