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  • Chemistry  (10)
  • Macrocyst  (2)
  • Sexual development  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Involvement of cytoplasmic pH in the production of ethylene, a potent inducer of sexual development inDictyostelium mucoroides (1991)
    Springer
    Protoplasma 160 (1991), S. 72-76 
    Details
    ISSN: 1615-6102
    Keywords: Dictyostelium mucoroides ; Cellular slime mold ; Cytoplasmic pH ; Ethylene ; Cyclic AMP ; Sexual development ; Macrocyst ; Sorocarp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Dictyostelium mucoroides-7 (Dm 7) and a mutant MF 1 derived from it exhibit two developmental pathways: sorocarp formation occurs during the asexual process, and macrocyst formation during the sexual cycle. The two developmental pathways are mainly regulated by two chemical substances: 3′,5′-cyclic adenosine monophosphate (cAMP) and ethylene. Recently, we have demonstrated that cytoplasmic pH (pHi) has a critical role for the choice of developmental pathways, higher pHi being favourable to macrocyst formation. Thereupon, attention was riveted to the relation of pHi to biosynthesis of cAMP and ethylene. Effect of pHi on the production and release of ethylene, a potent inducer of macrocyst formation, was examined, using the two facing culture method. The result showed that lowered pHi inhibits ethylene production, thus resulting in a failure of cells to form macrocysts. The accumulation of cAMP, an inhibitor of macrocyst formation, was found to vary depending on extracellular pH (pHo), but diethylstilbestrol (DES) that is a proton pump inhibitor and also an inhibitor of macrocyst formation had no significant effect on the accumulation. Taken together these results indicate that higher pHi may induce macrocyst formation through enhancement of ethylene production rather than inhibition of cAMP synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01539958
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  • 2
    Electronic Resource
    Electronic Resource
    Separation of water-ethanol by pervaporation through polyion complex composite membranePaper presented at 3rd International Conference on Pervaporation Processes in the Chemical Industry, September 1922, Nancy, France. (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 3229-3239 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: For the purpose of separating alcohol-water mixtures by the use of the pervaporation technique, new composite membranes composed of polyion complexes (PIC) as a separating layer were developed. The polyion complex structure, consisting of polyacrylic acid (PAA) and polycation, provided excellent permeation rate and selectivity. Among the polycations, ionenes, which have quaternary ammonium groups in the backbone chain, were effective in giving membranes of higher permselectivities. High selectivity of PIC membranes was observed at high ethanol concentration regions in the feed mixture. For the azeotropic mixture of water/ethanol (95 wt % EtOH) at 60°C, the PAA-based PIC membrane had the following separation properties: separation factor ∼ 3,500 and permeation rate ∼ 1.6 kg/m2 h.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070421216
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  • 3
    Electronic Resource
    Electronic Resource
    The ethylene action in the development of cellular slime molds: an analogy to higher plants (1992)
    Springer
    Protoplasma 167 (1992), S. 159-168 
    Details
    ISSN: 1615-6102
    Keywords: Dictyostelium mucoroides ; Ethylene ; Sexual development ; Macrocyst ; Sorocarp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The cellular slime moldDictyostelium mucoroides-7 (Dm 7) and its mutant (MF 1) exhibit sexual or asexual development depending upon culture conditions. During the sexual cycle macrocyst formation occurs, whereas sorocarps containing spores and stalk cells are asexually formed. As previously reported, the macrocyst formation is marked by the emergence of true zygotes, and is induced by a potent plant hormone, ethylene. The concentration of ethylene required for macrocyst induction was determined to establish the similarity of ethylene action between this organism and higher plants. Macrocysts are induced by low (1 μl/l) exogenous concentrations of ethylene. Higher concentrations (10–1,000 ul/l) also gave essentially the same inductive activity. Ethionine, an analogue of methionine, was found to inhibit zygote formation during sexual development through its interference with ethylene production by Dm 7 and MF 1 cells. In fact, the inhibitory effect of ethionine was mostly nullified by the application of ethylene, S-adenosyl-L-methionine, or 1-aminocyclopropane-1-carboxylic acid. Taken together these results suggest that both the effective concentration of ethylene and the pathway of ethylene biosynthesis inD. mucoroides may be similar to those in higher plants. Ethylene was also found to be produced in various species and strains of cellular slime molds, even during the asexual process. The possible functions of ethylene in the asexual development are discussed in relation to cell aggregation and differentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01403379
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  • 4
    Electronic Resource
    Electronic Resource
    Gas and vapor sorption in polymers just below Tg (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 4019-4029 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Generally, sorption isotherms for gases like CO2 in glassy polymers are concave to the pressure axis, whereas in the rubbery state these isotherms are linear for gases or sometimes convex to the pressure axis for more condensable vapors. Examples of CO2 isotherms are reported here that show at low pressure the curvature characteristic of glasses and then become linear at higher pressures. This is observed when the glass transition temperature Tg is not much greater than the observation temperature T, and plasticization of the polymer by sorbed CO2 causes Tg to become equal to T within the range of pressures employed in the isotherm measurement. For the sorption of vapors in glassy polymers, this can lead to sigmoidal isotherms, as discussed using an illustration from the literature.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1985.070301006
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  • 5
    Electronic Resource
    Electronic Resource
    Gas permeation in polyethersulfone (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 33 (1987), S. 1823-1828 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1987.070330533
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  • 6
    Electronic Resource
    Electronic Resource
    Eisen(II)-Verbindungen von Imidazolen (1976)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 426 (1976), S. 198-204 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Iron(II) Compounds of ImidazolesThe reaction of ferrocene and cyclopentadienyl dicarbonyl with imidazole, 2-methyl-, 2-ethyl- and 2-phenyl-imidazole yields iron(II) derivatives of these heterocyclic compounds, which have been investigated by thermogravimetry and Mössbauer spectroscopy. The derivative of the substituted imidazoles have the expected composition and contain fourfold coordinated iron. The reaction with unsubstituted imidazole yields the compound Fe(N2C3H3) · 0,71 N2C3H4 with fourfold as well as sixfold coordinated metal ions.
