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  • 1
    ISSN: 1432-1041
    Keywords: Key words Positron emission tomography ; Esuprone; antidepressive drugs ; MAO-A ; moclobemide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: The aim of the study was to investigate whether or not esuprone binds substantially to MAO-A in the human brain. Methods: In a randomised double-blind placebo-controlled study 16 male healthy volunteers were examined␣with positron emission tomography (PET) with [11C]harmine. Eight of the volunteers were given daily doses of 800 mg esuprone, four were given bi-daily doses of 300 mg moclobemide, and four volunteers were given placebo tablets. PET was performed before initiation of a 7-day treatment period. On day 7, one investigation was made immediately before administration of the drug, representing 23 h after the previous day's treatment for esuprone and 11 h after the last tablets of moclobemide. Further investigations were made 4 h and 8 h after the morning dose on day 7. Results: PET showed a high degree of binding of [11C]harmine, a high-affinity ligand for MAO-A, before the start of treatment, and a marked and similar reduction after treatment with esuprone and moclobemide. A slight tendency for normalisation of enzyme binding was observed at the last time point. In the placebo group no change was observed. Plasma kinetics of esuprone showed a rapid elimination with a half-life of about 4 h. Conclusion: The study demonstrates that esuprone was comparable to moclobemide in its effect on MAO-A inhibition in the brain at the doses given. This is an illustration of the potential of PET to monitor drug effects directly on target biochemical systems in the brain in human volunteers, and the possibility of using these data, rather than pharmacokinetic data, for the determination of dosing intervals.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 733 (1994), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1435-1463
    Keywords: Keywords: NMDA-receptor ; cyano-dizocilpine ; positron emission tomography ; in vitro investigation ; in vivo investigation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary. (+)-3-[11C]Cyano-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine ([11C]MKC) was successfully synthesized as a potential radiotracer for PET studies on the NMDA receptor channel complex. In vitro binding properties of [11C]MKC were investigated with newly developed techniques for efficient evaluation of 11C-labeled compounds. The association curve of [11C]MKC binding in rat forebrain membranes showed that the specific binding reached an equilibrium within 30 min. Specific binding was saturable with affinity constant KD = 8.2 ± 0.4 nM and Bmax = 1.62 ± 0.04 pmol/mg protein with glutamate and glycine included in the incubation medium. The binding of [11C]MKC was decreased by extensive washing of the membrane preparation. (+)- and (−)-Dizocilpine, 3-cyano-dizocilpine, and ketamine inhibited the specific binding of [11C]MKC with IC50 values of 37.3, 445.0, 65.8 nM and 3.91 μM, respectively. High specific binding in in vitro autoradiography was distributed predominantly in telencephalic regions (the hippocampus, cerebral cortex, and striatum) followed by thalamus. PET studies using rhesus monkeys under anesthesia showed high uptake of [11C]MKC in the temporoparietal and frontal cerebral cortices, striatum, and thalamic regions, although it is problematic to verify the specific binding in vivo by PET.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1435-1463
    Keywords: Keywords: Brain slice ; positron emitting tracer ; triazolam ; muscarinic acetylcholine receptor ; amnesia.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary. The effect of triazolam, a potent benzodiazepine (BZ) agonist, on muscarinic acetylcholinergic receptor (mAChR) binding was investigated in living brain slices by use of a novel positron-based imaging technique. Fresh rat brain slices were incubated with [11C]N-methyl-4-piperidylbenzilate ([11C]NMPB), a mAChR antagonist, in oxygenated Krebs-Ringer solution at 37°C. During incubation, time-resolved imaging of [11C]NMPB binding in the slices was constructed on the storage phosphor screens. Addition of triazolam (1 μM) plus muscimol (30 μM), a GABAA receptor agonist, to the incubation mixture decreased the specific binding of [11C]NMPB. Ro15-1788, a BZ receptor antagonist, prevented this effect, indicating that the effect was exerted through the GABAA/BZ receptor complex. These results demonstrated that stimulation of the GABAA/BZ receptor lowers the affinity of the mAChR for its ligand, which may underlie the BZ-induced amnesia, a serious clinical side effect of BZ. No such effect in the P2-fraction instead implies that the integrity of the neuronal cells and/or their environment is prerequisite for the modulation of mAChR by GABAA/BZ stimulation.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1434-601X
    Keywords: PACS:21.10.Re Collective levels – 27.60+j 90 ≤ A ≤ 149
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Excited states of the nucleus ν123Xe have been investigated with the fusion–evaporation-reaction ν110Pd(ν18O,5n)ν123Xe at 86 MeV beam energy, using the compton-suppressed Nordball-multidetector-system at the Niels-Bohr-Institute in Risø, Denmark. The level scheme of ν123Xe was extended up to a level of tentative 53/2+ħ. Four excited bands of 3-quasiparticle-character were observed. Analyzing the directional correlation information, we could assign spin- and parity-values to all observed bands in ν123Xe. The observed band structures fit well into systematics of the neighboring nuclei ν125Xe and ν127Xe.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 418 (1991), S. 153-160 
    ISSN: 1432-2013
    Keywords: ATP ; Electrical stimulation ; Force ; Phosphate ; Phosphocreatine ; Relaxation ; Skeletal muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Force and relaxation were measured during electrical stimulation of the quadriceps muscle of 14 volunteers. Stimulation produced 51.2 s of intermittent ischaemic contractions either as 16 3.2-s tetani or as 64 0.8-s tetani. Changes during recovery were followed for 180 s. On 8 subjects muscle biopsies were taken during work and after the rest period for determination of ATP, phosphocreatine and intermediates in glucolysis. The stimulation using 0.8-s contractions gave more pronounced fatigue and slowing of relaxation. There was a good correlation between force and relaxation during work but this relation changed during recovery, indicating that no general relation exists between these two contraction characteristics. In the 0.8-s stimulation more ATP was utilized and there were more profound changes in metabolite levels. We found a correlation between estimated [H2PO 4 − ] and relaxation covering both work and recovery and hypothesize that inorganic phosphate and its removal by phosphocreatine resynthesis during recovery might be important. Since stimulation patterns differ in force and relaxation even after the recovery period we suggest that additional factors, such as pH, are of importance in this work model.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 417 (1990), S. 136-141 
