Browsing by Subject "OXYGEN"

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  • Lagerspets, Emi; Valbonetti, Evelyn; Eronen, Aleksi; Repo, Timo (2021)
    We report here novel Cu(I) thiophene carbaldimine catalysts for the selective aerobic oxidation of primary alcohols to their corresponding aldehydes and various diols to lactones or lactols. In the presence of the in situ generated Cu(I) species, a persistent radical (2,2,6,6-tetramethylpiperdine-N-oxyl (TEMPO)) and N-methylimidazole (NMI) as an auxiliary ligand, the reaction proceeds under aerobic conditions and at ambient temperature. Especially the catalytic system of 1-(thiophen-2-yl)-N-(4-(trifluoromethoxy)phenyl)methanimine (ligand L2) with copper(I)-iodide showed high reactivity for all kind of alcohols (benzylic, allylic and aliphatic). In the case of benzyl alcohol even 2.5 mol% of copper loading gave quantitative yield. Beside high activity under aerobic conditions, the catalysts ability to oxidize 1,5-pentadiol to the corresponding lactol (86% in 4 h) and Nphenyldiethanolamine to the corresponding morpholine derivate lactol (86% in 24 h) is particularly noteworthy.
  • Ouwerkerk, Janneke P.; van der Ark, Kees C. H.; Davids, Mark; Claassens, Nico J.; Finestra, Teresa Robert; de Vos, Willem M.; Belzer, Clara (2016)
    Akkermansia muciniphila colonizes the mucus layer of the gastrointestinal tract, where the organism can be exposed to the oxygen that diffuses from epithelial cells. To understand how A. muciniphila is able to survive and grow at this oxic-anoxic interface, its oxygen tolerance and response and reduction capacities were studied. A. muciniphila was found to be oxygen tolerant. On top of this, under aerated conditions, A. muciniphila showed significant oxygen reduction capacities and its growth rate and yield were increased compared to those seen under strict anaerobic conditions. Transcriptome analysis revealed an initial oxygen stress response upon exposure to oxygen. Thereafter, genes related to respiration were expressed, including those coding for the cytochrome bd complex, which can function as a terminal oxidase. The functionality of A. muciniphila cytochrome bd genes was proven by successfully complementing cytochrome-deficient Escherichia coli strain ECOM4. We conclude that A. muciniphila can use oxygen when it is present at nanomolar concentrations. IMPORTANCE This article explains how Akkermansia muciniphila, previously described as a strictly anaerobic bacterium, is able to tolerate and even benefit from low levels of oxygen. Interestingly, we measured growth enhancement of A. muciniphila and changes in metabolism as a result of the oxygen exposure. In this article, we discuss similarities and differences of this oxygen-responsive mechanism with respect to those of other intestinal anaerobic isolates. Taken together, we think that these are valuable data that indicate how anaerobic intestinal colonizing bacteria can exploit low levels of oxygen present in the mucus layer and that our results have direct relevance for applicability, as addition of low oxygen concentrations could benefit the in vitro growth of certain anaerobic organisms.
  • Rajendran, Jayasimman; Purhonen, Janne; Tegelberg, Saara; Smolander, Olli-Pekka; Mörgelin, Matthias; Rozman, Jan; Gailus-Durner, Valerie; Fuchs, Helmut; de Angelis, Martin Hrabe; Auvinen, Petri; Mervaala, Eero; Jacobs, Howard T.; Szibor, Marten; Fellman, Vineta; Kallijärvi, Jukka (2019)
    Alternative oxidase (AOX) is a non-mammalian enzyme that can bypass blockade of the complex III-IV segment of the respiratory chain (RC). We crossed a Ciona intestinalis AOX transgene into RC complex III (cIII)-deficient Bcs1l(p.S78G) knock-in mice, displaying multiple visceral manifestations and premature death. The homozygotes expressing AOX were viable, and their median survival was extended from 210 to 590 days due to permanent prevention of lethal cardiomyopathy. AOX also prevented renal tubular atrophy and cerebral astrogliosis, but not liver disease, growth restriction, or lipodystrophy, suggesting distinct tissue-specific pathogenetic mechanisms. Assessment of reactive oxygen species (ROS) production and damage suggested that ROS were not instrumental in the rescue. Cardiac mitochondrial ultrastructure, mitochondrial respiration, and pathological transcriptome and metabolome alterations were essentially normalized by AOX, showing that the restored electron flow upstream of cIII was sufficient to prevent cardiac energetic crisis and detrimental decompensation. These findings demonstrate the value of AOX, both as a mechanistic tool and a potential therapeutic strategy, for cIII deficiencies.
