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5 December 2013 11:26 am ,
Vol. 342 ,
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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How the Nose Knows
5 March 1999 6:30 pm
Neurobiologists have sniffed out how the nose uses relatively few kinds of molecular sensors to discriminate among thousands of odors. As reported in today's Cell, different smells activate unique suites of these sensors. The sensors, called odorant receptors, are so sensitive to the chemical makeup of incoming odors that just a slight difference turns a smell from sweet to rancid.
For almost a decade, neurobiologists have suspected that odors activate different sets of receptors in the mammalian nose. A team led by Linda Buck of Harvard Medical School in Boston was able to test this proposition with mouse olfactory nerve cells. For each of a dozen odors, Takaaki Sato from the Life Electronics Research Center in Amagasaki, Japan, looked to see which cells increased their calcium concentration, which occurs as nerve cells fire. In addition, Bettina Malnic of Harvard determined which receptor genes were active in individual nerve cells to learn which odor receptors were present in each. "This was a very elegant and clever approach," says neurobiologist Stuart Firestein of Columbia University in New York City.
Each nerve cell contained one distinct type of receptor that was sensitive to more than one odor. Although only a small percentage of neurons were active at one time, every odor stimulated a unique subset of receptors. Changing the concentration also alters slightly which nerve cells fire a signal to the brain. Although the team studied only 13 of the 1000 different receptors and tested them with relatively few chemicals, the results "give us the beginning of an interesting set of rules" for odor discrimination, says Firestein. Thus, one chemical can smell delightful while an almost identical one can be repugnant because they activate a slightly different suite of receptors.
The techniques used in these experiments can help researchers identify the kinds of receptors that recognize specific odors, says Buck. Other researchers think this work could eventually lead to synthetic odors that could be used in pest control. More broadly, a better grasp of how olfactory receptor sensitivity depends on chemical structure could reveal universal secrets of receptor function, Firestein adds.