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  • 1995-1999  (11)
  • Polymer and Materials Science  (5)
  • Theoretical, Physical and Computational Chemistry  (5)
  • Rat
  • 1
    Electronic Resource
    Electronic Resource
    Acute and chronic effects of nornicotine on locomotor activity in rats: altered response to nicotine (1999)
    Springer
    Psychopharmacology 145 (1999), S. 442-451 
    Details
    ISSN: 1432-2072
    Keywords: Key words Nicotine ; Nornicotine ; Behavioral sensitization ; Locomotor activity ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rationale: Nicotine, a tobacco alkaloid, is known to be important in the acquisition and maintenance of tobacco smoking. Nornicotine, an active nicotine metabolite, stimulates nicotinic receptors and may produce psychomotor effects similar to nicotine. Objective: The present study determined the effects of acute and repeated administration of nornicotine on locomotor activity and compared its effects with those of nicotine. Methods: R(+)-Nornicotine (0.3–10 mg/kg), S(–)-nornicotine (0.3–10 mg/kg), S(–)-nicotine (0.1–1 mg/kg) or saline was administered s.c. to rats acutely or repeatedly (eight injections at 48-h intervals). Activity was recorded for 50 min immediately after each injection. Results: S(–)-Nicotine produced transient hypoactivity, followed by dose-related hyperactivity. Repeated S(–)-nicotine administration resulted in tolerance to the hypoactivity and sensitization to the hyperactivity. Subsequent testing following a saline injection revealed evidence of conditioned hyperactivity. Acute administration of 0.3 mg/kg or 1 mg/kg R(+)- or S(–)-nornicotine produced no effect. Transient hypoactivity was observed at 3 mg/kg and 10 mg/kg R(+)-nornicotine and at 10 mg/kg S(–)-nornicotine. However, rebound hyperactivity was not observed following acute administration of either nornicotine enantiomer, suggesting that nornicotine-induced psychomotor effects differ qualitatively from those of S(–)-nicotine. Repeated R(+)-nornicotine resulted in tolerance to the transient hypoactivity, however hyperactivity was not observed. Repeated S(–)-nornicotine resulted in tolerance to the hypoactivity and the appearance of hyperactivity. Repeated administration of either nornicotine enantiomer resulted in a dose-dependent alteration in response to a 1 mg/kg S(–)-nicotine challenge, suggesting some commonalities in the mechanism of action. Conclusion: Nornicotine likely contributes to the neuropharmacological effects of nicotine and tobacco use.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130051079
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of poly(vinylcyclohexane) derivatives (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1527-1536 
    Details
    ISSN: 0887-6266
    Keywords: polymer hydrogenation ; poly(vinylcyclohexane) derivatives ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Six nearly monodisperse substituted poly(styrene) homopolymers, poly(styrene) (PS), poly(2-methylstyrene) (P2MS), poly(3-methylstyrene) (P3MS), poly(4-methylstyrene) (P4MS), poly(tertiary-butylstyrene) (PtBS), and poly(α-methylstyrene) (FαMS) were anionically polymerized and subsequently saturated using heterogeneous hydrogenation techniques to poly(vinylcyclohexane) (PVCH), poly(2-methylvinylcyclohexane) (P2MVCH), poly(3-methylvinylcyclohexane) (P3MVCH), poly(4-methylvinylcyclohexane) (P4MVCH), and poly(tertiary-butylvinylcyclohexane) (PtBVCH), respectively. In each case, except PαMS, the materials were saturated to 〉 99% conversion with no chain degradation. PS hydrogenations required the addition of small amounts of tetrahydrofuran to the reaction solvent cyclohexane to enhance miscibility and eliminate large-scale chain degradation. Density gradient and differential scanning calorimetry (DSC) measurements were used to characterize the density and glass transition temperature, Tg, of the unsaturated and saturated polymers. Saturation reduces the density by 3% to 11% and changes Tg substantially. The greatest variation in Tg is obtained with the 3-methyl substituted species where a 63°C increase is observed, while the highest measured Tg is 186°C for P2MVCH. Small-angle neutron scattering (SANS) experiments on binary mixtures of hydrogenous and deuterium labeled PVCH derivatives provided a determination of bulk chain statistics. The statistical segment length is relatively insensitive to vinylcyclohexane ring substitution, except with P3MVCH where a 20% greater value is obtained. ©1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090331010
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  • 3
    Electronic Resource
    Electronic Resource
    Studies on microgels, 3Part 2: L. Pille, A. G. Jhingran, E. P. Capareda, D. H. Solomon, Polymer 37, 2459 (1996).. Synthesis using living free radical polymerization (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 18 (1997), S. 755-760 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Microgels which are soluble crosslinked polymer networks have been prepared using the nitroxide living free radical polymerization methodology. When heated in the presence of tert-butylstyrene and 1,4-divinylbenzene, the alkoxyamine 1 derived from 2,2′-azoisobutyronitrile (AIBN) afforded a high molecular weight soluble polymer which was shown by size exclusion chromatography in conjunction with an on-line multi angle laser light scattering (MALLS) detector to have microgel properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1997.030180901
