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Differentiation is crucial for multicellularity. However, it is inherently susceptible to mutant cells that fail to differentiate. These mutants outcompete normal cells by excessive self-renewal. It remains unclear what mechanisms can resist such mutant expansion. Here, we demonstrate a solution by engineering a synthetic differentiation circuit in Escherichia coli that selects against these mutants via a biphasic fitness strategy. The circuit provides tunable production of synthetic analogs of stem, progenitor, and differentiated cells. It resists mutations by coupling differentiation to the production of an essential enzyme, thereby disadvantaging non-differentiating mutants. The circuit selected for and maintained a positive differentiation rate in long-term evolution. Surprisingly, this rate remained constant across vast changes in growth conditions. We found that transit-amplifying cells (fast-growing progenitors) underlie this environmental robustness. Our results provide insight into the stability of differentiation and demonstrate a powerful method for engineering evolutionarily stable multicellular consortia.
Assuntos
Escherichia coli , Biologia Sintética , Diferenciação Celular , Escherichia coli/citologia , Escherichia coli/genética , Integrases/metabolismo , Biologia Sintética/métodos , Aptidão Genética , Farmacorresistência BacterianaRESUMO
In the prevailing model, Lgr5+ cells are the only intestinal stem cells (ISCs) that sustain homeostatic epithelial regeneration by upward migration of progeny through elusive upper crypt transit-amplifying (TA) intermediates. Here, we identify a proliferative upper crypt population marked by Fgfbp1, in the location of putative TA cells, that is transcriptionally distinct from Lgr5+ cells. Using a kinetic reporter for time-resolved fate mapping and Fgfbp1-CreERT2 lineage tracing, we establish that Fgfbp1+ cells are multi-potent and give rise to Lgr5+ cells, consistent with their ISC function. Fgfbp1+ cells also sustain epithelial regeneration following Lgr5+ cell depletion. We demonstrate that FGFBP1, produced by the upper crypt cells, is an essential factor for crypt proliferation and epithelial homeostasis. Our findings support a model in which tissue regeneration originates from upper crypt Fgfbp1+ cells that generate progeny propagating bi-directionally along the crypt-villus axis and serve as a source of Lgr5+ cells in the crypt base.
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Mucosa Intestinal , Receptores Acoplados a Proteínas G , Receptores Acoplados a Proteínas G/metabolismo , Animais , Camundongos , Mucosa Intestinal/metabolismo , Mucosa Intestinal/citologia , Células-Tronco/metabolismo , Células-Tronco/citologia , Linhagem da Célula , Regeneração , Proliferação de Células , Células Epiteliais/metabolismo , Células Epiteliais/citologia , Camundongos Endogâmicos C57BL , HomeostaseRESUMO
The gastrointestinal tract is in a state of constant motion. These movements are tightly regulated by the presence of food and help digestion by mechanically breaking down and propelling gut content. Mechanical sensing in the gut is thought to be essential for regulating motility; however, the identity of the neuronal populations, the molecules involved, and the functional consequences of this sensation are unknown. Here, we show that humans lacking PIEZO2 exhibit impaired bowel sensation and motility. Piezo2 in mouse dorsal root, but not nodose ganglia is required to sense gut content, and this activity slows down food transit rates in the stomach, small intestine, and colon. Indeed, Piezo2 is directly required to detect colon distension in vivo. Our study unveils the mechanosensory mechanisms that regulate the transit of luminal contents throughout the gut, which is a critical process to ensure proper digestion, nutrient absorption, and waste removal.
