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  • 1
    Electronic Resource
    Electronic Resource
    Biphasic increase of apical Cl− conductance by muscarinic stimulation of ht-29cl.19a human colon carcinoma cell line: Evidence for activation of different cl− conductances by carbachol and forskolin (1992)
    Springer
    The journal of membrane biology 127 (1992), S. 81-94 
    Details
    ISSN: 1432-1424
    Keywords: ionomycin ; phorbol-ester ; basolateral K+ conductance ; Cl− channel ; cystic fibrosis ; secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The modulation of ion transport pathways in filtergrown monolayers of the Cl−-secreting subclone (19A) of the human colon carcinoma cell line HT-29 by muscarinic stimulation was studied by combined Ussing chamber and microimpalement experiments. Basolateral addition of 10−4 m carbachol induced a complex poly-phasic change of the cell potential consisting of (i) a fast and short (30-sec) depolarization of 15±1 mV from a resting value of −52±1 mV and an increase of the fractional resistance of the apical membrane (first phase), (ii) a repolarization of 22±1 mV leading to a hyperpolarization of the cell (second phase), (iii) a depolarization of 11±1 mV and a decrease of the fractional resistance of the apical membrane (the third phase), (iv) and sometimes, a hyperpolarization of 6±1 mV and an increase of the fractional resistance of the apical membrane (fourth phase). The transepithelial potential increased with a peak value of 2.4±0.3 mV (basolateral side positive). The transepithelial PD started to increase (serosa positive), coinciding with the start of the second phase of the intracellular potential change, and continued to increase during the third phase. Ion replacements and electrical circuit analyses indicate that the first phase is caused by increase of the Cl− conductance in the apical and basolateral membrane, the second phase by increased K+ conductance of the basolateral membrane, and the third phase and the fourth phase by increase and decrease, respectively, of an apical Cl− conductance. The first and second phase of the carbachol effect could be elicited also by ionomycin. They were strongly reduced by EGTA. Phorbol dibutyrate (PDB) induced a sustained depolarization of the cell and a decrease of the apical fractional resistance. The results suggest that two different types of Cl− channels are involved in the carbachol response: one Ca2+ dependent and a second which may be PKC sensitive. In the presence of a supramaximal concentration of forskolin, carbachol evoked a further increase of the apical Cl− conductance. It is concluded that the short-lasting carbachol/Ca2+-dependent Cl− conductance is different from the forskolin-activated conductance. The increase of the Cl− conductance in the presence of forskolin by carbachol may be due to activation of different Cl− channels or to modulation of the PKA-activated Cl− channels by activated PKC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233281
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  • 2
    Electronic Resource
    Electronic Resource
    Microscopical determination of the filtration permeability of the mucosal surface of the goldfish intestinal epithelium (1981)
    Springer
    The journal of membrane biology 63 (1981), S. 31-39 
    Details
    ISSN: 1432-1424
    Keywords: intestine ; mucosal hypertonicity ; morphology ; filtration permeability ; goldfish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The rate of shrinkage of the mucosal folds of goldfish intestine in response to mucosal hypertonicity was measured by microscopic means. Because of the geometry of the intestinal folds the rate of shrinkage could be directly related to the loss of volume from the fold through the brush border membranes and tight junctions. Experimentally a wide range of velocities was observed, reflecting the difficulty of rapidly estabilishing a uniform osmotic gradient at the preparation's mucosal surface. The initial velocity of volume loss provided a measure of the filtration permeability (P f ) of the mucosal surface. From the highest velocities observed the filtration permeability was estimated to be approximately 14×10−3 cm/sec related to the folded mucosal surface and 65×10−3 cm/sec related to the straight serosal surface. Consideration of the experimental errors and unstirred layer effects make it probable that the latter value is still an underestimate of the trueP f . The series barriers of the epithelium cause the total tissueP f to be less than theP f of the mucosal surface alone. In addition theP f measured in the presence of an osmotic gradient may differ substantially from the tissue filtration permeability which exists in the absence of a change in osmolarity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01969443
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  • 3
    Electronic Resource
    Electronic Resource
