Enhancing the diagnosis of functionally relevant coronary artery disease with machine learning.

Functionally relevant coronary artery disease (fCAD) can result in premature death or nonfatal acute myocardial infarction. Its early detection is a fundamentally important task in medicine. Classical detection approaches suffer from limited diagnostic accuracy or expose patients to possibly harmful radiation. Here we show how machine learning (ML) can outperform cardiologists in predicting the presence of stress-induced fCAD in terms of area under the receiver operating characteristic (AUROC: 0.71 vs. 0.64, p = 4.0E-13). We present two ML approaches, the first using eight static clinical variables, whereas the second leverages electrocardiogram signals from exercise stress testing. At a target post-test probability for fCAD of <15%, ML facilitates a potential reduction of imaging procedures by 15-17% compared to the cardiologist's judgement. Predictive performance is validated on an internal temporal data split as well as externally. We also show that combining clinical judgement with conventional ML and deep learning using logistic regression results in a mean AUROC of 0.74.

Detailed mapping of the complex fiber structure and white matter pathways of the chimpanzee brain.

Long-standing questions about human brain evolution may only be resolved through comparisons with close living evolutionary relatives, such as chimpanzees. This applies in particular to structural white matter (WM) connectivity, which continuously expanded throughout evolution. However, due to legal restrictions on chimpanzee research, neuroscience research currently relies largely on data with limited detail or on comparisons with evolutionarily distant monkeys. Here, we present a detailed magnetic resonance imaging resource to study structural WM connectivity in the chimpanzee. This open-access resource contains (1) WM reconstructions of a postmortem chimpanzee brain, using the highest-quality diffusion magnetic resonance imaging data yet acquired from great apes; (2) an optimized and validated method for high-quality fiber orientation reconstructions; and (3) major fiber tract segmentations for cross-species morphological comparisons. This dataset enabled us to identify phylogenetically relevant details of the chimpanzee connectome, and we anticipate that it will substantially contribute to understanding human brain evolution.

Evolutionary Adaptation of Protein Turnover in White Muscle of Stenothermal Antarctic Fish: Elevated Cold Compensation at Reduced Thermal Responsiveness.

Protein turnover is highly energy consuming and overall relates to an organism's growth performance varying largely between species, e.g., due to pre-adaptation to environmental characteristics such as temperature. Here, we determined protein synthesis rates and capacity of protein degradation in white muscle of the cold stenothermal Antarctic eelpout (Pachycara brachycephalum) and its closely related temperate counterpart, the eurythermal common eelpout (Zoarces viviparus). Both species were exposed to acute warming (P. brachycephalum, 0 °C + 2 °C day-1; Z. viviparus, 4 °C + 3 °C day-1). The in vivo protein synthesis rate (Ks) was monitored after injection of 13C-phenylalanine, and protein degradation capacity was quantified by measuring the activity of cathepsin D in vitro. Untargeted metabolic profiling by nuclear magnetic resonance (NMR) spectroscopy was used to identify the metabolic processes involved. Independent of temperature, the protein synthesis rate was higher in P. brachycephalum (Ks = 0.38-0.614 % day-1) than in Z. viviparus (Ks= 0.148-0.379% day-1). Whereas protein synthesis remained unaffected by temperature in the Antarctic species, protein synthesis in Z. viviparus increased to near the thermal optimum (16 °C) and tended to fall at higher temperatures. Most strikingly, capacities for protein degradation were about ten times higher in the Antarctic compared to the temperate species. These differences are mirrored in the metabolic profiles, with significantly higher levels of complex and essential amino acids in the free cytosolic pool of the Antarctic congener. Together, the results clearly indicate a highly cold-compensated protein turnover in the Antarctic eelpout compared to its temperate confamilial. Constant versus variable environments are mirrored in rigid versus plastic functional responses of the protein synthesis machinery.

Heat hardening enhances metabolite-driven thermoprotection in the Mediterranean mussel Mytilus galloprovincialis.

