Hypoxic depression of circadian rhythms in adult rats
Bibliographic record
Abstract
Because the circadian rhythms of oxygen consumption (VO(2)) and body temperature (T(b)) could be contributed to by differences in thermogenesis and because hypoxia depresses thermogenesis in its various forms, we tested the hypothesis that hypoxia blunts the normal daily oscillations in VO(2) and T(b). Adult rats were instrumented for measurements of T(b) and activity by telemetry; VO(2) was measured by an open-flow method. Animals were exposed to normoxia (21% O(2)), hypoxia (10.5% O(2)), and normoxia again, each 1 wk in duration, in either a 12:12-h light-dark cycle ("synchronized") or constant light ("free running"). In this latter case, the period of the cycle was approximately 25 h. In synchronized conditions, hypoxia almost eliminated the T(b) circadian oscillation, because of the blunting of the T(b) rise during the dark phase. On return to normoxia, T(b) rapidly increased toward the maximum normoxic values, and the normal cycle was then reestablished. In hypoxia, the amplitude of the activity and VO(2) oscillations averaged, respectively, 37 and 56% of normoxia. In free-running conditions, on return to normoxia the rhythm was reestablished at the expected phase of the cycle. Hence, the action of hypoxia was not on the clock itself but probably at the hypothalamic centers of thermoregulation. Hyperoxia (40% O(2)) or hypercapnia (3% CO(2)) had no significant effects on circadian oscillations, indicating that the effects of hypoxia did not reflect an undifferentiated response to changes in environmental gases. Modifications of the metabolism and T(b) rhythms during hypoxia could be at the origin of sleep disturbances in cardiorespiratory patients and 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 | 0.000 |
| 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".