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記事によると、科学者が脳が死後腐らない理由を解明した可能性があると報告しています。通常、脳は死亡直後に他の器官よりも早く分解しますが、考古学者は4,400を超える保存された人間の脳を見つけています。この研究では、脳が千年にわたって存在する一方で、他の軟組織は消滅する理由を探求してきました。
特定の条件下では、腐敗によって保存が起きると研究者は報告しています。そのメカニズムについて、オックスフォード大学のパレオバイオロジストであるアレクサンドラ・セビール博士によれば、「酸素不足の環境下でこれらの反応は正常とは異なる方法で進展し、フリーイオン（高活性不安定分子）が周囲のタンパク質と結合することで組織全体が硬く、分解から守られる」と解説しています。つまり、腐敗と保存は特定の化学的制約下では共存するメカニズムだと研究者たちは結論付けました。
これらの研究結果はJournal of Proteome Researchに8月7日に掲載されました。
fahrbot-bot shares a report from Smithsonian Magazine: The brain is one of the first organs to begin decomposing after death. Yet archaeologists have discovered more than 4,400 preserved human brains around the world, some of which have remained intact for the last 12,000 years. In hundreds of cases, the brain was the only soft tissue left among otherwise skeletal remains. But how and why do brains sometimes persist for millennia while all other types of soft tissue disappear? This preservation paradox has stumped scientists for years. Now, however, a team of researchers say they may have solved the mystery.
If a brain ends up in a wet, oxygen-starved environment, the processes that usually cause decay can have the opposite effect, researchers report in a study published in the August 7 issue of the Journal of Proteome Research. "Under the right conditions, preservation actually arises from decay itself: The same reactions that degrade tissue can also weld the breakdown products together into something far tougher," study co-author Alexandra Seviour, a paleobiologist at the University of Oxford in England, tells Live Science's Victoria Atkinson.
Following experiments on 72 mouse carcasses (described in the article) the scientists think they know why. When oxygen is abundant, it triggers a cascading, chemical chain reaction that causes brain proteins to break down rapidly. This sequence hinges on free radicals, highly reactive, unstable molecules that "steal" electrons from nearby atoms and molecules. The process happens in the brains of living people too, and if left unchecked, can cause health problems. In low-oxygen environments, however, this chemical sequence appears to play out differently. The researchers' analyses hint that free radicals instead react and bond with nearby proteins, making the overall tissue tougher and more resistant to decomposition, Seviour tells Chemical and Engineering News' Anirban Mukhopadhyay. The findings show that "decay is not the opposite of preservation but, under specific chemical constraints, one of its mechanisms," the researchers write in the paper.
Read more of this story at Slashdot.
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