Cardiovascular autonomic nervous system responses and orthostatic intolerance in astronauts and their relevance in daily medicine

Background: The harsh environmental conditions during space travel, particularly weightlessness, impose a major burden on the human body including the cardiovascular system. Given its importance in adjusting the cardiovascular system to environmental challenges, the autonomic nervous system has been in the focus of scientists and clinicians involved in human space flight. This review provides an overview on human autonomic research under real and simulated space conditions with a focus on orthostatic intolerance. Methods: The authors conducted a targeted literature search using Pubmed. Results: Overall, 120 articles were identified and included in the review. Conclusions: Postflight orthostatic intolerance is commonly observed in astronauts and could pose major risks when landing on another celestial body. The phenomenon likely results from changes in volume status and adaptation of the autonomic nervous system to weightlessness. Over the years, various non-pharmacological and pharmacological countermeasures have been investigated. In addition to enabling safe human space flight, this research may have implications for patients with disorders affecting cardiovascular autonomic control on Earth

Reactive Jumps Preserve Skeletal Muscle Structure, Phenotype, and Myofiber Oxidative Capacity in Bed Rest

© Copyright © 2020 Blottner, Hastermann, Weber, Lenz, Gambara, Limper, Rittweger, Bosutti, Degens and Salanova. Identification of countermeasures able to prevent disuse-induced muscle wasting is crucial to increase performance of crew members during space flight as well as ameliorate patient’s clinical outcome after long immobilization periods. We report on the outcome of short but high-impact reactive jumps (JUMP) as countermeasure during 60 days of 6° head-down tilt (HDT) bed rest on myofiber size, type composition, capillarization, and oxidative capacity in tissue biopsies (pre/post/recovery) from the knee extensor vastus lateralis (VL) and deep calf soleus (SOL) muscle of 22 healthy male participants (Reactive jumps in a sledge, RSL-study 2015–2016, DLR:envihab, Cologne). Bed rest induced a slow-to-fast myofiber shift (type I –>II) with an increased prevalence of hybrid fibers in SOL after bed rest without jumps (control, CTRL, p = 0.016). In SOL, JUMP countermeasure in bed rest prevented both fast and slow myofiber cross-sectional area (CSA) decrements (p = 0.005) in CTRL group. In VL, bed rest only induced capillary rarefaction, as reflected by the decrease in local capillary-to-fiber ratio (LCFR) for both type II (pre vs. post/R + 10, p = 0.028/0.028) and type I myofibers (pre vs. R + 10, p = 0.012), which was not seen in the JUMP group. VO2maxFiber (pL × mm–1 × min–1) calculated from succinate dehydrogenase (SDH)-stained cryosections (OD660 nm) showed no significant differences between groups. High-impact jump training in bed rest did not prevent disuse-induced myofiber atrophy in VL, mitigated phenotype transition (type I – >II) in SOL, and attenuated capillary rarefaction in the prime knee extensor VL however with little impact on oxidative capacity changes

Electrocardiographic changes during sustained normobaric hypoxia in patients after myocardial infarction

The safety of prolonged high-altitude stays and exercise for physically fit post-myocardial infarction (MI) patients is unclear. Myocardial tissue hypoxia and pulmonary hypertension can affect cardiac function and electrophysiology, possibly contributing to arrhythmias. We included four non-professional male athletes, clinically stable after left ventricular MI (three with ST-segment elevation MI and one with non-ST-segment elevation MI) treated with drug-eluting stents for single-vessel coronary artery disease. Oxygen levels were reduced to a minimum of 11.8%, then restored to 20.9%. We conducted electrocardiography (ECG), ergometry, and echocardiography assessments in normoxic and hypoxic conditions. With an average age of 57.8 ± 3.3 years and MI history 37 to 104 months prior, participants experienced a significant increase in QTc intervals during hypoxia using Bazett's (from 402 ± 13 to 417 ± 25 ms), Fridericia's (from 409 ± 12 to 419 ± 19 ms), and Holzmann's formulas (from 103 ± 4 to 107 ± 6%) compared to normoxia. This effect partially reversed during recovery. Echocardiographic signs of pulmonary hypertension during normobaric hypoxia correlated significantly with altered QTc intervals (p < 0.001). Despite good health and complete revascularization following MI, susceptibility to hypoxia-induced QTc prolongation and ventricular ectopic beats persists, especially during physical activity. MI survivors planning high-altitude activities should consult cardiovascular specialists with high-altitude medicine expertise

Brain structure and neurocognitive function in two professional mountaineers during 35 days of severe normobaric hypoxia

Background and purpose Animal studies suggest that exposure to severe ambient hypoxia for several days may have beneficial long-term effects on neurodegenerative diseases. Because, the acute risks of exposing human beings to prolonged severe hypoxia on brain structure and function are uncertain, we conducted a pilot study in healthy persons. Methods We included two professional mountaineers (participants A and B) in a 35-day study comprising an acclimatization period and 14 consecutive days with oxygen concentrations between 8% and 8.8%. They underwent cerebral magnetic resonance imaging at seven time points and a cognitive test battery covering a spectrum of cognitive domains at 27 time points. We analysed blood neuron specific enolase and neurofilament light chain levels before, during, and after hypoxia. Results In hypoxia, white matter volumes increased (maximum: A, 4.3% ± 0.9%; B, 4.5% ± 1.9%) whilst gray matter volumes (A, −1.5% ± 0.8%; B, −2.5% ± 0.9%) and cerebrospinal fluid volumes (A, −2.7% ± 2.4%; B, −5.9% ± 8.2%) decreased. Furthermore, the number (A, 11–17; B, 26–126) and volumes (A, 140%; B, 285%) of white matter hyperintensities increased in hypoxia but had returned to baseline after a 3.5-month recovery phase. Diffusion weighted imaging of the white matter indicated cytotoxic edema formation. We did not observe changes in cognitive performance or biochemical brain injury markers. Discussion In highly selected healthy individuals, severe sustained normobaric hypoxia over 2 weeks elicited reversible changes in brain morphology without clinically relevant changes in cognitive function or brain injury markers. The finding may pave the way for future translational studies assessing the therapeutic potential of hypoxia in neurodegenerative diseases

Measurement of the production of a W boson in association with a charm quark in pp collisions at √s = 7 TeV with the ATLAS detector

The production of a W boson in association with a single charm quark is studied using 4.6 fb−1 of pp collision data at s√ = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96+0.26−0.30 at Q 2 = 1.9 GeV2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio σ(W + +c¯¯)/σ(W − + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s−s¯¯¯ quark asymmetry

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

Measurement of χ c1 and χ c2 production with s√ = 7 TeV pp collisions at ATLAS

The prompt and non-prompt production cross-sections for the χ c1 and χ c2 charmonium states are measured in pp collisions at s√ = 7 TeV with the ATLAS detector at the LHC using 4.5 fb−1 of integrated luminosity. The χ c states are reconstructed through the radiative decay χ c → J/ψγ (with J/ψ → μ + μ −) where photons are reconstructed from γ → e + e − conversions. The production rate of the χ c2 state relative to the χ c1 state is measured for prompt and non-prompt χ c as a function of J/ψ transverse momentum. The prompt χ c cross-sections are combined with existing measurements of prompt J/ψ production to derive the fraction of prompt J/ψ produced in feed-down from χ c decays. The fractions of χ c1 and χ c2 produced in b-hadron decays are also measured

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal