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  • 1
    ISSN: 1432-041X
    Keywords: Fowl embryo ; Catecholamine accumulation ; Formaldehyde-induced-fluorescence ; Non-neural tissues ; Morphogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Catecholamines (CA) were localized in stage 11–34 domestic fowl embryos by the formaldehyde-induced fluorescence (FIF) method after exposure in vivo or in vitro to CA (noradrenaline or α-methylnoradrenaline), or the CA precursorl-DOPA. The effects of drugs known to alter CA metabolism in the adult were also investigated. Negligible FIF was observed in embryos which had not been exposed to CA. After CA loading, FIF could be seen in the neural tube and in non-neural tissues such as the notochord and gut mesenchyme and to a lesser degree in suprarenal area tissue, liver endothelium, sclerotome, and myotome. This FIF was inhibited by desmethylimipramine, a blocker of adult neuronal CA uptake (Uptake1), but not by corticosterone, a blocker of adult extraneuronal CA uptake (Uptake2). The notochord, dorsal pancreas and some blood cells were fluorescent afterl-DOPA loading, and this FIF could be greatly diminished by the DOPA decarboxylase inhibitor RO4-4602. The pattern of FIF in the axial structures (neural tube and notochord) correlated with axial flexure in both position and time, and the intensity of fluorescence was strongest cranially and caudally, where flexure is most pronounced. The FIF in gut mesenchyme cells was closely related to the movement of the intestinal protals during early gut tube formation, and to the regions of the developing intestine that undergo intense morphogenesis during their early formation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 173 (2000), S. 57-66 
    ISSN: 1432-1424
    Keywords: Key words: Bladder — Smooth muscle cells — MaxiK channels — NS1608 — Hyperpolarization — Muscle relaxation — Urge incontinence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Using the patch-clamp technique, we have characterized membrane currents in single detrusor smooth muscle cells from rat and human urinary bladder. From the voltage- and Ca2+-dependence of the current as well as the single channel conductance we conclude that rat and human urinary bladder smooth muscle cells express MaxiK channels. In smooth muscle cells from rat urinary bladder we tested the action of NS1608 on current through these MaxiK channels. Application of 10 μm NS1608 increased the amplitude of the current and this increase could be explained by a shift in the activation voltage of the MaxiK channels ∼100 mV towards more negative potentials. Charybdotoxin as well as paxilline, well known blockers of MaxiK channels, were able to reduce current through MaxiK channels in our cell preparation. In addition, application of 10 μm NS1608 hyperpolarized the membrane potential of the investigated cells. This hyperpolarization could be antagonized by the application of paxilline. We conclude that application of NS1608 results in the opening of MaxiK channels under physiological conditions that leads to a hyperpolarization of the cells. This hyperpolarization in turn could relax urinary bladder smooth muscle cells. MaxiK channels in these cells could therefore play a role in directly controlling muscle tone by regulating the membrane potential. This opens up the possibility of MaxiK channels being targets for the treatment of urge incontinence.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 33 (1977), S. 1513-1514 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A procedure for the rapid freezing of whole chick embryos for histochemical treatment is described. The problems of deformation during preparation for quenching and orientation for sectioning have been largely overcome by placing embryos inside lengths of chicken trachea. The subsequenct disorientation of tissues that follows cracking and shattering due to the rapid freezing of whole embryos is avoided. The method permitted a more precise identification of the position and time of appearance of formaldehyde-induced fluorescence and myosin antibody immunofluorescence in serially sectioned embryos.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1912
    Keywords: Pinacidil ; K+-channels ; Membrane potential ; Ion flux ; Blood vessels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In rat aorta and rat portal vein, (−)- and (+)-pinacidil each produced a concentration-dependent inhibition of tension development. Although the (−) isomer was the more potent, concentration effect curves for each isomer were steep with similar slopes. In rat portal vein, tetraethylammonium and procaine antagonised the relaxant effect of (±)-pinacidil, whereas 3,4-diamino-pyridine was without effect. Intracellular microelectrode recording in rat portal vein showed that low concentrations of (±)-pinacidil reduced the duration of multispike electrical complexes. In both rat aorta and rat portal vein, higher concentrations of (±)-pinacidil hyperpolarised the membrane towards the potassium equilibrium potential. (±)-Pinacidil increased 86Rb efflux from rat aorta and rat portal vein in a concentration dependent manner. In a separate study, (±)-pinacidil increased 42K efflux from rat portal vein. (±)-Pinacidil had no effect on cyclic GMP or cyclic AMP levels in rat aorta. It is concluded that pinacidil opens 86Rb-permeable potassium channels in rat aorta and rat portal vein. This mechanism is independent of cyclic nucleotide changes and may be responsible for the antihypertensive effect of pinacidil.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-2665
