YSF 2017 lecture #9

  • Thursday,  28th September 2017
  • 12.45-1.15 p.m
  • LT Excellence



How gut bacteria may affect anxiety

illustration of human gut

Tiny molecules in the brain may help gut bacteria hijack people’s emotions.

Bacteria living in the human gut have strange influence over mood, depression and more, but it has been unclear exactly how belly-dwelling bacteria exercise remote control of the brain (SN: 4/2/16, p. 23). Now research in rodents suggests that gut microbes may alter the inventory of microRNAs — molecules that help keep cells in working order by managing protein production — in brain regions involved in controlling anxiety.

The findings, reported online August 25 in Microbiome, could help scientists develop new treatments for some mental health problems.

Mounting evidence indicates “that the way we think and feel might be able to be controlled by our gut microbiota,” says study coauthor Gerard Clarke, a psychiatrist at University College Cork in Ireland. For instance, the presence or absence of gut bacteria can influence whether a mouse exhibits anxiety-like behaviors, such as avoiding bright lights or open spaces.

Clarke and colleagues compared normal mice, whose gastrointestinal tracts were teeming with bacteria, with mice bred in sterile environments, whose guts didn’t contain any microbes. The researchers discovered that in brain regions involved in regulating anxiety — the amygdala and prefrontal cortex — microbe-free mice had an overabundance of some types of microRNA and a shortage of others compared with normal mice. After scientists exposed some sterilized mice to microbes, the rodents’ microRNA levels more closely matched those of normal mice.

The team also examined microRNAs in the amygdala and prefrontal cortex of rats whose gut bacteria had been decimated by antibiotics. These rats overproduced or underproduced some of the same microRNAs that were off-kilter in bacteria-free mice. The researchers suspect that gut bacteria affect their host’s anxiety levels by tampering with microRNAs in specific parts of the brain.

“I was a little surprised by the findings — in a positive way — because I think not many people so far have thought about microRNAs in this context,” says Peter Holzer, a neurogastroenterologist at the Medical University of Graz in Austria who wasn’t involved in the study. “It’s heading into a new area in gut-brain research that hasn’t been pursued.”

Researchers still aren’t sure how these bacteria dial microRNA production up and down in the brain. Maybe the microbes send signals along the vagus nerve, a kind of information highway that runs from gut to brain. Or perhaps bacteria churn out molecular by-products that provoke the immune system to produce chemicals that cause the brain to produce more or less of particular microRNAs. Outlining microbes’ mental manipulation scheme from start to finish “is still a work in progress,” Clarke says.

Next the team wants to see if probiotic drugs can cultivate certain types of bacteria in the gut, and therefore fine-tune microRNA levels in specific parts of the brain. If scientists can adjust microRNA abundances in a way that assuages anxiety, it could help lead to the development of new medications for psychiatric and neurological disorders.

MicroRNA-based medications may be unrealistic in the short term, though, says gastroenterologist Kirsten Tillisch of UCLA. “People tend to like to extrapolate these types of results to humans and start moving quickly towards clinical applications. It is just so tempting,” says Tillisch, who was not involved in the study. “But we know historically the translation from lab animal to human is hit-and-miss.”

source: Science News

Sunscreen Made From DNA Would Last Forever

A DNA-based sunscreen that not only stops harmful ultraviolet (UV) light, but also becomes more protective the longer you expose it to UV rays? That’s the dazzling premise behind a recent study published in the journal Science Reports.


While sunscreen isn’t the only form of sun protection (there’s always protective clothing and floppy hats), the reality is that most of us just skip it. A 2015 study in Journal of the American Academy of Dermatology found that only 14.3 percent of men and 29.9 percent of women routinely use sunscreen when they are in outside for more than an hour. This wouldn’t be a problem, except, “Ultraviolet light is a carcinogen,” Guy German a biomedical researcher at Binghamton University in New York and an author on the study, tells PopSci. “We know it can give you a tan, but it can also cause cancer as well.”

While dermatoepidemiologists (scientists who study diseases of the skin) suspect that sunlight causes cancer because it damages DNA in our cells, German and his colleagues were looking at DNA in an entirely different way. They wondered what would happen if they exposed DNA film, essentially a thin sheet of the stuff, to the same kind of ultraviolet light we get from walking in sunshine.


Continue reading “Sunscreen Made From DNA Would Last Forever”

Newborn baby’s infection offers a cautionary tale about placenta pills

placenta pills

When I was pregnant, I spent a lot of time searching for good information about how to keep both my baby and myself healthy after birth. Googling “placenta” and “eat,” I got a list of stories that reached nearly opposite conclusions about the practice.

Some say eating the organ will replenish mom’s nutrients, increase breast milk production and even stave off postpartum depression. Others point out that there are no studies that report these benefits, and placenta eating comes with risks. Scientists and doctors still have a lot of unanswered questions about the safety of the practice.

Here’s one story new mothers considering eating their placenta might want to pay extra attention to: Oregon doctors suspect that contaminated placenta pills may have caused a dangerous infection in a newborn.

Just after birth, this newborn had trouble breathing. Tests revealed a blood infection with Group B Streptococcus, or GBS. These bacteria are found in about a quarter of healthy women’s nether regions and can pose a danger to newborns. The baby probably picked up a GBS infection while passing through the birth canal.

After a round of ampicillin, the baby went home healthy. But five days later, the baby was in trouble again. Doctors at a second hospital found more GBS in the blood. After another round of antibiotics, two types this time, the baby was again sent home.

Doctors at the second hospital learned that three days after the baby had been born, the mother had begun eating six placenta capsules daily. She had hired a company to clean, slice and dehydrate her placenta before grinding it up and putting it into pills. Lab tests found the exact same strain of GBS that had infected the baby in the placenta pills. Genevieve Buser and colleagues published the case details June 30 in the U.S. Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report.