Introduction: Temperature affects organisms' metabolism and ecological performance. Owing to climate change, sea warming constituting a severe source of environmental stress for marine organisms, since it increases at alarming rates. Rapid warming can exceed resilience of marine organisms leading to fitness loss and mortality. However, organisms can improve their thermal tolerance when briefly exposed to sublethal thermal stress (heat hardening), thus generating heat tolerant phenotypes. Methods: We investigated the "stress memory" effect caused by heat hardening on M. galloprovincialis metabolite profile of in order to identify the underlying biochemical mechanisms, which enhance mussels' thermal tolerance. Results: The heat hardening led to accumulation of amino acids (e.g., leucine, isoleucine and valine), including osmolytes and cytoprotective agents with antioxidant and anti-inflammatory properties that can contribute to thermal protection of the mussels. Moreover, proteolysis was inhibited and protein turnover regulated by the heat hardening. Heat stress alters the metabolic profile of heat stressed mussels, benefiting the heat-hardened individuals in increasing their heat tolerance compared to the non-heat-hardened ones. Discussion: These findings provide new insights in the metabolic mechanisms that may reinforce mussels' tolerance against thermal stress providing both natural protection and potential manipulative tools (e.g., in aquaculture) against the devastating climate change effects on marine organisms.

Combined effects of salinity and intermittent hypoxia on mitochondrial capacity and reactive oxygen species efflux in the Pacific oyster, Crassostrea gigas.

Coastal environments commonly experience fluctuations in salinity and hypoxia-reoxygenation (H/R) stress that can negatively affect mitochondrial functions of marine organisms. Although intertidal bivalves are adapted to these conditions, the mechanisms that sustain mitochondrial integrity and function are not well understood. We determined the rates of respiration and reactive oxygen species (ROS) efflux in the mitochondria of oysters, Crassostrea gigas, acclimated to high (33 psu) or low (15 psu) salinity, and exposed to either normoxic conditions (control; 21% O2) or short-term hypoxia (24 h at <0.01% O2) and subsequent reoxygenation (1.5 h at 21% O2). Further, we exposed isolated mitochondria to anoxia in vitro to assess their ability to recover from acute (∼10 min) oxygen deficiency (<0.01% O2). Our results showed that mitochondria of oysters acclimated to high or low salinity did not show severe damage and dysfunction during H/R stress, consistent with the hypoxia tolerance of C. gigas. However, acclimation to low salinity led to improved mitochondrial performance and plasticity, indicating that 15 psu might be closer to the metabolic optimum of C. gigas than 33 psu. Thus, acclimation to low salinity increased mitochondrial oxidative phosphorylation rate and coupling efficiency and stimulated mitochondrial respiration after acute H/R stress. However, elevated ROS efflux in the mitochondria of low-salinity-acclimated oysters after acute H/R stress indicates a possible trade-off of higher respiration. The high plasticity and stress tolerance of C. gigas mitochondria may contribute to the success of this invasive species and facilitate its further expansion into brackish regions such as the Baltic Sea.

1H-NMR-Based Metabolic Profiling in Muscle and Liver Tissue of Juvenile Turbot (Scophthalmus maximus) Fed with Plant and Animal Protein Sources.

Circular economy driven feed ingredients and emerging protein sources, such as insects and microbial meals, has the potential to partially replace fishmeal in diets of high-trophic fish. Even though growth and feed performance are often unaffected at low inclusion levels, the metabolic effects are unknown. This study examined the metabolic response of juvenile turbot (Scophthalmus maximus) to diets with graded fishmeal replacement with plant, animal, and emerging protein sources (PLANT, PAP, and MIX) in comparison to a commercial-like diet (CTRL). A 1H-nuclear magnetic resonance (NMR) spectroscopy was used to assess the metabolic profiles of muscle and liver tissue after feeding the fish the experimental diets for 16 weeks. The comparative approach revealed a decrease in metabolites that are associated with energy deficiency in both tissues of fish fed with fishmeal-reduced diets compared to the commercial-like diet (CTRL). Since growth and feeding performance were unaffected, the observed metabolic response suggests that the balanced feed formulations, especially at lower fishmeal replacement levels, have the potential for industry application.

Protein Synthesis Determined from Non-Radioactive Phenylalanine Incorporated by Antarctic Fish.

