Propofol anesthesia does not alter regional rates of cerebral protein synthesis measured with L-[1-(11)C]leucine and PET in healthy male subjects.

We report regional rates of cerebral protein synthesis (rCPS) in 10 healthy young males, each studied under two conditions: awake and anesthetized with propofol. We used the quantitative L-[1-(11)C]leucine positron emission tomography (PET) method to measure rCPS. The method accounts for the fraction (lambda) of unlabeled leucine in the precursor pool for protein synthesis that is derived from arterial plasma; the remainder comes from proteolysis of tissue proteins.

Regional rates of cerebral protein synthesis measured with L-[1-11C]leucine and PET in conscious, young adult men: normal values, variability, and reproducibility.

We report regional rates of cerebral protein synthesis (rCPS) measured with the fully quantitative L-[1-(11)C]leucine positron emission tomography (PET) method. The method accounts for the fraction (lambda) of unlabeled amino acids in the precursor pool for protein synthesis derived from arterial plasma; the remainder (1-lambda) comes from tissue proteolysis. We determined rCPS and lambda in 18 regions and whole brain in 10 healthy men (21 to 24 years).

Use of acute hyperphenylalaninemia in rhesus monkeys to examine sensitivity and stability of the L-[1-11C]leucine method for measurement of regional rates of cerebral protein synthesis with PET.

We have previously shown by direct comparison with autoradiographic and biochemical measurements that the L-[1-(11)C]leucine positron emission tomography method provides accurate determinations of regional rates of cerebral protein synthesis (rCPS) and the fraction (lambda) of unlabeled leucine in the precursor pool for protein synthesis derived from arterial plasma. In this study, we examine sensitivity of the method to detect changes in lambda and stability of the method to measure rCPS in the face of these changes. We studied four isoflurane-anesthetized monkeys dynamically scanned with the high resolution research tomograph under control and mild hyperphenylalaninemic conditions.

An automated one-step one-pot [(18)F]FCWAY synthesis: development and minimization of chemical impurities.

[(18)F]FCWAY (N-{2-[4-(2-methoxyphenyl)piperazino]}-N-(2-pyridinyl)trans-4-fluorocyclohexanecarboxamide) has been prepared routinely as a serotonin 5-HT(1A) receptor ligand for clinical human studies. We have developed an automated one-step radiosynthesis using a modified Nuclear Interface C-11 Methylation System. The chemical synthesis of an appropriate methanesulfonate precursor for single-step nucleophilic substitution with [(18)F]fluoride ion and the adaptation of radiochemical synthesis to an automated production module were accomplished.

Imaging signal transduction via arachidonic acid in the human brain during visual stimulation, by means of positron emission tomography.

Background: Arachidonic acid (AA, 20:4n-6), an important second messenger, is released from membrane phospholipid following receptor mediated activation of phospholipase A(2) (PLA(2)). This signaling process can be imaged in brain as a regional brain AA incorporation coefficient K*.

Hypothesis: K* will be increased in brain visual areas of subjects submitted to visual stimulation.

Measurement of regional rates of cerebral protein synthesis with L-[1-11C]leucine and PET with correction for recycling of tissue amino acids: II. Validation in rhesus monkeys.

The confounding effect of recycling of amino acids derived from tissue protein breakdown into the precursor pool for protein synthesis has been an obstacle to adapting in vivo methods for determination of regional rates of cerebral protein synthesis (rCPS) to positron emission tomography (PET). We used a kinetic modeling approach to estimate lambda, the fraction of the precursor pool for protein synthesis derived from arterial plasma, and to measure rCPS in three anesthetized adult monkeys dynamically scanned after a bolus injection of L-[1-11C]leucine. In the same animals, lambda was directly measured in a steady-state terminal experiment, and values showed excellent agreement with those estimated in the PET studies.

Purification of the precursor for the automated radiosynthesis of [18F]FCWAY by counter-current chromatography.

Radiolabeled FCWAY (N-(2-[4-(2-methoxyphenyl)piperazino])-N-(2-pyridinyl) trans-4-fluorocyclohexanecarboxamide) was prepared for human positron emission tomography (PET) studies by a simple one-step radiosynthesis. The LC-MS analysis of the products indicated that it contained impurities which may interfere with FCWAY uptake of 5-HT1A receptors and that these impurities were derived from an impurity originally present in the precursor preparation. Since preparative HPLC failed to resolve one of the impurities from the precursor, preparative-scale high-speed counter-current chromatography (HSCCC) was used for purification of this FCWAY precursor.

