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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 100 (1979), S. 33-43 
    ISSN: 1615-6102
    Keywords: Amoeba proteus ; Ca++-binding sites ; Cytochemical demonstration ; Induced pinocytosis ; Plasma membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Different methods were used to demonstrate the existence of Ca++-binding sites (Ca++-bs) at the plasma membrane ofAmoeba proteus. In pinocytoting animals the number (indicated by the average distanced in nm) and size (average longitudinal axiss in nm) of Ca++-bs at the cytoplasmic surface of the cell membrane were significantly increased (d=162±15;n=41 ands=93±5;n=47) in comparison to controls (d=208 ±21;n=37 ands=59±8;n=45). The ratio of P: Ca obtained by X-ray microanalysis was in the range of 1.5. The differences observed in the two experimental groups of amoebae are explained by conformational changes in the molecular structure and an increased Ca++-permeability of the plasma membrane during induced pinocytosis. Microplasmodia of the acellular slime moldPhysarum polycephalum investigated for comparison were found to have no Ca++-bs at the interior cell surface.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 197 (1979), S. 263-279 
    ISSN: 1432-0878
    Keywords: Induced pinocytosis ; Dynamics ; Motive force generation ; Light and electron microscopy ; Amoeba proteus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The mechanism of induced pinocytosis was investigated in Amoeba proteus by light and electron microscopy. The application of nine different inducing substances revealed that pinocytotic channel formation, elongation, vesiculation, shortening and disappearance are the result of the successive or simultaneous action of both traction and pressure forces, which are produced by the contractile activity of a plasma membrane-associated layer of filaments ranging from a few hundred nm to several μ in thickness. The initial phase of channel formation is caused by traction forces according to the membrane flow concept, whereas channel elongation and vesiculation mainly result from pressure forces in conjunction with the extrusion of small hyaline pseudopodia. Shortening and disappearance of the pinocytotic channels are brought about by local contractions of the cortical filament layer in the basal region of the hyaline pseudopodia. Experiments using latex beads as marker particles together with inducing substances show that a rapid membrane turnover during pinocytosis can be excluded, and that the plasma membrane slides as an entire structure over the underlying cytoplasm.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The lifetime of cation selective carrier-PVC-membranes partially depends on the components' remaining in the membrane. An exchange of monomeric by polymeric plasticizers with low tendency to migrate lengthens the function time drastically. Other than for Na+ - and NH4+-selective membranes, it is essential for K+ - and Ca2+-selective membranes and optional for H+-selective membranes to incorporate lipophilic anions in order to make the phase transfer catalysis more efficient. The resistence to saponification of phthalic acid polyester gives H+-selective membranes a high stability of measured values even in the alkaline range.For anion selective PVC-membranes, instead of cation selective plasticizers the plasticizing qualities of a liquid charged ligand should be used.The tubular carrier-PVC-membranes of our ion selective flow through measuring systems are diffusion welded to the ends of two PVC-tubes [1] so that they are absolutely tight with no risk of potential leakage. Migration of the membrane components plasticizer and ionophore across this border as well as their extraction [2, 3] into the measuring solution [4] will naturally reduce the membrane's functionning time [5].
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituted Alkinyles as Axial Ligands at Hemine Like Bound Iron(III) - Incorporation into a Spectrochemical Series.Substituted lithium alkynyles Li—C≡C—R (R = tBu, Ph, p-Cl—C6H4, Me3Si, iPr3Si, Ph3Si) react with the hemine like macrocyclic iron(III) complex 6,13-di(ethoxycarbonyl)-5, 14-dimethyl-1, 4, 8, 11-tetraazatetradeca-4,6,12,14-tetraenato[2-]iron(III)-iodide (formula 2;) in tetrahydrofuran to form anionic low-spin di-adducts [fe(C≡C—R)2]-. The incorporation of the alkynyles into a spectrochemical series of the axial ligands (studied by the sharp equatorial-ligand-to-metal CT absorption band) results in the wavelength-sequence (nm): OH- (≍ 510) « N3- (≍ 625) 〈 tBu—C≡C- (664) 〈 NH3 (666) 〈 Ph—C≡C- (692) 〈 Ph—NH2 (695) 〈 Me3Si—C≡C- (698) 〈 SCN- (713) 〈 Ph3Si—C ≡ C- (716) 〈 CN- (739) 〈 4-picoline (759) 〈 pyridine (765) 〈 nicotinamide (776) 〈 methylnicotinat (788) 〈 pyrazine (798) and points to a significant π-acceptor ability of the silyl substituents.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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