bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxidative Enzyme Activity in Respiratory and Non‐Respiratory Muscle of Hypoxic Mice and Human Respiratory Patients
Authors: O'Connor Karen M. , Lewis Philip , O'Leary Andrew J. , Burns David P. , NiHici Tamara , Mayooran Nithiananthan , Hinchion John , O'Halloran Ken D. 
Published: November 2023

Despite the clinical relevance, little is known about the effects of long‐term exposure to hypoxia on respiratory muscle form and function. Recently, we demonstrated that exposure to chronic sustained hypoxia (CSH) causes respiratory muscle weakness due to oxidative stress (1). Redox proteomics with mass spectrometry revealed widespread oxidation of enzymes including those of the mitochondrial respiratory chain (1). We sought to explore citrate synthase activity in muscle samples from normoxic and CSH exposed mice. We have also initiated a study in human respiratory patients to explore the relationship between hypoxaemia and muscle aerobic capacity.C57BL6/J mice were exposed to normoxia or CSH (FiO2 = 10%) with/without antioxidant supplementation (either 1% N‐acetyl cysteine (NAC) or 1mM Tempol) for a period of six weeks (n=4–8 per group). Animals were anaesthetized with 5% isoflurane and euthanized. The diaphragm, soleus, extensor digitorum longus and tibialis anterior were excised. Following approval, external intercostal (n=10) and latissimus dorsi (n=9) muscle samples were harvested from respiratory patients under‐going thoracic surgery in Cork University Hospital. Patients presented with a wide range of pre‐operative blood oxygenation (PaO2) values breathing room air, including COPD patients. Homogenisation was performed on muscle samples, followed by protein quantification using a bicinchoninic assay (BCA). Citrate synthase activity was measured spectrophotometrically, as an index of oxidative enzyme activity (aerobic capacity), using commercial kits.Values are reported as mean±SEM. In mouse, diaphragm and limb muscles showed differential responses to hypoxia. Antioxidant supplementation with either NAC or Tempol prevented the hypoxia‐induced reduction in mouse diaphragm citrate synthase activity (P<0.0001). In human muscle, there was a significantly higher citrate synthase activity (P=0.018) in external intercostal compared with latissimus dorsi. Our pilot study examining citrate synthase activity as a function of PaO2 in respiratory patients is suggestive of a positive correlation, revealing low enzyme activity in two hypoxaemic patients (PaO2 < 60mmHg).The working respiratory muscles are particularly susceptible to hypoxia‐induced reduction in citrate synthase activity. Recent work from our group has revealed considerable redox remodelling and metabolic reprogramming in respiratory muscle following CSH exposure (1). Preliminary data from human external intercostal muscle suggest a similar outcome to mouse studies. Antioxidants may have application as an adjunctive therapy in respiratory diseases characterised by hypoxia.Support or Funding InformationThe Physiological Society
Pulmonary Collagen Content in 1‐Year‐Old Rats Exposed to Postnatal Hyperoxia
Authors: Sobotik Atzie , Pegelow David , Goss Kara , Haraldsdottir Kristin , Braun Rudolf , Barton Greg , Tetri Laura , Eldridge Marlowe 
Published: November 2023

IntroductionBronchopulmonary dysplasia (BPD) is a chronic lung disease of preterm infants exposed to oxygen therapy postnatally. Although it is a vital, life‐saving treatment, oxygen therapy is closely associated with long‐term consequences, including decreased alveolarization and reductions in pulmonary vasculature cross‐sectional area. Previous studies using a BPD rodent model have demonstrated an increase in lung collagen content within the first 20 days of birth. This suggests that the aberrant lung development in the BPD animal model is associated with pathological changes in the extracellular matrix (ECM) (i.e. increased collagen content). No study to our knowledge has looked at collagen accumulation later in life as a result of early postnatal hyperoxia treatment. Furthermore, it is currently unknown whether or not there are sex differences in the ECM remodeling. The purpose of this study is to determine if 14 days of postnatal hyperoxia exposure affects collagen accumulation in the lungs of 1‐year‐old male and female rats.MethodsAn established rat model of BPD using Sprague‐Dawley rats was. Within 12 hours of birth, rats were placed in a hyperoxic (HYP, 85% O2) chamber, or normoxic (NORM, 21% O2) chamber. After 14 days in respective conditions, all rats were allowed to age until 1 year in room air. The aged rats were sacrificed, and tissues were harvested and flash‐frozen in liquid nitrogen. Colorimetric assays were performed on lung tissue to assess overall hydroxyproline content as a measurement of collagen. Histology was also analyzed to visually assess collagen levels using Masson's trichrome‐stained lung slides. Four pictures were taken per slide, each picture was divided into 9 sections, and a blinded party scored each segment's collagen content on a scale of 1–3 (0=none, 1=mild, 2=moderate, 3=severe). Two‐way ANOVAs were used to determine the effects of sex, HYP exposure, and their influence on lung collagen.ResultsThe colorimetric assay revealed that aged hyperoxic females (n=7) demonstrate a 23% increase in collagen content compared to aged normoxic females (n=5, p=0.02). Aged HYP males (n=6) demonstrated similar pulmonary collagen content compared to aged normoxic males (n=3) based on colorimetric assay. However, histopathologic examination revealed increased collagen deposition in both males and female aged HYP rats (p=0.07, n=2–3).ConclusionsThese results suggest that females exposed to HYP in early‐postnatal life are more susceptible to collagen accumulation in the lungs, which may be indicative of increased lung injury as compared to males.Support or Funding InformationNIH‐NHLBI R01 – HL115061NIH‐NHLBI R01 Supplement – HL1150613
Predictors of Mortality Following Systemic LPS Injections During a Critical Period of Neonatal Development
Authors: Mayer Catherine A. , Desai Vilok , MacFarlane Peter M 
Published: November 2023

