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- Olsson, Catharina, 1968, et al.
(författare)
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Development of enteric and vagal innervation of the zebrafish (Danio rerio) gut.
- 2008
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Ingår i: The Journal of comparative neurology. - : Wiley. - 1096-9861 .- 0021-9967. ; 508:5, s. 756-70
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Tidskriftsartikel (refereegranskat)abstract
- The autonomic nervous system develops following migration and differentiation of precursor cells originating in the neural crest. Using immunohistochemistry on intact zebrafish embryos and larvae we followed the development of the intrinsic enteric and extrinsic vagal innervation of the gut. At 3 days postfertilization (dpf), enteric nerve cell bodies and fibers were seen mainly in the middle and distal intestine, while the innervation of the proximal intestine was scarcer. The number of fibers and cell bodies gradually increased, although a large intraindividual variation was seen in the timing (but not the order) of development. At 11-13 dpf most of the proximal intestine received a similar degree of innervation as the rest of the gut. The main intestinal branches of the vagus were similarly often already well developed at 3 dpf, entering the gut at the transition between the proximal and middle intestine and projecting posteriorly along the length of the gut. Subsequently, fibers branching off the vagus innervated all regions of the gut. The presence of several putative enteric neurotransmitters was suggested by using markers for neurokinin A (NKA), pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal polypeptide (VIP), nitric oxide, serotonin (5-hydroxytryptamine, 5-HT), and calcitonin gene-related peptide (CGRP). The present results corroborate the belief that the enteric innervation is well developed before the onset of feeding (normally occurring around 5-6 dpf). Further, the more detailed picture of how development proceeds at stages previously not examined suggests a correlation between increasing innervation and more regular and elaborated motility patterns.
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| 2. |
- Olsson, Catharina, 1968, et al.
(författare)
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Identification of genes for the ghrelin and motilin receptors and a novel related gene in fish, and stimulation of intestinal motility in zebrafish (Danio rerio) by ghrelin and motilin.
- 2008
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Ingår i: General and comparative endocrinology. - : Elsevier BV. - 0016-6480. ; 155:1, s. 217-26
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Tidskriftsartikel (refereegranskat)abstract
- In mammals ghrelin has a diverse range of effects including stimulation of gut motility but although present in teleost fish its effects on motility have not been investigated. The present study used bioinformatics to search for fish paralogues of the ghrelin receptor and the closely related motilin receptor, and investigated the effects of ghrelin and motilin on gut motility in zebrafish, Danio rerio. Fish paralogues of the human ghrelin and motilin receptor genes were identified, including those from the zebrafish. In addition, a third gene was identified in three species of pufferfish (the only fish genome completely sequenced), which is distinct from the ghrelin and motilin receptors but more closely aligned to these receptors relative to other G-protein coupled receptors. Immunohistochemistry demonstrated strong ghrelin receptor-like reactivity in the muscle of the zebrafish intestine. In isolated intestinal bulb and mid/distal intestine preparations, ghrelin, motilin, and the motilin receptor agonist erythromycin all evoked contraction; these responses ranged between 9% and 51% of the contractions evoked by carbachol (10(-6) M). There were some variations in the concentrations found to be active in the different tissues, e.g., whereas motilin and rat ghrelin caused contraction of the intestinal bulb circular muscle at concentrations as low as 10(-8) M, human ghrelin (10(-8) to 10(-6) M) was without activity. Neither ghrelin (10(-7) M) nor erythromycin (10(-5) M) affected the contractions evoked by electrical field stimulation. The results suggest that both ghrelin and motilin can regulate intestinal motility in zebrafish and most likely other teleosts, and are discussed in relation to the evolution of these regulatory peptides.
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| 3. |
- Seth, Henrik, 1979, et al.
(författare)
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Effects of gastric distension on the cardiovascular system in rainbow trout (Oncorhynchus mykiss).
- 2008
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Ingår i: American journal of physiology. Regulatory, integrative and comparative physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 294:5
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Tidskriftsartikel (refereegranskat)abstract
- When animals feed, blood flow to the gastrointestinal tract increases to ensure an adequate oxygen supply to the gastrointestinal tissue and an effective absorption of nutrients. In mammals, this increase depends on the chemical properties of the food, as well as, to some extent, on the mechanical distension of the stomach wall. By using an inflatable nitrile balloon positioned in the stomach, we investigated the cardiovascular responses to mechanical stretch of the stomach wall in rainbow trout (Oncorhynchus mykiss). Distension with a volume equivalent to a meal of 2% of the body mass increased dorsal aortic blood pressure by up to 29%, and central venous blood pressure increased transiently nearly fivefold. The increase in arterial pressure was mediated by an increased vascular resistance of both the systemic and the intestinal circulation. Cardiac output, heart rate, and stroke volume (SV) did not change, and only transient changes in gut blood flow were observed. The increase in arterial pressure was abolished by the alpha-adrenergic antagonist prazosin, indicating an active adrenergic vasoconstriction, whereas the venous pressor response could be the consequence of a passive increase in intraperitoneal pressure. Our results show that mechanical distension of the stomach causes an instantaneous increase in general vascular resistance, which may facilitate a redistribution of blood to the gastrointestinal tract when chemical stimuli from a meal induce vasodilation in the gut circulation. The normal postprandial increase in gut blood flow in teleosts is, therefore, most likely partly dependent on mechanical stimuli, as well as on chemical stimuli.
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| 4. |
- Sundqvist, Monika, 1976, et al.
(författare)
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Changes in the control of gastric motor activity during metamorphosis in the amphibian Xenopus laevis, with special emphasis on purinergic mechanisms.
- 2008
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Ingår i: The Journal of experimental biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 211:Pt 8, s. 1270-80
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Tidskriftsartikel (refereegranskat)abstract
- The stomach of the amphibian Xenopus laevis is subject to extensive remodelling during metamorphosis. We investigated the changes in gastric activity control during this period using in vitro circular smooth muscle preparations mounted in organ baths. The nitric oxide synthase inhibitor L-NAME increased mean force in metamorphic and juvenile frogs but not in prometamorphic tadpoles. Serotonin (5-HT) relaxed stomach muscle prior to metamorphosis but elicited a biphasic response in juveniles consisting of contraction at low concentrations and relaxation at high concentrations. The effects of 5-HT were blocked by methysergide. In the prometamorphic tadpole, ATP elicited relaxation that was blocked by the ectonucleotidase inhibitor ARL67156 and the adenosine A(1) receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), suggesting adenosine as the mediator. Exogenous adenosine and the A(1) receptor agonist N(6)-cyclopentyladenosine (CPA) induced relaxation at all stages. After metamorphosis, the potency of ATP decreased and neither DPCPX nor ARL67156 could block ATP-induced relaxation. Uridine 5'-triphosphate (UTP) induced relaxation prior to metamorphosis, but caused contraction of muscle strips from metamorphosing tadpoles. Single doses of UTP blocked phasic contractions in juveniles in a tetrodotoxin (TTX)-sensitive manner while the simultaneous increase in muscle tension was TTX insensitive. The P2X(1)/P2X(3) receptor agonist alpha-beta-MeATP elicited pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS)-sensitive contractions at all stages investigated. These results indicate the development of an inhibitory nitrergic tonus during metamorphosis and a 5-HT receptor involved in muscle contraction. Also, the development of UTP receptors mediating increased tension and neural UTP receptors decreasing contraction frequency in juveniles is indicated. An adenosine A(1)-like receptor mediating relaxation and a P2X-like receptor mediating contraction is demonstrated at all stages.
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