| 1. |
- Krönström, Jenny, 1978, et al.
(author)
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Serotonin and nitric oxide interaction in the control of bioluminescence in northern krill, Meganyctiphanes norvegica (M. Sars)
- 2007
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In: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 210:18, s. 3179-3187
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Journal article (peer-reviewed)abstract
- The role of nitric oxide (NO) in the control of bioluminescence (light production) in the crustacean Meganyctiphanes norvegica (krill) was investigated using pharmacological and immunohistochemical methods. All nitrergic drugs tested failed to induce bioluminescence per se but modulated light production stimulated by 5-hydroxytryptamine (5-HT). NO donors [sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine (SNAP)] injected in live specimens significantly reduced light production stimulated by 5-HT, whereas inhibition of the enzyme NO synthase (NOS) with L-NAME (NG-nitro-L-arginine methyl ester) resulted in an enhancement of the 5-HT response. The effects of NO do not seem to be mediated via production of cGMP as injections of a cGMP analogue (8-Bromoguanosine 3',5'-cyclic monophosphate) gave inconclusive effects on the 5-HT-stimulated light response. Inhibition of cGMP production with ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one) did not affect the light response. Moreover, a few individuals showed a considerably higher response to 5-HT in April and June compared with specimens collected in the autumn and winter. Furthermore, both NOS-like and 5-HT-like materials were detected by immunohistochemistry inside the light organs. NOS-like immunoreactivity was primarily observed in structures associated with vessels inside the light organs, whereas 5-HT-like material was abundant in nerve fibres throughout the whole light organ. The results suggest that NO has a modulatory role at several levels in the control of light production in M. norvegica and that NO and 5-HT interact in this regulation.
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| 2. |
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| 3. |
- Claes, Julien, et al.
(author)
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Nitric oxide in the control of luminescence from lantern shark (Etmopterus spinax)
- 2010
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In: JOURNAL OF EXPERIMENTAL BIOLOGY. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 213:17, s. 3005-3011
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Journal article (peer-reviewed)abstract
- Abstract: Photophores (photogenic organs) of the lantern shark Etmopterus spinax are under hormonal control, with prolactin (PRL) and melatonin (MT) triggering the light emission. Differential sensitivity to these hormones in adult individuals suggests, however, that the luminescence of this shark is controlled by an additional mechanism. In this study, different techniques were used to investigate a potential modulator of E. spinax luminescence-nitric oxide (NO). NO synthase (NOS)-like immunoreactivity (IR) was found in the photocytes (photogenic cells) of the photophores. In addition, acetylated tubulin IR also supported the presence of nerves running through the photogenic tissue and innervating different structural elements of the photophores: photocytes, pigmented cells from the iris-like structure and lens cells. Pharmacological experiments confirmed a modulatory action of NO on the hormonally induced luminescence: NO donors sodium nitroprusside (SNP) and hydroxylamine decreased the time to reach the maximum amplitude (TLmax) of MT-induced luminescence while these substances decreased the maximum amplitude of PRL-induced luminescence (and also the TLmax in the case of SNP). The small impact of the NOS inhibitor L-NAME on hormonally induced luminescence suggests that NO is only produced on demand. The cGMP analogue 8BrcGMP mimicked the effects of NO donors suggesting that the effects of NO are mediated by cGMP.
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| 4. |
- Cramp, R.L., et al.
