Hybrid microchannel-solid state micropore device for fast and optical cell detection.

This paper presents a methodology for cell detection and counting using a device that combines PDMS (polydimethylsiloxane) microfluidic multilayer channels with a single solid state micropore. Optimal conditions of solid-state micropore fabrication from crystalline silicon wafers are presented. Micropores of varying size can be obtained by directly etching using an etchant agent concentration of 50 wt% KOH, at varying temperatures (40, 60, 80 °C) and voltages (100, 500, 1000 mV).

The utility of (11)C-arachidonate PET to study in vivo dopaminergic neurotransmission in humans.

We developed a novel method to study dopaminergic neurotransmission using positron emission tomography (PET) with [1-(11)C]arachidonic acid ([1-(11)C]AA). Previous preclinical studies have shown the utility of [1-(11)C]AA as a marker of signal transduction coupled to cytosolic phospholipase A(2) (cPLA(2)). Using [1-(11)C]AA and [(15)O]water PET, we measured regional incorporation coefficients K(*) for AA and regional cerebral blood flow (rCBF), respectively, in healthy male volunteers given the D(1)/D(2) agonist (10 or 20 μg/kg subcutaneous) apomorphine.

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.

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.

Determination of [18F]FCWAY, [18F]FP-TZTP, and their metabolites in plasma using rapid and efficient liquid-liquid and solid phase extractions.

Liquid-liquid and solid phase extraction methods were developed for the accurate and rapid quantitation of radioactive components in human plasma following injection of two PET ligands. A solid phase extraction (SPE) method was developed for the determination of the 5HT(1A) receptor ligand [N-[2-[4-(2-methoxyphenyl) piperazino]ethyl]-N-(2-pyridinyl) trans-4-[(18)F]fluorocyclohexanecarboxamide (FCWAY), and its acidic metabolite, 4-[(18)F]fluorocyclohexane carboxylic acid (FC). In both cases, the extraction method was much faster and easier to use, yet provided results comparable to HPLC and TLC methods.

PET imaging of 5-HT1A receptor binding in patients with temporal lobe epilepsy.

Background: Activation of central serotonin (5-HT)1A receptors, found in high density in brainstem raphe, hippocampus, and temporal neocortex, exerts an anticonvulsant effect in various experimental seizure models. To test the hypothesis that 5-HT1A receptor binding is reduced in human epileptic foci, PET imaging was performed using the radioligand [18F]trans-4-fluoro-N-2-[4-(2-methoxyphenyl)piperazin-1-yl]ethyl]-N-(2-pyridyl)cyclohexanecarboxamide ([18F]FCWAY), a selective 5-HT1A receptor antagonist, in patients with temporal lobe epilepsy and normal controls.

Methods: MRI and PET were performed using [15O]water and [18F]FCWAY in 10 controls and in 12 patients with temporal lobe epilepsy confirmed on ictal video-EEG; patients also underwent [18F]fluorodeoxyglucose PET.

Brain uptake of the acid metabolites of F-18-labeled WAY 100635 analogs.

The 5-HT1A ligands [ 18F]FPWAY and [ 18F]FCWAY are metabolized to [ 18F]fluorobenzoic acid (FB) and [ 18F]fluorocyclohexanecarboxylic acid (FC), respectively. To quantify the penetration of these acids into the brain, dynamic positron emission tomography studies were performed in rhesus monkeys with [ 18F]FB and [ 18F]FC. High-performance liquid chromatography analysis of arterial blood samples showed no metabolites for [ 18F]FB, whereas [ 18F]FC was rapidly metabolized to [ 18F]fluoride.

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.

Rapid hemodynamic deterioration because of acute rupture of an aneurysm of the sinus of Valsalva: the importance of echocardiography in early diagnosis.

We report a patient with an acute rupture of an aneurysm of the right sinus of Valsalva of a bicuspid aortic valve into the right atrium. This congenital disorder is a result of a weak point in the aortic wall resulting from a localized interruption of the media. Because of rapid hemodynamic deterioration, early diagnosis is mandatory and often lifesaving.

Liquid chromatography-tandem mass spectrometry identification of metabolites of two 5-HT1A antagonists, N-[2-[4-(2-methoxylphenyl)piperazino]ethyl]-N-(2-pyridyl) trans- and cis-4-fluorocyclohexanecarboxamide, produced by human and rat hepatocytes.

Two 5-HT1A antagonists, t-FCWAY and c-FCWAY, were developed as imaging agents for positron emission tomography (PET). In order to evaluate these compounds, hepatocytes from both human and rat were utilized to produce metabolites and LC-MS-MS was used to identify metabolites. These in vitro metabolism studies indicate that hydrolysis of the amide linkage is the major metabolism pathway for humans, whereas aromatic ring-oxidation is the major metabolism pathway for rat.

