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- Louwies, T., et al.
(författare)
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Separate and combined effects of hypoxia and horizontal bed rest on retinal blood vessel diameters
- 2016
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Ingår i: Investigative Ophthalmology and Visual Science. - : Association for Research in Vision and Ophthalmology Inc.. - 0146-0404 .- 1552-5783. ; 57:11, s. 4927-4932
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE. To assess the separate and combined effects of exposure to prolonged and sustained recumbency (bed rest) and hypoxia on retinal microcirculation. METHODS. Eleven healthy male subjects (mean 6 SD age = 27 ± 6 years; body mass index [BMI] = 23.7 ± 3.0 kg m-2) participated in a repeated-measures crossover design study comprising three 21-day interventions: normoxic bed rest (NBR; partial pressure of inspired O2, PiO2 = 133.1 ± 0.3 mm Hg); hypoxic ambulation (HAMB; PiO2 = 90.0 6 0.4 mm Hg), and hypoxic bed rest (HBR; PiO2 = 90.0 ± 0.4 mm Hg). Central retinal arteriolar (CRAE) and venular (CRVE) equivalents were measured at baseline and at regular intervals during each 21- day intervention. RESULTS. Normoxic bed rest caused a progressive reduction in CRAE, with the change in CRAE relative to baseline being highest on day 15 (ΔDCRAE = -7.5 µm; 95% confidence interval [CI]: -10.8 to -4.2; P < 0.0001). Hypoxic ambulation resulted in a persistent 21-day increase in CRAE, reaching a maximum on day 4 (DCRAE = 9.4 µm; 95% CI: 6.0-12.7; P < 0.0001). During HBR, the increase in CRAE was highest on day 3 (ΔDCRAE = 4.5 µm; 95% CI: 1.2-7.8; P = 0.007), but CRAE returned to baseline levels thereafter. Central retinal venular equivalent decreased during NBR and increased during HAMB and HBR. The reduction in CRVE during NBR was highest on day 1 (ΔDCRVE = -7.9 µm; 95 CI: -13.3 to -2.5), and the maximum ΔDCRVE during HAMB (24.6 µm; 95% CI: 18.9-30.3) and HBR (15.2 µm; 95% CI: 9.8-20.5) was observed on days 10 and 3, respectively. CONCLUSIONS. The diameters of retinal blood vessels exhibited a dynamic response to hypoxia and bed rest, such that retinal vasodilation was smaller during combined bed rest and hypoxia than during hypoxic exposure.
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- Salvadego, D, et al.
(författare)
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Skeletal muscle oxidative function after a 10-day exposure to hypoxia and microgravity
- 2013
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Konferensbidrag (refereegranskat)abstract
- Skeletal muscle oxidative function was evaluated before (CTRL) and after 10 days of normobaric hypoxic (inspired PO2 12.5kPa) bed rest (H-BR) and normoxic bed rest (BR) in nine healthy young men (age: 24.1±1.7 years [mean±SD]). H-BR was taken as a simulation of lunar habitats. Pulmonary gas exchange and vastus lateralis muscle fractional O2-extraction (by near-infrared spectroscopy) were determined during an incremental cycle ergometer (CE) and one-leg knee extension (KE) exercise up to volitional exhaustion. Mitochondrial respiration was evaluated by high-resolution respirometry in permeabilized vastus lateralis fibers. During CE, peak pulmonary O2-uptake ( VO 2peak) significantly decreased by ~7 and 9 % after BR andH-BR, respectively. During KE, V O 2peak decreased significantly (by ~6%) after BR (0.83±0.07 vs. 0.89±0.08 [CTRL] L·min-1), but not after H-BR (0.86±0.07 vs. 0.90±0.07). Skeletal muscle peak fractional O2-extraction was significantly lower after BR (60±12 vs. 70±11% [CTRL]), but not after H-BR (65±12 vs. 71±10). No significant changes were observed in maximal ADP-stimulated mitochondrial respiration either after BR (48.9±11.5pmolO2·s-1·mg-1 wet weight) or H-BR (42.8±7.8) vs. CTRL (46.6±6.6). After relieving, by the KE exercise protocol, constraints related to cardiovascular O2-delivery, oxidative function in vivo was still impaired after BR, while a less pronounced impairment was evident after H-BR. Mitochondrial respiratory function ex-vivo was unchanged after both conditions. Peripheral O2-diffusion constraints and/or an impaired O2-delivery/O2-utilization coupling might be the main bottleneck to oxidative function in vivo after BR. Hypoxia may attenuate the impairment of muscle oxidative function observed after BR.
