Earth

Cash in on the kids' inheritance and spend up big on the retirement plans - that's the message coming from the University of South Australia as new research reveals that older people are keen to spend their well-earned savings, rather than passing them on to their kids.

And while it may seem like bad news for the younger generation, the research also confirms that the kids are just fine with this scenario, claiming that no one owes anyone anything.

The surprising findings are part of a new study that explores contemporary attitudes towards wealth transfer taxation in Australia, finding that public resistance to inheritance and estate taxes may have declined in the 40 years since they were abolished in Australia.

Inheritance is the only major form of income that is untaxed in Australia - a person who works for their income pays tax on it while someone who receives a bequest is not even liable for capital gains tax.

Social policy expert, Dr Veronica Coram from UniSA's Australian Alliance for Social Enterprise says the apparent decline in the bequest motive presents a significant opportunity for Australian tax reform, and a valuable chance to address social inequalities.

"There's nothing more certain than death and taxes. But while people generally assume the combination is notoriously unpopular, our research suggests otherwise," Dr Coram says.

"We talked to young adults and senior Australians and two thirds of them thought Australia should consider reintroducing taxes on estates worth more than $3m, while only one in ten were definitely opposed.

"The lack of interest in giving or receiving inheritances meant that most participants saw no reason to object to estates being taxed, which opens potential opportunities for much-needed tax reform.

"Inheritances generally go to people who are already well-off and don't need them; they encourage inequality and inhibit social mobility.

"The Australian government needs to find ways to raise revenue to support increased spending demands generated by COVID-19, an ageing population, pressure on health systems and increasing environmental disasters.

"Reintroducing inheritance or estate taxation is a way of increasing government revenue, while reducing a key driver of inequality at the same time."

While politicians and policymakers may be wary of making moves, Dr Coram says the findings reflect changes to social norms in Australia and other OECD countries.

"Historically, inheritance taxes have been considered 'political suicide'. But perhaps their time has come, ironically due to a growing individualism and associated decline in the assumption that family members should provide for one another," Dr Coram says.

"More research on changing views towards redistributive policy is required, but the results of our study suggest that if governments are considering tax reform, they should not assume that Australians are vehemently opposed to wealth transfer taxation."

Bottom Line: For women diagnosed with breast cancer in Florida, breast cancer-specific mortality rates have decreased more among Black and Hispanic women than white women since 1990. Despite these advances, Black women still have double the five- and 10-year mortality rates of non-Hispanic white women.

Journal in Which the Study was Published: Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.

Author: Robert Hines, PhD, MPH, associate professor of population health sciences at the University of Central Florida College of Medicine.

Background: On a national level, over the past several decades, the incidence of breast cancer diagnosis in Black women has been less than that for white women, and Black women have been more likely to be diagnosed with more advanced disease. Over time, incidence in Black women rose to nearly the same level as that of white women, an effect Hines attributes to targeted breast cancer surveillance in those populations.

Around 1990, breast cancer mortality rates began to decline, reflecting improved screening and the availability of new therapeutics, but the decline was far slower in Black women, Hines explained.

"Since the 80s, there's been increasing awareness of the disparities in breast cancer mortality and the troubling fact that they've grown over time," Hines said. "There's been a huge investment in decreasing or eliminating these disparities, but we wanted to see if it's been effective." Such initiatives have largely focused on improving screening education and availability for socioeconomically disadvantaged populations and racial and ethnic minorities.

How the Study Was Conducted: Hines and colleagues obtained records from the Florida Cancer Data System of over 250,000 women diagnosed with breast cancer from the years 1990-2015. Their sample set consisted of female patients who self-identified as non-Hispanic white (79.5 percent), non-Hispanic Black (10.5 percent), Hispanic white (9.7 percent), or Hispanic Black (0.3 percent). The researchers studied the cumulative incidence of breast cancer death as well as 5- and 10-year relative hazard rates for individuals in each group. They clustered patients based on year of diagnosis: 1990-1994, 1995-2004, and 2005-2015.

Results: Researchers found that for all racial and ethnic groups, mortality decreased gradually from 1990 to 2015. In non-Hispanic white women, 10-year mortality decreased from 20.6 percent in the first five years (1990-1994) to 14.0 percent in the final time period (2010-2015). In non-Hispanic Black women, 10-year mortality decreased from 36.0 percent to 25.9 percent.

In the most recent 10 years surveyed, there was no significant difference in five- or 10-year mortality rates between Hispanic white and non-Hispanic white women, data that Hines found both surprising and encouraging. But despite these advances, Hines stresses that Black women still have double the five- and 10-year mortality rates of non-Hispanic white women.

The results also hinted at possible factors underlying the continuing disparities. When the researchers normalized the mortality data based on age, insurance status, census-tract poverty, tumor stage and grade at diagnosis, and treatment received, the 10-year relative rate of breast cancer mortality for Black women--which was 102 percent higher than white women prior to normalization of data--decreased to 20 percent higher than white women.

Author's Comments: "Over the past three decades, we've seen an improvement in breast cancer survival for all women--especially for minority women--which is encouraging. However, in the most recent time period, non-Hispanic Black women have twice the rate of breast cancer death compared to non-Hispanic white women," Hines said. "We need to celebrate the progress we make, but we have a ways to go to produce equitable outcomes for women diagnosed with breast cancer."

As next steps, Hines and his team hope to pinpoint specific reasons for the continuing disparities, in order to advise future initiatives aimed at closing the gap. "In order to have the most impact, we need to tease out the individual factors that are most responsible," Hines said.

Study Limitations: Limitations of this study include incomplete data for a fraction of patients, especially at earlier time points, when some of the diagnostic criteria used often today were not commonly assessed. The study also excluded patients who identified as a race other than white or Black, or an ethnicity other than Hispanic.

Funding & Disclosures: This study was funded by the University of Central Florida College of Medicine. The authors declare no conflicts of interest.

An invasive species of aphid could put some threatened plant species on Kangaroo Island at risk as researchers from the University of South Australia confirm Australia's first sighting of Aphis lugentis on the Island's Dudley Peninsula.

It is another blow for Kangaroo Island's environment, especially following the Black Summer bushfires that decimated more than half the island and 96 per cent of Flinders Chase National Park.

Collected by wildlife ecologist Associate Professor Topa Petit and identified by colleagues from the WA Department of Primary Industries and Regional Development, the black aphids were found feeding on seedlings of Senecio odoratus, a native species of daisy, commonly known as the scented groundsel.

Of 16 native Senecio species on the island, at least ten are of conservation concern.

Originating from North America, the sap-sucking black aphids have spread across multiple continents over the past 20 years. This first record of the pest in Australia.

Assoc Prof Petit says the alien aphid species could threaten plants in the Compositae (daisy) family.

"Aphids were tended by several species of native ants that were feeding on their honeydew, showing easy integration for the pest in its new environment," Dr Petit says.

