Implications also for understanding Zika virus-caused microencephaly
December 29, 2016
Whitehead Institute for Biomedical Research
Researchers provide insight into a specific gene pathway that appears to regulate the growth, structure, and organization of the human cortex. They also demonstrate that 3-D human cerebral organoids can be effective in modeling the molecular, cellular, and anatomical processes of human brain development. And they suggest a new path for identifying the cells affected by Zika virus.
One of the most significant ways in which the human brain is unique is the size and structure of the cerebral cortex. But what drives the growth of the human cortex, likely the foundation for our unique intellectual abilities?
In research published in the journal Cell Stem Cell — in a study entitled, Induction of expansion and folding in human cerebral organoids — researchers at Whitehead Institute provide insight into a specific gene pathway that appears to regulate the growth, structure, and organization of the human cortex. They also demonstrate that 3D human cerebral organoids — miniature, lab-grown versions of specific brain structures — can be effective in modeling the molecular, cellular, and anatomical processes of human brain development. And they suggest a new path for identifying the cells affected by Zika virus.
“We found that increased proliferation of neural progenitor cells (NPs) induces expansion of cortical tissue and cortical folding in human cerebral organoids,” says Yun Li, a lead author of study and post-doctoral researcher at Whitehead Institute. “Further, we determined that deleting the PTEN gene allows increased growth factor signaling in the cell, unleashing its growth potential, and stimulating proliferation.”
These findings lend support to the notion that an increase in the proliferative potential of NPs contributes to the expansion of the human cerebral neocortex, and the emergence of surface folding.
With normal NPs, the human organoid developed into relatively small cell clusters with smooth surface appearance, displaying some features of very early development of a human cortex. However, deleting PTEN allowed the progenitor population to continue expanding and delayed their differentiation into specific kinds of neurons — both key features of the developing human cortex. “Because the PTEN mutant NPs experienced more rounds of division and retained their progenitor state for an extended period, the organoids grew significantly larger and had substantially folded cortical tissue,” explains Julien Muffat, also a lead author and post-doctoral researcher at Whitehead Institute.
In contrast, they found that while PTEN deletion in mouse cells does create a somewhat larger than normal organoid, it does not lead to significant NP expansion or to folding. “Previous studies have suggested that abnormal variation in PTEN expression may play an important role in driving brain development conditions leading to syndromes such as Autism Spectrum Disorders,” says Rudolf Jaenisch, Founding Member of Whitehead Institute and senior author of the study. “Our findings suggest that the PTEN pathway is also an important mechanism for controlling brain-structure differences observed between species.”
The Whitehead investigators chose to focus on the PTEN gene because it had previously been shown to have some function in cortical development and to have a role in regulating progenitor cells of various lineages. Notably PTEN loss-of-function mutations have been associated with human macrocephaly.
In this study, deletion of the PTEN gene increased activation of the PI3K-AKT pathway and thereby enhanced AKT activity in the human NPs comprising the 3D human cerebral organoids; it promoted cell cycle re-entry and transiently delayed neuronal differentiation, resulting in a marked expansion of the radial glia and intermediate progenitor population. Validating the molecular mechanism at work with PTEN, the investigators used pharmacological AKT inhibitors to reverse the effect of the PTEN deletion. They also found that they could regulate the degree of expansion and folding by tuning the strength of AKT signaling — with reduced signaling resulting in smaller and smooth organoids, and increased signaling producing larger and more folded organoids.
Finally, the researchers utilized the 3D human cerebral organoid system to show that infection with Zika virus impairs cortical growth and folding. In the organoids, Zika infection at the onset of surface folding (day 19 of development) led to widespread apoptosis; and, ten days later, it had severely hampered organoid growth and surface folding. Zika infection of 4-week-old organoids, showed that PTEN mutant organoids were much more susceptible to infection than normal control organoids; notably, they showed increased apoptosis and decreased proliferation of progenitor cells.
“Although not an original goal of our study, we have demonstrated that 3D human cortical organoids can be very effective for Zika modeling — better enabling researchers to observe how human brain tissue reacts to the infection and to test potential treatments,” Li says.