Direct measurements of temperature-dependent weight gains are experimentally challenging and time-consuming in long-lived/slow-growing organisms such as Antarctic fish. Here, we reassess methodology to quantify the in vivo protein synthesis rate from amino acids, as a key component of growth. We tested whether it is possible to avoid hazardous radioactive materials and whether the analytical pathway chosen is robust against analytical errors. In the eelpout, Pachycara brachycephalum, 13C9H1115N1O2 phenylalanine was injected intraperitoneally and muscle tissue was sampled before injection and at 1.5 h time intervals up to 6 h thereafter. The incorporation of 13C15N-labeled-phenylalanine into muscle was monitored by quantification of bound and free phenylalanine through liquid chromatography-mass spectrometry. We found an increase in the pool of labeled, free phenylalanine in the cytosolic fraction that leveled off after 4.5 h. The labeled phenylalanine bound in the proteins increased linearly over time. The resulting protein synthesis rate (Ks) for P. brachycephalum was as low as 0.049 ± 0.021% day-1. This value and its variability were in good agreement with literature data obtained from studies using radioactive labels, indicating that this methodology is well suited for characterizing growth in polar fish under in situ conditions in remote areas or on research vessels.

Metabolic remodeling caused by heat hardening in the Mediterranean mussel Mytilus galloprovincialis.

Organisms can modify and increase their thermal tolerance faster and more efficiently after a brief exposure to sublethal thermal stress. This response is called 'heat hardening' as it leads to the generation of phenotypes with increased heat tolerance. The aim of this study was to investigate the impact of heat hardening on the metabolomic profile of Mytilus galloprovincialis in order to identify the associated adjustments of biochemical pathways that might benefit the mussels' thermal tolerance. Thus, mussels were exposed sequentially to two different phases (heat hardening and acclimation phases). To gain further insight into the possible mechanisms underlying the metabolic response of the heat-hardened M. galloprovincialis, metabolomics analysis was complemented by the estimation of mRNA expression of phosphoenolpyruvate carboxykinase (PEPCK), pyruvate kinase (PK) and alternative oxidase (AOX) implicated in the metabolic pathways of gluconeogenesis, glycolysis and redox homeostasis, respectively. Heat-hardened mussels showed evidence of higher activity of the tricarboxylic acid (TCA) cycle and diversification of upregulated metabolic pathways, possibly as a mechanism to increase ATP production and extend survival under heat stress. Moreover, formate and taurine accumulation provide an antioxidant and cytoprotective role in mussels during hypoxia and thermal stress. Overall, the metabolic responses in non-heat-hardened and heat-hardened mussels underline the upper thermal limits of M. galloprovincialis, set at 26°C, and are in accordance with the OCLTT concept. The ability of heat-hardened mussels to undergo a rapid gain and slow loss of heat tolerance may be an advantageous strategy for coping with intermittent and often extreme temperatures.

The impact of post-traumatic stress on the mental state of university hospital physicians - a cross sectional study.

BACKGROUND: Hospital physicians have an increased risk for post-traumatic stress caused by work-related trauma. This study examines the frequency of reported traumatic events (TE), post-traumatic stress (PTS) and its possible consequences for the mental state and work ability of physicians at a university hospital. METHODS: As part of the mandatory psychological risk assessment, n = 145 physicians (n = 56 female; 38.6%) were examined at a university hospital in Germany in a cross sectional study. TE, PTS and symptoms of depression and anxiety were assessed using the self-report questionnaires "Freiburger Screening Fragebogen to identify patients at risk for the development of a post-traumatic stress disorder in the group of severely injured patients" (PTBS-13), the "Patient Health Questionnaire" (PHQ-2) and the "Generalized Anxiety Disorder scale" (GAD-2). Work ability was assessed using a modified version of the questionnaire for workplace analysis (KFZA). The response rate was 52%. RESULTS: Traumatic events were experienced by n = 125 physicians (86.2%) throughout their whole career. Of these, 19 physicians (15.2%) reported PTS. PTS is reported by 12 of 56 female physicians (63.2%), compared to 7 of 89 reports of PTS by male physicians (36.8%). Physicians with PTS symptoms had higher depression scores (p = 0.007) compared to physicians without TE or with TE, but without PTS. Physicians with PTS reported significantly reduced work ability caused by constantly interrupted work (p = 0.03). Female gender was the greatest risk factor for the development of PTS. (p = 0.001). CONCLUSIONS: Physicians - especially females - with PTS may have an increased risk of developing depressive symptoms. Therefore, interventions aimed at reducing trauma-related stress symptoms may be helpful in improving mental health of hospital physicians. Further studies with more physicians from different hospitals are necessary to support the results.