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  • 4
    Electronic Resource
    Electronic Resource
    The reaction of n-butyllithium with benzoic acid: is nucleophilic addition competitive with deprotonation?Dedicated to Frederick G. Bordwell for his many and continuing contributions to physical organic chemistry (1997)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 10 (1997), S. 537-541 
    Details
    ISSN: 0894-3230
    Keywords: n-Butyllithium ; benzoic acid ; nucleophilic addition ; deprotonation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: ---An evaluation of a branching vs sequential mechanism for the reaction of benzoic acid with n-butyllithium favors the latter. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Diffusive properties of immature articular cartilage (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 132-138 
    Details
    ISSN: 0021-9304
    Keywords: immature cartilage ; solute diffusion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The diffusive properties of immature bovine articular cartilage were determined using two different-sized, uncharged solutes (glucose 180 Da, and dextran 10k Da). Radioactively tagged glucose and dextran were diffused into the cartilage for transport times of 5, 15, and 60 min, and the diffusion and partition coefficients were calculated by fitting the experimental data to a one-dimensional diffusion model. The diffusion and partition coefficients for the two solutes averaged 6.08 ± 2.19 and 5.09 ± 2.51 (×10-6 cm2/s) and 0.712 ± 0.149 and 0.615 ± 0.120, respectively. Both coefficients were significantly greater for glucose compared to the larger dextran. While no statistical differences could be found in the diffusive properties of these solutes in immature cartilage compared to their diffusive properties in mature cartilage, there was some evidence that the larger dextran solute might diffuse faster in the earlier time periods. Finally, the bulk fluid contents between the two types of cartilage were not different even though the immature tissue was significantly thicker (1.6 times) than the mature tissue. Our results indicate that the solute diffusion properties of articular cartilage, at least with respect to uncharged solutes, do not change during skeletal maturation. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 132-138, 1998.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Wear testing of materials and surfaces for total knee replacement (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 33 (1996), S. 159-175 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A simple wear test was investigated for evaluating the wear and damage of material pairs when used in total knee replacement. The test consisted of an axially loaded metallic femoral indentor and a reciprocating ultrahigh molecular weight polyethylene (UHMWPE) flat disk that represented the tibial component. A number of variables were studied including the effect of conformity by varying the radii of the femoral surface, distilled water or serum as a lubricant, different femoral materials, and different types of UHMWPE. In general, the different morphologies of the surface wear of the UHMWPE were similar to those seen on retrieved total knee replacements. Increased conformity with a cylindrical indentor gave a reduced wear rate initially, compared with that of the lower conformity spherical indentor. However, the wear rates were similar subsequent to this initial wearing in phase. Transfer films of UHMWPE were observed on the cobalt-chrome indentors for both serum and distilled water lubrication, although this film was more extensive for distilled water. The lowest wear rate was observed when oxidized zirconium was used on the femoral side, which was attributed to greater wettability, surface hardness, and immunity to oxidative wear. Tests using cobalt-chrome femoral cylinders and different grades of UHMWPE showed different wear rates. Of these PEs, GUR 415 showed less wear than both RCH 1000 and UHMWPE containing numerous fusion defects. For the latter, wear was attributed to a fatigue mechanism, although in most cases it was associated with surface phenomena rather than subsurface cracking. However, in some specimens of UHMWPE subsurface crack propagations occurred with defects. The test method is discussed in relation to its applicability to the evaluation and comparison of bearing materials and surfaces, with particular application to total knee replacements. © 1996 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Rotary bending fatigue of coils and wires used in cardiac lead design (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 43 (1998), S. 21-37 
    Details
    ISSN: 0021-9304
    Keywords: bending fatigue ; coil flexure ; lead design ; drawn filled tube ; MP35N ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Implantable electrical conductor wires and coils of MP35N and drawn MP35N tube filled with a silver core (DFT) were tested in rotary bending to evaluate fatigue characteristics and failure mechanisms. Detailed stress analysis enabled evaluation of helical coil fatigue in bending with respect to theoretical stress. The relations between the maximum cyclic stress (S) and the cycles to failure (N) were obtained by introducing cyclic stresses on over 600 samples. Microscopic evaluation using scanning electron microscopy was performed to identify failure mechanisms. The results show that the stress analysis presented is a viable means for assessing the stress state in a composite coil structure in rotary loop testing, comparable S-N fatigue data sets for MP35N and DFT conductors are not consistently significantly different, S-N relationships for coils and wires of the MP35N and DFT appear to lie on the same curves, and failures of all sample types initiate on the outside surface of the wire. Differences in crack propagation and final fracture are shown as a function of sample type and cyclic stress. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 21-37, 1998
