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  • Electronic Resource  (7)
  • Chromatophores  (3)
  • 32.80.H  (2)
  • Benzamil  (2)
  • 1
    Electronic Resource
    Electronic Resource
    cAMP-activation of amiloride-sensitive Na+ channels from guinea-pig colon expressed in Xenopus oocytes (1996)
    Springer
    Pflügers Archiv 431 (1996), S. 913-922 
    Details
    ISSN: 1432-2013
    Keywords: Key wordsXenopus oocytes ; Guinea-pig colon ; Na+ channel ; Single-channel analysis ; Amiloride ; Benzamil ; cAMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Guinea-pig distal colonic mRNA injection into Xenopus laevis oocytes resulted in expression of functional active epithelial Na+ channels in the oocyte plasma membrane. Poly(A)+ RNA was extracted from distal colonic mucosa of animals fed either a high-salt (HS) or a low-salt (LS) diet. The electrophysiological properties of the expressed amiloride-sensitive Na+ conductances were investigated by conventional two-electrode voltage-clamp and patch-clamp measurements. Injection of poly(A)+ RNA from HS-fed animals [from hereon referred to as HS-poly(A)+ RNA] into oocytes induced the expression of amiloride-sensitive Na+ conductances. On the other hand, oocytes injected with poly(A)+ RNA from LS-fed animals [LS-poly(A)+ RNA] expressed a markedly larger amount of amiloride-blockable Na+ conductances. LS-poly(A)+ RNA-induced conductances were completely inhibitable by amiloride with a K i of 77 nM, and were also blocked by benzamil with a K i of 1.8 nM. 5-(N-Ethyl-N-isopropyl)-amiloride (EIPA), even in high doses (25 μM), had no detectable effect on the Na+ conductances. Expressed amiloride-sensitive Na+ channels could be further activated by cAMP leading to nearly doubled clamp currents. When Na+ was replaced by K+, amiloride (1 μM) showed no effect on the clamp current. Single-channel analysis revealed slow gating behaviour, open probabilities (P o) between 0.4 and 0.9, and slope conductances of 3.8 pS for Na+ and 5.6 pS for Li+. The expressed channels showed to be highly selective for Na+ over K+ with a permeability ratio P Na/P K 〉 20. Amiloride (500 nM) reduced channel P o to values 〈 0.05. All these features make the guinea-pig distal colon of LS-fed animals an interesting mRNA source for the expression of highly amiloride-sensitive Na+ channels in Xenopus oocytes, which could provide new insights in the regulatory mechanism of these channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050085
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  • 2
    Electronic Resource
    Electronic Resource
    Amöboid bewegliche Pigmentzellen im Epithel des Seeigels Centrostephanus longispinus (1972)
    Springer
    Cell & tissue research 133 (1972), S. 82-102 
    Details
    ISSN: 1432-0878
    Keywords: Echinoidea ; Colour change ; Chromatophores ; Amoeboid movement ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Für den physiologischen Farbwechsel bei Vertebraten und Evertebraten gilt die Vorstellung, daß eine Pigmentbewegung innerhalb einer formkonstanten Zelle stattfindet. Am Seeigel Centrostephanus longispinus wird nun der Nachweis einer amoeboiden Bewegung von Pigmentzellen geführt: Die Epidermis von Centrostephanus enthält große braune Chromatophoren, die bei Belichtung eine Pigmentdispersion, bei Verdunkelung eine Konzentration des Pigments zeigen. Die Chromatophoren sind außerordentlich stark verzweigte Zellen, deren Arme dicht mit Pigmentgrana erfüllt sind. Im geballten Zustand ist die allgemeine Zellform mehr oder weniger ovoid, wobei die Zellarme eingezogen und dicht um die Zellmitte angeordnet sind. Dispersion des Pigments wird hervorgerufen durch Ausstrecken der pigmentierten Zellarme in den Interzellularraum des umgebenden Gewebes. Innerhalb der Zelle werden filamentöse Elemente nachgewiesen, die vermutlich für die Zellbeweglichkeit verantwortlich sind. — Ferner wird der zelluläre Aufbau des Integuments beschrieben.
