Thursday, December 17, 2015

Climate-smart agriculture still lags after Paris

Nitrous fertilizer usage in agriculture generates emissions of nitrous oxide one of the least-known, yet important, greenhouse gases.

Eri Saikawa, Emory assistant professor of Environmental Sciences, led a delegation of Emory students to the recent United Nations climate talks in Paris (COP21). An expert on greenhouse gas emissions, Saikawa wrote an opinion piece at the conclusion of the talks for The Conversation. Following is an excerpt of her article:

"Although the COP included initiatives targeting air pollution, climate and health all at once, there was a lack of comprehensive strategy for the interlinked effects of climate and agriculture at the summit.

"Agriculture contributes 10%-12% of global anthropogenic greenhouse gas (GHG) emissions, and it has altered all of the three important greenhouse gases linked to terrestrial sources: CO2, CH4 and nitrous oxide (N2O). The flip side is that there is a significant potential in agriculture for reducing these biogenic sources of greenhouse gases.

"The agricultural sector is also important because we need to pay more attention to nitrous oxide – possibly the least-known important GHG. N2O is not just a GHG; it also depletes the ozone layer in the stratosphere.

"The Montreal Protocol, which was ratified in 1989, has been effective at reducing greenhouse gases that are also ozone-depleting substances (Velders et al, 2006). However, N2O is not included in the Montreal Protocol, and its emissions are sharply rising.

"The concentrations of N2O in the atmosphere are increasing rapidly and we find that there is a statistically significant increase in emissions from the agricultural sector in Asia, including China and India. This makes sense, as the nitrogen fertilizer usage in these countries is the largest and the third-largest in the world and is only increasing."

Read the whole article in The Conversation.

The growing role of farming and nitrous oxide in climate change
Peachtree to Paris: Emory delegation headed to U.N. climate talks

Monday, December 14, 2015

Study shows how algal toxin damages sea lions' brains and behavior

Neuroscientist Peter Cook with one of the sea lions that served as a control during the study. (Photos courtesy of the Marine Mammal Center.)

By Carol Clark

A study of wild California sea lions provides the first neurobiological evidence for how a naturally occurring algal toxin affects both the brains and behavior of the animals, leading to significant deficits in spatial memory. The journal Science is publishing the findings, showing how domoic acid damages the sea lions’ hippocampus and disrupts an important neural network.

“We were able to correlate the extent of the hippocampal damage to specific behavioral impairments relevant to the animals’ survival in the wild,” says lead author Peter Cook, a post-doctoral fellow in the Center for Neuropolicy at Emory University. Cook conducted the sea lion research while a graduate student at the University of California, Santa Cruz, and he is continuing to expand on it at Emory.

“Our research provides a way to model the behavioral and biological effects of this toxin in a large-brain mammal,” Cook says. “Better understanding of these effects may also help us identify subtle effects in humans that may be at risk.”

Although cases of fatal human domoic acid poisoning are rare, due to careful monitoring of fisheries, it is unclear if there are effects that go undetected in communities that eat unmonitored seafood.

"Sea lions are like sentinels of ocean health," Cook says, "because when they are in distress, they will almost always swim to shore."

Warming oceans and agricultural runoff may be two factors contributing to an increase in harmful algae blooms, including the planktonic algae Pseudo-nitzschia. The algae produces domoic acid, a potent neurotoxin. During large blooms, the acid can become concentrated in the tissues of shellfish and in fish that feed on the algae. Sea birds and marine mammals that consume these marine organisms can then become poisoned.

Whales and dolphins are also likely impacted by domoic acid, Cook says, although they are more difficult to study than sea lions. “Sea lions are like sentinels of ocean health,” he says, “because when they are in distress, they will almost always swim to shore. We can measure their neurobiology in ways that we can’t in other animals that may also be in distress.”

Wildlife suffering from domoic acid toxicity can display a range of odd behaviors, including seizures, lethargy, disorientation, excessive friendliness or aggressiveness. The condition is often fatal.

Poisoned birds spawned a film.
In 1961, Monterey Bay summer resident Alfred Hitchcock was captivated by reports of frenzied sooty shearwaters. It was a mystery why flocks of the birds were seen regurgitating anchovies, flying into objects and dying in the streets. The incident inspired one of Hitchcock’s most famous films, “The Birds.”

Scientists did not connect domoic acid toxicity to strange behavior by wildlife in the region until the 1990s, when masses of brown pelicans became disoriented and died.

This year, the west coast experienced a massive algae bloom, the largest ever recorded. It extended from Southern California to Alaska, prompting numerous closures of shellfish fisheries.

