Browsing by Subject "Oxygen"

Filter results by typing the first few letters
Now showing 1 - 20 of 48
  • Thumbnail Image
    ItemOpen Access
    A mathematical model for persistent post-CSD vasoconstriction.
    (PLoS computational biology, 2020-07-15) Xu, Shixin; Chang, Joshua C; Chang, Joshua C; Chow, Carson C; Brennan, KC; Huang, Huaxiong
    Cortical spreading depression (CSD) is the propagation of a relatively slow wave in cortical brain tissue that is linked to a number of pathological conditions such as stroke and migraine. Most of the existing literature investigates the dynamics of short term phenomena such as the depolarization and repolarization of membrane potentials or large ion shifts. Here, we focus on the clinically-relevant hour-long state of neurovascular malfunction in the wake of CSDs. This dysfunctional state involves widespread vasoconstriction and a general disruption of neurovascular coupling. We demonstrate, using a mathematical model, that dissolution of calcium that has aggregated within the mitochondria of vascular smooth muscle cells can drive an hour-long disruption. We model the rate of calcium clearance as well as the dynamical implications on overall blood flow. Based on reaction stoichiometry, we quantify a possible impact of calcium phosphate dissolution on the maintenance of F0F1-ATP synthase activity.
  • Thumbnail Image
    ItemOpen Access
    Abnormal oxidative stress responses in fibroblasts from preeclampsia infants.
    (PloS one, 2014-01) Yang, Penghua; Dai, Aihua; Alexenko, Andrei P; Liu, Yajun; Stephens, Amanda J; Schulz, Laura C; Schust, Danny J; Roberts, R Michael; Ezashi, Toshihiko

    Background

    Signs of severe oxidative stress are evident in term placentae of infants born to mothers with preeclampsia (PE), but it is unclear whether this is a cause or consequence of the disease. Here fibroblast lines were established from umbilical cords (UC) delivered by mothers who had experienced early onset PE and from controls with the goal of converting these primary cells to induced pluripotent stem cells and ultimately trophoblast. Contrary to expectations, the oxidative stress responses of these non-placental cells from PE infants were more severe than those from controls.

    Methods and findings

    Three features suggested that UC-derived fibroblasts from PE infants responded less well to oxidative stressors than controls: 1) While all UC provided outgrowths in 4% O2, success was significantly lower for PE cords in 20% O2; 2) PE lines established in 4% O2 proliferated more slowly than controls when switched to 20% O2; 3) PE lines were more susceptible to the pro-oxidants diethylmaleate and tert-butylhydroquinone than control lines, but, unlike controls, were not protected by glutathione. Transcriptome profiling revealed only a few genes differentially regulated between PE lines and controls in 4% O2 conditions. However, a more severely stressed phenotype than controls, particularly in the unfolded protein response, was evident when PE lines were switched suddenly to 20% O2, thus confirming the greater sensitivity of the PE fibroblasts to acute changes in oxidative stress.

