Changes in Brain Water Content in the Rainbow Trout (Oncorhynchus mykiss) and in the Goldfish (Carassius auratus) due to High External Ammonia Exposure
Notice bibliographique
Résumé
In fishes, hyperammonemia may occur following feeding or exposure to abnormally high concentrations of environmental ammonia due to sewage effluents, agricultural run-off and in crowded aquaculture pens. Increased internal ammonia can result in hyperactivity, convulsions, coma and death. In mammals, it is also associated with potentially fatal brain edema, in which the accumulation of intracellular water results in swelling, increased intracranical pressure and herniation leading to death. Recently it was shown that rainbow trout (Oncorhynchus mykiss) and goldfish (Carassius auratus) experience brain swelling following exposure to high external ammonia (HEA). However, the mechanism of ammonia-induced brain swelling in fishes remains unsolved. The goal of this thesis was to determine the underlying mechanisms of ammonia-induced swelling in the fish brain. The specific research objectives were to (i) determine if intracellular glutamine accumulation contributed to brain swelling by increasing intracellular osmolarity; (ii) ascertain what role NMDA receptor over-activation might play in mediating ammonia-induced brain swelling, and (iii) determine if changes in brain water content were accompanied by disturbances to ion balance and transport processes in the brain. Exposure of rainbow trout (1mM NH4Cl) and goldfish (5mM NH4Cl) to 48 h HEA lead to a 12-15% increase in brain water content, 10-fold increase in plasma ammonia [TAmm], and 5-6-fold increase in brain glutamine. Dry brain Na+ content displayed similar trends to brain water content, increasing approximately 45-70 %, while K+ was reduced by approximately 10-24 %. These changes were accompanied by simultaneously, 50 % reductions in rainbow trout brain Na+/K+-ATPase activity after 48 h high external ammonia (HEA). Goldfish were able to withstand higher concentrations of external ammonia compared to the rainbow trout, which was consistent with greater tolerance observed in previous studies. Remarkably, brain water content was restored to control levels following 24 h recovery in ammonia-free well water. Administration of MK801 (dizocilpine) an NMDA receptors antagonist prior to HEA prevented significant brain swelling in the rainbow trout but not in goldfish. Additionally, the administration of MK801 caused a reduction from control levels in brain Na+ content in both species. Lastly, the administration of glutamine synthetase inhibitor, methionine sulfoximine (MSO) to each species followed by 48 h HEA did not prevent significant swelling. In conclusion, HEA resulted in water accumulation in the brain, but this was not due to increased glutamine production. Rather, brain swelling appears to be mediated by NMDA receptors followed by ionic disturbances, resulting in brain swelling.
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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 | 0,000 |
| 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 ».