- SCIENCE NEWS This Week

Wounds Interactive dressing speeds the process

received pesticide runoff. In each pond, half the enclosures were made of a film porous enough to permit parasite larvae from the surrounding pond water to enter; the remaining enclosures had a less porous, parasite-blocking film.

Kiesecker p l d 10 wood frog hatchlings of the species Rana sylvatica in each of the 36 enclosures.

After a month or so, he harvested frogs in their early stages of metamorphosis from tadpoles and examined them for deformities and trematode infec- tions.

He found that limb deformities occurred only in frogs from the par-

New, easily prepared materials promote more rapid healing of wounds in labora- tory animals than conventional dressings do, researchers report. The new films ulti- mately could quicken the recovery of burn victims and patients with skin ulcers and bedsores, the team asserts.

The iilms are in a class of materials known as hydrogels, which are networks of poly-

mers that swell in water. These new hydrogels are made from complex sugars called glycosamino- glycans (GAGs) that are normally found in theproteinantaining gel, or extracellular matrix, that surrounds animal cells.

asite-infiltrated en- FREAKY FROG Amphibians infected with To make each poly- closures. Pesticides, parasites sport extra legs. mer network, Glenn however, increased D. Prestwich and his the prevalence of deformities. Within pol- luted ponds, 29 percent of these parasite- exposed frogs harbored deformities, but in pollution-free ponds, only 4 percent of these frogs were deformed.

“My findings support the hypothesis that parasite infection explains. . . limb defor- mities,” says Kiesecker. Pesticide exposure probably exacerbates the situation by com- promising the immune system’s defense against infections, he adds.

To test this, Kiesecker conducted lab- oratory experiments with three common pesticides at concentrations within Envi- ronmental Protection Agency limits for drinking water. Tadpoles exposed to two of these pesticides had significantly fewer eosinophils, white blood cells important for staving off parasitic infec- tions.

Kiesecker describes his findings in an upcoming Proceedings of the National Academy of Scie7lces.

This is the first demonstration from a field study of alink between chemicals and parasites, says David M. Gardiner at the University of California, Irvine. This research “has demonstrated yet again the dangerous effect of exposure to low doses of chemicals,” he says.

Adds Kiesecker, the pesticide concentra- tions tested in the laboratory are likely to be common in the environment. The combi- nation of pesticides and parasites may help explain amphibian population declines in manyregions, he says. -J. PICKRELL

colleagues at the University of Utah in Salt M e City mix a solution of a modified GAG with a solution of much shorter molecules that make the GAG molecules stick together. For one hydrogel, the researchers use a modified version of hyaluronan, a nat- ural GAG that promotes wound healing. For the other, they used a modified version of a GAG called chondroitin sulfate, which until now had no known healing effect.

Prestwich and his coworkers tested these two hydrogel preparations on mice that had wounds extending through their skin. After the scientists covered a wound with one of the hydrogels, they bathed the material with saline and protected it with a conventional polymer dressing used, for example, when skin is removed for transplant to a burn site.

After 7 days, wounds treated with one of the two hydrogel materials were 33 percent more thoroughly healed than those covered with only the conventional dressing, the researchers report in the September Bio- materials. The new films slowly integrate themselves into a wound as it’s healing, says Utah team member Jane Shelby.

“The problem of wounds in the United States is really a silent epidemic,” comments Glenn Warden of the Shriner’s Burn Insti- tute in Cincinnati. In particular, skin ulcers and pressure sores plague the nation’s eld- erly and diabetic populations. These people and thosewith moderate burns might ben- efit from new dressings, he says.

Although other scientists have con- structed hydrogels from GAGs, the new

ones are easier to make, the Utah researchers claim. The team is now attempting to form their hydrogels at the wound site so that they better mold into its shape, says Prestwich. The group is also incorporating into their hydrogels growth factors that could firther speed healing.

“This is another demonstration where we’re moving toward truly matrix-based materials for the healing ofwounds-getting away from simple coverings,” comments Vincent Falanga of Roger Williams Med- ical Center in Providence, RI. -J. GORMAN

Altruistic Sperm Mouse gametes team up to Dower one winner

Imagine sperm cooperating by the thou- sands in the great race to an egg-even though only one teammate gets the prize. Researchers now report such teamwork for the first time in a placental mammal.

The sperm of the European wood mouse, Apodemus sylvaticus, hook together in long, thick trains that can double an indi- vidual’s speed, say Harry Moore of the Uni- versity of Sheffield in England and his col- leagues in the July 11 Nature.

In pondering altruism, theorists some 25 years ago proposed sperm cooperation for species in which females mate with multi- ple males. In that brutally competitive world, collaboration between sperm from the same source may be worth some sacri- fice from individual sperm. The new study suggests that’s the case in the wood mice.

Clustering sperm have turned up in some insects and squid, and most New World marsupial sperm pair up to improve their mobility. Those partnerships pale beside the story that’s unfolding for the European wood mouse.

This common mouse ranks as a“supreme sexual performer among rodents,” comments

20 JULY 13, 2002 VOL. 162 SCIENCE N E W S