npj Microgravity

Space travel is becoming accessible, yet our understanding of how space environment and microgravity ({micro}G) affect biology, physiology, and health remains incomplete. We investigated {micro}G effects on neuromuscular development and aging in Caenorhabditis elegans. Nematodes in {micro}G showed downregulation of genes related to synaptic signaling, dopamine response, locomotion, and cuticle development, with impaired synaptic vesicle dynamics, reduced motility, and shorter body lengths. Aged worms in {micro}G showed decreased collagen gene expression, increased motor neuron defects, synaptic vesicle accumulation and decreased release, and mitochondrial morphology collapse in body wall muscles, indicating accelerated aging. MEC-4 mechanoreceptor was identified as a key mediator of {micro}G-induced body length reduction and changes in extracellular matrix gene expression. {micro}G conditions suppressed mechanoreceptor genes, suggesting multiple mechanosensory systems are affected. Physical stimulation through culture medium with small beads in space mitigated many {micro}G-induced expression changes, including mechanoreceptors, neuromuscular defects, and aging-related phenotypes. These results highlight mechanical stimulis role in maintaining neuromuscular integrity during spaceflight and suggest restoring tactile input could counter health risks from reduced stimulation in long-term space missions. SIGNIFICACEWe found that microgravity ({micro}G) conditions suppress the expression of multiple mechanoreceptor genes in Caenorhabditis elegans, indicating that several mechanosensory systems are affected during spaceflight. Importantly, reintroducing physical stimulation by adding small beads to the culture medium in space partially reversed many of these {micro}G-induced gene expression changes. This intervention also mitigated neuromuscular defects and aging-related phenotypes observed under {micro}G conditions. Collectively, these findings underscore the essential role of mechanical stimuli in preserving neuromuscular integrity during space missions and suggest that restoring tactile input may be a promising strategy to counteract the health risks associated with reduced tactile stimulation during prolonged spaceflights.

Glioblastoma (GBM) is an incurable brain cancer characterized by its highly immunosuppressive tumor microenvironment and aggressive malignant features that resist treatment. To overcome limitations of Earth-based models (sedimentation and disaggregation) and leverage the unique biological effects of space (accelerated disease progression and immune dysregulation), we developed a panel of GBM-myeloid organoids for extended culture on the International Space Station. After 40 days, the spaceflight-grown organoids had more uniform and reproducible morphology compared to identical ground controls. Organoids containing GBM cells + monocytes had increased expression of chronic innate inflammation, adaptive immune activation, and tissue and vascular remodeling-associated genes. There was an increase in organization of gene expression patterns, with mesenchymal-related genes enriched in the core and inflammation-related genes enriched at the periphery, mimicking GBM tumor architecture. Secretomics confirmed the generation of more immunosuppressive organoids, with enrichment of proteins associated with more aggressive disease, including CXCL12 and LOX-1. GBM co-culture organoids thus had enhanced transcriptomic, proteomic, and architectural features when grown in microgravity that are associated with worse patient outcomes from retrospective data. Infrared laser scanning microscopy confirmed spatial chemical gradients for DNA, protein, and lipid species in both space- and terrestrially-grown organoids. In summary, we present not only a novel and superior model of glioblastoma for more relevant basic, mechanistic, and translational research, but also demonstrate methods to acquire high-quality and diverse data from organoids compatible with the unique experimental constraints of biological research in space to help establish a working model for orbital oncology.

Unexploded ordnances (UX.Os) and landmines endanger lives and hinder the economic progress of communities living in post-conflict zones. Currently, the primary method for clearing UX.Os relies on metal detection and manual removal of UX.Os - an expensive, time-consuming, and hazardous process. This study, derived from the 2024 EPFL iGEM project SYNPLODE, presents a new approach that integrates synthetic biology and aerial drone robotics, proposing a novel, end-to-end, safe, and efficient solution to address UX.Os. Starting from bacteria engineered to detect and degrade 2,4,6-trinitrotoluene (TNT), a common explosive in landmines, our solution is designed for three main tasks: detecting TNT and RDX, breaking these compounds down into non-explosive byproducts, and confirming explosive neutralisation. To deploy this solution safely in UXO-contaminated areas, we designed, built, and tested an aerial drone capable of spraying explosive-degrading bacteria. Combining synthetic biology, robotics, mathematical modelling, and affected community engagement, our solution aims to improve UXO and landmine clearance by offering a scalable and cost-effective approach for deactivating UX.Os without risking human lives.

