By Amber Dance Billions of cells die in your body every day. Some go out with a bang, others with a whimper. They can die by accident if they’re injured or infected. Alternatively, should they outlive their natural lifespan or start to fail, they can carefully arrange for a desirable demise, with their remains neatly tidied away. Originally, scientists thought those were the only two ways an animal cell could die, by accident or by that neat-and-tidy version. But over the past couple of decades, researchers have racked up many more novel cellular death scenarios, some specific to certain cell types or situations. Understanding this panoply of death modes could help scientists save good cells and kill bad ones, leading to treatments for infections, autoimmune diseases and cancer. “There’s lots and lots of different flavors here,” says Michael Overholtzer, a cell biologist at Memorial Sloan Kettering Cancer Center in New York. He estimates that there are now more than 20 different names to describe cell death varieties. The identification of new forms of cell death has sped up in recent years. Lots of bad things can happen to cells: They get injured or burned, poisoned or starved of oxygen, infected by microbes or otherwise diseased. When a cell dies by accident, it’s called necrosis. There are several necrosis types, none of them pretty: In the case of gangrene, when cells are starved for blood, cells rot away. In other instances, dying cells liquefy, sometimes turning into yellow goop. Lung cells damaged by tuberculosis turn smushy and white — the technical name for this type, “caseous” necrosis, literally means “cheese-like.” Any form of death other than necrosis is considered “programmed,” meaning it’s carried out intentionally by the cell because it’s damaged or has outlived its usefulness.

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 13: Memory and Learning
Link ID: 29495 - Posted: 09.28.2024

Jon Hamilton For 22 years, Jason Mazzola’s life was defined by Fragile X, a genetic condition that often causes autism and intellectual disability. Jason, who is 24 now, needed constant supervision. He had disabling anxiety, and struggled to answer even simple questions. All that began to change when he started taking an experimental drug called zatolmilast in May of 2023. “It helps me focus a lot, helps me get more confident, more educated,” Jason says. His mother, Lizzie Mazzola, credits zatolmilast with transforming her son. “I have a different child in my house,” she says. “He gets himself to work, he walks downtown, gets his haircut, gets lunch. He wouldn't have done any of that before.” Other parents of children with Fragile X are also reporting big changes with zatolmilast. Those anecdotes are supported by data. A 2021 study of 30 adult male participants with Fragile X found that taking zatolmilast for 12 weeks improved performance on a range of memory and language measures. Now, two larger studies are underway that will determine whether zatolmilast becomes the first drug approved by the Food and Drug Administration to treat Fragile X. Mazzola realized early on that Jason was falling behind. “He could hardly talk by three,” she says. “At four he started to put some words together, but really wasn’t talking in sentences.” Genetic tests revealed the cause: Fragile X. The inherited condition affects the X chromosome, making one segment appear fragile or broken. This anomaly blocks production of a protein that’s important to brain development. © 2024 npr

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 13: Memory and Learning
Link ID: 29492 - Posted: 09.25.2024

By Max Kozlov A low-cost diabetes drug slows ageing in male monkeys and is particularly effective at delaying the effects of ageing on the brain, finds a small study that tracked the animals for more than three years1. The results raise the possibility that the widely used medication, metformin, could one day be used to postpone ageing in humans. Monkeys that received metformin daily showed slower age-associated brain decline than did those not given the drug. Furthermore, their neuronal activity resembled that of monkeys about six years younger (equivalent to around 18 human years) and the animals had enhanced cognition and preserved liver function. This study, published in Cell on 12 September, helps to suggest that, although dying is inevitable, “ageing, the way we know it, is not”, says Nir Barzilai, a geroscientist at the Albert Einstein College of Medicine in New York City, who was not involved in the study. Metformin has been used for more than 60 years to lower blood-sugar levels in people with type 2 diabetes — and is the second most-prescribed medication in the United States. The drug has long been known to have effects beyond treating diabetes, leading researchers to study it against conditions such as cancer, cardiovascular disease and ageing. Data from worms, rodents, flies and people who have taken the drug for diabetes suggest the drug might have anti-ageing effects. But its effectiveness against ageing had not been tested directly in primates, and it is unclear whether its potential anti-ageing effects are achieved by lowering blood sugar or through a separate mechanism. This led Guanghui Liu, a biologist who studies ageing at the Chinese Academy of Sciences in Beijing, and his colleagues to test the drug on 12 elderly male cynomolgus macaques (Macaca fasciucularis); another 16 elderly monkeys and 18 young or middle-aged animals served as a control group. Every day, treated monkeys received the standard dose of metformin that is used to control diabetes in humans. The animals took the drug for 40 months, which is equivalent to about 13 years for humans. © 2024 Springer Nature Limited