  • Melicher, Pavol; Dvorak, Petr; Krasylenko, Yuliya; Shapiguzov, Alexey; Kangasjärvi, Jaakko; Samaj, Jozef; Takac, Tomas (2022)
    Iron superoxide dismutase 1 (FSD1) was recently characterized as a plastidial, cytoplasmic, and nuclear enzyme with osmoprotective and antioxidant functions. However, the current knowledge on its role in oxidative stress tolerance is ambiguous. Here, we characterized the role of FSD1 in response to methyl viologen (MV)-induced oxidative stress in Arabidopsis thaliana. In accordance with the known regulation of FSD1 expression, abundance, and activity, the findings demonstrated that the antioxidant function of FSD1 depends on the availability of Cu2+ in growth media. Arabidopsis fsdl mutants showed lower capacity to decompose superoxide at low Cu2+ concentrations in the medium. Prolonged exposure to MV led to reduced ascorbate levels and higher protein carbonylation in fsdl mutants and transgenic plants lacking a plastid FSD1 pool as compared to the wild type. MV induced a rapid increase in FSD1 activity, followed by a decrease after 4 h long exposure. Genetic disruption of FSD1 negatively affected the hydrogen peroxide-decomposing ascorbate peroxidase in fsdl mutants. Chloroplastic localization of FSD1 is crucial to maintain redox homeostasis. Proteomic analysis showed that the sensitivity of fsd1 mutants to MV coincided with decreased abundances of ferredoxin and photosystem II light-harvesting complex proteins. These mutants have higher levels of chloroplastic proteases indicating an altered protein turnover in chloroplasts. Moreover, FSD1 disruption affects the abundance of proteins involved in the defense response. Collectively, the study provides evidence for the conditional antioxidative function of FSD1 and its possible role in signaling.
  • Piispanen, Wilhelm W.; Lundell, Richard V.; Tuominen, Laura J.; Räisänen-Sokolowski, Anne K. (2021)
    Introduction: Cold water imposes many risks to the diver. These risks include decompression illness, physical and cognitive impairment, and hypothermia. Cognitive impairment can be estimated using a critical flicker fusion frequency (CFFF) test, but this method has only been used in a few studies conducted in an open water environment. We studied the effect of the cold and a helium-containing mixed breathing gas on the cognition of closed circuit rebreather (CCR) divers. Materials and Methods: Twenty-three divers performed an identical dive with controlled trimix gas with a CCR device in an ice-covered quarry. They assessed their thermal comfort at four time points during the dive. In addition, their skin temperature was measured at 5-min intervals throughout the dive. The divers performed the CFFF test before the dive, at target depth, and after the dive. Results: A statistically significant increase of 111.7% in CFFF values was recorded during the dive compared to the pre-dive values (p < 0.0001). The values returned to the baseline after surfacing. There was a significant drop in the divers' skin temperature of 0.48 degrees C every 10 min during the dive (p < 0.001). The divers' subjectively assessed thermal comfort also decreased during the dive (p = 0.01). Conclusion: Our findings showed that neither extreme cold water nor helium-containing mixed breathing gas had any influence on the general CFFF profile described in the previous studies from warmer water and where divers used other breathing gases. We hypothesize that cold-water diving and helium-containing breathing gases do not in these diving conditions cause clinically relevant cerebral impairment. Therefore, we conclude that CCR diving in these conditions is safe from the perspective of alertness and cognitive performance.