    Notes: Durch Umsetzung von Ferroccn und Cyclopentadienyleisendicarbonyl mit Imidazol, 2-Methyl-, 2-Äthyl- und 2-Phenylimidazol konnten die Eisen(II)-Derivate dieser Heterocyclen dargestellt werden. Die Verbindungen wurden thermogravimetrisch und Mössbauer-spektrometrisch untersucht. Die Derivate der substituierten Imidazole besitzen die erwartete Zusammensetzung Fe(N2C3H2R)2 (R = CH3, C2H5, C6H5) und vierfach koordiniertes Eisen. Die Umsetzung mit nicht substituiertem Imidazol ergibt eine Verbindung Fe(N2C3H3)2 · 0,71 N2C3H4, die sowohl vierfach als auch sechsfach koordinierte Metallionen enthält.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19764260209
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  • 7
    Electronic Resource
    Electronic Resource
    Determination of dual-mode sorption and mobility parameters from permeation experiments (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 24 (1986), S. 121-131 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The precise pressure dependence of apparent diffusion and permeation coefficients was measured by using a microcomputer system for collecting and treating permeation data for CO2 in glassy poly(ethylene terephthalate) below 1 atm between 15 and 40°C. The partial immobilization model was used to determine the dual-mode sorption and mobility parameters. The curves calculated with these parameters were in excellent agreement with experimental data. These parameters were also compared with sorption parameters obtained from measurements at 30°C. There was a small difference between the values of the parameters obtained from these permeation data and those from sorption data which we had previously obtained. Relations between this difference and the method of determination of the parameters are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1986.180240113
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of antiplasticization on gas sorption and transport. III. Free volume interpretation (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 1005-1016 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Previous papers have shown that antiplasticization of polysulfone and poly(phenylene oxide) by low molecular weight diluents is accompanied by substantial reductions in permeability to gases like helium, carbon dioxide, and methane because of reduced mobility in the glass. These effects are not explained even qualitatively by the extent of volume contraction on mixing for these mixtures. However, as shown here, a simple free volume treatment provides an excellent correlation of these effects. Free volume was computed from measured specific volume and an estimate of the volume at the absolute zero of temperature of the material from a group contribution method. Application of this approach to the mechanical stiffening associated with antiplasticization is suggested. The basis and limitations of this analysis are discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1987.090250503
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of antiplasticization on gas sorption and transport. I. Polysulfone (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 957-980 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The addition of tricresyl phosphate, N-phenyl-2-naphthylamine, and 4,4′-dichlorodiphenyl sulfone to polysulfone causes changes in thermal and mechanical properties of the glassy mixtures associated with antiplasticization, i.e., reduction in glass transition temperature and increase in stiffness. These changes are also found to be accompanied by reductions in sorption of carbon dioxide and the permeability coefficients for helium, carbon dioxide, and methane at low diluent concentrations with reversal of these trends at higher levels as also occurs for the mechanical properties. Detailed analyses of data for carbon dioxide are given in terms of the dual sorption and mobility models often used for glassy polymers. The mobility for gas transport was found to decrease with diluent addition. The major cause for the decreased sorption is the reduction in glass transition temperature accompanying addition of the diluents. The changes in transport behavior approximately parallel the changes in mechanical behavior. These trends are not even qualitatively correlated with estimates of the excess volume changes associated with addition of the diluents to polysulfone.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1987.090250501
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of antiplasticization on gas sorption and transport. II. Poly(phenylene oxide) (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 981-1003 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The propensity for various diluents to cause antiplasticization of poly(phenylene oxide) was examined and compared with similar responses for polysufone. Of the diluents used, none resulted in significant stiffening of poly(phenylene oxide) at 35°C relative to what was observed for polysulfone in an earlier paper. However, these diluents did cause substantial reduction in gas sorption levels and permeability coefficients. The latter is consequently a more sensitive indicator of changes in molecular motions of glassy polymers caused by diluents. The permeability response of adding low molecular weight diluents is compared with that of adding a high molecular weight polymer, polystyrene, to poly(phenylene oxide). The data were analyzed and interpreted along lines used in the companion paper for polysulfone.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1987.090250502
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