Gas Exchange Efficiency Research Articles

Gill morphology of two killifish species acclimated to the extreme euryhaline environment: A histological and ultrastructural analysis (Actinopterygii: Aphaniidae)

AbstractKillifishes (family Aphaniidae) in southern Iran demonstrate long‐time acclimation to extreme euryhaline environments. This study provides a detailed histological and ultrastructural characterization of gill morphology in two sympatric endemic aphaniids, Aphaniops furcatus and Aphaniops hormuzensis, inhabiting an ecologically extreme environment in southern Iran. Specimens were collected from the Khurgu hot‐sulphuric spring in the Hormozgan River System which drains into the Persian Gulf, and examined using haematoxylin and eosin (H&E) staining and scanning electron microscopy (SEM). Both species exhibited gill structures typical of teleosts, with primary and secondary lamellae essential for efficient gas exchange. In A. furcatus, gills displayed variations linked to size and gender, with numerous secondary lamellae and a variety of epithelial cells, including squamous, chloride, mucus, blood, and pillar cells. Air exposure led to interlamellar cell masses (ILCM) growth, reducing the lamellae surface area. In A. hormuzensis, gill arches featured a double row of primary filaments with secondary lamellae facilitating oxygen exchange, supported by pillar cells and dense distribution of mucous cells throughout the epithelium. The study highlights the adaptive mechanisms of A. furcatus in response to fluctuating environmental conditions and underscores the evolutionary conservation of gill morphology among teleosts. These findings provide crucial insights into respiratory efficiency and ecological adaptability, emphasizing eco‐evolutionary acclimation to extreme aquatic habitats.

Unveiling the ecological dominance of button mangrove (Conocarpus erectus L.) through microstructural and functional traits modifications across heterogenic environmental conditions

BackgroundThe button mangrove (Conocarpus erectus L.) is regarded as a peripheral species within mangrove communities. This particular species has the ability to thrive in regions that are arid or semiarid, where there is limited availability of nutrients. This study provides evidence of the ecological dominance of Conocarpus erectus across various habitats, highlighting its adaptability and success throughout the country of Pakistan. We collected twelve populations from four distinct ecological regions, including artificial forest plantations, agricultural fields, roadsides, and wastelands, offering a comprehensive assessment of C. erectus adaptability across diverse environmental contexts.ResultsForest plantation populations exhibited impressive shoot growth and moderate root lengths, with plants generally tall and well-weighted. Physiologically, they had moderate chlorophyll content and low carotenoid levels, with a balanced chlorophyll a/b ratio, indicating stable photosynthetic activity. Anatomically, these populations had thicker epidermal and cortical root layers but smaller vascular bundles and phloem regions. Stem and leaf structures were generally moderate in size, with thicker midribs and cortical layers in the leaves. Agricultural field populations showed robust shoot and root systems with balanced fresh and dry biomass. They exhibited high chlorophyll and carotenoid levels, indicating strong photosynthetic capacity. Root and stem anatomy revealed larger root areas, thicker cortex, and wide vascular bundles, reflecting enhanced structural development. Leaves from these populations had moderate midrib and cortical thickness, with larger stomatal areas, promoting efficient gas exchange. Roadside populations displayed deeper roots and reduced biomass production. These populations adapted to environmental stress through leaf expansion, with high leaf numbers and areas. Physiologically, populations had high chlorophyll content, with a high chlorophyll a/b ratio. Root and stem anatomy showed compact structures with smaller vascular bundles, indicating adaptation to harsher conditions. Leaf anatomy was moderate, with smaller vascular bundles and reduced water transport capacity. Wasteland populations exhibited poor growth and high shoot biomass despite small leaves. Physiologically, these populations had the highest total soluble protein and proline contents, reflecting stress adaptation. Anatomically, root and stem structures were variable, with some populations showing reduced cortical cell areas and smaller vascular bundles, indicating limited resource transport. Leaf structures had thicker lamina, thinner epidermal layers, and lower stomatal densities, reflecting adaptation to nutrient-poor soils.ConclusionThis study reveals the adaptability and thriving potential of Conocarpus erectus across varied habitats, providing key insights into its resilience and survival strategies. Understanding these adaptive traits can support habitat restoration, conservation planning, and improve species management in diverse environmental conditions, especially in response to climate change and habitat degradation.

