Effect of acute hypoxia on the time course change in flow‐mediated dilation: effect of sympathetic nerve activity (708.4)
Bibliographic record
Abstract
Endothelium‐dependent flow‐mediated dilation (FMD) is impaired during exposure to high altitude. Although the time course and mechanism(s) governing this impairment are undefined, hypoxic‐induced elevations in sympathetic outflow may attenuate FMD. We examined the hypothesis that acute exposure to normobaric hypoxia would lead to reductions in FMD that could be reversed via adrenergic blockade. In a placebo‐controlled crossover experiment, brachial FMD, arterial oxygen saturation, blood pressure and heart rate (HR) were assessed in 11 healthy participants (aged 32±7 y) in normobaric normoxia and following 60 min, 210 min and 330 min of normobaric hypoxia (FIO 2 =0.11). At 210 min, participants ingested an α 1 ‐adrenoreceptor blocker (Prazosin; 1 mg/20 kg body mass) or an identical placebo. Compared to normoxic baseline, FMD was reduced following 60 min, 210, and 330 min of hypoxia by 1.6 ± 0.2% (relative change 28%), 2.5 ± 0.1% and 2.8 ± 0.2% (36%), respectively (P蠄0.003). Following α 1 ‐blockade, FMD and HR at 330 min were 5 ± 2 beats∙min ‐1 and 1.8 ± 1.4% (35%) higher compared with the placebo trial (P蠄0.03). In summary, sustained reductions in FMD occur within 60 min of exposure to normobaric hypoxia and are largely mediated via the α 1 ‐adrenoceptor pathway.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".