    Conclusions

    UC fibroblasts derived from PE infants are intrinsically less able to respond to acute oxidative stress than controls, and this phenotype is retained over many cell doublings. Whether the basis of this vulnerability is genetic or epigenetic and how it pertains to trophoblast development remains unclear, but this finding may provide a clue to the basis of the early onset, usually severe, form of PE.
  • Thumbnail Image
    ItemOpen Access
    Adult age differences in frontostriatal representation of prediction error but not reward outcome.
    (Cogn Affect Behav Neurosci, 2014-06) Samanez-Larkin, Gregory R; Worthy, Darrell A; Mata, Rui; McClure, Samuel M; Knutson, Brian
    Emerging evidence from decision neuroscience suggests that although younger and older adults show similar frontostriatal representations of reward magnitude, older adults often show deficits in feedback-driven reinforcement learning. In the present study, healthy adults completed reward-based tasks that did or did not depend on probabilistic learning, while undergoing functional neuroimaging. We observed reductions in the frontostriatal representation of prediction errors during probabilistic learning in older adults. In contrast, we found evidence for stability across adulthood in the representation of reward outcome in a task that did not require learning. Together, the results identify changes across adulthood in the dynamic coding of relational representations of feedback, in spite of preserved reward sensitivity in old age. Overall, the results suggest that the neural representation of prediction error, but not reward outcome, is reduced in old age. These findings reveal a potential dissociation between cognition and motivation with age and identify a potential mechanism for explaining changes in learning-dependent decision making in old adulthood.
  • Thumbnail Image
    ItemOpen Access
    Age-related differences in the neural bases of phonological and semantic processes.
    (Journal of cognitive neuroscience, 2014-12) Diaz, Michele T; Johnson, Micah A; Burke, Deborah M; Madden, David J
    Changes in language functions during normal aging are greater for phonological compared with semantic processes. To investigate the behavioral and neural basis for these age-related differences, we used fMRI to examine younger and older adults who made semantic and phonological decisions about pictures. The behavioral performance of older adults was less accurate and less efficient than younger adults' in the phonological task but did not differ in the semantic task. In the fMRI analyses, the semantic task activated left-hemisphere language regions, and the phonological task activated bilateral cingulate and ventral precuneus. Age-related effects were widespread throughout the brain and most often expressed as greater activation for older adults. Activation was greater for younger compared with older adults in ventral brain regions involved in visual and object processing. Although there was not a significant Age × Condition interaction in the whole-brain fMRI results, correlations examining the relationship between behavior and fMRI activation were stronger for younger compared with older adults. Our results suggest that the relationship between behavior and neural activation declines with age, and this may underlie some of the observed declines in performance.
  • Thumbnail Image
    ItemOpen Access
    Algal blooms and the nitrogen-enrichment hypothesis in Florida springs: evidence, alternatives, and adaptive management.
    (Ecol Appl, 2010-04) Heffernan, James B; Liebowitz, Dina M; Frazer, Thomas K; Evans, Jason M; Cohen, Matthew J
    Contradictions between system-specific evidence and broader paradigms to explain ecosystem behavior present a challenge for natural resource management. In Florida (U.S.A.) springs, increasing nitrate (NO3-) concentrations have been implicated as the cause of algal overgrowth via alleviation of N-limitation. As such, policy and management efforts have centered heavily on reduction of nitrogen (N) loads. While the N-limitation hypothesis appears well founded on broadly supported aquatic eutrophication models, several observations from Florida springs are inconsistent with this hypothesis in its present simplified form. First, NO3- concentration is not correlated with algal abundance across the broad population of springs and is weakly negatively correlated with primary productivity. Second, within individual spring runs, algal mats are largely confined to the headwater reaches within 250 m of spring vents, while elevated NO3- concentrations persist for several kilometers or more. Third, historic observations suggest that establishment of macroalgal mats often lags behind observed increases in NO3- by more than a decade. Fourth, although microcosm experiments indicate high thresholds for N-limitation of algae, experiments in situ have demonstrated only minimal response to N enrichment. These muted responses may reflect large nutrient fluxes in springs, which were sufficient to satisfy present demand even at historic concentrations. New analyses of existing data indicate that dissolved oxygen (DO) has declined dramatically in many Florida springs over the past 30 years, and that DO and grazer abundance are better predictors of algal abundance in springs than are nutrient concentrations. Although a precautionary N-reduction strategy for Florida springs is warranted given demonstrable effects of nutrient enrichment in a broad suite of aquatic systems worldwide, the DO-grazer hypothesis and other potential mechanisms merit increased scientific scrutiny. This case study illustrates the importance of an adaptive approach that explicitly evaluates paradigms as hypotheses and actively seeks alternative explanations.