"The presence of Aphis lugentis on Kangaroo Island could have serious consequences on seedling survival of Senecio and related species - as well as unknown ones for native ant communities."

Currently, 1,257 of Australia's threatened and endangered species are directly affected by 207 invasive plants, 57 animals and three pathogens. The most recent estimates found the cost of controlling invasive species and economic losses to farmers in 2011-12 was A$13.6 billion.

Once established across Australia, invasive species can be very difficult to eradicate.

Entomology diagnostician, Cameron Brumley from the Department of Primary Industries and Regional Development in Western Australia, and geneticists Monica Kehoe and Cuiping Wang, examined the aphid and found matching DNA in a collection from Hurstville, NSW, indicating the greater spread of aphid across Australia. Authorities have been alerted.

"It is still unclear how some fragile species of Kangaroo Island are coping following last year's bushfires, so I recommend that attention be paid to aphids present on plants related to daisies, on the island, but also on the mainland considering the likely presence of the aphid in other states. Its distribution needs to be mapped," Dr Petit says.

"This aphid was probably introduced to Australia on ornamental plants. Locally native plants and native gardens offer better habitats for native wildlife and lower invasion risks. We need to learn to appreciate our remarkable native flora."

Researchers at the Biodiversity Unit of the University of Turku, Finland, study insect biodiversity particularly in Amazonia and Africa. In their studies, they have discovered hundreds of species previously unknown to science. Many of them are exciting in their size, appearance, or living habits.

"The species we have discovered show what magnificent surprises the Earth's rainforests can contain. The newly discovered Dolichomitus meii wasp is particularly interesting for its large size and unique colouring. With a quick glance, its body looks black but glitters electric blue in light. Moreover, its wings are golden yellow. Therefore, you could say it's like a flying jewel," says Postdoctoral Researcher Diego Pádua from the Instituto Nacional de Pesquisas da Amazônia (INPA) in Brazil, who has also worked at the Biodiversity Unit of the University of Turku.

Dolichomitus parasitoid wasps are parasitic on insect larvae living deep in tree trunks. They lay a single egg on the insect larva and the wasp hatchling eats the host larva as it develops.

"The ovipositor of the Dolichomitus meii wasp is immensely long. It sticks the ovipositor into holes in the wood and tries to find host larvae inside. The species' striking colouring protects it from birds that prey on insects. They do not snatch the wasp sitting on the tree trunk as they think it will taste bad or that it is dangerous," says Professor of Biodiversity Research Ilari E. Sääksjärvi from the University of Turku.

Polysphincta parasitoid wasps manipulate the behaviour of the host spider

At the same time as the publication on the Dolichomitus meii species, the researchers published another research article on South American wasp species. The article describes altogether seven new wasp species belonging to the Polysphincta genus.

The Polysphincta parasitoid wasps are parasitic on spiders. The female attacks a spider in its web and temporarily paralyses it with a venomous sting. After this, the wasp lays a single egg on the spider, and a larva hatches from the egg. The larva gradually consumes the spider and eventually pupates.

"The wasps that are parasitic on spiders are extremely interesting as many of them can manipulate the behaviour of the host spider. They can change the way a spider spins its web, so that before its death, the spider does not spin a normal web to catch prey. Instead, they spin a safe nest for the parasitoid wasp pupa," describes Professor Sääksjärvi.

Researchers at University of Turku have already discovered 53 new species this year

The new species are often discovered through extensive international collaboration. This was also the case with the newly published studies.

"For example, the discovery of the Dolichomitus meii species was an effort of six researchers. Moreover, these researchers all come from different countries," says Professor Sääksjärvi.

The work to map out biodiversity previously unknown to science continues at the University of Turku and there are interesting species discoveries ahead.

"I just counted that, in 2021, the researchers of the Biodiversity Unit at the University of Turku have described already 53 new species from different parts of the globe - and we're only halfway through the year," Sääksjärvi announces cheerfully.

The discoveries of the research group were published in the Biodiversity Data Journal and ZooKeys.

Contrary to what science once suggested, older people with a declining sense of smell do not have comprehensively dampened olfactory ability for odors in general - it simply depends upon the type of odor. Researchers at the University of Copenhagen reached this conclusion after examining a large group of older Danes' and their intensity perception of common food odours.

That grandpa and grandma aren't as good at smelling as they once were, is something that many can relate to. And, it has also been scientifically demonstrated. One's sense of smell gradually begins to decline from about the age of 55. Until now, it was believed that one's sense of smell broadly declined with increasing age. However, a study from the University of Copenhagen reports that certain food odors are significantly more affected than others.

The Department of Food Science's Eva Honnens de Lichtenberg Broge and her fellow researchers have tested the ability of older Danes to perceive everyday food odors. The researchers measured how intensely older adults perceived different food odours, as well as how much they liked the odours.

"Our study shows that the declining sense of smell among older adults is more complex than once believed. While their ability to smell fried meat, onions and mushrooms is markedly weaker, they smell orange, raspberry and vanilla just as well as younger adults. Thus, a declining sense of smell in older adults seems rather odor specific. What is really interesting is that how much you like an odor is not necessarily dependent on theintensity perception" says Eva Honnens de Lichtenberg Broge.

For example, liking of seemed to be largely unaffected for fried meat, onions and mushrooms, despite the largest decline in intensity perception was seen for these specific odors. Also the ability to smell coffee declined, among other things, though they didn't like the aroma of coffee to the same degree as younger adults.

The test subjects included 251 Danes between the ages of 60 and 98 and a control group consisting of 92 people between the ages of 20 and 39.

What's the story?

The researchers can only speculate as to why the declining sense of smell in older adults seems to be odors specific, and why, in some cases, liking is largely unaffected. However, they can only speculate of why the intensity decline was most pronounced for fried meat, onions and mushrooms - foods that are referred to as 'savory' or umami in nature.

"This may be due to the fact that these are common food odours in which saltiness or umami is a dominant taste element. It is widely recognized that salty is the basic taste most affected by aging. Since taste and smell are strongly associated when it comes to food, our perception of aroma may be disturbed if one's taste perception of saltiness is impaired to begin with," explains Eva Honnens de Lichtenberg Broge.

Health and quality of life

The researchers hope that their findings can be deployed by those working to improve the meals and dining experiences of older adults. Figures show that half of those over 65 admitted to Danish hospitals are malnourished. The same applies to one in five nursing home residents.

While the sense of smell is important for stimulating appetite and our serotonin levels as well, according to Eva Honnens de Lichtenberg Broge, our study demonstrates that the sensitivity of one's sense of smell need not be decisive. For several of the food odours, the respondent's liking of an odour remained unchanged, even while their ability to perceive it had declined.

"Our results show that as long as a food odour is recognizable, its intensity will not determine whether or not you like it. So, if one wants to improve food experiences of older adults, it is more relevant to pay attention to what they enjoy eating than it is to wonder about which aromas seem weaker to them," concludes Eva Honnens de Lichtenberg Broge.

