Urban microbes, a smarter insulin patch, medical marijuana, and links between the gut microbiome and the brain. This week in Abstract Science.

Microbial Zip Codes

(Nature, 6/22/2015, Rachel Ehrenberg)

Biologists released estimates this week showing that vertebrate species on Earth are disappearing faster than at any time since the extinction of dinosaurs. On the other hand, the world’s biggest cities are teeming with largely anonymous bacteria, viruses, fungi and protists that scientists would like to get to know better. High-throughput techniques are opening door to this microscopic world, which hopefully will lead to new approaches for monitoring bioterrorism, tracking disease outbreaks or assessing the impact of storms and pollution. Early attempts to track what’s lurking in various New York locations were described at the Microbes in the City conference June 19 hosted by the New York Academy of Sciences and New York University.

Cannabis and Teens

(The Lancet, 6/22/2015 Deborah Hasin et al)

Will medical marijuana laws cause an uptick in adolescent use of pot? That’s certainly the concern among public health scientists, but a study published this in The Lancet has, thus far, found the passage of medical marijuana laws in 23 states and the District of Columbia do not appear to have led to an increase in marijuana use among teens. An analysis of data from over one million adolescents surveyed between 1991 and 2014 found that while marijuana use was more prevalent in states that passed a medical marijuana law any time up to 2014 compared to other states, the risk of marijuana use in states before passing medical marijuana laws did not differ significantly from the risk after medical marijuana laws were passed. The study, which was conducted by Columbia University, suggests that state-level risk factors other than medical marijuana laws could contribute to both marijuana use and the passage of medical marijuana laws, and such factors warrant investigation.

A Smarter Insulin Patch

(The Scientist, 6/22/2015, Amanda Keener)

The 400 million people worldwide with diabetes must constantly monitor and regulate their insulin manually using glucose measurement devices and needles. Automatic insulin delivery systems, like mechanical pumps, are helping to deliver insulin more easily, but a new device that combines a micro needle patch with a glucose-driven biochemical reaction to control insulin release could take the control of glucose levels to a whole other level. The patch contains 121 micro needles loaded with specialized nanoparticles designed to release insulin when glucose levels are high. The findings appeared this week in the Proceedings of the National Academy of Sciences.

Bacteria and Mood Swings

(New York Times, 6/23/2015, Peter Andrey Smith)

A lot is being written lately about the human microbiome and its connection to disease. Their presence or absence has been linked to obesity, inflammatory bowel disease and the toxic side effects of prescription drugs, but the list of diseases and disease state that are influenced by the state of our gut is much longer, including mental illness. Micro-organisms in our gut secrete a profound number of chemicals, and researchers have found that among those chemicals are the same substances used by our neurons to communicate and regulate mood.

—Compiled by Senior Scientific Writer Regina McEnery