Rooting systems of plants perceive environmental stimuli and flexibly regulate their growth. Therefore, understanding stimulus perception and response mechanisms is essential for optimizing cultivation. During the transition from aquatic to terrestrial environments, land plants have acquired mechanisms to adapt to gravitational force on land. Thus, elucidating gravity responses of rhizoids in bryophytes, early diverging land plants, provides important insights into how gravity-response mechanisms were established during land plant evolution. Analyzing rhizoid morphology under microgravity, where gravitational effects are largely eliminated, provides an effective approach to examine the gravity-response mechanisms that evolved after terrestrialization. In this study, to elucidate microgravity effects on rhizoid growth of Physcomitrium patens, we analyzed 3D datasets obtained by refraction-contrast micro-CT using synchrotron radiation after fixation and embedding of samples from the Space Moss experiment conducted on the International Space Station. Because each CT volume contains numerous rhizoids, we optimized a WEKA-based machine-learning segmentation approach by improving preprocessing, training, and postprocessing steps, resulting in a significantly improved segmentation accuracy. Comparison of 3D morphological indices between manually segmented rhizoids and predicted results supported the validity of the proposed method for morphological analysis. Morphological analyses revealed that, compared with both ground and artificial 1 x g conditions, rhizoid elongation and gravitropic responses were suppressed under microgravity, leading to reduced vertical growth. These findings indicate that gravity plays a fundamental role in rhizoid morphogenesis, and their absence affects growth orientation and elongation. This study provides foundational data for research on the rooting systems of bryophytes in space.

ABSTRACTMotion sickness (MS) is commonly hypothesized to arise from sensory conflicts between incongruent sources of sensory information. Different types of sensory conflicts can induce MS, yet it remains unclear whether distinct contexts produce different physiological responses. Moreover, there is a lack of reliable objective predictors of MS, particularly for space motion sickness (SMS), which appears unrelated to motion sickness susceptibility on Earth. This study examined multiple physiological measures as potential objective markers of MS, including heart rate, blood pressure, salivary cortisol, skin conductance, skin surface temperature, and facial skin colorimetry. Subjective motion sickness severity and symptomatology were assessed using standardized questionnaires (SSQ, MSAQ, MSSQ). All measures were collected before and immediately after exposure to two sensory conflict paradigms: virtual reality (visuo-vestibular conflict) and parabolic flight (otolitho-canal conflict). Post-exposure, both paradigms were associated with increased cortisol, skin conductance, and skin greeness. Notably, increased skin greenness was associated with greater MS severity in parabolic flight and strongly correlated with subjective nausea ratings in both paradigms. Skin temperature and systolic blood were affected differently by VR and parabolic flight. No robust new physiological predictors of MS were identified. Overall, our findings suggest that facial skin color -particularly skin greenness- may serve as a simple, non-invasive, and reliable objective indicator of MS severity.

Space-based platforms currently represent the most accurate means to experimentally assess the influence of the space environment on biological systems. However, performing such experiments remains technically challenging and requires highly specialized instrumentation. This study describes the current development and hardware qualification of ExocubeBio, a miniaturized experimental platform for in-situ biological space exposure. This experiment is scheduled for installation on the exterior of the International Space Station in 2027, as part of Exobio, the European Space Agencys new generation exobiology exposure facility. ExocubeBio will expose live microbial samples to the low Earth orbit environment, and combine autonomous in-situ optical density and fluorescence measurements, with the capacity to return preserved samples to Earth. Achieving these experimental goals requires a specialized, robust and reliable hardware system. The ExocubeBio hardware testing described here includes assessment of material biocompatibility and durability, functional validation of the miniaturized fluidic system, and optimization of the integrated optical subsystem for optical density and fluorescence measurements. These results demonstrate that the ExocubeBio experimental hardware components can each execute their core functional and operational requirements; subsystems allow for sample exposure, in-situ measurements of microbial cultures, and the chemical preservation of samples for post-flight analysis. As ExocubeBio transitions from hardware development to mission readiness, the results presented here validate the overall design and engineering approaches utilized. By combining the strengths of in-situ monitoring and sample return, ExocubeBio represents a significant advancement in space-based experimentation, and will provide new insights into microbial responses to the space environment.

Environmental stressors rarely affect just one brain circuit. Most studies assess single cognitive endpoints, obscuring whether vulnerabilities are global or circuit-selective and how effects distribute across interconnected systems. To address this, we used galactic cosmic radiation (GCR), a Mars mission-relevant stressor that disrupts the hippocampal-nucleus accumbens-prefrontal circuit. C57BL/6J mice received 33-ion GCR simulation (33-GCR, 0.75 Gy) or sham radiation with the Nrf2-activating compound CDDO-EA or vehicle, followed by multi-domain behavioral testing in both sexes. Under very high memory load, male Veh/33-GCR mice showed enhanced pattern separation compared to Veh/Sham males, an effect normalized by CDDO-EA. Female mice showed no radiation-induced changes in pattern separation but weighed 9-18% more than Veh/Sham females and had reduced locomotor activity. Reward-based learning differed by sex: males showed no changes, while female Veh/33-GCR mice displayed enhanced reward anticipation that was further increased by CDDO-EA alone, with both treatments contributing to elevated goal-tracking. For behavioral flexibility, CDDO-EA impaired reversal learning in males regardless of radiation, while 33-GCR impaired reversal learning in females regardless of CDDO-EA. Principal component analysis revealed that treatments disrupted specific circuit relationships while leaving others intact, consistent with selective rather than global cognitive effects. Fiber photometry showed enhanced dentate gyrus encoding activity in irradiated males under high memory load. Combined CDDO-EA/33-GCR selectively reduced dentate gyrus progenitors in females. Males and females showed distinct, circuit-selective vulnerability patterns, demonstrating that multi-domain, both-sex assessment is necessary to capture how stressors and interventions affect integrated brain function. CDDO-EA proved to be a double-edged sword: protecting one cognitive domain while impairing another, a trade-off invisible to single-endpoint assessment. This framework has immediate relevance for astronaut risk assessment and extends to any context where neuroprotective interventions are evaluated against environmental stressors.

As human space exploration expands to the Moon, Mars, and beyond, there is a growing need to study the effects of altered gravity on the microbial systems that we will bring with us for life support. Because spaceflight experiment opportunities are rare and resource-intensive, most space biology experiments are conducted using ground-based simulators. The most common microgravity simulator for microbial experiments, the rotating wall vessel, can approximate the low-shear and low-turbulence conditions that characterize microgravity. However, current designs do not allow for real-time measurement of growth or metabolic activity during rotation: experiments require destructive sampling or disruption of the microgravity simulation conditions. Here, we describe the development of an in situ spectroscopy system compatible with the Cell Spinpod rotating wall vessel, which enables measurement of both optical absorbance and fluorescence with high temporal resolution, producing growth curves similar to those from an off-the-shelf plate reader. These results are validated using two common microbial hosts: Escherichia coli and Saccharomyces cerevisiae. The Spinpod Optical System has the potential to diversify the types of microbiology experiments possible in simulated microgravity, allowing the measurement of not only growth curve parameters but also metabolic activity, gene expression, or community dynamics. It thus has the potential to improve the quality of experiments seeking to characterize microbial responses to spaceflight conditions.

