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  • 1
    ISSN: 1432-1106
    Keywords: Key words Substantia nigra ; MPTP ; Parkinsonism ; Primate ; Electrophysiology ; Basal ganglia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The basal ganglia are currently viewed as components of segregated corticosubcortical reentrant circuits. One of these circuits, the ”motor” circuit, is critically involved in the development of parkinsonian motor signs. Current pathophysiologic models postulate that parkinsonism is associated with increased activity in the basal ganglia output nuclei. The neuronal activity in the motor portion of one of these output nuclei, the internal segment of the globus pallidus (GPi), has been characterized in detail in intact and parkinsonian animals, but the neuronal activity in the second major basal ganglia output nucleus, the substantia nigra pars reticulata (SNr), has received far less attention. This study in primates represents a comparison of the effects of parkinsonism, induced by injections of the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), on the neuronal discharge in the GPi and SNr. These electrophysiologic recording experiments were carried out in three African green and two rhesus monkeys. One hundred and twenty-four neurons were recorded in the GPi before treatment with MPTP, and 93 neurons thereafter. In the SNr, 55 cells were recorded before treatment with MPTP, and 41 cells thereafter. MPTP induced a non-significant increase in the average discharge rate and a significant decrease in the median interspike interval length (ISI) in the GPi (by 13%), whereas no changes were detected in either parameter in the SNr. The average ISI distributions were markedly asymmetric in both structures, and could be modeled by a logarithmic normal distribution. With the MPTP treatment, the mode of the ISI distribution fell by 24% in the GPi (P≤0.01), whereas it did not change significantly in the SNr. An algorithm that detects burst discharges in the raw ISI data (based on the method by Legendy and Salcman) detected a significant increase in the proportion of action potentials that participated in bursts of discharge in both structures (increase by 257% in the GPi, and by 67% in the SNr). Power spectral and autocorrelation analysis revealed that treatment with MPTP increased the proportion of cells with oscillatory burst patterns at 3–8 Hz in both structures (from 0.8% to 27% of all neurons in the GPi, and from none to 10% in the SNr). The results show that neuronal discharge in the SNr is affected in parkinsonism, but that the changes in the SNr are less pronounced then those seen in the GPi.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 12 (1966), S. 205-207 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 3
    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 stress-strain (S/S) and the swelling equilibrium behavior in a series of ethylene propylene rubber (EPR) and ethylene propylene diene monomer (EPDM) networks were investigated and the results were employed to evaluate the effects of varying the cure conditions on the crosslinking efficiency in these networks. The S/S curve of completely swollen vulcanizates is in agreement with the predictions of rubber elasticity theory, while that of dry or partially swollen vulcanizates is fully described by the Mooney-Rivlin equation. ϰ values determined in benzene were found to vary linearly with vr (vr = equilibrium volume fraction of rubber in swollen sample). Crosslinking efficiency, moles of crosslinks produced per moles of crosslinking agent used, ranges from 3.7 in peroxide-cured EPDM (55% wt ethylene and 2.6% unsaturation) to 0.15 in similarly cured EPR (43% ethylene). Efficiency in the latter system improves to 0.6 by addition of a coagent (sulfur) to the cure formula. Crosslinking efficiency in EPDM (55% ethylene) was found to increase in the order: peroxide- 〉 resin- 〉 sulfur-cured. In the EPDM sulfur vulcanizates, changing the terpolymer in the cure formula resulted in significant changes in the crosslinking efficiency.
    Additional Material: 5 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: An improved stress-strain (S/S) method based on rubber elasticity theory and swelling equilibrium measurements was used to investigate the S/S behavior and the solvent swelling properties of nitrile-butadiene rubber (NBR) and also to study the effects of varying the cure agent and the curing conditions on the crosslinking efficiency in NBR vulcanizates. The S/S curve of completely swollen NBR vulcanizates is, as expected, in agreement with rubber elasticity theory, while that of dry or partially swollen vulcanizates is well described by the Mooney-Rivlin equation. Determined in benzene, χ was 0.494, compared to 1.338 in cyclohexane and 2.124 in n-heptane. The degree of crosslinking and the crosslinking efficiency in the NBR vulcanizates, moles of crosslinks produced per mole of crosslinking agent employed in the formula, are largely dependent on the nature of the crosslinking agent used and increase in the following order: peroxide, sulfur tetramethylthiuram disulfide, sulfur N-cyclohexyl-2-benzothiazolesulfenamide, sulfur benzothiazyl disulfide, and finally tetramethylthiuram disulfide.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 7 (1969), S. 529-533 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 13 (1982), S. 115-119 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polarized Raman spectra of aqueous solutions of Mg(NO3)2 have been obtained over the concentration range 0.05 m to 4.0 m. The Fourier transform of the isotropic band profile of the v1 symmetrical stretching frequency of the nitrate ion gives evidence of more than one component. A technique is described to obtain information on the number of component bands and their relative intensities. The bands were subject to component analysis and the results are discussed in terms of three main solution species. The association constant for the formation of solvent separated ion pairs is calculated to be ∼ 2 dm3 mol-1. Evidence is presented for the presence of contact ion pairs at all concentrations above 2 M.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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