Get a whiff. If you have a disease, this rodent may be able to feel it.
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In 1989, The Lancet was a curious report on a dog kept licking a mole on her leg owner. The mole turned out to be a malignant melanoma. Since then, scientists have observed "disease sniffing" capabilities similar in mice and rats, which tend to prevent the sick members of their own species. Now researchers think they have understood how these animals do.
Scientists have already identified a number of mouse smell receptors, cell surface proteins in animal noses that pick up any scent of food to the smell of fear ( science NOW, August 21, 08). Neurogeneticist Ivan Rodriguez of the University of Geneva in Switzerland, and his colleagues wondered if there could be such additional receptors that respond to a disease "perfume", perhaps by detecting chemicals associated with bacteria and inflammation.
The researchers traveled the already deciphered mouse genome, looking for genes that may encode proteins of additional receptors in the olfactory system, sensory cells that connect the nose to the brain. They found the genes of five new receptors, which belong to a known family of proteins called formyl peptide receptors (HRPF).
The known HRPF include two immune system receptors that detect chemicals given off by pathogens in the blood, helping immune cells track and attack foreign bodies. Could those newly identified on olfactory cells do the same, pathogen detection, but those outside the body on another animal? Rodriguez's team exposed olfactory mouse neurons in the laboratory to pathogenic bacteria and urine of sick mice. Indeed, some of the chemicals sparked a "smell response" in neurons, as demonstrated by electrical changes in cells, the researchers report online today in Nature .
neurons with the newfound FPR receptors reside in a part of the olfactory system at the base of the brain that also sniffs sexual signaling chemicals called pheromones This zone. - the vomeronasal organ - is directly related to brain emotional center , the amygdala. "This makes a lot of sense," Rodriguez said. When a mouse detects a nearby mate, or danger in the form of the disease, he needs to trigger a quick reaction, either an attempt to reproduce or to avoid an animal nearby ill, he said .
Rodriguez team also found the smell receptors in disease gerbils and rats, but thought it unlikely that they will be discovered in the human nose. There is no evidence that we HRPF elsewhere than in our immune system, he said.
The results are "very exciting, if not a major breakthrough," says neuroscientist and expert on odor Pierre Marie Lledo of the Pasteur Institute in Paris. The discovery will open "new field" in the molecular basis of sniff out the disease, said Marie-Christine Broillet, specialist in olfaction of the University of Lausanne in Switzerland.
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