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Tag: Stockholm University

  • Bioparticles vital in Arctic cloud ice formation

    Bioparticles vital in Arctic cloud ice formation

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    Newswise — An international team of scientists from Sweden, Norway, Japan, and Switzerland, has presented research findings that reveal a crucial role of biological particles, including pollen, spores, and bacteria, in the formation of ice within Arctic clouds. These findings, published today in Nature Communications, have far-reaching implications for climate science and our understanding of the rapidly changing Arctic climate.

    The research, whose outcomes have unveiled the connection between biological particles and the formation of ice in Arctic clouds, was conducted over multiple years at the Zeppelin Observatory, situated on the remote Norwegian archipelago of Svalbard, Norway, in the High Arctic. Gabriel Freitas, lead author and PhD student at Stockholm University, detailed their innovative approach:
    “We have individually identified and counted these biological particles using a sensitive optical technique reliant on light scattering and UV-induced fluorescence. This precision is essential as we navigate through the challenge of detecting these particles in minuscule concentrations, akin to finding a needle in a haystack.”

    Sugar alcohols as indicators of fungal spores
    The study delved into the seasonal dynamics of biological particles, establishing correlations with variables such as snow cover, temperature, and meteorological parameters. Furthermore, the presence of biological particles was confirmed through various methodologies, including electron microscopy and the detection of specific substances, such as the sugar alcohol compounds arabitol and mannitol.
    Karl Espen Yttri, senior scientist at the Climate and Environmental Research Institute NILU and a co-author of the study, underscored that: “While arabitol and mannitol are present in various microorganisms, their presence in air are related to fungal spores, and might originate both from local sources or from long range atmospheric transport”.

    Microbes contribute to ice nucleation at Zeppelin Observatory
    The quantification of ice nucleating particles and understanding their properties proved to be a cumbersome challenge. Researchers employed two distinct methods, involving the collection of particles on filters over a week, followed by rigorous laboratory analysis.

    Yutaka Tobo, Associate Professor at the National Institute of Polar Research in Japan and co-author of the study, described their strategy: “Our method can quantify the ice nucleating ability of aerosol particles immersed in water droplets at temperatures ranging from 0°C down to about -30°C, thereby revealing the concentration of ambient ice nucleating particles active in Arctic low-level clouds.”

    Franz Conen, Research Fellow at the University of Basel, Switzerland, added, “By subjecting the filters to additional heating at 95°C, we could identify the proteinaceous component of ice nucleating particles, shedding light on their potential biological origin. Our findings unequivocally establish the prevalence of biological particles contributing to ice nucleation at Zeppelin Observatory.”

    Paul Zieger, Associate Professor at Stockholm University and co-author, emphasized the important implication of these findings for climate science: “This research offers critical insights into the origin and properties of biological and ice nucleating particles in the Arctic that could enable climate model developers to improve the representation of aerosol-cloud interactions in models and reduce uncertainties related to anthropogenic radiative forcing estimates.”

    Increases in open ocean areas and snow-free tundra, both sources of biological particles in the Arctic, are expected in the coming decades. Therefore, gaining a deeper understanding of the relationship between these particles and clouds may provide valuable insights into the ongoing and future transformations occurring in the Arctic.

    Read article in Nature Communications: Regionally sourced bioaerosols drive high-temperature ice nucleating particles in the Arctic

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    Stockholm University

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  • New method to study microRNA activity in single cells

    New method to study microRNA activity in single cells

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    Newswise — MicroRNAs are small molecules that regulate gene activity by binding to and destroying RNAs produced by the genes. More than 60% of all human genes are estimated to be regulated by microRNAs, therefore it is not surprising that these small molecules are involved in many biological processes including diseases such as cancer. To discover the function of a microRNA, it is necessary to find out exactly which RNAs are targeted by it. While such methods exist, they require a lot of material typically in order of millions of cells, to work.