We showed previously the presence of a developmental window (postnatal age 10 days, P10) during which the respiratory neural control system exhibits a heightened vulnerability to a systemic injection of LPS. The vulnerability is associated with an attenuated hypoxic ventilatory response (HVR) and an unexpected high degree of mortality (~50% of rat pups) and is unique to the P10 age group because neither younger (P5) nor older (P20) rats appeared to be affected by LPS. Since only about half of the P10 rats appear to be vulnerable to LPS, we investigated whether the mortality could be predicted by prior examination of: 1) the magnitude of their hypoxic ventilatory response (HVR); and 2) changes in serum cytokine levels. Rat pups received an intraperitoneal injection of LPS (0.1mg/kg) or saline at P10. Plethysmography was performed at 2hrs post injection to determine the magnitude of the HVR; a blood sample was also taken immediately after plethysmography (via facial vein puncture) in unanesthetized rats to determine changes in serum TNFα levels using an ELISA. Rats were returned to the mother and monitored closely throughout the following 8hr time period for signs and symptoms of imminent death (color change, labored breathing, lethargy). 42% of rats treated with LPS died between 4–7 hrs after LPS whereas the remaining 58% survived. However, in the rats that died, the HVR at 2 hrs after LPS was reduced (0.64 ± 0.07 ml/g/min) compared to both saline treated rats (1.14 ± 0.13 ml/g/min) and survivors of LPS (0.97 ± 0.13 ml/g/min). The attenuated HVR of rats that died from LPS was associated with elevated serum TNFα levels (884.1 ± 89.4pg/ml; p<0.05) compared to saline rats (not detectable) and animals that survived LPS. These data suggest a sub‐population of rats exhibit a heightened and lethal vulnerability to LPS exposure that can be predicted by the magnitude of their HVR and serum TNFa levels prior to death. The cause of the vulnerability remains unknown although we speculate it may involve an aberrant “inflammatory” response to an otherwise sub‐lethal exposure to the endotoxin, resulting in a fatal disturbance in the cardio‐respiratory control system.Support or Funding InformationDepartment of Pediatrics, Rainbow Babies and Children's Hospital, Case Western Reserve University
Effects of A2A and 5‐HT2A Antagonists on Hypoxic and Hypercapnic Ventilatory Response in Rats Exposed to Chronic Sustained Hypoxia
Authors: Moya Esteban A , Powell Frank L 
Published: November 2023