  • Laurikkala, Johanna; Aneman, Anders; Peng, Alexander; Reinikainen, Matti; Pham, Paul; Jakkula, Pekka; Hästbacka, Johanna; Wilkman, Erika; Loisa, Pekka; Toppila, Jussi; Birkelund, Thomas; Blennow, Kaj; Zetterberg, Henrik; Skrifvars, Markus B. (2021)
    Background: Impaired cerebrovascular reactivity (CVR) is one feature of post cardiac arrest encephalopathy. We studied the incidence and features of CVR by near infrared spectroscopy (NIRS) and associations with outcome and biomarkers of brain injury. Methods: A post-hoc analysis of 120 comatose OHCA patients continuously monitored with NIRS and randomised to low- or high-normal oxygen, carbon dioxide and mean arterial blood pressure (MAP) targets for 48 h. The tissue oximetry index-(TOx) generated by the moving correlation coefficient between cerebral tissue oxygenation measured by NIRS and MAP was used as a dynamic index of CVR with-TOx > 0 indicating impaired reactivity and TOx > 0.3 used to delineate the lower and upper MAP bounds for disrupted CVR. TOx was analysed in the 0-12, 12-24, 24-48 h timeperiods and integrated over 0-48 h. The primary outcome was the association between TOx and six-month functional outcome dichotomised by the cerebral performance category (CPC1-2 good vs. 3-5 poor). Secondary outcomes included associations with MAP bounds for CVR and biomarkers of brain injury. Results: In 108 patients with sufficient data to calculate TOx, 76 patients (70%) had impaired CVR and among these, chronic hypertension was more common (58% vs. 31%, p = 0.002). Integrated TOx for 0-48 h was higher in patients with poor outcome than in patients with good outcome (0.89 95% CI [- 1.17 to 2.94] vs. - 2.71 95% CI [- 4.16 to - 1.26], p = 0.05). Patients with poor outcomes had a decreased upper MAP bound of CVR over time (p = 0.001), including the high-normal oxygen (p = 0.002), carbon dioxide (p = 0.012) and MAP (p = 0.001) groups. The MAP range of maintained CVR was narrower in all time intervals and intervention groups (p < 0.05). NfL concentrations were higher in patients with impaired CVR compared to those with intact CVR (43 IQR [15-650] vs 20 IQR [13-199] pg/ml, p = 0.042). Conclusion: Impaired CVR over 48 h was more common in patients with chronic hypertension and associated with poor outcome. Decreased upper MAP bound and a narrower MAP range for maintained CVR were associated with poor outcome and more severe brain injury assessed with NfL.
  • Vähätalo, Anssi V.; Xiao, Yihua; Salonen, Kalevi (2021)
    To explore the mechanisms that mineralize poorly bioavailable natural organic carbon (OC), we measured the mineralization of OC in two lake waters over long-term experiments (up to 623 days) at different pH and iron (Fe) levels. Both the microbial and photochemical mineralization of OC was higher at pH acidified to 4 than at the ambient pH 5 or an elevated pH 6. During 244 days, microbes mineralized up to 60% of OC in the 10-mu m filtrates of lake water and more than 27% in the 1-mu m filtrates indicating that large-sized microbes/grazers enhance the mineralization of OC. A reactivity continuum model indicated that the acidification stimulated the microbial mineralization of OC especially in the later (> weeks) phases of experiment when the bioavailability of OC was poor. The reactive oxygen species produced by light or microbial metabolism could have contributed to the mineralization of poorly bioavailable OC through photochemical and biogenic Fenton processes catalyzed by the indigenous Fe in lake water. When Fe was introduced to artificial lake water to the concentration found in the study lakes, it increased the densities of bacteria growing on solid phase extracted dissolved organic matter and in a larger extent at low pH 4 than at pH 5. Our results suggest that in addition to the photochemical Fenton process (photo-Fenton), microbes can transfer poorly bioavailable OC into labile forms and CO2 through extracellular Fe-catalyzed reactions (i.e., biogenic Fenton process). (C) 2020 Elsevier Ltd. All rights reserved.