    Now researchers at Stockholm University and SciLifeLab have developed a new method to detect microRNA targets at the level of single cells. Such cells are each around one-hundredth millimeter in diameter and weigh less than a billionth gram, and comprise the basic building blocks of living organisms. With their new sensitive method, the researchers can follow microRNA targeting of thousands of RNAs during biological processes such as the cell cycle or differentiation into red blood cells. In these processes, the researchers find that microRNAs – surprisingly – perform quite different tasks in each cell. In the future, it will be possible to also apply this method to study microRNA targeting in whole tissues, to find out exactly what is happening in each of the many cell types that comprise complex organs such as brains.

    Marc Friedländer, associate professor at Stockholm University, says: “In our research team, we want to understand and ultimately make mathematical models of gene regulation at the level of the single cell. Our new method is a huge leap towards making this possible”.

    The work was spearheaded by Dr. Inna Biryukova, who took a leading role in developing the laboratory method, and by PhD student Vaishnovi Sekar, who performed the bulk of the advanced computational analyses. Vaishnovi Sekar highlights the challenges of the project: “In terms of complexity of the computational work, this is uncharted territory, and we lacked reference points and thresholds. We had to explore a myriad of approaches to devise a methodology that not only works but also yields biologically meaningful observations.”

    The study was supported by ERC and Vetenskapsrådet and has been published in the journal Nature Biotechnology.

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  • Order sets humans apart from animals

    Order sets humans apart from animals

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    Newswise — Remembering the order of information is central for a person when participating in conversations, planning everyday life, or undergoing an education. A new study, published in the scientific journal PLoS One, shows that this ability is probably human unique. Even the closest relatives of humans, such as bonobos, do not learn order in the same way.

    “The study contributes another piece of the puzzle to the question of how the mental abilities of humans and other animals differ, and why only humans speak languages, plan space travel, and have learned to exploit the earth so efficiently that we now pose a serious threat to countless other life forms”, says Johan Lind, associate professor in ethology and deputy director at the Center for Cultural Evolution, Stockholm University. Since September also associate professor of ethology at Linköping University.

    Already earlier research at Stockholm University has suggested that only humans have the ability to recognize and remember so-called sequential information, and that this ability is a fundamental building block underlying unique human cultural abilities. But previously, this sequence memory-hypothesis has not been tested in humans’ closest relatives, the great apes. The new experiments now show that also bonobos, one of the great apes, struggle to learn the order of stimuli.

    In the recently published book The Human Evolutionary Transition: From Animal Intelligence to Culture (Princeton University Press), ethologists Magnus Enquist and Johan Lind at Stockholm University, and Stefano Ghirlanda, researcher in psychology at Brooklyn College, New York, have launched a new theory for how humans became cultural beings. A central idea concerns the difference in how humans and other animals recognize and remember sequential information.

    “We have previously analyzed a large number of studies that suggest that only humans recognize and remember sequential information faithfully. But, even though we analyzed data from a number of mammals and birds, including monkeys, there has been a lack of information from our closest relatives, the other great apes”, says Johan Lind.

    In a series of experiments, memory abilities of bonobos and humans were tested by having them press computer screens to, among other things, learn to distinguish between short sequences, including pressing right if a yellow square comes before a blue square, or by pressing to the left of the blue square appears before the yellow square.

    “The study shows that bonobos forget that they have seen a blue square already five to 10 seconds after it has disappeared from the screen, and that they have great difficulty learning to distinguish the sequences blue-square-before-yellow-square from yellow-square- before-blue-square, even though they have been trained for thousands of trials”, says Vera Vinken, associated with Stockholm University, now a PhD student in Great Britain at the Biosciences Institute, Newcastle University.

    In contrast, the study shows that humans learned to distinguish the short sequences nearly immediately. However, it still remains to be shown exactly how our closest relatives can remember and use sequential information.

    “We now know that our closest relatives do not share the same sequential mental abilities with humans. But even if the results indicate that their working memory works in principle in the same way as in rats and pigeons, no one has yet demonstrated this in practice”, says Magnus Enquist, professor emeritus and one of the founders of the Center for Cultural Evolution.

    The new results provide further support for the sequence memory-hypothesis, that during human prehistory an ability to remember and process sequences evolved, a necessary mechanism for many uniquely human phenomena such as language, planning ability and sequential thinking.

