If I am a lizard

[fredreload]

If I am a lizard at 5 years old, and my right arm limb is amputated, and I regenerate it all the way from progenitor cells, what is the age of this limb when it is fully regenerated?

[Klaynos]

Define age. And how old something is didn't really work as we can pretty quickly argue everything is the same age, that being the age of the universe. And really even that's a bit flakey because our understanding at t=0 isn't really good enough.

[Strange]

I don't think lizards can regenerate limbs. Some can regrow an incomplete tail. Salamanders are better at regrowing full limbs, I think.

 

How are you defining "age" the new limb? Surely whatever definition you use is the answer to your question.

[Sensei]

I have better puzzle: you're tree.

If somebody cut branch, put in ground, new tree will grow.

How old are they?

Suppose so, tree the next year, will have couple new branches.

We will cut again to couple new plants.

How old are they?

 

I did it with my Aronia.

 

Should I measure their age from the moment of cutting and putting to ground as separate plant?

Or should I count it from when it used to be part of bigger tree before cutting.. ?

Edited September 14, 2016 by Sensei

[fredreload]

I have better puzzle: you're tree.

If somebody cut branch, put in ground, new tree will grow.

How old are they?

Suppose so, tree the next year, will have couple new branches.

We will cut again to couple new plants.

How old are they?

 

I did it with my Aronia.

 

Should I measure their age from the moment of cutting and putting to ground as separate plant?

Or should I count it from when it used to be part of bigger tree before cutting.. ?

When you grow a tree, new sprout comes out, so the tree begins from age 0. The question I have about the limb is, does it start from progenitor cell that is already age 5, or progenitor cell of age 0 and quickly catch up to the current age of the lizard? I mean for a complete regeneration the age of the limb and age of the lizard has to match, that means something sped up the aging process for the limb

[Strange]

https://en.wikipedia.org/wiki/Ship_of_Theseus

I mean for a complete regeneration the age of the limb and age of the lizard has to match, that means something sped up the aging process for the limb

 

What do you mean by the "age of the limb"?

[StringJunky]

..., that means something sped up the aging process for the limb

Not if the 'new' part was mitotically produced from cells which are at the current level of senescence of the organism; they are the same age. The tails are actually regenerated from cartilage cells; no bone is regenerated. As far as I know, cells must be meiotically produced to put a cell at age zero i.e. start again. Cloning doesn't do this.

Edited September 14, 2016 by StringJunky

[fredreload]

Not if the 'new' part was mitotically produced from cells which are at the current level of senescence of the organism; they are the same age. The tails are actually regenerated from cartilage cells; no bone is regenerated. As far as I know, cells must be meiotically produced to put a cell at age zero i.e. start again. Cloning doesn't do this.

Well but, the new part consists of progenitor cells or stem cells in which they call it the blastema that eventually becomes the new limb, it doesn't make sense that these stem cells are at the same age as the specialized cells. They might be mitotically produced from the nearby cells, which are specialized cells, but they are still stem cells, so this makes it confusing as to whether it is an age 5 stem cell or an age 0 stem cell. Either that or they could be transformed to stem cells from these specialized cells, their age should be 0 right?

Edited September 14, 2016 by fredreload

[StringJunky]

Well but, the new part consists of progenitor cells or stem cells in which they call it the blastema that eventually becomes the new limb, it doesn't make sense that these stem cells are at the same age as the specialized cells. They might be mitotically produced from the nearby cells, which are specialized cells, but they are still stem cells, so this makes it confusing as to whether it is an age 5 stem cell or an age 0 stem cell. Either that or they could be transformed to stem cells from these specialized cells, their age should be 0 right?

A mitotically-produced cell is the same age as the cell it cloned from.

 

 

Recent data suggest that we age, in part, because our self-renewing stem cells grow old as a result of heritable intrinsic events, such as DNA damage, as well as extrinsic forces, such as changes in their supporting niches. Mechanisms that suppress the development of cancer, such as senescence and apoptosis, which rely on telomere shortening and the activities of p53 and p16INK4a, may also induce an unwanted consequence: a decline in the replicative function of certain stem-cell types with advancing age. This decreased regenerative capacity appears to contribute to some aspects of mammalian ageing, with new findings pointing to a 'stem-cell hypothesis' for human age-associated conditions such as frailty, atherosclerosis and type 2 diabetes.

http://www.nature.com/nrm/journal/v8/n9/full/nrm2241.html

The thing about stem cells is not that their age/youth is the distinctive property but their ability to make any type of cell. They still get 'old'.

Edited September 14, 2016 by StringJunky

[dimreepr]

If I am a lizard at 5 years old, and my right arm limb is amputated, and I regenerate it all the way from progenitor cells, what is the age of this limb when it is fully regenerated?

 

 

Half past three, give or take.

[fredreload]

A mitotically-produced cell is the same age as the cell it cloned from.

 

The thing about stem cells is not that their age/youth is the distinctive property but their ability to make any type of cell. They still get 'old'.

This article suggests that IPSC cell from an old donor has its molecular clock reset, including all DNA damages and telomere length. I'm not sure how he reprogrammed the IPSC cell, the lizard regeneration technique is thought to achieve with microRNA while IPSC cells I've heard about is derived from transcription factors. You think these adult stem cells can also be reprogrammed in the same way to get young stem cells? Well, it is true that the lizard's blastema might not be derived from the IPSC cells, no offense really

 

P.S. Ah, I found it, what you've mentioned is the adult stem cells found among normal cells, I'm guessing these can also be reprogrammed

Edited September 14, 2016 by fredreload

[Ophiolite]

On reflection I realise I am over 3.5 billion years old, at least as far as the living part of my ancestry goes.

