The sweet smell of science

The Senses
Massachusetts Institute of Technology researchers have managed to produce and grow, without altering their function, smell receptors in the laboratory. Olfactory or smell receptors are essentially membrane proteins present on cell surfaces and secreted by tips of cilia, tiny finger-like projections of olfactory neurons present in the nasal cavity lining. The proteins bind to odor molecules, setting into motion a cascade of events causing the olfactory neurons to "fire" so we are finally able to "smell."

For years, researchers have tried, unsuccessfully, to isolate and grow membrane proteins outside the cell. The main problem is the highly hydrophobic nature of these proteins -- they form clumps losing their stability and structure in water based solutions.

Now MIT have managed to grow these olfactory receptors successfully outside the cell. The key was finding a detergent in which the receptors would remain dissolved without losing their structure and function. Once Kaiser's group found such a detergent, they were able to grow the protein, using wheat germ extract, in large numbers in test tubes. Kaiser's group then tested the protein to confirm that the receptor's function had not been altered during the process.

BOTTOM LINE: "We now have a cell-free system to generate and test large quantities of this receptor," said Brian Cook, who initiated the research. "We can find out how smell works and make smell sensors that work like human noses."

WHAT'S NEXT: The researchers are working with several groups worldwide to develop a sensor that functions like the human nose. The sensors currently in the market are not broad spectrum and, unlike the human nose, can sense just one type of odor.

CAUTIONS: The olfactory receptor protein was grown in test tubes. In reality, these membrane proteins may be undergoing further modifications after binding to odor molecules and before we sense the odor. These modifications were not replicated in test tubes.

WHERE TO FIND IT: Proceedings of the National Academy of Sciences SENA DESAI GOPAL

Cancer
Ulcer-causing bacteria may not be all bad
Helicobacter pylori, a bacterium villanized for its links to ulcers and stomach cancer, might not be all bad. According to research set to be released today, people infected with H. pylori might actually be protected from a certain form of esophageal cancer.

Researchers from Iran and the US National Cancer Institute pooled existing published data on H. pylori and esophageal cancer to see if there's a link. Their results show that people infected with H. pylori bacteria "are half as likely to be diagnosed with esophageal adenocarcinoma than those who are not," says Farin Kamangar, one of the researchers.

To prove that the bacterial infection actually protects people from this form of cancer, further research is needed. Kamangar says that about half the world's population is infected with H pylori, so it might seem logical that the bacterium does some good.

For most of the 20th century, doctors believed that no bacteria could survive in the acidic cesspool of our stomachs. In the 1980s, a pair of Australian researchers named Barry Marshall and J. Robin Warren toppled that belief with their discovery of H. pylori and its nasty knack for causing ulcers. Research has also shown that the bacteria can cause certain forms of stomach cancer.

So is H. pylori good or bad? If the link between H pylori and lower esophageal cancer rates bears out, says Kamangar, "Expert panels need to weigh the good and bad effects of H. pylori."

BOTTOM LINE: H pylori bacteria have been shown to cause ulcers and certain forms of cancer; however, people with the infection seem to be less likely to get a specific form of esophageal cancer, called esophageal adenocarcinoma.

CAUTIONS: Correlation is not the same as cause. H pylori infection may not cause lower rates of esophageal cancer, despite the correlation.

WHAT'S NEXT: Researchers need to assess if and how the bacterial infection protects people from esophageal adenocarcinoma.

WHERE TO FIND IT: Cancer Prevention Research, Oct. 2008.

JESSICA TANENBAUM