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  • Wiley-Blackwell  (17)
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  • 1
    ISSN: 1040-452X
    Keywords: tPA ; Cortical granule reaction ; Sperm penetration ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The resumption of meiosis results in synthesis of tissue-type plasminogen activator (tPA) in the rat and mouse oocytes (Haurte et al., Cell 43:551-558, 1985). The present study demonstrates that freshly ovulated rat oocytes released their tPA into the surrounding medium upon in vitro activation by sperm penetration or treatment with a calcium ionophore. The presence of a neutralizing monoclonal anti-tPA antibody during in vitro activation by the calcium ionophore inhibited the activation-induced zona hardening and also preserved the ability of the oocyte to be penetrated by sperm subsequent to activation. Rat oocytes undergo zona hardening during in vitro maturation in the absence of serum, presumably as a result of spontaneous cortical granule release, based on findings in mice and hamsters. In the present study, the anti-tPA antibody prevented the zona hardening and enhanced partition by spermatozoa of rat oocytes that were matured in vitro without serum. Collectively, the observations reported here suggest a possible role of tPA released during the cortical granule reaction in the zona reaction, which contributes to the block to polyspermy.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1042-7147
    Keywords: Polymer blends ; Crystallization ; Relaxation behavior ; 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
    Notes: In this paper we focus on miscible blends of two engineering polymers: poly(butylene terephthalate) (PBT) and a polyarylate (PAr). The issue of transesterification in these blends will be addressed, followed by a discussion of the crystallization kinetics of PBT, poly(ethylene terephthalate) and several PBT/PAr blends. The ability to estimate polymer-polymer interaction parameters in blends from melting point depression will also be discussed. The amorphous phase behavior of the PBT/PAr blends has been explored primarily using dielectric spectroscopy. For blends in which PBT has crystallized, we observe two relaxations associated with Tg-like motion, and this behavior is interpreted in light of our recent work on order-disorder interphases in crystalline blends.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: polymer solution ; light scattering ; poly(isobornyl methacrylate) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermodynamic and hydrodynamic properties of dilute solutions of poly (isobornyl methacrylate) (PIMA) in tetrahydrofuran (THF) were characterized by using viscosity, static, and dynamic light scattering measurements. PIMA samples with different molecular weight were obtained by fractional precipitation of PIMA solution. Chain dimension parameters (Rg and RH), together with second virial coefficient A2 and intrinsic viscosity [η], were used to calculate various solution parameters characterizing polymer chains in polymer solutions. The experimental results are compared with calculation, indicating that PIMA behaves as a flexible coil in THF. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    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: A series of hydroxyl-terminated maleopimaric acid esters (HTMAEs) and rigid polyurethane (PU) foams based on these HTMAEs were synthesized using chemically modified natural gum rosin and its derivative maleopimaric acid as raw materials. Thermal stability of these polyols and their corresponding rigid PU foams was studied by a thermogravimetric method and a dimensional stability measurement. It was shown that the thermal stability of the final foams was strongly dependent on the structure of their corresponding polyols. The thermogravimetric analysis curves of these rosin-based rigid PU foams displayed two distinct regions of weight loss. It has been shown that at the initial stage of weight loss the process was dominated by polyol component degradation; the second stage was governed by isocyanate component degradation. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    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: A series of rosin-based rigid polyurethane foams of different composition were synthesized directly from chemically modified gum rosin. The effect of the composition of these rosin-based rigid polyurethane foams on their thermal stability and compression strength was measured. It was shown that the onset temperature of weight loss and the dimensional stability at high temperature increased with increase of the molar ratio of NCO/OH. The TGA data further confirmed that the second stage weight loss in the two-stage weight loss process of these polyurethane foams was governed by thermal degradation of the isocyanate component. Although density had no significant influence on the TGA curves of the rosin-based rigid polyurethane foams, it had great influence on the dimensional stability at high temperature and compression strength of the foams. It has been shown that the inclusion of rosin in rigid polyurethane foams increases the strength and thermal stability compared with that of polyether-based ones. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: physical aging ; tracer diffusion coefficient ; camphorquinone ; polysulfone ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of physical aging on the tracer diffusion coefficient D of camphorquinone in polysulfone is investigated. It is shown that if the sample is sufficiently annealed and physical aging is nearly complete, the temperature dependence of D will reflect the primary α-relaxation process of the host polymer. In the temperature range between Tg (=185°C) and 165°C, D is found to be a function of time, and the time dependence of D is given by D = At-μ, with μ approximately equal to unity. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1040-452X
    Keywords: Zonae pellucidae ; Trypsin inhibitor ; β-Mercaptoethanol ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The present study confirms that zonae pellucidae of rat oocytes became resistant to chymotrypsin digestion (zona hardening) after undergoing in vitro maturation (IVM) in a serum-free medium. However, zona hardening and did not occur when empty zonae without oocytes were cultured in the same IVM conditions, suggesting that oocyte-derived factor(s) is responsible for zona hardening in oocytes matured in the serum-free medium. Zona hardening occurred primarily after dictyate oocytes were cultured for 6-8 hours in the IVM medium without serum. Zona hardening could be prevented or alleviated if oocytes were cultured in the IVM medium containing bovine foetal calf serum, a soybean trypsin inhibitor, or β-mercaptoethanol, and in vitro fertilization rates for such oocytes were normal. Possible mechanisms of the phenomenon of zona hardening in oocytes matured in serum-free conditions are discussed in relation to its possible relevance to the cortical reaction and the physiological block to polyspermy.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1076-5174
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An N-terminal proteolytic processing product of chromogranin A was obtained from bovine chromaffin granules using two steps of C18 solid-phase extraction and reversed-phase high-performance liquid chromatography. Electrospray mass spectrometry revealed a protein with a molecular mass of 8632.0 for the fraction showing immunoreactivity against the N-terminus of chromogranin A, which differed by 48 u from that of the N-terminal processing product, vasostatin I (CGA1-76). Derivatization with mercaptoethanol showed that the peptide had an intact S—S bridge, which is a key structural feature of vasostatin I. Peptide mapping experiments involving reduction/alkylation with vinylpyridine and trypsin digestion were consistent with oxidation of the three methionine residues of vasostatin I to their sulphoxide forms. The oxidation of the methionine residues was found to occur during the C18 solid-phase extraction procedure. The use of freshly prepared Tris-HCl buffer and eluents and flushing the buffer and eluents with nitrogen were shown to result in the isolation of the non-oxidized form of vasostatin I.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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