Sex as a research variable
The article about using animal models in human health applications was informative (C&EN, March 20, page 30). The predominant use of male rodents in many studies was shown to raise serious questions about the general validity of extrapolating the results to both human sexes.
Another covert variable did not receive mention: namely, the role of the sex of the human experimenters. A study by R. E. Sorge et al. found that male mice exhibited higher levels (than females) of stress hormones when injected with a pain-inducing agent in the presence of male pheromones (e.g., soiled T-shirt) but not with similar female stimuli (Nat. Methods 2014, DOI: 10.1038/nmeth.2935). This stress reaction was replicated in the presence of pheromones from males of other species as well.
This cautionary observation adds yet another confounding variable to the complicated calculus of translating animal models to human application.
May 22, page 10: In the photo caption describing how to plate pennies, the zinc ions are reduced onto the copper surfaces by the solid zinc rather than by the copper itself, as stated originally.