Biomedical subjects

K Någren

Publications and source records attributed to K Någren.

At least 19 recordsLinked to original sources

PubMed2001

Decreased binding of [11C]flumazenil in Angelman syndrome patients with GABA(A) receptor beta3 subunit deletions.

We used positron emission tomography (PET) to study brain [11C]flumazenil (FMZ) binding in four Angelman syndrome (AS) patients. Patients 1 to 3 had a maternal deletion of 15q11-q13 leading to the loss of beta3 subunit of gamma-aminobutyric acidA/benzodiazepine (GABA(A)/BZ) receptor, whereas Patient 4 had a mutation in the ubiquitin protein ligase (UBE3A) saving the beta3 subunit gene. [11C]FMZ binding potential in the frontal, parietal, hippocampal, and cerebellar regions was significantly lower in Patients 1 to 3 than in Patient 4. We propose that the 15q11-q13 deletion leads to a reduced number of GABA(A)/BZ receptors, which could partly explain the neurological deficits of the AS patients.

Adolescent↗

PubMed2001

Myocardial fatty acid oxidation in patients with impaired glucose tolerance.

AIMS/HYPOTHESIS: Fatty acids are an important source of energy in the myocardium. Abnormal myocardial fatty acid metabolism could contribute to the deterioration of cardiac function frequently observed in patients with Type II (non-insulin-dependent) diabetes mellitus. In our previous study, myocardial total uptake of non-esterified fatty acid (NEFA) was measured in patients with impaired glucose tolerance and found to be normal. This study aimed to investigate the subsequent metabolic steps and beta-oxidation of NEFA. METHODS: A total of 6 men with impaired fasting glucose (age 50 +/- 2 years, BMI 29 +/- 1 kg/m2, means +/- SEM) and 6 healthy men (50 +/- 1 years, 25 +/- 1 kg/ m2) were studied in the fasting state. Myocardial blood flow was measured with [15O]H2O and positron emission tomography and myocardial NEFA metabolism with [11C]palmitic acid. RESULTS: Myocardial blood flow was normal and not different between the impaired glucose tolerance and the control group (78 +/- 6 vs 73 +/- 13 ml/100 g/ min, NS). The [11C]palmitic acid uptake indices were similar between the groups (10.4 +/- 0.5 vs 11.2 +/- 0.8 ml/100 g/min, respectively, NS). The clearance of [11C]-palmitate from the myocardium, an index of NEFA beta-oxidation, was similar between the groups (half-times of activity 17.6 +/- 1.6 vs 19.5 +/- 2.3 min, respectively, NS) CONCLUSION/INTERPRETATION: The results indicate that myocardial NEFA uptake and beta-oxidation are not altered in patients with IGT. Thus, it is not likely that altered NEFA metabolism contributes to the deterioration of the cardiac function in patients with IGT or Type II diabetes.

Blood Glucose↗

PubMed2001

Use of [11C]acetate and [15O]O2 PET for the assessment of myocardial oxygen utilization in patients with chronic myocardial infarction.

Carbon-11 acetate positron emission tomography (PET) has been widely used to assess regional oxidative metabolism of the heart. However, the accuracy of [11C]acetate PET in assessing oxidative metabolism in infarcted myocardium remains controversial. Thirteen patients with stable coronary artery disease and old myocardial infarction were studied. The 15O-based PET studies yielded regional blood flow (rMBF, ml/min/g) and oxygen consumption (rMMRO2, ml/min/g), which was compared with the myocardial clearance rate constant (kmono) of [11C]acetate in segments with rMBF > or = 75% (group A), 50%-74% (group B) or < 50% (group C) of the normal reference segment. Mean MBF was 0.96 +/- 0.08 ml/g/min in group A, 0.67 +/- 0.06 ml/g/min in group B and 0.42 +/- 0.07 ml/g/min in group C segments. The segmental rMMRO2 correlated linearly with kmono (r = 0.89, P < 0.001, y = 0.61x + 0.026). The kmono/rMMRO2 ratio was comparable in the group A and B segments (0.99 +/- 0.19 vs 1.07 +/- 0.21, P = NS). However, the ratio was significantly higher in the group C segments (1.28 +/- 0.35, P = 0.037). It is concluded that kmono of [11C]acetate correlates linearly with rMMRO2 determined by [15O]O2 inhalation. However, kmono appears to yield higher rMMRO2 estimates than the [15O]O2 method in low-flow areas.