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Trânsito Gastrointestinal , Canais Iônicos , Mecanotransdução Celular , Animais , Humanos , Camundongos , Digestão , Canais Iônicos/metabolismo , Neurônios/metabolismoRESUMO
Macrophages are highly heterogeneous tissue-resident immune cells that perform a variety of tissue-supportive functions. The current paradigm dictates that intestinal macrophages are continuously replaced by incoming monocytes that acquire a pro-inflammatory or tissue-protective signature. Here, we identify a self-maintaining population of macrophages that arise from both embryonic precursors and adult bone marrow-derived monocytes and persists throughout adulthood. Gene expression and imaging studies of self-maintaining macrophages revealed distinct transcriptional profiles that reflect their unique localization (i.e., closely positioned to blood vessels, submucosal and myenteric plexus, Paneth cells, and Peyer's patches). Depletion of self-maintaining macrophages resulted in morphological abnormalities in the submucosal vasculature and loss of enteric neurons, leading to vascular leakage, impaired secretion, and reduced intestinal motility. These results provide critical insights in intestinal macrophage heterogeneity and demonstrate the strategic role of self-maintaining macrophages in gut homeostasis and intestinal physiology.
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Intestinos/imunologia , Macrófagos/imunologia , Animais , Padronização Corporal/fisiologia , Diferenciação Celular/genética , Diferenciação Celular/imunologia , Motilidade Gastrointestinal/imunologia , Motilidade Gastrointestinal/fisiologia , Homeostase , Inflamação/imunologia , Mucosa Intestinal/imunologia , Intestino Delgado/metabolismo , Camundongos , Monócitos/metabolismo , Neurônios/metabolismo , Fagócitos/imunologia , TranscriptomaRESUMO
Transit-amplifying (TA) cells are progenitors that undergo an amplification phase followed by transition into an extinction phase. A long postulated epidermal TA progenitor with biphasic behavior has not yet been experimentally observed in vivo. Here, we identify such a TA population using clonal analysis of Aspm-CreER genetic cell-marking in mice, which uncovers contribution to both homeostasis and injury repair of adult skin. This TA population is more frequently dividing than a Dlx1-CreER-marked long-term self-renewing (e.g. stem cell) population. Newly developed generalized birth-death modeling of long-term lineage tracing data shows that both TA progenitors and stem cells display neutral competition, but only the stem cells display neutral drift. The quantitative evolution of a nascent TA cell and its direct descendants shows that TA progenitors indeed amplify the basal layer before transition and that the homeostatic TA population is mostly in extinction phase. This model will be broadly useful for analyzing progenitors whose behavior changes with their clone age. This work identifies a long-missing class of non-self-renewing biphasic epidermal TA progenitors and has broad implications for understanding tissue renewal mechanisms.
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Células Epidérmicas , Epiderme , Células-Tronco , Animais , Camundongos , Células-Tronco/citologia , Células-Tronco/metabolismo , Células Epidérmicas/citologia , Células Epidérmicas/metabolismo , Epiderme/metabolismo , Proliferação de Células , Linhagem da Célula , Homeostase , Diferenciação Celular , Autorrenovação Celular/fisiologiaRESUMO
Although the mammalian microbiota is well contained within the intestine, it profoundly shapes development and metabolism of almost every host organ. We questioned the range and depth of microbial metabolite penetration into the host, and how this is modulated by intestinal immunity. Chemically identical microbial and host metabolites were distinguished by stable isotope tracing from 13C-labeled live non-replicating Escherichia coli, differentiating 12C host isotopes with high-resolution mass spectrometry. Hundreds of endogenous microbial compounds penetrated 23 host tissues and fluids after intestinal exposure: subsequent 12C host metabolome signatures included lipidemia, reduced glycolysis, and inflammation. Penetrant bacterial metabolites from the small intestine were rapidly cleared into the urine, whereas induced antibodies curtailed microbial metabolite exposure by accelerating intestinal bacterial transit into the colon where metabolite transport mechanisms are limiting. Pervasive penetration of microbial molecules can cause extensive host tissue responses: these are limited by immune and non-immune intestinal mucosal adaptations to the microbiota.
