Effect of age on progesterone receptor expression, and osteoprogenitor proliferation and differentiation in female rat vertebral cell populations
Bibliographic record
Abstract
In the present investigation, we evaluated whether the capacity for proliferation and differentiation of progesterone (Prog)-dependent osteoprogenitors in the female rat skeleton is related to the level of Prog receptors (PRs) and/or the level of circulating estrogen. We confirmed that in rats, estrogen levels at 18 months of age are higher than those at 3 months, and higher again in rats of 22.5, 25.5, and 26 months of age. Prog levels in rats of ages between 18 and 25.5 months were lower than those at 26 and 3 months of age. PR-A levels were tenfold higher than those of PR-B in cell populations where PR-B was detectable; PR-B receptors were not detectable in all cell populations. In populations derived from 22.5 to 26 months old rats, the basal levels of PR-A were higher than those derived from 3 and 18 months old rats by five- and twofold respectively. Prog treatment enhanced PR-A expression in animals of all ages. Estrogen enhanced the effect of Prog on PR-A expression in cell populations from the 3 and 18 months old rats, but had no effect on PR-A expression in cell populations from 22.5, 25.5, and 26 months old rats. This might be related to the high basal expression of PR in 22.5-26 months old rats (the 'persistent estrous' phase). Our results also confirm our previous observation that in rats, the number of Prog- and dexamethasone (Dex)- dependent osteoprogenitors, and the effect of estrogen on the response to Prog do not decrease with age. In conclusion, we have shown that the basal level of PR-A was increased in old rats, and that this correlated with increased serum estrogen levels, but not with the number of detectable Prog-dependent osteoprogenitors. We also found that Prog upregulates the expression of its own receptors and that estrogen enhances this in young rats but not in rats over 22.5 months of age, in which estrogen levels are elevated.
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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".