Understanding how airborne particulates disrupt the human alveolar barrier requires in vitro systems that accurately replicate its composition and function. We present a biodegradable lung alveoli-on-a-chip that reproduces the architecture and physiology of the human air-blood interface using a porous poly(lactic-co-glycolic acid) (PLGA) membrane positioned between epithelium and endothelium under air-liquid interface (ALI) culture. The membrane, fabricated by porogen-assisted nonsolvent-induced phase separation, exhibited >50 % porosity, [~]2 {micro}m thickness, and mechanical compliance over 100-fold higher than conventional Transwell inserts, closely resembling the native interstitium. During co-culture, gradual PLGA degradation was compensated by cell-secreted extracellular-matrix (ECM) proteins such as collagen IV and laminin, forming a self-remodeling barrier that maintained integrity for at least 11 days. The platform supported stable epithelial-endothelial co-culture, high transepithelial electrical resistance, and physiologically relevant permeability. To demonstrate its utility, the chip was used to assess pulmonary toxicity of four types of waste-combustion-derived particulates, including rubber, plastic bags, plastic bottles, and textile fibers, delivered apically under ALI conditions. All combustion products reduced cell viability, increased hydrogen-peroxide release, and elevated {gamma}-H2AX expression, indicating oxidative and genotoxic stress, while disrupting barrier permeability. Rubber combustion particles elicited the most severe toxicity, causing the greatest loss of viability, accumulation of reactive oxygen species, and formation of DNA double-strand breaks. Together, these results establish a biodegradable, ECM-remodeling lung alveoli-on-a-chip as a physiologically relevant platform for investigating source-specific particulate toxicity and alveolar-barrier pathophysiology. By bridging environmental exposure models with human-relevant lung biology, this system provides a quantitative and translatable tool for evaluating respiratory risks and therapeutic interventions.

Spaceflight-Associated Neuro-ocular Syndrome (SANS) involves complex interactions between intracranial pressure (ICP), intraocular pressure (IOP), and cerebrospinal fluid (CSF) dynamics within the optic nerve subarachnoid space (ONSAS). While existing computational models address specific aspects of these interactions, they lack a comprehensive, system-level representation. To bridge this gap, we present the HEAD (Hemodynamic Eye-brain Associated Dynamics) model. By consistently integrating several previously proposed physiological sub-models, HEAD provides a unified lumped-parameter framework that fully couples cerebrovascular autoregulation, multi-territory ocular hemodynamics, and compartmentalized craniospinal-ONSAS CSF circulation under gravitational loading. This formulation enables the simultaneous analysis of eye-brain-CSF dynamics within a single computational tool. Model predictions were validated against experimental data from supine (0{degrees}) to head-down tilt (HDT, -30{degrees}) postures, accurately reproducing posture-dependent IOP increases and achieving an excellent ICP match against clinical benchmarks at the -6{degrees} HDT standard bed-rest angle. The coupled system predicts bed-specific ocular hemodynamic responses, with retinal blood flow exhibiting the largest relative increase under HDT compared to the ciliary and choroidal circulations. Crucially, explicitly modeling the ONSAS as a distinct compartment reveals a posture-dependent pressure drop of 1.89-3.69 mmHg between the intracranial and perioptic spaces. This compartmentalization yields a translaminar pressure profile that remains positive (8.05-11.83 mmHg) across all simulated conditions but is chronically reduced under sustained HDT. Ultimately, the HEAD model elucidates the physiological mechanisms linking gravitational stress to translaminar mechanics, providing a robust computational foundation to investigate SANS and supply boundary conditions for structural models of the optic nerve head.

Accurate assessment of low-dose neutron radiation exposure remains a central challenge in biodosimetry, particularly for applications requiring non-invasive sample types such as skin. Here, we characterized the transcriptional response of a three-dimensional in vitro human skin model (EpiDermFT) to neutron irradiation at doses up to 0.75 Gy, measured from pre-exposure through a 14-day post-exposure period. RNA sequencing revealed greater than 800 significantly altered genes, including upregulation of FOS, FOSB, CDKN1A, MDM2, and GADD45A, and downregulation of NRG1, H3C11, and CENPX. Gene ontology enrichment indicated activation of DNA damage checkpoint signaling, cell cycle arrest, and stress-response pathways, alongside suppression of nucleosome assembly and DNA replication processes. Machine learning models trained on transcriptomic features exhibited strong predictive performance across biodosimetric endpoints. Classification models accurately distinguished irradiated from sham samples (AUC > 0.99), and regression models achieved high accuracy for estimating both absorbed dose (R2 = 0.97) and days post-exposure (R2 = 0.99). The latter, while highly predictive, may partially reflect transcriptional shifts associated with progressive degradation of the in vitro tissue model over time. Collectively, these findings demonstrate that RNA-based molecular signatures from human skin tissue provide a robust framework for quantitative estimation of neutron radiation exposure and temporal response dynamics.