The study is published in the scientific journal Food Quality and Preference.

FACTS:

The study was conducted in the Future Consumer Lab at the University of Copenhagen's Department of Food Science by Eva Honnens de Lichtenberg Broge, Karin Wendin, Morten A. Rasmussen and Wender Bredie.

The study involved 251 Danish older adults from five different regions. The test subjects were aged 60-98. As a control group, 92 people between the ages of 20 and 39 took part.

Instead of using odours of chemical origin, which is commonly the procedure when testing the sense of smell, Eva Honnens de Lichtenberg Broge developed a test kit including 14 natural food odours familiar from everyday life, including bacon, onions, toast, asparagus, coffee, cinnamon, orange and vanilla. The odours were made primarily from essential oils and presented to test subjects by sniffing sticks.

The food odours were chosen based upon commonly consumed foods and dishes that older people often eat and enjoy most according to meal plans and surveys from a Danish catering company that provides food for the elderly.

The study is part of the ELDORADO project. The project aims to study how Danish municipalities can increase the desire of elderly people living at home to eat more, so as to help them avoid becoming malnourished. The ELDORADO project is based at the Department of Food Science and led by Wender Bredie.

Harpy eagles (Harpia harpyja) - which are among the world's largest eagle species - struggle to feed offspring in heavily deforested areas of the Amazon, according to a study published in Scientific Reports.

Everton Miranda and colleagues found that harpy eagles rely on specific prey that lives in canopy forests, including sloths and monkeys. Eaglets starved in areas of high deforestation where canopy-based food was limited.

The authors observed prey species, how frequently prey was delivered, and estimated the weight of prey in 16 harpy eagle nests in Amazonian forests in Mato Grosso, Brazil using cameras and identifying prey bone fragments. They also referenced maps and Google Earth to calculate deforestation levels 3-6km around nests. The authors identified 306 prey items, nearly half (49.7%) of which were two-toed sloths, brown capuchin monkeys and grey woolly monkeys. The authors' observations indicated that harpy eagles in deforested areas did not switch to alternative prey, and delivered canopy-based prey less frequently and with smaller estimated weight. In landscapes with 50-70% deforestation, three eaglets died from starvation, and no nests were found in areas with deforestation over 70%.

The authors calculated that areas with over 50% deforestation are unsuitable for harpy eagles to successfully raise offspring and estimate that around 35% of northern Mato Grosso is unsuitable for breeding harpy eagles. This may have caused a decline in numbers of breeding pairs by 3,256 since 1985.

The authors conclude that as breeding harpy eagles rely on specific food and rarely hunt in deforested areas, harpy eagle survival depends on forest conservation.

A new study based on computational analyses of how SARS-CoV-2 interacts with host cell proteins has identified 200 previously approved drugs that could be repurposed to treat COVID-19, 40 of which have already entered clinical trials. Furthermore, Namshik Han and colleagues identified 30 proteins induced by the SARS-CoV-2 virus that are targeted by 8 or more existing drugs, finding that nitric oxide production, which is important for viral synthesis, may be targeted by these drugs to fight infection. The researchers also identified 2 of these drugs with good safety profiles that successfully reduced viral replication in cellular assays, suggesting they could potentially prevent or treat COVID-19. Scientists now have sufficient data to understand the mechanisms by which SARS-CoV-2 interacts with host cell proteins better, illuminating possible individual targets and pathways. Existing approved drugs can be tested against these pathways to determine whether they may be repurposed to treat COVID-19. To advance this research, Han et al. developed a network of proteins induced by SARS-CoV-2 based on disease signatures and cross-examined these pathways against approved drugs. They used artificial neural network analysis to classify these 200 drugs into 9 distinct pathways within 2 overarching mechanisms: viral replication and immune response. Of the 1,573 proteins targeted by these 200 drugs, 66% were targeted by a single drug, while 0.19% (30 proteins) were targeted by 8 drugs or more. The researchers validated five drugs that targeted these 30 proteins using monkey cells in vitro, finding that proguanil (an anti-malarial drug) and sulfasalazine (a rheumatoid arthritis drug) showed antiviral effects without appearing to damage the cells. Further in vitro tests revealed that both drugs significantly reduced the phosphorylation of an important component of a protein kinase signaling pathway activated during SARS-CoV-2 infection, known to stimulate the release of cytokines that can cause potentially dangerous inflammation.

In 1934, physicist Eugene Wigner made a theoretical prediction based on quantum mechanics that for 87 years went unseen.

The theory suggested how a metal that normally conducts electricity could turn into a nonconducting insulator when the density of electrons is reduced. Wigner theorized that when electrons in metals are brought to ultracold temperatures, these electrons would be frozen in their tracks and form a rigid, non-electricity conducting structure -- a crystal -- instead of zipping around at thousands of kilometers per second and creating an electric current. Since he discovered it, the structure was coined a Wigner Crystal and was observed for the first time in 1979.

What's remained stubbornly elusive to physicists, however, has been the melting of the crystal state into a liquid in response to quantum fluctuations. At least, it was: Now, almost 90 years later, a team of physicists co-led by Hongkun Park and Eugene Demler in the Faculty of Arts and Sciences has finally experimentally documented this transition.

The work is described in a new study published in the journal Nature and marks a big step toward creating a system for studying these kinds of transitions between states of matter at the quantum level, a long-sought-after goal in the field.

"This is right at the border of matter of changing from partially quantum material to partially classical material and has many unusual and interesting phenomena and properties," said Eugene Demler, a senior author on the paper. "The crystal themselves have been seen, but this, sort of, pristine transition -- when quantum mechanics and classical interactions are competing with each other -- has not been seen. It has taken 86 years."

Led by Park and Demler, the research team focused on observing Wigner crystals and their phase transitions in the study. In chemistry, physics, and thermodynamics, phase transitions happen when a substance changes from a solid, liquid, or gas to a different state. When quantum fluctuations near absolute zero temperature drive these transitions, they are called quantum phase transitions. These quantum transitions are thought to play an important role in many quantum systems.

In the case of a Wigner crystal, the crystal-to-liquid transition happens from a competition between the classical and quantum aspects of the electrons - the former dominating in the solid phase, in which electrons are "particle-like," and the latter dominating in the liquid, in which electrons are "wave-like." For a single electron, quantum mechanics tells us that the particle and wave nature are complementary.

"It is striking that, in a system of many interacting electrons, these different behaviors manifest in distinct phases of matter," said Park. "For these reasons, the nature of the electron solid-liquid transition has drawn tremendous theoretical and experimental interest."

The Harvard scientists report using a novel experimental technique developed by You Zhou, Jiho Sung, and Elise Brutschea -- researchers from the Park Research Group and lead authors on the paper -- to observe this solid to liquid transition in atomically thin semiconductor bilayers. In general, Wigner crystallization requires very low electron density, making its experimental realization a major experimental challenge. By constructing two interacting electron layers from two atomically thin semiconductors, experimentalists created a situation in which the crystallization is stabilized at higher densities.