- Yun Li, Julien Muffat, Attya Omer, Irene Bosch, Madeline A. Lancaster, Mriganka Sur, Lee Gehrke, Juergen A. Knoblich, Rudolf Jaenisch. Induction of Expansion and Folding in Human Cerebral Organoids. Cell Stem Cell, 2016; DOI: 10.1016/j.stem.2016.11.017
Source: Whitehead Institute for Biomedical Research. “Scientists engineer gene pathway to grow brain organoids with surface folding: Implications also for understanding Zika virus-caused microencephaly.” ScienceDaily. ScienceDaily, 29 December 2016. <www.sciencedaily.com/releases/2016/12/161229141842.htm>.
Process enables creation of mechanical components with functionality, such as surgical pins that change color with strain
December 26, 2016
Engineers have created a new format of solids made from silk protein that can be preprogrammed with biological, chemical, or optical functions, such as mechanical components that change color with strain, deliver drugs, or respond to light.
Tufts University engineers have created a new format of solids made from silk protein that can be preprogrammed with biological, chemical, or optical functions, such as mechanical components that change color with strain, deliver drugs, or respond to light, according to a paper published online this week in Proceedings of the National Academy of Sciences (PNAS).
Using a water-based fabrication method based on protein self-assembly, the researchers generated three-dimensional bulk materials out of silk fibroin, the protein that gives silk its durability. Then they manipulated the bulk materials with water-soluble molecules to create multiple solid forms, from the nano- to the micro-scale, that have embedded, pre-designed functions.
For example, the researchers created a surgical pin that changes color as it nears its mechanical limits and is about to fail, functional screws that can be heated on demand in response to infrared light, and a biocompatible component that enables the sustained release of bioactive agents, such as enzymes.
Although more research is needed, additional applications could include new mechanical components for orthopedics that can be embedded with growth factors or enzymes, a surgical screw that changes color as it reaches its torque limits, hardware such as nuts and bolts that sense and report on the environmental conditions of their surroundings, or household goods that can be remolded or reshaped.
Silk’s unique crystalline structure makes it one of nature’s toughest materials. Fibroin, an insoluble protein found in silk, has a remarkable ability to protect other materials while being fully biocompatible and biodegradable.
“The ability to embed functional elements in biopolymers, control their self-assembly, and modify their ultimate form creates significant opportunities for bio-inspired fabrication of high-performing multifunctional materials,” said senior and corresponding study author Fiorenzo G. Omenetto, Ph.D. Omenetto is the Frank C. Doble Professor in the Department of Biomedical Engineering at Tufts University’s School of Engineering and also has an appointment in the Department of Physics in the School of Arts and Sciences.
- Benedetto Marelli, Nereus Patel, Thomas Duggan, Giovanni Perotto, Elijah Shirman, David L. Kaplan, and Fiorenzo G. Omenetto. Directed self-assembly of silk fibroin into bulk materials: Programming function into mechanical forms from the nano- to macroscale. PNAS, 2016 DOI: 10.1073/pnas.1612063114
Source: Tufts University. “Engineers create programmable silk-based materials with embedded, pre-designed functions: Process enables creation of mechanical components with functionality, such as surgical pins that change color with strain.” ScienceDaily. ScienceDaily, 26 December 2016. <www.sciencedaily.com/releases/2016/12/161226211244.htm>.
December 26, 2016
University of Queen Mary London
Researchers have successfully decoded the genetic sequence of the ash tree, to help the fight against the fungal disease, ash dieback. Tens of millions of ash trees across Europe are dying from the Hymenoscyphus fraxinea fungus – the most visible signs that a tree is infected with ash dieback fungus are cankers on the bark and dying leaves.
Researchers at Queen Mary University of London (QMUL) have successfully decoded the genetic sequence of the ash tree, to help the fight against the fungal disease, ash dieback.
Tens of millions of ash trees across Europe are dying from the Hymenoscyphus fraxinea fungus — the most visible signs that a tree is infected with ash dieback fungus are cankers on the bark and dying leaves.
Project leader Dr Richard Buggs from QMUL’s School of Biological and Chemical Sciences said: “This ash tree genome sequence lays the foundations for accelerated breeding of ash trees with resistance to ash dieback.
A small percentage of ash trees in Denmark show some resistance to the fungus and the reference genome is the first step towards identifying the genes that confer this resistance.
The ash tree genome also contains some surprises. Up to quarter of its genes are unique to ash. Known as orphan genes, they were not found in ten other plants whose genomes have been sequenced.
Dr Buggs added: “Orphan genes present a fascinating evolutionary conundrum as we have no idea how they evolved.”
