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  • Chemical Engineering  (6)
  • Aging  (3)
  • GK rat  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Age-dependent changes in the phosphorylation of nuclear proteins of submandibular glands in isoproterenol-treated rats
    Amsterdam : Elsevier
    Mechanisms of Ageing and Development 70 (1993), S. 127-137 
    Details
    ISSN: 0047-6374
    Keywords: Aging ; Histone proteins ; Isoproterenol ; Non-histone proteins ; Phosphorylation ; Submandibular gland
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0047-6374(93)90064-X
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  • 2
    Electronic Resource
    Electronic Resource
    Rapid accumulation of fluorescent material with aging in an oxygen-sensitive mutant mev-1 of Caenorhabditis elegans
    Amsterdam : Elsevier
    Mechanisms of Ageing and Development 74 (1994), S. 161-170 
    Details
    ISSN: 0047-6374
    Keywords: Aging ; Caenorhabditis elegans ; Fluorescent material ; Oxygen-sensitive mutant
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0047-6374(94)90087-6
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  • 3
    Electronic Resource
    Electronic Resource
    Density-associated changes in platelet-activating factor acetylhydrolase activity and membrane fluidity of human erythrocytes (1994)
    Springer
    Annals of hematology 69 (1994), S. 139-145 
    Details
    ISSN: 1432-0584
    Keywords: Aging ; Erythrocytes ; Platelet-activating factor ; Acyltransferases ; Membrane fluidity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Platelet-activating factor acetylhydrolase is known to degrade oxidatively fragmented phospholipids which are similar in structure to platelet-activating factor. We examined changes of acetylhydrolase activity during in vivo aging of human erythrocytes and tried to assess its role in maintaining the membrane properties of erythrocytes. Higher-density erythrocytes are enriched with older cells. Erythrocytes obtained from seven healthy colleagues were separated into four density fractions by centrifugation in discontinuous Percoll density gradients. Both membrane and cytosolic acetylhydrolase decreased with increasing erythrocyte density. Membrane and cytosolic acetylhydrolase activities in the lightest fraction were 2.0±1.0 (SD) nkat/g protein and 362±58 pkat/g protein, respectivley, and these values were significantly higher than those in the densest fraction: 1.3±0.7 nkat/g protein and 286±70 pkat/g protein, respectively. Membrane acyltransferase activity also decreased with red cell density and the average values in the lightest and densest fractions were 51.2±23.6 and 27.0±20.2 μkat/g protein, respectively. Generation of thiobarbituric acid-reactive substances induced byt-butyl hydroperoxide treatment decreased with increasing cell density, and the inhibition of acetylhydrolase with diisopropylfluorophosphate resulted in enhanced peroxide-induced lipid oxidation, particularly in lower-density fractions. There was no significant change in basal levels of thiobarbituric acid-reactive substances in red cell membrane. Membrane fluidity was evaluated by fluorescence recovery after photobleaching and it decreased as erythrocyte density increased. We conclude that the activity of the deacylation/reacylation cycle maintained by acetylhydrolase and acyltransferase is gradually reduced during in vivo aging of erythrocytes. This may be connected with decreases of polyunsaturated fatty acids and membrane fluidity in old eryhtrocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01695695
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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    The reinforcement mechanism of fiber-glass reinforced plastics under wet conditions: A review (1978)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 128-145 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Reinforcement mechanisms of fiber-glass reinforced plastics (FRP) under wet conditions are reviewed with emphasis on molecular structures of glass/matrix interfaces. Included are studies on glass surface, the glass/coupling agent interface, silane coupling agents on glass surfaces as well as in solution, the coupling agent/matrix interface, extending to the interphase of particulate-filled composites, and matrix resin. For a better understanding of wet strength of FRP, the structures under dry conditions are extensively, reviewed. The chemical bonding theory still dominates other reinforcement theories. The importance of other factors such as orientation of silane coupling agents and the restriction of matrix polymer conformations are also considered. Based on recent development in spectroscopy, molecular level research of the glass/matrix interfaces has been initiated in the past decade, yet only a few spectroscopic investigations on the function of water have appeared. It is concluded that the correlation between spectroscopic investigations and mechanical properties of a FRP is indispensable.
    Additional Material: 32 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760180211
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of fuming nitric acid surface treatment of ultra-high modulus polyethylene fibers on the mechanical properties of their composites (1992)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 13 (1992), S. 81-85 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effect of hot fuming nitric acid (FNA) treatment on the adhesion of ultra-high modulus polyethylene fabrics to an epoxy resin has been investigated. Mechanical and molecular characterization of the interface has been attempted. Fourier transform infrared diffuse transmittance spectroscopy has been used to monitor the chemical changes introduced by the FNA treatment as well as the nature of the interface between the fibers and the epoxy resin on the molecular level. Scanning electron microscopy has been used to examine the morphological consequences of the FNA treatment. Flexural and interlaminar shear properties of the composites have been measured as a function of the extent of surface treatment. Esterification of the FNA treated polyethylene fibers is used to examine the role of surface functionality to the mechanical performance.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750130203
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  • 9
    Electronic Resource
    Electronic Resource
    The silane interphase of composites: Effects of process conditions on γ-aminopropyltriethoxysilane (1986)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 7 (1986), S. 231-238 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: FT-IR spectroscopy was used to collect spectra of γ-aminopropyltriethoxy silane (γ-APS) coupling agent deposited on KBr plates, modeling the silane interphase of composites, to study the effects of heating the γ-APS film under various environmental conditions. This coupling agent is used in fiber-reinforced epoxy composites. An aminebicarbonate salt forms when the sample is dried in a moist carbon dioxide environment giving rise to a series of bands from 2800 to 2000 centimeter-1 (cm-1) and bands at 1637 cm-1, 1330 cm-1, 696 cm-1, and 663 cm-1. The primary amine group is split into two bands at 1572 cm-1 and 1486 cm-1 in the NH3+ form. Heating removes the aminebicarbonate salt at temperatures above 95°C and condenses the γ-APS polymer to a polysilsesquioxane film. The aminebicarbonate salt partially reforms if the γ-APS film is stored in a moist CO2 environment. At temperatures above 120°C the primary amine of γ-APS is oxidized in air to imine groups. In the process of evolving the CO2 the polymer is further condensed and the amine groups can be converted to imines if the temperatures exceeds 120°C. Both processes reduce the reactivity of the coupling agent with the epoxy resin. The structure of the silane interphase must be controlled during the processing of the composite to yield materials with maximum properties.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750070406
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  • 10
    Electronic Resource
    Electronic Resource
    Spectroscopic studies of the gradient in the silane coupling agent/matrix interface in fiberglass-reinforced epoxy (1988)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 9 (1988), S. 151-157 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Differential scanning calorimetry, Fourier transform infrared, and solid-state carbon 13 nuclear magnetic resonance were used to study the silane coupling agent/epoxy resin interface. Penetration of epoxy into the hydrolyzed silane has been shown. The addition of a solvent can further increase the penetration of epoxy into the hydrolyzed silane by decreasing the viscosity of the epoxy. Bulk models of the gradient in the silane coupling agent/epoxy interface have shown that the concentration of silane and the degree of hydrolysis of the silane can determine the rigidity or mobility of the interphase region. When the silane is hydrolyzed, the possible formation of entanglements may increase the rigidity of the system and decrease the degree of phase separation through the formation of an interpenetrating network.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750090209
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