in the Dec. 6 Nmum don’t mate with

r regular partners, says Ahlund. Rather, they sneak into a tree cavity where another goldeneye fe- male, off on some errand, had started laying a clutch of eggs. The intruder lays an egg, which the nest owner then rals-

lund and Anderson monitored the for- tunes of pairs nesting at Lake Mjorn in southwestern Sweden. During of their study, they observed and analyzed egg proteins to identify the respective mothers for 383 duck

In their work, the researchers de- signed conical molecules with hydropho- bic tails and hvdroDhilic heads-a com-

Synthetic moleCUles mimic bone growth bination that‘ mide them assemble

loosely in water to form fibers just With an eve toward new bone-reuair 8 nanometers wide. The use of sulfur-

treatments, iesearchers have designed molecules that assemble into tiny fibers that serve as templates for growing hy- droxyapatite, the mineral in bone. What’s more, hydroxyapatite crystals align along the synthetic fibers much as they do along collagen fibers in natural bone.

“This [alignment] is one of the funda- mental elements of the nanostructure of bone,” Samuel 1. Stupp said in Boston at a meeting of the Materials Research Soci- ety on Nov. 26. Stupp and his coworkers, all at Northwestern University in Evanston. 111.. also reDorted their results

containing amino acids in each molecule led to strong sulfur-sulfur bonds that helped lock the structures into their cylindrical shape.

Other portions of the conical mole- cules encouraged hydroxyapatite crystal formation on the fibers, while yet other parts were designed to attract various cells in the body. The hydroxyapatite crystals’ alignment along the fibers came as a pleasant surprise, notes Stupp.

“It’s really a wonderful example of mo- lecular engineering,” comments Ulrich B. Wiesner of Cornell University, an organiz-

in the Nov. 23 SCIENCE: er of th

Molecules with thin hydrophobic tails (left) assemble themselves in water to form a tiny fiber (right).

symposium in which Stupp spoke. The Northwestern team exploited what’s known about biology and applied it to materials science, he says.

Doctors might one day r e pair bone injuries with injec- tions of nanofiber solutions, Stupp suggests. He notes that the technique might also be used for making nanos- tructures that organize nerve cells, pancreatic cells, and other types of cells into new tissues and organs. Beyond medicine, such a method might prove useful for build- ing highly aligned inorganic crystals for electronics and photonics applications.

--J. Gorman

358 SCIENCE NEWS, VOL. 160

a Cruz. Just what drove

ers on the boost

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Delayed surgery aids spinal cord repair

Holding off on spinal cord surgery until a few weeks after an injury, rather than attempting it immediately, improves the chances of regaining some powers of movement lost because of the injury, a new study of rats finds.

Spinal injuries damage neurons. These cells’ long tendrils, called axons, then can’t carry signals from the brain to mus- cles and other tissues, a formula for paralysis.

Scientists at Georgetown University Medical Center in Washington, D.C., at- tempted to repair severed spinal cords in rats by implanting spinal tissue from fetal rats either immediately after an injury or 2 or 4 weeks later. For 14 days, all the ani- mals also received infusions of neu- rotrophins-naturally occurring chemi- cals that induce axons to grow-or an inert substance.

The researchers then observed whe- ther the animals regained movement of their paralyzed hind limbs. Starting 3 weeks after surgery, rats getting delayed surgery and neurotrophins began using the limbs to stand, walk, and climb stairs markedly better than did rats that re- ceived prompt surgery as well as the neu- rotrophins, the scientists report in the Dec. 1 JOURNAL OF NEUROSCIENCE. Rats not getting the neurotrophins failed to irn- prove.

Examination of the animals at least 2 months after surgery revealed that rats getting a combination of delayed trans-

DECEMBER 8,2001