Einstein Science Reporting for Kids
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5-Nov-2004

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The science of sniffing



MHC peptides are detected by distinct populations of VSNs. This image shows the spatial representation of peptide-induced activity in VNO sensory epithelium. Image Science.
Click here for a high resolution photograph.

If you've ever been in a park full of dogs, you've seen the dogs running around and sniffing each other like crazy.

A new mouse study in the 05 November issue of the journal Science helps to explain some of the science behind this sniffing. The researchers have uncovered new clues about how chemical messages in urine and other body fluids are passed from one mouse to another. Dogs probably use a similar process.

While scientists have known for a long time that animals use urine to mark their territory and communicate all kinds of information with other animals, there are many details of this process that remain a mystery.

Tiny proteins from an animal's infection-fighting system (the immune system) appear in their urine. In a new study in mice, the authors show that some of these proteins stimulate nerve cells deep inside an organ in the nose that helps control both social and mating behavior. This organ is called the vomeronasal organ. Humans have a vomeronasal organ, but scientists say that it stopped working at some point in our evolution.

Trese Leinders-Zufall from the University of Maryland School of Medicine in Baltimore, Maryland and her colleagues say that specific nerve cells deep within the vomeronasal organ process immune system proteins with different shapes in different ways. Since each person's immune system proteins are unique just like each person's fingerprint the scientists say that these proteins identify each animal as an individual.

These proteins are not just invisible nametags. They provide specific details about another animal's immune system. From this information, animals can probably get an idea of how healthy that animal is. This is important because scientists think some animals choose their mates based on their health or on how compatible their immune systems are. The scientists say these proteins may pass on other kinds of information as well.

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