Effect of simulated microgravity on mesenteric blood flow during orthostatic challenge
Bibliographic record
Abstract
Astronauts, particularly females, suffer from post‐flight orthostatic hypotension. We proposed that microgravity impairs reflex control of the splanchnic circulation during an orthostatic challenge. Female rats were trained to mount a 45% incline (Head up tilt, HUT). They were then implanted with transit time flow probes on the superior mesenteric artery (SMA) and vein (SMV). After 7 days recovery, mesenteric arterial and venous blood flow was measured during HUT. After hindlimb unloading (HU) for 14 days, the responses to HUT were then retested. Baseline SMA and SMV blood flows were 13.7±3.5 and 9.7±0.1mL/min respectively. During HUT these fell (At 5 sec: Δ SMA flow = −7mL/min, Δ SMV flow = −3mL/min; At 10 sec: Δ SMA flow = −4mL/min, Δ SMV flow = −3mL/min). There was thus an immediate mesenteric arterial constriction, and a net loss of ~4mL/min blood from the mesenteric vascular bed. After 14 days HU, there were no such changes in blood flow during HUT i.e. there was no reflex mesenteric arterial constriction and no mobilization of venous blood. We propose microgravity impairs splanchnic control of cardiac preload and afterload during HUT, and contributes to orthostatic hypotension. Canadian Space Agency.
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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) | 0.001 | 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".