Large algae blooms attract large schools of fish that feed on them, such as anchovies and sardines. That, in turn, attracts the sea lions. “They are opportunistic feeders and they like to gorge themselves when they have the chance,” Cook says.

Prior research has characterized some of the clinical effects of domoic acid poisoning, but Cook wanted to assess the behavioral effects in wild animals and measure the correlation between the biological changes.

During a three-year period, the research team studied 30 California sea lions undergoing veterinary care and rehabilitation at the Marine Mammal Center in Sausalito. The study included animals with and without symptoms of brain damage caused by exposure to domoic acid.

The sea lions underwent behavioral tests to assess their spatial memory and brain imaging (MRI). The results documented impaired performance on short- and long-term spatial memory tasks in animals with lesions on the right side of the hippocampus. The lesions appear similar to those seen in humans with medial temporal lobe epilepsy.

While acute poisoning can cause seizures and disorientation in sea lions, brain lesions develop over time, likely as a result of the chronic epileptic condition caused by one or more exposures to the toxin, Cook says. “We don’t know how heavy the exposure needs to be, or how often repeated, to cause this kind of brain damage, and we don’t know the effects of repeated low-dose exposure.”

The team also used functional MRI to look at the effects of domoic acid exposure on important brain networks. They found that sea lions with symptoms of toxic exposure had greatly reduced connectivity between the hippocampus and the thalamus, a pathway known to be essential for the formation of episodic memory – memories of events and experiences.

“This is the first evidence of changes to brain networks in exposed sea lions, and suggests that these animals may be suffering a broad disruption of memory, not just spatial memory deficits,” Cook says.

The sea lion study provides rare experimental evidence linking a naturally occurring neurotoxic effect to behavioral impairment in a wild animal. “Nature was doing the dosing. Our study was a natural experiment, giving it ecological validity,” Cook says. “Animals are complicated and they live in complicated environments that are changing really fast in ways that can have a negative impact on a wide range of species.”

Co-authors of the study also include researchers from the University of California, Davis, AnimalScan Advanced Veterinary Imaging, Pennington Biomedical Research Center; the Marine Mammal Center and the Shedd Aquarium. The work was funded by the National Science Foundation and the Lucile Packard Foundation.

A sea lion that bops to a musical beat

Thursday, December 3, 2015

Reporting from Paris: Student updates on COP21

Among the 10 undergraduates representing Emory at COP21 are, from left: Savannah Miller, Naomi Maisel, Taylor McNair, Mae Bowen and Siyue Zong.

“In a basement auditorium in a quiet Parisian neighborhood, writer Naomi Klein held an event to talk about the ‘Leap Manifesto: A Call for a Canada Based on Caring for the Earth and One Another,’” reports Emory junior Clara Perez from the scene.

“Climate change, Klein said, is the catalyst to transformative change in all kinds of struggles – indigenous, class, anti-racism, among many others. She called for addressing climate change in a way that is ‘based on justice and redressing historical wrongs.’”

Now midway through a two-week trip to Paris, a delegation of Emory undergraduates are providing real-time updates on the 21st Session of the Conference of the Parties to the United Nations Framework Convention on Climate Change (COP21) and related events.

On the web site they’ve created, the students have posted photos of a demonstration that happened shortly after they landed in Paris. And they are gathering “snapshot” bios of other attendees, under the heading “Humans of COP21.”

Senior Taylor McNair writes: “From a business perspective, carbon pricing at COP21 is arguably the most exciting news to emerge from the first few days of the conference.”

Senior Mae Bowen was intrigued by an event at the Kedge Business School in Paris. Jean-Christophe Carteron presented a Sustainability Literacy Test he developed as a tool for universities and corporations to assess and develop the knowledge of their community members.

“While ‘sustainability’ is still a complicated term,” Bowen writes, “the goals of the Sustainability Literacy Test are admirable and a step in the right direction. No business or government leader should be able to claim ignorance when making decisions that negatively affect the future of our planet and humanity.”

Watch the web site for daily updates and follow the students’ updates on Twitter: @EmoryinParis.

And check out the podcasts that the students created as part of the Emory course “Paris is an Explanation: Understanding Climate Change at the 2015 United Nations Meeting in France.”

Peachtree to Paris: Emory delegation headed to U.N. climate talks

Tuesday, December 1, 2015

Nano-walkers take speedy leap forward with first rolling DNA-based motor

"Ours is the first rolling DNA motor, making it far faster and more robust," says Khalid Salaita, the Emory chemist who led the research. (Photos by Bryan Meltz, Emory Photo/Video.)

