With modern plumbing and hygiene, the number of nasty microbes we humans are exposed to has plummeted, while the rate of autoimmune diseases and allergies has shot up. Are those related? Proponents of the hygiene hypothesis think so: our immune system is supposed to develop by encountering microbes, so being too clean throws it out of whack as the immune system overreacts to minor insults.
A new study found that mice raised germ-free had especially high numbers of invariant natural killer T cells (iNKT) in their colons and lungs—the mouse versions of inflammatory bowel disease and asthma, respectively. Most evidence supporting the hygiene hypothesis has just been in observed correlations, so this research that identifies a plausible molecular mechanism is good evidence for how over-cleanliness might cause immune dysfunction.
Your lungs know a bitter sensation when they taste one.
Yes, taste. In a Nature Medicine study, Stephen B. Liggett and company found receptors on the smooth muscle in the lungs that respond to bitterness, similar to the bitter taste buds on the tongue. And, Liggett found, the receptors’ reaction to bitterness is to relax the muscles, and therefore to expand airways. That was totally unexpected, he says, and opens intriguing possibilities for pulmonary treatment—for example, asthmatic symptoms could be treated by exposing these receptors to bitter compounds.
Like tastebuds on the tongue, the receptors react to bitterness, but unlike tastebuds they do not send any signals to the brain. The researchers thought the taste receptors might have evolved as a protection against toxic plants [Boston Globe]
Are we finally going to clean the skies of smog-causing nitrogen oxides and sulfur dioxide? The Environmental Protection Agency proposes new rules this week that would force power plants in 31 states, mostly in the East, to cut emissions of both to more than half of their 2005 levels by 2014.
The new rules take advantage of the “good neighbor” provision of the Clear Air Act to cut interstate transport—not cars and trucks, but the drift of air pollutants across state borders. (Air pollution, not unlike oil spills, does not respect the lines of the map) [TIME].
The Bush Administration tried to adopt a similar rule, but two years ago a U.S. Court of Appeals said the EPA had overstepped its bounds and nixed the regulations.
As a result, many power companies scaled back their investments in pollution controls. Now those companies will have to decide whether it is more cost-effective to retrofit their dirtiest power plants or shut them down [Los Angeles Times].
DNA may dictate your development, but you also wouldn’t be you without the unique mix of bacteria that make their home on your body. This week in the Proceedings of the National Academy of Sciences, researchers say that the very moment of your birth can decide for a lifetime what kind bacteria live in your body, and even whether you’ll be at a higher risk for conditions like asthma.
The uterus is a sterile environment. So, in the womb, babies don’t have any bacteria to call their own. It’s only once they enter the world that they begin to collect the microbes that will colonize their bodies and help shape their immunity [Scientific American].
How babies enter the world is the key, the team says. The studied surveyed the bacterial colonies of 10 mothers just before birth; four of those women gave birth traditionally and six did through cesarean section. When the scientists then checked up on the bacteria living in the newborns, they found that the difference in birth method decided what microbes the baby would get. Those born vaginally tended to pick up the bacteria from their mother’s vagina, while those born via C-section harbored bacterial colonies that tend to come from skin.
People fighting off winter colds and bouts of the flu typically reach for a glass vitamin C-packed orange juice, but new research suggests that vitamin D may be a better protector. People with low levels of the vitamin, which is often called the sunshine vitamin because sun exposure triggers its production in the body, are more likely to catch colds, the flu, and even pneumonia, a broad new study reports. The effect was magnified in people with asthma or other lung diseases.
Vitamin D deficiency is quite common in the United States — particularly in winter…. “People think that if they have a good, balanced diet that they will get enough vitamin D, and that’s actually not true,” said Dr. Michal Melamed…. “Unless you eat a lot of fish and drink a lot of milk, you can’t get enough vitamin D from diet” [CNN].
A microbe that has caused trouble in human stomachs for around 60,000 years may also play a role in preventing children from developing asthma and other allergies. In a new study, researchers say that a current campaign to wipe out the bacterium, Helicobacter pylori, may be having the unintended consequence of boosting asthma rates in kids.
A longtime resident of the human stomach, H. pylori went largely undetected until Australian scientists discovered it in 1979 and went on to show that it can cause stomach ulcers. Further work has linked it to stomach cancer. It’s now treated with antibiotics whenever detected [Science News]. But researchers say that when they studied health records of over 7,000 kids between the ages of 3 and 13, they found that children with H. pylori in their stomachs were less than half as likely to develop asthma. Those children were also less likely to suffer from eczema and hay fever.