The cellular force‐frequency response in ventricular myocytes from the varanid lizard, <i>Varanus exanthematicus</i>
Bibliographic record
Abstract
To investigate the cellular mechanisms underlying the negative force‐frequency relationship in the ventricle of the varanid lizard, we measured sarcomere and cell shortening, intracellular Ca 2+ ([Ca 2+ ] i ), action potentials (APs) and K + currents in isolated ventricular myocytes. Experiments were conducted between 0.2–1.0 Hz, which spans the physiological range of heart rates at 20–22°C for this species. As frequency increased, diastolic length, percent change in sarcomere length and relaxation time decreased significantly. Shortening velocity was unchanged. The rate of rise of [Ca 2+ ] i increased, [Ca 2+ ] i transient amplitude decreased, and diastolic [Ca 2+ ] i increased. The first order time constant of the [Ca 2+ ] i transient decay decreased at higher frequencies, indicating frequency dependent acceleration of relaxation, then leveled out and did not change above 0.5 Hz. The AP rate of rise was unaffected, but the AP duration (APD) decreased with increasing frequency. Peak depolarization was only significantly decreased at 1.0 Hz. The decrease in APD was not due to changes in I Kr or I to . Our results suggest that a negative FFR in varanid lizard ventricle is caused by decreased amplitude of the [Ca 2+ ] i transient with an increase in diastolic [Ca 2+ ] i , leading to incomplete relaxation between beats at high frequencies. This coincides with shortened action potential duration (APD) at higher frequencies.
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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".