Peripheral skin cooling during hyper-gravity: hemodynamic reactions.

Introduction: Orthostatic dysregulation occurs during exposure to an increased gravitational vector and is especially common upon re-entering standard Earth gravity (1 g) after an extended period in microgravity (0 g). External peripheral skin cooling (PSC) has recently been described as a potent countermeasure against orthostatic dysregulation during heat stress and in lower body negative pressure (LBNP) studies. We therefore hypothesized that PSC may also be an effective countermeasure during hyper-gravity exposure (+Gz). Methods: To investigate this, we designed a randomized short-arm human centrifuge (SAHC) experiment ("Coolspin") to investigate whether PSC could act as a stabilizing factor in cardiovascular function during +Gz. Artificial gravity between +1 g and +4 g was generated by a SAHC. 18 healthy male volunteers completed two runs in the SAHC. PSC was applied during one of the two runs and the other run was conducted without cooling. Each run consisted of a 10-min baseline trial followed by a +Gz step protocol marked by increasing g-forces, with each step being 3 min long. The following parameters were measured: blood pressure (BP), heart rate (HR), stroke volume (SV), total peripheral resistance (TPR), cardiac output (CO). Furthermore, a cumulative stress index for each subject was calculated. Results: +Gz led to significant changes in primary as well as in secondary outcome parameters such as HR, SV, TPR, CO, and BP. However, none of the primary outcome parameters (HR, cumulative stress-index, BP) nor secondary outcome parameters (SV, TPR, CO) showed any significant differences-whether the subject was cooled or not cooled. Systolic BP did, however, tend to be higher amongst the PSC group. Conclusion: In conclusion, PSC during +Gz did not confer any significant impact on hemodynamic activity or orthostatic stability during +Gz. This may be due to lower PSC responsiveness of the test subjects, or an insufficient level of body surface area used for cooling. Further investigations are warranted in order to comprehensively pinpoint the exact degree of PSC needed to serve as a useful countermeasure system during +Gz.

Hypoxia Differentially Affects Healthy Men and Women During a Daytime Nap With a Dose-Response Relationship: a Randomized, Cross-Over Pilot Study.

Context: The use of daytime napping as a countermeasure in sleep disturbances has been recommended but its physiological evaluation at high altitude is limited. Objective: To evaluate the neuroendocrine response to hypoxic stress during a daytime nap and its cognitive impact. Design, Subject, and Setting: Randomized, single-blind, three period cross-over pilot study conducted with 15 healthy lowlander subjects (8 women) with a mean (SD) age of 29(6) years (Clinicaltrials identifier: NCT04146857, https://clinicaltrials.gov/ct2/show/NCT04146857?cond=napping&draw=3&rank=12). Interventions: Volunteers underwent a polysomnography, hematological and cognitive evaluation around a 90 min midday nap, being allocated to a randomized sequence of three conditions: normobaric normoxia (NN), normobaric hypoxia at FiO2 14.7% (NH15) and 12.5% (NH13), with a washout period of 1 week between conditions. Results: Primary outcome was the interbeat period measured by the RR interval with electrocardiogram. Compared to normobaric normoxia, RR during napping was shortened by 57 and 206 ms under NH15 and NH13 conditions, respectively (p < 0.001). Sympathetic predominance was evident by heart rate variability analysis and increased epinephrine levels. Concomitantly, there were significant changes in endocrine parameters such as erythropoietin (∼6 UI/L) and cortisol (∼100 nmol/L) (NH13 vs. NN, p < 0.001). Cognitive evaluation revealed changes in the color-word Stroop test. Additionally, although sleep efficiency was preserved, polysomnography showed lesser deep sleep and REM sleep, and periodic breathing, predominantly in men. Conclusion: Although napping in simulated altitude does not appear to significantly affect cognitive performance, sex-dependent changes in cardiac autonomic modulation and respiratory pattern should be considered before napping is prescribed as a countermeasure.