Acetates↗

PubMed2001

Reduced myocardial carbon-11 hydroxyephedrine retention is associated with poor prognosis in chronic heart failure.

Abnormalities of the autonomic nervous system are known to be of prognostic significance in chronic heart failure (CHF). The prognostic value of positron emission tomography (PET) imaging of cardiac autonomic innervation in CHF has not been explored previously. We retrospectively studied the survival data of 46 NYHA class II-III CHF patients (mean LVEF 35% +/- 8%) who had undergone carbon-11 hydroxyephedrine (11C-HED) studies at the Turku PET Centre between August 1992 and March 1996. The origin of CHF was dilated cardiomyopathy in 13 of the 46 patients and coronary artery disease with at least one prior myocardial infarction in the remaining 33. Data on causes of death and heart transplantation were collected, and the statistically significant predictors of prognosis were analysed using Cox's proportional hazards regression. During the mean follow-up period of 55 +/- 19 months, 11 deaths occurred and two patients underwent heart transplantation successfully. Eleven end-points were classified as cardiac (nine sudden cardiac deaths and two deaths due to progressive heart failure) and two as non-cardiac. When divided into two groups based on the median of 11C-HED retention (mean 0.184 +/- 0.061, median 0.183), eight end-points (death or cardiac transplantation) were reached in the group with 11C-HED retention below the median and three in the group with 11C-HED retention above the median (P < 0.02). In proportional hazards regression analysis, only peak oxygen uptake (peak VO2), left ventricular end-diastolic volume and HED retention were found to be statistically significant. It is concluded that 11C-HED PET provides independent prognostic information in patients with CHF.

Aged↗

PubMed2001

Synthesis of high-specific-radioactivity 4- and 6-[18F]fluorometaraminol-PET tracers for the adrenergic nervous system of the heart.

Fluorine-18- (t(1/2) 109.8 min) and carbon-11 (t(1/2) 20.4 min)-labeled norepinephrine analogues have been found previously to be useful positron-emission-tomography (PET) radioligands to map adrenergic nerve terminals of the heart. Metaraminol ((1R,2S)-2-amino-1-(3-hydroxyphenyl)-1-propanol) is a metabolically stable structural analogue of norepinephrine and possesses high affinity towards the norepinephrine transporter and the vesicular monoamine transporter. This paper presents the radiosynthesis of new positron-emission-tomography halogeno analogues of metaraminol labeled with high specific radioactivity. Firstly, fluorine-18-labeled 4-fluorometaraminol (4-[18F]FMR or (1R,2S)-2-amino-1-(4-[18F]fluoro-3-hydroxyphenyl)-1-propanol) and its three other stereoisomers were prepared based on the following key steps: (a) condensation of the corresponding no-carrier-added labeled fluorobenzaldehyde with nitroethane, and (b) HPLC (C18 and chiral) resolution of the diastereomeric product mixture into the four individual enantiomers. Secondly, the corresponding 6-fluoro analogues, fluorine-18-labeled 6-fluorometaraminol (6-[18F]FMR or (1R,2S)-2-amino-1-(2-[18F]fluoro-5-hydroxyphenyl)-1-propanol) and its three other enantiomers, were prepared in an analogous way. Typically, 0.48-0.55 GBq of 4-[18F]FMR and 0.14-0.15 GBq of 6-[18F]FMR could be obtained after 120-160 min total synthesis time, with a specific radioactivity of 56-106 GBq/micromol. Furthermore, the synthesis of racemic 4-fluorometaraminol and 6-fluorometaraminol as reference compounds was performed. as well as independent chiral syntheses of the optically active (1R,2S) enantiomers. For the chiral syntheses, the key step was an electrophilic fluorination with acetyl hypofluorite of (1R,2S)-configurated organometallic derivatives of metaraminol. Tissue distribution studies in rats suggested that both 4-[18F]FMR and 6-[18F]FMR display similar affinity towards the presynaptic adrenergic nerve terminal in the heart. From a practical point of view, 4-[18F]FMR appeared to be the more attractive candidate for future PET investigations, due to higher radiochemical yields.

