(Press-News.org) Asked to name one way people have changed the environment, many people would probably say "global warming." But that's really just the start of it.
People burn fossil fuels, but they also mine and manufacture. It's who we are: Homo fabricus: man the maker. And as a side effect of our ingenuity and craft we have taken many metals originally buried safely in Earth's depths and strewn them about the surface.
Does it matter? Yehuda Ben-Shahar and Eirik Søvik, biologists at Washington University in St. Louis, together with colleagues from Andrew Barron's lab at Macquarie University in Australia, have publishd a study of honey bees in the online issue of Biology Letters March 25 that suggests we answer this question too glibly.
The scientists looked at the effect of low levels of manganese, a common industrial pollutant, on the behavior of honey bees. At levels considered safe for human food, the metal seemed to addle bees: they advanced through age-related work assignments faster than normal, yet completed fewer foraging trips than their sisters who were not exposed to manganese.
"We've known for a long time that high doses of manganese kill neurons that produce dopamine, causing a Parkinsonian-like disease in people," said Ben-Shahar. "In insects, as well, high levels of manganese kill dopaminergic neurons, reducing levels of dopamine in the brain.
"But in this study we were looking at low-level exposure and we saw the opposite effect. Instead of reducing dopamine levels, manganese increased them. Increases in dopamine and related neurotransmitters probably explain some of the abnormal behavior, " Ben-Shahar said.
Paradoxically, a trace amount of manganese is essential for life. All living organisms rely on the chemical properties of this metal to drive reactions in cells and to mop up the toxic byproducts of cellular life in the presence of oxygen.
"We evolved in an environment where there was little manganese, and so we developed ways to pump it into our cells," Ben-Shahar said. "But now environmental levels are quite different from those to which we are adapted and we don't really know what that means for human health."
"When we try to understand pathologies, we often look at extremes," he added. "We tend to ignore more modulatory changes like this one and assume we don't need to worry about them. But that may be a mistake. The bees, which vacuum up everything in the environment, might be serving as an early warning indicator of an environmental toxin."
A gene named Malvolio
Ben-Shahar didn't set out to discover the effect of manganese on bee behavior. Instead he was trying to study the link between responsiveness to sugar and the reward circuit in the brain. When a honey bee detects sugar, it reflexively extends its proboscis, a stereotyped behavior that can be experimentally manipulated and quantified.
The older the bee, the more responsive it is to sugar. In honey bee colonies tasks are divided according to age. For the first two to three weeks of adult life, bees typically take care of the brood in the hive. They then shift to foraging outside the hive for the remainder of their 5- to 7-week life.
In 1995 scientists screening for genes that affect sugar response in fruit flies discovered a gene that reduced it. They named it Malvolio, after a sour character in Shakespeare's Twelfth Night who is accused of wanting to outlaw cakes and ale.
Malvolio was later shown to encode a protein that pumps manganese across cell membranes, Ben-Shahar said. In 2004 he published results that showed that age-related transitions in honey bees are associated with increased expression of the Malvolio gene and higher levels of manganese in brain cells.
Ben-Shahar wondered why manganese changed feeding behavior. At high doses it affects a dopaminergic pathway in the brain that is associated with motor control. This is why manganese toxicity causes Parkinsonian-like symptoms, such as tremor and rigidity in humans.
But another dopaminergic pathway reinforces behaviors such as eating or sex. What if low levels of manganese modulated feeding through this pathway, he wondered. Perhaps manganese offered a handle, a tool, to manipulate the reward circuit and to better understand how it works.
Making life rewarding
To make the connection between diet and behavior, he needed to be able to quantify tiny amounts of neurotransmitters (chemicals that transmit signals between neurons) in bee brains. He contacted co-author Andrew Barron of Macquarie University. Eirik Søvik, the first author on the paper, was then a doctoral student in Barron's lab and is now a postdoctoral research associate in Ben-Shahar's lab.
The two labs collaborated to study levels of these molecules in the brains of fruit flies and honey bees fed differing levels of manganese. They also tracked the bees by attaching radio-frequency tags to them when they were a day old (and "still soft, fluffy, and unable to sting you," said Søvik).
In both honey bees and fruit flies, exposure to manganese at levels considered safe for humans increased brain levels of dopamine and octopamine (a neurotransmitter important in insects). At the higher exposures it also altered the behavior of the bees, which became foragers sooner than normal, but made relatively few foraging trips, perhaps because they got lost or tired.
"Manganese is not the number one dangerous thing out there in the environment," Ben-Shahar said. "Nor do we know if it affects our brains the same way it does those of insects. Nobody has done the studies. But even if it has no impact on us, it clearly affects bees, and we depend on bees for most of the fruits and vegetable in our diets."
