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Biological Miracle – Wood Frog

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Re: Biological Miracle – Wood Frog

#121

Post by fhfjfk »

wkjagt wrote: post #118

> No heartbeat. No breathing. For the entire winter, the wood frog is like a lump of hard, frigid, icy stone carved in the shape of a frog. But it’s alive, in a state of suspended animation. I find it hard to grasp what is still alive about the frog. I mean, it's not dead so there must be something happening inside the frozen frog? How does it compare to a dead (and frozen) wood frog?

A live frozen frog has ice around it's cells. Inside the cells remains liquid because of extra glucose acting as anti-freeze.

A dead frozen frog will be frozen completely, with all the cells having ruptured walls from their insides freezing.

Re: Biological Miracle – Wood Frog

#122

Post by telgareith »

nine_k wrote: post #73
telgareith wrote: post #68

Earlier quoted context omitted.

my poor knowledge of biology says it's a deeply unsatisfying "heart beats when enough of the body has thawed for it to beat." If the heart depends on the brain at all in frogs.

It doesn't, even in humans. There is an independent circuit of special muscle cells right on it that keeps it beating. So starting and stopping the heart in a controlled manner is pretty interesting, because it has to be well-timed, and there are few obvious and reliable inputs to control it, especially when thawing.

"Even in humans"- thats a pretty steep assumption.

I am fully aware that if the human heart is severed from the brainstem it will develop A rhythm.

But what about other mammals? Dunno. Not going to assume.

Theres also the tidbit that frogs are not mammals.

Re: Biological Miracle – Wood Frog

#123

Post by ethbr1 »

cmrx64 wrote: post #104
Someone wrote: post #90

Earlier quoted context omitted.

> Maybe it is that thawing happens in reverse with the extremities, then the rest of the system thawing, with the heart being last FTA: In spring, the wood frog thaws from the inside outward. First the heart starts beating. Then the brain activates. Finally, the legs move.

The article says that, but it can’t be the normal meaning of thaw. Thermodynamically, onbiously the innermost portion of the volume is going to warm last. But in terms of the frog’s system restart order, that order makes sense.

The inside of the frog isn't actually frozen, because it's glucose-flushed.

So the sequence is more:

   1. Outside of frog thaws
   2. ??
   3. Heart starts beating

Re: Biological Miracle – Wood Frog

#124

Post by sriacha »

terribleperson wrote: post #87
plastic3169 wrote: post #82

Earlier quoted context omitted.

Where can I read more about this? If this was a fact I think people would be way more excited about cryonics. Casually browsing wikipedia suggests that we are not there yet with the ability to thawn large animals or even organs.

I can't source this because I read it years ago, but I believe that there is some science that says that a major factor (not the only major factor, but a major factor) is body mass and volume. Essentially, the speed at which the core organs go from operating temperature to frozen is crucial, and it's also important for them to be deprived of oxygen when that happens. Humans are just... too big.

There are ways to adjust cooling rates... for example route the blood externally and chill it like they do in some kinds of surgery.

Re: Biological Miracle – Wood Frog

#125

Post by Someone »

cmrx64 wrote: post #104
Someone wrote: post #90

Earlier quoted context omitted.

> Maybe it is that thawing happens in reverse with the extremities, then the rest of the system thawing, with the heart being last FTA: In spring, the wood frog thaws from the inside outward. First the heart starts beating. Then the brain activates. Finally, the legs move.

The article says that, but it can’t be the normal meaning of thaw. Thermodynamically, onbiously the innermost portion of the volume is going to warm last. But in terms of the frog’s system restart order, that order makes sense.

This frog is alive. It could detect that long-term thaw is imminent (say from sensors on its skin) and start some processes that produce heat around its heart.

Re: Biological Miracle – Wood Frog

#126

Post by Qem »

Qem wrote: post #119
crazygringo wrote: post #37

Earlier quoted context omitted.

If kept in pristine conditions (perfectly sealed to prevent evaporation leading to dehydration, deep freeze), is there a particular chemical needed for life that we might expect to break down first? Since chemical reactions happen in the freezer just slower...

> Since chemical reactions happen in the freezer just slower. Can't the gross just be kept at artificially lie temperatures to lengthen the stasis time? Say, -100C or even lower?

*the frog

Re: Biological Miracle – Wood Frog

#128

Post by maronato »

Qem wrote: post #119
crazygringo wrote: post #37

Earlier quoted context omitted.

If kept in pristine conditions (perfectly sealed to prevent evaporation leading to dehydration, deep freeze), is there a particular chemical needed for life that we might expect to break down first? Since chemical reactions happen in the freezer just slower...

> Since chemical reactions happen in the freezer just slower. Can't the gross just be kept at artificially lie temperatures to lengthen the stasis time? Say, -100C or even lower?

The article says their cells don’t freeze during hibernation. -100C would probably freeze the cells and kill them

Re: Biological Miracle – Wood Frog

#130

Post by nine_k »

telgareith wrote: post #122
nine_k wrote: post #73

Earlier quoted context omitted.

It doesn't, even in humans. There is an independent circuit of special muscle cells right on it that keeps it beating. So starting and stopping the heart in a controlled manner is pretty interesting, because it has to be well-timed, and there are few obvious and reliable inputs to control it, especially when thawing.

"Even in humans"- thats a pretty steep assumption. I am fully aware that if the human heart is severed from the brainstem it will develop A rhythm. But what about other mammals? Dunno. Not going to assume. Theres also the tidbit that frogs are not mammals.

The point is that whatever control a frog heart may have, it's not cerebral. It must be a very low-level circuit, which can be modulated from outside, but which remains autonomous.
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