Thursday, August 15, 2013

Put Your Mouse Nose On

My first experiment on human odor perception asked whether people can smell the difference between strains of inbred laboratory mice. (Bottom line: yes, we can.) In addition to having test subjects sniff live mice from a Tupperware container, we utilized an, umm, alternative odor source of biological relevance.
Dry fecal pellets provided olfactory cues sufficient for subjects to discriminate between the males of two strains of mice differing at many genetic loci (AKR and C57BL/6) as well as between H-2 types (bb and kk) within each strain.
While the resulting article has been cited 53 times (according to Google Scholar), no one since has taken up the scientific banner of mouse turd odor. Until now.

A Japanese research team has sniffed and chemically analyzed the odor of mouse turds. Not just any turds—these were from mice exposed to four different stress conditions: no bedding chips, shaking, fasting, and movement restriction.

The sniff panel data indicate that all stressors except fasting result in stronger smelling feces. The chemical data (gathered by microscale purge and trap gas chromatography-mass spectrometry) revealed 17 odor compounds, including a bunch of aldehydes, two sulfides, and everyone’s favorite fatty acid, isobutyric acid.

Most, but not all, of these volatiles were present at concentrations detectable by the human nose. While the amount of some compounds varied significantly across the stress conditions, on the whole there was a lot of overlap in the chemical profiles. The researchers intend to use quantitative poop profiles to measure, and hopefully reduce, stress in lab mice.

The study discussed here is “Analysis of odor compounds in feces of mice that were exposed to various stresses during breeding,” by Kenji Sakuma, Susumu Hayashi, Yoshiyuki Yasaka, Hiroto Nishijima, Hisakage Funabashi, Masayoshi Hayashi, Hideaki Matsuoka, and Mikako Saito, published in Experimental Animals 62:101, 2013.

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