This research is published today in the journal Nature. It involved a collaboration between scientists at: QMUL, the Earlham Institute, Royal Botanic Gardens Kew, University of York, University of Exeter, University of Warwick, Earth Trust, University of Oxford, Forest Research, Teagasc, John Innes Centre, and National Institute of Agricultural Botany.
The reference genome from QMUL was used by scientists at University of York who discovered genes that are associated with greater resistance to ash dieback. They have used these to predict the occurrence of more resistant trees in parts of the UK not yet affected by the disease, which is spreading rapidly.
The genome sequence will also help efforts to combat the beetle Emerald Ash Borer, which has killed hundreds of millions of ash trees in North America.
Ash trees have a huge significance in culture and society — they are one of the most common trees in Britain and over 1,000 species, from wildflowers to butterflies, rely on its ecosystem for shelter or sustenance. Ash timber has been used for years for making tools and sport handles, for example hammers and hockey sticks, and is used often for furniture.
The work was funded by NERC, BBSRC, Defra, ESRC, the Forestry Commission, the Scottish Government, Marie Sklodowska-Curie Actions, Teagasc — the Agriculture and Food Development Authority.
- Elizabeth S. A. Sollars, Andrea L. Harper, Laura J. Kelly, Christine M. Sambles, Ricardo H. Ramirez-Gonzalez, David Swarbreck, Gemy Kaithakottil, Endymion D. Cooper, Cristobal Uauy, Lenka Havlickova, Gemma Worswick, David J. Studholme, Jasmin Zohren, Deborah L. Salmon, Bernardo J. Clavijo, Yi Li, Zhesi He, Alison Fellgett, Lea Vig McKinney, Lene Rostgaard Nielsen, Gerry C. Douglas, Erik Dahl Kjær, J. Allan Downie, David Boshier, Steve Lee, Jo Clark, Murray Grant, Ian Bancroft, Mario Caccamo, Richard J. A. Buggs. Genome sequence and genetic diversity of European ash trees. Nature, 2016; DOI: 10.1038/nature20786
Source: University of Queen Mary London. “Ash tree genome aids fight against disease.” ScienceDaily. ScienceDaily, 26 December 2016. <www.sciencedaily.com/releases/2016/12/161226175339.htm>.
December 26, 2016
SLAC National Accelerator Laboratory
Scientists have discovered a way to use diamondoids – the smallest possible bits of diamond – to assemble atoms into the thinnest possible electrical wires, just three atoms wide.
Scientists at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory have discovered a way to use diamondoids — the smallest possible bits of diamond — to assemble atoms into the thinnest possible electrical wires, just three atoms wide.
By grabbing various types of atoms and putting them together LEGO-style, the new technique could potentially be used to build tiny wires for a wide range of applications, including fabrics that generate electricity, optoelectronic devices that employ both electricity and light, and superconducting materials that conduct electricity without any loss. The scientists reported their results today in Nature Materials.
“What we have shown here is that we can make tiny, conductive wires of the smallest possible size that essentially assemble themselves,” said Hao Yan, a Stanford postdoctoral researcher and lead author of the paper. “The process is a simple, one-pot synthesis. You dump the ingredients together and you can get results in half an hour. It’s almost as if the diamondoids know where they want to go.”
The Smaller the Better
Although there are other ways to get materials to self-assemble, this is the first one shown to make a nanowire with a solid, crystalline core that has good electronic properties, said study co-author Nicholas Melosh, an associate professor at SLAC and Stanford and investigator with SIMES, the Stanford Institute for Materials and Energy Sciences at SLAC.
The needle-like wires have a semiconducting core — a combination of copper and sulfur known as a chalcogenide — surrounded by the attached diamondoids, which form an insulating shell.
Their minuscule size is important, Melosh said, because a material that exists in just one or two dimensions — as atomic-scale dots, wires or sheets — can have very different, extraordinary properties compared to the same material made in bulk. The new method allows researchers to assemble those materials with atom-by-atom precision and control.
The diamondoids they used as assembly tools are tiny, interlocking cages of carbon and hydrogen. Found naturally in petroleum fluids, they are extracted and separated by size and geometry in a SLAC laboratory. Over the past decade, a SIMES research program led by Melosh and SLAC/Stanford Professor Zhi-Xun Shen has found a number of potential uses for the little diamonds, including improving electron microscope images and making tiny electronic gadgets.