  • Hasegawa, Yuki; Tang, Dave; Takahashi, Naoko; Hayashizaki, Yoshihide; Forrest, Alistair R. R.; Suzuki, Harukazu; FANTOM Consortium; Sajantila, Antti (2014)
  • Aneman, Anders; Laurikalla, Johanna; Pham, Paul; Wilkman, Erika; Jakkula, Pekka; Reinikainen, Matti; Toppila, Jussi; Skrifvars, Markus B. (2019)
    Background Approximately two-thirds of the mortality following out of hospital cardiac arrest is related to devastating neurological injury. Previous small cohort studies have reported an impaired cerebrovascular autoregulation following cardiac arrest, but no studies have assessed the impact of differences in oxygen and carbon dioxide tensions in addition to mean arterial pressure management. Methods This is a protocol and statistical analysis plan to assess the correlation between changes in cerebral tissue oxygenation and arterial pressure as measure of cerebrovascular autoregulation, the tissue oxygenation index, in patients following out of hospital cardiac arrest and in healthy volunteers. The COMACARE study included 120 comatose survivors of out of hospital cardiac arrest admitted to ICU and managed with low-normal or high-normal targets for mean arterial pressure, arterial oxygen and carbon dioxide partial pressures. In addition, 102 healthy volunteers have been investigated as a reference group for the tissue oxygenation index. In both cohorts, the cerebral tissue oxygenation was measured by near infrared spectroscopy. Conclusions Cerebrovascular autoregulation is critical to maintain homoeostatic brain perfusion. This study of changes in autoregulation following out of hospital cardiac arrest over the first 48 hours, as compared to data from healthy volunteers, will generate important physiological information that may guide the rationale and design of interventional studies.
  • Gammal, Johanna; Norkko, Joanna; Pilditch, Conrad A.; Norkko, Alf (2017)
    Coastal ecosystems are important because of the vital ecosystem functions and services they provide, but many are threatened by eutrophication and hypoxia. This results in loss of biodiversity and subsequent changes in ecosystem functioning. Consequently, the need for empirical field studies regarding biodiversity-ecosystem functioning in coastal areas has been emphasized. The present field study quantified the links between benthic macrofaunal communities (abundance, biomass, and species richness), sediment oxygen consumption, and solute fluxes (NO3- + NO2-, NH4+, PO43-, SiO4, Fe, Mn) along a 7.5-km natural gradient of seasonal hypoxia in the coastal northern Baltic Sea. Sampling was done in late August 2010 in the middle archipelago zone of the Hanko peninsula, Finland. As predicted, the macrofaunal communities were decimated with increasing hypoxia, and the nutrient transformation processes were changed at the sediment-water interface, with notably higher effluxes of phosphate and ammonium from the sediment. Solute fluxes varied even during normoxia, which implies a high context-dependency, and could be explained by even small variations in environmental variables such as organic matter and C/N ratios. Importantly, the low diversity benthic macrofaunal communities, which were dominated by Macoma balthica and the invasive Marenzelleria spp., had a large influence on the solute fluxes, especially under normoxia, but also under hypoxia.