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Anticorpos/metabolismo , Microbioma Gastrointestinal/fisiologia , Glicólise/imunologia , Hiperlipidemias/imunologia , Inflamação/imunologia , Mamíferos/imunologia , Animais , Anticorpos/imunologia , Radioisótopos de Carbono/análise , Interações Hospedeiro-Patógeno , Imunidade , Cadeias Pesadas de Imunoglobulinas/genética , Espectrometria de Massas , Camundongos , Camundongos Endogâmicos C57BL , Camundongos KnockoutRESUMO
Studying â¼200,000 evictions filed against â¼300,000 Philadelphians from 2005 to 2021, we focus on the role of transit to court in preventing tenants from asserting their rights. In this period, nearly 40% of tenants facing eviction were ordered to leave their residences because they did not show up to contest cases against them and received a default judgment. Controlling for a variety of potential confounds at the tenant and landlord level, we find that residents of private tenancies with longer transit travel time to the courthouse were more likely to default. A 1-h increase in estimated travel time increases the probability of default by between 3.8% and 8.6% points across different model specifications. The effect holds after adjusting for direct distance to the court, unobserved landlord characteristics, and even baseline weekend travel time. However, it is absent in public housing evictions, where timing rules are significantly laxer, and during the COVID-19 pandemic, when tenants had the opportunity to be present virtually. We estimate that had all tenants been equally able to get to the court in 10 min, there would have been 4,000 to 9,000 fewer default evictions over the sample period. We replicate this commuting effect in another dataset of over 800,000 evictions from Harris County, Texas. These results open up a new way to study the physical determinants of access to justice, illustrating that the location and accessibility of a courthouse can affect individual case outcomes. We suggest that increased use of video technology in court may reduce barriers to justice.
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COVID-19 , Pessoas Mal Alojadas , Humanos , Pandemias , COVID-19/epidemiologia , Habitação , TexasRESUMO
We investigate the underlying distribution of orbital eccentricities for planets around early-to-mid M dwarf host stars. We employ a sample of 163 planets around early- to mid-M dwarfs across 101 systems detected by NASA's Kepler Mission. We constrain the orbital eccentricity for each planet by leveraging the Kepler lightcurve together with a stellar density prior, constructed using metallicity from spectroscopy, Ks magnitude from 2MASS, and stellar parallax from Gaia. Within a Bayesian hierarchical framework, we extract the underlying eccentricity distribution, assuming alternately Rayleigh, half-Gaussian, and Beta functions for both single- and multi-transit systems. We described the eccentricity distribution for apparently single-transiting planetary systems with a Rayleigh distribution with [Formula: see text], and for multitransit systems with [Formula: see text]. The data suggest the possibility of distinct dynamically warmer and cooler subpopulations within the single-transit distribution: The single-transit data prefer a mixture model composed of two distinct Rayleigh distributions with [Formula: see text] and [Formula: see text] over a single Rayleigh distribution, with 7:1 odds. We contextualize our findings within a planet formation framework, by comparing them to analogous results in the literature for planets orbiting FGK stars. By combining our derived eccentricity distribution with other M dwarf demographic constraints, we estimate the underlying eccentricity distribution for the population of early- to mid-M dwarf planets in the local neighborhood.
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A continuum from stem to transit-amplifying to a differentiated cell state is a common theme in multicellular organisms. In the plant root apical meristem (RAM), transit-amplifying cells are organized into two domains: cells from the proliferation domain (PD) are displaced to the transition domain (TD), suggesting that both domains are necessarily coupled. Here, we show that in the Arabidopsis thaliana mto2-2 mutant, in which threonine (Thr) synthesis is affected, the RAM lacks the PD. Through a combination of cell length profile analysis, mathematical modeling and molecular markers, we establish that the PD and TD can be uncoupled. Remarkably, although the RAM of mto2-2 is represented solely by the TD, the known factors of RAM maintenance and auxin signaling are expressed in the mutant. Mathematical modeling predicts that the stem cell niche depends on Thr metabolism and that, when disturbed, the normal continuum of cell states becomes aborted.
