Ultrastructural and immunocharacterization of undifferentiated myocardial cells in the developing mouse heart
Bibliographic record
Abstract
The recent discovery of several myogenic cardiac progenitor cells in the post-natal heart suggests that some myocardial cells may remain undifferentiated during embryonic development. In this study, we examined the subcellular characteristics of the embryonic (E) mouse ventricular myocardial cells using transmission electron microscopy (TEM). At the ultrastructural level, we identified three different cell populations within the myocardial layer of the E11.5 heart. These cells were designated as undifferentiated cells (43 +/- 6%), moderately differentiated cells (43 +/- 2%) and mature cardiomyocytes (14 +/- 4%). Undifferentiated cells contained a large nucleus and sparse cytoplasm with no myofibrillar bundles. Moderately differentiated cells contained randomly arranged myofilaments in the cytoplasm. In contrast, mature cardiomyocytes contained well-developed sarcomere structures. We also confirmed the presence of similar undifferentiated cells albeit at low levels in the E16.5 ( approximately 20%) and E18.5 ( approximately 7%) myocardium. Further we used immunogold labeling technique to test whether these distinct cell populations were also positive for markers such as Nkx2.5, ISL1 and ANF. A preponderance of anti-Nkx2.5 label was found in the undifferentiated and moderately differentiated cell types. Anti-ANF label was found only in the cytoplasmic compartment of moderately differentiated and mature myocardial cells. All of the undifferentiated cells were negative for anti-ANF labeling. We did not find immuno-gold labeling with ISL1 in any of the three myocardial cell types. Based on these results, we suggest that embryonic myocardial cell differentiation is a gradual process and undifferentiated cells expressing Nkx2.5 in post-chamber myocardium may represent a progenitor cell population while cells expressing Nkx2.5 and ANF represent differentiating myocytes.
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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) | 0.000 | 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 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".