Cell 'backpacks' on the horizon

LOSING LEMMINGS - Norway's lemming population is declining and it's not because the rodents are making a mad rush off a cliff. Climate change is the suspected cause, according to a study published online last week in Nature. Researchers presented evidence that unseasonable increases in temperature and humidity are altering snow conditions - reducing the insulated zone underneath the snow layer that provides small rodents with the essentials of survival: warmth, access to food plants, and protection from predators. Without that refuge, it is difficult for young lemmings to survive. (photo by Erika Leslie)

MEDICINE
MIT engineers are affixing tiny, synthetic "backpacks" to immune cells, giving the disease-fighting cells a place to stow chemotherapy, a vaccine, or other drugs that can provide an extra punch against disease.

The backpacks - in the form of a polymer patch - are designed to take advantage of the cells' normal function, which is to seek infections, tumors, and other specific sites in the body. A backpack might carry drugs that a cell, once at an infection site, could use as crucial backup. Or, alternatively, a backpack might carry a marker that would let researchers "follow" it and thus identify where a tumor or infection was lurking.

For now, researchers have done their work in a dish, proving first that the cargo-carrying backpacks would not kill the cells. They then stuffed the backpack with minuscule magnets, and dragged the cells around with a magnet, to make sure the pack stayed put.

"It carries with it this little payload - and we can literally put anything into the backpack," said Michael Rubner, director of the center for materials science and engineering at MIT, who collaborated with biological and chemical engineers to do the work. "Immune cells will hone in on where disease is, and we're giving them a little bit of help."

BOTTOM LINE: The new drug delivery technology has many potential uses, including drug delivery, bioimaging, and tissue engineering.

CAUTIONS: This work, just one of many approaches to drug delivery, represents the first stages of research and thus far has been attempted only in a dish.

WHAT'S NEXT: Researchers will try to stuff other cargo into the backpacks, figure out how to best release the contents, and test their methods in animals.

WHERE TO FIND IT: Nano Letters, Nov. 5

CAROLYN JOHNSON

CLIMATE

Researchers from the University of Minnesota in Minneapolis and Lanzhou University in China, led by R. Lawrence Edwards, have reconstructed 1,810 years of the Asian monsoon, moisture-laden winds that blow north from the Indian Ocean bringing rain to many Asian regions, especially India and China. The winds bring with them the rain needed for a bountiful growing season.

Edwards and colleagues looked at a stalagmite, a rock column formed by the solidification of minerals from water, that had grown continuously from 190 to 2003 A.D. a kilometer inside the Wanxiang Cave in China. They first measured uranium and thorium in the stalagmite to date the different layers, and then measured the ratio of two different isotopes of oxygen in the stalagmite. The source of oxygen was dripping water from the cave roof which in turn came from the rain, and a measure of the ratio helped them calculate the rainfall during a particular time period.

They found that a drop in monsoon rains coincided with the declines of three dynasties. Rainfall was low between 850 and 930 A.D., spanning the time when the Tang dynasty declined and collapsed. This time also coincided with dry weather in the Americas and the demise of the Mayans. Similar dry periods in the late 14th and early 17th centuries coincided with the demise of the Yuan and Ming dynasties.

A period when the monsoon was strong - between 960 and 1020 A.D. - was a "golden age" in China when the Northern Song dynasty flourished, the population doubled and rice cultivation expanded.

BOTTOM LINE: There is evidence suggesting that climate played a role in the rise and fall of Chinese dynasties.

CAUTIONS: This is the first study of its kind and more work is needed to confirm these findings.

WHAT'S NEXT: Researchers will look further back in history to see if the same trend appears.

WHERE TO FIND IT: Science, Nov. 7

SENA DESAI GOPAL