Animals↗

PubMed2001

Sex differences in extrastriatal dopamine d(2)-like receptors in the human brain.

OBJECTIVE: The study examined gender differences in extrastriatal dopamine D2-like receptor levels in the human brain in vivo. METHOD: [(11)C]FLB 457, a high-affinity radioligand for extrastriatal D(2)-like receptors, and a three-dimensional positron emission tomography system were used to measure D(2)-like receptor binding potentials in frontal cortex, temporal cortex, and thalamus in 12 healthy men and 12 healthy women. RESULTS: Women had higher D(2)-like receptor binding potentials than men in the three brain regions studied, and the difference in the frontal cortex was statistically significant. In a more detailed regional analysis, the difference between the sexes was most pronounced for the left and right anterior cingulate cortex. CONCLUSIONS: This study provides in vivo evidence for a gender difference in dopamine D(2)-like receptor levels, which could be reflected in gender-associated differences in clinical disorders linked to the dopamine system.

Adult↗

PubMed2000

[11 C]Flumazenil binding in the medial temporal lobe in patients with temporal lobe epilepsy: correlation with hippocampal MR volumetry, T2 relaxometry, and neuropathology.

OBJECTIVE: To detect reduced [11C]flumazenil in patients with temporal lobe epilepsy (TLE) and to relate binding to histopathology. METHODS: The authors studied 16 patients who underwent epilepsy surgery because of drug-resistant TLE using [11C]flumazenil PET and quantitative MRI. In 12 patients, resected hippocampus was available for histologic analysis. [11C]Flumazenil binding potential (fitted BP) was assessed with the simplified reference tissue model. RESULTS: [11C]Flumazenil fitted BP in the medial temporal lobe was reduced in all patients with abnormal hippocampal volumetry or T2 relaxometry on MRI. Fitted BP was also reduced in 46% of the patients with hippocampal volume within the normal range and in 38% of patients with less than 2 SD T2 prolongation. In all MRI-negative/PET-positive patients, the histologic analysis verified hippocampal damage. Also, [11C]flumazenil fitted BP correlated with the severity of reduced hippocampal volume, T2 prolongation, and histologically assessed neuronal loss and astrogliosis. CONCLUSION: [11C]Flumazenil PET provides a useful tool for investigating the hippocampal damage in vivo even in patients with no remarkable hippocampal abnormalities on quantitative MRI.

Adolescent↗

PubMed2000

Extrastriatal dopamine D2 and D3 receptors in early and advanced Parkinson's disease.

OBJECTIVE: To investigate whether dopamine D2 and D3 receptor subtypes (D2/3Rs) outside the caudate-putamen are affected in PD. BACKGROUND: Alterations in striatal D2-like dopamine receptors in PD have been extensively demonstrated using PET, but there are no studies focusing on extrastriatal D2/3Rs. METHODS: Fourteen unmedicated patients with idiopathic early PD with predominantly left-sided symptoms, 14 levodopa-medicated patients with advanced PD, and 20 normal age-matched controls were examined using PET. PET scanning was performed with a novel high-affinity D2/3R radioligand ([11C]FLB 457) and a PET scanner in three-dimensional mode. RESULTS: In advanced PD, the binding potential of [11C]FLB 457 in the dorsolateral prefrontal cortex was decreased by 40% (p < 0.01), in the anterior cingulate cortex by 20% (p < 0.01), and in the medial thalamus by 17% (p < 0.05) compared with healthy controls. In early PD, the extrastriatal [11C]FLB 457 binding potentials were not significantly different compared with the control group. However, the binding potential in the anterior cingulate cortex (29%; p < 0. 05) was higher in early PD compared with advanced PD. CONCLUSIONS: These results imply that the D2/3 receptor subtypes outside the striatum are affected in advanced PD but not in the early stages of the disease, and that this receptor decline is present in the anterior cingulate cortex, the dorsolateral prefrontal cortex, and the thalamus.