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  • Babies or beauty?

    Babies or beauty?

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    A new study published in Science Advances has not only revealed that an ALHS in Colias butterflies has an ancient origin, but also determined the mechanisms contributing to its persistence over millions of generations.

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  • Identity Theft the Secret of the Cat Parasite’s Success

    Identity Theft the Secret of the Cat Parasite’s Success

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    Newswise — The parasite Toxoplasma is carried by a large portion of the global human population. Now a study led by researchers at Stockholm University shows how this microscopic parasite so successfully spreads in the body, for example to the brain. The parasite infects immune cells and hijacks their identity. The study is published in the scientific journal Cell Host & Microbe.

    In order to fight infections, the various roles of immune cells in the body are very strictly regulated. Scientists have long wondered how Toxoplasma manages to infect so many people and animal species and spread so efficiently.

    “We have now discovered a protein that the parasite uses to reprogram the immune system”, says Arne ten Hoeve, researcher at the Department of Molecular Biosciences, Wenner-Gren Institute at Stockholm University.

    The study shows that the parasite injects the protein into the nucleus of the immune cell and thus changes the cell’s identity. The parasite tricks the immune cell into thinking it is another type of cell. This changes the gene expression and behavior of the immune cell. Toxoplasma causes infected cells which normally should not travel in the body to move very quickly and in this way the parasite spreads to different organs.

    The phenomenon has been described as Toxoplasma turning immune cells into Trojan horses or wandering “zombies” that spread the parasite. The newly published study provides a molecular explanation for the phenomenon, and also shows that the parasite is much more targeted in its spread than previously thought.

    “It is astonishing that the parasite succeeds in hijacking the identity of the immune cells in such a clever way. We believe that the findings can explain why Toxoplasma spreads so efficiently in the body when it infects humans and animals,” says Professor Antonio Barragan, who led the study, which was carried out in collaboration with researchers from France and the USA.

    The work is published in the scientific journal Cell Host & Microbe.
    The Toxoplasma effector GRA28 promotes parasite dissemination by inducing dendritic cell-like migratory properties in infected macrophages. Arne L. ten Hoeve, Laurence Braun, Matias E. Rodriguez, Gabriela C. Olivera, Alexandre Bougdour, Lucid Belmudes, Yohann Couté, Jeroen P.J. Saeij, Mohamed-Ali Hakimi, Antonio Barragan DOI: 10.1016/j.chom.2022.10.001

    About the parasite Toxoplasma and the disease toxoplasmosis:

    Toxoplasmosis is probably the most common parasitic infection in humans globally. Toxoplasma also infects many animal species (zoonosis), including our pets. The WHO has estimated that at least 30% of the world’s human population is a carrier of the parasite. Studies indicate that 15-20% of the Swedish population carry the parasite (the vast majority without knowing it). The incidence is higher in several other European countries.

    Felines, not just domestic cats, have a special place in the life cycle of Toxoplasma: it is only in the cat’s intestine that sexual reproduction takes place. In other hosts, for example humans, dogs or birds, reproduction takes place by the parasite dividing.

    Toxoplasma is spread through food and contact with cats. In nature, the parasite spreads preferentially from rodents to cats to rodents and so forth. The parasites are “sleeping” in the rodent’s brain and when the cat eats the mouse, they multiply in the cat’s intestine and come out via the feces. The parasite ends up in the vegetation and when the rodent eats the vegetation it becomes infected. Humans become infected through meat consumption or through contact with cats, specifically cat feces.

    The parasite causes the disease toxoplasmosis. When a person is infected for the first time, mild flu-like symptoms occur that can resemble a cold or a flu. After the first infection phase, the parasite transitions to a “sleeping” stage in the brain and begins a chronic silent infection that can last for decades or for life. The chronic infection usually causes no symptoms in healthy individuals. Toxoplasma can, however, cause a life-threatening brain infection (encephalitis) in people with a weakened immune system (HIV, organ transplant recipients, after chemotherapy) and can be dangerous to the fetus during pregnancy. Eye infections can occur in otherwise healthy individuals.

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