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  • 1
    ISSN: 1432-0878
    Keywords: Oocyte ; Yolk granules ; Ribonuclease ; Immunocytochemistry ; Bullfrog, Rana catesbeiana (Anura)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract To determine the localization of the pyrimidine-guanine sequence-specific ribonuclease in Rana catesbeiana (bullfrog) oocytes, the RNase was first isolated and used to prepare a specific rabbit antiserum. Only one protein of similar molecular size to the RNase was immunoprecipitated from ovary homogenate by the antiserum, but two bands were observed by Western blotting analysis. These two proteins were shown by further purification of antibody and Western blotting analysis to have similar antigenicity. Immunoprecipitation and Western blotting of tissue homogenates showed that the RNase was found predominantly in the ovary, but not in other tissues. The specific localization of the RNase was determined by immuno-electron microscopy of oocyte sections incubated with the specific antiserum; the yolk granules, but not other organelles, were found to contain the RNase. Most of the RNase was evenly distributed in the lateral amorphous area of the yolk granule but not in the central yolk crystal area which contains stored vitellogenin proteins. Our results indicate that the RNase is compartmentalized in the yolk granules of oocytes, which might prevent damage to cellular RNAs.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Keywords: Key words: Oocyte ; Yolk granules ; Ribonuclease ; Immunocytochemistry ; Bullfrog ; Rana catesbeiana (Anura)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. To determine the localization of the pyrimidine-guanine sequence-specific ribonuclease in Rana catesbeiana (bullfrog) oocytes, the RNase was first isolated and used to prepare a specific rabbit antiserum. Only one protein of similar molecular size to the RNase was immunoprecipitated from ovary homogenate by the antiserum, but two bands were observed by Western blotting analysis. These two proteins were shown by further purification of antibody and Western blotting analysis to have similar antigenicity. Immunoprecipitation and Western blotting of tissue homogenates showed that the RNase was found predominantly in the ovary, but not in other tissues. The specific localization of the RNase was determined by immuno-electron microscopy of oocyte sections incubated with the specific antiserum; the yolk granules, but not other organelles, were found to contain the RNase. Most of the RNase was evenly distributed in the lateral amorphous area of the yolk granule but not in the central yolk crystal area which contains stored vitellogenin proteins. Our results indicate that the RNase is compartmentalized in the yolk granules of oocytes, which might prevent damage to cellular RNAs.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0887-6266
    Keywords: liquid crystalline polymer ; nematic ; isotropic/nematic transition ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An aromatic copolyester composed of 25 mol % phenyl hydroquinone, 10 mol % isophthalic acid, 40 mol % chloroterephthalic acid, and 25 mol % t-butyl hydroquinone (PICT) has been synthesized. This amorphous, glassy polymer is soluble in common organic solvents such as methylene chloride. Thin, solution-cast films may be prepared which are in a metastable, vitrified, optically isotropic state. On first heating of an isotropic film at 20°C/min in a calorimeter, one glass transition is observed at low temperature (approximately 49°C) and is ascribed to the glass/rubber transition of the metastable, isotropic polymer. This thermal event is followed by a small exotherm due to the development of order during the scan, which results in a second Tg at approximately 125°C. This Tg is associated with the glass/rubber transition of the ordered polymer. Nematic order can be developed by thermal annealing. The lower Tg increases toward the upper Tg as annealing time is increased. For an initially isotropic film annealed at 90°C, the increase of the lower Tg with annealing time and the increase in birefringence observed by optical microscopy are governed by similar kinetics. Isotropization occurs in the temperature range of 250-300°C. The nematic polymer is slightly more dense than its isotropic analog. No detectable differences between isotropic and nematic samples were observed in rotating frame proton spin lattice relaxation times. © 1996 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2209-2222 
    ISSN: 0887-6266
    Keywords: poly(1-trimethylsilyl-1-propyne) ; poly(1-phenyl-1-propyne) ; blends ; gas and vapor transport ; NMR ; Maxwell model ; Bruggeman model ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Pure gas and hydrocarbon vapor transport properties of blends of two glassy, polyacetylene-based polymers, poly(1-trimethylsilyl-1-propyne) [PTMSP] and poly(1-phenyl-1-propyne) [PPP], have been determined. Solid-state CP/MAS NMR proton rotating frame relaxation times were determined in the pure polymers and the blends. NMR studies show that PTMSP and PPP form strongly phase-separated blends. The permeabilities of the pure polymers and each blend were determined with hydrogen, nitrogen, oxygen, carbon dioxide, and n-butane. PTMSP exhibits unusual gas and vapor transport properties which result from its extremely high free volume. PTMSP is more permeable to large organic vapors, such as n-butane, than to small, permanent gases, such as hydrogen. PPP exhibits gas permeation characteristics of conventional low free volume glassy polymers; PPP is more permeable to hydrogen than to n-butane. In PTMSP/PPP blends, both n-butane permeability and n-butane/hydrogen selectivity increase as the PTMSP content of the blends increases. © 1996 John Wiley & Sons, Inc.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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