Fractal Geometry in Vertebrate Respiratory Systems: A Comparative Analysis of Branching Patterns Across Species

This study investigates the application of fractal geometry to the analysis of vertebrate respiratory systems, focusing on the branching patterns of the bronchial tree across diverse species. Using a combination of mathematical modeling and computational visualization, we explore how fractal dimensions and branching characteristics reflect evolutionary adaptations to various habitats and physiological demands. The research encompasses a range of vertebrates, including humans, horses, dolphins, chickens, iguanas, and bullfrogs, representing diverse taxonomic groups and ecological niches. Our analysis reveals a clear gradient of complexity in respiratory structures, correlating strongly with metabolic rates and environmental adaptations. Mammals, particularly those adapted for high‐performance activities like horses, demonstrate the most complex fractal patterns, indicating highly efficient gas exchange systems. In contrast, ectothermic species such as iguanas and bullfrogs exhibit simpler structures, reflecting their lower metabolic demands and alternative respiratory strategies. The study employs fractal dimension calculations, L‐system modeling, and lacunarity analysis to quantify and visualize these differences. Our findings suggest that fractal analysis provides valuable insights into the relationship between form and function in vertebrate respiratory systems, offering a novel perspective on comparative physiology and evolutionary biology. This research not only enhances our understanding of respiratory system evolution but also has potential applications in biomimetic design, medical diagnostics, and ecological physiology. It demonstrates the power of interdisciplinary approaches, combining advanced mathematics with biological principles to uncover fundamental patterns in nature.

Advancing extracorporeal carbon dioxide removal technology: bridging basic science and clinical practice.

Recently, advancements in extracorporeal carbon dioxide removal (ECCO2R) technology have markedly enhanced its clinical applicability and efficacy for managing severe respiratory conditions. This review highlights critical innovations in ECCO2R, such as advanced catheter technologies, active mixing methods, and biochemical enhancements, which have substantially improved gas exchange efficiency and broadened the scope of ECCO2R applications. Integrating ECCO2R into acute and chronic respiratory care has led to a shift toward more mobile and less invasive modalities, promising for extending ECCO2R usage from intensive care units to home settings. By examining these technological advancements and their clinical impacts, this paper outlines the potential future directions of ECCO2R technology, emphasizing its role in transforming respiratory care practices and enhancing patient outcomes.

Gas exchange efficiency slopes to assess exercise tolerance in chronic obstructive pulmonary disease

BackgroundIn patients with chronic obstructive pulmonary disease (COPD), the clinical use of the minute ventilation-carbon dioxide production (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}CO2) slope has been reported as a measure of exercise efficiency, but the oxygen uptake efficiency slope (OUES), i.e., the slope of oxygen uptake (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}O2) versus the logarithmically transformed \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E, has rarely been reported.MethodsWe hypothesized that the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}CO2 slope is more useful than OUES in clinical use for the pathophysiological evaluation of COPD. Then, we investigated the cardiopulmonary exercise testing parameters affecting each of these slopes in 122 patients with all Global Initiative for Chronic Obstructive Lung Disease (GOLD) COPD grades selected from our database.ResultsCompared with the GOLD I-II group (n = 51), peak \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}O2 (p < 0.0001), OUES (p = 0.0161), \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E at peak exercise (p < 0.0001), and percutaneous oxygen saturation (SpO2) at peak exercise (p = 0.0004) were significantly lower in the GOLD III-IV group (n = 71). The GOLD III-IV group was divided into two groups by the exertional decrease in SpO2 from rest to peak exercise: 3% or less (the non-desaturation group: n = 23), or greater than 3% (the desaturation group: n = 48). OUES correlated only weakly with peak \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}O2, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E at peak exercise, and the difference between inspired and expired mean O2 concentrations (ΔFO2) at peak exercise, i.e., an indicator of oxygen consumption ability throughout the body, in the GOLD III-IV group with exertional hypoxemia. In contrast, the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}CO2 slope was significantly correlated with ΔFO2 at peak exercise, regardless of the COPD grade and exertional desaturation. Across all COPD stages, there was no correlation between the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}CO2 slope and \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E at peak exercise, and stepwise analysis identified peak \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}O2 (p = 0.0345) and ΔFO2 (p < 0.0001) as variables with a greater effect on the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}CO2 slope.ConclusionsThe OUES may be less useful in advanced COPD with exertional hypoxemia. The \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}CO2 slope, which is independent of \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E, focuses on oxygen consumption ability and exercise tolerance in COPD, regardless of the exertional hypoxemia level and COPD grade. Therefore, the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}CO2 slope might be useful in establishing or evaluating tailor-made therapies for individual patient’s pathologies in COPD as an indicator focusing on oxygen consumption ability.