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 13: Homeostasis: Active Regulation of the Internal Environment
Related chapters from MM:Chapter 13: Memory and Learning; Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 29481 - Posted: 09.14.2024

By Carl Zimmer The human brain, more than any other attribute, sets our species apart. Over the past seven million years or so, it has grown in size and complexity, enabling us to use language, make plans for the future and coordinate with one another at a scale never seen before in the history of life. But our brains came with a downside, according to a study published on Wednesday. The regions that expanded the most in human evolution became exquisitely vulnerable to the ravages of old age. “There’s no free lunch,” said Sam Vickery, a neuroscientist at the Jülich Research Center in Germany and an author of the study. The 86 billion neurons in the human brain cluster into hundreds of distinct regions. For centuries, researchers could recognize a few regions, like the brainstem, by hallmarks such as the clustering of neurons. But these big regions turned out to be divided into smaller ones, many of which were revealed only with the help of powerful scanners. As the structure of the human brain came into focus, evolutionary biologists became curious about how the regions evolved from our primate ancestors. (Chimpanzees are not our direct ancestors, but both species descended from a common ancestor about seven million years ago.) The human brain is three times as large as that of chimpanzees. But that doesn’t mean all of our brain regions expanded at the same pace, like a map drawn on an inflating balloon. Some regions expanded only a little, while others grew a lot. Dr. Vickery and his colleagues developed a computer program to analyze brain scans from 189 chimpanzees and 480 humans. Their program mapped each brain by recognizing clusters of neurons that formed distinct regions. Both species had 17 brain regions, the researchers found. © 2024 The New York Times Company

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 13: Memory and Learning
Link ID: 29459 - Posted: 08.31.2024

By Julian Nowogrodzki A newly devised ‘brain clock’ can determine whether a person’s brain is ageing faster than their chronological age would suggest1. Brains age faster in women, countries with more inequality and Latin American countries, the clock indicates. “The way your brain ages, it’s not just about years. It’s about where you live, what you do, your socio-economic level, the level of pollution you have in your environment,” says Agustín Ibáñez, the study’s lead author and a neuroscientist at Adolfo Ibáñez University in Santiago. “Any country that wants to invest in the brain health of the people, they need to address structural inequalities.” The work is “truly impressive”, says neuroscientist Vladimir Hachinski at Western University in London, Canada, who was not involved in the study. It was published on 26 August in Nature Medicine. Only connect The researchers looked at brain ageing by assessing a complex form of functional connectivity, a measure of the extent to which brain regions are interacting with one another. Functional connectivity generally declines with age. The authors drew on data from 15 countries: 7 (Mexico, Cuba, Colombia, Peru, Brazil, Chile and Argentina) that are in Latin America or the Caribbean and 8 (China, Japan, the United States, Italy, Greece, Turkey, the United Kingdom and Ireland) that are not. Of the 5,306 participants, some were healthy, some had Alzheimer’s disease or another form of dementia and some had mild cognitive impairment, a precursor to dementia. The researchers measured participants’ resting brain activity — that when they were doing nothing in particular — using either functional magnetic resonance imaging (fMRI) or electroencephalography (EEG). The first technique measures blood flow in the brain, and the second measures brain-wave activity. © 2024 Springer Nature Limited

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 13: Memory and Learning; Chapter 11: Emotions, Aggression, and Stress
Link ID: 29458 - Posted: 08.31.2024

