Investigations on the Activation of Strongylocentrotus Purpuratus Eggs by Homologous Sperm (or, Why Do the Male Gametes Lose it so Quickly?)
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Authors
Human, Kathleen
Issue Date
1991
Type
Thesis
Language
en_US
Keywords
Alternative Title
Abstract
Although egg activation and early fertilization events have been
extensively observed in sea urchin Strongylocentrotus purpuratus, actual
mechanisms involved in activation remain elusive. Diverse experiments
were undertaken to clarify the trigger(s) involved. As one preliminary test,
the naked egg was probed with various plant lectins in hopes of locating and
identifying an hypothesized egg plasma membrane receptor for sperm.
Theoretically, lectin binding might have directly activated the egg through a
G-protein intermediate, or it could have blocked sperm access to the receptor.
None of the lectins used either initiated activation parthenogenically or
inhibited subsequent fertilization by sperm. These results do not imply that
there are no sperm receptors on the egg cell membrane, but suggest that if
they do exist, that the simple probes used in this study were not adequate to
locate them. The next set of experiments focused on the other partner in
fertilization; the sperm. Once acrosome-reacted, S. purpuratus sperm quickly
lose viability, and by asking why, we hoped to find clues as to how activation
occurs. Viability of acrosome-reacted sperm were assayed by percent of eggs
fertilized and experiments were performed under several circumstances. To
test one hypothesis that heavy calcium influx "poisons" sperm, reacted sperm
were incubated in calcium-free seawater. Sperm viability over time was not
enhanced and we conclude that calcium influx does not result in sperm
degradation. We removed the vitelline layer from eggs and assayed
fertilization to determine if the sperm lost an enzyme or lysin necessary for
penetration of egg cell layers. Acrosome-reacted sperm were clearly able to
fertilize these eggs for a longer period of time indicating that some substance
necessary for vitelline layer penetration is lost after induction of the acrosome
reaction. It was also observed that sperm binding to eggs was negatively
affected with time after induction of the acrosome reaction, although sperm
motility remained unaffected. These final results imply that degradation of
the sperm protein bind in may be another factor contributing to the time-dependent
loss of sperm viability.
Description
vii, 32 p.
Citation
Publisher
Kalamazoo College
License
U.S. copyright laws protect this material. Commercial use or distribution of this material is not permitted without prior written permission of the copyright holder.