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  • 1
    Electronic Resource
    Electronic Resource
    Hyperresponse in calcium-induced insulin release from electrically permeabilized pancreatic islets of diabetic GK rats and its defective augmentation by glucose (1995)
    Springer
    Diabetologia 38 (1995), S. 772-778 
    Details
    ISSN: 1432-0428
    Keywords: Key words Insulin release ; intracellular calcium ; exocytosis ; GK rat ; permeabilized islets.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In spontaneously diabetic GK rats, insulin secretion from pancreatic beta cells in response to glucose is selectively impaired, probably due to deficient intracellular metabolism of glucose and impaired closure of KATP channels during glucose stimulation. By using electrically permeabilized islets of GK rats, we explored the functional modulations in exocytotic steps distal to the rise in [Ca2 + ]i in the diabetic condition. At 30 nmol/l Ca2 + (basal conditions) insulin release was similar between GK and non-diabetic control Wistar rats. In response to 3.0 μmol/l Ca2 + (maximum stimulatory conditions), insulin release was significantly augmented in permeabilized GK islets (p 〈 0.01). Raising glucose concentrations from 2.8 to 16.7 mmol/l further augmented insulin release induced by 3.0 μmol/l Ca2 + from permeabilized control islets(p 〈 0.001), but had no effect on that from permeabilized GK islets. The stimulatory effect of glucose on insulin release from permeabilized control islets was partly inhibited by 2,4-dinitrophenol, an inhibitor of mitochondrial oxidative phosphorylation (p 〈 0.01). The hyperresponse to Ca2 + in GK islets may play a physiologically compensatory role on the putative functional impairment both in [Ca2 + ]i rise and energy state in response to glucose in diabetic β cells, and may explain the relative preservation of insulin release induced by non-glucose depolarizing stimuli, such as arginine, from pancreatic islets in non-insulin-dependent diabetes mellitus. [Diabetologia (1995) 38: 772–778]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001250050351
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  • 2
    Electronic Resource
    Electronic Resource
    Reduced sensitivity of dihydroxyacetone on ATP-sensitive K+ channels of pancreatic beta cells in GK rats (1994)
    Springer
    Diabetologia 37 (1994), S. 1082-1087 
    Details
    ISSN: 1432-0428
    Keywords: Dihydroxyacetone ; ATP-sensitive K+ channels ; GK rat ; glycerol phosphate shuttle ; pancreatic beta cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the GK (Goto-Kakizaki) rat, a genetic model of non-insulin-dependent diabetes mellitus, glucose-induced insulin secretion is selectively impaired. In addition, it has been suggested by previous studies that impaired glucose metabolism in beta cells of the GK rat results in insufficient closure of ATP-sensitive K+ channels (KATP channels) and a consequent decrease in depolarization, leading to a decreased insulin release. We have recently reported that the site of disturbed glucose metabolism is probably located in the early stages of glycolysis or in the glycerol phosphate shuttle. In the present study, in order to identify the impaired metabolic step in diabetic beta cells, we have investigated insulin secretory capacity by stimulation with dihydroxyacetone (DHA), which is known to be directly converted to DHA-phosphate and to preferentially enter the glycerol phosphate shuttle. In addition, using the patch-clamp technique, we also have studied the sensitivity of DHA on the KATP channels of beta cells in GK rats. The insulin secretion in response to 5 mmol/l DHA with 2.8 mmol/l glucose was impaired, and DHA sensitivity of the KATP channels was reduced in beta cells of GK rats. From these results, we suggest that the intracellular site responsible for impaired glucose metabolism in pancreatic beta cells of GK rats is located in the glycerol phosphate shuttle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418371
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  • 3
    Electronic Resource
    Electronic Resource
    Reduced sensitivity of dihydroxyacetone on ATP-sensitive K+ channels of pancreatic beta cells in GK rats (1994)
    Springer
    Diabetologia 37 (1994), S. 1082-1087 
    Details
    ISSN: 1432-0428
    Keywords: Key words Dihydroxyacetone ; ATP-sensitive K+ channels ; GK rat ; glycerol phosphate shuttle ; pancreatic beta cell.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the GK (Goto-Kakizaki) rat, a genetic model of non-insulin-dependent diabetes mellitus, glucose-induced insulin secretion is selectively impaired. In addition, it has been suggested by previous studies that impaired glucose metabolism in beta cells of the GK rat results in insufficient closure of ATP-sensitive K+ channels (KATP channels) and a consequent decrease in depolarization, leading to a decreased insulin release. We have recently reported that the site of disturbed glucose metabolism is probably located in the early stages of glycolysis or in the glycerol phosphate shuttle. In the present study, in order to identify the impaired metabolic step in diabetic beta cells, we have investigated insulin secretory capacity by stimulation with dihydroxyacetone (DHA), which is known to be directly converted to DHA-phosphate and to preferentially enter the glycerol phosphate shuttle. In addition, using the patch-clamp technique, we also have studied the sensitivity of DHA on the KATP channels of beta cells in GK rats. The insulin secretion in response to 5 mmol/l DHA with 2.8 mmol/l glucose was impaired, and DHA sensitivity of the KATP channels was reduced in beta cells of GK rats. From these results, we suggest that the intracellular site responsible for impaired glucose metabolism in pancreatic beta cells of GK rats is located in the glycerol phosphate shuttle. [Diabetologia (1994) 37: 1082–1087]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418371
