Ontogenetic Changes in the Reptilian Heart: An Investigation of Cardiomyocyte Proliferation and Hyperplasia in the Leopard Gecko ( <i>Eublepharis macularius</i> )
Bibliographic record
Abstract
Relative rates of cardiomyocyte proliferation vary among and within species. Whereas embryonic and fetal mammals demonstrate robust rates of cardiomyocyte proliferation, this capacity sharply declines within days following birth. Continued growth of the heart in mammals primarily involves cardiomyocyte hypertrophy. In contrast, cardiomyocytes in some teleost fish and salamanders retain a relative high proliferative capacity, even as adults. In these species, continued growth involves increasing the relative population of cardiomyocytes (cardiomyocyte hyperplasia). Previously, we have demonstrated that subadult leopard geckos ( Eublepharis macularius , hereafter ‘geckos’) demonstrate relatively high rates of cardiomyocyte proliferation. As subadult geckos are actively undergoing somatic growth, we sought to determine if the rates of cardiomyocyte proliferation changed in adult geckos. We hypothesized that the elevated rate of cardiomyocyte proliferation observed in subadults is a function of ontogeny, and contributes to overall heart growth through cardiomyocyte hyperplasia. To document cardiomyocyte proliferation, we performed double immunofluorescence on heart ventricles from subadult and adult geckos. To identify proliferating cardiomyocytes we immunostained for the motor protein marker myosin heavy chain with either the DNA synthesis (S) phase marker proliferating cell nuclear antigen or the mitotic (M) phase marker phosphorylated histone H3. We found that there were significantly fewer cardiomyocytes in S phase (~0.1%) and M phase (~0%) in adult geckos as compared to subadult geckos (~11% and ~0.5%, respectively). This decline in proliferation likely reflects a shift from tissue growth to maintenance and remodeling. We also determined that the ventricle of adult geckos had more than twice as many cardiac cells when compared to subadult geckos. These data indicate that, similar to zebrafish (and unlike mammals), ontogenetic growth of the gecko heart involves continued cardiomyocyte proliferation and hyperplasia.
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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 | 0.001 | 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".