On pages 40-43, Dr. Moalem talked about the ability of many amphibians to survive within extremely cold temperatures during the winter. Particularly the ability of the wood frog to stop it’s heart from working, stop all brain activity, and to stop breathing. This survival technique of the wood frog relates to Big Idea 2, which states that biological systems utilize free energy and molecular building blocks to grow, reproduce, and to maintain dynamic homeostasis. This is because as the weather becomes cold the wood frog takes water out of its system and adds large amounts of sugars into its system to maintain homeostasis and survive.
Provide the process through which wood frogs maintain homeostasis during the cold temperatures but indicating the use of the sugar and state which biological system this occurs in. Explain why you think wood frogs must go through the process of freezing while some organisms just hibernate during the cold. Compare and contrast between just placing another organism, such as a human, in a freezer and placing a wood frog in a freezer. Also explain why a wood frog would survive some ice being produced in its body while a human being would die from the ice.Lastly explain what you think should be done before human corpses can be preserved by freezing(cryopreservation) by using the freezing of frogs as a model.
Prince Morkeh(pmorkeh4@students.d125.org)
When they sense the slightes cold in the air, the frog sends a signal to its vital organs telling them to stop. The frogs heartbeat is a complete flat line.The frogs blood sugar is distributed through its circulatory system, cells stay just damp enough to continue circulating. And finally when spring arrives the frog basically melts, the heart beat picks up and we see movemnt. The frog jumps around again. The frog is an amphibian which means that it has cold blood, its blood adjusts to the climate, like snakes it can go days, even weeks without eating. Humans in the other hand are warm blooded, our temperature is actually about 98 degrees ferenheit, in a healthy state, so we can't cool our body and keep ourselves alive. The frog may look dead, but if our blood cooled down to freezing basically our body would immediately shut down, which is why we can't survive in the cold. Humans experience hypothermia if in the cold for too long since to keep our blood running and all our vital organs working, we must be warm. I think that frogs developed this ability over time, because of their camouflage predators can't eat, and bears hybernate because they as well need to be warm, bears are mammals as are we. Wood frogs developed this trait as a form of survival, just like for example bears developed the ability to sleep for a long period of time. It's just simply survival.
ReplyDeletehttp://creation.com/frozen-frogs#endRef1
ReplyDeletehttp://www.youtube.com/watch?v=Fjr3A_kfspM
Wood frogs are able to survive harsh winter conditions by altering their biochemical pathways in order to freeze safely and thaw after winter is over. This survival technique revolves around Big Idea 2, as the frog uses glucose, proteins, and various signals to induce this state and maintain homeostasis.
ReplyDeleteOne of the most dangerous aspects of surviving freezing temperatures is keeping the newly formed ice within the body from damaging organs and cell membranes. The first step after the frog senses the dropping temperatures is to move water out of its blood and organ cells. Any ice within the body is dangerous, but the frog pools the water into the abdomen, where the ice crystals will pose the least danger and the ice may actually have a positive effect. One of the reasons a human is unable to survive freezing is that humans haven't evolved to do this because it has never been practical for our survival. Therefore, the water inside of us would freeze and ice would cause a huge amount of damage to our organs and tissue.
Another thing the frog does is have the liver dump massive amount of glucose into its bloodstream through the circulatory system, pushing its blood sugar level up a hundredfold. This is done because the sugar significantly reduces the freezing point of whatever water remains in the frog’s bloodstream, serving as sugary antifreeze.
The wood frog freezes instead of hibernating due to the environments it has evolved in and due to its physical makeup. Many animals store fat and have thick fur, allowing them to live off of their fat through the winter and keep warm with their thick coat of fur(http://www.wisegeek.com/which-animals-hibernate.htm#slideshow). The frog clearly does not have fur so it is more difficult for it to maintain homeostasis in terms of temperature. So if its going to freeze, it might as well do so in a safe manner. It is also cold blooded, so it is possible for it to survive cold temperatures unlike some warm blooded animals (i.e humans). Carolina referenced bears as an example of an animal that hibernates in order to survive and that frogs don't need to maintain a high body temperature. I agree and believe that animals evolved after adapting to the conditions that they live in, and for some animals that is hibernation while for others it is freezing.
