Determining how an embryonic stem cell differentiates into mature cells might eventually allow development of methods to reprogram an adult cell. Those techniques might let the mature cell return to its "pluripotent" state, in which it is capable of turning into different cell types. Laurie A. Boyer and Richard A. Young of the Whitehead Institute of Biomedical Research and colleagues demonstrated how three proteins control this process.

Another research finding underlined the importance of exploring the complexities of stem-cell biology without satisfying the demand for immediate medical benefits. Susan L. Lindquist of the Whitehead Institute and collaborators demonstrated that the prion protein, which causes mad cow disease when malformed, has a critical stem cell-related function in the body in its normal state.

The protein appears to help maintain the body's supply of stem cells that produce blood cells. The Whitehead experimenters demonstrated the role of prions by irradiating mice to kill off blood-producing stem cells. A bone-marrow transplant was then performed to regenerate the blood precursors. In mice that lacked the protein, stem cells gradually lost their ability to reconstitute themselves.

Bush's decision to limit stem cell research to 78 existing cell lines has hindered the field. Today, far fewer cell lines are viable than the original number permitted many of which are contaminated. Rep. Diana DeGette, a Democrat, and Mike Castle, a Republican tried to loosen restrictions. They succeeded in getting support from their colleagues in Congress but were ultimately stymied by Bush's veto--the first of his administration. No one knows whether stem cell therapies will produce radically new treatments. Without the commitment to continue basic research unfettered by politics, however, that ignorance is sure to continue.--Gary Stix

Smart Tags Get Smarter

The next generation of electronic tags promises to outperform RFIDs

The proliferation of radio-frequency identification (RFID) devices over the past decade has been nothing short of remarkable. Millions of motorists rely on the RFID microchips in their E-ZPass cards to speed through tollbooths. Retailers such as Wal-Mart use RFID technology to keep track of their enormous inventories, and some pet owners have even implanted the tiny chips under the skin of their dogs and cats.

But one of the most sweeping promises of the RFID revolution -- that the devices will replace the ubiquitous bar code -- has not yet come to pass because of their cost. Although the simplest RFID tags now cost about 20 cents apiece, the unit price must fall to about one cent to make it economical for manufacturers to attach the devices to every item sold in supermarkets. Such a reduction may not be possible for conventional silicon-based tags, so researchers have been striving to build RFIDs from a cheaper material: plastic.

In 2005 a group of engineers at IMEC, a microelectronics company based in Leuven, Belgium, overcame a major technological hurdle by constructing a diode made of pentacene, an organic compound that has semiconductor properties. Because a diode restricts the flow of electricity to one direction, an oscillating radio-frequency signal transmitted by an RFID reader can induce a direct current in the tag's circuits, enabling the chip to send a return signal. (This signal tells the reader the serial number of the tagged item.) Prior to IMEC's breakthrough, organic devices were considered too slow to power RFID chips, but the Belgian group showed that their diodes could efficiently generate electricity from the high-frequency radio waves used to identify the tags.

The next step came early this year when a group led by Eugenio Cantatore of Philips Research Laboratories in Eindhoven, Netherlands, announced that it had built a fully functional RFID tag made entirely of plastic electronics. Such a chip would be much simpler to manufacture than a silicon-based tag because the design could be directly printed onto a plastic substrate. The elimination of complex assembly may pave the way for low-cost RFID tags incorporated into product packaging, providing each item with a unique identification signal instead of a bar code. And because RFID readers have a range of a few meters, supermarket clerks could speed the checkout process by scanning all the contents of a grocery cart at once.