Brain↗

PubMed2000

Measurement of extrastriatal D2-like receptor binding with [11C]FLB 457--a test-retest analysis.

[11C]FLB 457 is a radioligand for positron emission tomography (PET) that possesses high affinity to D2/D3 receptors. It has been suggested to be useful for quantification of low-density dopamine D2 receptor populations, e.g. in cortical and limbic brain areas. We explored the reproducibility of five methods for measuring extrastriatal D2-like receptor binding potential with [11C]FLB 457. Seven healthy male volunteers were examined twice with [11C]FLB 457 (high specific radioactivity) on the same day, at least 3 h apart. Four brain areas, frontal cortex, nucleus thalamus, temporal cortex and cerebellar cortex, were examined. Binding potentials (BPs) were derived from (1) a target to cerebellum distribution volume ratio, (2/3) two reversible reference tissue compartment models and (4) a transient equilibrium approach. For comparison, BP values were also calculated with the standard three-compartment kinetic model that does not assume a receptor-free reference region. The use of the standard three-compartment model did not result in reproducible BP estimates. The distribution volume (DV) ratio, reference tissue compartment models and the transient equilibrium method all had good to excellent intraclass correlation coefficients (ICCs) in the studied brain areas ranging from 0.56 to 0.93. Absolute variability was also relatively low, ranging from 5.3% to 10.4%. There were no marked differences in the ICC or absolute and relative variability between the four methods based on a reference tissue (cerebellum). In addition, we did not observe systematic differences in the BP between the first and the second scan. These data indicate that the reproducibility of the DV ratio, reference tissue models and the transient equilibrium method is good or excellent. However, each of these methods includes assumptions affecting their validity. Thus, the choice of method will be critically dependent on the purpose of the study.

Adult↗

PubMed2000

Quantification of [Carbonyl-(11)C]WAY-100635 binding: considerations on the cerebellum.

The specific binding of [carbonyl-(11)C]WAY-100635 to 5-hydroxytryptamine(1A) receptors was quantitated using different kinetic models. Ten healthy subjects were studied using a GE Advance PET scanner. We suggest that tissue heterogeneity explains part of the nonspecific binding seen in cerebellum, which leads to an underestimation of binding potential with reference tissue methods. The nonlinear three-compartmental model with metabolite-corrected plasma input provides accurate estimates of receptor binding because of the favorable kinetics of tracer in the brain and circulation.

Adult↗

PubMed2000

Carbon-11 pb-12: an attempt to visualize the dopamine d(4) receptor in the primate brain with positron emission tomography.

The dopamine D(4) receptor (D(4)R) is expressed in low density in various extrastriatal brain regions. This receptor subtype is discussed in relation to the pathophysiology and treatment of schizophrenia but no selective positron emission tomography (PET) ligand is available to date to study the distribution in vivo. The arylpiperazine derivative N-[2-[4-(4-chlorophenyl)piperazin-1-yl]ethyl]-3-methoxybenzamide (PB-12) is a novel, high-affinity ( K(i)=0.040 nM) and selective D(4)R ligand. We radiolabeled PB-12 with carbon-11 (t(1/2) 20.4 min) by O-methylation of the corresponding desmethyl analogue N-[2-[4-(4-chlorophenyl)piperazin-1-yl]ethyl]-3-hydroxybenzamide (LM-190) with [(11)C]methyl triflate. Derivative LM-190 was prepared by condensing 3-hydroxybenzoic acid with the appropriate amine. For the radiolabeling, the incorporation yield was >90% and the total synthesis time including high performance liquid chromatography (HPLC) purification was about 35 min. The specific radioactivity of [(11)C]PB-12 at time of injection was 67-118 GBq x micromol(-1). PET studies in a cynomolgus monkey showed a high uptake and widespread distribution of radioactivity in the brain, including the neocortex and thalamus. About 40% of total radioactivity in plasma represented unchanged radioligand at 60 min after injection as determined by HPLC. Pretreatment with the D(4)R ligand 3-[[4-(4-chlorophenyl)piperazin-1-yl]methyl]-1H-pyrollo[2,3-b]pyridine (L-745,870) prior to radioligand injection failed to demonstrate receptor-specific binding in the monkey brain. Furthermore, the brain radioactivity distribution was left unaffected by pretreating with unlabeled PB-12. This failure to detect a D(4)R-specific signal may be related to a very low density of the D(4)R in primate brain, insufficient binding affinity of the radioligand, and a high background of nonspecific binding. It can be concluded from these findings that [(11)C]PB-12 is not suitable to visualize the D(4)R in the primate brain with PET.