(author)
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The effects of saltwater acclimation on neurotransmitters in the lingual salt glands of the estuarine crocodile, Crocodylus porosus
- 2007
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In: Regulatory Peptides. - : Elsevier BV. - 0167-0115. ; 140:1-2, s. 55-64
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Journal article (peer-reviewed)abstract
- Introduction Most avian and reptilian salt glands display marked phenotypic plasticity when animals are exposed to hyperosmotic conditions. In addition, the activity of most salt glands is under considerable control by the nervous system and nerves containing cholinergic, adrenergic and peptidergic neurotransmitters have been identified in avian and reptilian salt gland tissues. The present study sought to determine whether the salt glands of the estuarine crocodile, Crocodylus porosus contain the peptidergic neurotransmitters SP, CGRP, VIP, and PACAP and the gaseous neurotransmitter, NO. In addition, we sought to determine whether there was any evidence for the adaptation of the C. porosus salt gland nervous system to hyperosmotic conditions. Methods Salt glands from freshwater- and saltwater-acclimated C. porosus hatchlings were sectioned and examined immunohistochemically for neurotransmitters within the tissue. Results Neurons containing SP, CGRP, VIP, PACAP and NO synthase were identified within C. porosus salt glands. There was no difference in the overall number (density) of neurons within SW-acclimated tissues when compared with FW-acclimated animals. However, there was a significant reduction in density of neurons containing SP and PACAP in SW-acclimated animals. Conclusion C. porosus salt glands display phenotypic plasticity following exposure to hyperosmotic conditions. In addition to cholinergic and adrenergic neurons, they contain a variety of peptidergic neurotransmitters and the gaseous neurotransmitter NO. Additionally, there appears to be some evidence of acclimation of the nervous system of C. porosus to hypersaline conditions, although the functional significance of these changes remains to be determined.
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| 5. |
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| 6. |
- Holmberg, Anna, 1974, et al.
(author)
-
Enteric Control
- 2007
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In: Fish Larval Physiology, Eds RN Finn and BG Kapoor. - Enfield, NH, USA : Science Publishers. - 9781578083886 ; , s. 553-572
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Book chapter (other academic/artistic)
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| 7. |
- Holmberg, Anna, 1974, et al.
(author)
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Ontogeny of the gut motility control system in zebrafish Danio rerio embryos and larvae
- 2004
-
In: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 207:23, s. 4085-4094
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Journal article (peer-reviewed)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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| 8. |
- Holmberg, Anna, 1974, et al.
(author)
-
The effects of endogenous and exogenous nitric oxide on gut motility in zebrafish Danio rerio embryos and larvae
- 2006
-
In: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 209:13, s. 2472-2479
-
Journal article (peer-reviewed)abstract
- Using motion analysis, the ontogeny of the nitrergic control system in the gut was studied in vivo in zebrafish Danio rerio embryos and larvae. For the first time we show the presence of a nitrergic tonus, modulating both anterograde and retrograde contraction waves in the intestine of developing zebrafish. At 4 d.p.f. (days post fertilisation), the nitric oxide synthase (NOS) inhibitor L-NAME (three boluses of 50-100 nl, 10(-3) mol l(-1)) increased the anterograde contraction wave frequency by 0.50 +/- 0.10 cycles min(-1). Subsequent application of the NO donor sodium nitroprusside (SNP; three boluses of 50-100 nl, 10(-4) mol l(-1)) reduced the frequency of propagating anterograde waves (-0.71 +/- 0.20 cycles min(-1)). This coincided with the first appearance of an excitatory cholinergic tonus, observed in an earlier study. One day later, at 5 d.p.f., in addition to the effect on anterograde contraction waves, application of L-NAME increased (0.39 +/- 0.15 cycles min(-1)) and following SNP application reduced (-1.61 +/- 0.36 cycles min(-1)) the retrograde contraction wave frequency. In contrast, at 3 d.p.f., when no spontaneous motility is observed, application of L-NAME did not induce contraction waves in either part of the gut, indicating the lack of a functional inhibitory tonus at this early stage. Gut neurons expressing NOS-like immunoreactivity were present in the distal and middle intestine as early as 2 d.p.f., and at 1 day later in the proximal intestine. In conclusion, the present study suggests that a nitrergic inhibitory tonus develops shortly before or at the time for onset of exogenous feeding.
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| 9. |
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| 10. |
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| 11. |
- Holmgren, Susanne, 1946, et al.
(author)
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Nervous system of the gut
- 2011
-
In: Encyclopedia of Fish Physiology: From Genome to Environment (AP Farrell ed.) Integrated function and control of the gut (S Holmgren, C Olsson, section eds.). - : Elsevier. - 9780080923239 ; , s. 1332-1340
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Book chapter (peer-reviewed)
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| 12. |
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| 13. |
- Holmgren, Susanne, 1946, et al.