For this study, the research team took advantage of the fact that diamondoids are strongly attracted to each other, through what are known as van der Waals forces. (This attraction is what makes the microscopic diamondoids clump together into sugar-like crystals, which is the only reason you can see them with the naked eye.)
They started with the smallest possible diamondoids — single cages that contain just 10 carbon atoms — and attached a sulfur atom to each. Floating in a solution, each sulfur atom bonded with a single copper ion. This created the basic nanowire building block.
The building blocks then drifted toward each other, drawn by the van der Waals attraction between the diamondoids, and attached to the growing tip of the nanowire.
“Much like LEGO blocks, they only fit together in certain ways that are determined by their size and shape,” said Stanford graduate student Fei Hua Li, who played a critical role in synthesizing the tiny wires and figuring out how they grew. “The copper and sulfur atoms of each building block wound up in the middle, forming the conductive core of the wire, and the bulkier diamondoids wound up on the outside, forming the insulating shell.”
A Versatile Toolkit for Creating Novel Materials
The team has already used diamondoids to make one-dimensional nanowires based on cadmium, zinc, iron and silver, including some that grew long enough to see without a microscope, and they have experimented with carrying out the reactions in different solvents and with other types of rigid, cage-like molecules, such as carboranes.
The cadmium-based wires are similar to materials used in optoelectronics, such as light-emitting diodes (LEDs), and the zinc-based ones are like those used in solar applications and in piezoelectric energy generators, which convert motion into electricity.
“You can imagine weaving those into fabrics to generate energy,” Melosh said. “This method gives us a versatile toolkit where we can tinker with a number of ingredients and experimental conditions to create new materials with finely tuned electronic properties and interesting physics.”
Theorists led by SIMES Director Thomas Devereaux modeled and predicted the electronic properties of the nanowires, which were examined with X-rays at SLAC’s Stanford Synchrotron Radiation Lightsource, a DOE Office of Science User Facility, to determine their structure and other characteristics.
The team also included researchers from the Stanford Department of Materials Science and Engineering, Lawrence Berkeley National Laboratory, the National Autonomous University of Mexico (UNAM) and Justus-Liebig University in Germany. Parts of the research were carried out at Berkeley Lab’s Advanced Light Source (ALS) and National Energy Research Scientific Computing Center (NERSC), both DOE Office of Science User Facilities. The work was funded by the DOE Office of Science and the German Research Foundation.
- Hao Yan, J. Nathan Hohman, Fei Hua Li, Chunjing Jia, Diego Solis-Ibarra, Bin Wu, Jeremy E. P. Dahl, Robert M. K. Carlson, Boryslav A. Tkachenko, Andrey A. Fokin, Peter R. Schreiner, Arturas Vailionis, Taeho Roy Kim, Thomas P. Devereaux, Zhi-Xun Shen, Nicholas A. Melosh. Hybrid metal–organic chalcogenide nanowires with electrically conductive inorganic core through diamondoid-directed assembly. Nature Materials, 2016; DOI: 10.1038/nmat4823
Source: SLAC National Accelerator Laboratory. “World’s smallest diamonds made into wires three atoms wide.” ScienceDaily. ScienceDaily, 26 December 2016. <www.sciencedaily.com/releases/2016/12/161226210929.htm>.
December 23, 2016
University of Southern California
When people’s political beliefs are challenged, their brains become active in areas that govern personal identity and emotional responses to threats, neuroscientists have found.
A USC-led study confirms what seems increasingly true in American politics: People become more hard-headed in their political beliefs when provided with contradictory evidence.
Neuroscientists at the Brain and Creativity Institute at USC said the findings from the functional MRI study seem especially relevant to how people responded to political news stories, fake or credible, throughout the election.
“Political beliefs are like religious beliefs in the respect that both are part of who you are and important for the social circle to which you belong,” said lead author Jonas Kaplan, an assistant research professor of psychology at the Brain and Creativity Institute at USC Dornsife College of Letters, Arts and Sciences. “To consider an alternative view, you would have to consider an alternative version of yourself.”
To determine which brain networks respond when someone holds firmly to a belief, the neuroscientists with the Brain and Creativity Institute at USC compared whether and how much people change their minds on nonpolitical and political issues when provided counter-evidence.
They discovered that people were more flexible when asked to consider the strength of their belief in nonpolitical statements — for example, “Albert Einstein was the greatest physicist of the 20th century.”
