Long-Term Bed Rest Delays the Circadian Phase of Core Body Temperature.

Spaceflight can be associated with sleep loss and circadian misalignment as a result of non-24 h light-dark cycles, operational shifts in work/rest cycles, high workload under pressure, and psychological factors. Head-down tilt bed rest (HDBR) is an established model to mimic some of the physiological and psychological adaptions observed in spaceflight. Data on the effects of HDBR on circadian rhythms are scarce. To address this gap, we analyzed the change in the circadian rhythm of core body temperature (CBT) in two 60-day HDBR studies sponsored by the European Space Agency [n = 13 men, age: 31.1 ± 8.2 years (M ± SD)]. CBT was recorded for 36 h using a non-invasive and validated dual-sensor heatflux technology during the 3rd and the 8th week of HDBR. Bed rest induced a significant phase delay from the 3rd to the 8th week of HDBR (16.23 vs. 16.68 h, p = 0.005, g = 0.85) irrespective of the study site (p = 0.416, g = -0.46), corresponding to an average phase delay of about 0.9 min per day of HDBR. In conclusion, long-term bed rest weakens the entrainment of the circadian system to the 24-h day. We attribute this effect to the immobilization and reduced physical activity levels associated with HDBR. Given the critical role of diurnal rhythms for various physiological functions and behavior, our findings highlight the importance of monitoring circadian rhythms in circumstances in which gravity or physical activity levels are altered.

Mode-of-action of the PROPELLA concept in fulminant myocarditis.

AIMS: Haemodynamic load induces cardiac remodelling via mechano-transduction pathways, which can further trigger inflammatory responses. We hypothesized that particularly in an inflammatory disorder such as myocarditis, a therapeutic strategy is required which, in addition to providing adequate circulatory support, unloads the left ventricle, decreases cardiac wall stress, and mitigates inflammatory responses. METHODS AND RESULTS: Axial flow pumps such as the Impella systems comply with these requirements. Here, we report a potential mode-of-action of prolonged Impella support (PROPELLA concept) in fulminant myocarditis, including a decrease in cardiac immune cell presence, and integrin α1, α5, α6, α10 and ß6 expression during unloading. CONCLUSION: PROPELLA may provide benefits beyond its primary function of mechanical circulatory support in the form of additional disease-altering effects, which may contribute to enhanced myocardial recovery/remission in patients with chronic fulminant myocarditis.

Increased core body temperature in astronauts during long-duration space missions.

Humans' core body temperature (CBT) is strictly controlled within a narrow range. Various studies dealt with the impact of physical activity, clothing, and environmental factors on CBT regulation under terrestrial conditions. However, the effects of weightlessness on human thermoregulation are not well understood. Specifically, studies, investigating the effects of long-duration spaceflight on CBT at rest and during exercise are clearly lacking. We here show that during exercise CBT rises higher and faster in space than on Earth. Moreover, we observed for the first time a sustained increased astronauts' CBT also under resting conditions. This increase of about 1 °C developed gradually over 2.5 months and was associated with augmented concentrations of interleukin-1 receptor antagonist, a key anti-inflammatory protein. Since even minor increases in CBT can impair physical and cognitive performance, both findings have a considerable impact on astronauts' health and well-being during future long-term spaceflights. Moreover, our findings also pinpoint crucial physiological challenges for spacefaring civilizations, and raise questions about the assumption of a thermoregulatory set point in humans, and our evolutionary ability to adapt to climate changes on Earth.

Lipoprotein(a)--An independent causal risk factor for cardiovascular disease and current therapeutic options.

It is widely accepted that elevated levels of lipoprotein(a) (Lp(a)) are associated with an increased risk for cardiovascular diseases. Several studies have identified Lp(a) as independent cardiovascular risk factor. Consequently, therapeutic concepts are targeting at lowering Lp(a) serum levels. To date, in Europe no pharmaceutical treatment to lower levels of Lp(a) is available. Current developments of pharmaceutical agents like the apolipoprotein-(B-100)-antisense mipomersen, inhibitors of PCSK9 and apolipoprotein-(a)-antisense have shown promising results in lowering Lp(a). Presently, the only available therapy to effectively reduce levels of Lp(a) is regular extracorporeal lipoprotein apheresis. Different apheresis methods show a similar lowering effect of about 60-70 % by a single session. Apart from one small-scale study there has been no randomized, controlled study which could prove that lowering Lp(a) will result in a risk reduction for cardiovascular disease. This review looks into the current scientific evidence of.

Comparison of cardiovascular and biomechanical parameters of supine lower body negative pressure and upright lower body positive pressure to simulate activity in 1/6 G and 3/8 G.

