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  • 1995-1999  (5)
  • Chemistry  (3)
  • Insulin  (2)
  • Torpedo marmorata
  • 1
    ISSN: 1432-0428
    Keywords: Insulin ; insulin analogues ; glucose metabolism ; euglycaemic clamp ; insulin action ; hepatoselectivity ; glucose production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Insulin analogues with relatively greater effect on hepatic glucose production than peripheral glucose disposal could offer a more physiological approach to the treatment of diabetes mellitus. The fact that proinsulin exhibits this property to a minor degree may suggest that analogues with increased molecular size may be less able than insulin to obtain access to peripheral receptor sites. Covalent insulin dimers have previously been shown to possess lower hypoglycaemic potencies than predicted by their in vivo receptor binding affinities. Reduced rates of diffusion to peripheral target tissues-might be an explanation for the lower in vivo potency compared to insulin. To test the relative hepatic and peripheral effects of covalent insulin dimers, glucose clamp procedures with D-[3-3H] glucose tracer infusions were used in anaesthetised greyhounds to establish dose-response curves for rates of hepatic glucose production and glucose disposal with insulin, NαB1, NαB′ 1,-suberoyl-insulin dimer, and NεB29, NεB′ 29,-suberoyl-insulin dimer. With NαB1, NαB′ 1,-suberoyl-insulin dimer molar potencies relative to insulin were 68%, (34–133) (mean and 95% fiducial limits), for inhibition of hepatic glucose production and 14.7%, (10.3–20.9) for glucose disposal. With NεB29,NεB′ 29,-suberoyl-insulin dimer potencies were 75%, (31–184) and 2.5%, (1.5–4.3), for inhibition of hepatic glucose production and for glucose disposal, respectively. The demonstration that both dimers exhibit a significantly greater effect on glucose production than on glucose disposal supports the suggestion that analogues with increased molecular size may exhibit reduced ability to gain access to peripheral target cells.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-136X
    Keywords: Glycogen ; Hepatocyte ; Insulin ; 13C NMR ; Rainbow trout, Oncorhynchus mykiss
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This study, using 13C nuclear magnetic resonance spectroscopy showed enrichment of glycogen carbon (C1) from 13C-labelled (C1) glucose indicating a direct pathway for glycogen synthesis from glucose in rainbow trout (Oncorhynchus mykiss) hepatocytes. There was a direct relationship between hepatocyte glycogen content and total glycogen synthase, total glycogen phosphorylase and glycogen phosphorylase a activities, whereas the relationship was inverse between glycogen content and % glycogen synthase a and glycogen synthase a/glycogen phosphorylase a ratio. Incubation of hepatocytes with glucose (3 or 10 mmol·1-1) did not modify either glycogen synthase or glycogen phosphorylase activities. Insulin (porcine, 10-8 mol·1-1) in the medium significantly decreased total glycogen phosphorylase and glycogen phosphorylase a activities, but had no significant effect on glycogen synthase activities when compared to the controls (absence of insulin). In the presence of 10 mmol·1-1 glucose, insulin increased % glycogen synthase a and decreased % glycogen phosphorylase a activities in trout hepatocytes. Also, the effect of insulin on the activities of % glycogen synthase a and glycogen synthase a/glycogen phosphorylase a ratio were more pronounced at low than at high hepatocyte glycogen content. The results indicate that in trout hepatocytes both the glycogen synthetic and breakdown pathways are active concurrently in vitro and any subtle alterations in the phosphorylase to synthase ratio may determine the hepatic glycogen content. Insulin plays an important role in the regulation of glycogen metabolism in rainbow trout hepatocytes. The effect of insulin on hepatocyte glycogen content may be under the control of several factors, including plasma glucose concentration and hepatocyte glycogen content.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1307-1311 
    ISSN: 0887-6266
    Keywords: polymer surfaces ; polymer films ; polymer blends ; phase separation ; polystyrene-polybutadiene ; neutron reflectometry ; ion beam profiling ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 4 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. 901-908 
    ISSN: 0887-6266
    Keywords: hydrogen atom ejection ; radical-pair formation ; computer modelling of in ; n-hydrocarbons and high density polyethylene (HDPE) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Hydrogen atom ejection and subsequent radical pair formation have been modeled in a simple atomistic study employing a BIOSYM amorphous polyethylene macrocell. Mean radical pair distances have been obtained for various maximum hydrogen displacement vibrational cone angles (φ) in the model. φ angles extrapolated from these data, which correspond to experimentally determined mean radical pair distances of Dubinskii et al. (ca. 5.6 Å) and Iwasaki et al. (ca. 5.75 Å), are found to be close to φ angles calculated from hydrogen atom ejection theory. The Dubinskii et al. mean is thought to be the best determination, because the associated model φ angle (ca. φ = 15°) is the closest to φ* angles calculated for excited states of methane. The simple computer model thus supports the mechanism of radical pair formation in solid n-hydrocarbons and polyethylenes. In corroborating the theory for radical pair formation, the theory for polyene crosslinking termination reactions in amorphous polyethylenes irradiated in the presence of acetylene is also supported, because the mechanism requires the prior formation of radical pairs that are separated by distances of the order of those found by Dubinskii et al. The model is transferable to the study of radical-pair reactions in solid n-hydrocarbons irrespective of branching and density variations. A distribution function of radical pair distances from this model, which corresponds to the Dubinskii et al. experimentally determined mean distance, is given for amorphous HDPE. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 39 (1996), S. 271-271 
    ISSN: 0959-8103
    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
    Type of Medium: Electronic Resource
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