But when it came to reconsidering their political beliefs, such as whether the United States should reduce funding for the military, they would not budge.
“I was surprised that people would doubt that Einstein was a great physicist, but this study showed that there are certain realms where we retain flexibility in our beliefs,” Kaplan said.
The study was published on Dec. 23 in the Nature journal, Scientific Reports. Study co-authors were Sarah Gimbel of the Brain and Creativity Institute and Sam Harris, a neuroscientist for the Los Angeles-based nonprofit Project Reason.
Brain response to belief challenges
For the study, the neuroscientists recruited 40 people who were self-declared liberals. The scientists then examined through functional MRI how their brains responded when their beliefs were challenged.
During their brain imaging sessions, participants were presented with eight political statements that they had said they believe just as strongly as a set of eight nonpolitical statements. They were then shown five counter-claims that challenged each statement.
Participants rated the strength of their belief in the original statement on a scale of 1-7 after reading each counter-claim. The scientists then studied their brain scans to determine which areas became most engaged during these challenges.
Participants did not change their beliefs much, if at all, when provided with evidence that countered political statements such as, “The laws regulating gun ownership in the United States should be made more restrictive.”
But the scientists noticed the strength of their beliefs weakened by one or two points when challenged on nonpolitical topics, such as whether “Thomas Edison had invented the light bulb.” The participants were shown counter statements that prompted some feelings of doubt, such as “Nearly 70 years before Edison, Humphrey Davy demonstrated an electric lamp to the Royal Society.”
The study found that people who were most resistant to changing their beliefs had more activity in the amygdalae (a pair of almond-shaped areas near the center of the brain) and the insular cortex, compared with people who were more willing to change their minds.
“The activity in these areas, which are important for emotion and decision-making, may relate to how we feel when we encounter evidence against our beliefs,” said Kaplan, a co-director of the Dornsife Cognitive Neuroimaging Center at USC.
“The amygdala in particular is known to be especially involved in perceiving threat and anxiety,” Kaplan added. “The insular cortex processes feelings from the body, and it is important for detecting the emotional salience of stimuli. That is consistent with the idea that when we feel threatened, anxious or emotional, then we are less likely to change our minds.”
Thoughts that count
He also noted that a system in the brain, the Default Mode Network, surged in activity when participants’ political beliefs were challenged.
“These areas of the brain have been linked to thinking about who we are, and with the kind of rumination or deep thinking that takes us away from the here and now,” Kaplan said.
The researchers said that this latest study, along with one conducted earlier this year, indicate the Default Mode Network is important for high-level thinking about important personal beliefs or values.
“Understanding when and why people are likely to change their minds is an urgent objective,” said Gimbel, a research scientist at the Brain and Creativity Institute. “Knowing how and which statements may persuade people to change their political beliefs could be key for society’s progress,” she said.
The findings can apply to circumstances outside of politics, including how people respond to fake news stories.
“We should acknowledge that emotion plays a role in cognition and in how we decide what is true and what is not true,” Kaplan said. “We should not expect to be dispassionate computers. We are biological organisms.”
- Jonas T. Kaplan, Sarah I. Gimbel & Sam Harris. Neural correlates of maintaining one’s political beliefs in the face of counterevidence. Scientific Reports, December 2016 DOI: 10.1038/srep39589
Source: University of Southern California. “Hard-wired: The brain’s circuitry for political belief.” ScienceDaily. ScienceDaily, 23 December 2016. <www.sciencedaily.com/releases/2016/12/161223115757.htm>.
Impaired behavior in pregnant and lactating mice
December 22, 2016
University of Massachusetts at Amherst
In the first study of its kind, environmental health scientists and neuroscientists examined the effects of the compound bisphenol S (BPS) on maternal behavior and related brain regions in mice. They found subtle but striking behavior changes in nesting mothers exposed during pregnancy and lactation and in their daughters exposed in utero.
In the first study of its kind, environmental health scientist Laura Vandenberg and neuroscientist Mary Catanese at the University of Massachusetts Amherst examined the effects of the compound bisphenol S (BPS) on maternal behavior and related brain regions in mice. They found subtle but striking behavior changes in nesting mothers exposed during pregnancy and lactation and in their daughters exposed in utero.
