Hypothermia increases the gain of excitation-contraction coupling in guinea pig ventricular myocytes
Bibliographic record
Abstract
Components of excitation-contraction (EC)-coupling were compared at 37 degrees C and 22 degrees C to determine whether hypothermia altered the gain of EC coupling in guinea pig ventricular myocytes. Ca(2+) concentration (fura-2) and cell shortening (edge detector) were measured simultaneously. Hypothermia increased fractional shortening (8.3+/-1.7 vs. 2.6+/-0.3% at 37 degrees C), Ca(2+) transients (157+/-33 vs. 35+/-5 nM at 37 degrees C), and diastolic Ca(2+) (100+/-9 vs. 60+/-6 nM at 37 degrees C) in field-stimulated myocytes (2 Hz). In experiments with high-resistance microelectrodes, the increase in contractions and Ca(2+) transients was accompanied by a twofold increase in action potential duration (APD). When voltage-clamp steps eliminated changes in APD, cooling still increased contractions and Ca(2+) transients. Hypothermia increased sarcoplasmic reticulum (SR) Ca(2+) stores (83+/-17 at 37 degrees C to 212+/-50 nM, assessed with caffeine) and increased fractional SR Ca(2+) release twofold. In contrast, peak Ca(2+) current was much smaller at 22 degrees C than at 37 degrees C (1.3+/-0.4 and 3.5+/-0.7 pA/pF, respectively). In cells dialyzed with sodium-free pipette solutions to inhibit Ca(2+) influx via reverse-mode Na(+)/Ca(2+) exchange, hypothermia still increased contractions, Ca(2+) transients, SR stores, and fractional release but decreased the amplitude of Ca(2+) current. The rate of SR Ca(2+) release per unit Ca(2+) current, a measure of EC-coupling gain, was increased sixfold by hypothermia. This increase in gain occurred regardless of whether cells were dialyzed with sodium-free solutions. Thus an increase in EC-coupling gain contributes importantly to positive inotropic effects of hypothermia in the heart.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".