Scientists receive Nobel prize for unravelling secrets of smell
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《英国医生杂志》
As winners of the 2004 Nobel prize in physiology or medicine, Richard Axel and Linda Buck have a double claim to knowing more than most about the sweet smell of success. Cited by the Nobel Foundation "for their discoveries of odorant receptors and the organisation of the olfactory system," the two researchers have done much to explain the workings of this least understood sense.
To humans, smell has long been less than essential. But for many animals, high and low, it is central to their interpretation of the world. Yet until Professors Axel and Buck published their findings in 1991, no one had fathomed the principle by which the mammalian brain can distinguish between, and remember, several thousand odours. The explanation lay in the genes.
The first point of contact with any odour molecule is an array of odorant receptors: a family of protein molecules located on the surfaces of the olfactory receptor cells. Professors Axel and Buck, then working together on mice at New York's Columbia University, discovered that the information required to make these odorant receptors relied on no less than 3% of the mouse's genes. Mice have about a thousand receptor types. Humans have fewer genes involved in coding for odorant receptors.
The surface of each olfactory cell carries receptors of only one type. When triggered by its complementary odour molecule the receptor changes shape. Via several biochemical intermediaries, this change fires a signal that travels along the cell's nerve processes to a specific region of the olfactory bulb—the first relay station on the way to the brain.
Although one receptor recognises only one type of odorant molecule, odours in the real world normally comprise a characteristic cocktail of molecules. With each ingredient activating a different receptor type, the combined outcome is an "odorant pattern." Consequently a thousand genes specifying a thousand receptor types are able to distinguish between 10 times as many odours.
Scenting success: Professors Linda Buck (left) and Richard Axel
Credit: AP
Credit: JEFF CHIU/AP
The specificity of the receptors is maintained in the olfactory bulb, where nerve processes from each receptor type are brought together in one place. The nerves that carry the information on to the brain deliver their information to corresponding micro-regions of the cortex, where odour sensations are consciously perceived and memorised.
As with many Nobel prizes in the biological sciences, the implications for clinical medicine, if any, remain unpredictable. "The discovery of this large family of genes has revolutionised our understanding of this major sense," says Peter Brennan, research fellow in olfaction and behaviour at the University of Cambridge. "Although this work is not directly related to any major human diseases, it has opened new windows on the way the brain interprets the world around us."(Geoff Watts)
To humans, smell has long been less than essential. But for many animals, high and low, it is central to their interpretation of the world. Yet until Professors Axel and Buck published their findings in 1991, no one had fathomed the principle by which the mammalian brain can distinguish between, and remember, several thousand odours. The explanation lay in the genes.
The first point of contact with any odour molecule is an array of odorant receptors: a family of protein molecules located on the surfaces of the olfactory receptor cells. Professors Axel and Buck, then working together on mice at New York's Columbia University, discovered that the information required to make these odorant receptors relied on no less than 3% of the mouse's genes. Mice have about a thousand receptor types. Humans have fewer genes involved in coding for odorant receptors.
The surface of each olfactory cell carries receptors of only one type. When triggered by its complementary odour molecule the receptor changes shape. Via several biochemical intermediaries, this change fires a signal that travels along the cell's nerve processes to a specific region of the olfactory bulb—the first relay station on the way to the brain.
Although one receptor recognises only one type of odorant molecule, odours in the real world normally comprise a characteristic cocktail of molecules. With each ingredient activating a different receptor type, the combined outcome is an "odorant pattern." Consequently a thousand genes specifying a thousand receptor types are able to distinguish between 10 times as many odours.
Scenting success: Professors Linda Buck (left) and Richard Axel
Credit: AP
Credit: JEFF CHIU/AP
The specificity of the receptors is maintained in the olfactory bulb, where nerve processes from each receptor type are brought together in one place. The nerves that carry the information on to the brain deliver their information to corresponding micro-regions of the cortex, where odour sensations are consciously perceived and memorised.
As with many Nobel prizes in the biological sciences, the implications for clinical medicine, if any, remain unpredictable. "The discovery of this large family of genes has revolutionised our understanding of this major sense," says Peter Brennan, research fellow in olfaction and behaviour at the University of Cambridge. "Although this work is not directly related to any major human diseases, it has opened new windows on the way the brain interprets the world around us."(Geoff Watts)