PET evaluation of [(18)F]FCWAY, an analog of the 5-HT(1A) receptor antagonist, WAY-100635.

We synthesized [(18)F]FCWAY, an analog of [carbonyl-(11)C]WAY-100635 ¿[(11)C]N-(2-(1-(4-(2-methoxyphenyl)-piperazinyl)ethyl))-N-(2-(pyridi nyl))cyclohexanecarboxamide¿, by replacing the cyclohexanecarbonyl group acid with a trans-4-fluorocyclohexanecarbonyl group (FC). Control and preblocking studies were performed in anesthetized monkeys. Plasma radioactive metabolite analysis showed the presence of [(18)F]FC and [(18)F]fluoride.

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.

Muscarinic cholinergic receptor measurements with [18F]FP-TZTP: control and competition studies.

[18F]Fluoropropyl-TZTP (FP-TZTP) is a subtype-selective muscarinic cholinergic ligand with potential suitability for studying Alzheimer's disease. Positron emission tomography studies in isofluorane-anesthetized rhesus monkeys were performed to assess the in vivo behavior of this radiotracer. First, control studies (n = 11) were performed to characterize the tracer kinetics and to choose an appropriate model using a metabolite-corrected arterial input function.

In vivo muscarinic binding selectivity of (R,S)- and (R,R)-[18F]-fluoromethyl QNB.

We have developed a multistep radiochemical synthesis of two diastereomers of quinuclidinyl-4-[18F]-fluoromethyl-benzilate ([18F]-FMeQNB), a high-affinity ligand for muscarinic acetylcholine receptors. Previously, we have shown that the nonradioactive (R,R)-diastereomer displays an eightfold selectivity for M1 over M2 while the nonradioactive (R,S)-diastereomer displays a sevenfold selectivity for M2 over M1 in vitro. This paper reports the results of in vivo comparison studies.

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.

Quantification of amphetamine-induced changes in [11C]raclopride binding with continuous infusion.

Positron emission tomography and single-photon emission computer tomography receptor-binding ligands can be used to measure changes in neurotransmitter levels. In particular, amphetamine-induced dopamine release has been assessed with [11C]raclopride by paired bolus injections and with [123I]iodobenzamide by using a single bolus plus infusion (B/I) study. Here, we measured the change in [11C]raclopride-specific binding in rhesus monkeys after i.

An automated radiopharmaceutical dispenser.

An automated radiopharmaceutical dispenser, that offers several advantages over manual procedures, has been developed. It employs a personal computer interfaced to a precision syringe drive module, a dose calibrator, and a printer. The operating program provides menu-selection operation and documentation of procedures and individual doses delivered.

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.

Quinolinic acid and kynurenine pathway metabolism in inflammatory and non-inflammatory neurological disease.

Neurological dysfunction, seizures and brain atrophy occur in a broad spectrum of acute and chronic neurological diseases. In certain instances, over-stimulation of N-methyl-D-aspartate receptors has been implicated. Quinolinic acid (QUIN) is an endogenous N-methyl-D-aspartate receptor agonist synthesized from L-tryptophan via the kynurenine pathway and thereby has the potential of mediating N-methyl-D-aspartate neuronal damage and dysfunction.

Inter-relationships between quinolinic acid, neuroactive kynurenines, neopterin and beta 2-microglobulin in cerebrospinal fluid and serum of HIV-1-infected patients.

Quinolinic acid (QUIN) is an neurotoxic N-methyl-D-aspartate receptor agonist and an L-tryptophan metabolite of the kynurenine pathway. Increased concentrations of QUIN occur in both cerebrospinal fluid (CSF) and blood of patients infected with human immunodeficiency virus (HIV)-1, particularly those with neurologic disturbances. In the present study of HIV-1 infected patients in Walter Reed stages 4, 5 and 6, reductions in L-tryptophan accompanied proportional increases in L-kynurenine and QUIN in both serum and CSF.

A clinical comparison of bone imaging agents.

This study compares the six commercially available kits for preparing methylene diphosphonate. The kits were randomly assigned to 134 bone examinations such that neither the physicians nor the technologists knew which brand of tracer was used. Thigh activity quantitatively varied significantly among the kits (P = 0.

Decomposition of Tc-99m pyrophosphate by peroxides in pertechnetate used in preparation.

We describe an investigation of the stability of Tc-99m pyrophosphate (Tc-99m PPi). We hve shown that addition of exogenous hydrogen peroxide to Tc-99m PPi can initiate the oxidation of the complex, giving rise to 95% unbound pertechnetate. The presence of endogenous hydrogen peroxide in the sodium pertechnetate used in the preparation of Tc-99m PPi has been thought to influence its stability.