Efficient Computation of Radiative Heat Recovery from Porous Ceramic Monoliths for Efficient Solar Thermochemical Fuel Production

Solar thermochemical hydrogen (STCH) produced by heat-driven water-splitting is a promising route for producing green hydrogen and other zero-emission synfuels. However, the efficiency of STCH must be dramatically increased for it to make an impact on decarbonization efforts. We have previously presented a novel Reactor Train System (RTS) for significantly increasing the efficiency of STCH by employing heat recovery from the redox material and efficient gas exchange processes. In this paper we present a higher-fidelity model for the RTS that accommodates the slow heat diffusion through the STCH redox material. For this purpose, a novel method is introduced for transient modelling of radiative heat in participating media. This method, called GREENER: Generalized Radiation Exchange Factors and Net Radiation, combines the accuracy of Monte Carlo Ray Tracing with the low computational cost of the P1 or Rosseland diffusion approximations. Along with STCH, GREENER has application for modelling volumetric solar receivers, high temperature heat recovery systems like heat exchangers and regenerators, and packed bed reactors. Using the GREENER method, the RTS counterflow radiative heat exchanger is shown to achieve heat recovery effectiveness greater than 70%. The performance of non-uniform porous redox morphologies is evaluated, and high-performing configurations are identified.

Effects of sildenafil on gas exchange, ventilatory, and sensory responses to exercise in subjects with mild-to-moderate COPD: A randomized cross-over trial

Excess exercise ventilation (high ventilation (V̇E)/carbon dioxide output (V̇CO2)) contributes significantly to dyspnea and exercise intolerance since the earlier stages of chronic obstructive pulmonary disease (COPD). A selective pulmonary vasodilator (inhaled nitric oxide) has shown to increase exercise tolerance secondary to lower V̇E/V̇CO2 and dyspnea in this patient population. We aimed to assess whether a clinically more practical option - oral sildenafil - would be associated with similar beneficial effects. In a randomized, placebo-controlled study, twenty-four patients with mild-to-moderate COPD completed, on different days, two incremental cardiopulmonary exercise tests (CPET) one hour after sildenafil or placebo. Eleven healthy participants performed a CPET in a non-interventional visit for comparative purposes with patients when receiving placebo. Patients (FEV1= 69.4 ± 13.5 % predicted) showed higher ventilatory demands (V̇E/V̇CO2), worse pulmonary gas exchange, and higher dyspnea during exercise compared to controls (FEV1= 98.3 ±11.6 % predicted). Contrary to our expectations, however, sildenafil (50 mg; N= 15) did not change exertional V̇E/V̇CO2, dead space/tidal volume ratio, operating lung volumes, dyspnea, or exercise tolerance compared to placebo (P>0.05). Due to the lack of significant beneficial effects, nine additional patients were trialed with a higher dose (100 mg). Similarly, active intervention was not associated with positive physiological or sensory effects. In conclusion, acute oral sildenafil (50 or 100 mg) failed to improve gas exchange efficiency or excess exercise ventilation in patients with predominantly moderate COPD. The current study does not endorse a therapeutic role for sildenafil to mitigate exertional dyspnea in this specific patient subpopulation.Clinical trial registry: https://ensaiosclinicos.gov.br/rg/RBR-4qhkf4Web of Science Researcher ID: O-7665–2019

Dual role of BdMUTE during stomatal development in the model grass Brachypodium distachyon.