Since humans are warm blooded and don't have any of the evolved capabilities that a wood frog has,they would die if they are out in the cold for too long. Human organs and tissues cannot survive long term freezing, which makes cryogenics impossible at the moment, but that doesn't stop some people from trying (http://abcnews.go.com/Health/life-ice-world-crazy-cryogenics/story?id=14167348#.UXCROLVJOAh). Using the wood frog as a model to figure out how to freeze people and unfreeze them in the future could be valuable, but a much more practical starting point would be freezing human organs in order to perform transplants and save lives. According to organdonor.gov, an average of 18 people die each day because they can’t receive an organ transplant on time. If we are able to figure out how the wood frog is able to keep its organs functional after months of being frozen, we may be able to apply it to human organ transplants so that organs are given to people that need them in time. Many people do not get organ transplant in time because “a human kidney can be preserved for just two days outside the human body, while a heart can last only a few hours” (Moalem 42). We don’t know how to keep human organs frozen and functional for long periods of time, but the wood frog has the same major organs as humans, making it a good candidate for figuring out how to keep organs functional, a “huge breakthrough that could save thousands of lives each year” (Moalem 42). Maybe with enough time and huge technological breakthroughs we could even freeze living people and thaw them in the future, but right now that idea will stay in science fiction novels.
-Mikhail Iouchkov (mikhailiouchkov@gmail.com)
When they sense the slightest cold in the air, the frog sends a signal to its vital organs telling them to stop. The frogs heartbeat is a complete flat line. The frog is as close to dead as an animal can get yet it is still able to produce glucose and continue vital organs running. One response promoting freeze tolerance in freeze-tolerant frogs is the redistribution of up to 60% of the water normally found in tissues. Dissecting a frozen wood frog reveals that much of the ice is sequestered within the lymph system and in the coelom, where it may form without damaging delicate tissues and organs (Lee et al. 1992).
ReplyDeleteFreeze tolerance is also promoted by the rapid synthesis of glucose from liver glycogen and the distribution of this cryoprotective agent to cells throughout the body. The accumulated glucose apparently enhances the survival of cells, tissues, and organs because experimentally administering additional glucose to the frog increases its tolerance to freezing (Costanzo et al. 1993). One of the primary functions of glucose is to raise the osmotic pressure of the body fluids, which in turn reduces the amount of ice that forms at any given temperature. Glucose transported into cells acts as an osmolyte, decreasing the degree of cell shrinkage during freezing, and also serves as a fermentable fuel that can be metabolized in the absence of oxygen. The wood frog also uses urea as a cryoprotectant. Unlike glucose, urea is accumulated during autumn and early winter, and is already localized within cells when freezing begins. Some evidence suggests that urea is more efficacious than glucose in preventing cryoinjury (Costanzo and Lee 2005).
Aquaporins (AQPs) and facilitative urea transporters (UTs) are two transporter proteins that have been implicated in a wide range of physiological roles in various organisms. Recently, these proteins have been found in a variety of anurans; however, their physiological significance is not yet fully understood. In order to elucidate the importance of AQPs and UTs in osmolyte balance in hibernating frogs, we are examining expression of these proteins in frogs with varying degrees of terrestrialism. In addition we are measuring seasonal variations in expression, as well as changes in expression levels in response to winter-related stresses, in the wood frog. cells stay just damp enough to continue circulating. This is a contribution to the big idea number 2 because the frog uses its energy to maintain hemeostosis. And finally when spring arrives the frog basically melts, the heart beat picks up and we see movement. The wood frog has a large amount of proteins inside its liver, which The frog jumps around again. The frog is an amphibian which means that it has cold blood, its blood adjusts to the climate, like snakes it can go days, even weeks without eating. Humans in the other hand are warm blooded, our temperature is actually about 98 degrees ferenheit, in a healthy state, so we can't cool our body and keep ourselves alive. The frog may look dead, but if our blood cooled down to freezing basically our body would immediately shut down, which is why we can't survive in the cold. Humans experience hypothermia if in the cold for too long since to keep our blood running and all our vital organs working, we must be warm. I think that frogs developed this ability over time, because of their camouflage predators can't eat, and bears hybernate because they as well need to be warm, bears are mammals as are we. Wood frogs developed this trait as a form of survival, just like for example bears developed the ability to sleep for a long period of time. It's just simply survival.
ttp://creation.com/frozen-frogs#endRef1
http://www.youtube.com/watch?v=Fjr3A_kfspM
http://scienceblogs.com/lifelines/2011/11/07/guest-blog-freezing-wood-frogs/
http://www.units.muohio.edu/cryolab/projects/woodfrogfreezing.htm