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  • Chemistry  (23)
  • Polymer and Materials Science  (8)
  • Islet of Langerhans  (3)
  • 1
    Electronic Resource
    Electronic Resource
    The role of protein kinase C in insulin biosynthesis (1993)
    Springer
    Acta diabetologica 30 (1993), S. 99-104 
    Details
    ISSN: 1432-5233
    Keywords: Insulin synthesis ; Islet of Langerhans ; Northern blotting ; Phorbol ester ; Protein kinase C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Activation of protein kinase C (PKC) by the phorbol ester 4β-phorbol myristate acetate (4β-PMA) stimulated (pro)insulin biosynthesis in collagenase-isolated rat islets of Langerhans, as assessed by measuring the incorporation of [35S]cysteine into proinsulin and insulin after fractionation by high performance liquid chromatography. The stimulatory effects of 4β-PMA were observed at a substimulatory concentration of glucose (2 mM) but were not additive to the stimulatory effects of 20 mM glucose on insulin biosynthesis. Prolonged exposure to 4β-PMA caused a marked down-regulation of PKC activity in islets. PKC-depleted islets showed a much reduced biosynthetic response to 20 mM glucose, but this was caused, at least in part, by an enhanced basal rate of (pro)insulin synthesis. These elevations in the basal rate of insulin synthesis were not secondary to an inerease in the amount of preproinsulin mRNA in PKC-depleted islets since Northern blot analysis showed that prolonged exposure to 4β-PMA, and the subsequent loss of PKC activity, did not detectably alter basal levels of preproinsulin mRNA. These results suggest that the activation of PKC stimulates (pro)insulin synthesis in rat islets by enhancing translation of existing preproinsulin mRNA, and that this may play some part in the biosynthetic responses of β-cells to glucose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00578222
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  • 2
    Electronic Resource
    Electronic Resource
    Protein phosphorylation in the regulation of insulin secretion: the use of site-directed inhibitory peptides in electrically permeabilised islets of Langerhans (1995)
    Springer
    Acta diabetologica 32 (1995), S. 32-37 
    Details
    ISSN: 1432-5233
    Keywords: Islet of Langerhans ; Insulin secretion ; Protein phosphorylation ; Protein kinase C ; Protein kinase A ; Inhibitory peptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have used electrically permeabilised rat islets of Langerhans to investigate the role of protein phosphorylation in the regulation of insulin secretion using pseudosubstrate inhibitory peptides for cyclic AMP-dependent protein kinase (PKA) and for protein kinase C (PKC). The protein kinase inhibitor (PKI) peptide, PKI(6–22), completely inhibited the effects of cyclic AMP on islet PKA activity in vitro, on endogenous protein phosphorylation and on insulin secretion. This peptide had no significant effect on islet PKC activity in vitro, on CA2+-induced protein phosphorylation and on secretory responses to Ca2+ or to the PKC activator, 4β-phorbol myristate acetate (PMA). The PKC pseudosubstrate inhibitory peptide, PKC(19–36), caused a marked inhibition of islet PKC activity in vitro and inhibite PMA-induced insulin secretion without affecting secretory responses to cyclic AMP and Ca2+. These results demonstrate that PKA-and PKC-induced protein phosphorylation is obligatory for cyclic AMP-and PMA-stimulated insulin secretion, respectively, and suggest that there is little “crosstalk” between the response elements of the secretory pathways to the different, second messengers, at least after the generation of the messengers within the β-cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581042
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  • 3
    Electronic Resource
    Electronic Resource
    Nitric oxide is not involved in the initiation of insulin secretion from rat islets of Langerhans (1992)
    Springer
    Diabetologia 35 (1992), S. 1020-1027 
    Details
    ISSN: 1432-0428
