On pages 40 - 44, Dr. Moalem discusses the wood frog, Rana sylvatica's response to the extreme cold in the winter. In the spring time you can year the mating call of the frog, but in the winter you don't hear it at all. The frog does not hibernate, instead it buries itself under an inch or two of twigs and leaves and freezes solid.
When the temperature rises again in the spring, it thaws the frog, the heartbeat of the frog sparks, it gulps for air, color returns to its eyes, and it stretches its legs and soon returns to the woodlands to find a mate. It's like the frog returned from the dead.
Here's how it works. A few minuets after the frog senses that the temperature is dropping, it moves water out of its blood and organ cells, and pools the water in its abdomen. At the same time, the frog's liver releases large amounts of glucose into its bloodstream. This significantly lowers the freezing point of whatever water remains in the bloodstream and turns it into a kind of sugary antifreeze. The frog in effect put's its organs on ice. This relates to Big Idea 3: Living systems store, receive, transmit, and respond to information essential to life processes.
Keeping in mind how the frog freezes itself, and Big Idea 3, do you think that some day people will be able to cryopreserve themselves? Why or why not? Do you think that someday scientists will be able to mimic this process in the lab to preserve organs for transplant? Why?
(Posted by Sriya Potham, spotham4@students.d125.org)
Looking at the rana sylvatica scientists can see the selective advantages the rana sylvatica has developed as the frog can now survive the winter chill through a special type of hibernation. Through Big Idea 3 we can see that the frog is able to take the information, the cold winter weather, and respond to the info with a beneficial reaction, cyropreservation.
ReplyDeleteI believe that one day people will be able to cryopreserve themselves as many experiments have been performed and have been successful. The concept of cyropreserving is ingenious as the idea is based off metabolic rates. Not only is the temperature decreased due to the weather, but hibernating mammals can reduce the activity in their body during a state of torpor to as low as 1-2 degrees C (Campbell 871-872). The decrease in metabolic (combination of anabolic and catabolic) activity allows organisms to use very low amounts of energy in order to survive.
The success of cyropreservation is seen through the reports from University of Texas where scientists have been able to use cold freezers to preserve organisms. Using ultra-cold freezers scientists can stabilize some living cells for weeks or even years; however,liquid nitrogen is required for longer storage times. During this storage time, cyanobacteria, as is the case for all living cells, suffer severe osmotic stress and/or ice crystal damage during the freezing and thawing processes. The University of Texas explains that the most effective known ways to minimize these potentially lethal effects are to add a cryoprotective compound to the culture prior to its freezing for storage, and to control the cooling and warming rates during preservation avoiding extra damage to the organism. The University of Texas states that "We have been able to cryopreserve virtually all of the approximately 200 strains of cyanobacteria in the UTEX collection of algae [R.C. Starr and J.A. Zeikus (1993) J Phycol 29 (supp)] located in the Department of Botany at the University of Texas at Austin. This includes unicells, branching and unbranching filamentous species, marine and freshwater species, and those with heterocysts and akinetes."( http://www-cyanosite.bio.purdue.edu/protocols/cryo.html ).
This is the first step in being able to preserve humans or their organs. However, the large step that needs to be acknowledged is the size of humans compared to unicellular bacteria used by the University of Texas. Size matters when factoring metabolism as the larger an organism the more energy needed in order to survive (Campbell 868). In addition, to preserve both humans and their organs scientists need to address the irreversible and widespread damage from the formation of ice crystals at temperatures below 0 degrees Celsius as cells shrivel and collapse, extracellular matrices rip apart, blood vessels disintegrate.( http://www.the-scientist.com/?articles.view/articleNo/34190/title/Icing-Organs/). Once addressed and solved the new breakthrough innovation of refrigeration will be available and save many lives.
(Jimmy Wang, jimmypelewang@gmail.com)