BPS, found in baby bottles, personal care products and thermal receipts, is a replacement chemical for BPA and was introduced when concern was raised about possible health effects of that plastic compound. Though studies have found human BPS exposure is likely low, it is widespread and has increased over the past 10 years, the authors note. As with BPA, there is evidence that BPS is an endocrine disruptor.
Assistant professor Vandenberg and Catanese, a recent graduate of UMass Amherst’s neuroscience and behavior graduate program, report, “BPS affects maternal behavior as well as maternally relevant neural correlates.” Their results suggest that maternal care of pups, including mothers’ ability to adjust to the needs of their young during early development, was impaired after BPS exposure “with differing effects based on dose, postpartum period and generational timing of exposure.”
They note effects including “a surprising increased incidence of infanticide” in one treated group and poor maternal care, for example. Details appear in the current issue of Endocrinology.
For this work, the researchers divided pregnant mice into three treatment groups and administered no BPS or one of two low doses of BPS throughout pregnancy and lactation. The researchers then monitored nest-building, pup care and other maternal behaviors during the nursing period. Further, two female offspring from each of these litters were mated with unexposed male mice and tested for maternal behavior using the same assays used to test their mothers.
Trained observers recorded each mother’s position on or off the nest, self grooming, eating, drinking, sleeping/resting, nest repair and pup grooming at three separate time points after pups were born. Animals were also evaluated on time to retrieve pups that were moved out of the nest, another measure of maternal care.
Further, the researchers examined effects of BPS exposure in a brain region sensitive to estrogen or estrogen-mimicking chemicals that is also believed to be important in maternal behavior in mice.
The authors found a surprising increased incidence of infanticide among mouse mothers exposed to the lower dose in utero. Vandenberg and Catanese report that “although these same effects were not seen at the higher dose, more than 10 percent of females exposed to 2 microgram BPS/kg/day either killed their pups or provided such poor instrumental maternal care that one or more pups needed to be euthanized. While not statistically significant, the neglect and poor maternal care we observed were striking.”
In addition to the effects on infanticide, they also found BPS-induced effects on important aspects of maternal care in both exposed mothers and their daughters. They report that females exposed to the higher dose of BPS during pregnancy and lactation spent significantly more time on the nest than controls at one observation point, an unexpected finding given that mouse mothers usually spend less time on the nest as pups grow and develop. The researchers suggest that the mother’s BPS exposure “may indicate a lack of adjustment” to the changing needs of her pups.
BPS-exposed mothers also showed significantly shorter latency to retrieve their first pup and significantly shorter latency to retrieve their entire litter on one of the three observation days, which may not represent improved care but instead “may indicate hyperactivity, compulsivity-like behavior, heightened stress response to scattered pups, or a displaced form of retrieval.”
Different effects were seen in maternal behaviors of the exposed daughters. BPS-exposed daughters spent significantly less time on the nest compared to unexposed controls. The authors also add, “Observations suggesting an inability to attend to the changing development and needs of the pups may also be extended to measures of nest building.” In the exposed daughters, BPS treatment increased time spent nest building on one of the observation days, which “may indicate a repetitive or OCD-like behavior.”
Overall, Vandenberg and Catanese write that “uncovering effects of environmental chemicals that might influence proper maternal care have broad social and public health implications” because from an evolutionary perspective, maternal behavior is related to survival of offspring.
This work was supported by funding from UMass Amherst, a grant from the National Institute of Environmental Health Sciences and a fellowship from the Center for Research on Families at UMass Amherst.
- Mary C. Catanese and Laura N. Vandenberg. Bisphenol S (BPS) alters maternal behavior and brain in mice exposed during pregnancy/lactation and their daughters. Endocrinology, December 22, 2016 DOI: 10.1210/en.2016-1723
Source: University of Massachusetts at Amherst. “Plastics compound, BPS, often substituted for BPA, alters mouse moms’ behavior and brain regions: Impaired behavior in pregnant and lactating mice.” ScienceDaily. ScienceDaily, 22 December 2016. <www.sciencedaily.com/releases/2016/12/161222143405.htm>.
December 20, 2016
University of California, Los Angeles (UCLA), Health Sciences
Researchers have shown that the brain can be repaired — and brain function can be recovered — after a stroke in animals. The discovery could have important implications for treating a mind-robbing condition known as a white matter stroke, a major cause of dementia.
UCLA researchers have shown that the brain can be repaired — and brain function can be recovered — after a stroke in animals. The discovery could have important implications for treating a mind-robbing condition known as a white matter stroke, a major cause of dementia.