To see the transition, the researchers used a method called exciton spectroscopy. They use light to excite an electron in the system and bind it to the electron vacancy, or hole, it leaves behind, forming hydrogen-like electron-hole pair known as an exciton. This pair interacts with the other electrons in the material and modifies its properties so they can be optically seen.

The findings from the paper were largely accidental and came as a surprise, according to the researchers. The Park group initially set out in a different direction and were puzzled when they noticed the electrons in their material displayed insulating behavior. They consulted with theorists from Demler's lab and soon realized what they had.

The researchers plan on using their new method to continue to investigate other quantum phase transitions.

"We now have an experimental platform where all these [different quantum phase transition] predictions can now be tested," Demler said.

Decision-makers around the world are increasingly interested in using ecosystem solutions such as mangroves, coral reefs, sand dunes and forests on steep slopes to help buffer the impacts from hazard events and protect populations. But what evidence exists to show the efficacy of nature-based solutions over man-made protective measures to reduce the impacts of the increasing numbers of hazard events humanity faces due to climate change?

An international, multi-disciplinary team of 28 researchers has examined nearly 20 years' worth of peer-reviewed studies on the impacts of ecosystem-based disaster risk reduction (DRR) efforts to, for the first time, summarize the state of knowledge of ecosystem services and functions for DRR. The team reviewed 529 English-language articles to catalog the extent of knowledge on, and confidence in, ecosystems in reducing disaster risk.

"This is the most extensive and up-to-date assessment of the role nature-based solutions can play for reducing impacts of natural hazards" affirms Dr. Jaroslav Mysiak, director of the research division 'Risk assessment and adaptation strategies' at the CMCC Foundation - Euro-Mediterranean Center on Climate Change. "It complements the recently released European Environment Agency's report in the context of climate change and resilience".

As reported in the article published by the journal Nature Sustainability, researchers assessed the state of knowledge on the role ecosystems play in reducing the disaster risk: from the management of wildfires to the mitigation of flooding in urban areas through the implementation of green design, from the use of vegetation on steep slopes to cost-effectively reduce mountain hazards - such as mudslides and avalanches - to the management of stormwater.

Their review of existing research reveals that persistent droughts, land degradation and desertification are often slow-onset processes in drylands that, over time, may well lead to disaster. Importantly, they found ample evidence of how ecosystem-based approaches in areas susceptible to drought can reduce the impacts of climate change.

The main author of the article Karen Sudmeier, Senior Adviser, Disaster Risk Reduction, United Nations Environment Programme writes in a blog post: "Two decades of research analyzed over six years left us with a number of questions: we know there is evidence that most ecosystems reduce the impacts of hazard events in a cost-effective manner. Now we need to disseminate this evidence in the language that decision-makers speak: how much, how high, how wide? We also need to focus our attention on performance standards, green design blueprints, ecological engineering standard operating procedures and the specs that will provide the ultimate evidence base to draw attention and investment to nature's solutions to increasing numbers of hazard events worldwide. Our research in this growing field has only just begun."

The report, "Scientific evidence for ecosystem-based disaster risk reduction," is available online from Nature Sustainability.

Tokyo, Japan - Believe it or not, steel has something in common with bacterial appendages: they can both undergo a special type of physical transformation that remains puzzling. Now, researchers from Japan and China have used direct microscopic observations to provide more clarity to how this transformation occurs.

In a study recently published in Nature Communications, researchers from The University of Tokyo Institute of Industrial Science and Fudan University Department of Physics have revealed previously unknown physical details that underpin crystalline solid-to-solid phase transitions in soft materials, and possibly how researchers can more fully exploit the properties of advanced materials.

A special type of solid-to-solid phase transition, known as a martensitic transition, is an exciting frontier in medicine, technology, and other fields. The martensitic transition is enabled by a coordinated movement of atoms in a material, which changes the properties of the material without changing its chemical composition. Metal alloys and proteins can both undergo this transition. Researchers hypothesize that in easily deformable soft materials, the transition may occur differently from those observed in hard materials with stable defects. At present, this hypothesis is difficult to test, something the researchers aimed to address.

"Traditionally, it has been challenging to microscopically observe the dynamic process of martensitic transitions in soft materials on a single-particle level," says co-senior author of the study Hajime Tanaka. "One must devise a means to do so in a way that quickly initiates the transition without harmful perturbation to the system."

To do this, the researchers used a gentle technique known as ion exchange--in principle, the same method used to remove calcium and magnesium ions from water--to quickly change the crystal structure of polymeric microparticles. One can observe the kinetics of the resulting martensitic transitions with a microscope with single-particle resolution.

"The microscopy results were unambiguous," explains Peng Tan, co-senior author of the study. "We observed three previously unknown mechanisms by which body-centered cubic soft colloidal crystals form from face-centered cubic ones, depending on the condition."

The researchers examined the features of these pathways--termed thermally activated in-grain nucleation, grain-boundary-premelting-assisted nucleation, and wall-assisted growth--with particular focus on how the energy barrier to the transition is reduced in each case.

"Softness of a crystal plays a critical role in thermally activated in-grain nucleation," explains Tanaka. "Whereas, the other two pathways may occur even in hard materials."

These results have diverse applications. For example, some pharmaceuticals can alter their availability in the body by solid-to-solid phase transitions; therefore, understanding how to control when and where such transitions occur could provide a new means of targeted drug delivery. A greater understanding of the physical mechanisms of solid-to-solid transformations supports the development of new materials that can be tailored for applications.

Boulder, Colo., USA: GSA's dynamic online journal, Geosphere, posts articles online regularly. Locations and topics studied this month include the central Appalachian Mountains; fossil pollen in Colombia; the precision and accuracy of model analyses; the Bone Spring Formation, Permian Basin, west Texas; and the geochronology of modern river sediment in south-central Alaska. You can find these articles at https://geosphere.geoscienceworld.org/content/early/recent .