Animals↗

PubMed2000

Myocardial efficiency during levosimendan infusion in congestive heart failure.

AIMS: Levosimendan, a novel calcium-dependent calcium sensitizer of the myocardial contractile proteins, also enhances diastolic relaxation and induces peripheral vasodilation by opening potassium channels. To assess the combined energetical effects of levosimendan infusion in vivo, we performed positron emission tomography in patients with decompensated chronic heart failure. METHODS AND RESULTS: Eight hospitalized patients with New York Heart Association functional class III or IV heart failure received levosimendan or placebo intravenously in a randomized double-blind cross-over study. During steady-state, dynamic positron emission tomography with [11C]acetate was used to assess myocardial oxygen consumption and [15O]H2O to measure myocardial blood flow. Cardiac performance and dimensions were assessed by pulmonary artery catheterization and echocardiography. Compared with healthy volunteers, myocardial oxygen consumption during placebo was elevated in the right ventricle but comparable in the left ventricle. During administration of levosimendan, cardiac output increased by 32% (P = .002) mainly because of higher stroke volume. Coronary, pulmonary, and systemic vascular resistance values were significantly reduced. Mean myocardial blood flow increased from 0.76 to 1.02 mL/min/g (P = .033). Levosimendan was neutral on myocardial oxygen consumption and left ventricular efficiency, but it improved right ventricular mechanical efficiency by 24% (P = .012). CONCLUSIONS: Levosimendan has an energetically favorable short-term profile in the treatment of congestive heart failure. It enhances cardiac output without oxygen wasting, particularly by improving efficiency in the right ventricle.

Cardiotonic Agents↗

PubMed2000

Upregulation of putaminal dopamine D2 receptors in early Parkinson's disease: a comparative PET study with [11C] raclopride and [11C]N-methylspiperone.

UNLABELLED: Dopamine D2 receptor function was assessed in a PET study with 2 dopamine D2 receptor PET ligands, [11C]raclopride (RAC) and [11C]N-methylspiperone (NMSP), in early Parkinson's disease. METHODS: Seven patients with early Parkinson's disease and 5 healthy volunteers were studied. Each underwent PET both with reversible [11C]RAC and with irreversible [11C]NMSP. RESULTS: Upregulation of dopamine D2 receptors in the putamen contralateral to the predominant symptoms of Parkinson's disease was confirmed using both [11C]RAC and [11C]NMSP. Uptake of [11C]RAC in the contralateral putamen was 105% of uptake in the opposite putamen (P = 0.020). For [11C]NMSP, uptake in the contralateral putamen was 105% of uptake in the ipsilateral putamen (P = 0.011). No significant differences between Parkinson's disease patients and healthy volunteers were detected in any of the studied brain regions using either [11C]RAC or [11C]NMSP. No significant differences between [11C]RAC and [11C]NMSP uptake were detected in the striatum, whereas in the extrastriatal regions, [11C]NMSP showed significantly higher uptake than [11C]RAC both in healthy volunteers and in Parkinson's disease patients. CONCLUSION: This study confirms an increase in dopamine D2 receptors in the putamen contralateral to the predominant symptoms, compared with the ipsilateral putamen, in early Parkinson's disease. This increase was seen both with reversible ligand [11C]RAC and with irreversible ligand [11C]NMSP and thus does not seem a consequence of depleted endogenous dopamine.

Carbon Radioisotopes↗

PubMed1999

Cardiac positron emission tomography imaging with [11C]hydroxyephedrine, a specific tracer for sympathetic nerve endings, and its functional correlates in congestive heart failure.

