Follicle selection in domestic ruminants
Notice bibliographique
Résumé
Ultrasound imaging has shown that cattle exhibit 2 or 3 waves of follicular development during an oestrous cycle.The waves consist of the contemporaneous appearance, about every 7 days, of a group of follicles > 5 mm in diameter.One follicle gradually becomes larger than the rest (i.e.dominant).There are several lines of evidence suggesting that the waves occur regularly under conditions of basal LH and FSH.(1) Cycles with 3 waves of follicular development are longer and have longer luteal phases than do cycles with 2 waves, indicating that the number of waves in a cycle is determined by the time of luteal regression.(2) Cycles with 4 or 5 waves of follicular development can occur when the luteal phase is artificially prolonged with exogenous progesterone.(3) Waves of follicular development occur during pregnancy.However, the secondary surge of FSH may be important in initiating new follicular recruitment after ovulation, since suppression of the secondary surge delays the first wave of follicular development.Follicles are functionally dominant (capable of ovulating after luteal regression) while they are still growing and early during their plateau in growth.Functional dominance is lost some time between the early and late plateau phases, while the follicle is still morphologically dominant (i.e. the largest follicle).The factors that lead to dominance of one follicle and the mechanisms that suppress the growth of subordinate follicles are not well understood.When the luteal phase is artificially extended with low doses of exogenous progesterone, the normal pattern of follicular development is altered and the ovulatory follicle grows for a prolonged period of time.This finding indicates that subtle changes in the hormonal milieu can dramatically alter follicular dynamics and that the experimental model of prolonged dominance may be useful in studying the mechanisms of follicular dominance.In contrast, patterns of follicular development in sheep must be assessed in more indirect ways, but sheep offer the advantage of breeds that differ in ovulation rate.Correlation of the endocrine environment with ovulation rate in this species provides a valuable approach to understanding the mechanisms controlling follicle selection and ovulation rate.It has been suggested that in some species a high ovulation rate is achieved by increased recruitment, whereas in others there is increased selection.There is evidence that oestradiol is involved in regulating the number of dominant follicles in sheep.Follicular recruitment requires the presence of gonadotrophins, particularly FSH.In general, the mechanisms that regulate follicular selection and dominance in domestic ruminants are not well understood.Further experiments may determine the relative roles of paracrine factors and ovarian-pituitary-hypothalamic interactions in regulation of follicular selection and dominance in cattle and sheep.
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 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,000 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 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 ».