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Application of a simple diagonal force field to the simulation of cyclopentane conformational dynamics (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 1541-1548 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Molecular dynamics simulations have been carried out on the cyclopentane molecule using a diagonal force field and the results compared with both experiment and a recent study which used the MM3 force field [W. Cui, F. Li, and N. L. Allinger, J. Am. Chem. Soc., 115, 2943 (1993)]. The current simulation resulted in an RMS pseudorotational velocity of 1036 deg/ps, compared to the model estimated value of 400 deg/ps and the MM3 result of 1700 deg/ps. The pseudorotation amplitude was calculated to be 0.46 ± 0.02 Å, compared to the experimental value of 0.48 Å and the MM3 value of 0.5 ± 0.03 Å. The two distinct average C(SINGLE BOND)H bond lengths seen for the axial and equatorial conformations in the MM3 simulation were not observed. The energy barrier to passing through the planar conformation was calculated at 4.7 kcal/mol as compared to the experimental value of 5.2 kcal/mol and the MM3 value of 4.2 kcal/mol. During the simulation, the angle bending term dominated the potential energy, followed by the torsion energy, as was seen with MM3. The third largest energy term was the bond stretching, followed by the van der Waals interaction, the reverse of what was seen with MM3. The effects of carrying out the simulation under conditions of constant energy versus constant temperature are discussed. © 1996 by John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.5
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  • 9
    Electronic Resource
    Electronic Resource
    Free energy calculation methods: A theoretical and empirical comparison of numerical errors and a new method qualitative estimates of free energy changes (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 18 (1997), S. 902-919 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We present a comparison of four free energy calculation methods: thermodynamic integration (TI); traditional free energy perturbation (FEP); Bennett's acceptance ratio method (IPS); and a method that is related to an implementation of the WHAM method (CRS). The theoretical bases of the methods are first described, then calculations of the solvation free energies of methane and ethane are performed to determine the magnitude of the errors for the different methods. We find that the methods give similar errors when many intermediate states (windows) are used, but the IPS and CRS methods give smaller errors than the TI and FEP methods when no intermediate states are used. We also present a new procedure (based on the CRS method) that uses coordinates from simulations of a set of solutes to calculate the salvation free energies of additional solutes for which no simulations were performed. Solvation free energies for nine solutes (methanol, dimethylether, methylamine, methylammonium, dimethylamine, fluoromethane, difluoromethane, trifluoromethane, and tetrafluoromethane) are estimated based only on simulations of set of small hydrophobic solutes (including methane, ethane, and propane). These estimates can be surprisingly accurate and appear to be useful for making rapid estimates of solvation free energies. © 1997 by John Wiley & Sons, Inc. J Comput Chem 18: 902-919, 1997
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Advancing beyond the atom-centered model in additive and nonadditive molecular mechanics (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 18 (1997), S. 1632-1646 
    Details
    ISSN: 0192-8651
    Keywords: force field ; electrostatics ; hydrogen bonding ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A computational approach to the inclusion of off-center charges in both additive and nonadditive molecular mechanics calculations is presented. The additional sites in the molecular skeleton are placed in the approximate locations of the chemically intuitive electron lone pair, and are treated as formal particles throughout the calculation. The increase in the number of charge sites results in overall improvement in the energy associated with the angular dependence of hydrogen bonds and improved statistical accuracy of the electrostatic potential derived charges. The addition of lone pairs also results in improved accuracy in relative solvation free energy calculation for the pyridine to benzene and methanol to methane mutations. Because the number of atoms that require lone pairs is small, the extra accuracy can be achieved with little computational overhead.   © 1997 John Wiley & Sons, Inc.   J Comput Chem 18: 1632-1646, 1997
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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