- 1.
Two recently identified channel types in Lymnaea stagnalis heart muscle cells were shown to conduct Na+ in the absence of extracellular Ca2+. They did not appear to be ‘voltage-gated’ as they were not activated by voltage. Also, they remained active over a wide range of membrane potentials. However, they were weakly ‘voltage-sensitive’ as their activity usually tended to increase with depolarization. The weak voltage-sensitivity and similarity to other non-voltagegated Ca2+ channels suggested that one or both of these channels may be receptor-operated Ca2+ channels. 2. One of the two channels had a slope conductance of 15 pS. The other appeared to have at least two subconductance states with slope conductances of 50 and 72pS. Both these conductance states had very similar open dwell-time constants and identical reversal potentials. The open dwell-time constants of both conductance states were not affected by voltage, suggesting that the channels' weak voltage-sensitivity was mediated by one of the closed states. 3. With divalent cations in the patch pipette, non-voltage-gated Ba2+ and Ca2+ currents were also detected. The Ba2+ conductance (12pS) was similar to the Ca2+ conductance (11pS).
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.
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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