Regulation of Inducible Nitric Oxide Synthase Expression in Bovine Granulosa Cells and Its Involvement in Follicular Dominance.
Bibliographic record
Abstract
Understanding the paracrine events that regulate fertility in the cow is necessary not only because of the agricultural importance of this species, but also its potential use as a model for humans. Nitric oxide (NO), a free-radical gas, has been implicated in follicular growth in rodents, but the cow is an intriguing enigma: NO is produced by bovine granulosa cells and is regulated by FSH, but the enzymes responsible are reported to be absent. Three genes encode NO synthase proteins, one of which - iNOS - is widely considered to be regulated by extracellular ligands. We hypothesize that granulosa cells express the gene encoding iNOS, and that the expression of this gene is under hormonal regulation. The objectives of the present study were to determine the abundance of iNOS mRNA in growing and non-growing follicles in cattle, to determine the regulation of iNOS expression by FSH and growth factors, and to determine the action of NOS in bovine granulosa cells. The two largest follicles on days 1 to 5 of the first follicular wave of the cycle were collected from each pair of ovaries from six cows. Messenger RNA encoding iNOS was detected in granulosa and theca cells of bovine follicles by real-time PCR. The granulosa cells of dominant follicles contained higher levels of mRNA for iNOS compared with subordinate follicles (P<0.01). The regulation of iNOS expression was evaluated in a serum-free granulosa cell culture system. FSH (P<0.05) and IGF1 (P<0.01) stimulated E2 secretion iNOS mRNA abundance in a dose-dependent manner. Moreover, both FGF2 and EGF (P<0.01) decreased iNOS expression and E2 secretion in FSH and in IGF1-treated cells. Owing to the parallel changes in estradiol secretion and iNOS mRNA, we assessed the role of estradiol in the regulation of iNOS mRNA; replacement of estrogen precursor with a non-aromatizable androgen (DHT) or the addition of an estrogen receptor antagonist inhibited FSH-stimulated iNOS mRNA abundance, and addition of E2 alone stimulated NO production in vitro. To assess the role of endogenous iNOS, cells were treated with an iNOS-selective inhibitor, which resulted in increased FasL mRNA levels (P<0.01), induction of caspase-3 activation (P<0.01) and an increase in the incidence of cell death (P<0.05). In conclusion, bovine graulosa cells express iNOS, and increased iNOS mRNA levels are associated with growth of the dominant follicle. Gonadotropic factors stimulate iNOS mRNA levels through increased E2 secretion, and physiological levels of NOS activity may contribute to growth and survival of granulosa cells. Supported by NSERC Canada and CNPq Brazil. (poster)
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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".