Different patterns and durations of hypoxic exposure cause different forms of plasticity in the neural control of ventilation (Pamenter & Powell, F1000Prime Rep, 5: 23, 2013). For example, acute intermittent hypoxia (AIH) causes long term facilitation (LTF) of ventilation and phrenic nerve activity, while chronic sustained hypoxia (CSH) causes ventilatory acclimatization to hypoxia (VAH). In both LTF and VAH, ventilation in normoxia is increased after the hypoxic stimulus is removed. Previous work has shown that 5HT2a serotonin receptor activation (Gq pathway) is necessary for LTF but not VAH. However, recent work (Nichols et al., J Appl Physiol, 112: 1678–1688, 2012) shows A2A adenosine receptor activation (Gs pathway) is also involved in LTF with more severe AIH (PaO2 = 25–30 Torr vs. 35–45 Torr). We hypothesized that the Gs pathway also contributes to VAH and tested this in adult male rats by blocking the Gs and Gq pathways before and after 7 days of CSH (PO2 = 80 Torr) and measuring ventilation and the hypoxic ventilatory response (HVR) with barometric pressure plethysmography. Consistent with previous work, Gq blockade with a 5HT2a antagonist (Ketanserin, 1 mg/Kg i.p.) caused no significant changes before or after CSH. Gs blockade with an A2A agonist antagonist (MSX‐3, 1mg/Kg i.p.) had no effect before CSH but after CSH it significantly increased ventilation in acute normoxia (1777±352 vs. 2396±268 ml/min*kg) and hypoxia (2063±195 vs. 2403±450 ml/min*kg). This contrasts with the effect of Gs blockade during severe AIH to significantly decrease LTF and does not support our hypothesis. However, further experiments are necessary to determine the effects of blocking Gs and Gq pathways during CSH.Support or Funding InformationNIH RO1 HL‐081823
Ventilatory and Neurochemical Effects of Microdialysis of the Ionotropic GABAA Receptor Agonist Muscimol into the Ventral Respiratory Column of Awake Goats
Authors: Langer Thomas M , Neumueller Suzanne , Burgraff Nicholas , Crumley Emma , Pan Lawrence , Hodges Matthew R , Forster Hubert V 
Published: November 2023

We have previously dialyzed atropine, a nonspecific muscarinic receptor blocker in the ventral respiratory column (VRC) of chronically cannulated awake goats and observed an increase (J. Appl Physiol. 114, 694–647, 2012) or no change (Respir Physiol 205: 7–15, 2014) in ventilation (VI) and breathing frequency (f). The unexpected effects on VI and f with attenuating excitatory muscarinic receptor activity may have been due to the local compensatory increase in the excitatory neuromodulators serotonin (5‐HT) and substance P (SP) measured in the effluent dialysate mock cerebrospinal fluid (mCSF). To determine if a similar mechanism of compensation accompanied increased inhibition in the VRC, we dialyzed DAMGO, a μ‐opioid receptor agonist and found unexpectedly that absolute VI and f did not change (unpublished data). Analyses of effluent mCSF dialysate showed no changes in local 5‐HT or SP, but instead showed a decrease in GABA. Thus, these findings suggested that perturbation of G‐protein coupled receptors to not uniformly elicit local compensatory changes in neurochemicals and/or VI. In the present study, we dialyzed the ionotropic GABAA receptor agonist muscimol (0.5, 1.0, and 10.0 mM) into the VRC of awake goats (n=6), hypothesizing that it would inhibit ventilation as previously shown by others. Dialysis of muscimol at all doses had no effect on VI or f (P<0.05), but during the hour following drug application VI and f were increased (P<0.05) at all doses of muscimol. Associated with these studies, we found no changes in local SP, 5‐HT, GABA or glycine for all doses of muscimol. However, in 3 of 6 goats there was an increase in the concentration of norepinephrine in the effluent dialysate in response to 10 mM muscimol. Norepinephrine remained unchanged during dialysis of the lower doses of muscimol and in all of our previous dialysis studies. The results of these and previous studies support the concept of interdependence among local neurochemicals, and furthermore suggest that the mechanism of compensation differs between attenuation of excitatory and inhibitory G‐protein coupled receptors and between perturbation of G‐protein and ionotropic inhibitory receptors.Support or Funding InformationNational Heart, Lung, and Blood Institute Grants HL‐112996, HL‐007852, and the Department of Veterans Affairs
Combined effects of intermittent hyperoxia and intermittent hypoxia on respiratory control development in rats
Authors: MacDonald Carolyn A , O'Toole Caitlin A , Butler Jesse A , McDonough Amy B , Bavis Ryan W 
Published: November 2023