The integrative mechanisms of autonomic dysfunction in congestive heart failure (CHF) remain poorly understood. We sought to study cardiac retention of [11C]hydroxyephedrine (HED), a specific tracer for sympathetic presynaptic innervation, and its functional correlates in CHF. Thirty patients with mild to moderate heart failure underwent resting cardiac HED positron emission tomography imaging, spectrum analysis testing of systolic pressure and heart rate variability in the resting supine and 70 degrees head-up tilt positions, and testing of baroreflex sensitivity. Compared with control subjects, global myocardial HED retention index was reduced by 30% (p <0.01) in patients with CHF. The HED retention index did not correlate significantly with heart rate variability. However, it correlated with baroreflex sensitivity at rest (r = 0.43, p = 0.05) and with systolic pressure low-frequency (0.03 to 0.15 Hz) variability at head-up tilt (r = 0.76, p <0.01), as well as with low-frequency systolic pressure variability response from baseline to tilt (r = 0.75, p <0.01). We conclude that cardiac HED retention is reduced in patients with CHF. This correlates with blunted vascular sympathetic effector responses during posture-induced reflex activation and baroreflex control of heart rate, suggesting an interdependence between cardiac presynaptic innervation abnormalities and neural mechanisms important to blood pressure maintenance in CHF.

Blood Pressure↗

PubMed1999

Brain 5-HT2A receptor occupancy of deramciclane in humans after a single oral administration--a positron emission tomography study.

RATIONALE: Deramciclane fumarate is a new 5-HT2A and 5-HT2C receptor antagonist with putative anxiolytic effects. In the present study the binding of deramciclane to serotonin 5-HT2A receptors in frontal cortex of healthy male volunteers was studied using [11C]-N-methyl spiperone ([11C]-NMSP) and positron emission tomography. METHODS: The receptor occupancy percentage was assessed by the means of inhibition of [11C]-NMSP from the 5-HT2A receptors in the frontal cortex. Single oral doses of 20, 50 and 150 mg deramciclane were given to three subjects at each dose level (total n = 9). The receptor occupancy was measured before deramciclane and at 3 and 6 h post-dosing except at the 20 mg dose level where only the 3-h measurement was done. The occupancy percentage was calculated with the ratio method using cerebellum as a reference area. RESULTS: Deramciclane inhibited [11C]-NMSP binding dose and concentration dependently. However, deramasciclane inhibited maximally only 52% of the [11C]-NMSP binding in the frontal cortex, indicating a non-5-HT2A receptor binding component of this radioligand in frontal cortex. On average, specific [11C]-NMSP binding cerebellum ratios below 0.355 were not possible to achieve in this population. The 52% inhibition was regarded to represent near 100% 5-HT2A receptor occupancy. The 50 and 90% receptor occupancies were reached at deramciclane plasma concentrations of 21 ng/ml and 70 ng/ml, respectively. CONCLUSIONS: Deramciclane penetrates the blood-brain barrier in humans. Deramciclane binds to the 5-HT2A receptors in the frontal cortex in a saturable manner in vivo. Consequently, the increase in deramciclane concentration in plasma above 70 ng/ml will not result in major increase in the 5-HT2A receptor occupancy in the brain.

Administration, Oral↗

PubMed1999

Measurement of striatal D2 dopamine receptor density and affinity with [11C]-raclopride in vivo: a test-retest analysis.

Subacute and long-term stability of measurements of D2 dopamine receptor density (Bmax), affinity (Kd) was studied with positron emission tomography in eight healthy male volunteers. [11C]-Raclopride and the transient equilibrium method were used to measure D2 receptor characteristics. The interval between measurements (scan pairs) was 3 to 7 weeks (subacute) for four subjects and 6 to 11 months (long-term) for four subjects. A test-retest analysis of quantitative measurements of D2 receptor Bmax and Kd was compared with that done on binding potential (BP, Bmax/Kd) measures. In addition, the effect of error in defining the transient equilibrium time (tmax) in the parameter estimation procedure was explored with simulations. The subacute test-retest indicates good reproducibility of D2 receptor density, affinity, and BP ratio measurements with intraclass correlation coefficients of 0.90, 0.96, and 0.86, respectively. The variability of the measurements after 6 to 11 months was slightly higher than that seen in a subacute testing for Kd and more clearly so for binding potential and Bmax. The absolute variability in Bmax (14.5%) measurements was consistently higher than that of Kd (8.4%) or BP (7.9%) both in subacute and long-term measurements. Simulations indicated that the Bmax and Kd estimation procedure is more sensitive to error in the tmax than that for the BP. The results indicate a good overall stability of the equilibrium method with [11C]raclopride for measuring dopamine D2 receptor binding characteristics in the striatum. The BP approach is more stable than Kd and especially Bmax measurements. Error in defining the tmax in particular in the low specific radioactivity scan may be one source of greater variability in Bmax versus BP. However, a higher intraindividual variability in measurements of the D2 receptor Bmax also may include a component of continuous regulation of this parameter over time. These methodologic aspects should be considered in the design and interpretation of longitudinal studies on D2 dopamine receptor characteristics with [11C]-raclopride.