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Proteínas de Arabidopsis , Arabidopsis , Meristema/genética , Meristema/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Treonina/genética , Arabidopsis/genética , Arabidopsis/metabolismo , Mutação/genética , Proliferação de Células/genética , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Regulação da Expressão Gênica de PlantasRESUMO
Targeting heterologous multi-transmembrane domain (TMD) proteins to plant chloroplasts requires sequences in addition to the chloroplast transit peptide (cTP). The N-terminal domain (N-region), located C-terminal to the cTP in chloroplast inner envelope membrane proteins, is an essential region for import. However, it was unclear if the N-region functions solely as a spacer sequence to facilitate cTP access or if it plays an active role in the import process. This study addresses the N-region's role by using combinations of cTPs and N-regions from Arabidopsis chloroplast inner envelope membrane proteins to direct the cyanobacterial protein SbtA to the chloroplast. We find that the sequence context of the N-region affects the chloroplast import efficiency of SbtA, with particular sequences mis-targeting the protein to different cellular sub-compartments. Additionally, specific cTP and N-region pairs exhibit varying targeting efficiencies for different heterologous proteins. Substituting individual N-region motifs did not significantly alter the chloroplast targeting efficiency of a particular cTP and N-region pair. We conclude that the N-region exhibits contextual functioning and potentially functional redundancy in motifs.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Proteínas de Cloroplastos , Cloroplastos , Transporte Proteico , Cloroplastos/metabolismo , Arabidopsis/metabolismo , Arabidopsis/genética , Proteínas de Cloroplastos/metabolismo , Proteínas de Cloroplastos/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Sinais Direcionadores de Proteínas , Domínios Proteicos , Sequência de Aminoácidos , Proteínas de Membrana/metabolismo , Proteínas de Membrana/genéticaRESUMO
Stem cells self-renew or give rise to transit-amplifying cells (TACs) that differentiate into specific functional cell types. The fate determination of stem cells to TACs and their transition to fully differentiated progeny is precisely regulated to maintain tissue homeostasis. Arid1a, a core component of the switch/sucrose nonfermentable complex, performs epigenetic regulation of stage- and tissue-specific genes that is indispensable for stem cell homeostasis and differentiation. However, the functional mechanism of Arid1a in the fate commitment of mesenchymal stem cells (MSCs) and their progeny is not clear. Using the continuously growing adult mouse incisor model, we show that Arid1a maintains tissue homeostasis through limiting proliferation, promoting cell cycle exit and differentiation of TACs by inhibiting the Aurka-Cdk1 axis. Loss of Arid1a overactivates the Aurka-Cdk1 axis, leading to expansion of the mitotic TAC population but compromising their differentiation ability. Furthermore, the defective homeostasis after loss of Arid1a ultimately leads to reduction of the MSC population. These findings reveal the functional significance of Arid1a in regulating the fate of TACs and their interaction with MSCs to maintain tissue homeostasis.
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Aurora Quinase A/metabolismo , Proteína Quinase CDC2/metabolismo , Proteínas de Ligação a DNA/metabolismo , Incisivo/embriologia , Células-Tronco Mesenquimais/metabolismo , Mitose , Transdução de Sinais , Fatores de Transcrição/metabolismo , Animais , Aurora Quinase A/genética , Proteína Quinase CDC2/genética , Proteínas de Ligação a DNA/genética , Camundongos , Camundongos Transgênicos , Fatores de Transcrição/genéticaRESUMO
PURPOSE: Abnormalities in cerebral veins are a common finding in many neurological diseases, yet there is a scarcity of MRI techniques to assess venous hemodynamic function. The present study aims to develop a noncontrast technique to measure a novel blood flow circulatory measure, venous transit time (VTT), which denotes the time it takes for water to travel from capillary to major veins. METHODS: The proposed sequence, venous transit time imaging by changes in T1 relaxation (VICTR), is based on the notion that as water molecules transition from the tissue into the veins, they undergo a change in T1 relaxation time. The validity of the measured VTT was tested by studying the VTT along the anatomically known flow trajectory of venous vessels as well as using a physiological vasoconstrictive challenge of caffeine ingestion. Finally, we compared the VTT measured with VICTR MRI to a bolus-tracking method using gadolinium-based contrast agent. RESULTS: VTT was measured to be 3116.3 ± 326.0 ms in the posterior superior sagittal sinus (SSS), which was significantly longer than 2865.0 ± 390.8 ms at the anterior superior sagittal sinus (p = 0.004). The test-retest assessment showed an interclass correlation coefficient of 0.964. VTT was significantly increased by 513.8 ± 239.3 ms after caffeine ingestion (p < 0.001). VTT measured with VICTR MRI revealed a strong correlation (R = 0.84, p = 0.002) with that measured with the contrast-based approach. VTT was found inversely correlated to cerebral blood flow and venous oxygenation across individuals. CONCLUSION: A noncontrast MRI technique, VICTR MRI, was developed to measure the VTT of the brain.
