Evolved changes in reflex control of the cardiovascular system in deer mice native to high altitude
Bibliographic record
Abstract
The cold and hypoxic conditions at high altitude place high demands on the cardiovascular system to sustain circulatory O2 transport. High-altitude natives have evolved to overcome cold hypoxia, but the cardiovascular mechanisms involved remain poorly understood in most taxa. Here, we investigated the evolved changes in reflex control of cardiovascular function in deer mice (Peromyscus maniculatus) native to high altitude. High- and low-altitude populations of deer mice were each bred in captivity and then chronically acclimated to warm normoxia (25°C, ∼20 kPa O2) or cold hypoxia (5°C, 12 kPa O2) for 6-8 weeks. Cardiovascular function was measured in vivo using physiological telemeters, complemented by wire myography to examine vascular function ex vivo. High-altitude mice acclimated to cold hypoxia exhibited greater heart rates and were better able to maintain blood pressure in moderate and severe hypoxia, in association with less pronounced depression of metabolism and body temperature. High-altitude mice also exhibited greater baroreflex sensitivity than low-altitude mice across acclimation environments, as reflected by greater changes in heart rate and smaller changes in arterial blood pressure during pharmacological manipulations. Mesenteric arteries from each population exhibited similar ex vivo smooth muscle contractions in response to phenylephrine (α1-adrenoceptor agonist), and similar endothelium-dependent relaxation in response to acetylcholine, suggesting that evolved changes in the baroreflex arise from adjustments in autonomic control of the heart and/or other resistance vessels. These evolved changes in cardiovascular function and reflex control may be valuable for supporting high metabolic rates in the cold and hypoxic environment at high altitude.
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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) | 0.001 | 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".