Characterization of amine proton exchange for analyzing the specificity and intensity of the CEST effect: from humans to fish.

Chemical exchange saturation transfer (CEST) at about 2.8 ppm downfield from water is characterized besides other compounds by exchanging amine protons of relatively high concentration amino acids and is determined by several physiological (pH, T) and experimental (B0 , B1 , tsat ) parameters. Although the weighting of the CEST effect observed in vivo can be attributed mainly to one compound depending on the organism and organ, there are still several other amino acids, proteins and molecules that also contribute. These contributions in turn exhibit dependences and thus can lead to possible misinterpretation of the measured changes in the CEST effect. With this in mind, this work aimed to determine the exchange rates of six important amino acids as a function of pH and temperature, and thus to create multi-pool models that allow the accurate analysis of the CEST effect concerning different physiological and experimental parameters for a wide variety of organisms. The results show that small changes in the above parameters have a significant impact on the CEST effect at about 2.8 ppm for the chosen organisms, i.e. the human brain (37 °C) and the brain of polar cod (1.5 °C), furthermore, the specificity of the CEST effect observed in vivo can be significantly affected. Based on the exchange rates ksw (pH, T) determined for six metabolites in this study, it is possible to optimize the intensity and the specificity for the CEST effect of amino acids at about 2.8 ppm for different organisms with their specific physiological characteristics. By adjusting experimental parameters accordingly, this optimization will help to avoid possible misinterpretations of CEST measurements. Furthermore, the multi-pool models can be utilized to further optimize the saturation.

Mitochondrial capacity and reactive oxygen species production during hypoxia and reoxygenation in the ocean quahog, Arctica islandica.

Oxygen fluctuations are common in marine waters, and hypoxia-reoxygenation (H-R) stress can negatively affect mitochondrial metabolism. The long-lived ocean quahog, Arctica islandica, is known for its hypoxia tolerance associated with metabolic rate depression, yet the mechanisms that sustain mitochondrial function during oxygen fluctuations are not well understood. We used top-down metabolic control analysis (MCA) to determine aerobic capacity and control over oxygen flux in the mitochondria of quahogs exposed to short-term hypoxia (24 h <0.01% O2) and subsequent reoxygenation (1.5 h 21% O2) compared with normoxic control animals (21% O2). We demonstrated that flux capacity of the substrate oxidation and proton leak subsystems were not affected by hypoxia, while the capacity of the phosphorylation subsystem was enhanced during hypoxia associated with a depolarization of the mitochondrial membrane. Reoxygenation decreased the oxygen flux capacity of all three mitochondrial subsystems. Control over oxidative phosphorylation (OXPHOS) respiration was mostly exerted by substrate oxidation regardless of H-R stress, whereas control by the proton leak subsystem of LEAK respiration increased during hypoxia and returned to normoxic levels during reoxygenation. During hypoxia, reactive oxygen species (ROS) efflux was elevated in the LEAK state, whereas it was suppressed in the OXPHOS state. Mitochondrial ROS efflux returned to normoxic control levels during reoxygenation. Thus, mitochondria of A. islandica appear robust to hypoxia by maintaining stable substrate oxidation and upregulating phosphorylation capacity, but remain sensitive to reoxygenation. This mitochondrial phenotype might reflect adaptation of A. islandica to environments with unpredictable oxygen fluctuations and its behavioural preference for low oxygen levels.

Heat hardening enhances mitochondrial potential for respiration and oxidative defence capacity in the mantle of thermally stressed Mytilus galloprovincialis.

