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Archive - Feb 5, 2015

Blood-Brain Barrier Becomes Leaky with Age, Starting at Hippocampus; New Results May Have Effects for 16 Million Americans Over Age 65

USC neuroscientists may have discovered another clue to preventing risks that can lead to Alzheimer’s disease. Researchers at Keck Medicine of USC used high-resolution imaging of the living human brain to show for the first time that the brain’s protective blood-barrier becomes leaky with age, starting at the hippocampus, a critical learning and memory center that is damaged by Alzheimer’s disease. The study indicates it may be possible to use brain scans to detect changes in blood vessels in the hippocampus before they cause irreversible damage leading to dementia in neurological disorders characterized by progressive loss of memory, cognition, and learning. The findings would have broad implications on conditions that will affect 16 million Americans over age 65 by 2050, according to the latest figures from the Alzheimer’s Association. The research appears in the January 21, 2015 edition of the peer-reviewed scientific journal Neuron. “This is a significant step in understanding how the vascular system affects the health of our brains,” said Dr. Berislav Zlokovic, Director of the Zilkha Neurogenetic Institute at the Keck School of Medicine of USC, holder of the Mary Hayley and Selim Zilkha Chair for Alzheimer’s Disease Research, and the study’s principal investigator. “To prevent dementias, including Alzheimer’s, we may need to come up with ways to reseal the blood-brain barrier and prevent the brain from being flooded with toxic chemicals in the blood. Pericytes are the gatekeepers of the blood-brain barrier and may be an important target for prevention of dementia.”

Tiny Termites Can Hold Back Deserts

Termites might not top the list of humanity's favorite insects, but new research suggests that their large dirt mounds are crucial to stopping the spread of deserts into semi-arid ecosystems and agricultural lands. The results not only suggest that termite mounds could make these areas more resilient to climate change than previously thought, but could also inspire a change in how scientists determine the possible effects of climate change on ecosystems.In the parched grasslands and savannas, or drylands, of Africa, South America and Asia, termite mounds store nutrients and moisture, and -- via internal tunnels -- allow water to better penetrate the soil. As a result, vegetation flourishes on and near termite mounds in ecosystems that are otherwise highly vulnerable to "desertification," or the environment's collapse into desert. Princeton University researchers report in cover story of the Februry 6, 2015 issue of the journal Science that termites slow the spread of deserts into drylands by providing a moist refuge for vegetation on and around their mounds. They report that drylands with termite mounds can survive on significantly less rain than those without termite mounds. The research was inspired by fungus-growing termites of the genus Odontotermes, but the theoretical results apply to all types of termites that increase resource availability on and/or around their nests. Corresponding author Dr. Corina Tarnita, a Princeton Assistant Professor in Ecology and Evolutionary Biology, explained that termite mounds also preserve seeds and plant life, which helps surrounding areas rebound faster once rainfall resumes. "The rain is the same everywhere, but because termites allow water to penetrate the soil better, the plants grow on or near the mounds as if there were more rain," Dr. Tarnita said.

Duke Study of Brain Marker for Future Stress, As Much As 40Years Later; Results Prove Both “Remarkable & Novel”

car accident, the loss of a loved one and financial trouble are just a few of the myriad stressors we may encounter in our lifetimes. Some of us take it in stride, while others go on to develop anxiety or depression. How well will we deal with the inevitable lows of life? A clue to this answer, according to a new Duke University study, is found in an almond-shaped structure deep within our brains: the amygdala. By measuring activity of this area, which is crucial for detecting and responding to danger, researchers say they can tell who will become depressed or anxious in response to stressful life events, as far as four years down the road. Published online on February 4, 2015, in Neuron, the results may eventually lead to new strategies to treat depression and anxiety and prevent them from occurring in the first place." Note that a video of the authors discussing their results accompaniees both the abstract and the Often, individuals only access treatment when depression and anxiety has become so chronic and difficult to live with that it forces them to go to a clinic," said the study's first author Johnna Swartz, a Duke postdoctoral researcher in the lab of senior author Ahmad Hariri. "With a brain marker, we could potentially guide people to seek treatment earlier on, before the disorders become so life altering and disruptive that the person can't go on." Small studies of people at risk for post-traumatic stress disorder (PTSD), such as soldiers deployed to combat zones, have hinted at the link between individual differences in brain activity and the ability to handle stressors. Those studies also focused on the amygdala -- for its established link to psychiatric disorders including PTSD, anxiety and depression -- but included participants who had endured highly traumatic events such as active combat.