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Veias Cerebrais , Imageamento por Ressonância Magnética , Humanos , Masculino , Adulto , Feminino , Velocidade do Fluxo Sanguíneo/fisiologia , Veias Cerebrais/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Circulação Cerebrovascular/fisiologia , Reprodutibilidade dos Testes , Cafeína/farmacologia , Meios de Contraste , Adulto Jovem , Processamento de Imagem Assistida por Computador/métodos , Hemodinâmica , Angiografia por Ressonância Magnética/métodosRESUMO
Accurate assessment of cerebral perfusion is vital for understanding the hemodynamic processes involved in various neurological disorders and guiding clinical decision-making. This guidelines article provides a comprehensive overview of quantitative perfusion imaging of the brain using multi-timepoint arterial spin labeling (ASL), along with recommendations for its acquisition and quantification. A major benefit of acquiring ASL data with multiple label durations and/or post-labeling delays (PLDs) is being able to account for the effect of variable arterial transit time (ATT) on quantitative perfusion values and additionally visualize the spatial pattern of ATT itself, providing valuable clinical insights. Although multi-timepoint data can be acquired in the same scan time as single-PLD data with comparable perfusion measurement precision, its acquisition and postprocessing presents challenges beyond single-PLD ASL, impeding widespread adoption. Building upon the 2015 ASL consensus article, this work highlights the protocol distinctions specific to multi-timepoint ASL and provides robust recommendations for acquiring high-quality data. Additionally, we propose an extended quantification model based on the 2015 consensus model and discuss relevant postprocessing options to enhance the analysis of multi-timepoint ASL data. Furthermore, we review the potential clinical applications where multi-timepoint ASL is expected to offer significant benefits. This article is part of a series published by the International Society for Magnetic Resonance in Medicine (ISMRM) Perfusion Study Group, aiming to guide and inspire the advancement and utilization of ASL beyond the scope of the 2015 consensus article.
Assuntos
Encéfalo , Circulação Cerebrovascular , Marcadores de Spin , Humanos , Encéfalo/diagnóstico por imagem , Encéfalo/irrigação sanguínea , Circulação Cerebrovascular/fisiologia , Processamento de Imagem Assistida por Computador/métodos , Angiografia por Ressonância Magnética/métodos , Imageamento por Ressonância Magnética/métodos , Imagem de PerfusãoRESUMO
PURPOSE: Quantitative mapping of brain perfusion, diffusion, T2 *, and T1 has important applications in cerebrovascular diseases. At present, these sequences are performed separately. This study aims to develop a novel MRI technique to simultaneously estimate these parameters. METHODS: This sequence to measure perfusion, diffusion, T2 *, and T1 mapping with magnetic resonance fingerprinting (MRF) was based on a previously reported MRF-arterial spin labeling (ASL) sequence, but the acquisition module was modified to include different TEs and presence/absence of bipolar diffusion-weighting gradients. We compared parameters derived from the proposed method to those derived from reference methods (i.e., separate sequences of MRF-ASL, conventional spin-echo DWI, and T2 * mapping). Test-retest repeatability and initial clinical application in two patients with stroke were evaluated. RESULTS: The scan time of our proposed method was 24% shorter than the sum of the reference methods. Parametric maps obtained from the proposed method revealed excellent image quality. Their quantitative values were strongly correlated with those from reference methods and were generally in agreement with values reported in the literature. Repeatability assessment revealed that ADC, T2 *, T1 , and B1 + estimation was highly reliable, with voxelwise coefficient of variation (CoV) <5%. The CoV for arterial transit time and cerebral blood flow was 16% ± 3% and 25% ± 9%, respectively. The results from the two patients with stroke demonstrated that parametric maps derived from the proposed method can detect both ischemic and hemorrhagic stroke. CONCLUSION: The proposed method is a promising technique for multi-parametric mapping and has potential use in patients with stroke.