Buser, a pediatric infectious disease physician at Providence Health System in Portland, Ore., says the situation represents the first time researchers have turned up harmful bacteria in encapsulated placenta. “But then, I don’t think that anyone has looked.”

The mother’s breast milk tested negative for GBS. GBS can live in both men and women, mainly in the digestive tract, anus, vagina and, occasionally, skin. The placenta pills could have been dosing the mother regularly with the bacteria, boosting bacterial loads on her skin and in her digestive tract. Through touching, those bacteria could have been transferred to the baby.

The fact that the same strain of bacteria was found in the pills and in the baby’s blood led the researchers to suspect that the pills — and the mother — were a likely source of the infection. Still, Buser cautions that the bacteria transfer from pills to mom to baby “can’t be proven in one case study.”

Other sources of infection exist: The mother could have been colonized in a different way, the bacteria could have come from another person, and the placenta pills could have been contaminated after they were made. “This case report raises more questions than it answers,” Buser says. “But that is good and what science and medicine are all about.”

The baby probably picked up the first GBS infection during birth. With all the excitement of a new baby, it’s easy to forget that the placenta also passed through the same birth canal, picking up the same bacteria that live there. And anyway, placentas aren’t sterile. They’re actually home to swarms of various microbes.

Bottom line, Buser says: “This is a human tissue that is not sterilized.” She points out that dehydrating meat, including placenta, isn’t enough to kill bacteria that can make people sick, including forms of E. coli and Salmonella. A snack texturally similar to placenta, dried deer jerky, sickened people in Oregon in 1995 with E. coli O157. In later lab tests, 10 hours of drying failed to kill that bacteria.

Placenta pills (and other placenta recipes) aren’t regulated, which means there’s no way to tell if the product is safe. Nor is there a foolproof way to spot potentially harmful infections in mothers. In this case, the mother tested negative for GBS at 37 weeks of her pregnancy. That was either a bad test or she acquired the infection after it. There were no signs that she — and ultimately, her placenta — was colonized by bacteria that may have been harmful to her baby.

In their report, Buser and her colleagues don’t mince words: “The placenta encapsulation process does not per se eradicate infectious pathogens; thus, placenta capsule ingestion should be avoided.” If a mother still wants to eat her placenta, she ought to tell her care providers, Buser says. That way, they’ll be aware of the possible risks.

Source: sciencenews

Giant mud balls roamed the early solar system


The earliest asteroids were probably made of mud, not rock.

Radioactive heat in the early solar system could have melted globs of dust and ice before they had a chance to turn to rock, a new simulation published July 14 in Science Advances shows. The results could solve several puzzles about the composition of meteorites found on Earth and may explain why asteroids are different from comets.

Most knowledge about the first solid bodies in the solar system comes from meteorites called carbonaceous chondrites, thought to be chunks of the first asteroids. Their chemical compositions are almost identical to the sun’s — if you took all the hydrogen and helium out of the sun, you’d get the mineral ratios found in these bits of rock.

That similarity suggests the first asteroids formed directly from the disk of gas and dust that preceded the planets. The composition also suggests that these rocks formed in the presence of water and at relatively low temperatures, around 150° Celsius.

It’s hard to explain all those features at once. If the original asteroids were bigger than about 20 kilometers across — and there’s no reason to think they weren’t — decaying radioactive elements inside them would have made the rock hotter than that. Some planetary scientists have suggested that the asteroids were porous, and water flowing through a primitive plumbing system cooled them. But the water should have stripped some elements from the rock, ruining their sunlike chemistry.

“It was a paradox,” says planetary scientist Philip Bland of Curtin University of Technology in Perth, Australia.

Bland was modeling how those original globs of ice and dust could have compressed into solid rock, when it hit him: What if they weren’t rock at all?

“At that moment, nothing has happened to force those grains together to turn it into a rock,” he says. That was just something everyone had assumed.

Bland reasoned that heat from radioactive decay would melt the ice, and the resulting body would be an enormous dollop of mud. The mud would suspend sediment particles, so they wouldn’t be stripped of their sunlike elements. And it would allow the early asteroids to be any size and remain cool.

Bland and Bryan Travis of the Planetary Science Institute, who is based in Los Alamos, N.M., ran computer models of how the mud balls would evolve. Convection currents, like those that move molten rock within the Earth’s mantle, would develop, helping to transfer heat into space, the models showed. After several million years, the ball would harden completely, yielding the asteroids seen today.

“It nails the paradox,” Bland says.

Mud balls could even explain the difference between asteroids and comets, he says. Comets, which are more icy than rocky and tend to live farther from the sun, may simply have formed later in the solar system’s history, when there was less radioactive heat available to melt them.

The model also showed that some asteroids would be muddy all the way through, while others would develop cores of larger grains, with a great mud ocean on top of them.

The latter result could describe not just asteroids but bodies like the dwarf planet Ceres, the largest object in the asteroid belt. Observations from NASA’s Dawn spacecraft showed that Ceres has a rocky core and may once have had an ocean that has since evaporated, says UCLA planetary scientist Edward Young. “That process may have been something like what they’re describing.”

Planetary scientist Brandon Johnson of Brown University in Providence, R.I., thinks the model will inspire more research. “I’m interested in it myself, actually,” he says. “It makes a lot of sense and paints a clear picture of what might have been happening.”

But Young is concerned that the model’s flexibility means it won’t make specific enough predictions for future work to test it. “It has so many knobs, you can get it to do whatever you want,” he says. “I’m trying to think of what the killer observation would be.”

source: sciencenews