    Electrophysiological studies of forskolin-induced changes in ion transport in the human colon carcinoma cell line HT-29 cl.19A: Lack of evidence for a cAMP-activated basolateral K+ conductance (1991)
    Springer
    The journal of membrane biology 122 (1991), S. 239-250 
    Details
    ISSN: 1432-1424
    Keywords: Cl− transport ; K+ conductance ; forskolin ; cAMP ; HT-29 cl.19A ; electrophysiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Forskolin (i.e, cAMP)-modulation of ion transport pathways in filter-grown monolayers of the Cl−-secreting subclone (19A) of the human colon carcinoma cell line HT29 was studied by combined Ussing chamber and microimpalement experiments. Changes in electrophysiological parameters provoked by serosal addition of 10−5 m forskolin included: (i) a sustained increase in the transepithelial potential difference (3.9±0.4 mV). (ii) a transient decrease in transepithelial resistance with 26±3 Ω · cm2 from a mean value of 138±13 Ω · cm2 before forskolin addition, (iii) a depolarization of the cell membrane potential by 24±1 mV from a resting value of −50±1 mV and (iv) a decrease in the fractional resistance of the apical membrane from 0.80±0.02 to 0.22±0.01. Both, the changes in cell potential and the fractional resistance, persisted for at least 10 min and were dependent on the presence of Cl− in the medium. Subsequent addition of bumetanide (10−4 m), an inhibitor of Na/K/2Cl cotransport, reduced the transepithelial potential, induced a repolarization of the cell potential and provoked a small increase of the transepithelial resistance and fractional apical resistance. Serosal Ba2+ (1mm), a known inhibitor of basolateral K+ conductance, strongly reduced the electrical effects of forskolin. No evidence was found for a forskolin (cAMP)-induced modulation of basolateral K+ conductance. The results suggest that forskolin-induced Cl− secretion in the HT-29 cl.19A colonic cell line results mainly from a cAMP-provoked increase in the Cl− conductance of the apical membrane but does not affect K+ or Cl− conductance pathways at the basolateral pole of the cell. The sustained potential changes indicate that the capacity of the basolateral transport mechanism for Cl− and the basal Ba2+-sensitive K+ conductance are sufficiently large to maintain the Cl− efflux across the apical membrane. Furthermore, evidence is presented for an anomalous inhibitory action of the putative Cl− channel blockers NPPB and DPC on basolateral conductance rather than apical Cl− conductance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871424
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  • 4
    Electronic Resource
    Electronic Resource
    Calcium ionophore plus excision induce a large conductance chloride channel in membrane patches of human colon carcinoma cells HT-29cl.19A (1993)
    Springer
    Cellular and molecular life sciences 49 (1993), S. 313-316 
    Details
    ISSN: 1420-9071
    Keywords: Maxi-chloride channel ; HT-29 ; intestinal epithelium ; electrolyte transport ; Ca2+-ionophore
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In excised inside-out membrane patches of the human colon carcinoma HT-29cl.19A cells a large conductance (373±10 pS) chloride channel was found. Channel activity could only be observed after excision of patches from cells incubated with calcium ionophore. The channel was never observed in cell-attached patches. The channel was strongly voltage dependent, being open only between +30 and −30 mV clamp potentials. The selectivity sequence among anions, deduced from reversal potentials, was I〉Br〉Cl〉F〉gluconate. The PNa/PCl was 0.09. Although a similar type of channel, has been described earlier, this is the first report stating its appearance in patches of intestinal epithelial cells requiring the combined action of Ca2+ ionophore and excision, suggesting its control by an intracellular compound.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01923409
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  • 5
    Electronic Resource
    Electronic Resource
    Exocytotic release of vasoactive intestinal polypeptide and serotonin from mucosal nerve fibres and endocrine cells of the intestine of the goldfish (Carassius auratus) and the tilapia (Oreochromis mossambicus): an ultrastructural study (1997)
    Springer
    Journal of molecular histology 29 (1997), S. 45-51 
    Details
