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Fig. 1. Peroxidase-mediated crosslinking in the sea urchin fertilization
envelope contributes to its permeability barrier. (A-D) Plots show
permeability of dextrans into the perivitelline space of zygotes whose embryos
were formed as normal (A), after egg dejellying (B), in calcium-free seawater
(C), and in 3-AT (D). Plots show the percentage of normalized fluorescence
(variable molecular mass Texas Red dextran fluorescence to control
3,000-dalton Cascade Blue dextran) within the perivitelline space versus the
media outside the zygote. At least seven individuals were measured for each
point plotted. Mean percentages and standard deviation are shown. Data from
normal formation conditions (A) are reproduced in greyscale in other plots
(B-D). Significant changes in permeability compared with normal zygotes
(P<10-10) are indicated (asterisks).
(E,F) Merged images of fertilization envelopes formed under
normal conditions for S. purpuratus (E) and L. variegatus
(F). Neutral Texas Red dextran fluorescence (3,000 to 70,000 daltons; red)
overlaid with control Cascade-Blue dextran (3,000 daltons; blue), on top of
DIC images (greyscale). Perivitelline space is found between the zygote (zyg)
and the fertilization envelope (arrow). Scale bar: 50 µm.
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