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Imageamento por Ressonância Magnética , Acidente Vascular Cerebral , Humanos , Imageamento por Ressonância Magnética/métodos , Encéfalo/diagnóstico por imagem , Encéfalo/irrigação sanguínea , Espectroscopia de Ressonância Magnética , Perfusão , Acidente Vascular Cerebral/diagnóstico por imagem , Imagens de Fantasmas , Processamento de Imagem Assistida por Computador/métodosRESUMO
Water exchange rate (Kw) across the blood-brain barrier (BBB) is an important physiological parameter that may provide new insight into ageing and neurodegenerative disease. Recently, two non-invasive arterial spin labelling (ASL) MRI methods have been developed to measure Kw, but results from the different methods have not been directly compared. Furthermore, the association of Kw with age for each method has not been investigated in a single cohort. Thirty participants (70% female, 63.8 ± 10.4 years) were scanned at 3 T with Diffusion-Prepared ASL (DP-ASL) and Multi-Echo ASL (ME-ASL) using previously implemented acquisition and analysis protocols. Grey matter Kw, cerebral blood flow (CBF) and arterial transit time (ATT) were extracted. CBF values were consistent; approximately 50 ml/min/100 g for both methods, and a strong positive correlation in CBF from both methods across participants (r = 0.82, p < 0.001). ATT was significantly different between methods (on average 147.7 ms lower when measured with DP-ASL compared to ME-ASL) but was positively correlated across participants (r = 0.39, p < 0.05). Significantly different Kw values of 106.6 ± 19.7 min-1 and 306.8 ± 71.7 min-1 were measured using DP-ASL and ME-ASL, respectively, and DP-ASL Kw and ME-ASL Kw were negatively correlated across participants (r = -0.46, p < 0.01). Kw measured using ME-ASL had a significant linear relationship with age (p < 0.05). In conclusion, DP-ASL and ME-ASL provided estimates of Kw with significantly different quantitative values and inconsistent dependence with age. We propose future standardisation of modelling and fitting methods for DP-ASL and ME-ASL, to evaluate the effect on Kw quantification. Also, sensitivity and bias analyses should be performed for both approaches, to assess the effect of varying acquisition and fitting parameters. Lastly, comparison with independent measures of BBB water transport, and with physiological and clinical biomarkers known to be associated with changes in BBB permeability, are essential to validate the ASL methods, and to demonstrate their clinical utility.