  • Zinoviev, A. N.; Nordlund, K. (2017)
    The interatomic potential determines the nuclear stopping power in materials. Most ion irradiation simulation models are based on the universal-Ziegler-Biersack-Littmark (ZBL) potential (Ziegler et a1.,1983), which, however, is an average and hence may not describe the stopping of all ion-material combinations well. Here we consider pair-specific interatomic potentials determined experimentally and by density functional theory simulations with DMol approach (DMol software, 1997) to choose basic wave functions. The interatomic potentials calculated using the DMol approach demonstrate an unexpectedly good agreement with experimental data. Differences are mainly observed for heavy atom systems, which suggests they can be improved by extending a basis set and more accurately considering the relativistic effects. Experimental data prove that the approach of determining interatomic potentials from quasielastic scattering can be successfully used for modeling collision cascades in ion-solids collisions. The data obtained clearly indicate that the use of any universal potential is limited to internuclear distances R <7 a(f) (a(f) is the Firsov length). (C) 2017 Published by Elsevier B.V.
  • Davodi, Fatemeh; Mühlhausen, Elisabeth; Settipani, Daniel; Rautama, Eeva-Leena; Honkanen, Ari-Pekka; Huotari, Simo; Marzun, Galina; Taskinen, Pekka; Kallio, Tanja (2019)
    Core-shell nanoparticles represent a class of materials that exhibit a variety of properties. By rationally tuning the cores and the shells in such nanoparticles (NPs), a range of materials with tailorable properties can be produced which are of interest for a wide variety of applications. Herein, experimental and theoretical approaches have been combined to show the structural transformation of NPs resulting to the formation of either NiFexCy encapsulated in ultra-thin graphene layer (NiFe@UTG) or Ni3C/FexCy@FeOx NPs with the universal one-step pulse laser ablation in liquid (PLAL) method. Analysis suggests that carbon in Ni3C is the source for the carbon shell formation, whereas the final carbon-shell thickness in the NPs originates from the difference between Ni3C and FexCy phases stability at room temperature. The ternary Ni-Fe-C phase diagram calculations reveal the competition between carbon solubility in the studied metals (Ni and Fe) and their tendency toward oxidation as the key properties to produce controlled core-shell NP materials. As an application example, the electrocatalytic hydrogen evolution current on the different NPs is measured. The electrochemical analysis of the NPs reveals that NiFe@UTG has the best performance amongst the NPs in this study in both alkaline and acidic media.
  • Haapanen, Outi; Reidelbach, Marco; Sharma, Vivek (2020)
    Respiratory complex I (NADH:quinone oxidoreductase) plays a central role in generating the proton electrochemical gradient in mitochondrial and bacterial membranes, which is needed to generate ATP. Several high-resolution structures of complex I have been determined, revealing its intricate architecture and complementing the biochemical and biophysical studies. However, the molecular mechanism of long-range coupling between ubiquinone (Q) reduction and proton pumping is not known. Computer simulations have been applied to decipher the dynamics of Q molecule in the similar to 30 angstrom long Q tunnel. In this short report, we discuss the binding and dynamics of Q at computationally predicted Q binding sites, many of which are supported by structural data on complex I. We suggest that the binding of Q at these sites is coupled to proton pumping by means of conformational rearrangements in the conserved loops of core subunits.
  • Paananen, Riku O.; Javanainen, Matti; Holopainen, Juha M.; Vattulainen, Ilpo (2019)
    Dry eye syndrome (DES), one of the most common ophthalmological diseases, is typically caused by excessive evaporation of tear fluid from the ocular surface. Excessive evaporation is linked to impaired function of the tear film lipid layer (TFLL) that covers the aqueous tear film. The principles of the evaporation resistance of the TFLL have remained unknown, however. We combined atomistic simulations with Brewster angle microscopy and surface potential experiments to explore the organization and evaporation resistance of films composed of wax esters, one of the main components of the TFLL. The results provide evidence that the evaporation resistance of the TFLL is based on crystalline-state layers of wax esters and that the evaporation rate is determined by defects in the TFLL and its coverage on the ocular surface. On the basis of the results, uncovering the nonequilibrium spreading and crystallization of TFLL films has potential to reveal new means of treating DES.