Grasses form morphologically derived, four-celled stomata, where two dumbbell-shaped guard cells (GCs) are flanked by two lateral subsidiary cells (SCs). This innovative form enables rapid opening and closing kinetics and efficient plant-atmosphere gas exchange. The mobile bHLH transcription factor MUTE is required for SC formation in grasses. Yet whether and how MUTE also regulates GC development and whether MUTE mobility is required for SC recruitment is unclear. Here, we transgenically impaired BdMUTE mobility from GC to SC precursors in the emerging model grass Brachypodium distachyon. Our data indicate that reduced BdMUTE mobility severely affected the spatiotemporal coordination of GC and SC development. Furthermore, although BdMUTE has a cell-autonomous role in GC division orientation, complete dumbbell morphogenesis of GCs required SC recruitment. Finally, leaf-level gas exchange measurements showed that dosage-dependent complementation of the four-celled grass morphology was mirrored in a gradual physiological complementation of stomatal kinetics. Together, our work revealed a dual role of grass MUTE in regulating GC division orientation and SC recruitment, which in turn is required for GC morphogenesis and the rapid kinetics of grass stomata.

Control of hyperpnoea and pulmonary gas exchange during prolonged exercise: The role of group III/IV muscle afferent feedback.

It remains unclear whether feedback from group III/IV muscle afferents is of continuous significance for regulating the pulmonary response during prolonged (>5min), steady-state exercise. To elucidate the influence of these sensory neurons on hyperpnoea, gas exchange efficiency, arterial oxygenation and acid-base balance during prolonged locomotor exercise, 13healthy participants (4 females; 21 (3) years, : 46 (8) ml/kg/min) performed consecutive constant-load cycling bouts at ∼50% (20min), ∼75% (20min) and ∼100% (5min) of with intact (CTRL) and pharmacologically attenuated (lumbar intrathecal fentanyl; FENT) group III/IV muscle afferent feedback from the legs. Pulmonary responses were continuously recorded and arterial blood (radial catheter) periodically collected throughout the exercise. Pulmonary gas exchange efficiency was evaluated using the alveolar-arterial difference ( ). There were no differences in any of the variables of interest between conditions before the start of the exercise. Pulmonary ventilation was up to 20% lower across all intensities during FENT compared to CTRL exercise (P<0.001) and this hypoventilation was accompanied by an up to 10% lower arterial and a 2-4mmHg higher (both P<0.001). The exercise-induced widening of was up to 25% larger during FENT compared to CTRL (P<0.001). Importantly, the differences developed within the first minute of each stage and persisted, or further increased, throughout the remainder of each bout. These findings reflect a critical and time-independent significance of feedback from group III/IV leg muscle afferents for continuously regulating the ventilatory response, gas exchange efficiency, arterial oxygenation and acid-base balance during human locomotion. KEY POINTS: Feedback from group III/IV leg muscle afferents reflexly contributes to hyperpnoea during short duration (i.e. <5min) locomotor exercise. Whether continuous feedback from these sensory neurons is obligatory to ensure adequate pulmonary responses during steady-state exercise of longer duration remains unknown. Lumbar intrathecal fentanyl was used to attenuate the central projection of group III/IV leg muscle afferents during prolonged locomotor exercise (i.e. 45min) at intensities ranging from 50% to 100% of . Without affecting the metabolic rate, afferent blockade compromised pulmonary ventilation and gas exchange efficiency, consistently impairing arterial oxygenation and facilitating respiratory acidosis throughout exercise. These findings reflect the time-independent significance of feedback from group III/IV muscle afferents for regulating exercise hyperpnoea and gas exchange efficiency, and thus for optimizing arterial oxygenation and acid-base balance, during prolonged human locomotion.

