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Procedure
1a) To
inhibit the fast block to polyspermy, resuspend eggs in
ASW
or in nicotine (Sigma
Chemical Company) at 0.25
mM, 0.5 mM and 1 mM, (dilute 1.25 ul, 2.5 ul and 5 ul of
a
40% solution of nicotine
free base in 10 ml ASW and use immediately). Fertilize
eggs
with diluted sperm as
described in the basic
protocol. Be sure to allow
sperm to activate
for at least 5 minutes
before adding to eggs.
1b) To
inhibit the slow block to polyspermy, resuspend eggs in ASW
or in soybean trypsin
inhibitor (SBTI, Sigma
Chemical Company,) at 0.4 mg/ml (1/10 volume of 4 mg/ml
stock).
Fertilize eggs with diluted
sperm as described in the basic protocol. Be sure to
allow
sperm to activate for at
least 5 minutes before adding to eggs.
2.
Examine eggs after 10 minutes to score for the presence (or
absence) of the fertilization
envelope and periodically to
observe the events associated with the first cleavage
division.
References
Gilbert,
S.F., (2000), Developmental Biology, Sinauer
Associates, Sunderland, MA
Just, E.E., (1919), The fertilization reaction in
Echinarachinus parma, Biol. Bull., 36:1-10.
Jaffe, L.A., (1980),
Electrical polyspermy block in sea urchins: nicotine and low
sodium
experiments, Develop. Growth
and Differ., 22:503-507.
Vacquier, V.D., Tegner, M.J.,
and Epel, D., (1973), Protease release from sea urchin eggs
at
fertilization alters the
vitelline layer and aids in preventing polyspermy. Exp. Cell
Res. ,
80:111-119.
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