Electrocortical Evidence for Impaired Affective Picture Processing after Long-Term Immobilization

The neurobehavioral risks associated with spaceflight are not well understood. In particular, little attention has been paid on the role of resilience, social processes and emotion regulation during long-duration spaceflight. Bed rest is a well-established spaceflight analogue that combines the adaptations associated with physical inactivity and semi-isolation and confinement. We here investigated the effects of 30 days of 6 degrees head-down tilt bed rest on affective picture processing using event-related potentials (ERP) in healthy men. Compared to a control group, bed rest participants showed significantly decreased P300 and LPP amplitudes to pleasant and unpleasant stimuli, especially in centroparietal regions, after 30 days of bed rest. Source localization revealed a bilateral lower activity in the posterior cingulate gyrus, insula and precuneus in the bed rest group in both ERP time frames for emotional, but not neutral stimuli

Short tandem repeats in the inhibitory domain of the mineralocorticoid receptor: prediction of a β-solenoid structure

BACKGROUND: The human mineralocorticoid receptor (MR) is one of the main components of the renin-angiotensin-aldosterone system (RAAS), the system that regulates the body exchange of water and sodium. The evolutionary origins of this protein predate those of renin and the RAAS; accordingly it has other roles, which are being characterized. The MR has two trans-activating ligand independent domains and one inhibitory domain (ID), which modulates the activity of the former. The structure of the ID is currently unknown. RESULTS: Here we report that the ID contains at least 15 tandem repeats of around 10 amino acids, which we computationally characterize in the human MR and in selected orthologs. This ensemble of repeats seems to have emerged around 450 million years ago, after the divergence of the MR from its close homolog, the glucocorticoid receptor, which does not possess the repeats. The region would have quickly expanded by successive duplication of the repeats stabilizing at its length in human MR shortly after divergence of tetrapoda from bony fishes 400 million years ago. Structural predictions, in combination with molecular dynamics simulations suggest that the repeat ensemble forms a {beta}-solenoid, namely a {beta}-helical fold with a polar core, stabilized by hydrogen-bonded ladders of polar residues. Our 3D-model, in conjunction with previous experimental data, implies a role of the {beta}-helical fold as a scaffold for multiple intra-and inter-molecular interactions and that these interactions are modulated via phosphorylation-dependent conformational changes. CONCLUSIONS: We, thus, propose that the structure of the repeat ensemble plays an important role in the coordination and sequential interactions of various MR partners and therefore in the functionality and specificity of MR

Head-Down Tilt Position, but Not the Duration of Bed Rest Affects Resting State Electrocortical Activity

Adverse cognitive and behavioral conditions and psychiatric disorders are considered a critical and unmitigated risk during future long-duration space missions (LDSM). Monitoring and mitigating crew health and performance risks during these missions will require tools and technologies that allow to reliably assess cognitive performance and mental well-being. Electroencephalography (EEG) has the potential to meet the technical requirements for the non-invasive and objective monitoring of neurobehavioral conditions during LDSM. Weightlessness is associated with fluid and brain shifts, and these effects could potentially challenge the interpretation of resting state EEG recordings. Head-down tilt bed rest (HDBR) provides a unique spaceflight analog to study these effects on Earth. Here, we present data from two long-duration HDBR experiments, which were used to systematically investigate the time course of resting state electrocortical activity during prolonged HDBR. EEG spectral power significantly reduced within the delta, theta, alpha, and beta frequency bands. Likewise, EEG source localization revealed significantly lower activity in a broad range of centroparietal and occipital areas within the alpha and beta frequency domains. These changes were observed shortly after the onset of HDBR, did not change throughout HDBR, and returned to baseline after the cessation of bed rest. EEG resting state functional connectivity was not affected by HDBR. The results provide evidence for a postural effect on resting state brain activity that persists throughout long-duration HDBR, indicating that immobilization and inactivity per se do not affect resting state electrocortical activity during HDBR. Our findings raise an important issue on the validity of EEG to identify the time course of changes in brain function during prolonged HBDR, and highlight the importance to maintain a consistent body posture during all testing sessions, including data collections at baseline and recovery