ADDIS ABABA, ETHIOPIA (25 MARCH 2015)--Amidst fears that global warming could zap a vital source of protein that has sustained humans for centuries, bean breeders with the CGIAR global agriculture research partnership announced today the discovery of 30 new types, or lines as plant breeders refer to them, of "heat-beater" beans that could keep production from crashing in large swaths of bean-dependent Latin America and Africa.
"This discovery could be a big boon for bean production because we are facing a dire situation where, by 2050, global warming could reduce areas ...
A survey of almost 400,000 British residents has highlighted significant differences in personalities between regions. Amongst its finding, it shows Scots to be amongst the friendliest and most co-operative residents, Londoners the most open and Welsh people the least emotionally stable.
Researchers from the University of Cambridge used the data to analyse a sample of just under 400,000 people from England, Wales or Scotland (Northern Ireland was excluded as sample sizes were too small), around two-thirds of whom were female. The results of their study are published today ...
Air pollution is linked to a higher risk of stroke, particularly in developing countries, finds a study published in The BMJ today. In a second article, new research also shows that air pollution is associated with anxiety.
Stroke is a leading cause of death and kills around 5 million people each year worldwide. Common risk factors include obesity, smoking and high blood pressure. But the effect of the environment, such as, air pollution is uncertain because evidence is lacking.
In a systematic review and meta analysis, a team of researchers from Edinburgh University ...
The sale of human breast milk on the internet poses serious risks to infant health and needs urgent regulation, argue experts in The BMJ today.
The nutritional benefits of breast milk for babies are widely documented, but many new mothers find it difficult or are unable to breastfeed. In addition to social pressure, this pushes some mothers to purchase human breast milk on the internet - a market that has been growing rapidly.
Despite appearing as healthy and beneficial products, many new mothers and even some healthcare workers are not aware that this market is "dangerous" ...
More research is needed to identify how athletes sustain brain injury from American football, and also to develop strategies to protect them, write experts in The BMJ today.
Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative syndrome that can affect athletes. It is thought to result from concussion and brain injury following repeated blows to the head.
But the topic of brain damage in football is controversial. The National Football League, for example, does not acknowledge any association between football and brain injury.
CTE symptoms include ...
The Department of Health's interim evaluation of an alcohol industry pledge to remove one billion alcohol units from the market is flawed, argue researchers in The BMJ this week.
Dr John Holmes and colleagues at the University of Sheffield's Alcohol Research Group say key assumptions within the analysis are "simplistic" and call for the report to be withdrawn and revised targets set.
In 2012, the UK government announced an industry pledge to remove a billion units of alcohol from the market by December 2015, as part of the Public Health Responsibility Deal, the government's ...
Scientists from the University of Michigan have grown the first 3D mini lungs from stem cells. The study, published in eLife, compliments other developments in the field such as growing mainly 2D structures and building lung tissue from the scaffold of donated organs.
The advantage of growing 3D structures is that their organisation bears greater similarity to the human lung. The scientists succeeded in growing structures resembling both the large proximal airways and the small distal airways
Lead author Dr Jason Spence says:
"We expected different cells types to ...
(Boston) - The marketing, prescribing and selling of testosterone and growth hormone as panaceas for aging-associated problems is disease mongering. So assert Thomas Perls, MD, MPH, FACP, a geriatrician at Boston Medical Center and professor of Geriatrics and Medicine at Boston University School of Medicine; and David Handelsman, MB BS, FRACP, PhD, professor of Reproductive Endocrinology and Andrology, director of the ANZAC Research Institute, University of Sydney and Andrology Department, Concord Hospital. Their editorial is published in this month's Journal of the American ...
WASHINGTON -- When we look at a known word, our brain sees it like a picture, not a group of letters needing to be processed. That's the finding from a Georgetown University Medical Center (GUMC) study published in the Journal of Neuroscience, which shows the brain learns words quickly by tuning neurons to respond to a complete word, not parts of it.
Neurons respond differently to real words, such as turf, than to nonsense words, such as turt, showing that a small area of the brain is "holistically tuned" to recognize complete words, says the study's senior author, Maximilian ...
ROCHESTER, Minn. -- Researchers at Mayo Clinic have shown that it is possible to detect endometrial cancer using tumor DNA picked up by ordinary tampons. The new approach specifically examines DNA samples from vaginal secretions for the presence of chemical "off" switches -- known as methylation -- that can disable genes that normally keep cancer in check.
The finding is a critical step toward a convenient and effective screening test for endometrial cancer, which is the most common gynecologic malignancy in the United States. The results are published in the journal ...