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  • 1
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Psychophysiology 30 (1993), S. 0 
    ISSN: 1469-8986
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: Positron emission tomographic measurements of regional cerebral blood flow (rCBF) were used to investigate central nervous system correlates of fear and anxiety. Volunteers with symptomatic snake phobia were studied while exposed to visual phobogenic, aversive, and neutral stimuli. Anxiety ratings and the number of nonspecific electrodermal fluctuations increased as a function of phobic stimulation. Phobic, compared to neutral and aversive, stimulation elevated rCBF in the visual associative cortex. The basal ganglia were not activated more by phobic than aversive or neutral stimulation. However, cortical and thalamic rCBF were always correlated during phobic but not aversive or neutral stimulation. This indicates that the thalamus could be a relay station for phobic stimulus processing and affect.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1469-8986
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: We investigated central nervous system correlates of simple phobie fear, Regional cerebral blood flow (rcBF) was measured using position emission tomography(PFT) in eight volunteers with symptomatic spider phobia that were exposed to visual phobogenic and neutral stimuli Diazepam (0.1 mg/kg body weight i.v.) or placebo was administered under double blind conditions after initial PFT scans. The PFT scans were then repeated. The presence of fear was confirmed by rating procedures and increased number of nonspecific electrodermal fluctuations and by higher heart rate during phobic than during neutral stimulation. Phobic as compared to neural stimulation elevated the retional to whole brain (relative) CBF in the secondary visual cortex but reduced relative rCBF in the hippocampus, prefrontal, orbitofrontal, ttemporopolar, and posterior cingulated cortex. Dia/epam treatment did not affect the relative rCBF or the subjective or physiological fear indices. The observed rCPF pattern replicates our previous findings in snake phobics (M. Fredrikson et al.[1993] Psychophysiology, 30, 127, 131 G. Wik et al. [1993] Psychiatry Research (Neuroimaging), 50, 15–24) and indicated that fear and anxiety affect cortical areas outside the classic limbie system areas.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 3 (1991), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: This study of somatosensory discrimination of rectangular parallelepipeds with the right hand had three purposes: (i) to describe the exploratory finger movements; (ii) to reveal the anatomical brain structures specifically engaged in the production of exploratory finger movements; and (iii) to reveal the anatomical structures specifically engaged in the discrimination of tactually sensed shape. The thumb was the most active finger, moving with a mean exploration frequency of 2.4 Hz, as evident from videotape records of the exploratory finger movements. The cerebral structures activated during somatosensory discrimination were mapped by measurements of regional cerebral blood flow (rCBF) in six healthy male volunteers with positron emission tomography (PET) and the use of the computerized brain atlas of Greitz et al. (1991, J. Comp. Ass. Tomogr., 15, 26–38). The rCBF changes caused by somatosensory discrimination were compared point-to-point to a PET-study on right-hand finger movements and a PET-study on vibration stimulation of the right hand. From these results the following conclusions were drawn. The rCBF increase in the left superior parietal lobule indicated the site engaged in the analysis of shape. The rCBF increases in the left supplementary sensory area, bilaterally in premotor areas, in the left putamen, the right dentate nucleus and bilaterally in the posterior cerebellum were related to the control of the tactile exploratory finger movements. The rCBF increases in the right homologue of Broca's area, bilaterally in the superior prefrontal cortex and in the right midfrontal cortex probably resulted from working memory, the direction of attention, and the discrimination process.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 1 (1989), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We measured the regional cerebral oxidative metabolism (rCMRO2) with positron emission tomography in normal healthy volunteers in three different stages: rest, tactile learning, and tactile recognition of complicated geometrical objects. The frequency of manipulatory movements during tactile recognition was twice that of tactile learning. Tactile recognition with the right hand increased rCMRO2 in six prefrontal cortical areas, bilaterally in the supplementary motor areas, the premotor areas and supplementary sensory areas, in the left primary motor and primary sensory area, in the left anterior superior parietal lobule, bilaterally in the secondary somatosensory area, the anterior insula, lingual gyri, hippocampus, basal ganglia, anterior parasagittal cerebellum, and lobus posterior cerebelli. These structures have in other studies been found to participate in manipulatory movements and analysis of somatosensory information. Tactile learning increased rCMRO2 in the same structures as did tactile recognition. Thus we found no differences in the anatomical structures participating in storage and retrieval. However the rCMRO2 increases in the left premotor cortex, supplementary motor area, and left somatosensory hand area were larger during tactile recognition in accordance with the higher frequency of manipulatory movements and higher flux of somatosensory information from the periphery during recognition. Despite this the rCMRO2 was significantly higher in the neocerebellar cortex during tactile learning. Since there were no learning effects on the manipulatory movements, this extra metabolic activity in the lateral cerebellum was attributed to energy demanding processes associated with climbing fibre activity during storage of somatosensory information.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0843