    ISSN: 1432-2013
    Keywords: Electrical stimulation ; Fatigue ; Force ; Frequency ; Skeletal muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Percutaneous electrical stimulation was used to study the force response of the quadriceps muscle. The normal frequency dependence of force was investigated in muscles at rest and after fatiguing contractions. A comparison between force response during fatigue induced by electrical stimulation at different frequencies and by voluntary work suggested equal changes in contractility, irrespective of the fatigue-inducing procedure. In fresh muscle we found a linear relation between stimulation period (10–100 ms) and force. At fatigue the relation changes with maximal deviation from linearity at a 50-ms period (20 Hz). There is a rapid recovery of high frequency force whereas the low frequency response remains low even after 30 min rest. At very low frequencies there is initially unexpectedly high force in fatigued muscle. This could be a result of increased fusion of twitches with initially prolonged relaxation time. To study the twitch summation we compared experimental results in a wide frequency range with computer-simulated twitch summations and present the frequency dependence of summation processes in human quadriceps muscle.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-2072
    Keywords: Key words PET ; Pharmacokinetics ; Dopamine D2 receptor ; Serotonin 5HT2 receptor ; Atypical antipsychotic ; Quetiapine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Quetiapine (Seroquel) is a novel antipsychotic with an atypical profile in animal models and a relatively short plasma half-life of 2.5–5 h. In the present study, we used PET to compare the time course of blockade of dopamine D2 and serotonin 5HT2 receptors of quetiapine using C11-raclopride and C11-N-methyl-spiperone as ligands, parallel to monitoring plasma drug concentrations. It was an open study in 11 schizophrenic men using a fixed dose of 450 mg quetiapine. Eight men completed the 29 days treatment, followed by four PET scans performed over a 26-h period after withdrawal of the compound. Quetiapine was shown to bind to dopamine D2 receptors in striatum and 2 h (tmax) after the last dose, 44% receptor occupancy was calculated. After 26 h it had dropped to the same level as was found in untreated healthy volunteers. Serotonin 5HT2 receptor blockade in the frontal cortex was 72% after 2 h, which declined to 50% after 26 h. The terminal plasma half-life of quetiapine was 5.3 h. Clinically, our eight patients had good antipsychotic effect without any extrapyramidal side-effects. Our data shows that quetiapine has a relatively low affinity for dopamine D2 receptors, with an occupancy half-life (10 h), which was about twice as long as that for plasma. A more prolonged blockade of the serotonin 5HT2 receptors was found in the frontal cortex, with receptor occupancy half-life of 27 h. Compared to clozapine, as demonstrated in other studies, quetiapine has much the same ratio of D2/5HT2 occupancy. This could suggest that the combination of D2/5HT2 receptor blockade contributes to the antipsychotic effect and a low incidence of EPS seen with quetiapine in comparative phase three trials. Our results also confirm the clinical data that quetiapine can be administered twice daily.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1434-601X
    Keywords: 21.10.−K ; 21.60.−n ; 25.70.−z ; 27.70.+q
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The strongly shape driving πh9/2[541]l/2− configuration with α=+1/2 exhibits some anomalous, and so far unexplained, features concerning the crossing frequency, ħωc, the aligned angular momentum, ix, and interaction strength, at the alignment of the first pair of i13/2 quasineutrons in several odd-Z rare earth-nuclei. The h9/2[541]1/2− and h11/2[523]7/2− bands have been studied in the stably deformed rare-earth nucleus163Tm to investigate these features. A difference in band crossing frequency of ∼ 80 keV between the two bands is found. Rotational bands built on these two configurations have been found to cross in the spin range I=25/2–29/2 ħ. Theγ-decay pattern between the two bands is established in the crossing region and analysed in terms of a moderate shape difference between them. A theoretical estimate of the size of the interaction strength between the two bands is presented and compared to the experimental value. The observed band structure in163Tm is very similar to that of167Lu which has 2 protons and 2 neutrons in addition. This observation is discussed in relation to the similarity of the yrast bands of the two even-even “core” nuclei162Er and166Yb, for which theγ-transition energies are identical within ∼0.2 keV below the vi13/2 crossing.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-2161
    Keywords: Key words Skeletal metastases ; PET ; Fluoride ; CT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To characterise the uptake of 18F in skeletal metastases from breast cancer using positron emission tomography (PET) and to relate these findings to the appearance on CT. Patients and design. PET with 18F and CT were performed in five patients with multiple skeletal metastases from breast cancer. The CT characteristics were analysed in areas with high uptake on the PET study. Dynamic PET imaging of the skeletal kinetics of the 18F-fluoride ion were included. Results. The areas of abnormal high accumulation of 18F correlated well with the pathological appearance on CT. Lytic as well as sclerotic lesions had markedly higher uptake than normal bone, with a 5–10 times higher transport rate constant for trapping of the tracer in the metastatic lesions than in normal bone. Conclusion. PET with 18F-fluoride demonstrates very high uptake in lytic and sclerotic breast cancer metastases.
    Type of Medium: Electronic Resource
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