By Michael Eisenstein An analysis of almost 50,000 brain scans1 has revealed five distinct patterns of brain atrophy associated with ageing and neurodegenerative disease. The analysis has also linked the patterns to lifestyle factors such as smoking and alcohol consumption, as well as to genetic and blood-based markers associated with health status and disease risk. The work is a “methodological tour de force” that could greatly advance researchers’ understanding of ageing, says Andrei Irimia, a gerontologist at the University of Southern California in Los Angeles, who was not involved in the work. “Prior to this study, we knew that brain anatomy changes with ageing and disease. But our ability to grasp this complex interaction was far more modest.” The study was published on 15 August in Nature Medicine. Ageing can induce not only grey hair, but also changes in brain anatomy that are visible on magnetic resonance imaging (MRI) scans, with some areas shrivelling or undergoing structural alterations over time. But these transformations are subtle. “The human eye is not able to perceive patterns of systematic brain changes” associated with this decline, says Christos Davatzikos, a biomedical-imaging specialist at the University of Pennsylvania in Philadelphia and an author of the paper. Previous studies have shown that machine-learning methods can extract the subtle fingerprints of ageing from MRI data. But these studies were often limited in scope and most included data from a relatively small number of people. © 2024 Springer Nature Limited

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 13: Memory and Learning; Chapter 2: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Link ID: 29446 - Posted: 08.21.2024

By Lara Lewington, It's long been known that our lifestyles can help to keep us healthier for longer. Now scientists are asking whether new technology can also help slow down the ageing process of our brains by keeping track of what happens to them as we get older. One sunny morning, 76-year-old Dutch-born Marijke and her husband Tom welcomed me in for breakfast at their home in Loma Linda, an hour east of Los Angeles. Oatmeal, chai seeds, berries, but no processed sugary cereal or coffee were served - a breakfast as pure as Loma Linda’s mission. Loma Linda has been identified as one of the world’s so-called Blue Zones, places where people have lengthier-than-average lifespans. In this case, it is the city’s Seventh-Day Adventist Church community who are living longer. They generally don’t drink alcohol or caffeine, stick to a vegetarian or even vegan diet and consider it a duty of their religion to look after their bodies as best they can. This is their “health message”, as they call it, and it has put them on the map - the city has been the subject of decades of research into why its residents live better for longer. Dr Gary Fraser from the University of Loma Linda told me members of the Seventh-Day Adventist community there can expect not only a longer lifespan, but an increased “healthspan” - that is, time spent in good health - of four to five years extra for women and seven years extra for men. Marijke and Tom had moved to the city later in life, but both were now firmly embedded in the community. Copyright 2024 BBC.

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 13: Memory and Learning; Chapter 13: Memory and Learning
Link ID: 29391 - Posted: 07.13.2024

By Charles Q. Choi Chimeroids—brain organoids grown from the cells of multiple people—offer scientists a novel way to compare individual differences in response to drugs, infections or pathogenic variants, according to a new study in Nature. “The possibilities are endless,” says lead investigator Paola Arlotta, professor and chair of stem cell and regenerative biology at Harvard University. The approach overcomes a longstanding issue that has plagued any comparison of organoids derived from different people: Disparities between the organoids might reflect genetic dissimilarities between individual people but could also result just from inadvertent variations in how each organoid was grown, says Aparna Bhaduri, assistant professor of biological chemistry at the University of California, Los Angeles, who did not contribute to the new study. Mixing cells from multiple donors into a single organoid makes it possible to grow all the cells under the same conditions and makes it more likely that any differences seen between the cells are rooted in genetic variations between the people, Bhaduri says. Initially, Arlotta’s team tried to produce chimeroids by mixing pluripotent stem cells from multiple donors. But one person’s cells usually outgrew the others to make up most of each organoid. Even small differences in the stem cells’ extremely high growth rates easily led one person’s cells to overshadow the others, the team noted. So instead, the researchers grew the stem cells independently in organoids until they began to proliferate more slowly as neural stem cells or neural progenitor cells. They then broke these organoids apart and mixed them together, producing the chimeroids that developed with balanced numbers of up to five donors’ cells. Each cell line in the chimeroids could produce all the cell types normally found in the cerebral cortex, Arlotta and her colleagues discovered using DNA and RNA sequencing techniques. © 2024 Simons Foundation

