The team focused on bananas, cassava, and cocoa pulp cultivated in soil affected by the disaster. They examined levels of cadmium, chromium, copper, nickel, and lead, metals linked to iron oxides, which are the primary component of the tailings. Their findings suggest that eating bananas grown in contaminated soil may present a potential health risk for children six years old and younger.

“Our group has been studying the impacts of the dam collapse for years. We obtained the first samples seven days after the accident and immediately understood that there was an imminent risk of contamination of plants, soil, water, and fish. But the question remained: Does this contamination pose a risk to human health?” recalls Tiago Osório, an agronomist and professor in the Department of Soil Science at the Luiz de Queiroz College of Agriculture at the University of São Paulo (ESALQ-USP).

The study, published in Environmental Geochemistry and Health, explains how plants absorb potentially toxic elements (PTEs) from mining waste and store them in edible tissues. It also outlines how these substances can move into the human food supply. The research forms part of Amanda Duim’s doctoral work at ESALQ. Her thesis has produced seven international publications and earned two major awards in 2025: the USP Thesis Award in Sustainability and the Capes Thesis Award, granted by the Brazilian Ministry of Education’s Coordination for the Improvement of Higher Education Personnel (CAPES). Duim received support from FAPESP through a doctoral scholarship.

How Contaminated Soil Transfers Metals Into Plants

Duim, the study’s lead author, says the research stands out because it directly links human health risk to the movement of PTEs from soil into crops. “The iron oxide content in the soil, which is the main constituent of the tailings, correlates with its content in the plant. We studied the passage of constituents from the tailings in the soil to the water, and then from the water to the plant, including its leaves and fruits.”

“First, we need to know which elements are there and in what quantities in order to understand the biochemical dynamics of their release,” Osório explains.

Duim began her doctoral research in 2019 by exploring whether plants from flood-prone areas could help restore contaminated environments. She evaluated both cultivated crops and native species. “We evaluated cultivated and native species. In the case of the latter, we wanted to know how they affect the dissolution of iron oxide and, in this process, understand if and how the PTEs associated with this waste enter the plant, since different species accumulate PTEs differently,” she says. “The idea was to find the best native species for cleaning up contaminated environments, and we found more than one species that can fulfill this function, with results already published. In the case of cultivated species, we wanted to know if PTEs would be transferred to the fruits and edible parts of the plants.”

To measure contamination, the researchers carefully collected soil and plant samples. They washed and weighed the fresh plants, then dried them and weighed them again. Roots, stems, leaves, and peeled fruits were ground separately for analysis. “We dissolved the ‘plant powder,’ transforming it into a solution using various acids, and determined the concentration in the solution. We converted the calculation of the concentration of material in the solution and compared it with the weight of the diluted material, thus obtaining the PTE concentration in milligrams per kilogram of dry biomass,” Duim describes.

In bananas and cassava, nearly all PTEs except chromium were found in higher amounts below ground, in roots and tubers. Cocoa behaved differently, with elevated levels in stems, leaves, and fruits. In cocoa pulp, copper and lead concentrations exceeded limits set by the Food and Agriculture Organization of the United Nations (FAO).

When the team discovered that some edible portions contained PTE levels above recommended standards, they conducted a formal health risk assessment.

Health Risk Assessment for Children and Adults

The scientists calculated the risk quotient (RQ), risk index (RI), and total risk index (TRI) for people consuming bananas, cassava rhizomes, and cocoa pulp. They evaluated children (under six years of age) and adults (over 18 years of age) separately. The RQ compares a person’s estimated daily intake of a substance to a reference dose considered safe. The TRI helps determine potential non-carcinogenic health risk from exposure to PTEs. A TRI below 1 indicates low risk.

“These elements exist naturally in the environment. We’re exposed to them in lower concentrations. But in the case of a disaster like the one in Mariana, when exposure is expected to increase, we need to exercise extra caution,” says Tamires Cherubin, a health sciences Ph.D. and co-author of the study. Standard methods evaluate how bioavailable these elements are, since certain concentrations can lead to kidney and heart problems, gastrointestinal discomfort, and lung damage if inhaled. Short-term effects may also include skin irritation and eye problems.

