RESUMO
FMRFa is a molluscan peptide that has shown antiopiate activity in a number of mammalian test systems. The current study determined the antiopiate potency of FMRFa and two conformationally constrained peptidomimetics of FMRFa containing stereoisomers of Z-2,3-methanomethionine. Morphine abstinence signs were observed after varying doses (0.25-25.0 micrograms) of these substances were injected into the third ventricle of morphine-dependent rats. Although both peptidomimetics were far more potent than FMRFa itself, they bound with lower affinity than FMRFa to rat spinal cord receptors for the mammalian FMRFa-like peptide, NPFF.
Assuntos
Endorfinas/antagonistas & inibidores , Neuropeptídeos/farmacologia , Sequência de Aminoácidos , Animais , FMRFamida , Técnicas In Vitro , Masculino , Metionina/análogos & derivados , Dados de Sequência Molecular , Estrutura Molecular , Dependência de Morfina/etiologia , Neuropeptídeos/química , Neuropeptídeos/metabolismo , Oligopeptídeos/química , Oligopeptídeos/metabolismo , Oligopeptídeos/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de Neurotransmissores/efeitos dos fármacos , Receptores de Neurotransmissores/metabolismoRESUMO
FMRFamide is a molluscan peptide that has shown antiopiate activity in a number of mammalian test systems. The current study determined the antiopiate potency of FMRFamide and two conformationally constrained peptidomimetics of FMRFamide containing stereoisomers of (E)-2,3-methanomethionine. Morphine abstinence signs were observed after varying doses (0.25-25.0 microgram) of these substances were injected into the third ventricle of morphine-dependent rats. Both peptidomimetics were far more potent than FMRFamide itself. In addition, although both peptidomimetics bound with lower affinity than FMRFamide to rat spinal cord receptors for NPFF (the mammalian FMRFamide-like peptide), they were far more resistant than FMRFamide to enzymatic degradation by leucine aminopeptidase.
Assuntos
Leucil Aminopeptidase/metabolismo , Metionina/análogos & derivados , Antagonistas de Entorpecentes/farmacologia , Neuropeptídeos/farmacologia , Sequência de Aminoácidos , Animais , FMRFamida , Hidrólise , Masculino , Metionina/análise , Dados de Sequência Molecular , Neuropeptídeos/metabolismo , Oligopeptídeos/metabolismo , Ligação Proteica , Ratos , Ratos Sprague-Dawley , Receptores de Neuropeptídeos/metabolismo , Receptores Opioides/metabolismo , Estereoisomerismo , Síndrome de Abstinência a Substâncias/etiologiaRESUMO
We investigate theoretically the effect of a finite electric field on the resistivity of a disordered one-dimensional system in the variable-range hopping regime. We find that at low fields the transport is inhibited by rare fluctuations in the random distribution of localized states that create high-resistance breaks in the hopping network. As the field increases, the breaks become less resistive. In strong fields the breaks are overrun and the electron distribution function is driven far from equilibrium. The logarithm of the resistance initially shows a simple exponential drop with the field, followed by a logarithmic dependence, and finally, by an inverse square-root law.
RESUMO
A 36-year-old Latin American man with the basal cell nevus syndrome had multiple, soft, hairless, depressed scars of the face, scalp, neck, and back, ranging in size from 0.3 x 0.5 cm to 3.5 x 3.9 cm. These areas had never been treated and previously were sites of basal cell carcinomas that underwent complete spontaneous regression 4-5 years from the date of onset. Pathology of these spontaneously regressed sites was consistent with the criteria established by Curson and Weedon (1979). Type III transepithelial elimination was demonstrated for a basal cell carcinoma. Type III transepithelial elimination may play a role in the spontaneous regression of basal cell carcinomas.