Spatial Updating Depends on Gravity

As we move through an environment the positions of surrounding objects relative to our body constantly change. Maintaining orientation requires spatial updating, the continuous monitoring of self-motion cues to update external locations. This ability critically depends on the integration of visual, proprioceptive, kinesthetic, and vestibular information. During weightlessness gravity no longer acts as an essential reference, creating a discrepancy between vestibular, visual and sensorimotor signals. Here, we explore the effects of repeated bouts of microgravity and hypergravity on spatial updating performance during parabolic flight. Ten healthy participants (four women, six men) took part in a parabolic flight campaign that comprised a total of 31 parabolas. Each parabola created about 20-25 s of 0 g, preceded and followed by about 20 s of hypergravity (1.8 g). Participants performed a visual-spatial updating task in seated position during 15 parabolas. The task included two updating conditions simulating virtual forward movements of different lengths (short and long), and a static condition with no movement that served as a control condition. Two trials were performed during each phase of the parabola, i.e., at 1 g before the start of the parabola, at 1.8 g during the acceleration phase of the parabola, and during 0 g. Our data demonstrate that 0 g and 1.8 g impaired pointing performance for long updating trials as indicated by increased variability of pointing errors compared to 1 g. In contrast, we found no support for any changes for short updating and static conditions, suggesting that a certain degree of task complexity is required to affect pointing errors. These findings are important for operational requirements during spaceflight because spatial updating is pivotal for navigation when vision is poor or unreliable and objects go out of sight, for example during extravehicular activities in space or the exploration of unfamiliar environments. Future studies should compare the effects on spatial updating during seated and free-floating conditions, and determine at which g-threshold decrements in spatial updating performance emerge

Capping protein-controlled actin polymerization shapes lipid membranes

Arp2/3 complex-mediated actin assembly at cell membranes drives the formation of protrusions or endocytic vesicles. To identify the mechanism by which different membrane deformations can be achieved, we reconstitute the basic membrane deformation modes of inward and outward bending in a confined geometry by encapsulating a minimal set of cytoskeletal proteins into giant unilamellar vesicles. Formation of membrane protrusions is favoured at low capping protein (CP) concentrations, whereas the formation of negatively bent domains is promoted at high CP concentrations. Addition of non-muscle myosin II results in full fission events in the vesicle system. The different deformation modes are rationalized by simulations of the underlying transient nature of the reaction kinetics. The relevance of the regulatory mechanism is supported by CP overexpression in mouse melanoma B16-F1 cells and therefore demonstrates the importance of the quantitative understanding of microscopic kinetic balances to address the diverse functionality of the cytoskeleton

Gender-Specific Cardiovascular Reactions to +Gz Interval Training on a Short Arm Human Centrifuge

Cardiovascular deconditioning occurs in astronauts during microgravity exposure, and may lead to post-flight orthostatic intolerance, which is more prevalent in women than men. Intermittent artificial gravity is a potential countermeasure, which can effectively train the cardiovascular mechanisms responsible for maintaining orthostatic integrity. Since cardiovascular responses may differ between women and men during gravitational challenges, information regarding gender specific responses during intermittent artificial gravity exposure plays a crucial role in countermeasure strategies. This study implemented a +Gz interval training protocol using a ground based short arm human centrifuge, in order to assess its effectiveness in stimulating the components of orthostatic integrity, such as diastolic blood pressure, heart rate and vascular resistance amongst both genders. Twenty-eight participants (12 men/16 women) underwent a two-round graded +1/2/1 Gz profile, with each +Gz phase lasting 4 min. Cardiovascular parameters from each phase (averaged last 60 sec) were analyzed for significant changes with respect to baseline values. Twelve men and eleven women completed the session without interruption, while five women experienced an orthostatic event. These women had a significantly greater height and baseline mean arterial pressure than their counterparts. Throughout the +Gz interval session, women who completed the session exhibited significant increases in heart rate and systemic vascular resistance index throughout all +Gz phases, while exhibiting increases in diastolic blood pressure during several +Gz phases. Men expressed significant increases from baseline in diastolic blood pressure throughout the session with heart rate increases during the +2Gz phases, while no significant changes in vascular resistance were recorded. Furthermore, women exhibited non-significantly higher heart rates over men during all phases of +Gz. Based on these findings, this protocol proved to consistently stimulate the cardiovascular systems involved in orthostatic integrity to a larger extent amongst women than men. Thus the +Gz gradients used for this interval protocol may be beneficial for women as a countermeasure against microgravity induced cardiovascular deconditioning, whereas men may require higher +Gz gradients. Lastly, this study indicates that gender specific cardiovascular reactions are apparent during graded +Gz exposure while no significant differences regarding cardiovascular responses were found between women and men during intermittent artificial gravity training