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 13: Memory and Learning
Link ID: 29381 - Posted: 07.06.2024

By Paula Span About a month ago, Judith Hansen popped awake in the predawn hours, thinking about her father’s brain. Her father, Morrie Markoff, was an unusual man. At 110, he was thought to be the oldest in the United States. His brain was unusual, too, even after he recovered from a stroke at 99. Although he left school after the eighth grade to work, Mr. Markoff became a successful businessman. Later in life, his curiosity and creativity led him to the arts, including photography and sculpture fashioned from scrap metal. He was a healthy centenarian when he exhibited his work at a gallery in Los Angeles, where he lived. At 103, he published a memoir called “Keep Breathing.” He blogged regularly, pored over The Los Angeles Times daily, discussed articles in Scientific American and followed the national news on CNN and “60 Minutes.” Now he was nearing death, enrolled in home hospice care. “In the middle of the night, I thought, ‘Dad’s brain is so great,’” said Ms. Hansen, 82, a retired librarian in Seattle. “I went online and looked up ‘brain donation.’” Her search led to a National Institutes of Health web page explaining that its NeuroBioBank, established in 2013, collected post-mortem human brain tissue to advance neurological research. Through the site, Ms. Hansen contacted the nonprofit Brain Donor Project. It promotes and simplifies donations through a network of university brain banks, which distribute preserved tissue to research teams. Tish Hevel, the founder of the project, responded quickly, putting Ms. Hansen and her brother in touch with the brain bank at the University of California, Los Angeles. Brain donors may have neurological and other diseases, or they may possess healthy brains, like Mr. Markoff’s. “We’re going to learn so much from him,” Ms. Hevel said. “What is it about these superagers that allows them to function at such a high level for so long?” © 2024 The New York Times Company

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 13: Memory and Learning; Chapter 2: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Link ID: 29379 - Posted: 07.06.2024

By Angie Voyles Askham Some questions about neurons, such as how they give rise to behavior, are tricky to answer when those cells are embedded within their natural milieu. “Is residence in a nervous system sufficient to allow synapses to form?” says Kristin Baldwin, professor of genetics and development at Columbia University. “Are synapses that we can see sufficient to allow communication? And is synaptic communication sufficient to actually endow an animal with a set of behaviors that would be appropriate for it?” The best way to answer those questions is to put the cells in a new environment where their extrinsic and intrinsic influences can be teased apart, says Xin Jin, assistant professor of neuroscience at the Scripps Research Institute. For a long time, Jin says, that new environment was the unnatural setting of a petri dish. But two new studies that make use of chimeric mice—animals with both mouse and rat cells in their brain—point to another option: One demonstrates how rat stem cells can restore a mouse’s ability to smell, whereas the other shows how rat stem cells can give rise to a forebrain in mice that would otherwise lack one. The studies were published last month in Cell. Because rat brains are larger than mouse brains and develop at a different rate, the chimeras enable researchers to probe the competing forces of a cell’s intrinsic programming and its external environment. The work opens up doors for new research and the ability to explore the origins of species-specific cellular behaviors, says Jin, who was not involved in either study. “It’s sort of a fundamental ‘nature versus nurture,’” says Baldwin, who led one of the new studies. © 2024 Simons Foundation

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 13: Memory and Learning
Link ID: 29312 - Posted: 05.18.2024