Aging-Associated Molecular Changes in Human Alveolar Type I Cells.

Human alveolar type I (AT1) cells are specialized epithelial cells that line the alveoli in the lungs where gas exchange occurs. The primary function of AT1 cells is not only to facilitate efficient gas exchange between the air and the blood in the lungs, but also to contribute to the structural integrity of the alveoli to maintain lung function and homeostasis. Aging has notable effects on the structure, function, and regenerative capacity of human AT1 cells. However, our understanding of the molecular mechanisms driving these age-related changes in AT1 cells remains limited. Leveraging a recent single-cell transcriptomics dataset we generated on healthy human lungs, we identified a series of significant molecular alterations in AT1 cells from aged lungs. Notably, the aged AT1 cells exhibited increased cellular senescence and chemokine gene expression, alongside diminished epithelial features such as decreases in cell junctions, endocytosis, and pulmonary matrisome gene expression. Gene set analyses also indicated that aged AT1 cells were resistant to apoptosis, a crucial mechanism for turnover and renewal of AT1 cells, thereby ensuring alveolar integrity and function. Further research on these alterations is imperative to fully elucidate the impact on AT1 cells and is indispensable for developing effective therapies to preserve lung function and promote healthy aging.

Effect of CO2 Elevation on Tomato Gas Exchange, Root Morphology and Water Use Efficiency under Two N-Fertigation Levels.

Atmospheric elevated CO2 concentration (e[CO2]) decreases plant nitrogen (N) concentration while increasing water use efficiency (WUE), fertigation increases crop nutrition and WUE in crop; yet the interactive effects of e[CO2] coupled with two N-fertigation levels during deficit irrigation on plant gas exchange, root morphology and WUE remain largely elusive. The objective of this study was to explore the physiological and growth responses of ambient [CO2] (a[CO2], 400 ppm) and e[CO2] (800 ppm) tomato plant exposed to two N-fertigation regimes: (1) full irrigation during N-fertigation (FIN); (2) deficit irrigation during N-fertigation (DIN) under two N fertilizer levels (reduced N (N1, 0.5 g pot-1) and adequate N (N2, 1.0 g pot-1). The results indicated that e[CO2] associated with DIN regime induced the lower N2 plant water use (7.28 L plant-1), maintained leaf water potential (-5.07 MPa) and hydraulic conductivity (0.49 mol m-2 s-1 MPa-1), greater tomato growth in terms of leaf area (7152.75 cm2), specific leaf area (223.61 cm2 g-1), stem and total dry matter (19.54 g and 55.48 g). Specific root length and specific root surface area were increased under N1 fertilization, and root tissue density was promoted in both e[CO2] and DIN environments. Moreover, a smaller and denser leaf stomata (4.96 µm2 and 5.37 mm-2) of N1 plant was obtained at e[CO2] integrated with DIN strategy. Meanwhile, this combination would simultaneously reduce stomatal conductance (0.13 mol m-2 s-1) and transpiration rate (1.91 mmol m-2 s-1), enhance leaf ABA concentration (133.05 ng g-1 FW), contributing to an improvement in WUE from stomatal to whole-plant scale under each N level, especially for applying N1 fertilization (125.95 µmol mol-1, 8.41 µmol mmol-1 and 7.15 g L-1). These findings provide valuable information to optimize water and nitrogen fertilizer management and improve plant water use efficiency, responding to the potential resource-limited and CO2-enriched scenario.

Oxidized Bacterial Cellulose Membranes Immobilized with Papain for Dressing Applications: Physicochemical and In Vitro Biological Properties.

