Scientists in the United States have achieved something that previously seemed unthinkable: partially reviving the brain of pigs four hours earlier had been slaughtered.
The study showed that death of brain cells could stop and even restore some connections in the organ.
However, there were no signs that the brain was aware.
The astounding discoveries challenge the idea that the brain enters an irreversible phase a few minutes of losing blood flow.
At the same time, it fuels the debate over what is considered dead or alive and opens up a new way to investigate diseases such as Alzheimer's disease.
What did the researchers do?
In the first case, 32 pig brains were collected from a slaughterhouse.
Then, four hours later, the organs were connected to a system created by the Yale University team in the United States.
The equipment pumped rhythmically (to mimic the wrist) a specially designed liquid for the brain, which contained synthetic blood carrying oxygen and drugs in order to slow or reverse the death of brain cells.
The brains of the pigs received the cocktail for six hours.
What did the study show?
The study, the results of which were published in the Nature, showed a reduction in brain cell death, restoration of blood vessels and some brain activity.
Researchers they found signs of synapsesthat is, the connections through which the brain cells communicate.
The brains also showed a normal response to medication and an oxygen consumption similar to that required by a brain in its normal state.
That happened 10 hours later that the pigs were beheaded.
An electroencephalogram test showed that there were no signs of electrical activity in the brain that would indicate awareness or perception.
Basically they were still dead brains.
What could be learned?
Research has the potential to to transform the idea of how the brain dies, a process that many think is happening quickly and irreversibly, if there is no supply of oxygen.
Nenad Sestan, a professor of neuroscience at Yale University, said "cell death in the brain occurs over a longer time window than previously thought."
"What we are showing is that the process of cell death is a step-by-step process. And some of these processes can be postponed, paused or even reversed, "he explained.
How ethical are these experiences?
The pig brains used came from the pig industry, so the animals were not raised in the laboratory for this experiment.
But Yale scientists say they were worried pigs could regain consciousness, so they were given drugs to reduce any brain activity.
They were constantly monitored to see if there were any sign of higher brain functions. In that case, they would have used the anesthesia and finished the experiment, they say.
Ethics experts who write Nature, say that new guidelines are necessary for this field of research, since the animals used would be in a "gray area" where they are not alive, but neither are they completely dead.
What's it for?
The immediate benefit of this work will be for scientists who study the brain and diseases like Alzheimer.
The brain is the most complex structure in the known universe, but techniques such as freezing sections or cultivating colonies of brain cells do not allow researchers to explore the full spinning of the brain.
In the long run, scientists hope to find better ways to protect the brain after trauma such as a stroke or lack of oxygen at birth.
Andrea Beckel-Mitchener of the Brain Initiative of the National Institute of Mental Health said that "this line of research could lead to a new way of studying the postmortem brain."
However, the researchers say it is too early for the findings to make a difference for patients.
Does the meaning of death change?
Not at the moment, but some ethicists say that there should now be a debate, since people with "brain death" they are an important source of organs for transplants.
Professor Dominic Wilkinson, a professor of medical ethics and a consultant neonatologist at Oxford University, said, "Once someone has been diagnosed with" brain death ", there is really no way for the person to recover."
"The one who's gone is forever." If in the future it were possible to restore the function of the brain after death, to recover one's mind and personality, this would certainly have important implications, "he said.
But this is not the case today.
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