Some ethicists and consumer watchdog groups worry that the newly revised federal rules governing medical research don't go far enough to protect the rights and privacy of patients.
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Research with living systems is never simple, scientists say, so there are many possible sources of variation in any experiment, ranging from the animals and cells to the details of lab technique.
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In a cluster of glowing human stem cells, one cell divides. The cell membrane is shown in purple, while DNA in the dividing nucleus is blue. The white fibers linking the nucleus are spindles, which aid in cell division.
Allen Institute for Cell Science
Gregoire Courtine, a neurologist at the Swiss Federal Institute of Technology, holds a silicone model of a primate's brain with an electrode array. The goal is to pick up signals from the brain and transmit them to the legs.