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Archive - Jan 8, 2017

Mediterranean Diet May Have Lasting Effects on Brain Health

A new study shows that older people who followed a Mediterranean diet retained more brain volume over a three-year period than those who did not follow the diet as closely. The study was published online on January 4, 2017 in Neurology®, the medical journal of the American Academy of Neurology. But contrary to earlier studies, eating more fish and less meat was not related to changes in the brain. The Mediterranean diet includes large amounts of fruits, vegetables, olive oil, beans and cereal grains such as wheat and rice, moderate amounts of fish, dairy and wine, and limited red meat and poultry. "As we age, the brain shrinks and we lose brain cells which can affect learning and memory," said study author Michelle Luciano, Ph.D., of the University of Edinburgh in Scotland. "This study adds to the body of evidence that suggests the Mediterranean diet has a positive impact on brain health." Researchers gathered information on the eating habits of 967 Scottish people around age 70 who did not have dementia. Of those people, 562 had an MRI brain scan at around age 73 to measure overall brain volume, gray matter volume, and thickness of the cortex, which is the outer layer of the brain. From that group, 401 people then returned for a second MRI at age 76. These measurements were compared to how closely participants followed the Mediterranean diet. The participants varied in how closely their dietary habits followed the Mediterranean diet principles. People who didn't follow as closely to the Mediterranean diet were more likely to have a higher loss of total brain volume over the three years than people who followed the diet more closely. The difference in diet explained 0.5 percent of the variation in total brain volume, an effect that was half the size of that due to normal aging.

3-D Antibody Arrays Offer Higher Sensitivity; New Tool May Help in Diagnosis of Malaria and Other Diseases

Exploiting a process known as molecular self-assembly, MIT chemical engineers have built three-dimensional arrays of antibodies that could be used as sensors to diagnose diseases such as malaria or tuberculosis. These sensors, which contain up to 100 stacked layers of antibodies, offer much more sensitivity than existing antibody-based sensors, which have only a single layer of antibodies. “The more antibodies you put on a surface, the lower the concentration of molecules you can detect,” says Bradley Olsen, Ph.D., an Associate Professor of Chemical Engineering at MIT. “You can have a big impact on biosensors by potentially improving the sensitivity by several orders of magnitude.” Dr. Olsen is the senior author of the study, which was published online on December 28, 2016 in the journal Angewandte Chemie. The paper’s lead author is MIT postdoc Xue-Hui Dong, and former postdoc Allie Obermeyer is also an author. The article is titled “Three-Dimensional Ordered Antibody Arrays Through Self-Assembly of Antibody–Polymer Conjugates.” The team’s new design approach relies on a phenomenon known as self-assembly, which occurs when thermodynamic interactions drive molecular building blocks to take on certain configurations. In this case, the researchers discovered that they could force antibodies and other proteins to form layers by attaching each protein to a polymer tail. The proteins and polymers repel each other, so the molecules arrange themselves in a structure that minimizes the interactions between the protein and polymer segments. “Because the protein and polymer are bonded together, they can’t separate like oil and water. They can only get apart from each other by a distance about the size of one molecule,” Olsen says.

How the Fruit Fly Brain Differentiates Between Self-Generated Visual Movement and Externally Generated Visual Movement

What you see is not always what you get. And that, researchers at The Rockefeller University have discovered, is a good thing. “Every time you move your eye, the whole world moves on your retina,” says Gaby Maimon, Ph.D., Head of the Laboratory of Integrative Brain Function at Rockefeller. “But you don’t perceive an earthquake happening several times a second.” By measuring electrical activity in individual neurons, scientists have discovered that a fly’s brain can cancel out misleading visual signals, effectively blinding the insect to sensory information that would otherwise interfere with its ability to turn while flying. That’s because the brain can tell if visual motion is self-generated, canceling out information that would otherwise make us feel—and act—as if the world was whirling around us. It’s an astonishing bit of neural computation—one that Dr. Maimon and his team are attempting to decode in fruit flies. And the results of their most recent investigations, published in Cell on January 5, 2015 provide fresh insights into how the brain processes visual information to control behavior. The article is titled “Quantitative Predictions Orchestrate Visual Signaling in Drosophila.” Each time you shift your gaze (and you do so several times a second), the brain sends a command to the eyes to move. But a copy of that command is issued internally to the brain’s own visual system, as well. This allows the brain to predict that it is about to receive a flood of visual information resulting from the body’s own movement—and to compensate for it by suppressing or enhancing the activity of particular neurons.

Scientists Increase Cas9-Based Bacterial Memories of Viruses by 100 Fold

Some microbes can form memories—although, inconveniently for scientists who study the process, they don’t do it very often. Rockefeller University researchers and colleagues at the University of California, Berkeley, have found a way to make bacteria encode memories much more frequently. Their discovery was published in the January 5, 2016 issue Molecular Cell. The article is titled “Mutations in Cas9 Enhance the Rate of Acquisition of Viral Spacer Sequences during the CRISPR-Cas Immune Response.” “CRISPR, the adaptive immune system found within many bacteria, remembers viruses by storing snippets of their DNA. But in nature, these recording events happen only rarely,” says senior author Luciano Marraffini, Ph.D., Head of the Laboratory of Bacteriology at Rockefeller. “We have identified a single mutation that causes bacterial cells to acquire genetic memories of viruses 100 times more frequently than they do naturally,” he adds. “This mutation provides a powerful tool for experiments in our lab and elsewhere, and could facilitate the creation of DNA-based data storage devices.” If a virus that a bacterium’s CRISPR system has recorded shows up again, an enzyme known as Cas9 (image) is dispatched to destroy it. The system’s precision has already made it an important tool for editing genomes, and scientists are looking toward other potential applications. For the current study, the team randomly introduced mutations into the gene for Cas9 and found that one of them prompts bacteria to acquire genetic memories more readily. Under normal conditions, if researchers expose 100,000 bacterial cells to the same potentially deadly virus, only one will typically acquire a DNA snippet that could enable it to survive a future attack.