Frozen frogs thaw out and hop away

The following story is from a December/09 blog/twitter by Anne McIlroy, science reporter for the Globe and Mail. It features the research of Dr. Ken Storey and his graduate student, Kyle Biggar.

The frogs in the freezer are frozen solid. But if Kyle Biggar takes them out, within hours the icy amphibians will thaw out. Within 24 hours they will be able to hop.

“The brains and the vital organs thaw first. The legs are the last to thaw,” says the 22-year-old graduate student from Prince Edward Island. He works in Ken Storey’s lab at Carleton University in Ottawa and he is part of a team that is investigating the seemingly miraculous ability of wood frogs to survive the Canadian winter by freezing solid.

The work might one day mean that human organs could be safely frozen and doctors wouldn’t have to race to transplant hearts or livers that are taken from a donor.

Mr. Biggar became interested in creatures that could turn to ice when he was a boy. His father told him stories about pet baby turtles that survived after freezing overnight in a bowl of water.

As an undergraduate studying biology and chemistry at Saint Francis Xavier University in Antigonish, N.S., he was fascinated by insects that could survive when the temperature dipped below zero.

Dr. Storey has been freezing frogs in his Ottawa lab for almost 25 years, gradually gaining a deeper understanding of the complex mechanisms that allow the amphibians to freeze and thaw out. He has also studied other animals, like squirrels. They don’t freeze solid, but can turn off their metabolisms and live in a state of suspended animation.

When Mr. Biggar learned of Dr. Storey’s work, he applied for a position and moved to Ottawa to pursue his PhD.

He is also working with red-eared slider turtles. Only the hatchlings can freeze solid, but as adults, they can survive a winter under an ice-covered lake.

“It is like holding your breath for half a year,” says Mr. Biggar.

Figuring out how the strange ways frogs and turtles and other animals get through the winter could have important medical applications, he says.

A heart or lung can only last a few hours after it is taken from a donor. By freezing organs, doctors could avoid the mad rush to transplant and wait for a perfect match.

Years ago, Dr. Storey discovered that the frogs have a natural cryoprotectant, something that protects their cells from being killed when frozen.

It is glucose, the same blood glucose you get from a chocolate bar or any food. When ice starts forming on their rubbery skin, frogs fill each cell in their body with glucose, which stops deadly ice from forming within each cell.

But that was just the first step. Dr. Storey and graduate students have identified and isolated genes that are turned on when frogs start to freeze and are now working on the many molecular steps involved.

Mr. Biggar is focusing on how energy-consuming pathways in the cell are shut down in animals that freeze for the winter, hibernate or spend the winter beneath the ice.

The work could offer insight into a number of diseases, including diabetes, cancer, heart attack and stroke, he says.

For example, as soon as frogs start to freeze, ice enters their skin and moves through the veins, pushing the blood through the central cavity. In effect, it shuts off the blood supply.

In humans this would cause cells to die. But in the frogs it doesn’t. Figuring out why could offer new ways to treat heart disease and stroke.

When the frogs thaw out, their hearts resume beating even before ice in the body has completely melted, and pulmonary respiration and blood circulation are restored soon thereafter, he says. Muscle reflexes return several hours later, and the frogs usually have co-ordinated movement within 14 to 24 hours.

“Frogs freeze and thaw as easily as we fall asleep and wake up,” says Mr. Biggar.