High-Intensity Exercise Mitigates Cardiovascular Deconditioning During Long-Duration Bed Rest

Head-down-tilt bed rest (HDT) mimics the changes in hemodynamics and autonomic cardiovascular control induced by weightlessness. However, the time course and reciprocal interplay of these adaptations, and the effective exercise protocol as a countermeasure need further clarification. The overarching aim of this work (as part of a European Space Agency sponsored long-term bed rest study) was therefore to evaluate the time course of cardiovascular hemodynamics and autonomic control during prolonged HDT and to assess whether high-intensity, short-duration exercise could mitigate these effects. A total of n = 23 healthy, young, male participants were randomly allocated to two groups: training (TRAIN, n = 12) and non-training (CTRL, n = 11) before undergoing a 60-day HDT. The TRAIN group underwent a resistance training protocol using reactive jumps (5–6 times per week), whereas the CTRL group did not perform countermeasures. Finger blood pressure (BP), heart rate (HR), and stroke volume were collected beat-by-beat for 10 min in both sitting and supine positions 7 days before HDT (BDC−7) and 10 days after HDT (R+10), as well as on the 2nd (HDT2), 28th (HDT28), and 56th (HDT56) day of HDT. We investigated (1) the isolated effects of long-term HDT by comparing all the supine positions (including BDC−7 and R+10 at 0 degrees), and (2) the reactivity of the autonomic response before and after long-term HDT using a specific postural stimulus (i.e., supine vs. sitting). Two-factorial linear mixed models were used to assess the time course of HDT and the effect of the countermeasure. Starting from HDT28 onwards, HR increased (p < 0.02) and parasympathetic tone decreased exclusively in the CTRL group (p < 0.0001). Moreover, after 60-day HDT, CTRL participants showed significant impairments in increasing cardiac sympathovagal balance and controlling BP levels during postural shift (supine to sitting), whereas TRAIN participants did not. Results show that a 10-day recovery did not compensate for the cardiovascular and autonomic deconditioning following 60-day HDT. This has to be considered when designing rehabilitation programs—not only for astronauts but also in general public healthcare. High-intensity, short-duration exercise training effectively minimized these impairments and should therefore deserve consideration as a cardiovascular deconditioning countermeasure for spaceflight