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  • 4
    Electronic Resource
    Electronic Resource
    Polymerization of diethynyldiphenylmethane: DSC, FTIR, NMR, and dielectric characterization (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 27 (1989), S. 1611-1627 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 4,4′-Diethynyldiphenylmethane thermally polymerizes by a free radical mechanism to a highly crosslinked structure of interest as a high temperature composite matrix resin. The polymerization reaction was characterized by differential scanning calorimetry, Fourier-transform infrared (FTIR) spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, and microdi-electrometry. The predominant reaction mechanism appears to be linear polymerization through the acetylene end groups, which follows first-order kinetics. However, during the early stages of reaction a second, more rapid polymerization mechanism is evident; it is postulated that this is the formation of a cyclic trimer, which is kinetically favored but sterically prohibited as the crosslinked network grows. Formation of a liquid crystalline trimer is hyppthesized; such intermediate formation is supported by intensity increases in the aromatic region of the NMR spectra, by FTIR difference spectroscopy comparisons with model compounds, and by enhancement of conductivity as observed by microdielectrometry.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1989.090270803
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular level study of the crystallization of a thermoplastic polyimide by infrared spectroscopy (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2271-2282 
    Details
    ISSN: 0887-6266
    Keywords: Polyimide, thermoplastic, semicrystalline ; Fourier transform infrared spectroscopy (FTIR) ; crystallization process ; intramolecular rotation ; intermolecular chain packing ; local molecular order ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystallization process of the thermoplastic polyimide derived from 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 2,2-dimethyl-1,3,-(4-aminophenoxy) propane (DMDA) is studied at the molecular level by utilizing infrared spectroscopy's sensitivity to local molecular environment. Assignments of the unique spectral features appearing upon crystallization are made with additional verification from crystalline model imide compounds. A direct comparison of an annealed polyimide film studied by both infrared spectroscopy and x-ray diffraction shows fairly close agreement in the amount of crystallinity obtained. The unique crystalline infrared spectral features provide insight into the molecular mechanism involved with the crystallization process. Spectral shifts occurring upon crystallization reflect intramolecular rotations toward increased coplanarity as well as intermolecular chain packing of certain molecular groups at specific sites of the chain backbone. The site specific information is then used to study the relative kinetic behavior of the intramolecular and intermolecular effects occurring during crystallization. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090321314
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  • 6
    Electronic Resource
    Electronic Resource
    Surface modification of contact-lens materials by silanization: An FTIR-ATR study (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 213-232 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The adsorption, desorption, and orientation characteristics of two long-chain chlorosilane compounds, octadecyltrichlorosilane and 1-undecylene-dimethylchlorosilane, onto poly(methyl methacrylate) (PMMA) and poly(2-hydroxyl-ethyl methacrylate) (PHEMA) are studied using Fourier-transform infrared attenuated total reflection (FTIR-ATR) spectroscopy. Quantitative monitoring of the amount of silane adsorbed is also attempted. It is believed that the surface modification reaction has been successfully confined to monolayer coverages and that sufficient detection sensitivity has been achieved to observe the reaction at these low levels on both PMMA and PHEMA. Also, ATR polarization studies indicate that on both substrates, a definite preference for orientation exists such that the long molecular axis is perpendicular to the substrate surface. The silanes are observed to be only physisorbed onto the PMMA surface under the anhydrous conditions applied during adsorption, whereas a chemical reaction is observed on the PHEMA surface.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090280208