Ectotherms are exposed to a range of environmental temperatures and may face extremes beyond their upper thermal limits. Such temperature extremes can stimulate aerobic metabolism toward its maximum, a decline in aerobic substrate oxidation, and a parallel increase of anaerobic metabolism, combined with ROS generation and oxidative stress. Under these stressful conditions, marine organisms recruit several defensive strategies for their maintenance and survival. However, thermal tolerance of ectothermic organisms may be increased after a brief exposure to sub-lethal temperatures, a process known as "hardening". In our study, we examined the ability of M. galloprovincialis to increase its thermal tolerance under the effect of elevated temperatures (24, 26 and 28 °C) through the "hardening" process. Our results demonstrate that this process can increase the heat tolerance and antioxidant defense of heat hardened mussels through more efficient ETS activity when exposed to temperatures beyond 24 °C, compared to non-hardened individuals. Enhanced cell protection is reflected in better adaptive strategies of heat hardened mussels, and thus decreased mortality. Although hardening seems a promising process for the maintenance of aquacultured populations under increased seasonal temperatures, further investigation of the molecular and cellular mechanisms regulating mussels' heat resistance is required.

Temperature but not ocean acidification affects energy metabolism and enzyme activities in the blue mussel, Mytilus edulis.

In mosaic marine habitats, such as intertidal zones, ocean acidification (OA) is exacerbated by high variability of pH, temperature, and biological CO2 production. The nonlinear interactions among these drivers can be context-specific and their effect on organisms in these habitats remains largely unknown, warranting further investigation.We were particularly interested in Mytilus edulis (the blue mussel) from intertidal zones of the Gulf of Maine (GOM), USA, for this study. GOM is a hot spot of global climate change (average sea surface temperature (SST) increasing by >0.2°C/year) with >60% decline in mussel population over the past 40 years.Here, we utilize bioenergetic underpinnings to identify limits of stress tolerance in M. edulis from GOM exposed to warming and OA. We have measured whole-organism oxygen consumption rates and metabolic biomarkers in mussels exposed to control and elevated temperatures (10 vs. 15°C, respectively) and current and moderately elevated P CO2 levels (~400 vs. 800 µatm, respectively).Our study demonstrates that adult M. edulis from GOM are metabolically resilient to the moderate OA scenario but responsive to warming as seen in changes in metabolic rate, energy reserves (total lipids), metabolite profiles (glucose and osmolyte dimethyl amine), and enzyme activities (carbonic anhydrase and calcium ATPase).Our results are in agreement with recent literature that OA scenarios for the next 100-300 years do not affect this species, possibly as a consequence of maintaining its in vivo acid-base balance.

Machine Learning for Biomedical Time Series Classification: From Shapelets to Deep Learning.

With the biomedical field generating large quantities of time series data, there has been a growing interest in developing and refining machine learning methods that allow its mining and exploitation. Classification is one of the most important and challenging machine learning tasks related to time series. Many biomedical phenomena, such as the brain's activity or blood pressure, change over time. The objective of this chapter is to provide a gentle introduction to time series classification. In the first part we describe the characteristics of time series data and challenges in its analysis. The second part provides an overview of common machine learning methods used for time series classification. A real-world use case, the early recognition of sepsis, demonstrates the applicability of the methods discussed.

Enhancing statistical power in temporal biomarker discovery through representative shapelet mining.

MOTIVATION: Temporal biomarker discovery in longitudinal data is based on detecting reoccurring trajectories, the so-called shapelets. The search for shapelets requires considering all subsequences in the data. While the accompanying issue of multiple testing has been mitigated in previous work, the redundancy and overlap of the detected shapelets results in an a priori unbounded number of highly similar and structurally meaningless shapelets. As a consequence, current temporal biomarker discovery methods are impractical and underpowered. RESULTS: We find that the pre- or post-processing of shapelets does not sufficiently increase the power and practical utility. Consequently, we present a novel method for temporal biomarker discovery: Statistically Significant Submodular Subset Shapelet Mining (S5M) that retrieves short subsequences that are (i) occurring in the data, (ii) are statistically significantly associated with the phenotype and (iii) are of manageable quantity while maximizing structural diversity. Structural diversity is achieved by pruning non-representative shapelets via submodular optimization. This increases the statistical power and utility of S5M compared to state-of-the-art approaches on simulated and real-world datasets. For patients admitted to the intensive care unit (ICU) showing signs of severe organ failure, we find temporal patterns in the sequential organ failure assessment score that are associated with in-ICU mortality. AVAILABILITY AND IMPLEMENTATION: S5M is an option in the python package of S3M: github.com/BorgwardtLab/S3M.

