DENVER, Sept. 22 (UPI) -- U.S. scientists say they have reversed paralysis in human spinal cord injury victims by making and transplanting a specific type of nerve cell.

The University of Colorado and University of Rochester researchers said they made two types of brain and spinal cord cells called astrocytes from the same embryo-derived precursor cell. Only one type, called GDAsBMP, promoted nerve regeneration and the recovery of limb motion when transplanted into the spinal cord at the injury site. The other type of astrocyte cell failed to promote regeneration or functional recovery, and caused pain.

Associate Professor Margot Mayer-Proschel of the University of Rochester said, "To our knowledge, this is the first time that two distinct sub-types of astrocyte support cells generated from a common stem cell-like precursor cell have been shown to have robustly different effects when transplanted into the injured adult nervous system."

Another study co-author, Professor Mark Nobel of the University of Rochester, said, "These studies are particularly exciting in … defining the optimal cell for tissue repair and identifying means by which inadequately characterized approaches may actually cause harm."

The research, which was led by University of Colorado Associate Professor Stephen Davies appears in the Journal of Biology.

Swift sees farthest gamma-ray burst

WASHINGTON, Sept. 22 (UPI) -- The National Aeronautics and Space Administration says its Swift satellite has found the most distant gamma-ray burst ever detected.

NASA said the blast -- designated GRB 080913 -- came from an exploding star 12.8 billion light-years away. The burst occurred less than 825 million years after the universe began, when the universe was less than one-seventh its current age.

"This is the most amazing burst Swift has seen," said scientist Neil Gehrels at NASA's Goddard Space Flight Center in Greenbelt, Md. "It's coming to us from near the edge of the visible universe."

Gamma rays from the explosion triggered Swift's Burst Alert Telescope at 1:47 a.m. EDT Sept. 13.

Swift, launched in November 2004, has so far detected the brightest gamma-ray burst, which was visible to the human eye despite occurring billions of light-years away. In January, the spacecraft's instruments caught the first X-rays from a new supernova days before optical astronomers saw the exploding star.

Swift is managed by Goddard, with international collaborators including the University of Leicester and Mullard Space Sciences Laboratory in England, Brera Observatory and the Italian Space Agency in Italy, and additional partners in Germany and Japan.

Flatworms aid scientists studying cancer

SALT LAKE CITY, Sept. 22 (UPI) -- A U.S. study shows a key genetic pathway for cell growth and division is similar in both humans and flatworms, or planarians.

Planarians, normally living in freshwater, are known for their ability to regenerate. A planarian cut into 200 pieces can generate 200 new individuals.

Now research suggests the planarian can help scientists understand the basis of human development and disease.

Scientists at the University of Utah and the Forsyth Institute at Harvard University report planaria contain a gene highly similar to the human gene PTEN, one of the most frequently mutated genes in human cancer. They found PTEN was present in many planaria cell types, including stem cells. Additionally, disruption of PTEN pathways in the cell resulted in abnormal growths, drastic changes in body shape and, eventually, death.

The scientists said their findings demonstrate planaria are a new animal model to use in researching the biology of human stem cells and cancer cells.

The study appears in the September-October issue of the new research journal Disease Models & Mechanisms.

Global warming has ecosystem double whammy

RENO, Nev., Sept. 22 (UPI) -- U.S. scientists have found one abnormally warm year can suppress the amount of carbon dioxide absorbed by some grassland ecosystems for as long as two years.

Researchers at the Desert Research Institute said the findings from a four-year study of sealed, 12-ton containerized grassland plots is said to be the first to quantitatively track the response in carbon dioxide uptake and loss in entire ecosystems during anomalously warm years.

"The 'lagged' responses that carry over for more than one year are a dramatic reminder of the fragility of ecosystems that are key players in global carbon sequestration," said research Professor Jay Arnone.

The four-year Desert Research Institute study involved native Oklahoma tall grass prairie ecosystems that were sealed inside four, living-room-sized environment chambers. The dozen 12-ton, 6-foot-deep plots were extracted intact from the University of Oklahoma's prairie research facility near Norman, Okla. Scientists replicated the daily and seasonal changes in temperature and rainfall that occur in the wild.

They found ecosystems exposed to an anomalously warm year had a net reduction in CO2 uptake for at least two years.

The research is detailed in the journal Nature.