Spatially variable syn- and post-Alleghanian exhumation of the central Appalachian Mountains from zircon (U-Th)/He thermochronology
Luke C. Basler; Jaclyn S. Baughman; Michelle L. Fame; Peter J. Haproff

Abstract: To assess spatial and temporal patterns of Phanerozoic orogenic burial and subsequent exhumation in the central Appalachian Mountains, we present mid-temperature zircon (U-Th)/He (ZHe; closure temperature [T C] = 140-200 °C) dates for 10 samples along a 225 km, strike-perpendicular transect spanning the Appalachian Plateau, Valley and Ridge, Blue Ridge, and Piedmont physiographic provinces in West Virginia and western Virginia. Ranges of single-grain ZHe dates exhibit an eastward younging trend from 455-358 Ma in the Pennsylvanian Appalachian Plateau to 336-209 Ma in the Valley and Ridge, 298-217 Ma in the Blue Ridge, and 186-121 Ma in the Piedmont. Within the Pennsylvanian Appalachian Plateau, detrital ZHe dates are older than corresponding depositional ages, thus limiting postdepositional burial temperatures to less than 160 °C. These ZHe dates capture predepositional mid-Paleozoic cooling signatures, indicating provenance from either recycled Taconic or Acadian basin strata or mid-Paleozoic Appalachian terranes. Across the Valley and Ridge and western Blue Ridge provinces, reset Permian detrital ZHe dates feature flat date-effective uranium correlations that suggest rapid Alleghanian cooling initiating prior to 270 Ma. ZHe dates within the Valley and Ridge are more than 100 m.y. older than previously reported regional apatite fission-track dates, reflecting a protracted period of stable post-Alleghanian thermal conditions within the foreland. By contrast, post-Triassic single-grain ZHe dates in the interior Piedmont document rapid postrift cooling, likely resulting from both the relaxation of an elevated geothermal gradient and exhumation from rift-flank uplift. The spatial discontinuity between stable synrift thermal conditions in the Valley and Ridge and rapid cooling in the Piedmont suggests that rift-flank uplift and cooling were concentrated outboard of the foreland within the Piedmont province.

View article: https://pubs.geoscienceworld.org/gsa/geosphere/article-abstract/doi/10.1130/GES02368.1/602754/Spatially-variable-syn-and-post-Alleghanian

Constraints on the paleoelevation history of the Eastern Cordillera of Colombia from its palynological record
Peter Molnar; Lina C. Pérez-Angel

Abstract: We attempted to make an objective assessment of whether fossil pollen assemblages from the Sabana de Bogotá require surface uplift of ~2000 m since 6-3 Ma, as has been argued. We relied on recently published elevation ranges of plants for which fossil pollen has been found in sites 2000-2500 m high in the Sabana de Bogotá. The elevation ranges of fossil plants do not overlap, suggesting that those ranges may be too narrow. By weighting these elevation ranges by percentages of corresponding fossil pollen and summing them, we estimated probability density functions for past elevations. These probability distributions of past elevations overlap present-day elevations and therefore do not require surface uplift since deposition of the pollen. Fossil pollen assemblages include pollen from some plant taxa for which we do not know present-day elevation ranges, and therefore, with a more complete knowledge of elevation distributions, tighter constraints on elevations should be obtainable. The elevation of the oldest assemblage, from Tequendama, which lies at the southern edge of the Sabana de Bogotá and is thought to date from 16 to 6 Ma, is least well constrained. Although our analysis permits no change in elevation since the pollen was deposited, we consider 1000-2000 m of elevation gain since 15 Ma to be likely and consistent with an outward growth of the Eastern Cordillera.

View article: https://pubs.geoscienceworld.org/gsa/geosphere/article-abstract/doi/10.1130/GES02328.1/602755/Constraints-on-the-paleoelevation-history-of-the

Reconstructing the tectono-sedimentary evolution of the Early- Middle Jurassic Tlaxiaco Basin in southern Mexico: New insights into the crustal attenuation history of southern North America during Pangea breakup
Mildred Zepeda-Martínez; Michelangelo Martini; Luigi A. Solari; Claudia C. Mendoza-Rosales

Abstract: During Pangea breakup, several Jurassic extensional to transtensional basins were developed all around the world. The boundaries of these basins are major structures that accommodated continental extension during Jurassic time. Therefore, reconstructing the geometry of Jurassic basins is a key factor in identifying the major faults that produced continental attenuation during Pangea breakup. We reconstruct the tectono-sedimentary evolution of the Jurassic Tlaxiaco Basin in southern Mexico using sedimentologic, petrographic, and U-Pb geochronologic data. We show that the northern boundary of the Tlaxiaco Basin was an area of high relief composed of the Paleozoic Acatlán Complex, which was drained to the south by a set of alluvial fans. The WNW-trending Salado River-Axutla fault is exposed directly to the north of the northernmost fan exposures, and it is interpreted as the Jurassic structure that controlled the tectono-sedimentary evolution of the Tlaxiaco Basin at its northern boundary. The eastern boundary is represented by a topographic high composed of the Proterozoic Oaxacan Complex, which was exhumed along the NNW-trending Caltepec fault and was drained to the west by a major meandering river called the Tlaxiaco River. Data presented in this work suggest that continental extension during Pangea breakup was accommodated in Mexico not only by NNW-trending faults associated with the development of the Tamaulipas-Chiapas transform and the opening of the Gulf of Mexico, but also by WNW-trending structures. Our work offers a new perspective for future studies that aim to reconstruct the breakup evolution of western equatorial Pangea.

View article: https://pubs.geoscienceworld.org/gsa/geosphere/article-abstract/doi/10.1130/GES02309.1/602756/Reconstructing-the-tectono-sedimentary-evolution

Age and tectonic setting of the Quinebaug-Marlboro belt and implications for the history of Ganderian crustal fragments in southeastern New England, USA
Gregory J. Walsh; John N. Aleinikoff; Robert A. Ayuso; Robert P. Wintsch

Abstract: Crustal fragments underlain by high-grade rocks represent a challenge to plate reconstructions, and integrated mapping, geochronology, and geochemistry enable the unravelling of the temporal and spatial history of exotic crustal blocks. The Quinebaug-Marlboro belt (QMB) is an enigmatic fragment on the trailing edge of the peri-Gondwanan Ganderian margin of southeastern New England. SHRIMP U-Pb geochronology and geochemistry indicate the presence of Ediacaran to Cambrian metamorphosed volcanic and intrusive rocks dated for the first time between ca. 540-500 Ma. The entire belt may preserve a cryptic, internal stratigraphy that is truncated by subsequent faulting. Detrital zircons from metapelite in the overlying Nashoba and Tatnic Hill Formations indicate deposition between ca. 485-435 Ma, with provenance from the underlying QMB or Ganderian crust. The Preston Gabbro (418 ± 3 Ma) provides a minimum age for the QMB. Mafic rocks are tholeiitic with trace elements that resemble arc and E-MORB sources, and samples with negative Nb-Ta anomalies are similar to arc-like rocks, but others show no negative Nb-Ta anomaly and are similar to rocks from E-MORB to OIB or backarc settings. Geochemistry points to a mixture of sources that include both mantle and continental crust. Metamorphic zircon, monazite, and titanite ages range from 400 to 305 Ma and intrusion of granitoids and migmatization occurred between 410 and 325 Ma. Age and chemistry support correlations with the Ellsworth terrane in Maine and the Penobscot arc and backarc system in Maritime Canada. The arc-rifting zone where the Mariana arc and the Mariana backarc basin converge is a possible modern analog.