    Notes: Summary Rapid colour changes in vertebrate and invertebrate species are considered to be due to movement of pigment granules within pigment cells of constant shape. Evidence is presented in this study to show that an amoeboid movement of chromatophores occurs in the epidermis of the Echinoderm Centrostephanus longispinus. The epidermis in this species contains large brown chromatophores, which display a dispersion of pigment on illumination and its concentration on darkening. The chromatophores are extensively branched cells, and their branches are densely packed with pigment granules. In the state of pigment concentration, the shape of the cell is more or less ovoid, and the cell branches are drawn in and closely arranged around the cell centre. Dispersion is attained by a stretching out of the pigmented cell branches into the intercellular spaces of the surrounding tissue. Within the cell, filamentous elements, which may be functional in the motility of the pigment cell, can be demonstrated.—Additionally the cellular composition of the integument is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307069
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  • 3
    Electronic Resource
    Electronic Resource
    Light-induced alterations in cell shape and pigment displacement in chromatophores of the sea urchin Centrostephanus longispinus (1977)
    Springer
    Cell & tissue research 182 (1977), S. 165-176 
    Details
    ISSN: 1432-0878
    Keywords: Chromatophores ; Light-sensitivity ; Granule motion ; Echinoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Alterations in cell shape of the light-sensitive chromatophores of Centrostephanus longispinus are described. Upon illumination a centrifugal pigment movement starts within extremely thin filopodia which radiate from the cell body. With continued pigment migration the cellular processes increase in length and diameter and give the cell an irregular stellate appearance. Pigment movement within the cellular processes is discontinuous in space and time and may occur independently in single filopodia. The motion of single granules shows characteristic features of a saltatory movement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220586
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  • 4
    Electronic Resource
    Electronic Resource
    Ion transport across leech integument (1993)
    Springer
    Journal of comparative physiology 163 (1993), S. 153-159 
    Details
    ISSN: 1432-136X
    Keywords: Na+ channels ; Amiloride ; Benzamil ; Noise analysis ; Leech, Hirudo medicinalis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The dorsal skin of the leech Hirudo medicinalis was used for electrophysiological measurements performed in Ussing chambers. The leech skin is a tight epithelium (transepithelial resistance = 10.5±0.5 kΩ· cm-2) with an initial short-circuit current of 29.0±2.9 μA·cm-2. Removal of Na+ from the apical bath medium reduced short-circuit current about 55%. Ouabain (50μmol·l-1) added to the basolateral solution, depressed the short-circuit current completely. The Na+ current saturated at a concentration of 90 mmol Na+·l-1 in the apical solution (K M=11.2±1.8 mmol·l-1). Amiloride (100 μmol·l-1) on the apical side inhibited ca. 40% of the Na+ current and indicated the presence of Na+ channels. The dependence of Na+ current on the amiloride concentration followed Michaclis-Menten kinetics (K i=2.9±0.4 μmol·l-1). The amiloride analogue benzamil had a higher affinity to the Na+ channel (K i=0.7±0.2 μmol·l-1). Thus, Na+ channels in leech integument are less sensitive to amiloride than channels known from vertebrate epithelia. With 20 mmol Na+·l-1 in the mucosal solution the tissue showed an optimum amiloride-inhibitable current, and the amiloride-sensitive current under this condition was 86.8±2.3% of total short-circuit current. Higher Na+ concentrations lead to a decrease in amiloride-blockade short-circuit current. Sitmulation of the tissue with cyclic adenosine monophosphate (100 μmol·l-1) and isobutylmethylxanthine (1 mmol·l-1) nearly doubled short-circuit current and increased amiloride-sensitive Na+ currents by 50%. By current fluctuation analysis we estimated single Na+ channel current (2.7±0.9 pA) and Na+ channel density (3.6±0.6 