Acute regulation of erythropoietin via lower body negative pressure: Influence of sex and age
Bibliographic record
Abstract
The regulation of erythropoiesis via hemodynamic stimuli such as reduced central blood volume (CBV) remains uncertain in women and elderly individuals. This study assessed the acute effects of lower body negative pressure (LBNP) on key endocrine biomarkers regulating erythropoiesis, that is, erythropoietin (EPO) and copeptin, in young and older women and men (n = 87). Transthoracic echocardiography and hemodynamics were assessed throughout incremental LBNP levels for 1 hour, or until presyncope, with established methods. Venous blood samples were collected at baseline and immediately after termination of the orthostatic tolerance (OT) test for subsequent hormone analyses. The average age of young women and men (33.1 ± 6.0 vs. 29.5 ± 6.9 yr) and older women and men (63.8 ± 8.0 vs. 65.3 ± 8.9 yr) as well as their physical activity levels were matched within each age and sex group. CBV, as determined by right atrial volume, was reduced in all individuals at the end of the OT test (p < 0.001). The average OT time ranged from 50.1 to 58.1 min in all individuals. LBNP increased circulating EPO in young women (p = 0.023) but not in young men or older individuals. Copeptin was increased in all individuals with LBNP but was exclusively associated with EPO in men (r = 0.39, p = 0.013). The present study indicates that the acute hemodynamic regulation of EPO production is both sex- and age-dependent.
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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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".