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  • 21
    Electronic Resource
    Electronic Resource
    Periodisch auftretende Querstrukturen in Nervenfasern des Bulbus olfactorius der ElritzePhoxinus laevis (1970)
    Springer
    Cellular and molecular life sciences 26 (1970), S. 1349-1350 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Nerve fibers in the olfactory bulb of the minnow with a mean diameter of 1.5 μm contain transversally arranged membranous septa with a periodicity of approximately 1 μm. These profiles are fenestrated by pores, each of them being occupied by a neurotubulus. The septa are connected by longitudinally arranged membranous tubuli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02113024
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  • 22
    Electronic Resource
    Electronic Resource
    Tuberculin and dinitrochlorobenzene (DNCB) tests in cancer patients before and after cytostatic drug therapy (1978)
    Springer
    Journal of molecular medicine 56 (1978), S. 905-909 
    Details
    ISSN: 1432-1440
    Keywords: Tuberkulin-Test, Dinitrochlorbenzoltest ; Zytostatische Therapie ; Solide Karzinome ; Zelluläre Immunität ; Tuberculin test ; DNCB test ; Cytostatic drug therapy ; Cancer patients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In 137 patients with different kinds of cancer and different cancer stage, cell-mediated immunity was investigated by DNCB (dinitrochlorobenzene) and tuberculin test. These two skin tests were performed before and after cytostatic drug combination therapy. For a collective of cancer patients we found a positive correlation between skin reactions and prognosis and a negative correlation between skin reactions and cancer stage. After cytostatic drug therapy skin reactions could be significantly stronger. This could be observed in 50% when one test was positive before chemotherapy and in only 20% when both tests were negative before chemotherapy. There existed a significant correlation between an increased reaction after cytostatic drug therapy and objective tumor regression. When skin reactions decreased, tumor progression was seen in all cases. Due to these observations we use skin reactions as a good parameter for therapy results. When delayed cutaneous hypersensitivity impairs 2–3 weeks after chemotherapy, we then change the cytostatic drug combination immediately. We cannot say at this moment, whether an improvement of cytostatic drug therapy can be reached in this way.
    Notes: Zusammenfassung Bei 137 Patienten mit unterschiedlichen soliden Karzinomen und verschiedenem Tumorstadium wurde die zelluläre Immunität durch Tuberkulin- und DNCB-(Dinitrochlorbenzol)-Test untersucht. Die Tests wurden vor und nach zytostatischer Stoßtherapie durchgeführt. Insgesamt fanden wir eine positive Korrelation zwischen Hauttests und Prognose und eine negative Korrelation zwischen Hauttests und Tumorstadium. Wenn mindestens ein Test vor Chemotherapie positiv war, konnten wir in ca. 50% eine Verbesserung der zellulären Immunität registrieren, dagegen nur in 20%, wenn beide Tests vor zytostatischer Therapie negativ waren. Ein signifikanter Zusammenhang zwischen verbesserter Reaktion auf Tuberkulin und/oder DNCB nach zytostatischer Therapie und objektiver Tumorrückbildung wurde beobachtet. Wenn beide Reaktionen schwächer wurden, folgteimmer eine Tumorprogression. Aufgrund dieser Beobachtungen verwenden wir die Hauttests als wertvollen Parameter für den Therapieerfolg. Wir wechseln daher sofort die Zytostatikakombination, wenn 2–3 Wochen nach Chemotherapie die Hautreaktionen schwächer werden. Ob hierdurch eine Verbesserung der Zytostatikatherapie möglich ist, kann derzeit noch nicht sicher gesagt werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01489216
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  • 23
    Electronic Resource
    Electronic Resource
    A chromatophore system in the hermatypic, deep-water coral Leptoseris fragilis (Anthozoa: Hexacorallia) (1985)
    Springer
    Marine biology 89 (1985), S. 143-147 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ultrastructural evidence is presented of a chromatophoresystem in the zooxanthellae containing hermatypic, deep-water coral Leptoseris fragilis (Milne Edwards and Haime). It consists of multilobed cells which mainly occupy the intercellular space of the oral gastrodermis. The cellular processes are filled with electron-dense granules up to 1-μm-long and 0.5-μm-wide. Within the cytoplasm an elaborate system of microtubules is established. The ramifications of the pigment cells, containing the pigment granules, form a dense and nearly continuous layer close to the overlying zooxanthellae. It is speculated that host pigments may transform the violet portion of the incident light into longer wavelengths, thus increasing the photosynthetic efficiency of the zooxanthellae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392885
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  • 24
    Electronic Resource
    Electronic Resource
    Peculiarities of innervation in chromatophore muscle cells ofLoligo vulgaris (1973)
    Springer
    Marine biology 19 (1973), S. 224-226 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The contractile cortex in muscle cells of the large brown chromatophore organs inLoligo vulgaris features a small open slit in its proximal portion. The slit accommodates a nerve fiber, penetrating into the central core of the muscle cell. The functional properties of the fiber, in relation to the contraction of the muscle cell, are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02097142
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  • 25
    Electronic Resource
    Electronic Resource