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0878
    Keywords: Key words Protein phosphorylation ; Protein kinase-C ; Neural crest ; Cell migration ; Cell invasion ; Second messengers ; Quail (Coturnix coturnix japonica)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Epithelio-mesenchymal transition, which involves the re-organisation of cell-cell adhesion molecules and the actin cytoskeleton, can be induced in embryonic neural epithelium in vitro by protein kinase-C inhibitors. A non-inhibitory analogue, BIM V, and potent inhibitors of other kinases are not active. This suggests a central role for C-kinases, although the powerful specific C-kinase inhibitors BIM I and Ro 31–8220 show lower than expected activity. Co-inhibition by several kinases is unlikely to account for this, since no potentiation occurs when these are combined with potent inhibitors of other kinases. BIM I and Ro 31–8220 strongly inhibit only conventional calcium-regulated C-kinases; this and the lack of effect of TMB-8, which inhibits calcium release, suggests that novel and/or atypical isoforms are involved. Various potentiators and activators of conventional and novel C-kinases have no obvious effect alone and fail to reduce the effect of staurosporine, suggesting that atypical C-kinases are critical. The presence of C-kinase isoforms in the E2 embryonic neural tissues has been probed on Western blots, revealing immunoreactivity for the atypical isoforms ι (or λ) and ζ and the α, γ, ɛ and μ isoforms. Immunofluorecent localisation on sections of embryos has shown the widespread distribution of conventional and novel isoforms but only the atypical isoforms λ and ζ are enriched at the apical margins of the neural and other epithelia; they overlap with the cell-cell adhesion molecule N-cadherin and with F-actin. Thus, epithelio-mesenchymal transition in the embryonic neural epithelium in vitro is induced by inhibiting protein kinase activity, probably via an atypical protein kinase-C; atypical protein kinase-C isoforms are present in the tissue at the appropriate developmental stage and subcellular site in cells capable of epithelio-mesenchymal transition.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 244 (1986), S. 299-313 
    ISSN: 1432-0878
    Keywords: Sclerotome ; Neural crest ; Notochord ; Extracellular material ; Avian development ; Quail ; Chick
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution of sclerotome and neural crest cells of avian embryos was studied by light and electron microscopy. Sclerotome cells radiated from the somites towards the notochord, to occupy the perichordal space. Neural crest cells, at least initially, also entered cell-free spaces. At the cranial somitic levels they moved chiefly dorsal to the somites, favouring the rostral part of each somite. These cells did not approach the perichordal space. More caudally (i.e. trunk levels), neural crest cells initially moved ventrally between the somites and neural tube. Adjacent to the caudal half of each somite, these cells penetrated no further than the myosclerotomal border, but opposite the rostral somite half, they were found next to the sclerotome almost as far ventrally as the notochord. However, they did not appear to enter the perichordal space, in contrast to sclerotome cells. When tested in vitro, sclerotome cells migrated towards notochords co-cultured on fibronectin-rich extracellular material, and on collagen gels. In contrast, neural crest cells avoided co-cultured notochords. This avoidance was abolished by inclusion of testicular hyaluronidase and chondroitinase ABC in the culture medium, but not by hyaluronidase from Streptomyces hyalurolyticus. The results suggest that sclerotome and neural crest mesenchyme cells have a different distribution with respect to the notochord, and that differential responses to notochordal extracellular material, possibly chondroitin sulphate proteoglycan, may be responsible for this.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 239 (1985), S. 329-336 
    ISSN: 1432-0878