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- Šket, R., et al.
(författare)
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Intestinal metagenomes and metabolomes in healthy young males : Inactivity and hypoxia generated negative physiological symptoms precede microbial dysbiosis
- 2018
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Ingår i: Frontiers in Physiology. - : Frontiers Media S.A.. - 1664-042X. ; 9:Mars
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Tidskriftsartikel (refereegranskat)abstract
- We explored the metagenomic, metabolomic and trace metal makeup of intestinal microbiota and environment in healthy male participants during the run-in (5 day) and the following three 21-day interventions: normoxic bedrest (NBR), hypoxic bedrest (HBR) and hypoxic ambulation (HAmb) which were carried out within a controlled laboratory environment (circadian rhythm, fluid and dietary intakes, microbial bioburden, oxygen level, exercise). The fraction of inspired O2 (FiO2) and partial pressure of inspiredO2 (PiO2) were 0.209 and 133.1 ± 0.3 mmHg for the NBR and 0.141 ± 0.004 and 90.0 ± 0.4 mmHg (~4,000 m simulated altitude) for HBR and HAmb interventions, respectively. Shotgun metagenomes were analyzed at various taxonomic and functional levels, 1H-and 13C-metabolomes were processed using standard quantitative and human expert approaches, whereas metals were assessed using X-ray fluorescence spectrometry. Inactivity and hypoxia resulted in a significant increase in the genus Bacteroides in HBR, in genes coding for proteins involved in iron acquisition and metabolism, cell wall, capsule, virulence, defense and mucin degradation, such as beta-galactosidase (EC3.2.1.23), α-L-fucosidase (EC3.2.1.51), Sialidase (EC3.2.1.18), and α-N-acetylglucosaminidase (EC3.2.1.50). In contrast, the microbial metabolomes, intestinal element and metal profiles, the diversity of bacterial, archaeal and fungal microbial communities were not significantly affected. The observed progressive decrease in defecation frequency and concomitant increase in the electrical conductivity (EC) preceded or took place in absence of significant changes at the taxonomic, functional gene, metabolome and intestinal metal profile levels. The fact that the genus Bacteroides and proteins involved in iron acquisition and metabolism, cell wall, capsule, virulence and mucin degradation were enriched at the end of HBR suggest that both constipation and EC decreased intestinal metal availability leading to modified expression of co-regulated genes in Bacteroides genomes. Bayesian network analysis was used to derive the first hierarchical model of initial inactivity mediated deconditioning steps over time. The PlanHab wash-out period corresponded to a profound life-style change (i.e., reintroduction of exercise) that resulted in stepwise amelioration of the negative physiological symptoms, indicating that exercise apparently prevented the crosstalk between the microbial physiology, mucin degradation and proinflammatory immune activities in the host.
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- Strewe, C., et al.
(författare)
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PlanHab Study : Consequences of combined normobaric hypoxia and bed rest on adenosine kinetics
- 2018
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Adenosine plays a role in the energy supply of cells and provokes differential, hormone-like functions in circulating cells and various tissues. Its release is importantly regulated by oxygen tension. This renders adenosine and its kinetics interesting to investigate in humans subjected to low oxygen conditions. Especially for space exploration scenarios, hypoxic conditions - together with reduced gravity - represent two foreseen living conditions when planning manned long-duration space missions or planetary habitats. The PlanHab study investigated microgravity through inactivity in bed rest and normobaric hypoxia to examine their independent or combined effect on adenosine and its kinetics. Healthy male subjects (n = 14) completed three 21-day interventions: hypoxic bed rest (HBR); hypoxic ambulatory confinement (HAMB); normoxic bed rest (NBR). The interventions were separated by 4 months. Our hypothesis of a hypoxia-triggered increase in adenosine was confirmed in HAMB but unexpectedly also in NBR. However, the highest adenosine levels were noted following HBR. Furthermore, the percentage of hemolysis was elevated in HBR whereas endothelial integrity markers stayed low in all three interventions. In summary, these data suggest that neocytolysis accounts for these effects while we could reduce evidence for microcirculatory changes.
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