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  • 1
    ISSN: 1573-0603
    Keywords: Antrum ; Human gastrointestinal epithelium ; Polarized epithelial cells ; Spheroid-like vesicles ; Tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A novel procedure is described for the three-dimensional (3-D) in vitro culture and for maintaining of nontransformed gastric epithelial cells from the human antrum mucosa (HAEC). Biopsies obtained from the antrum were cut into small pieces and the tissue fragments were incubated in culture medium containing the appropriate antibiotics. The suspended mucosal fragments generated small, spheroid-like vesicles consisting of predominantly highly prismatic, mucus-producing cells which mimic the in vivo counterparts structurally and functionally. Electron microscopic investigations revealed a number of ultrastructural and morphological features similar to those of normal gastric cells in vivo such as apical microvilli associated with a glycocalyx, tight junctions, desmosomes, membraneous infoldings, mucous droplets, and an irregular basal lamina. In comparison to the two-dimensional (2-D) gastric cell cultures grown on plane supports, the vesicles maintain an intact epithelial organization of individual cells. The prismatic phenotype, the histophysiology as well as the cytoarchitecture of the non-transformed 3-D cultured gastric epithelial cells are comparable to those of the native tissue and therefore represent a suitable model for defined pathogen-host cell interactions.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-3904
    Keywords: biexponential kinetics ; proline helices ; substituted proline residues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of isomerization of the helical forms of three oligoprolines was determined by far-ultraviolet CD spectropolarimetry and kinetic analysis by singular value decomposition. ZRA (Pro3-X-Pro2-Y-Pro2-Z-Pro3) and ZRA2 (Pro7-X-Pro2-Y-Pro2-Z-Pro7) bear large redox-active substituents on proline residues X, Y, and Z, but P9 (Pro9) does not. All three peptides formed a stable proline-II helix in water. In acetonitrile, both ZRA2 and P9 were converted into a proline-I helical form but ZRA remained predominantly in the proline-II helical form. Evidently, in order to undergo substantial proline II→I isomerization, an oligoproline chain containing large substituents needs to have a segment of consecutive unsubstituted proline residues that is sufficiently long to form a stable proline helix. Biexponential kinetics (A→B, k1 = ∼3.3 × 10-4 s-1; B→C, k2 = ∼0.8 × 10-4 s-1) were observed for the proline II→I isomerization of ZRA2 and P9 in acetonitrile and for the proline I→II isomerization of ZRA2 in water, which provides evidence for the growth and decay of a major kinetic intermediate.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-3904
    Keywords: biexponential kinetics ; proline helices ; substituted proline residues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The kinetics of isomerization of the helical forms of three oligoprolines was determined by far-ultraviolet CD spectropolarimetry and kinetic analysis by singular value decomposition. ZRA (Pro3-X-Pro2-Y-Pro2-Z-Pro3) and ZRA2 (Pro7-X-Pro2-Y-Pro2-Z-Pro7) bear large redox-active substituents on proline residues X, Y, and Z, but P9 (Pro9) does not. All three peptides formed a stable proline-II helix in water. In acetonitrile, both ZRA2 and P9 were converted into a proline-I helical form but ZRA remained predominantly in the proline-II helical form. Evidently, in order to undergo substantial proline II→I isomerization, an oligoproline chain containing large substituents needs to have a segment of consecutive unsubstituted proline residues that is sufficiently long to form a stable proline helix. Biexponential kinetics (A→B, k1=∼3.3×10−4s−1; B→C, k2=∼0.8×10−4s−1) were observed for the proline II→I isomerization of ZRA2 and P9 in acetonitrile and for the proline I→II isomerization of ZRA2 in water, which provides evidence for the growth and decay of a major kinetic intermediate.
    Type of Medium: Electronic Resource
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