The researchers factored in how much locally grown food residents consume, using data from the Brazilian Institute of Geography and Statistics (IBGE). They also considered how long individuals might be exposed, differences in body weight between children and adults, and the time required for harmful effects to develop.

“According to the reference daily intake doses for contaminants covered by the literature, we consider the limits of 0.05 mg/kg^-1 for the presence of cadmium in fruits and 0.1 mg/kg^-1 in tubers, 0.5-1.0 mg/kg^-1 for the presence of chromium, 20.0 mg/kg^-1 for copper, 0.5-1.0 mg/kg^-1 for nickel, 0.8-2.3 mg/kg^-1 for lead, and 50.0 mg/kg-¹ for zinc,” Cherubin explains.

For most metals, TRI values were below 1, indicating no significant non-carcinogenic risk for adults consuming these foods from the Doce River estuary. However, the TRI for bananas exceeded 1 for children, signaling possible health concerns. Elevated lead levels were the primary driver, and cadmium concentrations in bananas also surpassed FAO recommendations. The researchers note that long-term exposure to lead, even at low levels, can permanently affect brain development, potentially lowering IQ and contributing to attention and behavioral problems.

Long-Term Cancer Concerns and Ongoing Exposure

The team cautions that eating food grown in contaminated soil over many years could lead to cumulative effects. “Over time, considering the life expectancy in Brazil of around 75 years, there may be a carcinogenic risk since there’s a possibility of direct and indirect DNA damage,” says Cherubin. Such genetic damage may increase the likelihood of cancers affecting the central nervous system, digestive tract, and blood-forming tissues. “It all depends on the human body’s ability to absorb and metabolize these elements that are available in the environment,” she adds.

The work builds on a fresh investigation of a famous Upper Paleolithic burial discovered in 1963 at Grotta del Romito in southern Italy. For decades, the site intrigued scientists because of unusual skeletal traits and the way the two individuals were laid to rest. Researchers long questioned how the pair were related and whether a medical condition explained their short stature.

Ice Age Double Burial Raises New Questions

The two individuals were buried in an embrace. “Romito 2,” a young person with notably shortened limbs who was once believed to be male, rested in the arms of “Romito 1,” thought to be an adult female. There were no signs of injury. Romito 2 stood about 110 cm (3’7″) tall, a height consistent with a rare skeletal disorder called acromesomelic dysplasia, although bones alone could not confirm that diagnosis. Romito 1 was also shorter than average for that time period at roughly 145 cm (4’9″). Over the years, experts debated their sex, their relationship, and whether the same condition might explain both of their statures.

To investigate further, scientists extracted ancient DNA from the petrous portion of the temporal bone in both skeletons, an area known for preserving genetic material. The results showed the two were first-degree relatives. The team then examined genes involved in bone growth and compared the detected variants with modern medical data. This collaborative effort brought together paleogenomics, clinical genetics, and physical anthropology, with researchers from the University of Vienna working alongside colleagues in Italy, Portugal, and Belgium.

Earliest Known Genetic Diagnosis in Humans

Genetic testing revealed that both individuals were female and closely related, most likely a mother and daughter. In Romito 2, researchers found a homozygous mutation in the NPR2 gene, which plays a key role in bone development. This provided clear evidence of acromesomelic dysplasia, Maroteaux type — a very rare inherited disorder characterized by severe short stature and significant shortening of the limbs.

Romito 1 carried a single altered copy of the same gene. That genetic pattern is associated with a milder form of short stature, explaining the difference in height between the two women.

Rare Genetic Diseases Deep in Human History

Ron Pinhasi, University of Vienna, who co-led the study says: “By applying ancient DNA analysis, we can now identify specific mutations in prehistoric individuals. This helps establish how far back rare genetic conditions existed and may also uncover previously unknown variants.”

