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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We have studied the characteristics of carbon-11 labeled pyrilamine as a radioligand for investigating histamine H1 receptors in human brain with positron emission tomography (PET). [11QPyrilamine is distributed evenly in proportion to cerebral blood flow at initial PET images. Later (after 45–60 min), 11C radioactivity was observed at high concentrations in the frontal and temporal cortex, hippocampus, and thalamus, and at low concentrations in the cerebellum and pons. The regional distribution of the carbon-11 labeled compound in the brain corresponded well with that of the histamine H1 receptors determined in vitro in autopsied materials. In six controls, the frontal and temporal cortices/cerebellum ratio increased during the first 60 min to reach a value of 1.22 ± 0.071. Intravenous administration of d-chlorpheniramine (5 mg) completely abolished the specific binding in vivo in the frontal cortex and temporal cortex (cortex/cerebellum ratio, 0.955 ±0.015). The availability of this method for measuring histamine H1 receptors in vivo in humans will facilitate studies on neurological and psychiatric disorders in which histamine H1 receptors are thought to be abnormal.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-7373
    Keywords: malignant glioma ; recombinant human tumor necrosis factor-α ; positron emission tomography ; hemocirculation ; glucose metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cerebral hemocirculation and glucose metabolism in a malignant astrocytoma were repeatedly quantified before and after intracarotid injection of recombinant human tumor necrosis factor-α (rH-TNF) using positron emission tomography (PET). The patient received an intracarotid injection of a 3 × 104 U/m2 dose of rH-TNF three times over a two week period. PET was performed prior to and 24 hr after the first injection, and two weeks after the third injection. Prior to the first rH-TNF treatment, two lesions demonstrating high perfusion and hypermetabolism of glucose were noted in the right frontal and temporal regions. The frontal hypermetabolic lesion showed decreases in hemocirculation and metabolism 24 hr after the first injection and then increases beyond the pre-treatment level two weeks after the third treatment, whereas the temporal lesion remained unchanged during the follow-up period. No appreciable changes were noted in the adjacent cortex where rH-TNF was perfused, with the exception of a transient decrease in regional blood volume. Magnetic resonance images of the tumor showed no changes as a result of treatment with intracarotid rH-TNF. Intracarotid rH-TNF preferentially affects tumor tissue as opposed to normal cortex.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1619-7089
    Keywords: Carbon-11 methionine ; Positron emission tomography ; Glioma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to evaluate the methionine uptake of a glioma with positron emission tomography (PET), the kinetics of carbon-11 methionine was investigated in 11 patients by measuring the free 11C-methionine in plasma as an input function following intravenous administration. When the mean clearance curve of free 11C-methionine in plasma instead of individual 11C-methionine clearance curves was used, mean differences in uptake rate and distribution volume were 4.0% and 4.6% respectively. By applying the mean clearance curve of free 11C-methionine in 18 glioma patients, significant differences in 11C-methionine uptake rate and distribution volume were found according to pathological grading. For the accurate evaluation of the metabolism of 11C-methionine, it is therefore preferable that the actual level of free 11C-methionine in the plasma be measured, especially for the follow-up of individual cases. The study also demonstrated that the mean clearance curve of 11C-methionine in plasma might be employed as an input curve for calculating the uptake rate and distribution volume with small errors.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1619-7089
    Keywords: [11C]Dimethyltryptamine ; Serotonin receptors ; Positron
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The endogenous hallucinogen, N,N-dimethyltryptamine (DMT), was labeled with carbon-11 and its regional distribution in rat brain studied. [11C]DMT showed higher accumulation in the cerebral cortex, caudate putamen, and amygdaloid nuclei. Studies of the subcellular distribution of [11C]DMT revealed the specific localization in the fractions enriched with serotonin receptors only when a very low dose was injected into rats. The proportions of the radioactivity in receptor-rich fractions were greatly enhanced by pretreatment with the monoamine oxidase inhibitor, pargyline. Specific binding of [11C]DMT to serotonin receptors in dog brain was demonstrated by a positron emission tomographic study in which 5-methoxy-N,N-dimethyltryptamine caused approximately 20% displacement of the radioligand from the receptors.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1619-7089
    Keywords: Positron emission tomography ; Fluorine-18 fluorophenylalanine ; Cerebral gliomas ; Large neutral amino acid transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To elucidate the mechanism of large neutral amino acid (LNAA) transport in cerebral gliomas and to evaluate the clinical usefulness of positron emission tomography (PET) with fluorine-18 fluorophenylalanine (18F-Phe), we examined 18 patients with cerebral glioma using dynamic PET and18F-Phe. By employing two-compartment model analysis, the influx rateK 1, the efflux ratek 2 and the distribution volume (V d) of18F-Phe were estimated in tumour tissue and contralateral normal grey matter.18F-Phe showed increased accumulation in tumour tissue regardless of the grade of malignancy in all patients. The rate of uptake of18F-Phe in high-grade glioma was significantly higher than in low-grade glioma (P 〈0.05). However, it was difficult to evaluate the tumour grade only from the18F-Phe accumulation in individual cases. Values ofK 1 andV d were significantly increased in the tumour tissue. TheK 1 value of the tumour tissue tended to decrease with increasing LNAA concentration in plasma. Therefore, influx of18F-Phe into tumour tissue is mainly related to the carrier-mediated active transport. It is concluded that PET with18F-Phe is of clinical value for tumour detection rather than assessment of tumour malignancy.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1619-7089
