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Sunday, 27 March 2016

Ageing, rejuvenation, regeneration and immortality

In my blog of 2 January 2016, I referred to a 2015 National Geographic article in which Iris Schrijver, professor of pathology at Stanford University, and her husband and astrophysicist Karel Schrijver talk about their new book "Living With the Stars: How the Human Body Is Connected to the Life Cycles of the Earth, the Planets, and the Stars" (Amazon).

In particular, I was fascinated by the following quotes by Iris and Karel that unfortunately did not fit that blog but never escaped my mind. Karel: "We tend to think of our bodies changing only slowly once we reach adulthood. So I was fascinated to discover that, in fact, we're changing all the time and constantly rebuilding ourselves. Talk about our skin".

Iris: "Most people don't even think of the skin as an organ. In fact, it's our largest one. To keep alive, our cells have to divide and grow. We're aware of that because we see children grow. But cells also age and eventually die, and the skin is a great example of this. It's something that touches everything around us. It's also very exposed to damage and needs to constantly regenerate. It weighs around eight pounds [four kilograms] and is composed of several layers.

These layers age quickly, especially the outer layer, the dermis. The cells there are replaced roughly every month or two. That means we lose approximately 30,000 cells every minute throughout our lives, and our entire external surface layer is replaced about once a year. Very little of our physical bodies lasts for more than a few years. Of course, that's at odds with how we perceive ourselves when we look into the mirror". Note: bold markings are mine.

I suppose that this ongoing process of rejuvenation determines our ageing and also separates death from immortality. There is even one species on Earth whose rejuvenation does not stop and which species is considered to be the only "immortal" species on Earth: the scarlet (medusa) jellyfish (eg, CNN, NYT, Wiki).

CNN (2014): "It's less immortality and more regeneration, but Shin Kubota - a professor at Kyoto University's Seto Marine Biological Laboratory - believes these tiny marine animals could hold the secret to perpetual life. When an adult scarlet jellyfish -- or medusa -- is injured, it goes to the bottom of the ocean floor. From there, it morphs back into its infant state, known as a polyp. Then the polyp becomes a new medusa, allowing the jellyfish to move between an adult and infant state in about two months".

Kubota has succeeded in making one jellyfish rejuvenate an incredible 12 times in the lab. But there remain many unanswered questions. "There should be a key to rejuvenation in the system of scarlet jellyfish," says Kubota. "I'd like to believe it could be applied to human beings, because genetically, jellyfish and humans are not so different." (CNN)

NYT, 2012: “There’s a shocking amount of genetic similarity between jellyfish and human beings,” said Kevin J. Peterson, a molecular paleobiologist who contributed to that study, when I visited him at his Dartmouth office. From a genetic perspective, apart from the fact that we have two genome duplications, “we look like a damn jellyfish.”

Seriously, who needs eternity anyway in this day and age??

SNAP! - The First, the Last, Eternity (1995) - artists, lyrics, Wiki-1, Wiki-2

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