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Arterial spin labeling (ASL) and dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI) have shown potential for differentiating tumor progression from pseudoprogression. For pseudocontinuous ASL with a single postlabeling delay, the presence of delayed arterial transit times (ATTs) could affect the evaluation of ASL-MRI perfusion data. In this study, the influence of ATT artifacts on the perfusion assessment and differentiation between tumor progression and pseudoprogression were studied. This study comprised 66 adult patients (mean age 60 ± 13 years; 40 males) with a histologically confirmed glioblastoma who received postoperative radio (chemo)therapy. ASL-MRI and DSC-MRI scans were acquired at 3 months postradiotherapy as part of the standard clinical routine. These scans were visually scored regarding (i) the severity of ATT artifacts (%) on the ASL-MRI scans only, scored by two neuroradiologists; (ii) perfusion of the enhancing tumor lesion; and (iii) radiological evaluation of tumor progression versus pseudoprogression by one neuroradiologist. The final outcome was based on combined clinical and radiological follow-up until 9 months postradiotherapy. ATT artifacts were identified in all patients based on the mean scores of two raters. A significant difference between the radiological evaluation of ASL-MRI and DSC-MRI was observed only for ASL images with moderate ATT severity (30%-65%). The perfusion assessment showed ASL-MRI tending more towards hyperperfusion than DSC-MRI in the case of moderate ATT artifacts. In addition, there was a significant difference between the prediction of tumor progression with ASL-MRI and the final outcome in the case of severe ATT artifacts (McNemar test, p = 0.041). Despite using ASL imaging parameters close to the recommended settings, ATT artifacts frequently occur in patients with treated brain tumors. Those artifacts could hinder the radiological evaluation of ASL-MRI data and the detection of true disease progression, potentially affecting treatment decisions for patients with glioblastoma.
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Neoplasias Encefálicas , Progressão da Doença , Glioblastoma , Marcadores de Spin , Humanos , Glioblastoma/diagnóstico por imagem , Glioblastoma/patologia , Pessoa de Meia-Idade , Masculino , Feminino , Neoplasias Encefálicas/diagnóstico por imagem , Neoplasias Encefálicas/patologia , Imageamento por Ressonância Magnética , Idoso , Artefatos , Adulto , Fatores de Tempo , Diagnóstico Diferencial , Angiografia por Ressonância Magnética , Artérias/diagnóstico por imagem , Artérias/patologiaRESUMO
This study aimed to implement a physics-informed unsupervised deep neural network (DNN) to estimate cerebral blood flow (CBF) and arterial transit time (ATT) from multi-delay arterial spin labeling (ASL), and compare its performance with that of a supervised DNN and the conventional method. Supervised and unsupervised DNNs were trained using simulation data. The accuracy and noise immunity of the three methods were compared using simulations and in vivo data. The simulation study investigated the differences between the predicted and ground-truth values and their variations with the noise level. The in vivo study evaluated the predicted values from the original images and noise-induced variations in the predicted values from the synthesized noisy images by adding Rician noise to the original images. The simulation study showed that CBF estimated using the supervised DNN was not biased by noise, whereas that estimated using other methods had a positive bias. Although the ATT with all methods exhibited a similar behavior with noise increase, the ATT with the supervised DNN was less biased. The in vivo study showed that CBF and ATT with the supervised DNN were the most accurate and that the supervised and unsupervised DNNs had the highest noise immunity in CBF and ATT estimations, respectively. Physics-informed unsupervised learning can estimate CBF and ATT from multi-delay ASL signals, and its performance is superior to that of the conventional method. Although noise immunity in ATT estimation was superior with unsupervised learning, other performances were superior with supervised learning.
