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  • 1
    ISSN: 1432-2072
    Keywords: Morphine ; Cholecystokinin ; Proglumide ; Locomotion ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Proglumide (0.02 mg/kg), a cholecystokinin antagonist, was administered to rats either together with or without morphine (0, 5, 15, or 45 mg/kg). Whereas proglumide in the absence of morphine showed a trend towards enhanced behavioral activation, it potentiated the hy[okinesia induced by morphine. These results are consistent with the hypothesis that endogenous cholecystokinin tonically antagonizes opiate modulation of motility, irrespective of whether such modulation is produced by opiates and endogenous or exogenous origin.
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  • 2
    ISSN: 1573-7217
    Keywords: lonidamine ; mechanism ; multi-drug resistance ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Lonidamine (LND) is a relatively new anti-cancer drug,and several clinical trials have indicated that it may be effectivein combinations with other therapeutic modalities. LND isclassified within the metabolic inhibitor agents. Multidrugresistance (MDR) phenomenon is often associated with increasedenergy requirements, and enhanced glycolysis rate. These studieswere performed to delineate the mechanism of action of LNDon MDR human breast cancer cells, and to investigate whetherLND as a single agent, or in combination with anotheranti-metabolism drug, 2-deoxyglucose (2-DG), may be usefulagainst MDR tumors. The effects of LND on intact perfuseddrug-sensitive (WT) and 33-fold resistant to Adriamycin(Adr) MCF-7 cells, embedded in alginate micro capsules, were continuouslymonitored by 31P and 13C nuclearmagnetic resonance (NMR) spectroscopy. 31PNMR studies showed that LND induced intracellular acidificationand depletion of NTP in both WT and Adr cells. However, pH and NTPlevels decreased less in the Adr cells than in the WT cells(p 〈 0.05 for both parameters). 13CNMR demonstrated that LND inhibited lactate transport,and lactate signals were elevated in both cell lines. However, theintracellular lactate levels increased to a greater extentin the WT than in the Adr cells (p 〈 0.05).There were major differences in the effects of LND onmetabolism between sensitive and resistant cells.While LND enhanced glucose uptake in the WT cells, and itsadministration was followed by continuous increase oflactate signal, both processes were not affected by LNDin the Adr cells. 2-DG is a glucose analogue that inhibitsboth cellular uptake and utilization of glucose, leading to cell starvation. Combined treatment with LND and2-DG yielded at best additive, but not synergistic,cellular toxicity, and the metabolic effects of LNDwere attenuated by 2-DG. These results showed that the principalmechanism of action of LND is inhibition of lactate transportleading to intracellular lactate accumulation and acidificationin both WT and Adr cells. The Adr cells were only 2-fold resistantto LND (compared to the WT cells), and since cellular uptakeof alkaloid chemotherapy is improved in acidic environment,LND may have a role in the treatment protocols of MDR tumors,especially when given as the initial means for inductionof intracellular acidification.
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  • 3
    ISSN: 1434-6079
    Keywords: 36.40 ; 64.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The evolution of thermodynamic, dynamic and quantum size effects in clusters is expected to contribute towards the merging between microscopic and macroscopic points of view in molecular, surface and bulk phenomena.
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  • 4
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 7757-7768 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we advance and apply a molecular theory of pure radiative lifetimes τr of (aromatic molecule)⋅(rare gas)n heteroclusters. The modification of τr in the heterocluster, relative to the bare molecule value, originates from intermolecular interactions between molecular multicenter transition monopoles, which are described by π electron approximation, and the rare-gas atom transition dipoles, which are specified in terms of the static atomic polarizability α. The calculated changes of τr of 9,10 dichloroanthracene⋅A1 (A=Ar, Kr, Xe) heterodimers are in good agreement with experiment; the theory accounting for the nearly linear dependence of the change of τr on α.Calculations of the radiative lifetimes of 9,10 dichloroanthracene⋅Arn (n=1–34) heteroclusters were performed using structural information from potential optimization for small (n=1–3) heteroclusters, static structural data for small and medium-sized (n=1–8) heteroclusters, and (constant energy) finite-temperature molecular dynamics simulations for medium-sized and large (n=5–34) heteroclusters. The structural sensitivity of τr is manifested by different values of τr for distinct structural isomers, by the nonmonotonous size effects on τr with increasing n, and by pronounced decrease of τr with increasing temperature. For medium-sized clusters (n=5–18), the temperature dependence of τr originates from the enhancement of atomic motion on both sides of the aromatic microsurface and the occupation of the peripheral region, while for large clusters (n(approximately-equal-to)34) two layer–one layer isomerization processes with increasing temperature result in dramatic changes of τr. Satisfactory overall agreement between theory and experiment for 9,10 dichloroanthracene⋅Arn n=1–34 heteroclusters was accomplished.The dominating 9,10 dichloroanthracene⋅Arn structures for n=1–18, which yield agreement between theory and experimental for τr, correspond to nearly equal distribution of the rare gases on both sides of the aromatic microsurfaces at T≤20 K, while large n=34 two-layered structures in the temperature domain 22 K≤T≤40 K account for the experimental τr result. τr serves as a useful spectroscopic probe for the interrogation of the structure and isomerization dynamics in heteroclusters.
