Plasticity of aged skeletal muscle: chronic contractile activity‐induced adaptations in muscle and mitochondrial function
Bibliographic record
Abstract
The intent of the present study was to investigate the adaptive potential of skeletal muscle, as well as subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria in young (6 mo) and senescent (36 mo) animals in response to a standard regimen of chronic contractile activity (CCA). The TA and EDL muscles of 6 and 36 mo F344XBN rats were chronically stimulated (10 Hz, 3 h/day, 7 days) to induce CCA. The contralateral limb served as a non‐stimulated control. Subsequent to CCA, acute stimulation (1 Hz, 5 min) of the TA muscle in situ revealed greater fatigue resistance in both 6 and 36 mo animals. However, the improvement in endurance was 50% greater in the young, compared to the old animals. The CCA‐mediated increase in Hsp70 was also greater in the young animals. The expression of the longevity protein SIRT1 was increased 40–50% with CCA in both age groups. CCA also induced similar 30% elevations in COX enzyme activity in young and old animals. This may be due to the CCA‐elicited increases in mitochondrial biogenesis regulatory proteins PGC‐1α and Tfam that were also comparable (40–70%) between groups. CCA reduced mitochondrial ROS production by 40–80% in both age groups, whereas mitochondrial VO 2 in the presence of succinate was increased with CCA only in the 6 mo group. Thus, muscle and mitochondria from senescent animals readily adapt to CCA, however the magnitude of the changes are less compared to young animals.
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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".