This research consolidates our group's advances in developing a therapeutic dressing with innovative enzymatic debridement, focusing on the physicochemical and in vitro biological properties of papain immobilized in wet oxidized bacterial cellulose (OxBC-Papain) dressing. OxBC membranes were produced with Komagataeibacter hansenii oxidized with NaIO4, and papain was immobilized on them. They were characterized in terms of enzyme stability (over 100 days), absorption capacity, water vapor transmission (WVT), hemocompatibility, cytotoxicity, and cell adhesion. The OxBC-Papain membrane showed 68.5% proteolytic activity after 100 days, demonstrating the benefit of using the OxBC wet membrane for papain stability. It had a WVT rate of 678 g/m2·24 h and cell viability of 99% and 86% for L929 and HaCat cells, respectively. The membranes exhibited non-hemolytic behavior and maintained 26% clotting capacity after 1 h. The wet OxBC-Papain membrane shows significant potential as a natural biomolecule-based therapeutic dressing for wound care, offering efficient debridement, moisture maintenance, exudate absorption, gas exchange, and hemostasis without cytotoxic effects or cell adhesion to the dressing. Further research, especially using in vivo models, is needed to assess its efficacy in inducing epithelialization. This study advances stomatherapy knowledge, providing a cost-effective solution for enzymatic debridement in healthcare.

The influence of membrane fiber arrangement on gas exchange in blood oxygenators: A combined numerical and experimental analysis

Oxygenators take over lung function in the event of severe lung injuries by exchanging gas into the blood stream using hollow fiber membrane mats. A central limitation of oxygenators is their large foreign surface area and priming volume, which cause blood damage.Thus, gas exchange efficiency needs to be improved through an understanding of the interaction between fiber arrangement and blood flow directions. This has only been investigated in two dimensional or simplified non-realistic fiber bundles. The aim of this study was to quantify gas exchange in realistic 3D fiber bundles.We performed three dimensional micro scale CFD simulations of different realistic fiber arrangements and flow directions that we validated in corresponding test oxygenators using porcine blood.Fiber-configurations influence gas transfer by factor 2, with highest transfer rates for blood flowing in circumferential direction, and lowest for longitudinal direction in wound oxygenators. The CFD model correlates with the experiments with an R2 = 0.88.For the first time, the configuration of realistic 3D fiber bundles was proven to strongly influence gas transfer in oxygenators, in simulations and experiments. The CFD model serves for investigation of further configurations and to derive transfer coefficients for full scale oxygenators.

Decoding stomatal characteristics regulating water use efficiency at leaf and plant scales in rice genotypes.

Stomatal traits in rice genotypes affect water use efficiency. Low-frequency small-size stomata correlate with whole plant efficiency, while low-frequency large-size stomata show intrinsic efficiency and responsiveness to vapour pressure deficit. Leaf surface and the patterning of the epidermal layer play a vital role in determining plant growth. While the surface helps in determining radiation interception, epidermal pattern of stomatal factors strongly regulate gas exchange and water use efficiency (WUE). This study focuses on identifying distinct stomatal traits among rice genotypes to comprehend their influence on WUE. Stomatal frequency ranged from 353 to 687 per mm2 and the size varied between 128.31 and 339.01 μm2 among 150 rice germplasm with significant variability in abaxial and adaxial surfaces. The cumulative water transpired and WUE determined at the outdoor phenomics platform, over the entire crop growth period as well as during specific hours of a 24h-day did not correlate with stomatal frequency nor size. However, genotypes with low-frequency and large-size stomata recorded higher intrinsic water use efficiency (67.04μmol CO2 mol-1 H2O) and showed a quicker response to varying vapour pressure deficit that diurnally ranged between 0.03 and 2.17kPa. The study demonstrated the role of stomatal factors in determining physiological subcomponents of WUE both at single leaf and whole plant levels. Differential expression patterns of stomatal regulatory genes among the contrasting groups explained variations in the epidermal patterning. Increased expression of ERECTA, TMM and YODA genes appear to contribute to decreased stomatal frequency in low stomatal frequency genotypes. These findings underscore the significance of stomatal traits in breeding programs and strongly support the importance of these genes that govern variability in stomatal architecture in future crop improvement programs.

Effect of artificial lung fiber bundle geometric design on micro- and macro-scale clot formation.

