For a human, mere minutes without oxygen (called anoxia) resulting from cardiac arrest, cerebral stroke or being trapped under water can lead to profound tissue damage and even death. However a Western painted turtle can survive anoxia for months without apparent tissue damage. Why, and how?
“Key to surviving anoxia is the shutting off of energy-utilizing cellular activities, such as the synthesis of proteins and perhaps most importantly reducing the activity of energy intensive ion pumps,” according to Leslie T. Buck, a physiologist at University of Toronto’s Zoology Department. Whereas turtles and many other animals have shutoff mechanisms, humans and many mammals don’t.
“However, basic biochemical pathways are common to almost all species, certainly among reptiles (turtles), fish, birds and mammals,” Buck said, adding: “Therefore, the basic signals and pathways that permit anoxia-tolerance in the turtle must also be present in mammals.”
In studying the natural mechanisms of anoxia tolerance, Buck’s lab focused on a particular ion channel, the N-methyl-D-aspartate (NMDA) receptor. This receptor/channel is strongly associated with anoxic damage in the mammalian brain by permitting a very large flow of calcium ions into the cell during anoxia. Unlike anoxia-sensitive mammals, this doesn’t occur in the western painted turtle’s brain.
Featured topic: Buck is also participating in “Mechanisms of metabolic depression: comparative aspects,” Sunday April 3, room 30 B/C beginning at 10:30 a.m. His presentation is scheduled for noon. Buck is presenting the research at the 35th Congress of the International Union of Physiological Sciences in San Diego, March 31 - April 5, 2005.
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