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Hardy frog can survive being frozen for weeks: Amphibian's secret may lead to better ways to freeze food and aid fertility treatment

Glycerol in the frogs' blood helps to prevent freezing and ice build-up
It enables frogs to survive at low temperatures without damage to tissues
Scientists can now study water at low temperatures without it freezing
They hope the findings can improve the way we freeze eggs for IVF and other biological samples

By Katharine Sharpe and Charlotte Worrall For Mailonline

Published: 18:05 GMT, 19 May 2016 | Updated: 18:44 GMT, 19 May 2016

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A small species of frog which can survive freezing temperatures could lead to improvements in everything from medicine to frozen foods.

Eastern Wood frogs are able to freeze to temperatures as low as -8°C (-17.6°F), thawing out in spring and hopping off on their way in perfect health.

Scientists say that uncovering just how they survive being frozen for weeks on end could help provide a boost for fertility treatments, as well as cold storage of medicine and food.

Scientists are trying to mimic how Eastern Wood frogs (pictured) are able to freeze to temperatures as low as -8°C (-17.6°F) and survive. They are hopeful that using the same biological trick could provide a boost for fertility treatments, as well as cold storage of medicine and food

Biologists have shown that Eastern Wood frogs are able to enter a state of cryopreservation thanks to their blood, which contains a sugar alcohol called glycerol to stop cells from being damaged as they enter into a deep freeze.

Researchers have tried to mimic the frog's freezing process in order to improve the success rate of freeze storage techniques, used to keep cells on hold until they are needed.

Current freezing methods are not 100 per cent reliable at keeping cells alive, meaning valuable samples could be lost.

A team at the University of Leeds recreated freezing conditions to see how glycerol - nature's answer to antifreeze - interacts with water to prevent harmful ice crystals from forming.

Biologists have shown that the frogs (pictured) are able to enter a state of cryopreservation thanks to their blood, which contains a sugar alcohol called glycerol to stop cells from being damaged as they enter into a deep freeze

FROGS IN THE FREEZER

Eastern Wood frogs are able to enter a state of cryopreservation thanks to their blood, which contains a sugar alcohol called glycerol to stop cells from being damaged as they enter into a deep freeze.

In the depths of winter the amphibians are able to freeze to temperatures as low as -8°C (-17.6°F), thawing out in spring and hopping off on their way in perfect health.

Recreating the conditions, scientists showed that water molecules formed clusters that were 'protected' by a network of glycerol, which acted as a 'cryoprotectant' to prevent freezing damage.

The team says that uncovering just how they survive being frozen for weeks on end could help provide a boost for fertility treatments, as well as cold storage of medicine and food.

And the results could lead to discovering new substances which can protect living tissue from freeze damage.

Recreating the frozen frog conditions, the team found how glycerol prevents ice crystals from forming in water when cooled to -35°C (-31°F).

As the mercury dropped, water molecules formed clusters that were 'protected' by an extensive network of glycerol, with the glycerol acting as a 'cryoprotectant' - a substance that prevents freezing damage.

Glycerol could potentially be used in future to improve our understanding of the structure of water, by allowing scientists to study it at temperatures that would have previously led to freezing.

'If we understand what glycerol is doing we might be able to fine tune some of these cryoprotectants that are used to find more effective combinations,' said Dr Lorna Dougan, a researcher at Leeds and lead author of the study.

Freezing biological samples for scientific testing can often result in issues with damage from ice crystals. But cryoprotectants can prevent this and enhance the research possibilities of certain tissues, as well as sperm and egg cells.

To focus in on how the amphibian's cells survive the biting freeze and thaw, the researchers used a technique called 'Small Angle Neutron Diffractometer for Liquids and Amorphous Samples' - or 'Sandals'.

Freezing biological samples for scientific testing can often result in issues with damage from ice crystals (illustrated). But cryoprotectants can prevent this and enhance the research possibilities of certain tissues, as well as sperm and egg cells

Glycerol could potentially be used in future to improve our understanding of the structure of water, by allowing scientists to study it at temperatures that would have previously led to freezing. And the results could lead to discovering new substances which can protect living tissue from freeze damage. Pictured left are frozen sperm straws and embryos in liquid nitrogen (right)

By firing neutrons at the frozen frog, they could see the water and glycerol separating into the clusters. While the water looked like it was on the verge of freezing, but the encapsulating glycerol molecules stopped this from happening.

Dr Dougan explained that using the sensitive Sandals system helped them to achieve accurate results.

She said: '[It's] very sensitive to the hydrogen in the system, both in glycerol and water, and that gives us a wonderful handle on what those molecules are doing.

'We can fine tune the temperature and pressure in the instrument to give the environment we're looking for.'

This technique helped the team to study the structure of water at temperatures where it would normally freeze for six to eight hours.

These results could mean that the discovery of more cryoprotectants could be on the horizon, potentially leading to more improvements in cryopreservation in areas such as human fertility treatment.

The findings are published in the Journal of Physical Chemistry B.