By Laura Sanders What does it feel like to be a rat? We will never know, but some very unusual mice may now have an inkling. In a series of new experiments, bits of rat brain grew inside the brains of mice. Donor stem cells from rats formed elaborate — and functional — neural structures in mice’s brains, despite being from a completely different species, researchers report in two papers published April 25 in Cell. The findings are “remarkable,” says Afsaneh Gaillard, a neuroscientist at INSERM and the University of Poitiers in France. “The ability to generate specific neuronal cells that can successfully integrate into the brain may provide a solution for treating a variety of brain diseases associated with neuronal loss.” These chimeric mice are helping to reveal just how flexible brain development can be (SN: 3/29/23). And while no one is suggesting that human brains could be grown in another animal, the results may help clarify biological details relevant to interspecies organ transplants, the researchers say. The success of these rat-mouse hybrids depended on timing: The rat and mouse cells had to grow into brains together from a very young stage. Stem cells from rats that had the potential to mature into several different cell types were injected into mouse embryos. From there, these rat cells developed alongside mice cells in the growing brain, though researchers couldn’t control exactly where the rat cells ended up. In one set of experiments, researchers first cleared the way for these rat cells to develop in the young mouse brains. Stem cell biologist Jun Wu and colleagues used a form of the genetic tool CRISPR to inactivate a mouse gene that instructs their brain cells to build a forebrain, a large region involved in learning, remembering and sensing the world. This left the mice without forebrains — normally, a lethal problem. © Society for Science & the Public 2000–2024.

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 13: Memory and Learning; Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 29274 - Posted: 04.26.2024

By Sara Reardon Researchers have hailed organoids — 3D clusters of cells that mimic aspects of human organs — as a potential way to test drugs and even eliminate some forms of animal experimentation. Now, in two studies published on 24 April in Nature1,2, biologists have developed gut and brain organoids that could improve understanding of colon cancer and help to develop treatments for a rare neurological disorder. “In the last ten years, people spent a lot of time to develop and understand how to make organoids,” says Shuibing Chen, a chemical biologist at Weill Cornell Medical College in New York City. “But this is the time now to think more about how to use” the models. Organoids — particularly those made from human stem cells — sometimes reveal things that animal models can’t, says Sergiu Pașca, a neuroscientist at Stanford University in California and a co-author of one of the studies1. Pașca’s group studies Timothy syndrome: a genetic disorder involving autism, neurological problems and heart conditions that affects only a few dozen people in the world. Timothy syndrome is caused by a single mutation in a gene called CACNA1C, which encodes a channel through which calcium ions enter cells including neurons. Pașca says that there are no good animal models for Timothy syndrome because the underlying mutation doesn’t always cause the same symptoms in rodents. “It became very clear to us we’d need to find a way of testing in vivo,” he says. © 2024 Springer Nature Limited

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 13: Memory and Learning
Link ID: 29271 - Posted: 04.26.2024

By Diana Kwon Overall, people in U.S. live longer than they did a hundred years ago. The growing number of people reaching old age has meant an increased proportion are at risk of developing dementia or Alzheimer’s disease, illnesses that typically strike later in life. However, researchers have found that, in the U.S. and elsewhere, dementia risk may actually be decreasing, at least in a subset of the population. A new study provides a potential explanation for this trend: Human brains may be getting larger—and thus more resilient to degeneration—over time. Several large population studies in countries including the U.S. and Great Britain have found that, in recent decades, the number of new cases, or incidence, of dementia has declined. Among these is the Framingham Heart Study, which has been collecting data from individuals living in Framingham, Massachusetts since 1948. Now accommodating a third generation of participants, the study includes data from more than 15,000 people. In 2016, Sudha Seshadri, a neurologist at UT Health San Antonio and her colleagues published findings revealing that while the prevalence—the total number of people with dementia—had increased, the incidence had declined since the late 1970s. “That was a piece of hopeful news,” Seshadri says. “It suggested that over 30 years, the average age at which somebody became symptomatic had gone up.” These findings left the team wondering: What was the cause of this reduced dementia risk? While the cardiovascular health of the Framingham residents and their descendants—which can influence the chances of developing dementia—had also improved over the decades, this alone could not fully explain the decline. On top of that, the effect only appeared in people who had obtained a high school diploma, which, according to Seshadri, pointed to the possibility that greater resilience against dementia may result from changes that occur in early life. © 2024 SCIENTIFIC AMERICAN,

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 13: Memory and Learning; Chapter 13: Memory and Learning
Link ID: 29265 - Posted: 04.20.2024