Daniel Fernandes of the University of Coimbra, first author of the study, adds: “Identifying both individuals as female and closely related turns this burial into a familial genetic case. The older woman’s milder short stature likely reflects a heterozygous mutation, showing how the same gene affected members of a prehistoric family differently.”

The findings underscore that rare genetic diseases are not limited to modern populations. Adrian Daly of Liège University Hospital Centre, a co-leader of the study, notes: “Rare genetic diseases are not a modern phenomenon but have been present throughout human history. Understanding their history may help recognising such conditions today.”

Evidence of Social Care in the Ice Age

Despite serious physical challenges, Romito 2 lived into adolescence or adulthood. Her survival suggests she received consistent support from her community. Alfredo Coppa of Sapienza University of Rome, who also co-led the study, says: “We believe her survival would have required sustained support from her group, including help with food and mobility in a challenging environment.”

Key Findings

• Ancient DNA analysis revealed that two individuals buried together in southern Italy were closely related — most likely mother and daughter.
• In the younger individual, two altered copies of the NPR2 gene confirmed acromesomelic dysplasia (Maroteaux type), a condition marked by severe short stature and pronounced limb shortening; the older individual carried one altered copy linked to milder short stature.
• The findings show that rare genetic diseases were already present in prehistoric populations and can now be studied using paleogenomics.
• The younger individual’s survival despite severe physical limitations suggests sustained care and social support within her community.

During the survey, researchers identified a promising 8.19-millisecond pulsar (MSP) candidate located close to Sagittarius A*, the supermassive black hole at the center of our galaxy.

A Potential Tool for Testing Einstein’s General Relativity

If astronomers can confirm the object and precisely measure the timing of its pulses, it could create a rare opportunity to test General Relativity under extreme conditions. Tracking a pulsar in this environment would allow scientists to make highly accurate measurements of space-time around a supermassive black hole.

Pulsars are dense remnants of massive stars known as neutron stars. They spin rapidly and generate intense magnetic fields, producing focused beams of radio waves that sweep across space like the beam of a lighthouse.

When undisturbed by outside forces, the radio pulses from a pulsar reach Earth with remarkable consistency. Because of this steady rhythm, pulsars function like highly reliable cosmic clocks. Millisecond pulsars spin especially fast, which makes their timing behavior even more stable and predictable.

How Gravity Can Distort a Pulsar’s Signal

“Any external influence on a pulsar, such as the gravitational pull of a massive object, would introduce anomalies in this steady arrival of pulses, which can be measured and modeled,” said Slavko Bogdanov, a research scientist at the Columbia Astrophysics Laboratory who was a co-author on the study. “In addition, when the pulses travel near a very massive object, they may be deflected and experience time delays due to the warping of space-time, as predicted by Einstein’s General Theory of Relativity.”

Sagittarius A* contains about 4 million times the mass of the Sun, giving it a powerful gravitational reach that strongly affects nearby objects.

Follow Up Observations Underway

Because of the possible scientific significance, researchers are now analyzing additional follow up observations to determine whether the pulsar candidate is genuine.

To encourage broader scientific collaboration, Breakthrough Listen is making the data publicly available. This allows research teams around the world to conduct their own independent analyses and explore related scientific questions.

“We’re looking forward to what follow-up observations might reveal about this pulsar candidate,” Perez said. “If confirmed, it could help us better understand both our own Galaxy, and General Relativity as a whole.”

Toxoplasma gondii is a potentially dangerous parasite that infects warm blooded animals. People are most often exposed through contact with cats, contaminated fruits or vegetables, or undercooked meat. After entering the body, the parasite can spread to multiple organs and eventually settle in the brain, where it can remain for life. Roughly one third of the global population is believed to carry Toxoplasma, yet most people never develop symptoms. When illness does occur, known as toxoplasmosis, it is most serious in individuals with weakened immune systems.