Secondary Traumatic Stress, Mental State, and Work Ability in Nurses-Results of a Psychological Risk Assessment at a University Hospital.

Psychological risk assessment is a legal obligation for companies and part of occupational safety and employment protection in Germany. However, data from psychological risk assessments in nursing staff are scarce, although this population is at increased risk for secondary traumatic stress by patient experienced trauma. Therefore, our study aimed at examining the frequency of reported secondary trauma events, secondary traumatic stress, and its possible consequences for psychological well-being and work ability in nurses. N = 320 nurses (n = 280 female) were assessed at a University Hospital in Germany as part of the psychological risk assessment. Secondary traumatic events, secondary traumatic stress, and symptoms of depression and anxiety were measured using self-report questionnaires (PHQ-2, GAD-2), and work ability was assessed using a modified version of the questionnaire for workplace analysis (KFZA). Of 320 nurses, 292 (91.2%) experienced secondary trauma, and 74 nurses (25.3%) reported secondary traumatic symptoms. Nurses with secondary traumatic symptoms reported higher depression (p < 0.001) and anxiety scores (p < 0.001) compared to nurses without secondary trauma experience, and to nurses with secondary trauma experience but without secondary traumatic stress (both p < 0.001). Further, nurses with secondary traumatic stress reported significantly reduced work ability, social support and control over work, and increased emotional strain and labor time. Nurses with secondary traumatic stress may be at increased risk of developing major depression and anxiety disorders, and particularly need support in overcoming secondary traumatic experiences. Psychological risk assessment is a useful tool to identify groups at risk, and pave the way to implement strategies to improve mental well-being and prevent work ability in high risk groups.

Single and combined effects of the "Deadly trio" hypoxia, hypercapnia and warming on the cellular metabolism of the great scallop Pecten maximus.

In the ocean the main climate drivers affecting marine organisms are warming, hypercapnia, and hypoxia. We investigated the acute effects of warming (W), warming plus hypercapnia (WHc, ~1800 µatm CO2), warming plus hypoxia (WHo, ~12.1 kPa O2), and a combined exposure of all three drivers (Deadly Trio, DT) on king scallops (Pecten maximus). All exposures started at 14 °C and temperature was increased by 2 °C once every 48 h until the lethal temperature was reached (28 °C). Gill samples were taken at 14 °C, 18 °C, 22 °C, and 26 °C and analyzed for their metabolic response by 1H-nuclear magnetic resonance (NMR) spectroscopy. Scallops were most tolerant to WHc and most susceptible to oxygen reduction (WHo and DT). In particular under DT, scallops' mitochondrial energy metabolism was affected. Changes became apparent at 22 °C and 26 °C involving significant accumulation of glycogenic amino acids (e.g. glycine and valine) and anaerobic end-products (e.g. acetic acid and succinate). In line with these observations the LT50 was lower under the exposure to DT (22.5 °C) than to W alone (~ 25 °C) indicating a narrowing of the thermal niche due to an imbalance between oxygen demand and supply.

Early prediction of circulatory failure in the intensive care unit using machine learning.

Intensive-care clinicians are presented with large quantities of measurements from multiple monitoring systems. The limited ability of humans to process complex information hinders early recognition of patient deterioration, and high numbers of monitoring alarms lead to alarm fatigue. We used machine learning to develop an early-warning system that integrates measurements from multiple organ systems using a high-resolution database with 240 patient-years of data. It predicts 90% of circulatory-failure events in the test set, with 82% identified more than 2 h in advance, resulting in an area under the receiver operating characteristic curve of 0.94 and an area under the precision-recall curve of 0.63. On average, the system raises 0.05 alarms per patient and hour. The model was externally validated in an independent patient cohort. Our model provides early identification of patients at risk for circulatory failure with a much lower false-alarm rate than conventional threshold-based systems.

