S C I E N C E N E W S

The investigators then took tissue sam-ples from the uterine walls of women at dif-ferent stages of their menstrual cycle. Theteam discovered that during the window ofreceptivity, the wall’s inner surface beginsto display several L-selectin–binding car-bohydrates. Fisher and her colleagues alsoshowed that an antibody to L-selectin inhib-ited lab-grown trophoblasts from bindingto uterine tissue harvested during the win-dow of receptivity.

Compounds that block L-selectin or itspartners could offer a new form of femalecontraception, says Daniel Carson of theUniversity of Delaware in Newark.

However, Susan J. Kimber of the Uni-versity of Manchester in England cautionsthat Fisher’s group hasn’t directly shownthat human embryos use L-selectin for theirinitial uterine attachment. Moreover, Kim-ber says, her research team has failed tofind L-selectin on human embryos.

But if L-selectin is crucial to implanta-tion, it may explain why some women withsexually transmitted diseases or other gen-ital infections have trouble conceiving.Infections can cause cells to shed L-selectin,which could hinder an embryo from attach-ing to the uterus, Fisher explains. —J. TRAVIS

Testosterone’sFamily TiesHormone-linkedproblems reflect parent-child bond

Testosterone has a public reputation as thehormone that turns men into boisterouslouts at best and violent criminals at worst.

New evidence is challenging that. Wit-ness a new study that finds no link betweentestosterone concentrations and eitherdelinquent behavior or depression in chil-dren and teenagers of both sexes—that is,if relations with parents are close.

The behavior and mood problems tradi-tionally blamed on testosterone most oftenappear in boys and girls with poor parentalrelations, says sociologist Alan Booth ofPennsylvania State University in State Col-lege. In the new study, high-testosterone boyswho related well to their mothers engaged infar fewer delinquent acts than low-testos-terone boys who got on poorly with theirmothers, Booth and his colleagues report inthe January Developmental Psychology.

“Children’s testosterone levels createbehavioral predispositions that get modifiedby the quality of parent-child relationships,”Booth theorizes.

As a hormone that shapes masculinephysical features, testosterone occurs insmall amounts in females and much largeramounts in males. Among men, many stud-ies have associated high testosterone con-centrations with aggressive and risk-takingbehaviors and low testosterone concentra-tions with depression. However, some stud-ies have failed to find links between men’stestosterone levels and behavior or moodproblems. Only a few studies have addressedthis issue in women or in children.

The new investigation by Booth’s groupfocused on 400 middle-class families inPennsylvania. All the parents and 608 chil-dren, ages 6 to 18, were interviewed andprovided saliva samples for testosteroneanalysis. The researchers defined a goodparent-child relationship as one in whichthe parent knew about and approved of thechild’s activities, the parent participated inactivities with the child, and the childreported feeling close to the parent.

An intriguing sex difference emerged foryoungsters with poor parental relationships.Among these boys of all ages, those withhigh testosterone concentrations were mostprone to delinquency, illicit-drug use, andother risky behaviors. Yet among girls, riskybehaviors most often appeared in thosebetween ages 10 and 14 and with low testos-terone concentrations.

Moreover, low testosterone concentra-tions were linked to symptoms of depressionin boys of all ages who related poorly to theirmothers. The same association emerged forgirls only between ages 14 and 18 who hada poor relationship with their fathers.

Reasons for these sex disparities areunclear, Booth says. Larger studies shouldexamine testosterone’s link to behavior atvarious ages, he adds.

Besides revisiting testosterone’s bad rep-utation, researchers need to probe for ben-eficial behaviors linked to the hormone,remarks sociologist Allan Mazur of Syra-cuse (N.Y.) University. “Under the right socialconditions, high testosterone levels may helpto produce our leaders,” Mazur says. “No onehas studied this possibility.” —B. BOWER

Quick-ChangeSurfaceMaterial repels water on command

In an advance that could open new routesto sensors, drug delivery, and many othertechnologies, researchers have modified agold surface so that it switches from a water-

attracting mode to a water-repelling oneon command. With that capability, a flip ofa switch could cause drug molecules, pro-teins, or cells to collect on the surface or tosuddenly be released from it.

The turncoat layer, atop a gold-coatedwafer, is made of neatly aligned, chainlikemolecules that stand up like bristles on abrush. The molecules’ tips exposed to theworld are negatively charged and attractwater, but the molecules’ midsections shunwater. When scientists apply an electricfield to the wafer, the gold attracts the mol-ecules’ negative tips and each bristle bendsover, exposing its hydrophobic belly.

Since no chemical bond breaking orbond forming occurs, the process is easilyreversible, says Joerg Lahann of the Mass-achusetts Institute of Technology (MIT).He and his colleagues from MIT and theUniversity of California, Santa Barbaraand Berkeley describe their surface in theJan. 17 Science.

Making the surface took some computa-tion and a neat chemical trick. When thebristle molecules assemble themselves ontoa gold surface, they usually pack together sotightly that they can’t bend over. To over-come this problem, Lahann and his cowork-ers ran simulations that showed that eachmolecular bristle needs at least 0.65 squarenanometer to bow. So, the team found achemical group that takes up about 0.67 square nanometer of space and linkedit to the negatively charged tip of the molec-ular bristles. Once these mushroom-shapedmolecules assembled on the gold, they eachoccupied about 0.67 square nanometer.When the scientists chemically lopped offthe molecules’ space-filling heads, each bris-tle had enough room to bend over.