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  • 7
    Electronic Resource
    Electronic Resource
    FTIR separation of nylon-6 chain conformations: Clarification of the mesomorphous and γ-crystalline phases (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 489-495 
    Details
    ISSN: 0887-6266
    Keywords: infrared spectra of Nylon-6 chain conformation ; Nylon-6 chain conformation, FT-IR separation of ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Specific infrared absorptions for each form of Nylon-6 have been indentified. Quenched films were prepared by melt casting and converted in turn to the α-crystalline and γ-crystalline structures. The films were examined using Fourier transform infrared spectroscopy (FTIR) with the attenuated total reflection configuration and by X-ray diffractometry. The FTIR spectrum of the pure mesomorphous component of the quenched film was calculated by subtracting away the contribution of α-crystalline peaks present due to incomplete quenching. A curve-fitting procedure was applied to the pure mesomorphous and gamma crystalline spectra. Several peaks in the mesomorphous spectrum are observed to develop a shoulder upon conversion to the γ-crystalline form. This is due to the extra gauche character imparted to the C—N bond between the methylene unit and the amide group. These and other band assignments were confirmed by analysis of model compounds.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1992.090300508
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of the surface treatment of graphitized carbon fibers on the curing of an amine-catalyzed epoxy-anhydride system (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 1121-1135 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The surface of graphitized carbon fibers is oxidatively treated by nitric acid. Fourier transform infrared attenuated total reflection spectroscopy has been utilized to monitor the influence of the surface species on the curing of an epoxy system. A curve-fitting program is used to deconvolve the overlapped infrared bands. The integrated intensities of the ester, anhydride, epoxy, and carboxylic acid, plotted against the curing time, clearly show the dependence of the crosslinking process on the concentration of the surface species. The surface groups themselves act as a catalyst: there exists an optimal concentration below which an activation of the curing process occurs. Above that concentration, a retardation of the curing process has been detected.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090280710
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  • 9
    Electronic Resource
    Electronic Resource
    Investigation of ethylene-vinyl alcohol copolymers for surface modification of contact lenses (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 67-73 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ethylene-vinyl alcohol copolymers from 0 to 57 mol % of vinyl alcohol were investigated for potential contact lens surface modification. Films of the ethylene-vinyl alcohol copolymers made by solution casting, showed that the copolymers with a high percentage of vinyl alcohol groups possessed excellent surface properties such as good wettability, low protein (albumin) and lipid adsorption, and no conformational change of the adsorbed protein. Utilizing the Langmuir-Blodgett dipping technique, an ultrathin layer of ethylene-vinyl alcohol copolymer was deposited on a silicone rubber substrate. This initial results confirm that wettability was improved and the amount of protein adsorbed was reduced significantly after only one deposition trip.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1991.090290109
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of fumed silica upon the reaction of iron octoate and polysiloxanes (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 44 (1992), S. 1331-1341 
    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: Silica is a common component in silicone elastomer formulation. Silica is known to have surface hydroxyl groups and the reactions and interactions of these surface groups with various materials have been studied extensively in the past. It is believed that the iron octoate used to combat oxidative embrittlement in silicone elastomer formulations may also react with the surface of silica, specifically fumed silica. Dynamic mechanical spectroscopy (DMS), Fourier Transform Infrared Spectroscopy (FT-IR), Electron Scanning for Chemical Analysis (ESCA), and Gel Permeation Chromatogrphy (GPC) were used to study the influence of untreated fumed silica and silica treated with dimethylsiloxane species on the iron octoate reaction. The rate of reaction was studied as a function of loading of silica. From analyzing rates of backbone scission and salt consumption, it is found that the iron octoate reacts preferentially with the surface of untreated fumed silica. Conversely, iron octoate appears to have no preferential reaction with the surface of the treated fumed silica.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070440803
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