Effects of Insulin-Like Growth Factor I on Steroidogenic Enzyme Expression Levels in Mouse Leydig Cells
Bibliographic record
Abstract
The role of IGF-I in Leydig cell maturation was studied by evaluation of: 1) steady state levels for nine mRNA species expressed specifically in Leydig cells of 35- and 50-d-old IGF-I-null mice and wild-type controls; 2) protein levels for 17 alpha-hydroxylase/C17-20 lyase, cholesterol side-chain cleavage, and type I 5 alpha-reductase (5 alpha R-1) in Leydig cells by immunocytochemistry; and 3) serum testosterone (T) and testicular interstitial fluid IGF-I levels. Expression levels of all mRNA species associated with T biosynthesis were lower in the absence of IGF-I stimulation. In contrast, androgen-metabolizing enzyme mRNA species had either normal (3 alpha-hydroxysteroid dehydrogenase) or higher expression (5 alpha R-1) levels in IGF-I-null mice (P < 0.05) relative to wild-type controls. None of the mRNA species studied changed developmentally in the mutant, whereas there were increases or decreases between d 35 and 50 in normal controls. Parallel trends were observed for average Leydig cell 5 alpha R-1 immunostaining intensity. T levels in mutants were initially higher during d 14-21, equivalent to normal on d 28, and then failed to increase pubertally, remaining at 30% of control levels (P < 0.01) in 90-d-old adult animals. In normal wild-type mice, interstitial fluid and plasma IGF-I levels were highest (P < 0.05) on d 24, indicating that the action of this growth factor on the testis peaks during pubertal development. These results show that in the absence of IGF-I, there is a failure of adult Leydig cells to mature, and that the reduced capacity for T production is caused by disproportionate expression of T biosynthetic and metabolizing enzymes.
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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) | 0.001 | 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".