(author)
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The neuroendocrine regulation of gut function
- 2009
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In: Fish Physiology Volume 28: Fish Neuroendocrinology (Eds Nicholas J. Bernier, Geln Van Der Kraak, Anthony P. Farrel, Colin J. Brauner). - : Academic Press. - 9780123746313 ; , s. 467-512
-
Book chapter (other academic/artistic)
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| 14. |
- Johansson, Ågot, 1966, et al.
(author)
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Characterization of receptors for two Xenopus gastrointestinal tachykinin peptides in their species of origin
- 2004
-
In: Naunyn-Schmiedebergs Archives of Pharmacology. - : Springer Science and Business Media LLC. - 0028-1298 .- 1432-1912. ; 370:1, s. 35-45
-
Journal article (peer-reviewed)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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| 15. |
- Jönsson, Elisabeth, 1968, et al.
(author)
-
Endocrine systems of the gut
- 2011
-
In: Encyclopedia of Fish Physiology: From gene to environment. (A.P. Farrell ed). Elsevier. - : Academic Press. - 9780123745453 ; , s. 1341-1347
-
Book chapter (peer-reviewed)abstract
- The gut endocrine system comprises dispersed enteroendocrine cells in its epithelium. These cells produce many different hormones, with important roles in control of gastrointestinal functions such as appetite and food processing. Many hormones like serotonin are present both in gut nerves and/or endocrine cells, and others, like glucagon-like peptide-1, are secreted both from pancreas and intestinal mucosa. The effects range from local paracrine (or neurocrine) to broad general effects. Histamine and somatostatin produced by stomach mucosa locally stimulate the stomach to release gastric acid. Cholecystokinin produced by intestinal cells has broader effects, inducing gallbladder contraction and inhibiting appetite. Ghrelin has even more widespread effects, being a potent growth hormone secretagog and appetite regulator, besides having other functions. Leptin was only recently discovered in fish gut.
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| 16. |
- Krönström, Jenny, 1978, et al.
(author)
-
Involvement of contractile elements in control of bioluminescence in Northern krill, Meganyctiphanes norvegica (M. Sars).
- 2009
-
In: Cell and tissue research. - : Springer Science and Business Media LLC. - 1432-0878 .- 0302-766X. ; 336:2, s. 299-308
-
Journal article (peer-reviewed)abstract
- Inside the light organs of the bioluminescent (light-producing) crustacean Meganyctiphanes norvegica (krill), numerous capillaries drain haemolymph into the light-producing structure (lantern). We have investigated the arrangement and function of filamentous material found around the opening of the capillaries. These have been suggested to work as sphincters, controlling the haemolymph (i.e. oxygen) supply to the lantern and thereby the production of light. Electron microscopy shows that the filamentous material consists of thick and thin muscle filaments arranged in perpendicular blocks around the opening of each capillary. The actin probe rhodamine phalloidin has revealed that one component is filamentous actin. Clusters of vesicle-dense nerve profiles surround the cells containing filamentous material and antibodies against 5-hydroxytryptamine (5-HT) reveal that 5-HT containing nerves lead to the filamentous area. When exposed to the muscle-relaxing substances papaverine and verapamil, krill respond with luminescence, suggesting that the sphincter structures are functionally involved in the control of light production. Treatment with the muscle-contracting drugs Bay K8544 and thapsigargin gives no light response. Thus, 5-HT stimulates light production in krill; however, a combination of 5-HT and the muscle-relaxing drugs or Bay K8544 potentiates the effect of 5-HT. Thapsigargin quenches the response to 5-HT. Our results corroborate speculations of earlier authors who have suggested that the sphincter structures are of a muscular nature and important in controlling light production in krill. However, other parameters in addition to the oxygen supply to the lantern are involved in controlling bioluminescence in the light organs of M. norvegica.
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| 17. |
- Krönström, Jenny, 1978, et al.