Cardiac Autonomic Modulations and Psychological Correlates in the Yukon Arctic Ultra: The Longest and the Coldest Ultramarathon.

Studies on human physical performance in extreme environments have effectively approached the investigation of adaptation mechanisms and their physiological limits. As scientific interest in the interplay between physiological and psychological aspects of performance is growing, we aimed to investigate cardiac autonomic control, by means of heart rate variability, and psychological correlates, in competitors of a subarctic ultramarathon, taking place over a 690 km course (temperatures between +5 and -47°C). At baseline (PRE), after 277 km (D1), 383 km (D2), and post-race (POST, 690 km), heart rate (HR) recordings (supine, 15 min), psychometric measurements (Profile of Mood States/POMS, Borg fatigue, and Karolinska Sleepiness Scale scores both upon arrival and departure) were obtained in 16 competitors (12 men, 4 women, 38.6 ± 9.5 years). As not all participants reached the finish line, comparison of finishers (FIN, n = 10) and non-finishers (NON, n = 6), allowed differential assessment of performance. Resting HR increased overall significantly at D1 (FIN +15.9; NON +14.0 bpm), due to a significant decrease in parasympathetic drive. This decrease was in FIN only partially recovered toward POST. In FIN only, baseline HR was negatively correlated with mean velocity [r -0.63 (P.04)] and parasympathetic drive [pNN50+: r -0.67 (P.03)], a lower HR and a higher vagal tone predicting a better performance. Moreover, in FIN, a persistent increase of the long-term self-similarity coefficient, assessed by detrended fluctuation analysis (DFAα2), was retrieved, possibly due to higher alertness. As for psychometrics, at D1, POMS Vigor decreased (FIN: -7.0; NON: -3.8), while Fatigue augmented (FIN: +6.9; NON: +5.0). Sleepiness increased only in NON, while Borg scales did not exhibit changes. Baseline comparison of mood states with normative data for athletes displayed significantly higher positive mood in our athletes. Results show that: the race conditions induced early decreases in parasympathetic drive; the extent of vagal withdrawal, associated to the timing of its recovery, is crucial for success; pre-competition lower resting HR predicts a better performance; psychological profile is reliably depicted by POMS, but not by Borg fatigue scales. Therefore, assessment of heart rate variability and psychological profile may monitor and partly predict performance in long-duration ultramarathon in extreme cold environment.

Modificaciones en la plasticidad hipocampal a corto plazo por efecto de un péptido diseñado y sintetizado con base en la estructura de una conotoxina / Changes in Short Term Hippocampal Plasticity caused by a Peptide Designed and Synthesized based on the Structure of a Conotoxine

Introducción: El diseño de instrumentos o moléculas inspiradas en la naturaleza hapermitido avanzar en diferentes áreas de la ciencia y tecnología. Objetivo: Evaluarcambios plásticos a corto plazo desencadenados por la administración intraperitonealde un péptido agonista del receptor de glutamato NMDA. Materiales y métodos:Se utilizaron ratas macho divididas en grupo péptido (a quienes se administróperitonealmente el péptido) y grupo control (a quienes se administró peritonealmenteel vehículo). Por técnicas de estereotaxia se localizaron electrodos de estimulacióny registro en las áreas hipocampales CA3 y CA1 respectivamente, con el ánimo deobtener los potenciales de campo y analizar cambios en su pendiente y amplitud porla aplicación de pares de estímulos, antes y después de la administración del péptido.Resultados: Aunque con la administración del péptido no hay cambios en variablessistémicas como la temperatura o la frecuencia cardiaca, sí se pueden modificar lospotenciales de campo, específicamente cuando el intervalo entre pares de estímuloses más corto (40 a 80 ms). Conclusión: El péptido evaluado en el presente trabajotiene efectos en la facilitación por pulsos pareados tanto en la amplitud como en lapendiente de potenciales de campo en el hipocampo de ratas, pero en los intervalosentre estímulos más cortos...

