Biology Reference
In-Depth Information
Fig. 2.5 a, a
0
Spontaneous post-ICSI fragmented zygotes after failure of syngamy that followed
microinjection of spermatozoa with neck anomalies. In A two pronuclei are clearly seen (arrows).
b heterologous ICSI. Normal sperm aster formation (tubulin green fluorescence) after injection of
a normal human spermatozoon into a bovine oocyte. b
0
When a spermatozoon with neck
anomalies is microinjected the sperm aster fails to form. The sperm flagellum (tubulin green
fluorescence) is still associated with the male pronucleus. a, a
0
, original magnification X400; b,
b
0
, bars represent 25 lm (These figures were originally produced by Chemes et al. (
1999
) and
Rawe et al. (
2002
) and are reproduced, modified from the original, with permission from the
publishers)
What impaired mechanisms can account for centrosomal dysfunction? The proxi-
mal centriole must disengage from the connecting piece to be able to reconstitute the
zygote centrosome. Long et al. (
1997
) characterized a phosphorylated protein complex
from sperm ODF and connecting pieces that may be involved in the regulation of sperm
centrosomal activity after connecting piece disassembly, and Pinto Correia et al.
(
1994
) reported that dephosphorylation of sperm connecting piece antigens is required
for initiation of aster formation in rabbit oocytes. Centriole release after fertilization