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 331-339 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we provide an extension of the electrostatic model for the structure and energetics of large van der Waals ions consisting of an aromatic cation bound to rare-gas atoms. We consider the effects of intermolecular electronic overlap on the charge-induced dipole interactions. Model calculations for tetracene⋅R+n (n=1–3 and R=Ar, Kr) and for benzene⋅R+ provide a reasonable account for the ionization potentials of these vdW ions.
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 9346-9351 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we examine the spectral moments of the absorption line shapes of aromatic- molecule⋅(rare gas)n heteroclusters to provide analytic expressions for the spectral shifts (δν), which are determined by the first moment, and for the homogeneous linewidths (Γ), which are determined by the central second moment (Δ) of the line shape. δν originates from the cumulative contributions of dispersive pair interactions, while Δ and Γ manifest the short-range dynamic nuclear fluctuations. Our analysis elucidates some of the general features of these spectroscopic observables, e.g., their dependence on the cluster structure and their size dependence, as well as some of their specific characteristics, e.g., their temperature dependence. We predict a weak temperature dependence of δν (=a+bT with b(very-much-less-than)a/T) and a strong temperature dependence of Δ(∝T1/2), which is borne out by molecular dynamics (MD) simulations. We have derived cluster size equations (CSE) relating the spectroscopic observables of the finite cluster with those of the infinite bulk system. The excluded volume corrections for δν(n)∝n−1 and for Δ(n)∝n−3 are different, in accordance with the nonuniversability principle for CSEs. The predictions of the CSEs concur with experimental and MD simulation data for δν(n) and with MD simulation data for Δ(n). Finally, we have addressed dimensionality scaling of spectroscopic cluster properties, applicable for the situation of a common dimensionality (D≠3) for the cluster and for the infinite bulk. This analysis may be useful for the spectroscopic interrogation of doped clusters of low dimensionality, e.g., wire clusters (D=1) and planar clusters (D=2), as well as fractal clusters, e.g., clusters of porous materials.
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 1848-1853 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Microscopic spectral shifts of the lowest spin-allowed weak 1Lb(α) transitions of heteroclusters consisting of inert-gas atoms bound to naphthalene, phenanthrene, and pyrene were evaluated utilizing the multicenter monopole representation for the dispersive intermolecular interactions, in conjunction with a semiempirical scaling of the Hückel transition monopoles. These calculations predict that the spectral shift for the electronic origin of the 1La(p) transition is higher by a numerical factor of 2–4 than for the weak 1Lb(α) transition, in accord with experiment. The semiempirical theory was applied for the calculation of cluster size and isomer structure dependence of the 1Lb(α) spectral shifts in these heteroclusters.
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 6290-6299 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we report on the electronic two-photon two-color near threshold spectroscopy of mass-resolved perylene⋅Arn (n=1–45), perylene⋅Krn (n=1–35), perylene⋅(N2)n (n=1–12), and perylene⋅(CH4)n (n=1–10) heteroclusters. The S0→S1 inhomogeneously broadened spectra of perylene⋅Arn (n=1–6) and perylene⋅Krn (n=1–4) exhibit resolved spectral features, which were assigned on the basis of experimental combination rules and polarizability relations to the electronic origins of distinct two-sided and one-sided structural isomers. Larger perylene⋅An (A=Ar, Kr; n=6–10) heteroclusters exhibit an "abnormal'' specific size dependence of the red spectral shifts, which decrease with increasing n and reach a local minimum at n=8. Similar characteristics of the red spectral shifts are exhibited for perylene⋅(N2)n and perylene⋅(CH4)n (n=4–8) heteroclusters. This abnormal size dependence of the spectral shifts is attributed to the dominance of one-sided single-layered and double-layered structural isomers in this cluster size domain. On the basis of the comparison between the spectroscopic data and molecular dynamics simulations of the absorption line shapes we have obtained a quantitative description of isomer-specific structures for n=2–6, a semiquantitative description of the abnormal size domain for n=6–10 (due to the dominance of one-sided structures with the abundance of two-layered structures increasing at higher n), the prevalence of one-sided structures for n=16 and n=22, and the realization of two-sided multilayered structures at n=45.
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  • 10
    ISSN: 1432-2072
    Keywords: d-Amphetamine ; Simultaneous discrimination ; Control by S+ and S− ; General transfer ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rats were trained in a Y-maze on a two-choice simultaneous black-white discrimination with either black or white as S+. Animals were then transferred to one of three discrimination tasks. In task 1 (New S−), a new stimulus, either vertical or horizontal stripes, was substituted for the original S−. In task 2 (New S+), a new stimulus, either vertical or horizontal stripes as in task 1, was substituted for the original S+. In task 3 (New S+/S−) animals were trained on horizontal-vertical discrimination. The pre-trial administration of 1 mg/kg d-amphetamine facilitated the acquisition of the original black-white discrimination with both black as S+ and white as S+. Likewise, the drug improved performance in all three transfer conditions. However, the course of learning in the three transfer tasks was different in the placebo- and amphetamine-treated animals. Amphetamine-treated animals were disrupted more by a change in S+ than by a change in S−, whereas the opposite pattern was evident in the placebo controls. When both discriminative stimuli were changed, placebo animals exhibited pronounced decrement in performance, whereas amphetamine animals exhibited excellent learning. The implications of these findings for the effects of amphetamine on discrimination learning are discussed.
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