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Circulação Cerebrovascular , Imageamento por Ressonância Magnética , Marcadores de Spin , Circulação Cerebrovascular/fisiologia , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Adulto , Feminino , Simulação por Computador , Física , Redes Neurais de Computação , Aprendizado Profundo , Aprendizado de Máquina Supervisionado , Aprendizado de Máquina não Supervisionado , Encéfalo/diagnóstico por imagem , Encéfalo/irrigação sanguínea , Encéfalo/fisiologiaRESUMO
Increasing hurricane frequency and intensity with climate change is likely to affect soil organic carbon (C) stocks in tropical forests. We examined the cycling of C between soil pools and with depth at the Luquillo Experimental Forest in Puerto Rico in soils over a 30-year period that spanned repeated hurricanes. We used a nonlinear matrix model of soil C pools and fluxes ("soilR") and constrained the parameters with soil and litter survey data. Soil chemistry and stable and radiocarbon isotopes were measured from three soil depths across a topographic gradient in 1988 and 2018. Our results suggest that pulses and subsequent reduction of inputs caused by severe hurricanes in 1989, 1998, and two in 2017 led to faster mean transit times of soil C in 0-10 cm and 35-60 cm depths relative to a modeled control soil with constant inputs over the 30-year period. Between 1988 and 2018, the occluded C stock increased and δ13C in all pools decreased, while changes in particulate and mineral-associated C were undetectable. The differences between 1988 and 2018 suggest that hurricane disturbance results in a dilution of the occluded light C pool with an influx of young, debris-deposited C, and possible microbial scavenging of old and young C in the particulate and mineral-associated pools. These effects led to a younger total soil C pool with faster mean transit times. Our results suggest that the increasing frequency of intense hurricanes will speed up rates of C cycling in tropical forests, making soil C more sensitive to future tropical forest stressors.
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Tempestades Ciclônicas , Solo , Carbono , Florestas , MineraisRESUMO
Soils store large quantities of carbon in the subsoil (below 0.2 m depth) that is generally old and believed to be stabilized over centuries to millennia, which suggests that subsoil carbon sequestration (CS) can be used as a strategy for climate change mitigation. In this article, we review the main biophysical processes that contribute to carbon storage in subsoil and the main mathematical models used to represent these processes. Our guiding objective is to review whether a process understanding of soil carbon movement in the vertical profile can help us to assess carbon storage and persistence at timescales relevant for climate change mitigation. Bioturbation, liquid phase transport, belowground carbon inputs, mineral association, and microbial activity are the main processes contributing to the formation of soil carbon profiles, and these processes are represented in models using the diffusion-advection-reaction paradigm. Based on simulation examples and measurements from carbon and radiocarbon profiles across biomes, we found that advective and diffusive transport may only play a secondary role in the formation of soil carbon profiles. The difference between vertical root inputs and decomposition seems to play a primary role in determining the shape of carbon change with depth. Using the transit time of carbon to assess the timescales of carbon storage of new inputs, we show that only small quantities of new carbon inputs travel through the profile and can be stabilized for time horizons longer than 50 years, implying that activities that promote CS in the subsoil must take into consideration the very small quantities that can be stabilized in the long term.
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Sequestro de Carbono , Carbono , Mudança Climática , Solo , EcossistemaRESUMO
BACKGROUND AIMS: Dendritic cell (DC)-based immunotherapy is a promising approach to treat cancer. However, key aspects governing the reproducible manufacturing of high-quality DC remain incompletely defined. Here, we show that the time window between leukapheresis and DC manufacturing is critical. METHODS: Transcriptomic profiling by RNA-seq was used to unbiasedly characterize cellular states during each step of DC manufacturing process, and functional assays were used to determine the anti-tumor activities of DC. RESULTS: During preclinical development of a DC-based cytotherapy platform, CUD-002 (NCT05270720), we found that DC quality varied among different batches, even though commonly used DC maturation markers CD80, CD83 and CD86 were indistinguishable. Multivariate analysis indicated that DC quality was negatively associated with the shipping time from the leukapheresis site to the manufacturing center. To investigate the potential effect of shipping time, we stored leukapheresis materials from three donors for 0, 1, 2 or 3 days before DC manufacturing. For each step, we carried out RNA-seq analysis to unbiasedly characterize cellular states. Integrated bioinformatic analyses indicated that longer storage time reduced the expression of several transcription factors to attenuate interferon pathways. CONCLUSIONS: Consistently, we found that 3-day storage of leukapheresis materials significantly lowered the efficiency to generate DC but also impaired DC responses to inflammatory signals, resulting in inferior antigen-presentation and cytotoxic T-cell activities. Thus, we recommend using leukapheresis materials within 48 h to manufacture therapeutic DCs.