28 • THE UNIVERSITY DAILY KANSAN
WEDNESDAY, JULY3, 2002
Study: Estrogen affects sperm
VIENNA, Austria (AP) — Researchers have found the first direct evidence that chemicals in the environment — including some in foods such as peas and beer mimic the effect of the female sex hormone estrogen on the ability of sperm to fertilize eggs.
The study was conducted with mice, but experts say human sperm behave very similarly.
Scientists reported Tuesday at Europe's annual human reproduction conference that such chemicals seem to have a much more potent effect on sperm than estrogen found in the body, and that they might make sperm burn out before reaching the egg.
Studies have shown that estrogen-like chemicals can disrupt the development of the male reproductive system and reduce the production of sperm, but this is the first time scientists have shown they affect sperm itself. Whether the effect is strong enough to cause harm is uncertain.
Sperm expert Christopher Barratt, a professor of reproductive medicine at Birmingham University, said human sperm is even more sensitive to female sex hormones than mouse sperm.
"If the effect is true, it means you would need only extremely low levels in humans to affect sperm," said Barratt, who was not connected with the research.
Lynn Fraser, a professor of reproductive biology at King's College in London, tested the effects on sperm of three pseudo estrogen chemicals and compared the results with the action of natural estrogen found in the vagina.
The three environmental chemicals were genistein, found in soya, peas and other legume vegetables; 8-prenylaringenin, found in beer, and nonylphenol, which is in products such as household cleaners, paint and pesticides.
Sperm goes through lots of changes between leaving the male and arriving at the egg. If it fails at any of those steps, it won't make it.
The final phase of sperm development, where its ability to fertilize is "switched on." is called capacitation.
Capacitation involves a specific pattern of hyperactive wiggling. The outer layer of the sperm is also remodeled and the tail becomes more flexible, giving the sperm about 10 times more energy to help it propel itself.
The process starts inside the female body, once the sperm has left the semen and started its journey to the womb through the cervical mucous. On average, it takes five hours to complete the process.
Once the sperm reaches the uterus, it wiggles into the fallopian tube and makes its way to the oviduct, where it finally
becomes quiet and stays for a day or two until it is summoned by the ovary. By this point, capacitation is complete.
In response to a signal from the ovary, the capacitated sperm travels farther up the tube to a location called the ampulla, where the egg is.
The sperm then docks onto a rubbery coat protecting the egg.
The docking triggers a cascade of events that end with the gradual rupturing of the cap over the head of the sperm, called the acrosome, which contains the enzymes it needs to penetrate the layer. The sperm then docks with the egg's shell and the tail stops swishing. The egg does the rest of the work from there.
Estrogen stimulates this process, but is not crucial to it.
The new research found that both the natural and the pseudo estrogens accelerated the capacitation process and rupturing of the sperm cap, but that the environmental chemicals did it much more quickly.
"All of these compounds stimulate, but if they keep on stimulating, at least some of the sperm will undergo an acrosome reaction (cap rupturing). Strategically, that's really not a good thing because once the sperm have undergone that reaction they can't fertilize, however much they can wiggle," Fraser said.
NEWS IN BRIEF Science fiction authors to sign novels at Union bookstore
The Mount Oread Bookshop at the University will feature several authors at a science fiction and fantasy book signing from 12:45 to 1:30 p.m., Saturday, University officials said.
Officials said the signing was to accompany the annual Campbell Conference on science fiction writing being held Friday through Sunday. The winners of the John W. Campbell Memorial Award for the bet science-fiction novel of the year and the Theodore Sturgeon Memorial Award for the best short science fiction of 2001 will be announced at an awards banquet the evening before the signing.
Officials said this year's inductions into the Science Fiction and Fantasy Hall of Fame would also occur during the banquet. They include: Samuel R. Delany, Michael Moorcock, James Blish and Donald Wollheim.
Books by the inductees will be available at the book signing, and authors Robin Wayne Bailey, James Gunn, Kij Johnson and Frederick Pohl will attend. The recipients of Sturgeon and Campell awards will also be available.
—Jay Pilgreen
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