Myosin phosphorylation‐mediated potentiation does not alter the economy of work performed in fast skeletal muscles
Bibliographic record
Abstract
The physiological role of myosin regulatory light chain (RLC) phosphorylation in fast skeletal muscle is unclear, as the resultant potentiation of contractile function comes with an undetermined energetic cost. We conducted in vitro experiments (25°C) to quantify contractile economy (i.e. energy cost/work performed) in potentiated extensor digitorum longus (EDL) muscles from wildtype and myosin light chain kinase knockout (skMLCK −/− ) mice. Economy values were calculated as the ratio of total work performed to high‐energy phosphate consumption (HEPC) during a period of repeated isovelocity contractions that followed a potentiating stimulus (PS). The PS enhanced contractile parameters (concentric force and work) in both genotypes, although the effect was significantly greater in wildtype (1.38 ± 0.03 and 1.51 ± 0.03) vs. skMLCK −/− (1.10 ± 0.04 and 1.10 ± 0.05) muscles ( P < 0.05, n = 8 for all data). During the experimental period of repetitive stimulation in the potentiated state, wildtype muscles performed ~58% more total work than skMLCK −/− muscles (94.05 ± 3.80 vs. 59.55 ± 4.10 J•kg −1 ; P < 0.001) without a statistical increase in HEPC (19.03 ± 3.37 vs. 16.02 ± 3.41 μmol~P; P = 0.27) or genotype difference in economy (5.74 ± 0.67 vs. 4.61 ± 0.71 J•kg −1 μmol~P −1 ; P = 0.27). Importantly, when relative genotype differences were analyzed, the quantity of total work performed was ~3 fold greater than the increase in HEPC for wildtype muscles. Our results support the idea that myosin RLC phosphorylation‐mediated potentiation is a mechanism capable of augmenting sustained contractile function without significantly increasing energetic cost or decreasing economy. Support or Funding Information Natural Sciences & Engineering Research Council of Canada (NSERC): Discovery Grant (R. Vandenboom)
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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 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".