  • Thumbnail Image
    ItemOpen Access
    Analysis of oxygen/glucose-deprivation-induced changes in SUMO3 conjugation using SILAC-based quantitative proteomics.
    (Journal of proteome research, 2012-02) Yang, W; Thompson, JW; Wang, Z; Wang, L; Sheng, H; Foster, MW; Moseley, MA; Paschen, W
    Transient cerebral ischemia dramatically activates small ubiquitin-like modifier (SUMO2/3) conjugation. In cells exposed to 6 h of transient oxygen/glucose deprivation (OGD), a model of ischemia, SUMOylation increases profoundly between 0 and 30 min following re-oxygenation. To elucidate the effect of transient OGD on SUMO conjugation of target proteins, we exposed neuroblastoma B35 cells expressing HA-SUMO3 to transient OGD and used stable isotope labeling with amino acids in cell culture (SILAC) to quantify OGD-induced changes in levels of specific SUMOylated proteins. Lysates from control and OGD-treated cells were mixed equally, and HA-tagged proteins were immunoprecipitated and analyzed by 1D-SDS-PAGE-LC-MS/MS. We identified 188 putative SUMO3-conjugated proteins, including numerous transcription factors and coregulators, and PIAS2 and PIAS4 SUMO ligases, of which 22 were increased or decreased more than ±2-fold. In addition to SUMO3, the levels of protein-conjugated SUMO1 and SUMO2, as well as ubiquitin, were all increased. Importantly, protein ubiquitination induced by OGD was completely blocked by gene silencing of SUMO2/3. Collectively, these results suggest several mechanisms for OGD-modulated SUMOylation, point to a number of signaling pathways that may be targets of SUMO-based signaling and recovery from ischemic stress, and demonstrate a tightly controlled crosstalk between the SUMO and ubiquitin conjugation pathways.
  • Thumbnail Image
    ItemOpen Access
    Baroreceptor afferents modulate brain excitation and influence susceptibility to toxic effects of hyperbaric oxygen.
    (Journal of applied physiology (Bethesda, Md. : 1985), 2014-09) Demchenko, Ivan T; Gasier, Heath G; Zhilyaev, Sergei Yu; Moskvin, Alexander N; Krivchenko, Alexander I; Piantadosi, Claude A; Allen, Barry W
    Unexplained adjustments in baroreflex sensitivity occur in conjunction with exposures to potentially toxic levels of hyperbaric oxygen. To investigate this, we monitored central nervous system, autonomic and cardiovascular responses in conscious and anesthetized rats exposed to hyperbaric oxygen at 5 and 6 atmospheres absolute, respectively. We observed two contrasting phases associated with time-dependent alterations in the functional state of the arterial baroreflex. The first phase, which conferred protection against potentially neurotoxic doses of oxygen, was concurrent with an increase in baroreflex sensitivity and included decreases in cerebral blood flow, heart rate, cardiac output, and sympathetic drive. The second phase was characterized by baroreflex impairment, cerebral hyperemia, spiking on the electroencephalogram, increased sympathetic drive, parasympatholysis, and pulmonary injury. Complete arterial baroreceptor deafferentation abolished the initial protective response, whereas electrical stimulation of intact arterial baroreceptor afferents prolonged it. We concluded that increased afferent traffic attributable to arterial baroreflex activation delays the development of excessive central excitation and seizures. Baroreflex inactivation or impairment removes this protection, and seizures may follow. Finally, electrical stimulation of intact baroreceptor afferents extends the normal delay in seizure development. These findings reveal that the autonomic nervous system is a powerful determinant of susceptibility to sympathetic hyperactivation and seizures in hyperbaric oxygen and the ensuing neurogenic pulmonary injury.
  • Thumbnail Image
    ItemOpen Access
    Bioluminescence imaging of glucose in tissue surrounding polyurethane and glucose sensor implants.
    (J Diabetes Sci Technol, 2010-09-01) Prichard, Heather L; Schroeder, Thies; Reichert, William M; Klitzman, Bruce
    BACKGROUND: The bioluminescence technique was used to quantify the local glucose concentration in the tissue surrounding subcutaneously implanted polyurethane material and surrounding glucose sensors. In addition, some implants were coated with a single layer of adipose-derived stromal cells (ASCs) because these cells improve the wound-healing response around biomaterials. METHODS: Control and ASC-coated implants were implanted subcutaneously in rats for 1 or 8 weeks (polyurethane) or for 1 week only (glucose sensors). Tissue biopsies adjacent to the implant were immediately frozen at the time of explant. Cryosections were assayed for glucose concentration profile using the bioluminescence technique. RESULTS: For the polyurethane samples, no significant differences in glucose concentration within 100 μm of the implant surface were found between bare and ASC-coated implants at 1 or 8 weeks. A glucose concentration gradient was demonstrated around the glucose sensors. For all sensors, the minimum glucose concentration of approximately 4 mM was found at the implant surface and increased with distance from the sensor surface until the glucose concentration peaked at approximately 7 mM at 100 μm. Then the glucose concentration decreased to 5.5-6.5 mM more than 100 μmm from the surface. CONCLUSIONS: The ASC attachment to polyurethane and to glucose sensors did not change the glucose profiles in the tissue surrounding the implants. Although most glucose sensors incorporate a diffusion barrier to reduce the gradient of glucose and oxygen in the tissue, it is typically assumed that there is no steep glucose gradient around the sensors. However, a glucose gradient was observed around the sensors. A more complete understanding of glucose transport and concentration gradients around sensors is critical.
