5 replies to this topic

[The Whisk]

Cryonics is said to make damage when ice crystals form, grow and puncture the cell walls. What I don't get though, is how they continue to grow and puncture the cell walls as they approach them. Because, if they only grow by layers of atoms collecting on the ice crystal's surface, then how can they continue to grow when getting closer to the cell walls? For example, if the tip of the ice crystal is 1 atom in size and is touching the cell wall, and a hexagonal layer of atoms collect around it to grow, how can it grow in height any more?

[Keizo]

due to the properties of water? water is less dense in its solid form

Osmosis might be another thing

[The Whisk]

Interesting information keizo, so you're saying that possibly because of the properties of water, that when water gets colder, the molecules's increase in attraction resulting in expansion in the form of a crystal lattice is what punctures the cell walls when the final molecule is attracted to the tip with enough force despite the wall's presence. While Osmosis may also be a suspect for causing damage.

Since water at room temperature doesn't puncture cell walls, while colder water will, water's attractive force must be stronger than the momentum of water at room temperature. In our cells, at room temperature, the water molecules are already connected, and if a water molecule is attracted to the tip near the cell wall, it doesn't puncture the wall since although the molecules behind it are somewhat hard, the wall currently has more force. When the water molecules behind it are really hard, the water molecule near the wall gets to fully attract to the tip, and has more force than the wall and punctures it.

[benbest]

You have a misconception about why ice formation causes cell damage. Cryobiologists have two major competing reasons for ice-damage:

 

(1) With cooling, water osmotically moves out of cells and freezes in the extracellular space, thereby mechanically crushing tissue cells

 

(2) With cooling water osmotically moves out of cells, freezes in the extracellular space, which increases the concentration of toxic solutes that poison cells.

 

Note that neither of these explanations involve ice crystals growing and puncturing cell walls. You are correct that this would make no sense. 

Edited by benbest, 15 September 2016 - 11:36 AM.

[The Whisk]

When you say ice formation mechanically crushes tissue cells, do you mean the void of water in the cells damages them in there? Or do you mean the ice around the cells squishes them? Wouldn't ice formation closing in on them stop when it gets to the walls as I was explaining above?

 

I notice you say Cryrobiologists have 2 major competing reasons for ice-damage. When the cells are viewed under a microscope, what damage is being seen once they are brought back to room temperature? Dents? Discoloration?

[Hip]

There is an Arctic frog that during winter has 60% of its body frozen solid. The frog uses glucose and urea as cryoprotectants to facilitate this freezing without causing cellular damage.