    Keywords: Islet of Langerhans ; insulin secretion ; nitric oxide ; cyclic guanosine monophosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The involvement of nitric oxide as an intracellular messenger in the control of insulin secretion from pancreatic Beta cells was studied in rat islets of Langerhans by measuring: (i) nitric oxide generation in response to physiological insulin secretagogues; (ii) the effects of inhibitors of nitric oxide synthesis on insulin secretory responses to physiological secretagogues, and on insulin synthesis; (iii) changes in islet cyclic guanosine monophosphate in response to secretagogues; (iv) the effects of exogenous cyclic guanosine monophosphate and dibutyryl cyclic guanosine monophosphate on insulin secretion from electrically permeabilised islets and from intact islets, respectively. These studies produced no evidence that nitric oxide generation is required for the initiation of insulin secretion by common secretagogues. However, the results of our experiments suggest that the generation of nitric oxide may be involved in long-term, glucose-dependent increases in cyclic guanosine monophosphate content of islet cells, although the physiological relevance of these changes requires further investigation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02221676
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  • 4
    Electronic Resource
    Electronic Resource
    A positron annihilation lifetime study of isothermal structural relaxation in bisphenol-A polycarbonate (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 1541-1552 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Positron annihilation lifetime spectroscopy has been used to study the isothermal relaxation response of compression molded bisphenol-A polycarbonate at temperatures of 263, 273, and 303 K. The temperature dependence of both the lifetime and intensity of the ortho-Positronium (o-Ps) pickoff component is discussed in terms of ductile-to-brittle transition behavior and free volume theory. An additive exponential model and the Williams-Watt model were used to analyze the relaxation as a function of temperature and provided results consistent with the anticipated molecular mobility of polycarbonate at sub-Tg temperatures.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1988.080260605
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  • 5
    Electronic Resource
    Electronic Resource
    1,5-dimethyl-2,3,3,4-tetrachloro-1,5,2,4-diazadiphosphorinan-6-one and some derivatives. Part II (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 8 (1997), S. 165-175 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compound 1 was allowed to react with catechol, 2,3-dihydroxynaphthalene, tetrabromocatechol, resorcinol, saligenin, and 3,5-di-tert-butylcatechol in the presence of triethylamine to form compounds 4a-4d and 4f. Whereas the catechol derivative 4a, the naphthol derivative 4b, and the tetrabromocatechol derivative 4c could be readily obtained, the saligenin derivative 4d and the 3,5-di-tert-butylcatechol derivative 4f were found to be stable only in solution. Contrary to expectation, compound 4e was not formed in the reaction of 1 with resorcinol. The reaction of 1 with 1,2,4,5-tetrahydroxybenzene led to the pentacyclic derivative 4g. Reaction of hydroquinone with 1 led to the formation of the dimeric structure 4h. Crystal structure analyses of 4a and 4b show that the nine-membered rings adopt essentially identical “tub” conformations in which the P and O atoms are coplanar. The P-C-P angles (across the CCl2 bridge) are wide (ca. 119°). © 1997 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal degradation of polymers. II further thermogravimetric and differential thermal analysis studies of atactic poly(m-aminostyrene) homopolymers, copolymers, and related polymers (1969)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 401-415 
    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: Thermogravimetric and differential thermal analysis have been employed to study the effect on the thermal degradation pattern in static air of the molecular weight of poly(m-aminostyrene) homopolymers and copolymers with styrene. Related substituted styrene polymers and copolymers with styrene have also been studied in order to assess the effect of introduction of amino, substituted amino, and hydroxy groupings into a polystyrene main chain. The effect of these groupings on the thermal stability of the polymers as compared with polystyrene suggests that the inherent antioxidant characteristics of the subtituent grouping plays the major role in stabilization. A molecular weight effect has been shown to be operative for m-aminostyrene, p-N,N-dimethylaminostyrene, and m-hydroxystyrene polymers. This manifests itself in terms of different thermograms rather than by significantly influencing the procedural decomposition temperatures, although a trend is seen.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1969.070130301
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal degradation of polymers. part IV. Vacuum pyrolysis of poly(m-aminostyrene). The residue and the fraction volatile at pyrolysis temperature involatile at room temperature (1969)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 1555-1567 