White matter stroke is a type of ischemic stroke, in which a blood vessel carrying oxygen to the brain is blocked. Unlike large artery blockages or transient ischemic attacks, individual white matter strokes, which occur in tiny blood vessels deep within the brain, typically go unnoticed but accumulate over time. They accelerate Alzheimer’s disease due to damage done to areas of the brain involved in memory, planning, walking and problem-solving.
“Despite how common and devastating white matter stroke is there has been little understanding of how the brain responds and if it can recover,” said Dr. Thomas Carmichael, senior author of the study and a professor of neurology at the David Geffen School of Medicine at UCLA. “By studying the mechanisms and limitations of brain repair in this type of stroke, we will be able to identify new therapies to prevent disease progression and enhance recovery.”
In a five-year study, Carmichael’s team looked at white matter strokes in animals and found that the brain initiated repair by sending replacement cells to the site, but then the process stalled. The team had a short list of molecular suspects from previous research that they thought might be responsible. Researchers identified a molecular receptor as the likely culprit in stalling the repair; when they blocked the receptor, the animals began to recover from the stroke.
“White matter stroke is an important clinical target for the development of new therapies,” Carmichael said.
Annually in the United States, about 795,000 suffer a stroke, resulting in nearly 130,000 deaths. Multiply the number of strokes by six, and you’ll have an estimate of the number of strokes that are “silent,” in that they do not produce symptoms that lead to hospitalization. Most of these silent strokes are white matter strokes.
The paper was published in the electronic edition of the Proceedings of the National Academy of Sciences.
Materials provided by University of California, Los Angeles (UCLA), Health Sciences. Note: Content may be edited for style and length.
- Elif G. Sozmen, Shira Rosenzweig, Irene L. Llorente, David J. DiTullio, Michal Machnicki, Harry V. Vinters, Lief A. Havton, Roman J. Giger, Jason D. Hinman, S. Thomas Carmichael. Nogo receptor blockade overcomes remyelination failure after white matter stroke and stimulates functional recovery in aged mice. Proceedings of the National Academy of Sciences, 2016; 201615322 DOI: 10.1073/pnas.1615322113
December 19, 2016
University of Liverpool
A change in weather patterns, brought on by the ‘Godzilla’ El Niño of 2015, fueled the Zika outbreak in South America, researchers report.
Scientists at the University of Liverpool have shown that a change in weather patterns, brought on by the ‘Godzilla’ El Niño of 2015, fuelled the Zika outbreak in South America.
The findings were revealed using a new epidemiological model that looked at how climate affects the spread of Zika virus by both of its major vectors, the yellow fever mosquito (Aedes aegypti) and the Asian tiger mosquito (Aedes albopictus).
The model can also be used to predict the risk of future outbreaks, and help public health officials tailor mosquito control measures and travel advice.
The model used the worldwide distribution of both vectors as well as temperature-dependent factors, such as mosquito biting rates, mortality rates and viral development rates within mosquitoes, to predict the effect of climate on virus transmission. It found that in 2015, when the Zika outbreak occurred, the risk of transmission was greatest in South America.
The researchers believe that this was likely due to a combination of El Niño — a naturally occurring phenomenon that sees above-normal temperatures in the Pacific Ocean and causes extreme weather around the world — and climate change, creating conducive conditions for the mosquito vectors.
El Niños occur every three to seven years in varying intensity, with the 2015 El Niño, nicknamed the ‘Godzilla’, one of the strongest on record. Effects can include severe drought, heavy rains and temperature rises at global scale.
Dr Cyril Caminade, a population and epidemiology researcher who led the work, said: “It’s thought that the Zika virus probably arrived in Brazil from Southeast Asia or the Pacific islands in 2013.
“However, our model suggests that it was temperature conditions related to the 2015 El Niño that played a key role in igniting the outbreak — almost two years after the virus was believed to be introduced on the continent.”
“In addition to El Niño, other critical factors might have played a role in the amplification of the outbreak, such as the non-exposed South American population, the risk posed by travel and trade, the virulence of the Zika virus strain and co-infections with other viruses such as dengue.”
The World Health Organisation recently declared that Zika, which has been linked to birth defects and neurological complications, will no longer be treated as an international emergency, but as a “significant enduring public health challenge.”
