Metabolic rate and mitochondrial physiology adjustments in Arctic char (<i>Salvelinus alpinus</i>) during cyclic hypoxia
Bibliographic record
Abstract
Diel fluctuations of oxygen levels characterize cyclic hypoxia and pose a significant challenge to wild fish populations. Although recent research has been conducted on the effects of hypoxia and reoxygenation, mechanisms by which fish acclimatize to cyclic hypoxia remain unclear, especially in hypoxia-sensitive species. We hypothesized that acclimation to cyclic hypoxia requires a downregulation of aerobic metabolic rate and an upregulation of mitochondrial respiratory capacities to mitigate constraints on aerobic metabolism and the elevated risk of oxidative stress upon reoxygenation. We exposed Arctic char (Salvelinus alpinus) to 10 days of cyclic hypoxia and measured their metabolic rate and mitochondrial physiology to determine how they cope with fluctuating oxygen concentrations. We measured oxygen consumption as a proxy of metabolic rate and observed that Arctic char defend their standard metabolic rate but decrease their routine metabolic rate during hypoxic phases, presumably through the repression of spontaneous swimming activities. At the mitochondrial level, acute cyclic hypoxia increases oxygen consumption without ADP (CI-LEAK) in the liver and heart. Respiration in the presence of ADP (OXPHOS) temporarily increases in the liver and decreases in the heart. Cytochrome c oxidase oxygen affinity also increases at day 3 in the liver. However, no change occurs in the brain, which is likely primarily preserved through preferential perfusion (albeit not measured in this study). Finally, in vivo measurements of reactive oxygen species revealed the absence of an oxidative burst in mitochondria in the cyclic hypoxia group. Our study shows that Arctic char acclimatize to cyclic hypoxia through organ-specific mitochondrial adjustments.
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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".