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  • 1
    Electronic Resource
    Electronic Resource
    The effects of caffeine and Ca2+ on rigor tension in triton-treated rat ventricular trabeculae (1992)
    Springer
    Pflügers Archiv 421 (1992), S. 343-349 
    Details
    ISSN: 1432-2013
    Keywords: Cardiac muscle ; Rigor tension ; Ca2+ ; Caffeine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Ventricular trabeculae from rat heart were chemically skinned with Triton-X100, which disrupts all cellular membranes including the sarcoplasmic reticulum. Trabeculae developed a maintained rigor contracture when adenosine triphosphate was withdrawn from the bathing medium. In all preparations, the final level of rigor force developed in the presence of caffeine (10–40 mM) was greater than under control conditions. However, caffeine failed to increase rigor tension when applied after contracture had fully developed. The effect of caffeine on rigor was maximal at about 15 mM; concentrations greater or less than 15 mM were less effective. On average, caffeine decreased the time required to develop half-maximum rigor force. The caffeine-induced potentiation of rigor force occurred in the effective absence of Ca2+ (10−9 M), in solutions strongly Ca2+-buffered with [ethylenebis(oxonitrilo)]tetraaceticacid (10–50 mM). In all preparations, rigor force was found to be independent of [Ca2+] over the range 10−10 M to about 10−7 M. These results suggest that caffeine affects rigor force by a direct effect on the myofilaments via a mechanism that is independent of Ca2+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374222
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of 2,3-butanedione monoxime on initial heat, tension, and aequorin light output of ferret papillary muscles (1990)
    Springer
    Pflügers Archiv 416 (1990), S. 219-221 
    Details
    ISSN: 1432-2013
    Keywords: Cardiac muscle ; butanedione monoxime ; heat production ; aequorin luminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract At low concentrations (up to 5 mM) the compound 2,3-butanedione monoxime (BDM) was found to reduce twitch tension and initial heat production in isolated papillary muscles without significantly affecting the size of the intracellular Ca transient measured with aequorin luminescence. Higher concentrations of BDM caused further inhibition of twitch tension and heat production with a fall in the size of the Ca+ transient. The size of the aequorin transient was 50% of the control value at 15 mM BDM while twitch tension was negligible. These results suggest that BDM selectively inhibits Ca2+ activated force in cardiac muscle at low concentrations with additional effects on intracellular calcium at concentrations above 5 mM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370248
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  • 3
    Electronic Resource
    Electronic Resource
    The effects of lactic acid production on contraction and intracellular pH during hypoxia in cardiac muscle (1993)
    Springer
    Basic research in cardiology 88 (1993), S. 421-429 
    Details
    ISSN: 1435-1803
    Keywords: Cardiac muscle ; hypoxia ; pH ; lactate ; ischaemia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary During hypoxia cardiac contraction declines and there is an intracellular acidosis. We find that, if this acidosis is abolished by decreasing pCO2 there is little restoration of force. Therefore the acidosis is not the major cause of the decline of force. The acidosis may partly result from the generation of lactic acid. No acidosis, is however, seen in isolated cardiac cells. Furthermore a theoretical model shows that lactic acid production would be expected to produce a transient acidosis. We suggest that the observed maintained acidosis may be a consequence of extracellular lactic acid accumulation affecting intracellular pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00795409
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  • 4
    Electronic Resource
    Electronic Resource
    Properties of amorphous and crystallizable hydrocarbon polymers. III. Studies of the hydrogenation of polybutadieneSee this issue, pp. 1183-1210 for Parts I and II, and pp. 1223-1235 for Part IV. (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 17 (1979), S. 1211-1222 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Three methods for hydrogenating anionically prepared polybutadiene (containing about 8% vinyl double bonds) were investigated: homogeneous catalysis (alkylated transition metal salts), heterogeneous catalysis (nickel on kieselguhr; paladium on calcium carbonate), and stoichiometric reaction with in situ generated diimide. The products were characterized by intrinsic viscosity, gel permeation chromatography, infrared spectroscopy, and melt viscosity. Only the heterogeneous catalysts were found to yield completely hydrogenated products without incorporation of foreign groups and without significant change in the large-scale molecular structure of the chain. The 195°C melt viscosity of linear polybutadiene hydrogenated with heterogeneous catalysts is virtually identical with that of linear polyethylene with the same intrinsic viscosity in trichlorobenzene at 135°C. The solid state properties of hydrogenated polybutadiene, containing about 20 ethyl branches/1000 main chain atoms, closely resemble those of commercial branched polyethylene.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.180170706
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  • 5
    Electronic Resource
    Electronic Resource