    Keywords: Epithelio-mesenchymal transformation ; Cell migration ; Neural crest ; Cell-cell adhesion ; Calcium Quail (Coturnix coturnix japonica)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary To investigate the control of the timing in the epithelio-mesenchymal transformation of the neural crest into a migrating population, neural anlagen (neural tube plus crest) were isolated from 2-day quail embryos by proteases in the presence of Ca+ + and explanted onto substrates favourable for neural crest cell migration. Explants isolated before normal migration had commenced required 3–8 h in vitro before neural crest cells started migration, but explants obtained at migratory stages showed an immediate onset of migration. The schedule was similar to that expected in vivo. When pre-migratory neural anlagen were isolated by protease in Ca+ +- and Mg+ +-free (CMF) medium, or when the protease was followed by a brief (5 min) exposure to CMF medium, neural crest cell migration commenced without delay, and the cohesion of the anlagen was impaired. Ca+ +-free medium duplicated the effects of CMF, but neither Mg+ +-free medium nor CMF treatment before treatment with protease stimulated migration and reduced cohesion. Precocious neural crest cell migration and reduced cohesion also followed when neural anlagen of pre-migratory stages were cultured with membrane. Ca+ +-channel antagonists D600 and Nifedipine, without any exernal Ca+ +-depletion. The decrease of cohesion of these tissues is consistent with results in other systems where protease/Ca+ +-depletion inactivates Ca+ +-dependent cell-cell adhesive mechanisms. Therefore, we suggest that Ca+ +-dependent cell-cell adhesions play a part in preventing neural crest cells from migrating precociously and that the timed inactivation of this adhesion system normally helps trigger the onset of migration. The results with blockers of Ca+ +-channels suggest that Ca+ + levels may be involved in regulating this system.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-0878
    Keywords: Neural crest ; Autonomic neurons ; Differentiation ; Fowl embryo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Sympathetic cells (adrenergic neurons, SIF cells and chromaffin cells) and enteric neurons differentiate from migratory cells derived from the neural crest. The development of these cell types was studied in chorio-allantoic membrane (CAM) grafts, using combinations of tissues from domestic fowl embryos. Neural anlagen (neural tube and crest) of the vagal, cervico-thoracic and lumbo-sacral axial levels were equally capable of sympathetic differentiation, but this required somitic tissue for its significant expression. However, the vagal somites possessed only slight sympathogenic activity, thereby accounting for the negligible contribution of the vagal neural crest to the sympathetic nervous system. The same three levels of the neural anlage could furnish enteric neurons when combined directly with the aneuronal colo-rectum. However, the scale of this line of differentiation varied with the level of origin of the neural anlage, in contrast to the apparent equivalence in the ability to diffentiate as sympathetic cells. The density of enteric neurons in combinations with the vagal neural anlage was estimated as 60 times greater than the neuron density in combinations with the cervico-thoracic neural anlage. The lumbo-sacral neural anlage gave results similar to those of the cervico-thoracic level. Moreover, neural crest-derived pigment cells, positioned ectopically in the wall of the colo-rectum, were rare in combinations with the vagal neural anlage, but common in grafts with the other levels. When tested physiologically, the colo-rectum grown with the vagal neural anlage showed non-adrenergic, non-cholinergic inhibitory nervous activity in addition to the expected cholinergic excitatory responses. The neurons derived directly from vagal neural anlagen were similar to those that had reached the colo-rectum via their normal migratory pathways, when studied in terms of histological appearance, density of distribution and physiological responses.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 203 (1979), S. 115-140 
    ISSN: 1432-0878
    Keywords: Neural crest ; Tissue culture ; Cell locomotion ; Chick embryo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Neural primordia of chick embryos were cultured for three days and the behaviour of migrating neural crest cells studied. Somite cells were used as a comparison. Crest cells were actively multipolar with narrow projections which extended and retracted rapidly, contrasting to the gradual extension of somite-cell lamellae. On losing cell contact, somite cells were also more directionally persistent. The rate of displacement of isolated crest cells was particularly low when calculated over a long time base. Both crest and somite cells were monolayered; contact paralysis occurred in somite cell collisions but was not ascertained for crest cells. However, crest cells in a population were far more directionally persistent than isolated cells. Contact duration between crest cells increased with time and they formed an open network. Eventually, retraction clumping occurred, initially and chiefly at the periphery of the crest outgrowth. Crest cells did not invade cultured embryonic mesenchymal or epithelial populations but endoderm underlapped them. No effects were observed on crest cells prior to direct contact. Substrate previously occupied by endoderm or ectoderm caused crest cells to flatten while substrate previously occupied by the neural tube caused them to round up and clump prematurely.
    Type of Medium: Electronic Resource
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