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In earlier studies we determined the effect, presence and ultrastructure of vasoactive intestinal polypeptide (VIP) and 5- hydroxytryptamine (5-HT)-containing nerve fibres in the tilapia and goldfish intestinal mucosa. 5-HT-labelled varicosities were found close to the epithelial cells; however, synaptic membrane specializations have never been observed. VIP-like immunoreactive nerve fibres appear to be located less frequently close to the goldfish epithelium, as in the tilapia intestine, in which the distance between the VIP- or 5-HT-labelled varicosities and the epithelial cells was also rather large (more than 2 μm). To establish a possible role of VIP and 5-HT as neurotransmitters involved in the regulation of fish intestinal epithelium, both electron microscopical and immunoelectron microscopical methods were used to visualize the release of 5-HT and VIP from nerve fibres. We found exocytoses from VIP-ergic and serotonergic varicosities in the muscle layers of both fish. Directly underneath the intestinal epithelium of the goldfish, it was demonstrated that 5-HT could be released from scarce varicosities. The release of 5-HT in the tilapia intestinal mucosa could only be observed from endocrine cells
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026464801501
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of forskolin and carbachol on intestinal absorption of horseradish peroxidase in the goldfish (Carassius auratus) (1996)
    Springer
    Cell & tissue research 285 (1996), S. 51-56 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Intestine ; Endocytosis ; Tight junctions ; Carbachol ; Forskolin ; Transport ; Carassius auratus (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The transepithelial route for mucosa-to-serosa transport of the tracer macromolecule horseradish peroxidase (HRP; MW 40 kDa) and modulation of this transport by forskolin and carbachol have been studied in vi-tro in stripped goldfish intestinal epithelium mounted in Ussing-type chambers. Uptake and transport have been investigated by measuring the HRP flux from the muco-sal to serosal sides by an enzymatic method and by visualising HRP reaction products in the mucosa with electron-microscopical techniques. Both the cholinergic agonist carbachol (which is thought to increase intracellular Ca2+ and activate protein kinase C activity) and forskolin (a direct activator of adenylylcyclase) affect the amount of enzymatically active HRP in the tissue. In control tissue, HRP product is found only within the epithelial cells, the transepithelial flux reaching a constant value of about 1.5 pmoles/cm2 per h. Carbachol increases the amount of HRP product in the cells, but has no significant effect on the HRP flux compared with control values. Forskolin decreases the amount of HRP product in the cells; however, in the presence of forskolin, the lateral intercellular spaces become filled with HRP product. HRP is found in the lamina propria and the transepithelial protein flux increases more than 2.5-fold. In the presence of forskolin plus carbachol, the results are no different from the control. It is concluded that carbachol increases the endocytotic uptake of HRP, whereas forskolin inhibits the uptake but increases the paracellular permeability for HRP in goldfish intestine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050619
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  • 7
    Electronic Resource
    Electronic Resource
    Ultrastructural study of the presence of vasoactive intestinal polypeptide and serotonin in mucosal nerve fibres and endocrine cells of the intestine of goldfish (Carassius auratus) and tilapia (Oreochromis mossambicus) (1995)
    Springer
    Cell & tissue research 283 (1995), S. 143-150 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Vasoactive intestinal polypeptide (VIP) ; Serotonin ; Ultrastructure ; Immunogold label ; Mucosal nerves ; Goldfish ; Carassius auratus ; Tilapia ; Oreochromis mossambicus (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. In order to establish a possible role of vasoactive intestinal polypeptide (VIP) and serotonin as (neuro)transmitters involved in the regulation of fish intestinal epithelium, we studied the presence of VIP and serotonin at the ultrastructural level in the intestinal mucosa of tilapia and goldfish. A low percentage of varicosities near the basal membrane of the tilapia intestinal epithelium was found to label for VIP or for serotonin, whereas in the goldfish, this percentage was much higher. The varicosities usually contained large granular and small clear vesicles. Immunogold labeling indicated that serotonin and VIP were localized in the large granular vesicles. Unlabeled large granular vesicles and small clear vesicles were usually also present in varicosities with serotonin- or VIP-labeled vesicles. In the goldfish, the serotonin-labeled varicosities were close to the epithelial cells, and direct contacts between serotonin-labeled nerve fibres and epithelial cells could sometimes be visualized. However, synaptic membrane specializations were never observed. In tilapia, the distance between the VIP- or serotonin-labeled varicosities and the epithelial cells was large (more than 2 μm).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050522
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  • 8
    Electronic Resource
    Electronic Resource