Routine quality control of recycled target [18O]water by capillary electrophoresis and gas chromatography.

Recycling of [(18)O]water for [(18)F]fluoride production can be accomplished with reliable results. We have developed sensitive, robust, and rapid analyses of impurities in [(18)O]water. Anions were quantitated by capillary electrophoresis and organic residuals were quantitated by gas chromatography using methods with excellent reproducibility and linearity.

The automated radiosynthesis of [18F]FP-TZTP.

[(18)F]FP-TZTP (3-(3-(3-[(18)F]fluoropropylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine) is a muscarinic ligand that displays in vivo selectivity for the M2 subtype. We have developed a one-step radiosynthesis of [(18)F]FP-TZTP that can be conducted with an automated synthesis unit. A number of hardware and software modifications to a Nuclear Interface C-11 Methylation System provided the equipment for the automated radiosynthesis.

Brain incorporation of [11C]arachidonic acid in young healthy humans measured with positron emission tomography.

Arachidonic acid (AA) is an important second messenger involved in signal transduction mediated by phospholipase A2. The goal of this study was to establish an in vivo quantitative method to examine the role of AA in this signaling process in the human brain. A simple irreversible uptake model was derived from rat studies and modified for positron emission tomography (PET) to quantify the incorporation rate K* of [11C]AA into brain.

Quantification of Kryptofix 2.2.2 in 2-[(18)F]FDG and other radiopharmaceuticals by LC/MS/MS.

A high-performance liquid chromatography-tandem mass spectrometric method (LC/MS/MS) was developed and validated for the quantitative analysis of Kryptofix (K-222) in the radiopharmaceuticals of 2-deoxy-2-[(18)F] fluoro-D-glucose (2-[(18)F]FDG) and 3-(3-((3-fluoropropyl)thio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (FPTZTP). With an internal standard, the limit of quantitation for K-222 was 1.0 ng/ml.

Analysis of residual solvents in 2-[(18)F]FDG by GC.

A gas chromatography method has been developed for the measurement of the residual acetone, ethanol and acetonitrile in 2-deoxy-2-[(18)F] fluoro-D-glucose (2-[(18)F]FDG), in accordance with the pending FDA revision on the drug. The detections limits were 0.1 ppm for all three solvents.

Noninvasive estimation of the aorta input function for measurement of tumor blood flow with.

Quantitative measurement of tumor blood flow with [15O]water can be used to evaluate the effects of tumor treatment over time. Since quantitative flow measurements require an input function, we developed the profile fitting method (PFM) to measure the input function from positron emission tomography images of the aorta. First, a [11C]CO scan was acquired and the aorta region was analyzed.

Kinetic analysis of the 5-HT2A ligand [11C]MDL 100,907.

The goal of this study was to develop a suitable kinetic analysis method for quantification of 5-HT2A receptor parameters with [11C]MDL 100,907. Twelve control studies and four preblocking studies (400 nmol/kg unlabeled MDL 100,907) were performed in isoflurane-anesthetized rhesus monkeys. The plasma input function was determined from arterial blood samples with metabolite measurements by extraction in ethyl acetate.

Biologically stable [(18)F]-labeled benzylfluoride derivatives.

Use of the [(18)F]-fluoromethyl phenyl group is an attractive alternative to direct fluorination of phenyl groups because the fluorination of the methyl group takes place under milder reaction conditions. However, we have found that 4-FMeBWAY showed femur uptake equal to that of fluoride up to 30 min in rat whereas 4-FMeQNB had a significantly lower percent injected dose per gram in femur up to 120 min. For these and other benzylfluoride derivatives, there was no clear in vivo structure-defluorination relationship.

Brain incorporation of [1-11C]arachidonate in normocapnic and hypercapnic monkeys, measured with positron emission tomography.

Positron emission tomography (PET) was used to determine brain incorporation coefficients k* of [1-11C]arachidonate in isoflurane-anesthetized rhesus monkeys, as well as cerebral blood flow (CBF) using [15O]water. Intravenously injected [1-11C]arachidonate disappeared from plasma with a half-life of 1.1 min, whereas brain radioactivity reached a steady-state by 10 min.

Synthesis and evaluation of radioiodinated 6-iodo-L-DOPA as a cerebral L-amino acid transport marker.

