'It's really been a mystery as to how the sperm does it,' says Epel, noting that many other candidates were studied before the discovery of nitric oxide.
Epel credits graduate student Richard C. Kuo for most of the work that led to the breakthrough. Kuo, lead author of the Nature study, is enrolled in the School of Medicine's graduate neurosciences program and in the School of Law.
Sea urchin sex
Because sperm and eggs are relatively easy to extract from sea urchins, biologists have been studying these small marine creatures for decades. They have long served as a model for understanding fertilization in other living beings, including people. In fact, the vital role that calcium plays in egg activation was first discovered in laboratory experiments on sea urchins.
'We now know that calcium increase occurs during fertilization of all animal eggs, as well as in humans,' says Epel. 'Whether nitric oxide increase is involved in species other than sea urchins is something we're looking at.'
Specifically, Epel's team will be analyzing cow and mouse eggs to see if they also undergo increased concentrations of nitric oxide after mating.
'If nitric oxide is involved in mammalian fertilization,' maintains Epel, 'then it could be useful in genetic engineering or cloning.'
Cloning mammals is difficult, he explains, because only a small percentage of laboratory clones develop into viable fetuses. Adding nitric oxide to a fertilized mammal egg 'might end up improving the efficiency of cloning,' he notes.
Nitric oxide also may turn out to be a necessary ingredient in successful human reproduction.
'There are lots of defects in human sperm,' notes Epel, 'and there could well be deficiencies in nitric oxide concentrations in the sperm of some males.'
If that turns out to be the case, predicts Epel, then a procedure might be developed that uses nitric oxide
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Contact: Mark Shwartz
mshwartz@stanford.edu
650-723-9296
Stanford University
9-Aug-2000