  • Thumbnail Image
    ItemOpen Access
    BOLD signal compartmentalization based on the apparent diffusion coefficient.
    (Magn Reson Imaging, 2002-09) Song, Allen W; Fichtenholtz, Harlan; Woldorff, Marty
    Functional MRI (fMRI) can detect blood oxygenation level dependent (BOLD) hemodynamic responses secondary to neuronal activity. The most commonly used method for detecting fMRI signals is the gradient-echo echo-planar imaging (EPI) technique because of its sensitivity and speed. However, it is generally believed that a significant portion of these signals arises from large veins, with additional contribution from the capillaries and parenchyma. Early experiments using diffusion-weighted gradient-echo EPI have suggested that intra-voxel incoherent motion (IVIM) weighting inherent in the sequence can selectively attenuate contributions from different vessels based on the differences in the mobility of the blood within them. In the present study, we used similar approach to characterize the apparent diffusion coefficient (ADC) distribution within the activated areas of BOLD contrast. It is shown that the voxel values of the ADCs obtained from this technique can infer various vascular contributions to the BOLD signal.
  • Thumbnail Image
    ItemOpen Access
    Cell cycle Start is coupled to entry into the yeast metabolic cycle across diverse strains and growth rates.
    (Mol Biol Cell, 2016-01-01) Burnetti, Anthony J; Aydin, Mert; Buchler, Nicolas E
    Cells have evolved oscillators with different frequencies to coordinate periodic processes. Here we studied the interaction of two oscillators, the cell division cycle (CDC) and the yeast metabolic cycle (YMC), in budding yeast. Previous work suggested that the CDC and YMC interact to separate high oxygen consumption (HOC) from DNA replication to prevent genetic damage. To test this hypothesis, we grew diverse strains in chemostat and measured DNA replication and oxygen consumption with high temporal resolution at different growth rates. Our data showed that HOC is not strictly separated from DNA replication; rather, cell cycle Start is coupled with the initiation of HOC and catabolism of storage carbohydrates. The logic of this YMC-CDC coupling may be to ensure that DNA replication and cell division occur only when sufficient cellular energy reserves have accumulated. Our results also uncovered a quantitative relationship between CDC period and YMC period across different strains. More generally, our approach shows how studies in genetically diverse strains efficiently identify robust phenotypes and steer the experimentalist away from strain-specific idiosyncrasies.
  • Thumbnail Image
    ItemOpen Access
    Cerebral oxygenation and optimal vascular brain organization.
    (J R Soc Interface, 2015-06-06) Hadjistassou, Constantinos; Bejan, Adrian; Ventikos, Yiannis
    The cerebral vascular network has evolved in such a way so as to minimize transport time and energy expenditure. This is accomplished by a subtle combination of the optimal arrangement of arteries, arterioles and capillaries and the transport mechanisms of convection and diffusion. Elucidating the interaction between cerebral vascular architectonics and the latter physical mechanisms can catalyse progress in treating cerebral pathologies such as stroke, brain tumours, dementia and targeted drug delivery. Here, we show that brain microvascular organization is predicated on commensurate intracapillary oxygen convection and parenchymal diffusion times. Cross-species grey matter results for the rat, cat, rabbit and human reveal very good correlation between the cerebral capillary and tissue mean axial oxygen convective and diffusion time intervals. These findings agree with the constructal principle.
  • Thumbnail Image
    ItemOpen Access
    Co-activation of the amygdala, hippocampus and inferior frontal gyrus during autobiographical memory retrieval.
    (Neuropsychologia, 2005) Greenberg, Daniel L; Rice, Heather J; Cooper, Julie J; Cabeza, Roberto; Rubin, David C; Labar, Kevin S
    Functional MRI was used to investigate the role of medial temporal lobe and inferior frontal lobe regions in autobiographical recall. Prior to scanning, participants generated cue words for 50 autobiographical memories and rated their phenomenological properties using our autobiographical memory questionnaire (AMQ). During scanning, the cue words were presented and participants pressed a button when they retrieved the associated memory. The autobiographical retrieval task was interleaved in an event-related design with a semantic retrieval task (category generation). Region-of-interest analyses showed greater activation of the amygdala, hippocampus, and right inferior frontal gyrus during autobiographical retrieval relative to semantic retrieval. In addition, the left inferior frontal gyrus showed a more prolonged duration of activation in the semantic retrieval condition. A targeted correlational analysis revealed pronounced functional connectivity among the amygdala, hippocampus, and right inferior frontal gyrus during autobiographical retrieval but not during semantic retrieval. These results support theories of autobiographical memory that hypothesize co-activation of frontotemporal areas during recollection of episodes from the personal past.
