In previous papers, we have examined turtle cortical neurons in vitro for mechanisms of anoxic metabolic depression ('channel arrest' and changes in electrical parameters). Negative results prompted the current study with the aim of examining more closely the energy profile and metabolism of turtle cortical slices. Calorimetry is used to measure heat dissipation during normoxia and nitrogen perfusion (120 min) and the results are converted into an ATP utilization rate. These indicate that the control rate of ATP utilization (1.72 µmol ATP g-1 min-1) agrees closely with in vivo whole-brain metabolic measurements. Both nitrogen perfusion and pharmacologically induced anoxic (cyanide+N2) groups depressed heat dissipation considerably compared with the control value (nitrogen 37 %; pharmacological anoxia 49 %). The resulting ATP utilization estimates indicate metabolic depressions of 30 % (nitrogen) and 42 % (pharmacological anoxia). The slice preparation did not exhibit a change in any measured adenylate parameter for up to 120 min of anoxia or pharmacological anoxia. Significant changes did occur in [ADP], ATP/ADP ratio and energy charge after 240 min of exposure to anoxic conditions. These results support the idea that the turtle cortical slice preparation has a profound resistance to anoxia, with both nitrogen perfusion and pharmacological anoxia causing a rapid decline in heat dissipation and metabolism.
In the field: an interview with Martha Muñoz
Martha Muñoz is an Assistant Professor at Yale University, investigating the evolutionary biology of anole lizards and lungless salamanders. In our new Conversation, she talks about her fieldwork in Indonesia, Costa Rica, the Dominican Republic and the Appalachian Mountains, including a death-defying dash to the top of a mountain through an approaching hurricane.
Call for new preLighters
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preLights is the preprint highlighting community supported by The Company of Biologists. At the heart of preLights are our preLighters: early-career researchers who select and write about interesting new preprints for the research community. We are currently looking for new preLighters to join our team. Find out more and apply here.
Graham Scott in conversation with Big Biology
Graham Scott talks to Big Biology about the oxygen cascade in mice living on mountaintops, extreme environments for such small organisms. In this JEB-sponsored episode, they discuss the concept of symmorphosis and the evolution of the oxygen cascade.
Trap-jaw ants coordinate tendon and exoskeleton for perfect mandible arc
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Trap-jaw ants run the risk of tearing themselves apart when they fire off their mandibles, but Greg Sutton & co have discovered that the ants simultaneously push and pull the mandibles using energy stored in a head tendon and their exoskeleton to drive the jaws in a perfect arc.
Hearing without a tympanic ear
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In their Review, Grace Capshaw, Jakob Christensen-Dalsgaard and Catherine Carr explore the mechanisms of hearing in extant atympanate vertebrates and the implications for the early evolution of tympanate hearing.
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