42 ANGIOGENESIS IN CLONED AND IVF-DERIVED BOVINE PREGNANCIES AT DAY 30 OF GESTATION
Notice bibliographique
Résumé
New and expanded microvascular networks in maternal and embryonic tissue are vital to development of a functional placenta. Typically a large proportion of bovine pregnancies derived from somatic cell nuclear transfer (NT) are lost between Days 25 and 45 of gestation. Several laboratories have noted aberrant placental development of NT embryos and fetuses; one factor that may contribute to these defects is faulty maternal or embryonic angiogenesis during placentation. The aim of this study was to determine if angiogenesis in maternal caruncular tissues differs in bovine NT- and IVF-derived pregnancies at the time of placentation. Cloned embryos were produced using cultured ear skin fibroblasts from a 15-year-old Hereford cow; in other experiments, these donor cells resulted in a term live calf and 67% of viable Day-30 embryos dying by Day 51 of gestation. For IVF-derived embryos, IVM oocytes were fertilized with semen from Hereford or Angus bulls. All embryos were cultured in vivo in ligated sheep oviducts, and at Day 8 blastocysts were transferred to synchronized recipient heifers. Whenever possible, one embryo was transferred to each uterine horn. A total of 41 NT and 41 IVF grade 1, 2 and 3 embryos were transferred to 48 recipients. Viable NT (n = 9; 22.0% of transferred) and IVF (n = 9; 22.0%) embryos were recovered at Day 30, and caruncular tissue adjacent to each embryo was sampled. Expression of genes implicated in angiogenesis was measured by real-time quantitative RT-PCR and normalized to histone 2A expression. In addition, paraformaldehyde-fixed sections were stained by the Periodic Acid-Schiffs method to identify blood vessels. Microvascular density was determined as percentage of total tissue area composed of blood vessels in the luminal caruncular stroma as measured by two observers. Data were analyzed by ANOVA using the GLM procedure of SAS (SAS Institute, Cary, NC, USA). Quantification of gene expression revealed no differences between NT and IVF pregnancies for angiogenesis-promoting growth factors and their receptors: vascular endothelial growth factor-A (VEGF-A), VEGF-C, placental growth factor, VEGF receptor-1 (VEGFR-1/flt-1), VEGFR-2 (flk-1/KDR), VEGFR-3 (flt-4), angiopoietin-1 (Ang-1), and Ang receptor-1 (tie-1). Likewise, NT and IVF pregnancies demonstrated similar mean microvascular densities in the caruncles; however, density differed between individual pregnancies across both groups (P < 0.05). For these experiments, the timing of NT and IVF, embryo transfer, and tissue collection on Day 30 was as consistent as possible. Despite these efforts, embryo morphology and developmental stage were highly variable even within the IVF group. It follows that the progress of placentation, and hence the signaling between each embryo and the maternal tissues, may have differed as well, accounting for the variation observed. Our results suggest that failure of maternal tissue to increase angiogenesis during placentation is not a primary cause of aberrant placental development in cloned cattle.
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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 ».