Effect of simulated microgravity on sympathetic outflow to the mesentery during an orthostatic challenge
Bibliographic record
Abstract
Female astronauts suffer from orthostatic hypotesion upon return to a normal gravitational field. Recent work from our laboratory has shown that female rats exposed to 2 weeks of simulated microgravity (hindlimb unloading; HU) also experience orthostatic hypotension during an active orthostatic challenge (head‐up tilt; HUT; i.e., volunatary mounting of a 45° slope). The simulated microgravity abolishes a reflex mesenteric vasoconstriction that occurs in response to HUT, in part due to a decreased sensitivity of mesenteric arteries to adrenergic stimulation. We examined if HU also attenuates sympathetic outflow to the mesentery induced by HUT. Virgin female rats were chronically instrumented with recording electrodes (Telemetry Research) on a nerve fiber branching from the coelic ganglion and innervating the mesentery, as well as a blood pressure transducer (DSI). Nerve activity, mean arterial pressure (MAP) and heart rate ( f H ) responses to HUT were measured prior to, immediately following and 3 h post‐HU. Compared to pre‐HU, HUT immediately following HU induced increased sympathetic outflow to the mesentery in both amplitude and frequency, whereas MAP and f H responses were similar (immediate and sustained increases). Thus, increased nerve activity compensated for deficient mesenteric vascular constriction. However, by 3 h post‐HU, the increased nerve activity was attenuated and the tachycardia less. We propose that an inability to maintain a compensatory increase in sympathetic outflow to the mesentery in face of an impaired end organ response to adrenergic stimulation contributes to orthostatic hypotesion in females following simulated microgravity. AHFMR
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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".