Introduction: Designing bio-inspired devicesor molecules has been a longstanding methodsupporting multiple advances in science and technology.Objective: To test the potential effectof intraperitoneal administration of the bio-inspiredpeptide on short-term plasticity. Materialsand methods: Male rats in two groups (peptidetreated and control) were used for registrationof hippocampal field potentials from CA1, afterpaired stimuli in CA3 contra lateral area. Results:Amplitude and slope of field potentials’,both before and after peptide administration,showed no changes in systemic factors (temperatureand heart rate), but statistical significancein short term plasticity in small inter stimuli interval(40 to 80 ms). Conclusion: The current researchshows effects on paired pulse facilitationcaused by peptide treatment, specifically on interstimuli interval shorter...

Plasticidad neuronal y fisiología aeroespacial: muchos hechos y algunas especulaciones / Neuronal plasticy and aerospace physiology: many facts and several speculations

La investigación de los procesos neurofisiológicos atrae el interés de las agencias aeroespaciales ya que la exploración humana, más allá de la atmósfera terrestre, implica el sometimiento del sistema nervioso a una serie de fenómenos con capacidad de generar cambios drásticos tanto en nivel celular como sistémico. Estudios arrojados en las últimas décadas demuestran que de realizarse exploraciones que requieran una exposición prolongada a estos fenómenos (por ejemplo un eventual viaje a Marte), uno de los principales componentes que podría afectarse en el sistema nervioso sería su plasticidad. La presente mini-revisión se enfoca en aquellos fenómenos que han sido descritos más frecuentemente y las consecuencias moleculares y celulares que pueden tener. Estos fenómenos básicamente son las radiaciones cósmicas, la aceleración gravitacional y de otros tipos, la hipoxia, la hiperoxia e hipobaria, la vibración, el confinamiento, los campos magnéticos y la nutrición. Es claro que la relación de estos fenómenos con su efecto neural será diferente dependiendo el tipo de vuelo al que nos refiramos (extra o intra-atmosférico) y que el listado presentado corresponde tan solo al conocimiento actual de los posibles factores fisicoquímicos implicados. Sin embargo, futuras investigaciones pueden develar aspectos hasta el momento ni siquiera contemplados. Adicionalmente, se propone una clasificación sobre los diferentes tipos de adaptaciones que acompañan la exposición del sistema nervioso, especialmente en el vuelo espacial

Registros in vivo de la facilitación por pulsos pareados y la potenciación a largo plazo en la región CA1 de la rata: descripción y prueba de una técnica para la evaluación de la plasticidad sináptica / Recording of PPF and LTP in neurons of CA1 in vivo in the rat: description and testing of the technique for evaluation of the synaptic plasticity

En Colombia, la investigación básica en el campo de la neurofisiología demanda la introducción de técnicas adecuadas para la avaluación de la actividad dinámica neuronal. La técnica que aquí se presenta describe los pasos esencialespara el registro poblacional de la actividad neuronal el aerea CA1 del hipocampo.Este tipo de registro resulta útil para estudiar cambios plásticos en el sistema nervioso, tales como la facilitación por pulsos pareados (PPF) y la potenciación a largo Plazo (LTP). Este último fenómeno es una evidencia experimental de cambios duraderos en eficiencia sináptica, que podrían bubyacer a procesos normales como el aprendizaje, o patológicos, como la epilepsia. En este trabajo se presentan de manera sencilla, los pasos básicos de estos procedimientos experimentales, a fin de que los investigadore colombianos puedan ejecutarlos con estándares de calidad aceptados internacionalmente. Además, se muestran algunos registros que han permitido poner en evidencia las carcterísticas básicas de los fenómenos de plasticidad neural antes mencionados. Como aporte final se recomiendan al lector los sitios de Internet adonde se puede consultar información adicionaly descargar algunos programas que resultarán útiles para la implementación de la técnica