“This is quite creative work,” commentschemical engineer Manoj K. Chaudhury of

3 6 J A N U A R Y 1 8 , 2 0 0 3 V O L . 1 6 3

SCIENCENEWSThis Week

ALL TOGETHER Molecules with water-lovingtips (yellow) bend over and expose theirwater-avoiding parts (blue).

LAH

AN

N E

T A

L.

FOBs.1-18 1/15/03 3:12 PM Page 36

W W W. S C I E N C E N E W S. O R G J A N U A R Y 1 8 , 2 0 0 3 V O L . 1 6 3 3 7

M.L

IPM

AN

/CA

NA

DIA

N M

USE

UM

OF

NA

TUR

E

Lehigh University in Bethlehem, Pa. For usein many technologies, the technique needsto produce a surface that is even more repel-lant to water than those in the tests so far, henotes. Then the method would prove useful,for example, in microfluidic devices in whichfluid must be reliably directed throughexquisitely fine pathways. —J. GORMAN

Nifty SpittleCompound in bat salivamay aid stroke patients

When a vampire bat bites an animal, itssaliva introduces an anticlotting agent tokeep the blood meal flowing. Scientists nowreport that this compound, which busts upblood clots as well as the leading medica-tion for treating strokes does, avoids one ofthe drug’s major drawbacks.

Researchers injected mice with chemi-cals that induce brain damage like thatbrought on by the most common type ofhuman stroke—clots that block vessels andsubsequently starve brain tissue. The sci-entists then injected some mice with thebat-saliva compound, called Desmodusrotundus salivary plasminogen activator(DSPA). They injected others with the stan-dard clot-busting drug, tissue plasminogenactivator (tPA), which shows the side effectof initiating damage to brain neurons. In themice, DSPA caused less than 1 percent asmuch neuron damage as tPA did, theresearchers report in the February Stroke.

Animal studies have established that tPAleads to the death of neurons, although sci-entists are still investigating the specificmechanism of the damage.

The new finding suggests that DSPAdoesn’t sabotage brain cells, says studycoauthor Robert L. Medcalf, a biochemistat Monash University in Victoria, Australia.

In two current studies, scientists areassessing DSPA’s effectiveness when given topeople up to 9 hours after a stroke. Resultscould be available by the end of this year, saysMariola Söhngen, a physician and managingdirector of Paion, the company commer-cializing the drug in Aachen, Germany.

“This could be potentially very exciting, ifDSPA is really better then tPA,” says StuartA. Lipton, a neurologist at the BurnhamInstitute and the University of California,San Diego. He and others are studying com-pounds that might mitigate tPA’s drawbacks.

For stroke victims, tPA “is a two-edgedsword,” Lipton says. Doctors don’t typi-cally give the drug to someone more than3 hours after a stroke because risks of dam-age, whether from neurotoxicity or bleed-ing in the brain, outweigh the benefits.Söhngen notes that in people, it’s difficultto identify damage caused specifically byneurotoxicity.

The 3-hour window limits tPA’s useful-ness because a stroke’s immediate symp-toms can be subtle, and many people don’tget to a hospital within that period. Amongpeople who do, roughly 6 percent of thosereceiving tPA suffer some brain bleeding,says neurologist John R. Marler of theNational Institute of Neurological Disor-ders and Stroke in Rockville, Md. —N. SEPPA

Northern VentsArctic shows surprisinghydrothermal activity

A recent survey along a midocean ridgebeneath the Arctic icepack unveiled anunexpected abundance of hydrothermalactivity. Besides casting doubt on currenttheories about where such vent systems canarise, the wayward vents could harborecosystems that are dramatically differentfrom those found in other oceans.

Midocean ridges are seams where mate-rial wells up from Earth’s interior to formnew seafloor, explains Hedy Edmonds, amarine geochemist at the University ofTexas’ Marine Science Institute in PortAransas. In 2001, she and other scientistsused icebreakers to plow their way acrossthe Arctic Ocean to make measurementsalong a 1,100-kilometer segment of the1,800-km-long Gakkel Ridge. That little-explored midocean ridge, which is spread-ing slower than other known seams, runswithin 350 km of the North Pole and lies

at frigid depths between 4,500 and 5,000meters.

Edmonds and her colleagues dredgedthe ocean floor for rocks at more than 150sites along the ridge. As the dredgedropped to the seafloor, instrumentsattached to its cable measured the tem-perature and optical properties of the sea-water. That’s when evidence for ventsstarted pouring in. At 119 sites, research-ers found thick layers of water with highconcentrations of suspended particles. At58 of those spots, those light-scatteringlayers were warmer than those above andbelow. Water from some sites containedmanganese, often a component of the min-eral-rich water discharged from vents. Thedata suggest there are 9 to 12 vent systemsalong the surveyed segment.

Until recently, most scientists thoughtthe amount of hydrothermal activity alonga particular portion of a midocean ridgedepended on the rate of seafloor spreadingthere, says Edmonds. Her team’s survey,described in the Jan. 16 Nature, found dou-ble to triple the number of vent systemsthat current models predict.

The newfound vents may soon catch biol-ogists’ attention. Hydrothermal vents oftenhost thriving ecosystems that are nourishedby the warm, mineral-rich fluids. The bio-logical communities that surround theGakkel Ridge’s vents may be significantly dif-ferent from those that populate hydrother-mal systems elsewhere, says Cindy L. VanDover, a biological oceanographer at the Col-lege of William and Mary in Williamsburg,Va. Deep parts of the Arctic Ocean contain

GOOD GUY? The saliva of the common vampire bat, Desmodus rotundus, contains acompound that might yield a new drug for dissolving blood clots in stroke victims.

FOBs.1-18 1/15/03 2:28 PM Page 37