1,721,706 research outputs found
Biodistribution, dosimetry, metabolism and monkey PET studies of [18F]GBR 13119. Imaging the dopamine uptake system in vivo
Get PDFThe in vivo charactersitics of a new radiotracer, [18F]GBR 13119, have been examined. Full body biodistribution in rats has been determined and the expected human dosimetry calculated. Pharmacological specificity of in vivo regional brain distribution in rats was examined. Blockage of specific binding was accomplished by dopamine reuptake inhibitors but no effect was observed for pretreatment with serotonin or norepinephrine reuptake inhibitors. Preliminary examination of rat blood shows the presence of radiolabeled metabolites, which can be rapidly identified using bonded-phase (Sep-Pak) chromatography. Finally, the striatum of living primates has been imaged using PET and i.v. administration of [18F]GBR 13119. These results represent the intermediate steps in the development of [18F]GBR 13119 as a radiotracer for the study of the dopamine uptake system in man.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28208/1/0000661.pd
In vivo binding of [18F]GBR 13119 to the brain dopamine uptake system
Get PDFRegional rat brain uptake of [18F]GBR 13119, a high specific activity, positron-emitter labeled derivative of the potent dopamine uptake antagonist GBR 12935, is reported. Striatum to cerebellum ratios of 3 are obtained at 90 minutes post injection. Specific binding in striatum can be blocked by pretreatment with dopamine uptake system antagonists (mazindol, nomifensine) but not with receptor antagonists (spiperone, flupenthixol). [18F]GBR 13119 is proposed as a new positron-emitting radioligand for in vivo PET studies of the pre-synaptic dopamine uptake system.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27608/1/0000652.pd
In vivo binding of the dopamine uptake inhibitor [18F]GBR 13119 in MPTP-treated C57BL/6 mice
Get PDFThe in vivo regional distribution of [18F]GBR 13119 (1-[(4-[18F]fluorophenyl(phenyl)methoxy)ethyl]-4-(3-phenylpropyl) piperazine), a specific dopamine reuptake inhibitor, was examined in brains of C57BL/6 mice after MPTP treatment. At 2 weeks post MPTP the in vivo specific binding of [18F]GBR 13119 in striatum was decreased 63% relative to age and sex-matched controls. Animals studied at 6 and 8 weeks after MPTP treatment showed a gradual recovery of specific [18F]GBR 13119 binding in the striatum. No significant changes were observed in binding of radiotracer to cerebellum or cortex after MPTP treatment, nor were age-related changes observed in control mice. In vivo radiotracer studies thus appear useful for following gradual changes in the dopamine uptake system of mouse brain after neurotoxin treatment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29646/1/0000735.pd
Repeated reserpine administration reduces in vivo [18F]GBR 13119 binding to the dopamine uptake site
Get PDFThe effects of repeated reserpine on the in vivo regional brain distribution of [18F]GBR 13119 (1-[(4-[18F]fluorophenyl)(phenyl)methoxy)ethyl]-4-(3-phenylpropyl)piperazine), a dopamine uptake inhibitor, have been examined. Repeated parenteral administration of reserpine (2 mg/kg i.p., once daily for three days) causes a decrease of the in vivo specific binding of [18F]GBR 13119 in mouse striatum, consistent with a down-regulation of available uptake sites in response to dopamine depletion. These results indicate that modification of endogenous dopamine concentrations, either due to pathological disturbance or pharmacological interventions, may affect in vivo studies of the dopamine uptake system using radioligands of the 1,4-dialk(en)ylpiperazine class, and complicate the interpretation of in vivo human studies of these radioligands using positron emission tomography.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30038/1/0000406.pd
Regional brain distribution of [18F]GBR 13119, a dopamine uptake inhibitor, in CD-1 and C57BL/6 mice
Get PDFWe have examines the regional brain distribution of [18F]GBR 13119 (18F: [beta]+, T1/2 = 110 min), a dopamine uptake inhibitor, in CD-1 and C57BL/6 mice. High levels of binding are observed in the striatum of both species, with striatum/cerebellum ratios of 3-4 at 60 min after injection of the radiotracer. Striatum radioactivity and striatum/cerebellum ratios are more than 50% reduced in C57BL/6 mice treated chronically with the neurotoxin MPTP. We conclude mice are an appropriate model for the in vivo study of the dopamine uptake system, and that [18F]GBR 13119 may be a suitable in vivo marker for degeneration of striatal dopaminergic neurons.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27847/1/0000258.pd
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Aryltrimethylammonium trifluoromethanesulfonates as precursors to aryl [ 18 F]fluorides: Improved synthesis of [ 18 F]GBR‐13119
Get PDFAromatic nucleophilic substitution of various trimethylammonium trifluoromethanesulfonates with [ 18 F]fluoride has been evaluated. Fluorinations were studied over a temperature range of 45–165°C, with decay corrected yields ranging from 20–80%. [ 18 F]GBR 13119, 1‐[2‐{(4‐[ 18 F]fluorophenyl)(phenyl)methoxy}ethyl]‐4‐(3‐phenylpropyl)piperazine, a potential radio‐tracer for the dopamine uptake system, has been prepared in no‐carrier‐added form from 4‐N,N,N,‐trimethylaniliniumphenylmethanone trifluoromethanesulfonate. Purification by solid‐phase techniques yielded the product in 20% decay corrected radiochemical yield and >98% radiochemical and chemical purity without HPLC.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90072/1/2580270711_ftp.pd
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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