  • Lindblad, Caroline; Raj, Rahul; Zeiler, Frederick A.; Thelin, Eric P. (2022)
    Introduction Multimodality monitoring of patients with severe traumatic brain injury (TBI) is primarily performed in neurocritical care units to prevent secondary harmful brain insults and facilitate patient recovery. Several metrics are commonly monitored using both invasive and non-invasive techniques. The latest Brain Trauma Foundation guidelines from 2016 provide recommendations and thresholds for some of these. Still, high-level evidence for several metrics and thresholds is lacking. Methods Regarding invasive brain monitoring, intracranial pressure (ICP) forms the cornerstone, and pressures above 22 mmHg should be avoided. From ICP, cerebral perfusion pressure (CPP) (mean arterial pressure (MAP)-ICP) and pressure reactivity index (PRx) (a correlation between slow waves MAP and ICP as a surrogate for cerebrovascular reactivity) may be derived. In terms of regional monitoring, partial brain tissue oxygen pressure (PbtO(2)) is commonly used, and phase 3 studies are currently ongoing to determine its added effect to outcome together with ICP monitoring. Cerebral microdialysis (CMD) is another regional invasive modality to measure substances in the brain extracellular fluid. International consortiums have suggested thresholds and management strategies, in spite of lacking high-level evidence. Although invasive monitoring is generally safe, iatrogenic hemorrhages are reported in about 10% of cases, but these probably do not significantly affect long-term outcome. Non-invasive monitoring is relatively recent in the field of TBI care, and research is usually from single-center retrospective experiences. Near-infrared spectrometry (NIRS) measuring regional tissue saturation has been shown to be associated with outcome. Transcranial doppler (TCD) has several tentative utilities in TBI like measuring ICP and detecting vasospasm. Furthermore, serial sampling of biomarkers of brain injury in the blood can be used to detect secondary brain injury development. Conclusions In multimodal monitoring, the most important aspect is data interpretation, which requires knowledge of each metric's strengths and limitations. Combinations of several modalities might make it possible to discern specific pathologic states suitable for treatment. However, the cost-benefit should be considered as the incremental benefit of adding several metrics has a low level of evidence, thus warranting additional research.
  • Lundell, Richard V; Arola, Olli; Suvilehto, Jari; Kuokkanen, Juha; Valtonen, Mika; Raisanen-Sokolowski, Anne K. (2019)
    Introduction: This is the first published study on decompression illness (DCI) and its treatment in Finland. Diving conditions are demanding, as even in the summer the water temperature below 20 meters' sea/fresh water (msw/mfw) is 4-10 degrees C. Technical diving has become more popular over the years, so the emphasis of this study was to describe DCI in technical divers and compare it with non-technical recreational divers. Methods: This study includes by estimation over 95% of all hyperbaric oxygen-treated DCI patients during the years 1999-2018 (n = 571). The cases were divided into technical divers (n = 200) and non-technical divers (n = 371). We focused on the differences between these two groups. Technical diving was defined as the usage of mixed breathing gases, closed circuit rebreather diving or planned decompression diving. Results: The mean annual number of treated DCI cases in Finland was 29 (range 16-38). The number of divers treated possibly indicate a shift towards technical diving. Technical dives were deeper and longer and were mainly performed in cold water or an overhead environment. Technical divers were more likely to utilize first aid 100% oxygen (FAO(2)) and sought medical attention earlier than non-technical divers. Symptom profiles were similar in both groups. Recompression was performed using USN Treatment Table Six in the majority of the cases and resulted in good final outcome. Eighty two percent were asymptomatic on completion of all recompression treatment(s). Conclusion: This 20-year observational study indicates a shift towards technical diving, and hence a more demanding and challenging style of diving among Finnish divers, with a surprisingly constant number of DCI cases over the years. There is still need for improvement in divers' education in use of FAO(2) for DCI symptoms. Fortunately, the outcome after recompression therapy is generally successful.