For future space exploration missions, it is important to determine the best method of simulating on Earth cardiovascular and biomechanical conditions for lunar and Martian gravities. For this purpose, we compared exercise performed within a lower body negative pressure (LBNP) and a lower body positive pressure (LBPP) chamber. Twelve subjects underwent a protocol of resting and walking (0.25 Froude) within supine LBNP and upright LBPP simulation. Each protocol was performed in simulated 1/6 G and 3/8 G. We assessed heart rate (HR), mean arterial blood pressure, oxygen consumption (Vo2), normalized stride length, normalized vertical peak ground reaction force, duty factor, cadence, perceived exertion (Borg), and comfort of the subject. A mixed linear model was employed to determine effects of the simulation on the respective parameters. Furthermore, parameters were compared with predicted values for lunar and Martian gravities to determine the method that showed the best agreement. During walking, all cardiovascular and biomechanical parameters were unaffected by the simulation used for lunar and Martian gravities. During rest, HR and Vo2 were lower in supine LBNP compared with upright LBPP. HR, Vo2, and normalized vertical peak ground reaction force obtained with supine LBNP and upright LBPP showed good agreement with predicted values. Since supine LBNP and upright LBPP are lacking significant differences, we conclude that both simulations are suited to simulate the cardiovascular and biomechanical conditions during activity in lunar and Martian gravities. Operational characteristics and the intended application should be considered when choosing either supine LBNP or upright LBPP to simulate partial gravities on Earth.

Toe blood pressure and leg muscle oxygenation with body posture.

INTRODUCTION: In 1980 Katkov and Chestukhin measured blood pressures and oxygenation invasively at various body tilt angles at different locations on the body, including the foot. To our knowledge, such measurements have not been performed noninvasively. Therefore, the purpose of this study was to measure toe blood pressure (TBP) and lower limb muscle oxygenation noninvasively at various body tilt angles, and to assess the use of a Finometer for noninvasive TBP measurements. Our noninvasive results are compared with those performed by Katkov and Chestukhin. We hypothesized that: 1) the Finometer provides a noninvasive measurement of TBP at different tilt angles; and 2) muscle oxygenation is highest with 0 and -6 degrees, and decreases with increased head-up tilt (HUT). METHODS: There were 10 subjects who were exposed to different body tilt angles (-6, 0, 10, 30, 70, and 90 degrees). At each angle we measured TBP noninvasively with a Finometer and muscle tissue oxygenation by near infrared spectroscopy. RESULTS: We found a strong correlation between TBP using the Finometer and TBP predicted by adding the hydrostatic component due to body tilt to the standard arm blood pressure measurement. At 10, 30, 70, and 90 degrees both TBP and tissue oxygenation were significantly different from the 0 degree (supine) level. Oxygenation decreased and TBP increased with higher HUT angles. No differences were observed in TBP or oxygenation between -6 and 0 degree. CONCLUSIONS: The Finometer accurately measures TBP noninvasively with body tilt. Also, muscle oxygenation is highest at small HUT angles and decreases with increased HUT.

Oxygen consumption during walking and running under fractional weight bearing conditions.

INTRODUCTION: Knowledge of changes in oxygen consumption during reduced body weight loading at different speed levels is important, in particular in astronauts who may lose aerobic fitness as well as in clinical patients (e.g., in obese individuals at walking speeds or in injured athletes at running speeds). Therefore, the aim of this study was to analyze oxygen consumption during unloaded walking and running. METHODS: Oxygen consumption (Vo2), heart rate (HR), and Borg rating of perceived exertion (Borg RPE) were quantified in 10 healthy young female and male volunteers at 3 body weight (BW) conditions (100%, 66%, and 33% BW) and 4 treadmill speeds (slow walking at 0.4 m x s(-1), comfortable walking at 1.3 m x s(-1), slow running at 2.2 m x s(-1), and moderately fast running at 3.1 m x s(-1)). Unloading was achieved in a waist-high chamber with increased pressure called Lower Body Positive Pressure (LBPP). RESULTS: All parameters (Vo2, HR, and Borg RPE) decreased during unloaded walking and running. Interestingly, our findings confirm a specific linear relationship between each parameter and treadmill speed for each BW condition with smaller slope angles at higher levels of unloading (e.g., for Vo2, the slope angle decreased from 11.9 at 100% BW to 4.4 at 33% BW). DISCUSSION: Oxygen consumption, heart rate, and Borg rating of perceived exertion are reduced during unloaded exercise with a relatively greater decline at higher treadmill speeds. That is, the higher the treadmill's speed in unloaded conditions, the relatively "easier" it is to exercise.