  • Thumbnail Image
    ItemOpen Access
    Cognitive and neural contributors to emotion regulation in aging.
    (Social cognitive and affective neuroscience, 2011-04) Winecoff, Amy; Labar, Kevin S; Madden, David J; Cabeza, Roberto; Huettel, Scott A
    Older adults, compared to younger adults, focus on emotional well-being. While the lifespan trajectory of emotional processing and its regulation has been characterized behaviorally, few studies have investigated the underlying neural mechanisms. Here, older adults (range: 59-73 years) and younger adults (range: 19-33 years) participated in a cognitive reappraisal task during functional magnetic resonance imaging (fMRI) scanning. On each trial, participants viewed positive, negative or neutral pictures and either naturally experienced the image ('Experience' condition) or attempted to detach themselves from the image ('Reappraise' condition). Across both age groups, cognitive reappraisal activated prefrontal regions similar to those reported in prior studies of emotion regulation, while emotional experience activated the bilateral amygdala. Psychophysiological interaction analyses revealed that the left inferior frontal gyrus (IFG) and amygdala demonstrated greater inverse connectivity during the 'Reappraise' condition relative to the 'Experience' condition. The only regions exhibiting significant age differences were the left IFG and the left superior temporal gyrus, for which greater regulation-related activation was observed in younger adults. Controlling for age, increased performance on measures of cognition predicted greater regulation-related decreases in amygdala activation. Thus, while older and younger adults use similar brain structures for emotion regulation and experience, the functional efficacy of those structures depends on underlying cognitive ability.
  • Thumbnail Image
    ItemOpen Access
    Comprehensive pharmacokinetic studies and oral bioavailability of two Mn porphyrin-based SOD mimics, MnTE-2-PyP5+ and MnTnHex-2-PyP5+.
    (Free radical biology & medicine, 2013-05) Weitner, Tin; Kos, Ivan; Sheng, Huaxin; Tovmasyan, Artak; Reboucas, Julio S; Fan, Ping; Warner, David S; Vujaskovic, Zeljko; Batinic-Haberle, Ines; Spasojevic, Ivan
    The cationic, ortho Mn(III) N-alkylpyridylporphyrins (alkyl=ethyl, E, and n-hexyl, nHex) MnTE-2-PyP(5+) (AEOL10113, FBC-007) and MnTnHex-2-PyP(5+) have proven efficacious in numerous in vivo animal models of diseases having oxidative stress in common. The remarkable therapeutic efficacy observed is due to their: (1) ability to catalytically remove O2(•-) and ONOO(-) and other reactive species; (2) ability to modulate redox-based signaling pathways; (3) accumulation within critical cellular compartments, i.e., mitochondria; and (4) ability to cross the blood-brain barrier. The similar redox activities of both compounds are related to the similar electronic and electrostatic environments around the metal active sites, whereas their different bioavailabilities are presumably influenced by the differences in lipophilicity, bulkiness, and shape. Both porphyrins are water soluble, but MnTnHex-2-PyP(5+) is approximately 4 orders of magnitude more lipophilic than MnTE-2-PyP(5+), which should positively affect its ability to pass through biological membranes, making it more efficacious in vivo at lower doses. To gain insight into the in vivo tissue distribution of Mn porphyrins and its impact upon their therapeutic efficacy and mechanistic aspects of action, as well as to provide data that would ensure proper dosing regimens, we conducted comprehensive pharmacokinetic (PK) studies for 24h after single-dose drug administration. The porphyrins were administered intravenously (iv), intraperitoneally (ip), and via oral gavage at the following doses: 10mg/kg MnTE-2-PyP(5+) and 0.5 or 2mg/kg MnTnHex-2-PyP(5+). Drug levels in plasma and various organs (liver, kidney, spleen, heart, lung, brain) were determined and PK parameters calculated (Cmax, C24h, tmax, and AUC). Regardless of high water solubility and pentacationic charge of these Mn porphyrins, they are orally available. The oral availability (based on plasma AUCoral/AUCiv) is 23% for MnTE-2-PyP(5+) and 21% for MnTnHex-2-PyP(5+). Despite the fivefold lower dose administered, the AUC values for liver, heart, and spleen are higher for MnTnHex-2-PyP(5+) than for MnTE-2-PyP(5+) (and comparable for other organs), clearly demonstrating the better tissue penetration and tissue retention of the more lipophilic MnTnHex-2-PyP(5+).
  • Thumbnail Image
    ItemOpen Access
    Controlling Trophoblast Cell Fusion in the Human Placenta-Transcriptional Regulation of Suppressyn, an Endogenous Inhibitor of Syncytin-1.
    (Biomolecules, 2023-11) Sugimoto, Jun; Schust, Danny J; Sugimoto, Makiko; Jinno, Yoshihiro; Kudo, Yoshiki
