Phenotype‐Specific Permeability Transition Pore Regulation in Rat Skeletal Muscle
Bibliographic record
Abstract
The aim of this study was to determine whether the susceptibility of mitochondria to opening of the permeability transition pore (PTP) varies according to muscle phenotype represented by the soleus (SOL: 95% type I fibers) and superficial white gastrocnemius (WG: 92% type IIb fibers). Sensitivity to Ca 2+ ‐induced PTP opening was determined with a novel approach using permeabilized myofibers devoid of their contractile apparatus (phantom fibers). Ca 2+ uptake in this preparation is specific to mitochondria and calcium retention capacity (CRC) is a good indicator of PTP sensitivity. Mitochondrial volume density was ~ 2 fold greater in SOL vs. WG, as judged by respiratory capacity per mg fiber weight and activity of the marker enzyme citrate synthase (CS). CRC values were 2.2 fold lower in phantom fibers from SOL compared to WG when expressed per unit of CS (CRC: 36.6±9.9 vs. 81.0±26.2 pmol Ca 2+ /mIU CS; p<0,001; n=4), indicating a pronounced vulnerability to PTP opening in type I vs. IIb fibers . A similar phenomenon was also observed in isolated mitochondria (CRC: <83 and 121 ± 60 nmol Ca 2+ /mg prot. in SOL and WG). This phenomenon was partly due to a 2‐fold increase in endogenous matrix Ca 2+ levels in mitochondria from SOL compared to WG, but not to enhanced ROS production. Expression of the PTP regulatory protein cyclophilin‐D was similar in mitochondria from both muscles. However, expression of ANT, a protein reported to be involved in pore formation and which contributes to Ca 2+ ‐sensitivity of the PTP, was significantly 2.3 fold higher in SOL compared to WG. The present study provides evidence that regulation of the PTP varies according to the phenotype of muscle fibers , which may impact on muscle cell death under conditions of stress. Funded by NSERC .
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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".