3 ms·
They are looking at those proteins in the nucleus of the lens of the eye for a reason. Didn’t you wonder why? “In vertebrates, the eye lens nucleus is composed
by kgwgk 7y ago
They are looking at those proteins in the nucleus of the lens of the eye for a reason. Didn’t you wonder why?
“In vertebrates, the eye lens nucleus is composed of metabolically inert crystalline proteins, which in the center (i.e., the embryonic nucleus) is formed during prenatal development (6, 7). This tissue retains proteins synthetized approximately at age 0 – a unique feature of the eye lens that has been exploited for other difficult-to-age vertebrates (6, 8, 9).”
https://ora.ox.ac.uk/objects/uuid:6c040460-9519-4720-9669-9911bdd03b09/download_file?file_format=pdf&safe_filename=Eye%2Blens%2Bradiocarbon%2Breveals%2Bcenturies%2Bof%2Blongevity%2Bin%2BGreenland%2Bshark.pdf&type_of_work=Journal+article https://ora.ox.ac.uk/objects/uuid:6c040460-9519-4720-9669-99...
“Because the epithelial basement membrane (lens capsule) completely encloses the lens, desquamation of aging cells is impossible, and due to the complete absence of blood vessels or transport of metabolites in this area, there is no subsequent remodelling of these fibers, nor removal of degraded lens fibers. [...] The lens fibre cells in the nucleus of an adult lens are thought to be produced during early embryonic life [2]. The lens plate is formed in the 4 mm embryonal stage. The lens fibre cells degrade all membrane-bound organelles and the older lens cells become compressed into the nucleus of the lens by the continuous formation of new fibres at the surface.”
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0001529 https://journals.plos.org/plosone/article?id=10.1371/journal...
- pvaldes 7y agoThanks for the links. It clears many things, but the main problem stills remain. Let me put you this example problem. "We have a box full of marbles and we can take two marbles out of the box each day. How many time it would take us to empty the box of marbles? As you had noticed yet, this is an unsolvable problem Now lets assume than we examine a Greenland shark's eye lense and register a value of "X" remaining radioactive carbon-14 atoms and then we take a look to a human eye lense of known age and found "Y" remaining radioactive C14 atoms. To simplify the problem we will assume that all atoms in a eye lense are trapped there forever, no new carbon atoms were physically added or removed, and the size, weight, and fiber density in the lense are the same for both human and shark. Having in mind that decay ratio is independent on taxonomy and there is not any reason to think that radioactivity would decay faster in a particular vertebrate... if X = Y; could we conclude than the shark and the human had the same age? The answer is: Not, we can't infer the shark age. And this is the same problem than with the box of marbles.
- kgwgk 7y agoI don’t understand what you’re talking about. Do you mean that radiocarbon dating of organic material in general is impossible? Do you mean that radiocarbon dating of the embryonic nucleus of the eye lens of a vertebrate in particular is impossible?
- pvaldes 7y agoBoth are possible if, and only if, some conditions are fullfilled first. I don't see nothing in the article suggesting that, and I spot at least one serious flaw in the design. But I don't know everything, and I could be wrong, obviously.
- kgwgk 7y agoThere are several papers and theses (including this one about the Greenland shark http://www2.bio.ku.dk/bibliotek/phd/Julius%20Nielsen.pdf http://www2.bio.ku.dk/bibliotek/phd/Julius%20Nielsen.pdf) looking at the isotopic profile of the different layers of fish eye lenses, down to the embryonic nucleus. Maybe all those researchers are onto something. Or maybe they are all wrong. I have no dog on this fight anyway.