| 1. |
- Holmberg, Anna, 1974, et al.
(författare)
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Ontogeny of the gut motility control system in zebrafish Danio rerio embryos and larvae
- 2004
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 207:23, s. 4085-4094
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Tidskriftsartikel (refereegranskat)abstract
- Using digital motion analysis, the ontogeny of the cholinergic, tachykinin and pituitary adenylate cyclase-activating polypeptide (PACAP) control systems was studied in zebrafish Danio rerio larvae, in vivo. For the first time we show that the regular propagating anterograde waves that occur in the zebrafish larval gut before and around the onset [at 5-6 days post fertilization (d.p.f.)] of feeding are modulated by acetylcholine or atropine, PACAP and NKA (neurokinin A). At 3 d.p.f., when no spontaneous motility has developed, application of acetylcholine did not affect the gut. However, at 4 d.p.f., acetylcholine increased and atropine reduced the frequency of propagating anterograde waves. At 5 d.p.f., NKA increased and PACAP reduced the wave frequency. This suggests that both excitatory and inhibitory pathways develop at an early stage in the gut, independent of exogenous feeding. Immunohistochemistry established the presence of gut neurons expressing PACAP and NKA in the proximal part of the developing gut from the first stage investigated (2 d.p.f.) and before regular motility was observed. I d.p.f. (PACAP) or 2 d.p.f. (NKA) stages later the whole gut was innervated. This supports physiological results that gut motility is under neuronal control during the period when regular motility patterns develop.
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| 2. |
- Johansson, Ågot, 1966, et al.
(författare)
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Characterization of receptors for two Xenopus gastrointestinal tachykinin peptides in their species of origin
- 2004
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Ingår i: Naunyn-Schmiedebergs Archives of Pharmacology. - : Springer Science and Business Media LLC. - 0028-1298 .- 1432-1912. ; 370:1, s. 35-45
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Tidskriftsartikel (refereegranskat)abstract
- Two tachykinin peptides, bufokinin and Xenopus neurokinin A (X-NKA) were recently isolated from Xenopus laevis. In this study we investigated the tachykinin receptors in the Xenopus gastrointestinal tract. In functional studies using stomach circular muscle strips, all peptides had similar potencies (EC50 values 1-7 nM). The rank order of potency to contract the intestine was physalaemin (EC50 1 nM)greater than or equal tobufokinin (EC50 3 nM)>substance P (SP)greater than or equal tocod SP>NKA>>X-NKA (EC50 1,900 nM). No maximum response could be obtained for [Sar(9),Met(O-2)(11)]SP, eledoisin and kassinin. In stomach strips, the mammalian tachykinin receptor antagonists RP 67580 (NK1) and MEN 10376 (NK2) had agonistic effects but did not antagonize bufokinin or X-NKA. In intestinal strips, RP 67580 (1 muM) reduced the maximal response to X-NKA but not bufokinin, while MEN 10376 was ineffective. [I-125]BH-bufokinin bound with high affinity to a single class of sites, of K-D 213+/-35 (stomach) and 172+/-9.3 pM (intestine). Specific binding of [I-125]BH-bufokinin was displaced by bufokiningreater than or equal toSP>NKAgreater than or equal toeledoisinapproximate tokassinin>X-NKA, indicating binding to a tachykinin NK1-like receptor. Selective tachykinin receptor antagonists were weak or ineffective. Other iodinated tachykinins ([I-125]NKA and [I-125]BH-eledoisin) displayed biphasic competition profiles, with the majority of sites preferring bufokinin rather than X-NKA. In conclusion, there is evidence for two different tachykinin receptors in Xenopus gastrointestinal tract. Both receptors may exist in stomach, whereas the bufokinin-preferring NK1-like receptor predominates in longitudinal muscle of the small intestine. Antagonists appear to interact differently with amphibian receptors, compared with mammalian receptors.
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| 3. |
- Sundqvist, Monika, 1976, et al.
(författare)
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Neurotrophin receptors and enteric neuronal development during metamorphosis in the amphibian Xenopus laevis
- 2004
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Ingår i: Cell and Tissue Research. - : Springer Science and Business Media LLC. - 0302-766X .- 1432-0878. ; 316:1, s. 45-54
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Tidskriftsartikel (refereegranskat)abstract
- During metamorphosis, the frog intestine goes through a dramatic shortening with extensive apoptosis and regeneration in the epithelial layer and connective tissue. Our aim was to study changes in the enteric nervous system represented by one inhibitory (vasoactive intestinal polypeptide; VIP) and one excitatory (substance P, neurokinin A; SP/NKA) nerve population and concomitant changes in neurotrophin receptor occurrence during this development in the gut of Xenopus laevis adults and tadpoles at different stages of metamorphosis (NF stages 57-66). Sections were incubated with antibodies against the neurotrophin Trk receptors and p75(NTR), and the neurotransmitters VIP and SP/NKA. Trk-immunoreactive nerves increased dramatically but transiently in number during early metamorphic climax. Nerves immunoreactive for p75(NTR) were present throughout the gut, decreased in number in the middle intestine during climax, and increased in the large intestine during late metamorphosis. The percentage of VIP-immunoreactive nerves did not change during metamorphosis. SP/NKA-immunoreactive nerves were first apparent at NF stages 61-62 in the middle intestine and increased in the stomach and large intestine during metamorphosis. Endocrine cells expressing SP/NKA increased in number in stomach, proximal, and middle intestine during metamorphic climax. Thus, neurotrophin receptors are expressed transiently in neurons of the enteric nervous system during metamorphosis in Xenopus laevis and SP/NKA innervation is more abundant in the intestine of the postmetamorphic frog than in the tadpole.
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