BackgroundSpaceflight-associated neuro-ocular syndrome (SANS) poses significant risks to astronaut visual health during long-duration missions, yet its underlying molecular mechanisms remain incompletely understood. Oxidative stress and apoptosis are candidate molecular drivers, but their transcriptomic signatures in spaceflight-exposed retinal tissue have not been systematically characterized. MethodsWe applied a machine learning ensemble of linear regression models to predict two ocular phenotypes: 4-hydroxynonenal (4-HNE) immunostaining as a marker of lipid peroxidation-mediated oxidative damage; and TUNEL positivity as a marker of apoptotic cell death. In this observational study, we use bulk retinal gene expression data obtained from a controlled experiment with ground control and spaceflown mice to predict these phenotypes. Gene Ontology pathway enrichment was performed on the most predictive gene sets for each phenotype. ResultsThe 4-HNE phenotype was predicted by genes that converge on membrane-associated pathways, photoreceptor protein modification, synaptic dysfunction, and extracellular matrix dysregulation, including B2m, Tf, Cnga1, mt-Nd1, Snap25, and Efemp1. The genes predicting the TUNEL phenotype revealed a distinct signature emphasizing stress-induced apoptosis, rod photoreceptor degeneration, and endoplasmic reticulum dysfunction, with Ddit4, Nrl, Rom1, Reep6, and Gabarapl1 emerging as central regulators. ConclusionsOxidative lipid peroxidation and apoptotic cell death represent complementary and molecularly distinct pathological mechanisms in spaceflight-exposed murine retinal tissue. The gene signatures provide a putative molecular framework for developing noninvasive biomarkers and therapeutic targets to monitor and protect astronaut visual health during long-duration and deep-space missions.

Head rotation is the leading cause of diffuse brain injuries from cycling accidents, with severe, long-term or even fatal consequences. Here, we present a novel helmet safety technology, the Release Layer System (RLS), designed to enhance conventional helmets and reduce the likelihood of such injuries. RLS is located on the outer side of the helmet and thus gets impacted first. The force of the impact activates a rolling mechanism triggering the release of an outer polycarbonate panel, thereby dispersing and transforming a substantial portion of the incident rotational energy. To evaluate the effectiveness of the technology, we conducted oblique impact tests on three popular helmet types, in conventional and RLS-equipped configurations, at three impact locations. RLS-equipped helmets reduced Peak Angular Velocity (PAV) by 57-66%, averaged across impact locations, compared to their conventional counterparts. This corresponds to a 68-86% reduction in the probability of an AIS2+ brain injury, as estimated by the Brain Injury Criterion. The most notable improvement was observed at the pYrot location (front impacts, mid-sagittal plane), with up to 85% PAV reduction. Testing across headforms further demonstrated the effectiveness of the technology in mitigating head rotation irrespective of variations in evaluation setups. This work introduces a novel mechanism for rotational impact mitigation and provides evidence of its potential benefits compared with conventional helmets. As an outer-layer approach, RLS may offer an alternative pathway for managing rotational kinematics in future helmet designs.

Traumatic joint injuries both disrupt chondrocyte metabolism and increase the risk for post-traumatic osteoarthritis. Yet the relationships between trauma, altered metabolism, and cartilage degradation remains unclear. This study compares the metabolic responses of bovine (normal) and osteoarthritic (OA) chondrocytes to physiological and injurious mechanical stimuli under normoxic (20% O2) and hypoxic (5% O2) conditions. Using primary chondrocytes encapsulated in agarose, physiological and injurious mechanical stimulation, targeted metabolomic profiling of central carbon metabolites, and O2 saturation measurements, we find that healthy bovine chondrocytes exhibit robust, time-dependent adaptation to mechanical stimuli, whereas OA chondrocytes display a blunted response, particularly under injury conditions. Injurious mechanical stimuli led to altered O2 consumption and glutamine accumulation, suggesting disrupted respiration and reduced protein synthesis hypothesized to be a result of altered mitochondrial metabolism in OA cells. These findings underscore the role of mechanical cues in chondrocyte metabolism and inform future studies aimed at identifying metabolic targets relevant to post-traumatic osteoarthritis progression.