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The in vivo distribution of the antileukemic agent busulfan labeled with the positron-emitting radionuclide carbon 11 was investigated in cynomolgus monkeys and in a human patient using positron emission tomography. After i.v. injection of the radiotracer, its regional uptake was monitored for about 1 h in the monkey's body and in a separate experiment, in the monkey's brain. The concentration of radioactivity in the liver, which showed the highest levels of all the organs scanned, increased throughout the experiment and was 9-fold that in the brain at the end of the experiment. [11C]-Busulfan rapidly crossed the blood-brain barrier. The radioactivity peaked in both the cortex and the white matter showing a ratio of 1.25, at 3 min but declined quickly to yield a ratio of approximately 1 after 30 min. In the human brain, radioactivity in the cerebellum, cortex, and white matter reached a maximum within 5 min showing a cortex:white matter ratio of 1.6. The activity in the cortex declined to yield a ratio of 1 within 30 min. Of the delivered dose, 20% penetrated into the brain.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1619-7089
    Keywords: 11C-2-Deoxy-D-glucose ; 11C-D-glucose-metabolism ; PET-positron emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 11C-2-Deoxy-D-glucose has been prepared by the reaction of 11C-hydrogen cyanide with a stable precursor, 1-deoxy-2,3:4,5-di-O-isopropylidine-1-iodo-D-arabitol, thereby avoiding the synthesis of starting material immediately prior to labeling. Fast, efficient, and reproducible solvent change from dimethyl sulfoxide to ether by flash chromatography enabled the use of diisobutylaluminium hydride in the reduction of the intermediate nitrile. Hydrolysis of the imine-aluminum complex with sulfuric acid, removal of the isopropylidine protecting groups with formic acid, and HPLC purification with an Aminex HPX-87P column yielded 11C-2-deoxy-D-glucose in an aqueous solution, sterile, pyrogen-free, and ready for use in human studies. The radiochemical yield was ∼20% after a synthesis time of 50 min. The 11C-2-deoxy-D-glucose thus obtained is presently being compared with photosynthetically prepared 11C-D-glucose in PET studies of cerebral metabolism. A preliminary report of the regional cerebral metabolic rate of glucose obtained with the two tracers in a healthy subject with visual stimulation is presented.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1619-7089
    Keywords: 11C-labelled fluoromethane ; Cerebral blood flow ; Positron emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fluoromethane, previously labelled with 18F and used as a tracer in the measurement of regional cerebral blood flow, was 11C-labelled by the reaction of 11C-methyl iodide with tetraethylammonium fluoride. Sufficient quantities of radiotracer were prepared with a minimum amount of handling from 15 min target irradiations in the 14N(p, α) 11C reaction. Total synthesis time was 25 min from end-of-bombardment, allowing serial blood flow measurements 30 min apart. The use of 11C-fluoromethane as a cerebral blood flow tracer in positron emission tomography is discussed.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1619-7089
    Keywords: 11C-Tyrosine ; d-Tyrosine ; l-Tyrosine ; (1-11C)Tyrosine ; Positron emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The synthesis of d-and l-(1-11C)tyrosine, starting with 11C-cyanide, is reported. dl-(1-11C)Tyrosine was prepared by the Bücherer-Strecker reaction, from carrier added 11C-cyanide with an incorporation of 80% in 20 min. The isolation of the pure d- and l-amino acid isomers from the enantiomeric mixture was accomplished within 15 min by preparative HPLC using a chiral stationary phase and a phosphate buffer as the mobile phase. Typically, the total synthesis time was 50 min (including purification) from end of trapping of 11C-cyanide, with a radiochemical yield of d- and l-amino acid of 40%–60%. The d- and l-(1-11C)tyrosine were both obtained optically pure, with a carrier added specific activity of 0.3–0.5 Ci/mmol and a radiochemical purity better than 99%. The 11C labelled l-tyrosine was used in an in vivo study in the human brain using positron emission tomography (PET).
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1619-7089
    Keywords: Blood-brain transfer of glucose ; Hypoglycaemia ; Michaelis ; Menten ; Positron emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of steady-state moderate hypoglycaemia on human brain homeostasis has been studied with positron emission tomography using [U-11C]-D-glucose as tracer. To rule out any effects of insulin, the plasma insulin concentration was maintained at the same level under normo- and hypoglycaemic conditions. Reduction of blood glucose by 55% increased the glucose clearance through the blood-brain barrier by 50% and reduced brain glucose consumption by 40%. Blood flow was not affected. The results are consistent with facilitated transport of glucose from blood to brain in humans. The maximal transport rate of glucose from blood to brain was found to be 62±19 (mean±SEM) μmol hg−1 min−1, and the half-saturation constant was found to be 4.1 + 2.3 mM.
    Type of Medium: Electronic Resource
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