(author)
-
Nitric oxide in control of luminescence from hatchetfish (Argyropelecus hemigymnus) photophores
- 2005
-
In: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 208:15, s. 2951-2961
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Journal article (peer-reviewed)abstract
- Nitric oxide synthase-like immunoreactivity (NOS-LI IR) was detected by immunohistochemistry in ventral light organs of the mesopelagic fish, Argyropelecus hemigymnus. Strong NOS-LI IR was present in nerve fibres and in other cells central for production or modulation of light: immunoreactive fibres surrounded the photophores, and were also present in the filter area. Filter cells, particularly in the outer layers, showed strong IR throughout the cytoplasm. Pharmacological studies suggested that nitric oxide (NO) modulates adrenaline-stimulated light emission, and that the modulation is correlated to the ability of the light organ to respond to adrenaline. Adrenaline is known to produce two different types of light response in isolated photophores from Argyropelecus: a slow, long-lasting, high intensity response, or a fast and weak response of short duration. Incubation of photophores in the NO donors sodium nitroprusside or S-nitroso-N-acetylpenicillamine prior to adrenaline stimulation reduced the intensity of the strong and long-lasting type of response, but had little or even a potentiating effect on the weakly responding photophores. Hydroxylamine, which is converted to NO if catalase activity is present in the tissue, reduced the duration and the intensity of the adrenaline response in all tested organs. The NOS-inhibitor L-thiocitrulline potentiated the adrenaline response in the weakly responding organs; the weaker the adrenaline effect, the stronger the potentiation caused by L-thiocitrulline. The strongly responding organs were instead inhibited by L-thiocitrulline. The results suggest that NO has an important role in the control of light emission from Argyropelecus hemigymnus photophores. The cGMP analogue dibutyryl cGMP, the guanylate cyclase inhibitor ODQ and the phosphodiesterase inhibitor pentoxiphylline had no effect, indicating that the NO effect does not involve cGMP.
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| 18. |
- Olsson, Catharina, 1968, et al.
(author)
-
Autonomic control of gut motility: A comparative view.
- 2011
-
In: Autonomic Neuroscience: Basic and Clinical. - : Elsevier BV. - 1566-0702. ; 165:1, s. 80-101
-
Research review (peer-reviewed)abstract
- Gut motility is regulated to optimize food transport and processing. The autonomic innervation of the gut generally includes extrinsic cranial and spinal autonomic nerves. It also comprises the nerves contained entirely within the gut wall, i.e. the enteric nervous system. The extrinsic and enteric nervous control follows a similar pattern throughout the vertebrate groups. However, differences are common and may occur between groups and families as well as between closely related species. In this review, we give an overview of the distribution and effects of common neurotransmitters in the vertebrate gut. While the focus is on birds, reptiles, amphibians and fish, mammalian data are included to form the background for comparisons. While some transmitters, like acetylcholine and nitric oxide, show similar distribution patterns and effects in most species investigated, the role of others is more varying. The significance for these differences is not yet fully understood, emphasizing the need for continued comparative studies of autonomic control.
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| 19. |
- Olsson, Catharina, 1968, et al.
(author)
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Development of enteric and vagal innervation of the zebrafish (Danio rerio) gut.
- 2008
-
In: The Journal of comparative neurology. - : Wiley. - 1096-9861 .- 0021-9967. ; 508:5, s. 756-70
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Journal article (peer-reviewed)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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| 20. |
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| 21. |
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| 22. |
- Olsson, Catharina, 1968, et al.
(author)
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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
-
In: General and comparative endocrinology. - : Elsevier BV. - 0016-6480. ; 155:1, s. 217-26
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Journal article (peer-reviewed)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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| 23. |
- Seth, Henrik, 1979, et al.
(author)
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Effects of gastric distension on the cardiovascular system in rainbow trout (Oncorhynchus mykiss).
- 2008
-
In: American journal of physiology. Regulatory, integrative and comparative physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 294:5
-
Journal article (peer-reviewed)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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| 24. |
- Shahbazi, Fatemeh, et al.
(author)
-
Cod CGRP and tachykinins in coeliac artery innervation of the Atlantic cod, Gadus morhua: presence and vasoactivity.