    Cell fusion in the placenta is tightly regulated. Suppressyn is a human placental endogenous retroviral protein that inhibits the profusogenic activities of another well-described endogenous retroviral protein, syncytin-1. In this study, we aimed to elucidate the mechanisms underlying suppressyn's placenta-specific expression. We identified the promoter region and a novel enhancer region for the gene encoding suppressyn, ERVH48-1, and examined their regulation via DNA methylation and their responses to changes in the oxygen concentration. Like other endogenous retroviral genes, the ERVH48-1 promoter sequence is found within a characteristic retroviral 5' LTR sequence. The novel enhancer sequence we describe here is downstream of this LTR sequence (designated EIEs: ERV internal enhancer sequence) and governs placental expression. The placenta-specific expression of ERVH48-1 is tightly controlled by DNA methylation and further regulated by oxygen concentration-dependent, hypoxia-induced transcription factors (HIF1α and HIF2α). Our findings highlight the involvement of (1) tissue specificity through DNA methylation, (2) expression specificity through placenta-specific enhancer regions, and (3) the regulation of suppressyn expression in differing oxygen conditions by HIF1α and HIF2α. We suggest that these regulatory mechanisms are central to normal and abnormal placental development, including the development of disorders of pregnancy involving altered oxygenation, such as preeclampsia, pregnancy-induced hypertension, and fetal growth restriction.
  • Thumbnail Image
    ItemOpen Access
    Development and deployment of a field-portable soil O2 and CO2 gas analyzer and sampler.
    (PloS one, 2019-01) Brecheisen, Zachary S; Cook, Charles W; Heine, Paul R; Ryang, Junmo; Richter, Daniel deB
    Here we present novel method development and instruction in the construction and use of Field Portable Gas Analyzers study of belowground aerobic respiration dynamics of deep soil systems. Our Field-Portable Gas Analysis (FPGA) platform has been developed at the Calhoun Critical Zone Observatory (CCZO) for the measurement and monitoring of soil O2 and CO2 in a variety of ecosystems around the world. The FPGA platform presented here is cost-effective, lightweight, compact, and reliable for monitoring dynamic soil gasses in-situ in the field. The FPGA platform integrates off-the-shelf components for non-dispersive infrared (NDIR) CO2 measurement and electro-chemical O2 measurement via flow-through soil gas analyses. More than 2000 soil gas measurements have been made to date using these devices over 4 years of observations. Measurement accuracy of FPGAs is consistently high as validated via conventional bench-top gas chromatography. Further, time series representations of paired CO2 and O2 measurement under hardwood forests at the CCZO demonstrate the ability to observe and track seasonal and climatic patterns belowground with this FPGA platform. Lastly, the ability to analyze the apparent respiratory quotient, the ratio of apparent CO2 accumulation divided by apparent O2 consumption relative to the aboveground atmosphere, indicates a high degree of nuanced analyses are made possible with tools like FPGAs. In sum, the accuracy and reliability of the FPGA platform for soil gas monitoring allows for low-cost temporally extensive and spatially expansive field studies of deep soil respiration.
  • Thumbnail Image
    ItemOpen Access
    Differentiating sensitivity of post-stimulus undershoot under diffusion weighting: implication of vascular and neuronal hierarchy.
    (PLoS One, 2008-08-13) Harshbarger, Todd B; Song, Allen W
    The widely used blood oxygenation level dependent (BOLD) signal during brain activation, as measured in typical fMRI methods, is composed of several distinct phases, the last of which, and perhaps the least understood, is the post-stimulus undershoot. Although this undershoot has been consistently observed, its hemodynamic and metabolic sources are still under debate, as evidences for sustained blood volume increases and metabolic activities have been presented. In order to help differentiate the origins of the undershoot from vascular and neuronal perspectives, we applied progressing diffusion weighting gradients to investigate the BOLD signals during visual stimulation. Three distinct regions were established and found to have fundamentally different properties in post-stimulus signal undershoot. The first region, with a small but focal spatial extent, shows a clear undershoot with decreasing magnitude under increasing diffusion weighting, which is inferred to represent intravascular signal from larger vessels with large apparent diffusion coefficients (ADC), or high mobility. The second region, with a large continuous spatial extent in which some surrounds the first region while some spreads beyond, also shows a clear undershoot but no change in undershoot amplitude with progressing diffusion weighting. This would indicate a source based on extravascular and small vessel signal with smaller ADC, or lower mobility. The third region shows no significant undershoot, and is largely confined to higher order visual areas. Given their intermediate ADC, it would likely include both large and small vessels. Thus the consistent observation of this third region would argue against a vascular origin but support a metabolic basis for the post-stimulus undershoot, and would appear to indicate a lack of sustained metabolic rate likely due to a lower oxygen metabolism in these higher visual areas. Our results are the first, to our knowledge, to suggest that the post-stimulus undershoots have a spatial dependence on the vascular and neuronal hierarchy, and that progressing flow-sensitized diffusion weighting can help delineate these dependences.
  • Thumbnail Image
    ItemOpen Access