Regioselective radioiodination of N-trifluoroacetyl 3,4-dimethoxy-6-trifluoroacetoxymercurio-L-phenylalanine ethyl ester 1 under no-carrier-added condition gave 6-[125I]iodo protected L-DOPA with a labeling efficiency of more than 85%, and no-carrier-added 6-[125I]I-L-DOPA was obtained with a radio-chemical purity of over 95% after hydrolysis and chromatography. A nonradioactive standard of 6-iodo protected L-DOPA was synthesized by the iododemercuration of 6-mercuric trifluoroacetate protected L-DOPA 1 using I2 in chloroform. 6-[125I]I-L-DOPA showed high brain accumulation and rapid blood clearance in mice.

Synthesis of polymer-bound 6-mercuric carboxylate DOPA precursors and solid phase labelling method of 6-radioiodinated L-DOPA.

In order to avoid separating unreacted mercury precursor and other mercury-containing compounds after the halodemercuration of a 6-mercury DOPA precursor, we developed a polymer-bound mercury precursor for the preparation of 6-halogenated DOPA. In this study, polymer-bound 6-mercuric carboxylate DOPA derivatives were synthesized from ion-exchange resin and Merrifield-type resin. Iododemercuration of polymer-bound 6-mercuric carboxylate DOPA derivatives gave higher yields (49-54%) compared with monomeric 6-mercuric trifluoroacetate protected DOPA.

Incorporation of [1-carbon-11]palmitate in monkey brain using PET.

Unlabelled: We determined regional incorporation coefficients (k*) of plasma [1-11C]palmitate into stable brain lipids of anesthetized monkeys with PET.

Methods: Carbon-11-palmitate was injected intravenously in untreated animals and in animals pretreated with methyl palmoxirate (MEP), an inhibitor of beta-oxidation of palmitate in the brain and periphery. Plasma radioactivity was followed, and brain radioactivity was determined at various times using PET.

Synthesis of polymer-bound 6-thiolatomercury and 6-mercuric sulfonate DOPA precursors and their halodemercuration reactivity.

Fluorodemercuration has the greatest utility for the preparation of 6-[18F]DOPA, but requires separation from unreacted mercury precursor and other mercury-containing compounds. One approach is the development of a polymer-bound mercury precursor. In this study, polymer-bound 6-thiolatomercury and 6-mercuric sulfonate DOPA derivatives, and its monomeric analogs were synthesized.

Comparison of bolus and infusion methods for receptor quantitation: application to [18F]cyclofoxy and positron emission tomography.

Positron emission tomography studies with the opiate antagonist [18F]cyclofoxy ([18F]CF) were performed in baboons. Bolus injection studies demonstrated initial uptake dependent on blood flow. The late uptake showed highest binding in caudate nuclei, amygdala, thalamus, and brainstem and the least accumulation in cerebellum.

PET imaging of opiate receptor binding in human epilepsy using [18F]cyclofoxy.

We used [18F]cyclofoxy (CF), a potent opiate antagonist with affinity for mu and kappa receptors, and the Scanditronix PC1024-7B PET scanner to study 14 patients with complex partial seizures (CPS), and 14 normal controls. Epileptic foci were localized by prolonged EEG-video monitoring. EEG was recorded continuously during each scan.

In vivo imaging of insulin receptors in monkeys using 18F-labeled insulin and positron emission tomography.

We previously described a prosthetic group methodology for incorporating 18F into peptides and showed that 18F-labeled insulin (18F-insulin) binds to insulin receptors on human cells (IM-9 lymphoblastoid cells) with affinity equal to that of native insulin (1). We now report studies using 18F-insulin with positron emission tomography to study binding to insulin receptors in vivo. Positron emission tomography scans were performed in six rhesus monkeys injected with 0.

A single column, rapid quality control procedure for 6-[18F]fluoro-L-dopa and 6-[18F]fluorodopamine PET imaging agents.

6-[18F]Fluoro-L-dopa and 6-[18F]fluorodopamine are promising PET imaging agents for visualizing cerebral dopaminergic centers and cardiac sympathetic innervation and function. Administration to humans requires a means to determine the purity before injection. We describe such a method using HPLC with u.

Kinetic analysis of the opiate antagonist cyclofoxy in rat brain: simultaneous infusion of active and inactive enantiomers.

The opiate antagonist (-)-cyclofoxy [(-)-CF] and the receptor inert enantiomer (+)-CF were radiolabeled with 18F or 3H and administered to conscious Sprague-Dawley rats; an isotope effect was not observed. Constant i.v.