Researchers led by Tajie Harris, PhD, set out to understand how the immune system responds when Toxoplasma invades CD8+ T cells, which are specialized immune cells responsible for killing infected cells.

“We know that T cells are really important for combatting Toxoplasma gondii, and we thought we knew all the reasons why. T cells can destroy infected cells or cue other cells to destroy the parasite. We found that these very T cells can get infected, and, if they do, they can opt to die. Toxoplasma parasites need to live inside cells, so the host cell dying is game over for the parasite,” said Harris, the director of the Center for Brain Immunology and Glia (BIG Center) at the University of Virginia School of Medicine. “Understanding how the immune system fights Toxoplasma is important for several reasons. People with compromised immune systems are vulnerable to this infection, and now we have a better understanding of why and how we can help patients fight this infection.”

Caspase-8 and the Self-Destruct Defense

Harris and her team discovered that CD8+ T cells rely on a powerful enzyme called caspase-8 to control T. gondii. Caspase-8 plays a central role in regulating immune responses and can trigger a process that causes a cell to self-destruct.

In laboratory experiments, mice that lacked caspase-8 in their T cells developed far higher levels of T. gondii in their brains compared to mice whose T cells produced the enzyme. This happened even though both groups mounted strong immune responses against the infection.

The difference in outcomes was striking. Mice with caspase-8 remained healthy, while those without it became severely ill and died. Examination of their brain tissue showed that their CD8+ T cells were much more likely to be infected by the parasite.

These findings indicate that caspase-8 plays a crucial role in limiting T. gondii inside T cells. The results also add to growing evidence that this enzyme is broadly important in helping the body control infectious threats.

“We scoured the scientific literature to find examples of pathogens infecting T cells. We found very few examples,” said Harris, part of UVA’s Department of Neuroscience. “Now, we think we know why. Caspase-8 leads to T cell death. The only pathogens that can live in CD8+ T cells have developed ways to mess with Caspase-8 function. Prior to our study, we had no idea that Caspase-8 was so important for protecting the brain from Toxoplasma.”

Study Details and Funding

The findings were published in the journal Science Advances. The research team included Lydia A. Sibley, Maureen N. Cowan, Abigail G. Kelly, NaaDedee A. Amadi, Isaac W. Babcock, Sydney A. Labuzan, Michael A. Kovacs, Samantha J. Batista, John R. Lukens and Harris. The scientists reported no financial conflicts of interest.

Funding for the research came from the National Institutes of Health, grants R01NS112516, R01NS134747, R21NS12855, T32GM008715, T32AI007496, T32AI007046, T32NS115657, F30AI154740, T32AI007496 and T32GM007267; a University of Virginia Pinn Scholars Award; a UVA Shannon Fellowship; and UVA’s Strategic Investment Fund.

In the new research, the team worked with human spinal cord organoids — miniature organs derived from stem cells — to recreate different forms of spinal cord trauma and evaluate a promising regenerative treatment.

For the first time, researchers showed that these human spinal cord organoids can faithfully reproduce the major biological consequences of spinal cord injury. The model displayed cell death, inflammation, and glial scarring, which is a thick buildup of scar tissue that forms a physical and chemical barrier preventing nerve repair.

When the damaged organoids were treated with “dancing molecules” — a therapy that restored movement and repaired tissue in a previous animal study — the results were dramatic. The injured tissue produced substantial neurite outgrowth, meaning the long extensions that allow neurons to communicate began growing again. Scar like tissue was greatly reduced. The findings add support to the idea that this therapy, which recently received Orphan Drug Designation from the U.S. Food and Drug Administration (FDA), could improve recovery for people with spinal cord injuries.

The study was published on Feb. 11 in Nature Biomedical Engineering.

