Wiring Up Biology

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Wiring Up Biology WHEN the commonplaces of one discipline are applied to an unrelated field, they can prove curiously fruitful. In 1952 two British physiologists, Alan Hodgkin and Andrew Huxley, managed just such a fruitful crossover, applying textbook physics to living tissue. They were both later knighted, and shared a Nobel prize in 1963. The experimental method they pioneered remains fundamental to research into the behaviour of nerve cells. As anyone who has ever had an electric shock knows, electricity has powerful effects on living matter. Luigi Galvani found in 1771 that electricity could make the muscles from frogs' legs contract; soon afterwards, physiologists came to suspect that all sensation and movement depended upon electric pulses in nerve and muscle. But how does electricity pass through living things? By the time Dr Hodgkin and Dr Huxley (as they then were) came to these questions, other researchers had discovered various things about nerve cells. One of the most intriguing was that messages down nerves are as loud when received as they were when transmitted--unlike messages sent down cables, which attenuate with distance. Physiologists thought that this active transmission had something to do with sudden and short-lived changes in the electrical resistance of a nerve fibre's outer membrane. The link between transmission and changing resistance was the subject of decades of increasingly intense speculation. Progress was slow because the nerves were not, as the police put it, assisting in the inquiries. Nerve fibres are made of axons, which are hairlike protrusions that grow out of nerve cells. They are small and delicate, unforgiving of rough treatment. The surges in the voltage... ... middle of paper ... ...s. Caesium blocks the potassium channels. If a nerve is bathed in TTX and caesium, there should be no membrane current at all. At the beginning of the 1970s, two groups of scientists--Clay Armstrong and Pancho Bezanilla in America, Dr Keynes and Eduardo Rojas in Britain--managed to measure the tiny current that does flow for a fraction of a millisecond under these conditions. They called this the gating current. It flows when, under the influence of a voltage across the membrane, charged molecular plugs break away to unblock the channels. Research today concentrates on matching what is known of the molecular structure of the channels, with ever finer readings of their electrical behaviour, to discover how and why the channels open and close. This continues the escape from "biological generalisations", in favour of Dr Hodgkin's and Dr Huxley's approach.

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