    Disrupting the vicious cycle created by NOX activation in sickle erythrocytes exposed to hypoxia/reoxygenation prevents adhesion and vasoocclusion.
    (Redox biology, 2019-07) MacKinney, Anson; Woska, Emily; Spasojevic, Ivan; Batinic-Haberle, Ines; Zennadi, Rahima
    In sickle cell disease (SCD), recurrent painful vasoocclusive crisis are likely caused by repeated episodes of hypoxia and reoxygenation. The sickle erythrocyte (SSRBC) adhesion plays an active role in vasoocclusion. However, the effect of prolonged reoxygenation after hypoxic stress on the molecular mechanisms in SSRBCs involved in onset of episodic vasoocclusion remain unclear. Exposure of human SSRBCs to hypoxia followed by 2 h reoxygenation, increased reactive oxygen species (ROS) production. Using specific pharmacological inhibitors, we show that excess ROS production in both reticulocytes and mature SSRBCs is regulated by NADPH oxidases (NOXs), the mitogen-activated protein kinase (ERK1/2), and G-protein coupled-receptor kinase 2 (GRK2). Consequently, SSRBC ROS create an intracellular positive feedback loop with ERK1/2 and GRK2 to mediate SSRBC adhesion to endothelium in vitro, and vasoocclusion in a mouse model of vasoocclusion in vivo. Importantly, reducing ROS levels in SSRBCs with redox-active manganese (Mn) porphyrins, commonly known as mimics of superoxide dismutase (SOD), disrupted the cycle created by ROS by affecting NOX and GRK2 activities and ERK1/2 phosphorylation, thus abrogating RBC-endothelial interactions. Inhibition adhesion assays show that LW (ICAM-4, CD242) blood group glycoprotein and CD44 are the RBC adhesion molecules mediating endothelial binding. Conversely, hypoxia/reoxygenation of normal RBCs failed to activate this feedback loop, and adhesion. These findings provide novel insights into the pathophysiological significance of the deleterious cycle created by NOX-dependent ROS, GRK2 and ERK1/2 within SSRBCs activated by hypoxia/reoxygenation, and involved in SSRBC adhesion and vasoocclusion. Thus, this loop in SSRBCs, which can be disrupted by Mn porphyrins, likely drives the profound SCD vasculopathy, and may point to new therapeutic targets to prevent chronic vasoocclusive events.
  • Thumbnail Image
    ItemOpen Access
    Early onset preeclampsia in a model for human placental trophoblast.
    (Proceedings of the National Academy of Sciences of the United States of America, 2019-03) Sheridan, Megan A; Yang, Ying; Jain, Ashish; Lyons, Alex S; Yang, Penghua; Brahmasani, Sambasiva R; Dai, Aihua; Tian, Yuchen; Ellersieck, Mark R; Tuteja, Geetu; Schust, Danny J; Schulz, Laura C; Ezashi, Toshihiko; Roberts, R Michael
    We describe a model for early onset preeclampsia (EOPE) that uses induced pluripotent stem cells (iPSCs) generated from umbilical cords of EOPE and control (CTL) pregnancies. These iPSCs were then converted to placental trophoblast (TB) representative of early pregnancy. Marker gene analysis indicated that both sets of cells differentiated at comparable rates. The cells were tested for parameters disturbed in EOPE, including invasive potential. Under 5% O2, CTL TB and EOPE TB lines did not differ, but, under hyperoxia (20% O2), invasiveness of EOPE TB was reduced. RNA sequencing analysis disclosed no consistent differences in expression of individual genes between EOPE TB and CTL TB under 20% O2, but, a weighted correlation network analysis revealed two gene modules (CTL4 and CTL9) that, in CTL TB, were significantly linked to extent of TB invasion. CTL9, which was positively correlated with 20% O2 (P = 0.02) and negatively correlated with invasion (P = 0.03), was enriched for gene ontology terms relating to cell adhesion and migration, angiogenesis, preeclampsia, and stress. Two EOPE TB modules, EOPE1 and EOPE2, also correlated positively and negatively, respectively, with 20% O2 conditions, but only weakly with invasion; they largely contained the same sets of genes present in modules CTL4 and CTL9. Our experiments suggest that, in EOPE, the initial step precipitating disease is a reduced capacity of placental TB to invade caused by a dysregulation of O2 response mechanisms and that EOPE is a syndrome, in which unbalanced expression of various combinations of genes affecting TB invasion provoke disease onset.
  • Thumbnail Image
    ItemOpen Access
    Efficacy of interferon beta-1a plus remdesivir compared with remdesivir alone in hospitalised adults with COVID-19: a double-bind, randomised, placebo-controlled, phase 3 trial.
    (The Lancet. Respiratory medicine, 2021-12) Kalil, Andre C; Mehta, Aneesh K; Patterson, Thomas F; Erdmann, Nathaniel; Gomez, Carlos A; Jain, Mamta K; Wolfe, Cameron R; Ruiz-Palacios, Guillermo M; Kline, Susan; Regalado Pineda, Justino; Luetkemeyer, Anne F; Harkins, Michelle S; Jackson, Patrick EH; Iovine, Nicole M; Tapson, Victor F; Oh, Myoung-Don; Whitaker, Jennifer A; Mularski, Richard A; Paules, Catharine I; Ince, Dilek; Takasaki, Jin; Sweeney, Daniel A; Sandkovsky, Uriel; Wyles, David L; Hohmann, Elizabeth; Grimes, Kevin A; Grossberg, Robert; Laguio-Vila, Maryrose; Lambert, Allison A; Lopez de Castilla, Diego; Kim, EuSuk; Larson, LuAnn; Wan, Claire R; Traenkner, Jessica J; Ponce, Philip O; Patterson, Jan E; Goepfert, Paul A; Sofarelli, Theresa A; Mocherla, Satish; Ko, Emily R; Ponce de Leon, Alfredo; Doernberg, Sarah B; Atmar, Robert L; Maves, Ryan C; Dangond, Fernando; Ferreira, Jennifer; Green, Michelle; Makowski, Mat; Bonnett, Tyler; Beresnev, Tatiana; Ghazaryan, Varduhi; Dempsey, Walla; Nayak, Seema U; Dodd, Lori; Tomashek, Kay M; Beigel, John H; ACTT-3 study group members