“One of the most exciting aspects of organoids is that we can use them to test new therapies in human tissue,” said Northwestern’s Samuel I. Stupp, the study’s senior author and inventor of dancing molecules. “Short of a clinical trial, it’s the only way you can achieve this objective. We decided to develop two different injury models in a human spinal cord organoid and test our therapy to see if the results resembled what we previously saw in the animal model. After applying our therapy, the glial scar faded significantly to become barely detectable, and we saw neurites growing, resembling the axon regeneration we saw in animals. This is validation that our therapy has a good chance of working in humans.”

Stupp is a leader in regenerative materials science and holds the title of Board of Trustees Professor of Materials Science and Engineering, Chemistry, Medicine and Biomedical Engineering at Northwestern. He has appointments in the McCormick School of Engineering, Weinberg College of Arts and Sciences and Feinberg School of Medicine, and directs the Center for Regenerative Nanomedicine (CRN). The paper’s first author is Nozomu Takata, a research assistant professor of medicine at Feinberg and member of CRN.

Why Human Organoids Matter

Organoids are grown from induced pluripotent stem cells in the laboratory. Although they are simplified versions of full organs, they closely resemble real tissue in structure, cellular diversity, and function. Because of this, organoids are powerful tools for studying disease, testing treatments, and exploring how organs develop. They also allow researchers to move faster and at lower cost compared to animal experiments or human clinical trials.

While other groups have produced spinal cord organoids to study basic biology, this model represents a major advance for injury research. The organoids measured several millimeters across and were mature enough to sustain and model traumatic damage.

Over several months, the team guided stem cells to form complex spinal cord tissue containing neurons and astrocytes. They also became the first to incorporate microglia — immune cells found in the central nervous system — to better replicate the inflammatory response that follows spinal cord injury.

“It’s kind of a pseudo-organ,” Stupp said. “We were the first to introduce microglia into a human spinal cord organoid, so that was a huge accomplishment. It means that our organoid has all the chemicals that the resident immune system produces in response to an injury. That makes it a more realistic, accurate model of spinal cord injury.”

What Are Dancing Molecules

Once the spinal cord organoids were fully developed, the researchers turned their attention to testing injury and treatment. First introduced in 2021, the dancing molecules therapy uses controlled molecular motion to repair tissue and potentially reverse paralysis after traumatic spinal cord injury. It belongs to a broader class of supramolecular therapeutic peptides (STPs), which rely on large assemblies of 100,000 or more molecules to activate cell receptors and stimulate the body’s natural repair signals. (The concept of supramolecular therapies also is used in current GLP-1 drugs for weight loss and diabetes, an area that Stupp’s lab investigated nearly 15 years ago.)

The therapy is delivered as a liquid injection that quickly forms a web of nanofibers resembling the spinal cord’s extracellular matrix. By adjusting how dynamically the molecules move within this structure, researchers improved how effectively they interact with constantly shifting cell receptors.

“Given that cells themselves and their receptors are in constant motion, you can imagine that molecules moving more rapidly would encounter these receptors more often,” Stupp said in 2021. “If the molecules are sluggish and not as ‘social,’ they may never come into contact with the cells.”

In previous animal experiments, a single injection given 24 hours after a severe injury enabled mice to walk again within four weeks. Formulations with faster molecular motion performed better than slower versions, suggesting that increased movement enhances bioactivity and cellular signaling.

Simulating Spinal Cord Trauma

To test the therapy, the researchers created two common types of spinal cord injury in the organoids. Some were cut with a scalpel to mimic a laceration similar to a surgical wound. Others were subjected to a compressive contusion injury, comparable to trauma from a serious car crash or fall.

Both types of injury led to cell death and the formation of glial scars — just as occurs in real spinal cord injury.

“We could distinguish between the astrocytes that are a part of normal tissue and the astrocytes in the glial scar, which are large and very densely packed,” Stupp said. “We also detected the production of chondroitin sulfate proteoglycans, which are molecules in the nervous system that respond to injury and disease.”

After treatment with dancing molecules, the gelled nanofiber scaffold reduced inflammation, shrank glial scarring, stimulated neurite extension, and encouraged neurons to grow in organized patterns.

