每日跟讀#619: Researchers ‘reboot’ pig brains hours after animals died
The brains of decapitated pigs can be partially revived several hours after the animal has died, researchers have revealed, with some of the functions of cells booted back up when an oxygen-rich fluid is circulated through the organ.
The scientists stress that the brains do not show any signs of consciousness — for example, there was no sign that different parts of the brain were sending signals to each other — and that it does not change the definition of death. “This is not a living brain. But it is a cellularly active brain,” said Prof Nenad Sestan from Yale University, who led the research.
A number of studies have suggested brain cells might not inevitably die after blood stops circulating. Writing in the journal Nature, researchers in the US reported how they sought to examine this further by taking brains from 32 pigs that had been killed in a slaughterhouse. Four hours after their deaths the arteries of the pig brains were hooked up to a sophisticated system dubbed BrainEx, which pumped an oxygenated synthetic blood through the organ. This fluid contained a host of nutrients as well as other substances to tackle processes that lead to cell death, and the circulation was continued for six hours.
At that point, the team found the circulating fluid successfully flowed through blood vessels in the brain, including tiny capillaries, and that the blood vessels were able to dilate in response to a drug, while the brain as a whole consumed oxygen and glucose from the fluid and released carbon dioxide back into it at similar rates to an intact brain.
What is more, the cells showed certain functions, including the release of various immune-response substances when triggered. After tissues were removed from the brains and flushed of the BrainEx fluid the researchers found individual neurons were still able to function.
The team said that while the BrainEx fluid was circulating, they monitored the brains to check for any signs of organized electrical activity that might suggest consciousness. “That monitoring didn’t show any kind of organized global electrical activity,” said Dr Stephen Latham, a bioethicist and co-author of the study.
But, he said, the team had been ready for signs of consciousness. “Had that appeared they would have lowered the temperature of the brain and used anesthesia to stop that kind of activity,” said Latham, adding that at present there are no ethics committees set up for such an eventuality, and it remained unclear in any case if the technique could ever restore consciousness.
The team said the approach could provide a new way to study the brain, and even help in the development and testing of new therapies for stroke and other conditions in which bloodflow to parts of the brain is blocked, causing cells to die.
Source article: http://www.taipeitimes.com/News/lang/archives/2019/04/28/2003714163/2
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