- 2009
-
In: Fish physiology and biochemistry. - : Springer Science and Business Media LLC. - 1573-5168 .- 0920-1742. ; 35:3, s. 369-76
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Journal article (peer-reviewed)abstract
- The presence and vasoactive effects of native calcitonin gene-related peptide (CGRP), substance P (SP), and neurokinin A (NKA) were studied on isolated small branches of the coeliac artery from Atlantic cod, Gadus morhua, using immunohistochemistry and myograph recordings, respectively. Immunohistochemistry revealed nerve fibers containing CGRP- and SP/NKA-like material running along the wall of the arteries. CGRP induced vasorelaxation of precontracted arteries with a pD(2) value of 8.54 +/- 0.17. Relaxation to CGRP (10(-8) M) was unaffected by L-NAME (3 x 10(-4) M) and indomethacin (10(-6) M) suggesting no involvement of nitric oxide or prostaglandins in the CGRP-induced relaxation. SP and NKA (from 10(-10) to 3 x 10(-7) M) contracted the unstimulated arteries at concentrations from 10(-8) M and above in 42% and 33%, respectively, of the vessels. It is concluded that the innervation of the cod celiac artery includes nerves expressing CGRP-like and tachykinin-like material, and that a vasodilatory response to CGRP is highly conserved amongst vertebrates while the response to tachykinins is more variable.
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| 25. |
- Sundqvist, Monika, 1976, et al.
(author)
-
Changes in the control of gastric motor activity during metamorphosis in the amphibian Xenopus laevis, with special emphasis on purinergic mechanisms.
- 2008
-
In: The Journal of experimental biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 211:Pt 8, s. 1270-80
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Journal article (peer-reviewed)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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| 26. |
- Sundqvist, Monika, 1976, et al.
(author)
-
Neurotrophin receptors and enteric neuronal development during metamorphosis in the amphibian Xenopus laevis
- 2004
-
In: Cell and Tissue Research. - : Springer Science and Business Media LLC. - 0302-766X .- 1432-0878. ; 316:1, s. 45-54
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Journal article (peer-reviewed)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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| 27. |
- Sundqvist, Monika, 1976, et al.
(author)
-
Ontogeny of excitatory and inhibitory control of gastrointestinal motility in the African clawed frog, Xenopus laevis
- 2006
-
In: American Journal of Physiology-Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 291:4
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Journal article (peer-reviewed)abstract
- The transparent body wall of Xenopus laevis larvae during the first developmental stages allows in vivo studies of gastrointestinal tract activity. The purpose of this study was to chart the ontogeny of gut motility in Xenopus larvae and to identify the most important control systems during the first developmental stages. Coordinated descending contraction waves first occurred in the gut at Nieuwkoop and Faber stage 43 [0.8 +/- 0.1 contractions/min (cpm)] and increased to 4.9 +/- 0.1 cpm at stage 47. The cholinergic receptor agonist carbachol (5 - 10 mu M) increased contraction frequency already at stage 43, as did neurokinin A (NKA, 0.3 - 1 mu M). The muscarinic antagonist atropine (100 mu M) first affected contraction frequency at stage 45, which coincides with the onset of feeding. The tachykinin antagonist MEN-10,376 (6 mu M) blocked NKA-induced contractions but not spontaneous motility. Both sodium nitroprusside [nitric oxide (NO) donor, 1 - 10 mu M] and vasoactive intestinal peptide (VIP, 0.1 - 1 mu M) inhibited contractions from the earliest stage onward. Blocking NO synthesis using N-G-nitroL- arginine methyl ester (100 mu M) had no effect per se, but antagonized VIP evoked inhibition at stage 47. We conclude that gastrointestinal motility is well developed in the Xenopus laevis larvae before the onset of feeding. Functional muscarinic and tachykinin receptors are present already at the onset of motility, whereas a cholinergic tone develops around the onset of feeding. No endogenous tachykinin tone was found. Functional VIP receptors mediate inhibition at the onset of motility. NO seems to mediate the VIP effect at later stages.
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