α-Adrenergic regulation of systemic peripheral resistance and blood flow distribution in the turtle<i>Trachemys scripta</i>during anoxic submergence at 5°C and 21°C
Notice bibliographique
Résumé
Anoxic exposure in the anoxia-tolerant freshwater turtle is attended by substantial decreases in heart rate and blood flows, but systemic blood pressure (P(sys)) only decreases marginally due to an increase in systemic peripheral resistance (R(sys)). Here, we investigate the role of the alpha-adrenergic system in modulating R(sys) during anoxia at 5 degrees C and 21 degrees C in the turtle Trachemys scripta, and also describe how anoxia affects relative systemic blood flow distribution (%.Q(sys)) and absolute tissue blood flows. Turtles were instrumented with an arterial cannula for measurement of P(sys) and ultrasonic flow probes on major systemic blood vessels for determination of systemic cardiac output ((.Qsys)). Alpha-adrenergic tone was assessed from vascular injections of alpha-adrenergic agonists and antagonists (phenylephrine and phentolamine, respectively) during normoxia and following either 6 h (21 degrees C) or 12 days (5 degrees C) of anoxic submergence. Coloured microspheres, injected through a left atrial cannula during normoxia and anoxia, as well as after alpha-adrenergic stimulation and blockade during anoxia at both temperatures, were used to determine relative and absolute tissue blood flows. Anoxia was associated with an increased R(sys) and functional alpha-adrenergic vasoactivity at both acclimation temperatures. However, while anoxia at 21 degrees C was associated with a high systemic alpha-adrenergic tone, the progressive increase of R(sys) at 5 degrees C was not mediated by alpha-adrenergic control. A redistribution of blood flow away from ancillary vascular beds towards more vital circulations occurred with anoxia at both acclimation temperatures. %.Q(sys) and absolute blood flow were reduced to the digestive and urogenital tissues (approximately 2- to 15-fold), while %.Q(sys) and absolute blood flows to the heart and brain were maintained at normoxic levels. The importance of liver and muscle glycogen stores in fueling anaerobic metabolism were indicated by increases in %.Q(sys) to the muscle at 21 degrees C (1.3-fold) and liver at 5 degrees C (1.7-fold). As well, the crucial importance of the turtle shell as a buffer reserve during anoxic submergence was indicated by 40-50% of .Q(sys) being directed towards the shell during anoxia at both 5 degrees C and 21 degrees C. Alpha-adrenergic stimulation and blockade during anoxia caused few changes in %.Q(sys) and absolute tissue blood flow. However, there was evidence of alpha-adrenergic vasoactivity contributing to blood flow regulation to the liver and shell during anoxic submergence at 5 degrees C.
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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 | 0,000 | 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 | 0,000 |
| 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 ».