Adult↗

PubMed1999

The dopamine D2 receptor 5'-flanking variant, -141C Ins/Del, is not associated with reduced dopamine D2 receptor density in vivo.

The Del allele of the -141C (Ins/Del) polymorphism located in the immediate 5'-flanking region of the human dopamine D2 receptor gene has been reported to be associated with reduced promoter activity in vitro. However, genetic association studies of the -141C (Ins/Del) polymorphism with schizophrenia and alcoholism have yielded conflicting results. In this report, we explored the effect of the Del allele on the D2 receptor binding characteristics in vivo in healthy volunteers using positron emission tomography and D2 receptor antagonist, [11C]raclopride. No difference in D2 receptor density was observed between the Del allele carriers compared to the individuals with the Ins/Ins genotype, indicating that the genetic variation at the -141C (Ins/Del) site does not affect D2 receptor expression level in vivo.

Adult↗

PubMed1998

Use of carbon-11 methionine positron emission tomography to assess malignancy grade and predict survival in patients with lymphomas.

The aim of this study was to investigate whether uptake of carbon-11 methionine (MET) is associated with histological grade of malignancy and survival in patients with newly diagnosed or recurrent lymphoma. Thirty-two patients with histologically confirmed lymphoma participated in the study. Twenty-six (81%) were studied before any therapy and six before treatment for recurrent disease. Twenty-eight patients had non-Hodgkin's lymphoma and four had Hodgkin's disease. An ECAT 931/08-12 positron emission tomography (PET) scanner was used for PET imaging. After the transmission scan, a median dose of 293 MBq of MET was injected intravenously and dynamic images were acquired for 40 min. The uptake of MET in tumour was measured as the standardized uptake value (SUV) and influx constant (Ki). The SUV formula was also adjusted to the predicted value of lean body mass (SUVlean) and body surface area (SUVBSA). The PET results were correlated with the clinical follow-up data. The median SUV in 32 malignant lesions was 6.6 (range, 1.9-12.4) and the median Ki was 0. 116 min-1 (range, 0.025-0.201, n=23). The median SUV was 7.0 (range, 5.4-12.4, n=9) in high, 6.2 (range, 1.9-10.4, n=11) in intermediate and 5.7 (range, 3.8-8.3, n=8) in low grade lymphomas. One intermediate grade lymphoma of the skin was visually negative (SUV 1. 9). In Hodgkin's disease the median SUV was 7.0 (range, 3.2-7.9, n=4). The median Ki value was 0.162 min-1 (range, 0.147-0.197, n=7) in high, 0.099 (range, 0.025-0.152, n=10) in intermediate, and 0.078 (range, 0.056-0.152, n=4) in low grade lymphomas and 0.149 (range, 0. 096-0.201, n=2) in Hodgkin's disease. The difference between high and other grade non-Hodgkin's lymphomas was significant when using Ki (P<0.001), but not with SUV, SUVlean or SUVBSA. The final outcome of the patients was not related to MET uptake. Lymphomas with a high Ki value tended to have a high S-phase fraction (r2=0.46, P=0.043). It is concluded that MET PET is highly sensitive for the detection of untreated and recurrent lymphomas. Differentation of high grade lymphomas from lower malignancy grades seems to be possible if graphical analysis is applied to calculate Ki for MET. However, prediction of survival is not possible with MET PET.

Adolescent↗