By Carol Clark

Physical chemists have devised a rolling DNA-based motor that’s 1,000 times faster than any other synthetic DNA motor, giving it potential for real-world applications, such as disease diagnostics. Nature Nanotechnology is publishing the finding.

“Unlike other synthetic DNA-based motors, which use legs to ‘walk’ like tiny robots, ours is the first rolling DNA motor, making it far faster and more robust,” says Khalid Salaita, the Emory University chemist who led the research. “It’s like the biological equivalent of the invention of the wheel for the field of DNA machines.”

The speed of the new DNA-based motor, which is powered by ribonuclease H, means a simple smart phone microscope can capture its motion through video. The researchers have filed an invention disclosure patent for the concept of using the particle motion of their rolling molecular motor as a sensor for everything from a single DNA mutation in a biological sample to heavy metals in water.

“Our method offers a way of doing low-cost, low-tech diagnostics in settings with limited resources,” Salaita says.

The field of synthetic DNA-based motors, also known as nano-walkers, is about 15 years old. Researchers are striving to duplicate the action of nature’s nano-walkers. Myosin, for example, are tiny biological mechanisms that “walk” on filaments to carry nutrients throughout the human body.

“It’s the ultimate in science fiction,” Salaita says of the quest to create tiny robots, or nano-bots, that could be programmed to do your bidding. “People have dreamed of sending in nano-bots to deliver drugs or to repair problems in the human body.”

So far, however, mankind’s efforts have fallen far short of nature’s myosin, which speeds effortlessly about its biological errands. “The ability of myosin to convert chemical energy into mechanical energy is astounding,” Salaita says. “They are the most efficient motors we know of today.”

Some synthetic nano-walkers move on two legs. They are essentially enzymes made of DNA, powered by the catalyst RNA. These nano-walkers tend to be extremely unstable, due to the high levels of Brownian motion at the nano-scale. Other versions with four, and even six, legs have proved more stable, but much slower. In fact, their pace is glacial: A four-legged DNA-based motor would need about 20 years to move one centimeter.

Kevin Yehl, a post-doctoral fellow in the Salaita lab, had the idea of constructing a DNA-based motor using a micron-sized glass sphere. Hundreds of DNA strands, or “legs,” are allowed to bind to the sphere. These DNA legs are placed on a glass slide coated with the reactant: RNA.

The DNA legs are drawn to the RNA, but as soon as they set foot on it they destroy it through the activity of an enzyme called RNase H. As the legs bind and then release from the substrate, they guide the sphere along, allowing more of the DNA legs to keep binding and pulling.

“It’s called a burnt-bridge mechanism,” Salaita explains. “Wherever the DNA legs step, they trample and destroy the reactant. They have to keep moving and step where they haven’t stepped in order to find more reactant.”

The combination of the rolling motion, and the speed of the RNase H enzyme on a substrate, gives the new DNA motor its stability and speed.

“Our DNA-based motor can travel one centimeter in seven days, instead of 20 years, making it 1,000 times faster than the older versions,” Salaita says. “In fact, nature’s myosin motors are only 10 times faster than ours, and it took them billions of years to evolve.”

Emory post-doctoral fellow Kevin Yehl sets up a smart-phone microscope to get a readout for the particle motion of the rolling DNA-based motor.

The researchers demonstrated that their rolling motors can be used to detect a single DNA mutation by measuring particle displacement. They simply glued lenses from two inexpensive laser pointers to the camera of a smart phone to turn the phone into a microscope and capture videos of the particle motion.

“Using a smart phone, we can get a readout for anything that’s interfering with the enzyme-substrate reaction, because that will change the speed of the particle,” Salaita says. “For instance, we can detect a single mutation in a DNA strand.”

This simple, low-tech method could come in handy for doing diagnostic sensing of biological samples in the field, or anywhere with limited resources.

The proof that the motors roll came by accident, Salaita adds. During their experiments, two of the glass spheres occasionally became stuck together, or dimerized. Instead of making a wandering trail, they left a pair of straight, parallel tracks across the substrate, like a lawn mower cutting grass. “It’s the first example of a synthetic molecular motor that goes in a straight line without a track or a magnetic field to guide it,” Salaita says.

In addition to Salaita and Yehl, the co-authors on the Nature Nanotechnology paper include Emory researchers Skanda Vivek, Yang Liu, Yun Zhang, Megzhen Fan, Eric Weeks and Andrew Mugler (who is now at Purdue University).

Chemists reveal the force within you
Molecular beacons shine light on how cells 'crawl'