  • Candolin, Ulrika; Goncalves, Sara; Pant, Pankaj (2022)
    Early life conditions can have a decisive influence on viability later in life. However, the influence of embryo density within a nest or body cavity on subsequent viability has received little attention within an ecological setting. This is surprising given that embryos often compete for limited resources, such as nutrients and oxygen, and this could influence their viability later in life through carry-over and compensatory effects. We show that the density of fertilized eggs within the nests of threespine stickleback males (Gasterosteus aculeatus) influences their viability after hatching. Embryos from larger broods hatch earlier and at a smaller size than those from smaller broods, which reduces their survival until the age of four weeks. This indicates a trade-off between the number and viability of offspring that males can raise to the hatching stage, which could explain the high incidence of partial egg cannibalism in nest-brooding fishes-as a strategy to improve the survival of remaining offspring. These results highlight the importance of considering conditions at the embryonic stage when evaluating the impact of early life conditions on viability and the adaptive value of reproductive decisions.
  • CENTER-TBI High Resolution HR ICU; Zeiler, Frederick A.; Ercole, Ari; Cabeleira, Manuel; Raj, Rahul (2020)
    Background To date, the cerebral physiologic consequences of persistently elevated intracranial pressure (ICP) have been based on either low-resolution physiologic data or retrospective high-frequency data from single centers. The goal of this study was to provide a descriptive multi-center analysis of the cerebral physiologic consequences of ICP, comparing those with normal ICP to those with elevated ICP. Methods The Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) High-Resolution Intensive Care Unit (HR-ICU) sub-study cohort was utilized. The first 3 days of physiologic recording were analyzed, evaluating and comparing those patients with mean ICP <15 mmHg versus those with mean ICP > 20 mmHg. Various cerebral physiologic parameters were derived and evaluated, including ICP, brain tissue oxygen (PbtO(2)), cerebral perfusion pressure (CPP), pulse amplitude of ICP (AMP), cerebrovascular reactivity, and cerebral compensatory reserve. The percentage time and dose above/below thresholds were also assessed. Basic descriptive statistics were employed in comparing the two cohorts. Results 185 patients were included, with 157 displaying a mean ICP below 15 mmHg and 28 having a mean ICP above 20 mmHg. For admission demographics, only admission Marshall and Rotterdam CT scores were statistically different between groups (p = 0.017 andp = 0.030, respectively). The high ICP group displayed statistically worse CPP, PbtO(2), cerebrovascular reactivity, and compensatory reserve. The high ICP group displayed worse 6-month mortality (p <0.0001) and poor outcome (p = 0.014), based on the Extended Glasgow Outcome Score. Conclusions Low versus high ICP during the first 72 h after moderate/severe TBI is associated with significant disparities in CPP, AMP, cerebrovascular reactivity, cerebral compensatory reserve, and brain tissue oxygenation metrics. Such ICP extremes appear to be strongly related to 6-month patient outcomes, in keeping with previous literature. This work provides multi-center validation for previously described single-center retrospective results.