Preterm infants may experience hyperoxia due to early exposure to atmospheric O2 levels (relative hyperoxia) or through administration of supplemental O2. Although intermittent hyperoxia has been found to alter breathing in neonatal rats, hyperoxia alternates with bouts of hypoxia clinically. In this study, we exposed newborn rats for 14 days to four treatments: control (room air), sustained hyperoxia (30% O2; SH), intermittent hypercarbic hypoxia (10% O2/6% CO2, 5 episodes h−1; I10/30), or intermittent hyperoxia + hypercarbic hypoxia (10% O2/6% CO2 to 40% O2/0% CO2, 5 episodes h−1; I10/40); 30% O2 was used as the background O2 level for I10/30 and I10/40 to mimic the relative hyperoxia of preterm birth. SH and I10/40 rats had reduced carotid body responses to hypoxia, but only SH rats exhibited blunted ventilatory responses to hypoxia. CNS plasticity may compensate for abnormal carotid body function in I10/40 rats, or SH could alter breathing through additional mechanisms. In either case, intermittent hypercarbic hypoxia appears to diminish the effects of intermittent hyperoxia on the respiratory phenotype.Support or Funding InformationSupported by NIH grants HL114001 and GM103423.
Effect of Omega‐3 Polyunsaturated Fatty Acids on Insulin Resistance are Sex‐dependent: A Meta‐analysis of Randomized Controlled Trials
Authors: Garg Manohar Lal , Abbott Kylie , Thota Rohith , Acharya Shamsunder , Burrows Tracy Lal 
Published: November 2023

Interventions that improve Insulin Resistance (IR) may be able to prevent or delay the onset of type 2 diabetes in at‐risk populations. Cohort and cross‐sectional studies suggest there is an inverse relationship between omega‐3 polyunsaturated fatty acids (n3PUFAs) and IR, however randomised control trials (RCTs) have had equivocal findings. Recent findings by our research group suggest that effects may be sex‐dependent. The aim of this systematic review and meta‐analysis is to determine whether the results of RCTs differ according to sex.Five databases were searched (Medline, EMBASE, PubMed, CINAHL and Scopus) to locate RCTs that included a dietary or supplement‐based n3PUFA intervention and measures of IR in adult populations. Studies reporting HOMA‐IR were pooled for meta‐analysis. Sub‐group analysis was conducted to explore sex‐dependent differences.Thirty‐two trials were included in the systematic review, including a total of 2326 participants (mean age 53.4 years; BMI 29.7). Of those included, five were conducted in males only, seven in females, and the remaining included both sexes (n=20). Sixteen trials were pooled for meta‐analysis (males n=2; females n=4; combined n=10). There was considerable heterogeneity in terms of trial duration (mean 12.8 weeks; range 3–48 weeks), n3PUFA dose and placebos used. When all studies were pooled they showed no significant effect of n3PUFA on HOMA‐IR, with mean difference of intervention vs control (95%CI): −0.23 (−0.382, 0.337) (p=0.902). Subgroup analysis showed n3PUFA intervention significantly improved HOMA‐IR in females: −0.559 (−9.989, −0.130) (p=0.011), but had a non‐significant trend towards deterioration of HOMA‐IR in males: 1.382 (−0.183, 2.947) (p=0.083). No trials conducted in males found a positive effect of n3PUFA supplementation on insulin resistance.Findings from this systematic review and meta‐analysis support a sex‐dependent effect of n3PUFA intervention on markers of IR, with a protective effect evident in females only. n3PUFA interventions could potentially prevent the development of type 2 diabetes in females. Further research is required to further elucidate potential mechanisms of these sex‐dependent differences.Support or Funding Informationn/a
Mathematical modeling of the microenvironment beneath a surface pH electrode tip
Authors: Occhipinti Rossana , Calvetti Daniela , Boron Walter F , Somersalo Erkki 
Published: November 2023

The time course of extracellular surface pH (pHS), recorded by a blunt pH microelectrode, is the key physiological data to assess membrane permeability to CO2 (PM,CO2) when exposing an oocyte to a solution containing CO2/HCO3−. In an effort to extract PM,CO2 values from pHS measurements, we previously developed a reaction‐diffusion mathematical model of CO2 influx into a spherical cell. The model accounts for the slow interconversion of CO2 and HCO3− as well as the reactions of a multitude of non‐CO2/HCO3− buffers. When compared to physiological experiments, the model can predict the essential features of the measured pHS transients. However, it is clear that further improvements in the quantitative agreement of the model with the physiological data, will require additional refinements of the model, including a detailed modeling of the micro‐environment under the pHS electrode tip, when pushed against the cell membrane.In the present study, we propose two computational models for studying the effect of the pHS electrode on pHS measurements. In the first approach, we develop a two‐dimensional model of the pHS electrode and the extracellular microenvironment underneath the electrode by assuming that the electrode‐membrane interface is an infinitely thin homogenous disc within which diffusion occurs only in the tangential direction along the disc surface as well as at the interface between the disc and the bulk extracellular fluid. In addition, transmembrane gas exchange occurs between the disc and the cytoplasm, in a direction perpendicular to the disc. Mathematically, this model is described by two‐dimensional reaction‐diffusion equations that are solved numerically by a combination of finite difference (FD) schemes and stiff solvers. Because this model does not reveal the dependence of the pHS transient on the distance of the pHS electrode from the cell membrane, in the second approach, we develop a three‐dimensional reaction‐diffusion model of the pHS electrode tip and of its surrounding environment, where the reaction‐diffusion equations are now solved by a combination of the finite element method (FEM) with stiff solvers.Our preliminary results corroborate the hypothesis that diffusion is slower in the micro‐environment under the electrode tip, resulting in substantially larger pHS transients than those on a free membrane surface. The work points towards the possibility of defining a reliable electrode gain function that corrects the effect of the electrode.Support or Funding InformationSupported by grants from NIH (U01‐GM111251, K01‐DK107787)
Three‐dimensional Microenvironment with Uniaxial Topology Induces Myoblast Maturation
Authors: Ko Ung Hyun , Park Suk‐Hee , Choung Jinseung , Lee Junho , Shin Jennifer 
Published: November 2023