    Endogenous Ion Channels in Oocytes of Xenopus laevis: Recent Developments (1999)
    Springer
    The journal of membrane biology 170 (1999), S. 1-12 
    Details
    ISSN: 1432-1424
    Keywords: Key words:Xenopus laevis oocyte — Endogenous ion channels — Ion transport — Membrane transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002329900532
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  • 26
    Electronic Resource
    Electronic Resource
    Endogenousd-glucose transport in oocytes ofXenopus laevis (1989)
    Springer
    The journal of membrane biology 111 (1989), S. 93-102 
    Details
    ISSN: 1432-1424
    Keywords: Xenopus oocyte ; glucose ; cotransport ; flux ; voltage clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Endogenous glucose uptake by the oocytes ofXenopus laevis consists of two distinct components: one that is independent of extracellular Na+, and the other one that represents Na+-glucose cotransport. The latter shows similar characteristics as 2 Na+-1 glucose cotransport of epithelial cells: The similarities include the dependencies on external concentrations of Na+, glucose, and phlorizin, and on pH. As in epithelial cells, the glucose uptake in oocytes can also be stimulated by lanthanides. Both the electrogenic cotransport and the inhibition by phlorizin are voltage-dependent; the data are compatible with the assumption that the membrane potential acts as a driving force for the reaction cycle of the transport process. In particular, hyperpolarization seems to stimulat transport by recruitment of substrate binding sites to the outer membrane surface. The results described pertain to oocytes arrested in the prophase of the first meiotic division; maturation of the oocytes leads to a downregulation of both the Na+-independent and the Na+-dependent transport systems. The effect on the Na+-dependent cotransport is the consequence of a change of driving force due to membrane depolarization associated with the maturation process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869212
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  • 27
    Electronic Resource
    Electronic Resource
    Further Characteristics of the Ca2+-inactivated Cl− Channel in Xenopus laevis Oocytes (1999)
    Springer
    The journal of membrane biology 172 (1999), S. 169-179 
    Details
    ISSN: 1432-1424
    Keywords: Key words: Ca2+-inactivated Cl− channel — Inhibition profile — Capacitance measurements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Removal of extracellular Ca2+ activates ion channels in the plasma membrane of defolliculated oocytes of the South Africa clawed toad Xenopus laevis. At present, there is controversy about the nature of the Ca2+-inactivated ion channels. Recently, we identified one of these channels as a Ca2+-inactivated Cl− channel (CaIC) using single channel analysis. In this work we confirm and extend previous observations on the CaIC by presenting a decisive extension of the regulation and inhibition profile. CaIC current is reversibly blocked by the divalent and trivalent cations Zn2+ (half-maximal blocker concentration, K1/2= 8 μm), Cu2+ (K1/2= 120 μm) and Gd3+ (K1/2= 20 μm). Furthermore, CaIC is inhibited by the specific Cl− channel blocker NPPB (K1/2≈ 3 μm). Interestingly, CaIC-mediated currents are further sensitive to the cation channel inhibitor amiloride (500 μm) but insensitive to its high affinity analogue benzamil (100 μm). An investigation of the pH-dependence of the CaIC revealed a reduction of currents in the acidic range. Using simultaneous measurements of membrane current (I m ), conductance (G m ) and capacitance (C m ) we demonstrate that Ca2+ removal leads to instant activation of CaIC already present in the plasma membrane. Since C m remains constant upon Ca2+ depletion while I m and G m increase drastically, no exocytotic transport of CaIC from intracellular pools and functional insertion into the plasma membrane is involved in the large CaIC currents. A detailed overview of applicable blockers is given. These blockers are useful when oocytes are utilized as an expression system for foreign proteins whose investigations require Ca2+-free solutions and disturbances by CaIC currents are unwanted. We further compare and discuss our results with data of Ca2+-inactivated cation channels reported by other groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002329900594
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  • 28
    Electronic Resource
    Electronic Resource
    The Ca2+-induced leak current in Xenopus oocytes is indeed mediated through a Cl− channel (1995)
    Springer
    The journal of membrane biology 148 (1995), S. 263-275 
    Details
    ISSN: 1432-1424
    Keywords: Xenopus oocytes ; Cl− channel ; Divalent cations ; Leak current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Defolliculated oocytes of Xenopus laevis responded to removal of external divalent cations with large depolarizations and, when voltage clamped, with huge currents. Single channel analysis revealed a Cl− channel with a slope conductance of about 90 pS at positive membrane potentials with at least four substates. Single channel amplitudes and mean channel currents had a reversal potential of approximately −15 mV as predicted by the Nernst equation for a channel perfectly selective for Cl−. Readdition of Ca2+ immediately inactivated the channel and restored the former membrane potential or clamp current. The inward currents were mediated by a Ca2+ inactivated Cl− channel (CaIC). The inhibitory potency of Ca2+ was a function of the external Ca2+ concentration with a half maximal blocker concentration of about 20 μm. These channels were inhibited by the Cl− channel blockers flufenamic acid, niflumic acid and