1.IntroductionAir pollution (AirPoll) is a major environmental risk factor for age-related cognitive decline and dementia, yet we poorly understood the cellular and molecular mechanisms underlying its effects and their potential attenuation. MethodsWe combined single cell RNA sequencing with immunohistochemistry to determine transcriptional responses in microglia, astrocytes, neurons and neural stem cells in the hippocampus of mice following exposure to chronic diesel exhaust particle (DEP). Differential gene expression profiles were compared between filtered-air and DEP exposed animals. The gamma secretase modulator GSM-15606 (BPN) was used to probe selective rescue of inflammatory signatures across distinct cell populations. ResultsDEP exposure triggered robust inflammatory programs in microglia and astrocytes, including upregulation of cytokine signaling components, innate immune receptors, stress-responsive transcription factors, and markers of reactive glial phenotypes. In neural stem cells, DEP induced activation of gliosis-associated pathways, including Il6st, Stat3, and Txnip, consistent with a pro-inflammatory state that may bias lineage decisions. Immunostaining confirmed a significant reduction in immature neurons in the neurogenic niche after AirPoll exposure. GSM-15606 attenuated many DEP-induced transcriptional alterations in microglia and astrocytes, reducing expression of inflammatory mediators and reactive gliosis markers, but did not modulate the inflammatory profile of neural stem cells. ConclusionsAirPoll activates divergent inflammatory pathways across hippocampal cell populations and suppresses neurogenesis. Targeting inflammation with GSM-15606 selectively reverses glial but not neural stem cell responses, highlighting cell-type-specific mechanisms and potential therapeutic pathways to mitigate pollution-related cognitive vulnerability. These results support GSM-15606 as a protective agent against AirPoll-induced hippocampal dysfunction and amyloidogenic stress.

In "Experiment-free exoskeleton assistance via learning in simulation", Luo et al. [1] present an ambitious framework for developing exoskeleton controllers through reinforcement learning exclusively in computer simulation. The authors report that a control policy trained on a small dataset from one subject was directly transferred to physical hardware, reducing human metabolic cost during walking, running, and stair climbing by more than any prior device. If confirmed, this would represent a major breakthrough for the field of wearable robotics and their clinical applications. However, a close examination of the published materials casts doubt on these claims. The reported experimental results violate physiological limits on the relationship between mechanical power and muscle energy use during gait2,3,4. The algorithmic claims are surprising and cannot be verified; in contrast with established replicability standards in machine learning5,6, executable code has not been made available. We conclude that the goals of this study have not yet been verifiably achieved and make recommendations for avoiding publication errors of this type in the future.

Eye movements enable visual information gathering and stabilize gaze via optokinetic (OKR) and vestibulo-ocular reflex (VOR) pathways.1 Echolocating bats, despite their rapid and agile flight maneuvers to land upside down and navigate 3D space, have long been thought not to move their eyes, an assumption originating from Wallss influential assertion over 80 years ago2 but never tested with empirical measurements. Here we present quantitative analysis of eye movements driven by visual and vestibular signals in Sebas short-tailed bat (Carollia perspicillata). Bats generated robust visually driven OKR with an oculomotor range of [~]{+/-}10{degrees}, and displayed strong otolith-mediated responses during off-vertical axis rotation. In contrast, they showed minimal semicircular canal-driven angular VOR (aVOR) for passive head rotations that elicit large, sustained responses in mice. Micro-CT reconstructions revealed that bats and mice have similar semicircular canal geometry, indicating that the weak aVOR does not reflect peripheral anatomical constraints. These findings provide the first empirical demonstration that bats make robust eye movements and exhibit strong visual and otolith-driven components of gaze stabilization. We propose that semicircular canal signals may be more strongly engaged during active flight and modulated by behavioral state-dependent tuning of vestibular pathways to support ecologically specialized behaviors.

Preserving biodiversity requires the genetic monitoring of wild populations, but traditional invasive sampling techniques can impact animal welfare. For cetaceans, a promising non-invasive approach is the collection of exhaled respiratory vapour, or blow, to generate individual genetic profiles. Here, we demonstrate the feasibility of generating whole genomes from the blow of humpback whales with data of sufficient quality for population genomics. A total of 58 blow samples from 26 Northeast Pacific humpback whales (Megaptera novaeangliae) were collected in Gitgaat First Nation territory using a commercially available drone. The high endogenous content at 84% on average allowed us to generate low-coverage nuclear genomes (mean 2.3x, range 0.2x-3.5x) and high coverage mitochondrial genomes (mean 94x, range 7.7x-151.3x) for inference of population structure, diversity and phylogenomics. The reliability of the blow-derived genomes was demonstrated by direct comparison between replicate blow samples, as well as paired tissue samples from a subset of individuals.