    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: The effect of the extent of degradation of poly(m-aminostyrene) on the quantity and composition of the residue and the effect of pyrolysis temperature on the fraction volatile at pyrolysis temperature are discussed. The behavior of poly(m-aminostyrene) is compared to that of polystyrene; a significant difference has been found for the behavior of the residue from poly(m-aminostyrene), which is ascribed to a crosslinking reaction involving the amino substituent. Mechanisms to acount for the observed products of degradation have been suggested and are discussed. Relative thermal stability studies have also been made and compared with results from polystyrene.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1969.070130718
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  • 8
    Electronic Resource
    Electronic Resource
    Thermal degradation of polymers. Part III. Vacuum pyrolysis of poly(m-aminostyrene); the products volatile at pyrolysis temperature which are liquid or gaseous at room temperaturePaper presented at Thermal Analysis Group of Society of Analytical Chemistry Burlington House, London, on November 13th, 1968. (1969)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 2033-2043 
    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: The products obtained on degradation of poly(m-aminostyrene) in vacuo are described. The effect of molecular weight and pyrolysis temperature are discussed and the behavior of poly(m-aminostyrene) compared with that of polystyrene. Quantitative analytical methods using ultra-violet spectroscopy and gas liquid chromatography are described for m-aminostyrene and m-toluidine. The possible mechanisms of degradation to yield the products are discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1969.070131001
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  • 9
    Electronic Resource
    Electronic Resource
    Decomposition of organic wastes by Sphaerotilus (1963)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 5 (1963), S. 287-307 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Sphaerotilus is usually present in biological waste treatment processes and is considered to be a nuisance organism because it may cause bulking of activated sludge. However, it may play an important role in the decomposition of putrescible organic matter in properly operated biological waste treatment processes. The research described herein is a study of the variety of types of organic compounds which may be decomposed by Sphaerotilus and the effect of some environmental factors upon the rate of decomposition. Although there are some types of compounds which cannot be decomposed by Sphaerotilus, it is shown that this organism is able to assimilate and oxidize a large variety of organic compounds and that it is tolerant of an extremely wide range of environmental conditions. The role of Sphaerotilus in biological waste treatment is discussed in the light of the data presented.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260050405
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  • 10
    Electronic Resource
    Electronic Resource
    Ringtransformationen heterocyclischer Verbindungen. I. 2-Amino-benzophenone und 7-Oxo-hepta-2,4-diennitrile durch Reaktion von 2,4,6-Triaryl-pyryliumsalzen mit 4-Nitro-benzylcyanid (1993)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 335 (1993), S. 351-358 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ring Transformations of Heterocyclic Compounds. I. 2-Amino-benzophenones and 7-Oxo-hepta-2,4-dienenitriles by Reaction of 2,4,6-Triarylpyrylium Salts with 4-Nitrobenzyl Cyanide2,4,6-Triarylpyrylium salts 1 react with 4-nitrobenzyl cyanide in the presence of sodium acetate, triethylamine or triethylamine/acetic acid to give 7-oxo-hepta-2,4-dienenitriles 2. With stronger bases such as sodium methanolate or ethanolate a ring transformation of the salts 1 occurs giving rise to 2-amino-benzophenones 3 which can also be obtained by cyclization of the nitriles 2. Under the same conditions the 3-methyl-2,4,6-triphenylpyrylium salt 4 forms the 4-methyl-7-oxo-hepta-2,4-dienenitrile 5 by regioselective addition of the 4-nitrobenzyl cyanide at C-2 or it is converted to the 2-amino-5-methyl-benzophenone 6. The ring transformation of the pyrylium salts 1/4 by 4-nitrobenzyl cyanide represents a new and simple method for the preparation of 2-amino-benzophenones. - Spectroscopic data of the novel compounds are discussed; the structure of 5 was confirmed by a single crystal X-ray analysis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19933350408
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