Influence of Estrogen on RLC Phosphorylation and Posttetanic Potentiation of Mouse Muscles with and without Skeletal Myosin Light Chain Kinase
Bibliographic record
Abstract
Estrogen may influence myosin regulatory light chain (RLC) phosphorylation and posttetanic potentiation (PTP) in mouse fast twitch muscle; although the signalling pathway for this effect is unknown. The purpose of this study was to test the hypothesis that previously reported estrogen effects on RLC phosphorylation and PTP are mediated via skeletal myosin light chain kinase (skMLCK). To this end, extensor digitorum longus (EDL) muscles from female wildtype and skMLCK deficient (skMLCK-/-) mice were divided into four groups: ovariectomized (OVX) with estrogen (E+), ovariectomized without estrogen (E-), sham surgery (Sham) and intact baseline (BL). At 8 weeks of age, mice in the OVX groups were ovariectomized followed by pellet implantation at 9 weeks of age with either a 0.1 mg of 17β-Estradiol or implantation of a placebo pellet (E+ and E- respectively); sham surgeries were also performed at this time point for both genotypes. Two weeks later EDL muscles were isolated and suspended in vitro (25° C) for determination of RLC phosphorylation and PTP, except for BL groups which began contractile experiments at 9 weeks. Our results showed that RLC phosphorylation measured in muscles frozen immediately after a potentiating stimulus was not different across conditions within either genotype although values for wildtype muscles were significantly (P<0.05) greater than skMLCK-/- muscles. Consistent with these findings, the ratio of concentric twitch force (post PS / pre PS) for wildtype and skMLCK-/- muscles was similar between E+ and E+ groups although values for wildtype were greater than skMLCK-/- muscles (all data P < 0.05). However, we were unable to directly test our hypothesis as a result of unaltered estradiol levels following OVX. The inability to validate estrogen’s beneficial influence on muscle strength and contractibility in this model could be a direct result of interference with further development and growth during estrogen supplementation. Future studies should note the importance of both estrous cycles and further growth of adult mice when working with ovarian hormones. Both of these factors were likely causes of our atypical findings.
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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".