    Changes in surgar transport and in electrophysiological characteristics of intestinal preparations of temperature-acclimated goldfish (Carassius auratus L.) (1983)
    Springer
    Journal of comparative physiology 151 (1983), S. 163-170 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Goldfish were acclimated to temperatures of 10°C and 30°C for at least 4 weeks. 2. Fish acclimated to 10°C have longer intestines with larger mucosal folds than fish acclimated to 30°C. 3. When fish acclimated to 10°C are compared with 30°C fish, the electrical resistance of intestinal mucosa, expressed in Ωcm2 of serosal area, from 10°C-acclimated fish is higher. However when related to mucosal area, the resistance in 30°C-acclimated fish is higher. 4. Mucosal glucose application evokes a change in the transepithelial potential difference. Although this effect is smaller in the intestines of 30°C-acclimated fish, a sustained change in potential difference due to the presence of glucose is observed in both cases. 5. Transepithelial sugar transport across in vitro intestinal preparations was measured using 3-oxy-methyl-d-glucose as a substrate. At 30°C the net flux, expressed in mmol·kg wet weight−1·h−1, is larger in intestinal mucosa of 30°C-acclimated fish than in mucosa of 10°C-fish. 6. Ion content was determined in both freshly isolated muscosa and mucosa incubated for 1 h at 20°C. The sodium concentration in intestinal cells from 30°C-acclimated fish was found to be higher. 7. Oxygen consumption by intestinal mucosa was determined at 20°C in the absence and presence of ouabain. The difference in ouabain-sensitive oxygen consumption between 10°C-fish or 30°C-fish is not significant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00689914
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  • 9
    Electronic Resource
    Electronic Resource
    Neuropeptides in the intestine of two teleost species (Oreochromis mossambicus, Carassius auratus): Localization and electrophysiological effects on the epithelium (1993)
    Springer
    Cell & tissue research 271 (1993), S. 123-134 
    Details
    ISSN: 1432-0878
    Keywords: Vasoactive intestinal polypeptide ; Neuropeptide Y ; Enkephalin ; Calcitonin gene-related peptide ; Galanin ; Immunohistochemistry ; Enteric nervous system ; Oreochromis mossambicus, Carassius auratus (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The presence of bioactive peptides in the gut and their possible electrophysiological effects on the intestinal epithelium were studied in two teleost species, the tilapia (Oreochromis mossambicus) and the goldfish (Carassius auratus). Vasoactive intestinal polypeptide-like immunoreactive nerve fibres were found beneath the intestinal epithelium of both species. Galanin-, metenkephalin-and calcitonin gene-related peptide-like immunoreactive nerve fibres were found exclusively in the mucosa of the tilapia. Both species had vasoactive intestinal polypeptide-, enkephalin- or neuropeptide Y-like immunoreactive endocrine cells; calcitonin gene-related peptide-like immunoreactive endocrine cells were additionally found in the tilapia. Somatostatin- and dopamine-β-hydroxylase-like immunoreactivities were not observed. Nerve cell bodies in the myenteric plexus of both species showed immunoreactivity for calcitonin gene-related peptide-, vasoactive intestinal polypeptide-, and galanin-like peptide. Enkephalin-like immunoreactive nerve cell bodies were present in the tilapia only. None of the peptides had a pronounced electrogenic effect. However, calcitonin gene-related peptide added to stripped intestinal epithelium of the tilapia, reduced the ion selectivity, and addition of galanin increased the ion selectivity. In goldfish intestine, both galanin and calcitonin gene-related peptide were without effect. Enkephalin counteracted the serotonin-induced reduction of the ion selectivity of the goldfish intestinal epithelium, but had no effect on the tilapia epithelium. In both species, vasoactive intestinal polypeptide reduced the ion selectivity of the intestinal epithelium, and neuropeptide Y induced an increase of the ion selectivity. Somatostatin showed no effect on the epithelial ion selectivity of either species. Tetrodotoxin did not inhibit the effects of the peptides studied. The changes in ion selectivity suggest that the enterocytes may be under the regulatory control of these peptides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297550
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  • 10
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    Ultrastructural study of the presence of vasoactive intestinal polypeptide and serotonin in mucosal nerve fibres and endocrine cells of the intestine of goldfish ( Carassius auratus ) and tilapia ( Oreochromis mossambicus ) (1995)
    Springer
    Details
    Publication Date: 1995-12-19
    Print ISSN: 0302-766X
    Electronic ISSN: 1432-0878
    Topics: Biology , Medicine
    Published by Springer
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