[Strange]

I certainly feel like that some days.

[dimreepr]

On reflection I realise I am over 3.5 billion years old, at least as far as the living part of my ancestry goes.

 

 

Indeed, DNA is never destroyed just changed.

Edited September 15, 2016 by dimreepr

[Sensei]

 

Indeed, DNA is never destroyed just changed.

 

Everything is not destroyed, just changed.

 

p⁺ + p⁺ -> D⁺ + e⁺ + V_e + 0.42 MeV

for a start....

Protons don't destroy..

They join together to form Deuterium, then further to Helium-3, then further to Helium-4, then further to Berylium-8 and if it's going enough fast, 3rd Helium-4 hits it making Carbon-12..

and so on, so on..

The all yours atoms, are as old, as the whole Universe...

 

Everything exists forever and ever...

Just in different configuration of quantum sub-particles.

Edited September 15, 2016 by Sensei

[fredreload]

If I am a lizard and my tail got cut off, how do I know what to grow back?

[Strange]

Cell differentiation is driven by things like chemical gradients

https://en.wikipedia.org/wiki/Cellular_differentiation#Mechanisms

 

(Note that lizards don't actually grow back a fully functioning tail but, rather, a tail-shaped lump of flesh and bone.

[fredreload]

Cell differentiation is driven by things like chemical gradients

https://en.wikipedia.org/wiki/Cellular_differentiation#Mechanisms

 

(Note that lizards don't actually grow back a fully functioning tail but, rather, a tail-shaped lump of flesh and bone.

From your Wikipedia link I've read about the transcription factors for IPSC programming Oct4, Sox2, and Nanog proteins are involved, actually 4 proteins for the Nobel prize winner. Now I've made a conclusion that transcription factors and microRNA actually does the same thing here. In which both of them does the same thing in gene silencing and gene activation. Now if microRNA also plays an important role in cellular differentiation, why isn't it mentioned in the link? That's my first question.

 

Second question, can epigenetic eplains which cell turns into a muscle cell and which cell turns into bone cell, if so, how?

 

P.S. No zombie dream = =

P.S. Kids, microRNA is important

Edited September 26, 2016 by fredreload

[DrKrettin]

 

(Note that lizards don't actually grow back a fully functioning tail but, rather, a tail-shaped lump of flesh and bone.

 

The lizards which we have in our garden (Gallotia galloti) lose their tails sometimes (attacked by cat or stuck between rocks etc.). We can identify quite a few individuals including one or two who have lost their tails, and as far as we can see, the tails grow back to be as effective as the original ones. They walk normally with the new tail, and it looks the same, although we have had no reason to capture one and examine a new tail. The tails can be cut or torn off at any point and regrows from there, although it remains an unusual shape if not detached completely at the stem. It takes quite some time for a whole tail to grow back (months at least)

[Strange]

I may well be wrong then (again!). I was under the impression they were fairly non-functional.

[fredreload]

I may well be wrong then (again!). I was under the impression they were fairly non-functional.

Wikipedia says microRNA is capable of activating genes, but the video I posted only mentioned gene silencing so. The point is, if it can activate genes, that means it is capable of converting cell into stem cell like the transcription factors. There is an article says that they found microRNA in the regenerated lizard limb when it is forming a blastema, or lizard stem cells. So if microRNA is as powerful as it is, we could use it to create a transdifferentiation on our cells to reverse aging. What transdifferentiation does is it differentiate a cell to another type without going through the stem cell stage, I don't know about the details but apparently the immortal jellyfish has it thanks to Edward's post. What the IPSC stem cell is, the one that is obtained through transcription factors for as old as 82 years old cell, is showing no DNA damage, no mitochondria damage, or any signs of aging. Thing is the 82 years old skin cell has to division a few times before it becomes an IPSC stem cell. Trandifferentiate is capable of differentiating without having to divide cells. So now the point isn't trying to modify the cell's DNA, but trying to have the cell differentiate to an earlier stage. Which I speculate can be done with the correct microRNA.

 

P.S. My original plan of use with microRNA, body cells-> revert to stem cells -> differentiate back to younger specialized cells

P.S. Now body cells-> transdifferentiate to yonger cells

Edited September 26, 2016 by fredreload

[DrKrettin]

I may well be wrong then (again!). I was under the impression they were fairly non-functional.

 

The lizard's tail has extremely useful functions. The most important (again, I speak only of gallotia galloti) is deception. If an animal catches the lizard's tail, the tail detaches and squirms about as if alive. The lizard can make its escape whilst the hunter is confused. I've had that happen when trying to catch a lizard for its protection in a hazardous situation. The squirming of the tail can last a few minutes. Another use is a counterbalance. They can scale walls very effectively, and can drop off a vertical wall and re-join it further down, using the weight of the tail to flick it outwards, giving momentum to the body towards the wall to get a foothold. And they were presumably doing this long before Newton invented the conservation of momentum. I suspect the tail has an important function during mating, because of the manner in which the males and females twist around each other. ... drone...drone...