  • Heinonen, Jussi S.; Bohrson, Wendy A.; Spera, Frank J.; Brown, Guy A.; Scruggs, Melissa A.; Adams, Jenna V. (2020)
    The Magma Chamber Simulator (MCS) is a thermodynamic model that computes the phase, thermal, and compositional evolution of a multiphase–multicomponent system of a Fractionally Crystallizing resident body of magma (i.e., melt ± solids ± fluid), linked wallrock that may either be assimilated as Anatectic melts or wholesale as Stoped blocks, and multiple Recharge reservoirs (RnASnFC system, where n is the number of user-selected recharge events). MCS calculations occur in two stages; the first utilizes mass and energy balance to produce thermodynamically constrained major element and phase equilibria information for an RnASnFC system; this tool is informally called MCS-PhaseEQ, and is described in a companion paper (Bohrson et al. 2020). The second stage of modeling, called MCS-Traces, calculates the RASFC evolution of up to 48 trace elements and seven radiogenic and one stable isotopic system (Sr, Nd, Hf, 3xPb, Os, and O) for the resident melt. In addition, trace element concentrations are calculated for bulk residual wallrock and each solid (± fluid) phase in the cumulate reservoir and residual wallrock. Input consists of (1) initial trace element concentrations and isotope ratios for the parental melt, wallrock, and recharge magmas/stoped wallrock blocks and (2) solid-melt and solid–fluid partition coefficients (optional temperature-dependence) for stable phases in the resident magma and residual wallrock. Output can be easily read and processed from tabulated worksheets. We provide trace element and isotopic results for the same example cases (FC, R2FC, AFC, S2FC, and R2AFC) presented in the companion paper. These simulations show that recharge processes can be difficult to recognize based on trace element data alone unless there is an independent reference frame of successive recharge events or if serial recharge magmas are sufficiently distinct in composition relative to the parental magma or magmas on the fractionation trend. In contrast, assimilation of wallrock is likely to have a notable effect on incompatible trace element and isotopic compositions of the contaminated resident melt. The magnitude of these effects depends on several factors incorporated into both stages of MCS calculations (e.g., phase equilibria, trace element partitioning, style of assimilation, and geochemistry of the starting materials). Significantly, the effects of assimilation can be counterintuitive and very different from simple scenarios (e.g., bulk mixing of magma and wallrock) that do not take account phase equilibria. Considerable caution should be practiced in ruling out potential assimilation scenarios in natural systems based upon simple geochemical “rules of thumb”. The lack of simplistic responses to open-system processes underscores the need for thermodynamical RASFC models that take into account mass and energy conservation. MCS-Traces provides an unprecedented and detailed framework for utilizing thermodynamic constraints and element partitioning to document trace element and isotopic evolution of igneous systems. Continued development of the Magma Chamber Simulator will focus on easier accessibility and additional capabilities that will allow the tool to better reproduce the documented natural complexities of open-system magmatic processes.
  • Shapiguzov, Alexey; Nikkanen, Lauri; Fitzpatrick, Duncan; Vainonen, Julia P.; Gossens, Richard; Alseekh, Saleh; Aarabi, Fayezeh; Tiwari, Arjun; Blokhina, Olga; Panzarova, Klara; Benedikty, Zuzana; Tyystjärvi, Esa; Fernie, Alisdair R.; Trtilek, Martin; Aro, Eva-Mari; Rintamäki, Eevi; Kangasjarvi, Jaakko (2020)
    The Arabidopsis mutant rcd1 is tolerant to methyl viologen (MV). MV enhances the Mehler reaction, i.e. electron transfer from Photosystem I (PSI) to O-2, generating reactive oxygen species (ROS) in the chloroplast. To study the MV tolerance of rcd1, we first addressed chloroplast thiol redox enzymes potentially implicated in ROS scavenging. NADPH-thioredoxin oxidoreductase type C (NTRC) was more reduced in rcd1. NTRC contributed to the photosynthetic and metabolic phenotypes of rcd1, but did not determine its MV tolerance. We next tested rcd1 for alterations in the Mehler reaction. In rcd1, but not in the wild type, the PSI-to-MV electron transfer was abolished by hypoxic atmosphere. A characteristic feature of rcd1 is constitutive expression of mitochondrial dysfunction stimulon (MDS) genes that affect mitochondrial respiration. Similarly to rcd1, in other MDS-overexpressing plants hypoxia also inhibited the PSI-to-MV electron transfer. One possible explanation is that the MDS gene products may affect the Mehler reaction by altering the availability of O-2. In green tissues, this putative effect is masked by photosynthetic O-2 evolution. However, O-2 evolution was rapidly suppressed in MV-treated plants. Transcriptomic meta-analysis indicated that MDS gene expression is linked to hypoxic response not only under MV, but also in standard growth conditions. This article is part of the theme issue 'Retrograde signalling from endosymbiotic organelles'.