View article: https://pubs.geoscienceworld.org/gsa/geosphere/article-abstract/doi/10.1130/GES02295.1/602757/Age-and-tectonic-setting-of-the-Quinebaug-Marlboro

Precision and accuracy of modal analysis methods for clastic deposits and rocks: A statistical and numerical modeling approach
Pierre-Simon Ross; Bernard Giroux; Benjamin Latutrie

Abstract: Quantifying the proportions of certain components in rocks and deposits (modal analysis or componentry) is important in earth sciences. Relevant methods for cross-sections (two- dimensional exposures) of clastic rocks include point counts or line counts. The accuracy of these methods has been supposed to be good in the literature but not necessarily verified empirically. Natural materials are inappropriate for assessing accuracy because the true proportions of each component are unknown. The precision of modal analysis methods has traditionally been evaluated from statistical models (primarily the normal approximation to the binomial distribution) but again rarely verified in practice because it is also extremely difficult to obtain different slices through the same material at outcrop scale. Here we create a set of numerical models of red and blue spheres with different proportions and sizes and cut 60 slices through the models, on which we perform point counts and line counts. We show that both of these methods are indeed able to retrieve the correct volumetric proportions of components, on average, when enough fragments are counted or intersected. As already known, precision is controlled by component abundance and the number of points counted or clasts intersected. However, we show that other important factors include differences between slices, which are relevant for our unequal-size models, and the proportion of voids, matrix, and/or cement in the rock. We present empirical precision charts for clast counts and line counts based on our models and make recommendations for future field studies.

View article: https://pubs.geoscienceworld.org/gsa/geosphere/article-abstract/doi/10.1130/GES02374.1/602758/Precision-and-accuracy-of-modal-analysis-methods

Progradational slope architecture and sediment distribution in outcrops of the mixed carbonate-siliciclastic Bone Spring Formation, Permian Basin, west Texas
Wylie Walker; Zane R. Jobe; J.F. Sarg; Lesli Wood

Abstract: Sediment transport and distribution are the keys to understanding slope-building processes in mixed carbonate-siliciclastic sediment routing systems. The Permian Bone Spring Formation, Delaware Basin, west Texas, is such a mixed system and has been extensively studied in its distal (basinal) extent but is poorly constrained in its proximal upper-slope segment. Here, we define the stratigraphic architecture of proximal outcrops in Guadalupe Mountains National Park in order to delineate the shelf-slope dynamics of carbonate and siliciclastic sediment distribution and delivery to the basin. Upper-slope deposits are predominantly fine-grained carbonate lithologies, interbedded at various scales with terrigenous (i.e., siliciclastic and clay) hemipelagic and gravity-flow deposits. We identify ten slope-building clinothems varying from terrigenous-rich to carbonate-rich and truncated by slope detachment surfaces that record large-scale mass wasting of the shelf margin. X-ray fluorescence (XRF) data indicate that slope detachment surfaces contain elevated proportions of terrigenous sediment, suggesting that failure is triggered by changes in accommodation or sediment supply at the shelf margin. A well-exposed terrigenous-rich clinothem, identified here as the 1st Bone Spring Sand, provides evidence that carbonate and terrigenous sediments were deposited contemporaneously, suggesting that both autogenic and allogenic processes influenced sediment accumulation. The mixing of lithologies at multiple scales and the prevalence of mass wasting acted as primary controls on the stacking patterns of terrigenous and carbonate lithologies of the Bone Spring Formation, not only on the shelf margin and upper slope, but also in the distal, basinal deposits of the Delaware Basin.

View article: https://pubs.geoscienceworld.org/gsa/geosphere/article-abstract/doi/10.1130/GES02355.1/600740/Progradational-slope-architecture-and-sediment

Introduction: Active Margins in Transition--Magmatism and Tectonics through Time: An Issue in Honor of Arthur W. Snoke
Allen J. McGrew; Joshua J. Schwartz

Abstract: The evolution of active margins through time is the record of plate tectonics as inscribed on the continents. This themed issue honors the eclectic contributions of Arthur W. Snoke (Fig. 1) to the study of active margins with a series of papers that amply demonstrate the broad scope of active margin tectonics and the diverse methods that tectonic geologists employ to decipher their histories. Taken together, this set of papers illustrates the diversity of boundary conditions that guide the development of active margins and the key parameters that regulate their evolution in time and space.

View article: https://pubs.geoscienceworld.org/gsa/geosphere/article-abstract/doi/10.1130/GES02422.1/600741/Introduction-Active-Margins-in-Transition

Detrital zircon geochronology of modern river sediment in south-central Alaska: Provenance, magmatic, and tectonic insights into the Mesozoic and Cenozoic development of the southern Alaska convergent margin
Cooper R. Fasulo; Kenneth D. Ridgway

Abstract: New and previously published detrital zircon U-Pb ages from sediment in major rivers of south- central Alaska archive several major episodes of magmatism associated with the tectonic growth of this convergent margin. Analysis of detrital zircons from major trunk rivers of the Tanana, Matanuska-Susitna, and Copper River watersheds (N = 40, n = 4870) documents major View article: https://pubs.geoscienceworld.org/gsa/geosphere/article-abstract/doi/10.1130/GES02270.1/600742/Detrital-zircon-geochronology-of-modern-river

Low-temperature thermochronology constraints on the evolution of the Eastern Kunlun Range, northern Tibetan Plateau
Chen Wu; Jie Li; Lin Ding

Abstract: Signals of uplift and deformation across the Tibetan Plateau associated with the Cenozoic India-Asia collision can be used to test debated deformation mechanism(s) and the growth history of the plateau. The spatio-temporal evolution of the Eastern Kunlun Range in northern Tibet provides a window for understanding the intracontinental tectonic evolution of the region. The Eastern Kunlun Range exposes the Cenozoic Kunlun left-slip fault and kinematically linked thrust belts. In this contribution, integrated field observations and apatite fission-track thermochronology were conducted to constrain the initiation ages of localized thrust faults and the exhumation history of the Eastern Kunlun Range. Our analyses reveal four stages of cooling of the Eastern Kunlun Range. We relate these four stages to the following interpreted tectonic evolution: (1) an initial period of early Cretaceous cooling and slow exhumation over the early Cenozoic, which is associated with the formation of a regional unconformity observed between Cretaceous strata and early Cenozoic sediments; (2) rapid Oligocene cooling that occurred at the eastern domain of the Eastern Kunlun Range related to the southern Qaidam thrusts; (3) extensive rapid cooling since the early-middle Miocene in most of the eastern-central domains and significant uplift of the entire range; and (4) a final pulse of rapid late Miocene-to-present cooling associated with the initiation of the Kunlun left-slip fault and dip-slip shortening at the western and eastern termination of the left-slip fault. Early Cenozoic deformation was distributed along the northern extent of the Tibetan Plateau, and overprinting out-of-sequence deformation migrated back to the south with the initiation of Miocene-to-present deformation in the Eastern Kunlun Range.

