Sperm selection by a climbing-over-a-wall IVF method reduces the incidence of polyspermic
penetration of porcine oocytes.
The most immediate question is whether researchers should be permitted to split and culture blastomeres from normal embryos in order to replicate the results obtained at George Washington with polyspermic
However, the proportions of polyspermic
oocytes were not significantly different among the treatments.
Because researchers cannot distinguish between sperm with and without acrosome caps, they must inject more than one sperm into an egg in order to get a decent shot at fertilization -- a practice that sometimes produces useless, polyspermic
eggs, says Lippi.
As first identified in sea urchins (Jaffe, 1976), a membrane depolarization based on external sodium is believed to generate a fast polyspermic
block in Crassostrea gigas (Togo and Morisawa, 1999) and Mytilus edulis (Togo et al.
Table 2 Developmental profiles of wrinkled egg formation in normal fertilized eggs and polyspermic
eggs Percentage of egg shape under each sperm concentration (sperm/[mu]l) Time after Developmental 17 32 65 fertilization (min) stage (shape) 0 1 cell (S) 100 100 100 (n = 35) (n = 45) (n = 33) 30 1 cell (S) 11.
This study was examined whether the variation of stress related HSP70 gene was associated with nuclear morphological change during in vitro maturation with or without freezing of immature oocytes on the pattern of the enlarged sperm head and polyspermic
invasion in pigs.
At 12 h after IVF, oocytes were fixed in 2% formaldehyde for 40 min to examine sperm penetration, polyspermic
oocytes and pronucleus formations.
eggs exhibited multiple currents associated with the polynumery sperm.
In fertilization experiments with polyspermic
eggs of D.
Oocytes were considered to be polyspermic
when the first cleavage was abnormal.
In contrast, artificially activated sea urchin eggs tend not to divide, and polyspermic
eggs have very characteristic disruptions in their cleavage patterns (e.