    Properties of amorphous and crystallizable hydrocarbon polymers. I. Melt rheology of fractions of linear polyethyleneParts II, III, and IV of this series appear on pp. 1197-1235 in this issue. (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 17 (1979), S. 1183-1195 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamic moduli G′(ω) and G″(ω) for two groups of linear polyethylene fractions (reported Mw/Mn 〈 1.2) were measured in the melt state using the eccentric rotating disk method. Values of zero shear viscosity η0 were obtained and compared with published results on similar fractions. Molecular weight data were converted to a common basis through intrinsic viscosities in trichlorobenzene (TCB) at 135°C. With recent data on Mw (light scattering) vs. [η]TCB, for linear polyethylene, the relationship at 190°C, η0 = 3.40 × 10-14(Mw)3.60, was obtained. The flow activation energy Ea was 6.4 kcal (T = 140-195°C). The plateau modulus G0N at 190°C was determined from the area under the loss modulus peak in one high-molecular-weight sample. The value obtained, G0N = 1.58 × 107 dyn/cm2, corresponds to an apparent molecular weight between entanglements of 1850. The storage compliance J′(ω) becomes anomalously large at low frequencies. The recoverable compliance J0e could not be determined for any of the fractions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.180170704
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  • 6
    Electronic Resource
    Electronic Resource
    Properties of amorphous and crystallizable hydrocarbon polymers. II. Rheology of linear and star-branched polybutadieneParts I, III, and IV of this series may be found on pp. 1183-1195 and pp. 1211-1235 in this issue. (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 17 (1979), S. 1197-1210 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Some results are reported on the linear viscoelastic properties of polybutadienes with narrow-molecular-weight distributions. The zero shear viscosity η0 varies as M3.4 in the linear samples, and viscosity enhancement is found in star-branched samples with long arms, in good agreement with results reported earlier by Kraus and Gruver. The temperature coefficient of viscosity appears to be slightly larger in stars when the arms become long. The steady state recoverable compliance J0e is 2.1 × 10 -7 cm2/dyn in linear samples of high molecular weight, but it increases to values as much as 10 times larger in the stars. The plateau modulus G0N, obtained from a composite curve for the linear samples, is 1.32 × 107 dyn/cm2. The terminal relaxation spectrum of the stars is too broad to allow an evaluation of plateau modulus.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.180170705
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  • 7
    Electronic Resource
    Electronic Resource
    Novel preparation of pure β-TiCl3 and its use in isoprene polymerization (1969)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 7 (1969), S. 707-713 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of the reaction product of TiCl4, Al, AlCl3, and an aromatic compound with an ether and subsequently with TiCl4 yields very pure β-TiCl3. This material, when treated with small amounts of aluminum trialkyls, is a very active catalyst for the stereospecific polymerization of isoprene. If the above reaction is stopped after the ether addition, before the addition of TiCl4, the product so obtained is largely TiCl2. Reaction variables in the preparation of TiCl3 are described as is the effect of various organoaluminum compounds as cocatalysts for polymerization.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1969.150070223
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  • 8
    Electronic Resource
    Electronic Resource
    Monitoring polymer surface derivatization by RBS and ESCA (1984)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 3367-3381 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rutherford backscattering spectrometry (RBS) has been used to detect and quantitate the thallium concentration resulting from the thallous ethoxide derivatization of phenol and carboxylic acid groups contained in the surface region of bisphenol-A polycarbonate (PC) sheet. Hydrolysis of the PC surface prior to derivatization leads to increased thallium levels, in which the chemical nature of the thallium is shown to be of the form R-O-Tl (R = alkyl or aromatic) by electron spectroscopy for chemical analysis (ESCA). Similar trends in thallium concentrations were observed by both RBS and ESCA for PC surfaces that had been exposed for increasing lengths of time to accelerated weathering and outdoor Florida conditions. The detection limit for thallium in PC using RBS is ca. 5 × 1013 atoms/cm2. The diffusion of thallous ethoxide and transesterification of the aromatic carbonate linkage led to a thallium-containing layer 300-700 Å thick, which increased the experimental uncertainty when assaying residual uncapped polymer chains in unweathered material. During the course of the RBS analysis, the interaction of 2-MeV 4He+ with the PC substrate caused dramatic chemical and physical changes. Microscopy and profilometry indicate that a crater was formed having the same cross-sectional area as the incident ion beam with a depth (ca. 0.3-1.5 μ) that varied according to the beam energy and integrated charge. ESCA analysis provided evidence for the loss of the carbonate linkage and the appearance of carbonyl and ester groups. Infrared analysis of the crater bottom shows the appearance of O-H stretch, carbonyl functionality other than aromatic carbonate, and enhanced aromatic ring stretch vibrations. Crosslinking and subsequent densification of the polymer matrix are though to be responsible for the observed morphological changes. It is suggested that this beam-induced damage does not prohibit the use of RBS to measure high-Z elements on a PC matrix since quantitation of 1000-Å Au layers on silicon and PC gave identical results.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1984.170221152
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