View article: https://pubs.geoscienceworld.org/gsa/geosphere/article-abstract/doi/10.1130/GES02358.1/600735/Low-temperature-thermochronology-constraints-on

LA JOLLA--(June 30, 2021) Scientists--and gardeners--have long known that plants grow taller and flower sooner when they are shaded by close-growing neighbors. Now, for the first time, researchers at the Salk Institute have shown the detailed inner workings of this process.

The study, published June 17, 2021, in Nature Genetics, offers a new understanding of how gene activity directs plant growth, and how quickly plants respond to their environment--with shifting light conditions triggering molecular changes in as little as five minutes. The findings provide insights into how to increase yield and safeguard world food production as climate change shrinks the planet's arable land.

"This paper shows, in high resolution, how plants respond to subtle environmental changes on the cellular level," says co-corresponding author Joanne Chory, director of Salk's Plant Molecular and Cellular Biology Laboratory, Howard Hughes Medical Institute investigator, and holder of the Howard H. and Maryam R. Newman Chair in Plant Biology. "Work that reveals how plants can adapt to greater environmental stresses will be critical as the effects of climate change intensify."

Plants in the shade grow faster and taller in an effort to break through the canopy and reach more light. At the same time, shaded growing conditions cause them to flower and produce seeds earlier than normal, in order to out-compete other plants. These responses might be helpful to wildflowers growing in a meadow, but on farms they can reduce production and result in bitter, low-quality crops--as any gardener whose lettuce has bolted knows.

In the new study, researchers looked at the role of specific transcription factors in activating this growth response. Transcription factors are proteins that turn genes on or off by binding to DNA.

The team worked with mutant seedlings lacking transcription factors called PIFs (PHYTOCHROME-INTERACTING FACTORs). When they grew these plants in an environment that simulated shade, the plants without certain PIFs did not elongate or speed up their growth, but instead continued to grow normally as if they were in full sunlight. Previously, the Chory lab showed that PIF7 plays the most important role in regulating shade-induced growth.

The researchers then took a closer look at the role of histones in this process, in particular the histone variant H2A.Z. Histones are proteins that act like spools for strands of DNA. When histones are exchanged or modified, they can work to activate or suppress certain genes.

The scientists found that canopy shade led to the removal of the histone H2A.Z at growth-regulating genes through the DNA binding of PIF7, which in turn activated their expression.

By using very short time intervals for their experiments, the researchers found that PIF7 gets activated, binds its target genes, and initiates the removal of H2A.Z, all within the first 5 minutes of the plant experiencing canopy shade.

"Our study describes another step towards a mechanistic understanding of how plants alter their gene expression in response to a changing environment," says co-corresponding author Joseph Ecker, a Howard Hughes Medical Institute investigator and professor in Salk's Genomic Analysis Laboratory.

Previous studies had identified PIFs and H2A.Z as having important roles in the responses of plants exposed to high temperatures; however, the timing of events was not known, notes co-author Björn Willige, a Howard Hughes Medical Institute research specialist in the Chory lab.

"Our study reveals the mechanism in close detail and also shows the rapid nature of the response. We found that when PIF7 is active, it binds to DNA. And our data indicate that this leads to the removal of H2A.Z from the DNA. Subsequently, genes are activated, and then this induces growth, to outcompete the neighboring plants," Willige says.

The speed of the process was unexpected, says co-author Mark Zander, an assistant professor at the Waksman Institute of Microbiology at Rutgers University. He noted that, in addition to triggering the stress response within five minutes, the histone landscape also recovered quickly when shade was removed.

"When we removed shade, the levels of H2A.Z at PIF7 target genes went back to normal within 30 minutes," he says. "I was surprised by how dynamic the process is, which is really the foundation for the elegance of our study."

PIFs play significant roles in the growth, development and pest defense of plants. Therefore, the team hopes that their findings can be translated to other plant responses that are important for farmers, especially in relation to helping plants be more resilient to climate change. The Salk Institute's Harnessing Plants Initiative seeks to help solve climate change by optimizing plants' natural ability to capture and store carbon.

PULLMAN, Wash. - Fire can put a tropical songbird's sex life on ice.

Following habitat-destroying wildfires in Australia, researchers found that many male red-backed fairywrens failed to molt into their red-and-black ornamental plumage, making them less attractive to potential mates. They also had lowered circulating testosterone, which has been associated with their showy feathers.

For the study published in the Journal of Avian Biology, the researchers also measured the birds' fat stores and the stress hormone corticosterone but found those remained at normal levels.

"Really, it ended up all coming down to testosterone," said Jordan Boersma, Washington State University doctoral student and lead author on the study. "There's no evidence that the birds were actually stressed. Wildfire was just interfering with their normal, temporal pattern of elevating testosterone and then producing that colorful plumage."

While the findings are specific to this tropical songbird, they may have implications for other species that don special coloration for mating, Boersma added.

"It could be a good way to gauge how healthy a population is if you know their normal level of ornamentation," he said. "If you see that there are very few males undergoing that transition, then there is probably something in their environment that's not ideal."

Without the elevated testosterone, male red-backed fairywrens are not so red. Instead they have drab, brown feathers much like their female counterparts. Ornamental feathers can make them stand out to predators and cause conflict with competing males. As Boersma puts it, the flashy feathers are "costly." Their only advantage is in attracting female fairywrens.

"The females prefer to mate with a male fairywren who is prettier," Boersma said. "Testosterone is just one of the mechanisms that they use to get their ornamentation."

In an earlier study, Boersma and his colleagues showed that testosterone helps the fairywren process pigments in their diet called carotenoids to create their colorful feathers. This study adds further evidence of that connection as well as the birds' response to wildfire.

While other research has looked at how wildfire impacts long-term survival of birds and other animals, this is one of the few studies that look at how wildfire may affect the birds' physiology.

Red-backed fairywrens are used to living with periodic wildfires, and the researchers suspect that the suppression of testosterone is an evolved response. Wildfires can destroy the birds' grassland nesting habitat, so it is a signal that it might not good time to raise their young. The male birds then may inhibit or delay breeding by remaining brown and unattractive to mates.

For this study, the researchers observed and took blood samples from the fairywrens for five years at two different sites in the tropical northeast part of Queensland state in Australia. This allowed them to compare birds living at times and places that experienced wildfire with those that did not.

The male red-backed fairywrens typically wait for the monsoon season to molt into their bright colors when the rains bring more of the insects they eat out into the open. The researchers wanted to be sure it was the wildfire and not a dry season that was affecting their testosterone levels and feather color. During the study period, there was an unusually dry season, and the researchers observed minimal breeding among the birds, but yet the males were still producing ornamentation at a normal level. It was only post-fire that the many of the male birds stayed brown.

The researchers not only found that more males remained brown immediately following the wildfire event but also that the testosterone was lower in the brown males--and lower in the population at large relative to previous years without fires.

