Diminished contraction‐induced intracellular signaling in aged fast‐twitch skeletal muscle with low and high mitochondrial content
Bibliographic record
Abstract
Reduced plasticity of senescent skeletal muscle may be due to an attenuated signaling response to contractions. The intent of the present study was to determine whether aging affects signaling pathways involved in mitochondrial biogenesis in response to a single bout of contractile activity (CA). Acute stimulation (1 Hz, 5 min) of the tibialis anterior (TA) resulted in a significantly greater rate of fatigue in 36 month (mo) relative to 6 mo F344XBN rats. To investigate fiber type‐specific signaling, the TA was sectioned into red (RTA) and white (WTA) portions, possessing 2.5‐fold differences in mitochondrial content. The CA‐mediated activation of p38, MKK3/6, CaMKII and AMPK signaling was assessed. In general, CA‐evoked kinase phosphorylation was greater in RTA compared to WTA in both age groups. p38 activation was similar in RTA from 6 and 36 mo groups, however in WTA, the response was 2‐fold greater in muscle from 6, relative to 36 mo animals. CA also increased MKK3/6 phosphorylation, the upstream regulator of p38, however the magnitude was 70–80% higher in RTA and WTA of 6, compared to 36 mo rats. Contraction‐induced CaMKII phosphorylation was 40% higher in both fiber types in muscle from 6 relative to 36 mo animals. AMPK was not responsive to 1 Hz CA at either age. Thus, CA‐induced signaling to mitochondrial biogenesis is reduced in aging muscle, but the extent of the attenuation depends in part on mitochondrial content.
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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".