The Dynamics of Scavenger Receptor BI Expression During Luteinization.
Notice bibliographique
Résumé
During luteinization, bulk cholesterol uptake to ovarian cells from blood high-density lipoproteins (HDL) is achieved by Scavenger Receptor BI (SR-BI). This is believed to be the major source of substrate for steroidogenesis. In the pig, we have shown weak expression of SR-BI in granulosa cells prior to ovulation, while robust in the corpus luteum (CL), where the protein localizes to the plasma membrane. Little is known about other species, indeed mice with SR-BI null mutation display estrous cycles and form CLs. We studied the expression of SR-BI during estrous cycle, the effects of uncoupling of ovulation and luteinization and the ovarian consequences of SR-BI knockout. Ovarian morphology was examined by light microscopy in HE-stained sections, SR-BI protein expression by immunofluorescence and progesterone determined by RIA. In Experiment 1, ovaries were collected from mature female WT mice at each stage of the estrous cycle (n=3 per stage). Expression of SR-BI was weak and diffuse in granulosa cells of developing follicles but became strong and localized to the cell membrane in CLs. In Experiment 2, follicular development was induced in immature female mice with PMSG and hCG. Animals received, 6 mg/kg of meloxicam (a cyclooxygenase inhibitor; MEL; n=3) or 10 mg of mifepristone (a progesterone receptor antagonist; RU; n=3) to block ovulation or vehicle only (n=3) and ovaries were collected 24 h after the hCG injection. Ovaries of animals treated with MEL or RU showed non-ovulated follicles, containing entrapped oocytes in unexpanded cumulus complexes. Membrane SR-BI expression was present throughout, but most intensely in the peripheral regions of the unruptured follicles. In Experiment 3, follicular development of mature WT and SR-BI-/- mice was stimulated by PMSG and hCG and animals were divided to receive vehicle or a combination of 20 mg/kg of mevinolin (an HMG-CoA reductase inhibitor; MEV) and 100 mg/kg of chloroquinone (an inhibitor of lysosomal processing of LDL; CHLORO) in a 2x2 factorial design (n=3 per group). At 18 h after hCG injection, approximately 6 h after expected ovulation, ovaries from SR-BI-/- mice presented small, luteal-like structures and large follicles with a thick, luteal-like layer of theca cells. Ovaries from MEV-CHLORO-treated, SR-BI-/- mice also displayed follicular cysts with blood filled cavities. Plasma progesterone concentrations were decreased in SR-BI-/- mice and further decreased by MEV-CHLORO treatment. It was concluded that (1) membrane expression of SR-BI increases in response to luteinization, (2) this event is not dependent on ovulation, (3) CL can be formed in the absence of SR-BI and (4) blocking cholesterol de novo synthesis and uptake from LDL and HDL sources leads to the formation of follicular cysts and reduces, but does not impair, ovarian steroidogenesis. Supported by CIHR grant FRN 11018 to BDM. MB is on leave from University of São Paulo and is supported by FAPESP (grant 06/52960-4).
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».