Several years ago, Shinya Yamanaka of Kyoto University in Japan and other scientists developed a way to turn cells from the body, such as skin or blood cells, into stem cells, avoiding the need to destroy embryos. That work won Dr. Yamanaka a Nobel Prize.

But creating those induced cells requires genetic changes to the cells, raising some questions about whether they can be used for medical therapy.

The new technique does away with deliberate genetic changes. Instead, it involves subjecting specialized cells, like blood or skin cells, to stress.

The researchers in Kobe and Boston tried various stresses, including squeezing the cells, but found that bathing the cells for half an hour in a mildly acidic solution seemed to work best. The technique worked for cells taken from various organs of newborn mice, but the efficiency was highest using white blood cells.

The mice from which the cells were taken had been genetically engineered so their cells would glow green if Oct4, a gene associated with pluripotent cells, was active.

After the acid bath, the cells were grown in culture. Many died from the exposure to acid, but among those that survived, many were glowing green by the seventh day. The researchers called these STAP cells, standing for stimulus-triggered acquisition of pluripotency.

To prove the STAP cells could indeed turn into every cell type in the body, researchers injected the cells into early mice embryos. These embryos grew into mice, called chimeras, with cells derived from the STAP cells in all tissues of their bodies. The mice could reproduce and pass along the genetic characteristics from those cells.