The influence of estrogen on skeletal muscle myosin regulatory light chain phosphorylation, post-tetanic potentiation, work, and power in C57BL/6 mice
Bibliographic record
Abstract
Estrogen hormones are implicated in influencing skeletal muscle contractile function and specifically, the interactions between myosin and actin that facilitate contraction. Myosin regulatory light chain (RLC) phosphorylation (RLC-p) is highly associated with an increase in the percentage of myosin proteins strongly bound to actin during contractile activity. Myosin RLC-p is also highly associated with post-tetanic potentiation (PTP) i.e. the short-term increase in force observed following tetanic stimulation characteristic of fast-twitch skeletal muscle. The purpose of this study was to examine the influence of ovarian hormone deficiency and 17β-Estradiol (E2) replacement, on the PTP of concentric twitch force and myosin RLC-p of mouse fast twitch skeletal muscle. To this end, 4-month-old wildtype C57BL/6 mice were allocated to the ovariectomized (OVX), ovariectomized with E2 replacement (OVX+E), or sham-ovariectomized (SHAM) condition (n=8 mice). Extensor digitorum longus (EDL) muscles were surgically extracted and mounted for in vitro contractile experiments at 25° C involving the use of a brief potentiating stimulus (PS) to induce PTP. The PS, consisting of four equally spaced tetani (400Hz, 100ms) over 10.5s, significantly increased concentric twitch force and myosin RLC-p levels across condition groups. However, no significant differences in PTP, myosin RLC-p, or rates of force development and relaxation were observed between muscles of the OVX, OVX+E and SHAM conditions. A significant drop in relative tetanic force amongst the first and second tetanus within the PS was observed of muscles from OVX mice compared to that of OVX+E and SHAM mice. Specific force, calculated as the ratio of force to muscle PCSA, total work, peak work, and power production, were significantly increased following the PS across conditions, and were significantly less of muscles from OVX mice compared to OVX+E and SHAM, both prior to and following the PS. Data are contrary to the primary hypothesis that E2 influences myosin RLC-p and PTP in fast twitch skeletal muscle, though are suggestive of an influence of OVX and E2 on skeletal muscle quality.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".