IntroductionWith the recent advancement in micro‐manufacturing technology, there have been remarkable research progresses in utilization of synthetic scaffolds for tissue engineering applications. The synthetic scaffold exhibits high sustainability of sub‐micron structure, enabling researchers to mimic the micro‐environments of the in vivo tissues. However, the manufacturing resolution of the synthetic scaffold still needs improvements to provide truly the 3D environment for the cells by reflecting the dimensions and structural features the cellular extracellular matrix (ECM). On the other hand, hydrogels such as collagen, fibrin, or matrigel can provide 3D environment yet with weak mechanical strength and stability.Materials and MethodsIn this study, we incorporated collagen with the electrospun scaffold to realize the sub‐micron uniaxial pattern with 3D substrate environment. The synthetic scaffold was fabricated by electrospinning method using polycaprolactone (PCL) polymer, and the uniaxial topology was regulated by the tilted gap collectors. Mouse myoblasts (C2C12s) were expanded on electrospun scaffold and collagen gel was added on the scaffold after one day. C2C12 cells were cultured for 6 days in total and subsequently differentiated for 7 days in DMEM supplemented with 5% equine serum.Results and DiscussionWe found that our hybrid scaffold system effectively induced cellular elongation compared to ordinary uniaxial synthetic scaffolds and promoted myogenic differentiation. This elongation effect was initially induced by the uniaxial cue of synthetic backbone, and 3D environment additively increased cellular sustainability leading to higher elongation. These highly elongated cells were then induced to aggregate to form 3D myofibril whose maturation was further evoked by the application of electric field stimulation during the differentiation stage.ConclusionConclusively, we expect that the concept of our hybrid scaffold can be utilized in the field of skeletal muscle engineering and the underlying mechanism behind the role of physical cues in cellular physiology would have potential to be applied broadly in understanding the diseases and therapeutics in general.Support or Funding InformationAcknowledgements: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (2013R1A2A2A01017014).
Cross‐Linked Polypeptide Multilayer Films Facilitates the Cardiac Differentiation of Mouse iPSCs
Authors: Wang Si‐Han 
Published: November 2023

Well‐designed biomaterials, which mimic physiological microenvironment and mechanical properties, can guide stem cell differentiation. Polyelectrolyte multilayer films allow for modulation of thickness, stiffness, and adhesiveness and is a useful method for substrate coating to modulate cellular behaviors. In this study, mouse induced pluripotent stem cells (iPSCs) were cultured on polypeptide multilayer films built up by the alternate deposition of cationic poly‐L‐lysine and anionic poly‐L‐glutamic acid, cross‐linked with EDC/sulfo‐NHS, and coated with gelatin. The characteristics of film thickness, surface roughness, and adsorbed film mass were measured by AFM and QCM. Cardiomyocyte differentiation was evaluated by RT‐PCR analysis of cardiac markers, cardiac troponin T (cTnT) and myosin light chain‐2a (MLC‐2a). After embryonic bodies of iPSCs were cultured for 3 days and then induced for cardiac differentiation for 0, 3, and 6 days, compared with iPSCs on culture dish, iPSCs on 6‐layer cross‐linked polypeptide films demonstrates significantly higher expressions of both cTnT and MLC‐2a on day 3 and day 6. Our results indicate a possible way to facilitate iPSCs toward cardiomyocyte differentiation on polypeptide multilayer films.Support or Funding InformationThis work was supported by the Ministry of Science and Technology, Taiwan. (Grant number: NSC 102‐2628‐B‐010‐010‐MY3).