By Tomasz Nowakowski, Karthik Shekhar Diverse neurons and their equally diverse circuits are the foundation of the brain’s remarkable ability to process information, store memories, regulate behavior and enable conscious thought. High-throughput, single-cell profiling technologies have made it possible to classify these cells more comprehensively than ever before, offering a 360-degree view of the sheer magnitude of neural diversity in the mammalian brain. A recent effort to define the complete set of transcriptomic cell types in the adult whole mouse brain, for example, defined roughly 5,000 distinct cell types distributed across dozens of brain areas. This landmark accomplishment is a critical step toward integrating information about function and connectivity, and extending similar efforts to the adult human brain. But this impressive gestalt conveys little, if any, information about how such diversity arises and develops in the first place. Single-cell atlases developed to date have been limited to a few points in time, focusing largely on the endpoint of neural development. How is this exquisite panoply of neurons generated and organized into precise and orderly circuits that last a lifetime? Providing the answer is the central task of developmental neuroscience. We want to understand the many transitions that unfold — where cells come from, the paths they take, and when terminal cell states emerge. The comprehensive nature of single-cell technologies offers tremendous promise for defining cell types and reconstructing the trajectories of gene expression that underlie their differentiation. Initial efforts to apply these technologies to development, including in the prenatal human brain, hint at the insights these approaches can bring. Single-cell transcriptomics has helped map the diversity of neural progenitor cells, for example, most notably identifying progenitors that are expanded in humans, and their associated molecular adaptations. Further insights into development will require methods that reveal the specific history of every neuron type, including those that can more densely sample brain cells’ trajectories over time and novel approaches for tracking fate transitions in individual cells. These discoveries will in turn help us to understand neurodevelopmental conditions, many of which are associated with genomic variation, and neurological disorders, such as brain tumors. © 2024 Simons Foundation

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 13: Memory and Learning
Link ID: 29198 - Posted: 03.19.2024

By Claudia López Lloreda By squirting cells from a 3D printer, researchers have created tissue that looks—and acts—like a chunk of brain. In recent years, scientists have learned how to load up 3D printers with cells and other scaffolding ingredients to create living tissues, but making realistic brainlike constructs has been a challenge. Now, one team has shown that, by modifying its printing techniques, it can print and combine multiple subtypes of cells that better mimic signaling in the human brain. “It’s remarkable that [the researchers] can replicate” how brain cells work, says Riccardo Levato, a regenerative medicine researcher at Utrecht University who was not involved with the study. “It’s the first demonstration that, with some simple organization [of cells], you can start getting some interesting functional [responses].” The new technology, described last week in Cell Stem Cell, could offer advantages over existing techniques that neuroscientists use to create 3D brain tissues in the lab. One common approach involves using stem cells to grow miniature brainlike blobs called organoids. But researchers can’t control the types of cells or their precise location in these constructs. Each organoid “is unique,” making it difficult to reproduce research results, says neuroscientist Su-Chun Zhang of the University of Wisconsin–Madison, an author of the new study. With the right kind of 3D printing, however, “you can control where different cell types are placed,” says developmental biologist Francis Szele of the University of Oxford. Past studies have used 3D printers to construct brain tissues that allowed researchers to study how the cells matured and made connections, and even integrate printed tissue into mouse brains. But those constructs had limited functionality. And efforts that produced more functional printed tissue used rat cells, not human cells. © 2024 American Association for the Advancement of Science.

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 11: Motor Control and Plasticity
Related chapters from MM:Chapter 13: Memory and Learning; Chapter 5: The Sensorimotor System
Link ID: 29145 - Posted: 02.10.2024

