89 Does progesterone block the nerve growth factor–induced luteinizing hormone surge in llamas?
Notice bibliographique
Résumé
The central inhibitory effects of progesterone on gonadotrophin secretion have been well documented in several species, including camelids. Nerve growth factor (NGF) in seminal plasma triggers ovulation in camelids and is thought to act at the level of the hypothalamus. The objective of the study was to determine the effect of progesterone on NGF-induced LH release in llamas. In Experiment 1, llamas were assigned to a low, medium, or high progesterone group (n = 4 per group). The low progesterone group consisted of non-mated (non-ovulatory) llamas, the medium progesterone group consisted of mated llamas (luteal phase; 3–4 weeks pregnant), and the high progesterone group consisted of non-mated llamas given a single intramuscular (IM) dose of progesterone (300 mg IM, Progesterone BioRelease LA). A jugular catheter was placed, and the following day llamas were given an intravenous dose of 1 mg of NGF isolated from seminal plasma. Blood samples were taken every 30 min from 1 h before to 5.5 h after NGF treatment. In Experiment 2, the pituitary LH response to gonadotrophin-releasing hormone (GnRH) was compared between llamas treated with either Progesterone BioRelease LA or saline (n = 4 per group). Sixteen hours later, llamas in both groups were given 50 µg of gonadorelin (GnRH) IV, and blood samples were collected by jugular puncture at 0.5 h before and 0, 1, 2, and 4 h after GnRH. Blood samples were centrifuged, and plasma was stored frozen until radioimmunoassay for LH and progesterone. Data are presented as mean ± s.e.m. Data were analysed by one-way ANOVA for single-point and repeated-measures, and independent or paired t-tests. In Experiment 1, plasma progesterone concentrations in the low, medium, and high progesterone groups were 0.6 ± 0.3, 8.2 ± 0.4, and 14.9 ± 1.2 ng mL−1, respectively, at the time of NGF treatment (P < 0.05). Circulating concentrations of LH did not differ among progesterone groups (treatment, P = 0.49; time, P < 0.01; treatment × time interaction, P = 0.65). In all groups, LH concentrations were elevated within 30 min of NGF administration, reached a peak by 2 h, and remained elevated beyond the sampling period. Comparison of samples collected during the pretreatment period (i.e. −60, −30, and 0 min), however, revealed that plasma LH concentrations in the high progesterone group were half that of the low and medium progesterone groups (P < 0.03). In Experiment 2, plasma progesterone concentrations in the progesterone- and saline-treated groups were 12.7 ± 2.2 and 1.3 ± 0.3 ng mL−1, respectively (P < 0.01). Despite the difference in circulating progesterone concentrations, the LH response to GnRH treatment was not different between groups (treatment group, P = 0.43; time, P < 0.01; treatment × time interaction, P = 0.84). Results demonstrate a suppressive effect of progesterone on basal LH release in llamas, but no suppressive effect on NGF- or GnRH-induced surge release from the pituitary gland. Results are consistent with the hypothesis that the site of action of NGF is downstream of the hypothalamic site of action of progesterone. This research was supported by NSERC Canada.
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 distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 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 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 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 tête enseignante, 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 ».