Non-invasive MRI Studies of Ventilatory and Cardiovascular Performance in Edible Crabs Cancer pagurus During Warming Under Elevated CO2 Levels.

The thermal tolerance of marine decapod crustacea is defined through their capacities for oxygen uptake and distribution. High ambient CO2 levels were previously shown to reduce hemolymph oxygen levels at enhanced cardiac performance during warming. This study investigated the impacts of warming under two CO2 levels on ventilation and hemolymph circulation in edible crabs Cancer pagurus. It also highlights changes in the ventilatory and cardiac pauses displayed by Decapoda under routine metabolism. Animals were exposed to step-wise, sub-critical warming (12-20°C over 5 days) under control (470 µatm) and high (1,350 µatm) water PCO2. Flow-through respirometry was combined with magnetic resonance imaging and infra-red photoplethysmography to allow for simultaneous, non-invasive measurements of metabolic rates ( M ˙ O 2 ), ventilation and cardiovascular performance. Crabs spent significantly more time in a low M ˙ O 2 state (metabolic pause), when experiencing high CO2 conditions above 16°C, compared to normocapnic warming. Heart rates leveled off beyond 18°C at any CO2 level. Cardiac output continued to increase with high-CO2-warming, due to elevated cardiac stroke volumes. Consequently, temperature-dependent branchial hemolymph flow remained unaffected by CO2. Instead, a suppressing effect of CO2 on ventilation was found beyond 16°C. These results indicate constrained oxygen uptake at stable cardiovascular performance in a decapod crustacean. Cancer pagurus: urn:lsid:zoobank.org:act:B750F89A-84B5-448B-8D80-EBD724A1C9D4.

In vivo31P-MRS of muscle bioenergetics in marine invertebrates: Future ocean limits scallops' performance.

OBJECT: Dynamic in vivo31P-NMR spectroscopy in combination with Magnetic Resonance Imaging (MRI) was used to study muscle bioenergetics of boreal and Arctic scallops (Pecten maximus and Chlamys islandica) to test the hypothesis that future Ocean Warming and Acidification (OWA) will impair the performance of marine invertebrates. MATERIALS & METHODS: Experiments were conducted following the recommendations for studies of muscle bioenergetics in vertebrates. Animals were long-term incubated under different environmental conditions: controls at 0 °C for C. islandica and 15 °C for P. maximus under ambient PCO2 of 0.039 kPa, a warm exposure with +5 °C (5 °C and 20 °C, respectively) under ambient PCO2 (OW group), and a combined exposure to warmed acidified conditions (5 °C and 20 °C, 0.112 kPa PCO2, OWA group). Scallops were placed in a 4.7 T MR animal scanner and the energetic status of the adductor muscle was determined under resting conditions using in vivo31P-NMR spectroscopy. The surplus oxidative flux (Qmax) was quantified by recording the recovery of arginine phosphate (PLA) directly after moderate swimming exercise of the scallops. RESULTS: Measurements led to reproducible results within each experimental group. Under projected future conditions resting PLA levels (PLArest) were reduced, indicating reduced energy reserves in warming exposed scallops per se. In comparison to vertebrate muscle tissue surplus Qmax of scallop muscle was about one order of magnitude lower. This can be explained by lower mitochondrial contents and capacities in invertebrate than vertebrate muscle tissue. Warm exposed scallops showed a slower recovery rate of PLA levels (kPLA) and a reduced surplus Qmax. Elevated PCO2 did not affected PLA recovery further. CONCLUSION: Dynamic in vivo31P-NMR spectroscopy revealed constrained residual aerobic power budgets in boreal and Arctic scallops under projected ocean warming and acidification indicating that scallops are susceptible to future climate change. The observed reduction in muscular PLArest of scallops coping with a warmer and acidified ocean may be linked to an enhanced energy demand and reduced oxygen partial pressures (PO2) in their body fluids. Delayed recovery from moderate swimming at elevated temperature is a result of reduced PLArest concentrations associated with a warm-induced reduction of a residual aerobic power budget.