Neurites include axons, which are often severed in spinal cord injuries. When axons are cut, communication between neurons is disrupted, leading to paralysis and loss of sensation below the injury site. Promoting neurite regrowth could reconnect these pathways and help restore function.

The Role of Molecular Motion

Stupp credits the therapy’s effectiveness to supramolecular motion, meaning the ability of the molecules to move rapidly and even briefly detach from the nanofiber network. Experiments on healthy organoids reinforced this idea.

“Before we even developed the injury model, we tested the therapy on a healthy organoid,” he said. “The dancing molecules spun out all these long neurites on the surface of the organoid but, when we used molecules that had less or no motion, we saw nothing. This difference was very vivid.”

Looking ahead, the team plans to engineer even more advanced organoids to refine their models. They also intend to develop versions that replicate chronic, long standing injuries, which typically involve thicker and more persistent scar tissue. With further development, Stupp said these miniature spinal cords could contribute to personalized medicine by generating implantable tissue from a patient’s own stem cells, reducing the risk of immune rejection.

The study, “Injury and therapy in a human spinal cord organoid,” was supported by the Center for Regenerative Nanomedicine at Northwestern University and a gift from the John Potocsnak Family for spinal cord injury research.

Compulsive behaviors appear in a range of mental health conditions, including obsessive-compulsive disorder, substance use disorders, and gambling disorder. In these conditions, people continue repeating certain actions even when they lead to harmful consequences. Millions of people worldwide are affected.

How Habits and Self-Control Normally Work

Senior author Dr. Laura Bradfield, a behavioral neuroscientist, explained that habits serve an important purpose. They allow us to run on autopilot during routine tasks like brushing our teeth or driving along a familiar road, freeing up mental energy for other thoughts.

“However, if we are driving and a child steps onto the road, then we suddenly become aware of our surroundings and focus on what we are doing. This involves taking back conscious control, thinking about possible outcomes and adjusting our behavior,” said Dr. Bradfield.

In compulsive behaviors such as repeated handwashing or playing poker machines, the prevailing theory has been that these actions become deeply ingrained habits. According to this view, the behavior runs automatically, making it hard for people to regain cognitive control.

“Brain imaging studies show it’s common for people with compulsive disorders to have inflammation in the striatum, a brain region involved in choosing actions, so we decided to test whether inducing inflammation in this region in rats would increase habitual behavior.”

Brain Inflammation and Decision-Making

The study was led by Dr. Arvie Abiero during his PhD research at UTS and was recently published in Neuropsychopharmacology. The researchers examined how rats learn behaviors and how they regulate their actions. When inflammation was triggered in the striatum, the results were unexpected. Instead of becoming more automatic or habit-driven, the rats showed more deliberate and effortful decision-making.

“Surprisingly, the animals became more goal-directed and continued to adjust their behavior based on outcomes, even in situations where habits would normally take over,” said Dr. Bradfield.

The Role of Astrocytes in Compulsive Behavior

The team traced these changes to astrocytes, star-shaped cells in the brain that support neurons. When inflammation occurred, astrocytes multiplied and disrupted nearby neural circuits that control movement and decision-making.

These findings could have important implications for psychologists, psychiatrists, patients, and caregivers who work with compulsive disorders. Rather than reflecting a loss of control due to runaway habits, some compulsive behaviors may result from excessive, though misdirected, deliberate control.

The researchers suggest that medications aimed at astrocytes or treatments that reduce neuroinflammation may provide new therapeutic options. Broader anti-inflammatory strategies, such as regular exercise or improved sleep, could also play a role.

“There’s a lot of compulsive behavior that doesn’t fit neatly into the habit hypothesis. If someone is continually washing their hands because they are worried about germs, they are not doing this without thinking, they are consciously choosing to make that effort,” said Dr. Bradfield.

“Our findings offer a new explanation for these behaviors, which goes against the accepted view. Based on this, it’s possible that new treatments and interventions can be developed that more effectively treat these diseases and disorders,” she said.