Fiber-type differences in muscle mitochondrial profiles
Bibliographic record
Abstract
Although striated muscles differ in mitochondrial content, the extent of fiber-type specific mitochondrial specializations is not well known. To address this issue, we compared mitochondrial structural and functional properties in red muscle (RM), white muscle (WM), and cardiac muscle of rainbow trout. Overall preservation of the basic relationships between oxidative phosphorylation complexes among fiber types was confirmed by kinetic analyses, immunoblotting of native holoproteins, and spectroscopic measurements of cytochrome content. Fiber-type differences in mitochondrial properties were apparent when parameters were expressed per milligram mitochondrial protein. However, the differences diminished when expressed relative to cytochrome oxidase (COX), possibly a more meaningful denominator than mitochondrial protein. Expressed relative to COX, there were no differences in oxidative phosphorylation enzyme activities, pyruvate-based respiratory rates, H2O2 production, or state 4 proton leak respiration. These data suggest most mitochondrial qualitative properties are conserved across fiber types. However, there remained modest differences ( approximately 50%) in stoichiometries of selected enzymes of the Krebs cycle, beta-oxidation, and antioxidant enzymes. There were clear differences in membrane fluidity (RM > cardiac, WM) and proton conductance (H+/min/mV/U COX: WM > RM > cardiac). The pronounced differences in mitochondrial content between fiber types could be attributed to a combination of differences in myonuclear domain and modest effects on the expression of nuclear- and mitochondrially encoded respiratory genes. Collectively, these studies suggest constitutive pathways that transcend fiber types are primarily responsible for determining most quantitative and qualitative properties of mitochondria.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".