When it comes to climate change, not all organisms will lose out. A new Cal Poly study finds that rattlesnakes are likely to benefit from a warming climate.

A combination of factors makes a warming climate beneficial to rattlesnakes that are found in almost every part of the continental United States but are especially common in the Southwest.

Rattlers are experts at thermoregulation. Researchers found that, when given a choice, the snakes prefer a body temperature of 86-89 degrees Fahrenheit, a much warmer temperature than they generally experience in nature. The average body temperature of coastal rattlesnakes in the study was 70 degrees, and for inland rattlers it was 74 degrees Fahrenheit.

"We were surprised to see how much lower the body temperatures of wild snakes were relative to their preferred body temperatures in the lab," said Hayley Crowell, a graduate student researcher and project lead. "There are a lot of ecological pressures in nature that could prevent rattlesnakes from basking, such as the risk of increased exposure to predators. A warmer climate may help these snakes heat up to temperatures that are more optimal for digestion or reproduction."

Longer periods of warmer temperatures would also give rattlesnakes a longer active season, giving them more time to hunt and feed. Because snakes are ectothermic, or cold-blooded, they cannot regulate their body temperatures like warm-blooded animals. Instead, they rely on their surroundings to provide heat, which restricts their activity in cold weather.

In addition to seasonal changes, rattlers could spend more active hours during a given day.

A possible lack of prey -- rattlesnakes eat mostly rodents, but may also eat insects and other reptiles --resulting from a warming climate may not be a big problem for the snakes either.

The research team discovered that the snakes use energy extremely efficiently. To subsist, an adult male rattlesnake needs only 500-600 calories for an entire year, which is about one ground squirrel, the equivalent of only about half a large burrito. Though in the real world a rattler needs additional calories to hunt and bear young among other activities, the calculations point to the snakes' ability to survive even if prey isn't plentiful. Humans, by comparison, need about 1,300 times as many calories to survive.

"Rattlesnakes require very little energy to exist," said Crowell, who earned a master's degree in biological sciences at Cal Poly.

Rattlesnakes are widespread throughout California, and the seven species of these vipers in the Golden State can be found from the coast to the desert. An increase in the number of snakes could affect entire ecosystems. Rattlesnakes are a keystone predator for ground squirrels in California and are prey for raptors and many other animals.

"We are so used to climate change studies that forecast negative impacts on wildlife -- it was interesting to see such starkly different findings for these snakes," said Crowell, who is seeking a doctorate at the University of Michigan.

With advances in medical science driving progress against childhood brain tumors, today three out of four young patients survive at least five years beyond diagnosis. However, the outcomes look grim when malignant cells spread, or metastasize.

Such is the case with medulloblastoma, a type of brain cancer that arises in the cerebellum, at the back of the head. Although rare in absolute terms -- about 350 cases emerge each year, 60 percent of them in children -- medulloblastoma is the most common and deadliest form of pediatric brain cancer. Metastasis to the lining of the brain or spinal cord is responsible for virtually all deaths from the disease.

Now, research led by USC investigators has shined new light on how medulloblastoma travels to other sites within the central nervous system. The study, which appeared in the journal Cell Reports, showed that an enzyme called GABA transaminase, abbreviated as ABAT, aids metastases in surviving the hostile environment around the brain and spinal cord and in resisting treatment. These findings may provide clues to new strategies for targeting deadly medulloblastoma metastases.

"This is one of the first studies to focus on how medulloblastoma spreads through the perspective of neuroscience," said corresponding author Josh Neman, PhD, an assistant professor of neurosurgery and the scientific director of the USC Brain Tumor Center at the Keck School of Medicine of USC and a member of USC Norris Comprehensive Cancer Center. "These tumors are not only smart, but also utilize any means to grow. Now we know one key marker that the rogue cells use."

Brain cancer cells change to spread

Medulloblastoma faces a substantial challenge in spreading to other parts of the central nervous system. The cerebrospinal fluid that fills cavities inside the brain, as well as surrounding the brain and spinal cord, lacks nutrients for cancer cells to feed upon.

For what cerebrospinal fluid lacks in nutrients, it makes up in an abundance of an amino acid called GABA. GABA's primary purpose in the central nervous system is as a neurotransmitter that lessens the effects of other messenger molecules in the brain and spine. However, healthy neurons in the cerebellum also break GABA down for energy. The ABAT enzyme helps in the process.

The study led by Neman, his doctoral student Vahan Martirosian and their colleagues outlines how medulloblastoma metastases respond to the barren environment in cerebrospinal fluid by changing up their metabolism. The scientists showed that cells at the primary tumor site are low in ABAT compared to their neighbors in the brain, while traveling medulloblastoma cells are significantly higher in ABAT. The metastases avoid starvation by ramping up production of the ABAT enzyme so they can feed on GABA, in a sort of microscopic cloak-and-dagger exercise with deadly consequences.

Another effect of ABAT is to slow cell division. This turns out to be an advantage for the medulloblastoma metastases -- ironically, considering that cancer is characterized by out-of-control growth. Because radiotherapy and chemotherapy affect the fastest-growing cells in the body, increased ABAT helps the metastases go undercover and resist treatment.

"When tumor cells go quiet, they're very dangerous," Neman said. "Current therapies don't work perfectly on these quiet cancer cells -- and that is why they ultimately survive and spread."

Indeed, the researchers showed that ABAT-rich tumor cells were more resistant to cisplatin and vincristine, types of chemotherapy commonly used to treat medulloblastoma. And medulloblastoma cells were unable to spread to the linings of the brain and spine without ABAT.

A key comparison between cancerous and healthy brain cells

The Cell Reports study documents a chain of diligent investigations in which each answer led to an additional question that the researchers pursued. The paper reports on more than three dozen individual experiments designed to understand the metabolism, survival and proliferation of medulloblastoma cells. The scientists' methods ran the gamut from analyzing DNA and RNA datasets to studying the metabolism of cells grown in culture, from working with genetically engineered lab models to examining tumor samples donated by patients.

According to Neman, one particularly powerful tool his team used to understand the spread of medulloblastoma was the side-by-side comparison of cancerous cells with healthy brain cells of various types. In certain ways, the slow-growing metastases seemed to ape processes seen in neurons -- cells that do not divide and reproduce.

"Our approach was utilizing the emerging field called cancer neuroscience, where normal developmental neurobiology meets cancer biology," he said. "The ultimate quiet cell in the body is the neuron, and these cancer cells are using similar pathways to become rogue and survive."

As next steps in this line of inquiry, Neman is leading preclinical studies to test whether drugs that inhibit ABAT will halt medulloblastoma metastases. Meanwhile, his research group will delve into other elements of ABAT's role in the disease.

"With neuronal comparison, we're just hitting the tip of the iceberg," he said. "There are many more features of these dormant tumor cells that we haven't discovered yet."