    Background

    Functional impairment of interferon, a natural antiviral component of the immune system, is associated with the pathogenesis and severity of COVID-19. We aimed to compare the efficacy of interferon beta-1a in combination with remdesivir compared with remdesivir alone in hospitalised patients with COVID-19.

    Methods

    We did a double-blind, randomised, placebo-controlled trial at 63 hospitals across five countries (Japan, Mexico, Singapore, South Korea, and the USA). Eligible patients were hospitalised adults (aged ≥18 years) with SARS-CoV-2 infection, as confirmed by a positive RT-PCR test, and who met one of the following criteria suggestive of lower respiratory tract infection: the presence of radiographic infiltrates on imaging, a peripheral oxygen saturation on room air of 94% or less, or requiring supplemental oxygen. Patients were excluded if they had either an alanine aminotransferase or an aspartate aminotransferase concentration more than five times the upper limit of normal; had impaired renal function; were allergic to the study product; were pregnant or breast feeding; were already on mechanical ventilation; or were anticipating discharge from the hospital or transfer to another hospital within 72 h of enrolment. Patients were randomly assigned (1:1) to receive intravenous remdesivir as a 200 mg loading dose on day 1 followed by a 100 mg maintenance dose administered daily for up to 9 days and up to four doses of either 44 μg interferon beta-1a (interferon beta-1a group plus remdesivir group) or placebo (placebo plus remdesivir group) administered subcutaneously every other day. Randomisation was stratified by study site and disease severity at enrolment. Patients, investigators, and site staff were masked to interferon beta-1a and placebo treatment; remdesivir treatment was given to all patients without masking. The primary outcome was time to recovery, defined as the first day that a patient attained a category 1, 2, or 3 score on the eight-category ordinal scale within 28 days, assessed in the modified intention-to-treat population, defined as all randomised patients who were classified according to actual clinical severity. Safety was assessed in the as-treated population, defined as all patients who received at least one dose of the assigned treatment. This trial is registered with ClinicalTrials.gov, NCT04492475.

    Findings

    Between Aug 5, 2020, and Nov 11, 2020, 969 patients were enrolled and randomly assigned to the interferon beta-1a plus remdesivir group (n=487) or to the placebo plus remdesivir group (n=482). The mean duration of symptoms before enrolment was 8·7 days (SD 4·4) in the interferon beta-1a plus remdesivir group and 8·5 days (SD 4·3) days in the placebo plus remdesivir group. Patients in both groups had a time to recovery of 5 days (95% CI not estimable) (rate ratio of interferon beta-1a plus remdesivir group vs placebo plus remdesivir 0·99 [95% CI 0·87-1·13]; p=0·88). The Kaplan-Meier estimate of mortality at 28 days was 5% (95% CI 3-7%) in the interferon beta-1a plus remdesivir group and 3% (2-6%) in the placebo plus remdesivir group (hazard ratio 1·33 [95% CI 0·69-2·55]; p=0·39). Patients who did not require high-flow oxygen at baseline were more likely to have at least one related adverse event in the interferon beta-1a plus remdesivir group (33 [7%] of 442 patients) than in the placebo plus remdesivir group (15 [3%] of 435). In patients who required high-flow oxygen at baseline, 24 (69%) of 35 had an adverse event and 21 (60%) had a serious adverse event in the interferon beta-1a plus remdesivir group compared with 13 (39%) of 33 who had an adverse event and eight (24%) who had a serious adverse event in the placebo plus remdesivir group.

    Interpretation

    Interferon beta-1a plus remdesivir was not superior to remdesivir alone in hospitalised patients with COVID-19 pneumonia. Patients who required high-flow oxygen at baseline had worse outcomes after treatment with interferon beta-1a compared with those given placebo.

    Funding

    The National Institute of Allergy and Infectious Diseases (USA).