Retention of Pax3 Expression in Satellite Cells of Muscle Spindles
Bibliographic record
Abstract
Intrafusal fibers within muscle spindles retain features characteristic of immaturity, unlike the larger and more numerous extrafusal fibers constituting the bulk of skeletal muscle. Satellite cells (SCs), myogenic progenitors, are detected on the surfaces of both intrafusal and extrafusal fibers, but little is known of spindle SCs. We have recently demonstrated that, like their extrafusal counterparts, SCs in muscle spindles of posthatch chickens express paired box transcription factor 7 (Pax7) protein. During vertebrate embryogenesis, myogenic progenitors express both Pax7 and Pax3 proteins. In postnatal mice, Pax3 appears in rare SC subsets, whereas Pax7 is expressed by all SCs within extrafusal fibers. Here we test the hypothesis that Pax3 protein maintains localized expression within SCs of muscle spindles. Immunohistochemical techniques were used to identify SCs by their Pax7 expression within anterior latissimus dorsi muscle excised from posthatch chickens of various ages. A greater percentage of SCs express Pax3 within intrafusal than extrafusal fibers at each age, and the proportion of SCs expressing Pax3 declines with aging. This is the first study to localize Pax3 expression in posthatch avian muscle and within SCs of muscle spindles. We suggest that Pax3-positive SCs are involved in fiber maintenance.
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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) | 0.000 | 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) | 0.000 | 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".