The hollow fiber membrane bundle is the functional component of artificial lungs, transferring oxygen to and carbon dioxide from the blood. It is also the primary location of blood clot formation and propagation in these devices. The geometric design of fiber bundles is defined by a narrow set of parameters that determine gas exchange efficiency and blood flow resistance, principally: fiber packing density, path length, and frontal area. These same parameters also affect thrombosis. This study investigated the effect of these parameters on clot formation using 3D printed flow chambers that mimic the geometry and blood flow patterns of fiber bundles. Hollow fibers were represented by an array of vertical micro-rods (380 μm diameter) arranged with three packing densities (40%, 50%, and 60%) and two path lengths (2 and 4 cm). Blood was pumped through these devices corresponding to three mean blood flow velocities (16, 20, and 25 cm/min). Results showed that (1) clot formation decreases dramatically with decreasing packing density and increasing blood flow velocity, (2) clot formation at the outlet of the fiber bundle enhances deposition upstream, and consequently (3) greater path length provides greater clot-free fiber surface area for gas exchange than a shorter path length. These results can help guide the design of less thrombogenic, more efficient artificial lung designs.

The Lungs in Space: A Review of Current Knowledge and Methodologies.

Space travel presents multiple risks to astronauts such as launch, radiation, spacewalks or extravehicular activities, and microgravity. The lungs are composed of a combination of air, blood, and tissue, making it a complex organ system with interactions between the external and internal environment. Gravity strongly influences the structure of the lung which results in heterogeneity of ventilation and perfusion that becomes uniform in microgravity as shown during parabolic flights, Spacelab, and Skylab experiments. While changes in lung volumes occur in microgravity, efficient gas exchange remains and the lungs perform as they would on Earth; however, little is known about the cellular response to microgravity. In addition to spaceflight and real microgravity, devices, such as clinostats and random positioning machines, are used to simulate microgravity to study cellular responses on the ground. Differential expression of cell adhesion and extracellular matrix molecules has been found in real and simulated microgravity. Immune dysregulation is a known consequence of space travel that includes changes in immune cell morphology, function, and number, which increases susceptibility to infections. However, the majority of in vitro studies do not have a specific respiratory focus. These studies are needed to fully understand the impact of microgravity on the function of the respiratory system in different conditions.

Experimental investigation of the matching boundary and optimization strategy of a variable geometry turbocharged direct-injected hydrogen engine

With the higher demand for torque, power, brake thermal efficiency (BTE), and low NOx emissions of hydrogen engines, direct injection and turbocharging are the most effective methods to improve performance. However, due to the large air flow rate variation range with lean combustion and low exhaust gas energy, the turbine needs to be adjusted significantly, and the performance of the conventional waste gate turbochargers is limited. In this study, a 2.0 L direct-injected turbocharged hydrogen engine was studied experimentally and matched with a variable geometry turbocharger (VGT). The working boundary of the VGT determined by abnormal combustion and exhaust back pressure is proposed at all working conditions as it changes from 10-50 % @1500 rpm to 40–75 % @4500 rpm. Control of the VGT to balance combustion and gas exchange was achieved to reach the highest BTE of 42.57 %. Further, high torque of 326 Nm and high power of 125 kW are explored and different VGT opening strategies are compared. An optimized VGT opening control strategy is proposed, which is divided into five regions at different loads to ensure best performance. The VGT opening control strategy based on λ control and the trade-off between combustion and gas exchange efficiency at all working conditions can be valuable in the development of high-performance hydrogen engines.

Enhancing plant resilience: arbuscular mycorrhizal fungi's role in alleviating drought stress in vegetation concrete.