The core biopolymers (DNA, RNA and proteins) are assembled from their monomers under conditions that avoid water. RNA is crucial for the Origin of Life. When cleaved from its polymerized state, RNA first transitions to nucleoside 2,3-cyclic phosphates. In the reverse direction, RNA polymerizes from 2,3-cyclic monomers in dry states, creating short oligomers that then can ligate on a template under aqueous, alkaline conditions. We studied the role of the counterions in polymerization of 2,3-cyclic nucleotides under geologically plausible settings. Through experiments and simulations, we demonstrate that the presence of ammonium and alkylammonium counterions greatly improves RNA polymerization. The otherwise less reactive cytidine containing monomers formed polyC sequences of up to heptamers; copolymers of AU, GC, or GCAU were detected up to hexamers. Our findings suggest three reasons for this: (1) (Alkyl)ammonium cations form hydrogen bonds with phosphates, (2) their alkaline pKa value can trigger general base catalysis, and (3) (alkyl)ammonium salts naturally form dry, anhydrous materials. The findings indicate that pyrolyzed organic tars creating ammonia-rich gas pockets in subsurface rocks could have enhanced the early evolution of RNA. TOC image O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/713775v1_ufig1.gif" ALT="Figure 1"> View larger version (112K): org.highwire.dtl.DTLVardef@1adc431org.highwire.dtl.DTLVardef@12b8da0org.highwire.dtl.DTLVardef@5f187dorg.highwire.dtl.DTLVardef@140ed1a_HPS_FORMAT_FIGEXP M_FIG C_FIG

Air pollution has been increasingly linked to adverse neurodevelopmental and neurodegenerative outcomes. While experimental and preclinical studies suggest that exposure to particulate matter (PM), particularly during gestation, may disrupt cognitive development, the impact of short-term PM exposure on cognitive and behavioral functioning in healthy young populations remains insufficiently explored in Spain. Moreover, few studies have incorporated individualized dosimetry models to estimate exposure more accurately. This study included 186 healthy young adults (mean age = 20.4 years) recruited from three Spanish cities (Teruel, Almeria, and Talavera) characterized by different pollution levels. Ambient fine and coarse PM concentrations were recorded 8, 15, and 30 days prior to psychological assessment. Instead of relying solely on raw in situ environmental measurements, individualized PM deposition was estimated using the Multiple-Path Particle Dosimetry Model (MPPD), allowing a more biologically meaningful exposure approximation. Psychological outcomes were assessed using validated questionnaires: DASS-21 (depression, anxiety, stress), BIS-11 (impulsivity), UCLA Loneliness Scale, and SWLS (life satisfaction). Behavioral performance was evaluated using computerized versions of the Attentional Network Task (ANT) and the Stroop Task. Blood NRF2 concentrations were analyzed as a biomarker potentially related to oxidative stress mechanisms. In situ data indicated that Talavera presented the highest pollution levels, followed by Almeria and Teruel. Linear regression analyses showed that coarse PM exposure across 8-, 15-, and 30-day windows significantly predicted poorer Executive Control Index performance in the ANT. Additionally, 15-day coarse PM and 30-day fine PM exposure were associated with greater cognitive interference. Oxidative stress markers were significantly associated with PM exposure levels. These findings support emerging evidence that short-term PM exposure may negatively affect executive and attentional processes even in healthy young adults. Further longitudinal research incorporating individualized exposure modeling is warranted to clarify causal pathways and underlying biological mechanisms. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=97 SRC="FIGDIR/small/713644v1_ufig1.gif" ALT="Figure 1"> View larger version (79K): org.highwire.dtl.DTLVardef@1a0ac13org.highwire.dtl.DTLVardef@1812accorg.highwire.dtl.DTLVardef@120bf07org.highwire.dtl.DTLVardef@dd9a7c_HPS_FORMAT_FIGEXP M_FIG C_FIG