Professor Matthew Baylis, from the University’s Institute of Infection and Global Health, added: “Zika is not going away, and so the development of tools that could help predict potential future outbreaks and spread are extremely important.
“Our model predicts a potential seasonal transmission risk for Zika virus, in the south eastern United States, southern China, and to a lesser extent over southern Europe during summer.”
The researchers now plan to adapt the model to other important flaviviruses, such as Chikungunya and Dengue fever, with the aim of developing disease early warning systems that could help public health officials prepare for, or even prevent, future outbreaks.
The research was funded by the National Institute for Health Research (NIHR) Health Protection Research Unit (HPRU) in Emerging Infections and Zoonoses, a collaboration between the University of Liverpool, Liverpool School of Tropical Medicine and Public Health England.
The paper ‘Global risk model for vector-borne transmission of Zika virus reveals the role of El Niño 2015’ is published in the Proceedings of the National Academy of Sciences.
- Matthew Baylis et al. Global risk model for vector-borne transmission of Zika virus reveals the role of El Niño 2015. PNAS, December 2016 DOI: 10.1073/pnas.1614303114
Source: University of Liverpool. “El Niño fueled Zika outbreak, new study suggests.” ScienceDaily. ScienceDaily, 19 December 2016. <www.sciencedaily.com/releases/2016/12/161219151735.htm>.
Local weather may play an important role in Americans’ belief in climate change
December 19, 2016
Utah State University
Researchers from Utah State University, Boston University, The George Washington University and the University of Oxford report findings from analysis of experiential basis for skepticism about climate change in the United States.
If you’re shivering from unusually teeth-rattling cold this holiday season, global warming is probably the last thing on your mind.
“The local weather conditions people experience likely play a role in what they think about the broader climate,” says Utah State University researcher Peter Howe. “Climate change is causing record-breaking heat around the world, but the variability of the climate means that some places are still reaching record-breaking cold. If you’re living in a place where there’s been more record cold weather than record heat lately, you may doubt reports of climate change.”
Howe says people’s beliefs about climate change are driven by many factors, but a new study in which he participated suggests weather events in your own backyard may be an important influence.
With colleagues Robert Kaufmann, Sucharita Gopal, Jackie Liederman, Xiaojing Tang and Michelle Gilmore of Boston University; Michael Mann of The George Washington University and Felix Pretis of the University of Oxford, Howe published findings in the Dec. 19, 2016, Early Edition of the Proceedings of the National Academy of Sciences.
Howe, assistant professor of human-environment geography in USU’s Department of Environment and Society and the USU Ecology Center, generated the public opinion dataset used in the analysis. The collected information is based on a statistical model of more than 12,000 survey respondents across the nation from 2008 to 2013 collected by the Yale Project on Climate Change Communication and George Mason Center for Climate Change Communication.
“We found that places with more record high temperatures than lows have more residents who believe the planet is warming,” he says. “Conversely, in places with more record low temperatures, more people tend to doubt global warming.”
The study notes part of this dichotomy may be because early terminology used to describe climate change suggested the earth was simply warming, rather than changing in innumerable but measurable ways.
“One of the greatest challenges to communicating scientific findings about climate change is the cognitive disconnect between local and global events,” says Mann, one of Howe’s partners in the study. “It’s easy to assume that what you experience at home must be happening elsewhere.”
The scientists note the importance of differentiating between weather, the temperatures of a relatively short period of time, such as a season, and climate, the average temperature over a period of 25 or 30 years. Emphasizing the different between weather and climate may help the scientific community more effectively explain climate change, they say.
“Our work highlights some of the challenges of communicating about climate change, and the importance of situating people’s experiences at the local level within the larger global context,” Howe says.
Materials provided by Utah State University. Note: Content may be edited for style and length.
- Robert K. Kaufmann, Michael L. Mann, Sucharita Gopal, Jackie A. Liederman, Peter D. Howe, Felix Pretis, Xiaojing Tang, and Michelle Gilmore. Spatial heterogeneity of climate change as an experiential basis for skepticism. PNAS, December 19, 2016 DOI: 10.1073/pnas.1607032113
Source: Utah State University. “Freezing in record lows? You may doubt global warming: Local weather may play an important role in Americans’ belief in climate change.” ScienceDaily. ScienceDaily, 19 December 2016. <www.sciencedaily.com/releases/2016/12/161219151744.htm>.
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