The biologists also devised an experimental technique by which they could generate the type of water flow and physical forces found in those habitats in a specialized tank. They used a computer and laser-based imaging system to study and quantify individual interactions between single sperm cells and single eggs, at long distances, away from any walls or boundaries. They are the first scientists to conduct such research.
"We now know properties of fluid motion that relate to the forces imposed at a microscopic scale on individual sperm and individual eggs as they interact," Zimmer said.
As part of the study, Zimmer and Riffell also developed mathematical models that describe the plumes of tryptophan that come off of eggs under a variety of physical conditions.
"We have theoretical models of what the plumes should look like, and images of eggs with sperm swimming around them," Zimmer said. "We mapped the empirical data on top of the theoretically predicted plumes. The question was whether sperm's attraction to eggs could be predicted from our theoretical models of the physics of what the plume looks like. The two mapped onto each other beautifully. The interaction could be predicted."
Because aspects of fluid flow in coastal ocean environments are remarkably similar to those in the human reproductive tract, the research could lead to methods to identify which human donors' sperm are the "most vigorous," with the highest probability of fertilizing an egg, Zimmer said. It may also suggest how to add fluid motion to maximize the probability of sperm fusing with an egg.
The study was funded by the National Science Foundation, the National Institutes of Health, the National Oceanic and Atmospheric Administration, and UCLA's Council on Research.
Scientists have been trying to descri
|Contact: Stuart Wolpert|
University of California - Los Angeles