diphenylamine-2-carboxylate (DPC). In contrast, 4,4′-acetamido-4′-isothiocyanatostilbene-2,2′-disulfonicacid (SITS), another Cl− channel blocker, led to activation of this Cl− channel. Like other Cl− channels, the CaIC was activated by cytosolic cAMP. Extracellular ATP inhibited the channel while ADP was without any effect. Injection of phorbol 12-myristate 13-acetate (PMA), a protein kinase C activating phorbol ester, stimulated the Cl− current. Cytochalasin D, an actin filament disrupting compound, reversibly decreased the clamp current demonstrating an influence of the cytoskeleton. The results indicate that removal of divalent cations activates Cl− channels in Xenopus oocytes which share several features with Cl− channels of the CLC family. The former so-called leak current of oocytes under divalent cation-free conditions is nothing else than an activation of Cl− channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235044
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  • 29
    Electronic Resource
    Electronic Resource
    The Ca2+-inactivated Cl− Channel at Work: Selectivity, Blocker Kinetics and Transport Visualization (1997)
    Springer
    The journal of membrane biology 155 (1997), S. 95 -104 
    Details
    ISSN: 1432-1424
    Keywords: Key words:Xenopus oocytes — Cl− channel — Calcium — Selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Removal of extracellular divalent cations activated a Cl− channel in the plasma membrane of Xenopus laevis oocytes. This so-called Ca2+-inactivated Cl− channel (CaIC) was present in every oocyte and was investigated using two-electrode whole-cell voltage clamp and single-channel patch-clamp techniques. Beside other Cl− channel inhibitors, anthracene-9-carboxylic acid (9-AC) and 3′azido-3′deoxythymidine (AZT), a nucleoside analogue commonly used as an antiviral drug, blocked at least partly the CalC-mediated currents. Using the Cl−-sensitive dye 6-methoxy-N-(sulfopropyl)quinolinium (SPQ) we could visualize the transport of Cl− from the oocyte cytoplasm to the surrounding medium after activation of the CaIC by Ca2+ removal. In the absence of external Cl− and Ca2+, the emission intensity of SPQ declined continuously, indicating a quenching of fluorescence by the efflux of Cl− in the millimolar range. In the presence of external Ca2+, no emission changes could be observed during the same time period. Chelating external Ca2+ in absence of Cl− immediately activated Ca2+-inactivated Cl− channels leading to subsequent emission decrease of SPQ. Investigations on the selectivity of the CaIC revealed only poor discrimination between different anions. With single-channel measurements, we found an anion selectivity sequence I− 〉 Br− 〉 Cl−≫ gluconate as it is also typical for maxi Cl− channels. Contrary to the majority of all other transport systems of the Xenopus oocyte, which show reduced activity due to membrane depolarization or endocytotic removal of the transport protein from the plasma membrane during oocyte maturation, the CaIC remained active in maturated oocytes. Single-channel measurements on maturated oocytes, also known as eggs, showed the presence of Ca2+-inactivated Cl− channels. However, this egg CaIC revealed an altered sensitivity to external Ca2+ concentrations. All these data confirm and extend our previous observations on the CaIC and give clear evidence that this channel is peculiar among all Cl− channels described up to now.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002329900161
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  • 30
    Electronic Resource
    Electronic Resource
    Transport of Charged Dipeptides by the Intestinal H+/Peptide Symporter PepT1 Expressed in Xenopus laevis Oocytes (1997)
    Springer
    The journal of membrane biology 155 (1997), S. 247 -256 
    Details
    ISSN: 1432-1424
    Keywords: Key words: Intestinal peptide transporter — Expression — Substrate specificity — Two-electrode voltage-clamp technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. The cloned intestinal peptide transporter is capable of electrogenic H+-coupled cotransport of neutral di- and tripeptides and selected peptide mimetics. Since the mechanism by which PepT1 transports substrates that carry a net negative or positive charge at neutral pH is poorly understood, we determined in Xenopus oocytes expressing PepT1 the characteristics of transport of differently charged glycylpeptides. Transport function of PepT1 was assessed by flux studies employing a radiolabeled dipeptide and by the two-electrode voltage-clamp-technique. Our studies show, that the transporter is capable of translocating all substrates by an electrogenic process that follows Michaelis Menten kinetics. Whereas the apparent K0.5 value of a zwitterionic substrate is only moderately affected by alterations in pH or membrane potential, K0.5 values of charged substrates are strongly dependent on both, pH and membrane potential. Whereas the affinity of the anionic dipeptide increased dramatically by lowering the pH, a cationic substrate shows only a weak affinity for PepT1 at all pH values (5.5–8.0). The driving force for uptake is provided mainly by the inside negative transmembrane electrical potential. In addition, affinity for proton interaction with PepT1 was found to depend on membrane potential and proton binding subsequently affects the substrate affinity. Furthermore, our studies suggest, that uptake of the zwitterionic form of a charged substrate contributes to overall transport and that consequently the stoichiometry of the flux-coupling ratios for peptide: H+/H3O+ cotransport may vary depending on pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002329900177
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