By Viviane Callier Aging can seem like an unregulated process: As time marches along, our cells and bodies inevitably accumulate dings and dents that cause dysfunctions, failures and ultimately death. However, in 1993 a discovery upended that interpretation of events. Researchers found a mutation in a single gene that doubled a worm’s life span; subsequent work showed that related genes, all involved in the response to insulin, are key regulators of aging in a host of animals, from worms and flies to humans. The discovery suggested that aging is not a random process — indeed, specific genes regulate it — and opened the door to further research into how aging proceeds at a molecular level. Recently, a set of papers documented a new biochemical pathway that regulates aging, one based on signals passed between mitochondria, the organelles best known as the powerhouse of the cell. Working with worms, the researchers found that damage to mitochondria in brain cells triggered a repair response that was then amplified, setting off similar reactions in mitochondria throughout the worm’s body. The effect of this repair activity was to extend the organism’s life span: The worms with repaired mitochondrial damage lived 50% longer. What’s more, cells in the germline — the cells that produce eggs and sperm — were central to this anti-aging communication system. It’s a finding that adds new dimensions to the fertility concerns implied when people talk about aging and their “biological clock.” Some of the findings were reported in Science Advances and others were posted on the scientific preprint server biorxiv.org in the fall. All Rights Reserved © 2024

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 13: Memory and Learning
Link ID: 29092 - Posted: 01.11.2024

By Sara Reardon At birth, a human baby’s brain contains the most neurons it will ever have. How this complex brain develops in the womb has been hard to study in humans. But a new and potentially controversial method, growing tiny, brainlike structures called organoids in a dish from human fetal brain tissue, could provide a realistic model and improve the study of developmental disorders or brain cancers. The team that achieved this first, reported yesterday in Cell, has also shown it can genetically engineer the blobs of tissue, which could help the fetal brain organoids (FeBOs) mimic certain diseases. The researchers have “demonstrated some interesting and creative uses,” for the new organoids, says Arnold Kriegstein, a neurologist at the University of California (UC), San Francisco. He thinks FeBOs might help researchers tackle previously unexplored questions about how neurons take on specific identities in the maturing brain, for example. Researchers have already created organoids that mimic multiple parts of the brain and nervous system using stem cells that have the capacity to turn into many or all known cell types with the right stimulation and environment. To study genetic conditions that affect brain development, scientists can also “reprogram” mature cells from affected patients into stem cells to make organoids. Some stem cell–derived brain organoids, which are usually about the size of a grain of rice, have even produced electrical activity reminiscent of that in the brain of a fetus. But although these organoids can be useful representations of the brain, the starting stem cells must be “pushed” into a brainlike state through an introduced cocktail of signaling molecules—a complex process that may not fully replicate normal development, says stem cell biologist Benedetta Artegiani of the Princess Máxima Center for Pediatric Oncology. Using natural fetal brain tissue might reveal more about what the human brain really looks like at this stage of development. (Previous studies have made organoids from human fetal intestine, liver, and lung tissue, but not brain.) © 2024 American Association for the Advancement of Science.

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 13: Memory and Learning
Link ID: 29090 - Posted: 01.11.2024

By Yasemin Saplakoglu In the 16th century, the Belgian cartographer Abraham Ortelius created the world’s first modern atlas — a collection of maps that he called “The Theater of the World.” The maps, drawn by Ortelius and others, detailed what was at the time the best knowledge of the world’s continents, cities, mountains, rivers, lakes and oceans and helped usher in a new understanding of global geography. Similarly, the creation of cell atlases — maps of organs and bodies constructed cell by cell — is heralding a new era in our understanding of biology. Powerful sequencing and imaging technologies invented in the last decade are revealing with unprecedented detail the composition of human organs and tissues, from the pancreas and liver to the placenta, as well as those of other animals like the mouse and fruit fly. With these new tools, researchers can fingerprint individual cells based on which genes they are expressing. That information has revealed subtle and unsuspected distinctions among cells and has begun to illuminate how the diversity of cell types can be essential to the healthy functioning of organs. “We’re at this amazing point in time in science where we’re now able to understand the composition of these cell types,” said Steve Quake, a bioengineer and biophysicist at Stanford University who helped develop the technologies that make cell atlases possible. “It’s changed the way we understand how human biology works.” Two cell atlas efforts, part of the National Institutes of Health’s $250 million brain cell census, that just released their findings illustrate the excitement bubbling up in the field. Today in Nature, a coalition of laboratories published nine studies that collectively form a detailed atlas of the mouse brain — the most comprehensive mammalian brain atlas to date. It describes more than 5,300 types of cells found throughout the organ. How these cells are distributed and are related to one another suggests many intriguing ideas about the evolution of the mammalian brain. All Rights Reserved © 2023