Drought stress usually inhibits plant growth, which may increase the difficulty of greening slopes. In this study, we systematically investigated the effects of arbuscular mycorrhizal (AM) fungi on the growth and drought tolerance of two plant species, Festuca elata and Cassia glauca, in a vegetation concrete environment by exogenously inoculating AM fungi and setting three drought levels: well water, moderate drought and severe drought. The results showed that plant growth was significantly inhibited under drought stress; however, AM fungi inoculation significantly promoted plant height, root length, and above- and belowground biomass in these two plant species. Compared with, those in the CK treatment, the greatest increases in the net photosynthesis rate, stomatal conductance and transpiration rate in the AM treatment group were 36.72%, 210.08%, and 66.41%, respectively. Moreover, inoculation with AM fungi increased plant superoxide dismutase and catalase activities by 4.70-150.73% and 9.10-95.70%, respectively, and reduced leaf malondialdehyde content by 2.79-55.01%, which alleviated the damage caused by oxidative stress. These effects alleviated the damage caused by oxidative stress and increased the content of soluble sugars and soluble proteins in plant leaves by 1.52-65.44% and 4.67-97.54%, respectively, which further increased the drought adaptability of plants. However, inoculation with AM fungi had different effects on different plants. In summary, this study demonstrated that the inoculation of AM fungi in vegetation concrete environments can significantly increase plant growth and drought tolerance. The plants that formed a symbiotic structure with AM fungi had a larger root uptake area, greater water uptake capacity, and greater photosynthesis and gas exchange efficiency. In addition, AM fungi inoculation further increased the drought adaptability of the plants by increasing their antioxidant enzyme activity and regulating their metabolite content. These findings are highly important for promoting plant growth and increasing drought tolerance under drought conditions, especially for potential practical applications in areas such as slope protection, and provide useful references for future ecological engineering and sustainable development.

Subpopulations of fibroblasts derived from human iPS cells

Organ fibrosis causes collagen fiber overgrowth and impairs organ function. Cardiac fibrosis after myocardial infarction impairs cardiac function significantly, pulmonary fibrosis reduces gas exchange efficiency, and liver fibrosis disturbs the natural function of the liver. Its development is associated with the differentiation of fibroblasts into myofibroblasts and increased collagen synthesis. Fibrosis has organ specificity, defined by the heterogeneity of fibroblasts. Although this heterogeneity is established during embryonic development, it has not been defined yet. Fibroblastic differentiation of induced pluripotent stem cells (iPSCs) recapitulates the process by which fibroblasts acquire diversity. Here, we differentiated iPSCs into cardiac, hepatic, and dermal fibroblasts and analyzed their properties using single-cell RNA sequencing. We observed characteristic subpopulations with different ratios in each organ-type fibroblast group, which contained both resting and distinct ACTA2+ myofibroblasts. These findings provide crucial information on the ontogeny-based heterogeneity of fibroblasts, leading to the development of therapeutic strategies to control fibrosis.

Effect of continuous positive airway pressure helmet on respiratory function following surgical procedures in brachycephalic dogs: A randomized controlled trial.

To evaluate the effect of continuous positive airway pressure (CPAP) on respiratory function in the early postoperative period of brachycephalic dogs. Prospective, randomized clinical trial. A total of 32 dogs. Dogs were assigned to recover with or without CPAP (control) and assessed at specific time points over 1 h. Treatment was discontinued for dogs with a CPAP tolerance score of 3 or more (from a range of 0-4). The primary outcome was pulse oximetry (SpO2). Secondary outcomes were arterial O2 pressure (PaO2)/FiO2 ratio (PaO2/FiO2), arterial CO2 pressure (PaCO2), and rectal temperature. For dogs that reached a CPAP tolerance score of 3 or more, only the data collected up to the time point before discontinuation were included in the analysis.The treatment effect (β) was analyzed using random effects models and the results were reported with 95% confidence intervals. Dogs were assigned randomly to each protocol. Baseline characteristics in both groups were comparable. Arterial blood gases were obtained in seven control group dogs and nine CPAP group dogs. Treatment did not affect SpO2 (β = -0.1, -2.1 to 2.0) but affected the PaO2/FiO2 ratio (β = 58.1, 2.6 to 113.6), with no effects on PaCO2 (β = -4.3, -10.5 to 1.9) or temperature (β = 0.4, -0.8 to 1.6). In postoperative brachycephalic dogs, CPAP had no effect on SpO2 but improved the PaO2/FiO2 ratio in brachycephalic dogs postoperatively. Continuous positive airway pressure offers a valuable solution to improve gas exchange efficiency, a prevalent concern in postoperative brachycephalic dogs, with the potential to enhance overall outcomes.