Taurine efflux counters the hydrodynamic impact of anaerobic metabolism to protect cardiorespiratory function under acute thermal stress in brook char (<i>Salvelinus fontinalis</i>)
Bibliographic record
Abstract
Upper thermal tolerance may be limited by convective oxygen transport in fish, but the mechanisms constraining heart function remain elusive. The activation of anaerobic metabolism imposes an osmotic stress on cardiomyocytes at high temperatures that must be countered to prevent swelling and cardiac dysfunction. We tested the hypothesis that cardiac taurine efflux is required to counter the osmotic impact of anaerobic end product accumulation in brook char, Salvelinus fontinalis. Fish were fed a diet enriched in β-alanine, a competitive inhibitor of the taurine transporter, to induce taurine deficiency and inhibit transporter function. In vivo, stroke volume increased by 60% and cardiac output doubled in control fish during a 2°C h-1 thermal ramp. Stroke volume was temperature insensitive in taurine-deficient (TD) fish, so cardiac output was 30% lower at high temperatures. The thermal sensitivity of aerobic metabolism did not differ, and lactate accumulated to a similar degree in the two diet treatment groups, indicating that taurine deficiency does not impact energy metabolism. Heart taurine efflux was absent and ventricular muscle osmolality was 40 mOsmol kg-1 higher in TD brook char following thermal stress. Swelling and decreased ventricular compliance likely impair diastolic filling to constrain stroke volume in TD fish. The adrenaline sensitivity of cardiac contractility and the regulation of intracellular pH in the brain and liver were also impacted in TD brook char. Taurine efflux appears necessary to counteract the hydrodynamic impact of activating anaerobic metabolism and this process may limit heart function under acute thermal stress.
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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".