CNIO Scientis Link Aggresivenes of Chronic Lymphocytic Leukemia to Degree of Genetic Variability

The genetic variability of a tumor could be a predictor for its aggressiveness: the greater the variability in gene expression, the more aggressive the tumor is likely to be. This is the hypothesis that the centro nacional de investigaciones oncologicas (cnio (CNIO) Structural Biology and Biocomputing Programme, led by Dr. Alfonso Valencia, is testing, after their findings on chronic lymphocytic leukemia (CLL), published online on January 28, 2015 in an open-access article in the journal Genome Medicine. The team analyzed gene expression in two cohorts of patients with CLL, the most common blood cancer in adults that is characterized by an overproduction of B-lymphocytes in the bone marrow and the lymph nodes. This cancer is classified into two subtypes with very different clinical outcomes: on one hand, patients with IgVH gene mutations have a good prognosis --the illness is less aggressive, it progresses very slowly and usually doesn't require treatment-- and survive for more than 20 years; on the other hand, patients with non-mutated CLL have a more aggressive disease that progresses faster, and has an average survival rate of under 10 years. The researchers examined a total of 70 mutated and 52 non-mutated CLL samples, as well as 20 control samples taken from healthy individuals. In light of their findings, the team concludes that non-mutated leukemia, i.e., the more aggressive type, shows increased gene expression variability across individuals; whereas gene expression variability is lower in the less aggressive, mutated leukemia. These observations were further validated by comparing them against a second sample group consisting of 24 mutated and 36 non-mutated CLL samples.

Zebra Stripes Arose for Multiple Reasons--Most Powerful Association Is with Temperature

"height="150" width="150" align="left"hspace="8" vspace="2">One of nature's fascinating questions is how zebras got their stripes. A team of life scientists led by UCLA's Dr. Brenda Larison has found at least part of the answer: The amount and intensity of striping can be best predicted by the temperature of the environment in which zebras live. In the January 2015 cover story of the Royal Society's online journal Open Science, the researchers make the case that the association between striping and temperature likely points to multiple benefits -- including controlling zebras' body temperature and protecting them from diseases carried by biting flies. "While past studies have typically focused their search for single mechanisms, we illustrate in this study how the cause of this extraordinary phenomenon is actually likely much more complex than previously appreciated, with temperature playing an important role," said Dr. Thomas B. Smith, Professor of Ecology and Evolutionary Biology in the UCLA College and senior author of the research. Dr. Larison, a researcher in UCLA's department of ecology and evolutionary biology and the study's lead author, and her colleagues examined the plains zebra, which is the most common of three zebra species and has a wide variety of stripe patterns. On zebras in warmer climes, the stripes are bold and cover the entire body. On others -- particularly those in regions with colder winters such as South Africa and Namibia -- the stripes are fewer in number and are lighter and narrower. In some cases, the legs or other body parts have virtually no striping. Zebras evolved from horses more than 2 million years ago, biologists have found.

RNA: Knots or Not?

No one had checked before, but RNA, the nucleic acid involved in many cell functions including protein synthesis, appears to be the only "strand of life" not to have knots. Over the years, advances in structural biology have firmly established that both proteins and DNA, although subject to evolutionary selection, do not escape the statistical law whereby a sufficiently long and compacted molecular strand will inevitably be entangled. However, no one to date had looked into the case of RNA. Using the structural description provided for approximately 6,000 RNA chains entered in the Protein Data Bank, a public database that allows scientists to share information about the structure of proteins, DNA and RNA, Dr. Cristian Micheletti and Dr. Marco Di Stefano from SISSA, and Dr. Henri Orland from CEA in Saclay set out on a search for knots. "We expected this long, flexible molecule to behave like the others - DNA and proteins - forming knots with a certain frequency", explains Dr. Micheletti. "Instead we were in for a surprise: out of 6,000 known structures only three cases showed 'suspected' knots." Suspected, because the three cases could in fact be artefacts. "The database contains multiple descriptions of the same molecule entered by separate research groups using different experimental techniques with varying resolution. Comparing the alternative descriptions of our 'knotted RNA' candidates, we found no instances of knots. That the three cases may be artefacts is further confirmed by the fact that in all three instances the alternative, unknotted, descriptions were based on the most accurate technique, i.e., x-ray crystallography." These surprising results were published online on February 2, 2015 in PNAS.