    Keywords: Neuroleptic binding sites ; 3-N-[11C]methylspiperone ; Specific labeling in vivo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In vivo binding of 3-N-[11C]methylspiperone ([11C]NMSP) was saturable in the rat forebrain, but not in the cerebellum. Nonspecific binding was almost equivalent in all brain regions except for the white matter. [11C]NMSP binding was localized to receptor-rich fractions when low doses were administered (less than 20 nmol/kg body weight). The striatum-to-cerebellum ratio was a function of time after injection and administered dose. This radio remained constant in low doses of under 30 nmol/kg. The radioactivity curve of the cerebellum in a control positron-emission tomographic study almost equaled that of the striatum in the dog pretreated with spiperone (2 mg). This indicates that the amount of binding in the cerebellum might be considered a nonspecific binding and unbound pool. The data obtained by the pretreatment study was different from that of displacement, which suggested that displaceable [11C]NMSP in the specific binding sites of the striatum was not completely cleared from the brain tissue by a large amount of unlabeled spiperone.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1619-7089
    Keywords: Myocardium ; Glucose metabolism ; 18F-2-fluoro-2-deoxy-d-glucose ; Fasting time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The myocardial uptake of 18F-FDG was investigated under various conditions, and compared with brain and tumor uptake as a function of blood glucose level. The uptake by the heart of normal feeding rats was rapid and remained essentially unchanged up to 2 h after 18F-FDG injection, approximately 3%–4% dose/g tissue. On the other hand, the myocardial uptake of fasted rats was significantly lower than that of control rats throughout the course of the study, and it was about 0.3%–0.4% dose/g tissue. Myocardial uptake of 18F-FDG was relatively constant at glucose levels under about 120 mg/100 ml and increased steeply at higher blood glucose levels. In contrast, brain uptake decreased linearly with increasing levels of blood glucose, revealing a strong negative correlation between brain uptake of 18F-FDG and blood glucose levels. The tumor uptake pattern remained relatively unchanged, irrespective of blood glucose levels. It was revealed that the glucose demands of brain, heart, and tumor were entirely different. After a glucose load, the myocardial uptake of fasted rats increased only slightly from 0.4% to 0.6% dose/g tissue, in spite of transitional hyperglycemia. In contrast, insulin caused myocardial uptake to increase extraordinarily, although it caused a decrease in blood glucose levels.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1619-7089
    Keywords: 11C-methionine ; Positron emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The metabolites of L-[methyl-11C]methionine in the plasma of 8 patients with tumor were measured for 60 min after injection. In the plasma, after a rapid clearance, the total radioactivity remained constant, and protein-bound radioactivity increased rapidly. Non protein metabolites detected by HPLC as at least two components besides methionine, increased with time. Significant individual variations for the metabolism were observed. AT 60 min after injection, 36.5% (range: 16%–72%) and 45.3% (range: 13%–74%) of the 11C was measured as methionine and labeled proteins, respectively.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-6792
    Keywords: Topographic EEG map ; CBF ; PET ; Combined display
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To evaluate complicated changes in the EEG and cerebral blood flow (CBF) in cerebral infarction, EEG was recorded under various blood pressure levels, during CBF measurement with positron emission tomography, in patients with chronic cerebral infarction. Newly developed display methods which combine topographic EEG and its significance probability mapping with CBF, clearly provided objective measures of changes in EEG parameters and CBF, during induced hypo- and hypertension.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-7373
    Keywords: 18F-fluorodeoxyglucose ; kinetic analysis ; oligodendroglioma ; positron emission tomography ; tumor recurrence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To accurately characterize the pathophysiology and proliferating activity of oligodendrogliomas, we studied cerebral blood flow and metabolism using positron emission tomography (PET) in five patients with this tumor. Regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), oxygen extraction fraction (rOEF), and cerebral metabolic rates of oxygen (rCMRO2) and of glucose (rCMRGl) were quantitatively measured in tumor lesions and the contralateral gray matter. rCMRGl was analyzed based on both kinetic and autoradiographic methods. Tumor rCBF and rCBV were lower than in the contralateral gray matter in all preoperatively examined patients. Oxygen metabolism, determined by rCMRO2 and rOEF, was consistently reduced in the tumor (rCMRO2, P〈0.05 vs. gray matter, determined by the Student's t-test). Tumor rCMRGl was significantly lower than the gray matter rCMRGl in both kinetic (P〈0.01) and autoradiographic (P〈0.05) analyses. Kinetic tumor rCMRGl varied between 1.22 and 4.13 mg/100 ml/min, but was lower than the gray matter value in all patients. Autoradiographic tumor rCMRGl, which ranged from 1.02 to 5.79 mg/100 ml/min, was also reduced in all tumors but one; the remaining tumor, which had a relatively high value of autoradiographic rCMRGl (comparable to gray matter rCMRGl), infiltrated the contralateral hemisphere through the corpus callosum, and was characterized by high cellular density. In one patient who suffered from tumor recurrence 8 years and 10 months after initial treatment, phosphorylation constant (K3) and kinetic rCMRGl of the recurring tumor were higher than those of the original tumor. No other tumors have regrown or recurred during the postoperative follow-up periods, which ranged from 22 to 130 months (median=101 months). Circulation and metabolism measured by PET provide in vivo biological characteristics, including proliferating activity, in oligodendrogliomas.
    Type of Medium: Electronic Resource
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