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 13: Memory and Learning; Chapter 2: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Link ID: 29053 - Posted: 12.16.2023

By Carl Zimmer Why do we grow old and die? In the 19th century, the German biologist August Weismann argued that the machinery of life inevitably wore out with time. Death had evolved “for the need of the species,” he declared. It cleared away weak, old individuals so they wouldn’t compete with young ones. That explanation never made sense to George Williams, an American evolutionary biologist. Natural selection acts only on the genes that are passed down from one generation to the next. What happens at the end of an animal’s life can have no effect on the course of evolution. It occurred to Williams that growing old might instead be an inescapable side effect of natural selection. In 1957, he proposed a new theory: Genetic mutations that increased an animal’s fertility could also cause harm late in life. Over many generations, those mutations would create a burden that would lead eventually to death. A new study, published on Friday in the journal Science Advances, bolsters Williams’s theory using a trove of human DNA. Researchers found hundreds of mutations that could boost a young person’s fertility and that were linked to bodily damage later in life. Smaller studies in the past had already offered some support for Williams’s theory. In 2007, for example, a team of researchers studying a tiny worm found a pair of mutations that lengthened the creature’s life while cutting down its average number of offspring. But Jianzhi Zhang, an evolutionary biologist at the University of Michigan, was not satisfied with these experiments. “These are case studies,” he said. “We don’t know if in the entire genome there are lots of such mutations.” Dr. Zhang tapped into the UK Biobank, a database containing genetic material from half a million volunteers in Britain, along with information on their health and life experiences. The biobank has permitted scientists to uncover subtle links between genetic variations and thousands of traits such as high blood pressure, schizophrenia and a habit of smoking. Working with Dr. Erping Long, a medical researcher now at the Chinese Academy of Sciences, Dr. Zhang pored over the database for information about reproduction and longevity. The scientists found that the genetic variations linked to fertility, such as the number of children a volunteer had, were also linked to a shorter life span. © 2023 The New York Times Company

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 13: Memory and Learning; Chapter 8: Hormones and Sex
Link ID: 29048 - Posted: 12.16.2023

By Laura Sanders WASHINGTON — Brain scans could be used to predict how teenagers’ mental health will fare during a stressful time, an analysis that spanned the COVID-19 pandemic suggests. The findings, presented November 13 in a news briefing at the annual meeting of the Society for Neuroscience, may help explain why some people succumb to stress while others are more resilient. For a lot of research, “the study happens, and you report on the results, and that’s about it,” says Margot Wagner, a bioengineer at the University of California, San Diego who was not involved in the new work. But this research followed hundreds of teenagers over time, a study design that “means you can intervene and help way sooner than otherwise,” Wagner says. The pandemic was particularly tough for many teenagers, as isolation, worry and upheaval of daily routines affected them in ways that scientists are just now starting to see (SN: 1/3/23). A record number of young people are struggling with depression and anxiety, a mental health crisis that some scientists are calling “the second pandemic” (SN: 6/30/23). While many teenagers struggled during the pandemic, others did OK. Computational neuroscientist Caterina Stamoulis of Harvard Medical School and Boston Children’s Hospital investigated why responses differed using data collected as part of the Adolescent Brain Cognitive Development, or ABCD, study. That larger study — involving scientists at 21 research sites across the United States — aims to figure out how teenagers’ brains grow over the years. “This is the first time in history we’re looking at thousands of participants and getting these measures over time,” Wagner says. “It’s truly remarkable.” The ABCD study, begun in 2015, was well under way when COVID hit, so researchers possessed brain scans from before the pandemic. “Without the pandemic, we would not have been able to understand the impact of a long-lasting adverse event” that deeply affected the participants’ lives, changing their interactions with their family and friends, Stamoulis says. © Society for Science & the Public 2000–2023.

Related chapters from BN: Chapter 15: Emotions, Aggression, and Stress; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress; Chapter 13: Memory and Learning
Link ID: 29012 - Posted: 11.18.2023