Word: proven
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...grown outside of the body. In fact, he says, just about every human cell can now be cultured in a Petri dish - something that wasn't true 20 years ago, when Atala began his regeneration research. The only exceptions are pancreas, liver and nerve cells; so far these have proven too finicky to survive outside their human home...
Creating a working organ hinges on keeping those first few cells alive, which has proven to be the biggest challenge for Atala's team. Each cell - whether from the bladder, skin, cartilage, or heart - prefers a different environment to grow, made up of unique cocktails of growth factors, enzymes, proteins and other nutrients. Once the incubated cells have multiplied to a sufficient number, Atala puts them through a series of rigorous tests to ensure that they look, act and function just like their normally grown siblings in the body...
Earlier this year, Atala's group became the first to make another valuable discovery: that amniotic fluid contains stem cells. These have proven critical in helping his team to regenerate tissues from the more ornery cells of the pancreas, liver and nerves, which don't grow as well in a lab dish. Amniotic-fluid stem cells aren't as versatile as embryonic stem cells, which can turn into every tissue type in the body, but they can still develop into an impressive number of much-needed cell types, and Atala has already used them to grow up muscle, bone...
...officer tasered an autistic teenager who had been running in and out of traffic as he tried to escape a treatment center. Other cases across the country include the use of Tasers on pregnant women, the elderly and children as young as six. Tasering someone on drugs has proven to be especially dangerous and often lethal...
...like lifting the ban on U.S. travel to Cuba - something even most Cuban-Americans in Miami now favor, and which many Cuba watchers suggest the Castros actually fear. Bush insisted that engaging Cuba now would just give "oxygen to a criminal regime." But, argues Colvin, "American citizens have always proven the best ambassadors of freedom and democracy...