Auswirkung von Bettruhe in Kopftieflage auf Gehirnstruktur und -funktion

Introduction: Future long-duration exploratory missions to the Moon and Mars will expose several stressors to the human body that are likely to result in adverse cognitive and behavioral conditions. To assure mission success, it is critically to ascertain the neurobehavioral risks asso-ciated with such endeavors. Head-down tilt bed rest provides a unique analog to study some of the effects of spaceflight on Earth. Methods: As part of a randomized controlled study conducted by the French Institute for Space Medicine and Physiology in Toulouse, France in 2017, twenty young healthy men underwent 60 days of bed rest. Participants were randomly assigned to either a treatment group (n = 10) receiving a daily antioxidant supplement or a control group (n = 10) not receiving any treatment. To assess brain changes in response to prolonged immobilization, electroencephalography was employed both at rest, and while performing two standardized cognitive tasks measuring selec-tive attention and emotion processing at different time points before, during, and after the bed rest phase. Results: Irrespective of the assigned groups, distinct decreases in resting state spectral power were observed within the delta, theta, alpha, and beta frequency bands across all electrode sites with the onset of bed rest. An extended duration of the bed rest exposure did not further change this response. Spectral power returned to baseline level eight days after the cessation of bed rest. Additionally, data revealed a significant decrease of efficiency in the selective attention task after 60 days of bed rest that was corroborated by changes in event-related potential (ERP) ampli-tudes across several brain regions regardless of the assigned groups that did not recover eight days after bed rest. In addition, significantly lowered ERP amplitudes at frontal and parietal re-gions in response to positive and negative pictures of the emotion task were found in partici-pants tested after one month of bed rest compared to a control group tested before bed rest. Source localization confirmed a bilateral lower activity in the posterior cingulate gyrus, insula and precuneus in the bed rest group for emotional, but not neutral stimuli. Conclusion: The present work provides evidence for the adverse effects of long-duration bed rest on neurophysiology and behavior that could not be mitigated by the antioxidant supplement. Future research is needed to elucidate the mechanisms underlying these effects to promote the development of efficient target-specific countermeasures to assure human survival in space.Zukünftige Langzeit-Weltraummissionen zum Mond und Mars werden den menschlichen Körper verschiedenen Stressoren aussetzen, die höchstwahrscheinlich negative kognitive und verhaltensspezifische Auswirkungen haben können. Um den Erfolg dieser Missionen zu gewährleisten, ist es von entscheidender Bedeutung, die neurophysiologischen und verhaltensbezogenen Risiken, die mit solchen Unternehmungen einhergehen, zu ermitteln. Bettruhe in Kopftieflage bietet ein einzigartiges Analogmodell, um auch auf der Erde einige der Auswirkungen der Raumfahrt auf den Menschen zu untersuchen. Methodik: Im Rahmen einer randomisiert-kontrollierten Studie, die 2017 vom französischen Institut für Weltraummedizin und Physiologie in Toulouse, Frankreich, durchgeführt wurde, unterzogen sich zwanzig junge, gesunde Männer 60-tägiger Bettruhe. Die Teilnehmer wurden nach dem Zufallsprinzip entweder einer Behandlungsgruppe (n = 10), die täglich ein antioxidatives Nahrungsergänzungsmittel einnahm, oder einer Kontrollgruppe (n = 10), die keine Behandlung erhielt, zugewiesen. Um die Veränderungen des Gehirns als Reaktion auf die andauernde Inaktivität zu beurteilen, wurde ein Elektroenzephalogramm in Ruhe und während der Durchführung zweier standardisierter kognitiver Aufgaben zur Messung der selektiven Aufmerksamkeit und der Emotionsverarbeitung zu verschiedenen Zeitpunkten vor, während und nach der Bettruhephase aufgezeichnet. Ergebnisse: Unabhängig von der Gruppenzuordnung konnten deutliche Abnahmen der spektralen Leistungsdichte im Ruhezustand in den Delta-, Theta-, Alpha- und Beta-Frequenzbändern über alle Elektroden mit dem Beginn der Bettruhe beobachtet werden. Eine längere Dauer der Bettruhe änderte diese Reaktion nicht weiter. Die spektrale Leistungsdichte kehrte acht Tage nach Beendigung der Bettruhephase auf das Ausgangsniveau zurück. Zusätzlich wurde eine signifikant verringerte Effizienz während der Bearbeitung der selektiven Aufmerksamkeitsaufgabe nach 60 Tagen Bettruhe festgestellt, die mit veränderten Amplituden der ereigniskorrelierten Potenziale (EKP) in zahlreichen Hirnregionen einherging. Dieses Verhalten war unabhängig von den Gruppen und erholte sich auch acht Tage nach Bettruhe noch nicht. Darüber hinaus zeigten die Daten signifikant verringerte EKP-Amplituden in frontalen und parietalen Hirnregionen als Reaktion auf die positiven und negativen Bilder der Emotionsaufgabe bei Teilnehmern, die nach einem Monat Bettruhe getestet wurden, im Vergleich zu einer Kontrollgruppe, die vor der Bettruhe getestet wurde. Die Quellenlokalisation bestätigte eine geringere Aktivität im bilateralen posterioren cingulären Cortex, in der Insula und im Precuneus in der Bettruhegruppe für emotionale, aber nicht für neutrale Stimuli. Schlussfolgerung: Die vorliegende Arbeit liefert weitere Nachweise für die negative Auswirkung von Langzeit-Bettruhe auf die Neurophysiologie und das Verhalten, die durch die Einnahme eines antioxidativen Nahrungsergänzungsmittels nicht gemildert werden konnte. Zukünftige Untersuchungen sind notwendig, um die Mechanismen, die diesen Effekten zugrunde liegen, aufzuklären und die Entwicklung effizienter zielgerichteter Gegenmaßnahmen zu fördern, um das Überleben der Menschen im Weltraum zu sichern

Lichtgestalt und Dunkelziffer. Hartmut von Hentig und die Erziehungswissenschaft

Zenke CT. Lichtgestalt und Dunkelziffer. Hartmut von Hentig und die Erziehungswissenschaft. In: Vogel K, Bers C, Brauns J, Hild A, Stisser A, Horn K-P, eds. Wendungen und Windungen in der Erziehungswissenschaft. Empirische Studien. Beiträge zur Theorie und Geschichte der Erziehungswissenschaft. Vol 45. Bad Heilbrunn: Klinkhardt; 2018: 15-30