channels·μm-2) under control conditions. After cyclic adenosine monophosphate stimulation Na+ channel density increased to 5.4±1.1 channels·μm-2, whereas single Na+ channel current showed no significant change (1.9±0.2 pA). These data present a detailed investigation of an invertebrate epithelial Na+ channel, and show the similarities and differences to vertebrate Na+ channels. Whereas the channel properties are different from the classical vertebrate Na+ channel, the regulation by cyclic adenosine monophosphate seems similar. Stimulation of Na+ uptake by cyclic adenosine monophosphate is mediated by an increasing number of Na+ channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00263601
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  • 5
    Electronic Resource
    Electronic Resource
    KL 2,3 ionization in neon by electron impact in the range 1.5–50 keV: cross sections and alignment (1990)
    Springer
    The European physical journal 16 (1990), S. 97-106 
    Details
    ISSN: 1434-6079
    Keywords: 34.80.D ; 32.80.H
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have measured the ratio of cross sections σ(KL 2,3)/σ(K) for neon for electron impact in the energy range ofE 0=1.5 ... 50 keV via the intensity ofKL 2,3−LLL 2,3 Auger satellite lines relative to the intensity ofKL 1 L 2,3 (3 P) diagram line. The experimental ratio decreases over the full range of energyE 0 which is contrary to an earlier result by Carlson et al. We have also measured the alignment ofKL 2,3 1 P and3 P states via the angular distribution of Auger satellite intensity for the energy rangeE 0=1.5 ... 4 keV, within experimental error we have found a zero alignment. The totalK Auger spectrum, measured forE 0=40 keV and at the magic angle of emission ϑ=54.7°, has been decomposed into its components by using appropriate line shapes distorted by postcollision interaction. Finally, we discussed whether the lines observed at the high-energy side ofKL 2,3−LLL 2,3 Auger satellite lines can be interpreted as structures caused by an angular momentum exchange in the postcollision interaction predicted by Niehaus and Zwakhals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01679570
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  • 6
    Electronic Resource
    Electronic Resource
    Alignment of double vacancy states (1s2p)−1 3 P and1 P of neon for electron impact ionization (1994)
    Springer
    The European physical journal 31 (1994), S. 53-54 
    Details
    ISSN: 1434-6079
    Keywords: 34.80.D ; 32.80.H
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract From intensity of Auger transitions (1s2p)−1 1 P,3 P→2p −3 2 P,2 D+e A − relative to 1s −1 2 S→2p −2 1 D+e A − measured at ϑ=54 and 90° relative to the primary electron beam we have determined the alignment of double vacancy states (1s 2p)−1 1 P and3 P of neon for electron impact ionization for the impact energies 1.5, 2.0, 2.5 and 4.0 keV. ForE 0=1.5, 2.0 and 2.5 keV the alignment is compatible with zero with an upper limit of , forE 0=4.0 keV a small negative value was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426578
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  • 7
    Electronic Resource
    Electronic Resource
    Ultrastructural observations on changes in cell shape in chromatophores of the sea urchin Centrostephanus longispinus (1980)
    Springer
    Cell & tissue research 206 (1980), S. 21-33 
    Details
    ISSN: 1432-0878
    Keywords: Chromatophores ; Light-sensitivity ; Alteration in cell shape ; Microtubules ; Echinoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Alterations in cell shape of the light-sensitive chromatophores of the sea urchin Centrostephanus longispinus were studied by scanning- and transmission electron microscopy. Transition of the aggregated to the dispersed state is accompanied by incorporation of vesicles into the membrane of the pigment cell. During dispersion a system of microtubules originating from centriole-like structures is established throughout the stellate cell. Within restricted areas of the cell, cytoplasmic differentiation and condensation is found. The possible functional significance of the findings is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233604
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