[125I]-2-(2,5-dimethoxy-4-iodophenyl)aminoethane ([125I]-2C-I) as a label for the 5-HT2 receptor in rat frontal cortex.

Recent studies of 5-HT2 receptor binding have involved the use of radiolabeled agonists. This report describes the use of [125I]-2-(2,5-dimethoxy-4-iodophenyl)aminoethane ([125I]-2C-I) as a label for low-density 5-HT2 agonist binding sites. A nonhydrolyzable analog of GTP, GppNHp, was found to inhibit the high affinity binding of [125I]-2C-I.

Regional cerebral glucose transport and utilization in Alzheimer's disease.

We performed dynamic positron emission tomographic (PET) studies of glucose utilization, using (18F) 2-fluoro-2-deoxy-D-glucose (FDG), in patients with probable Alzheimer's disease (AD) and healthy age-matched controls, to evaluate blood-brain-barrier glucose transport and glucose utilization rates in the disease. We found no significant differences in rate constants for glucose transport (k1 and k2) and phosphorylation (k3), nor for the vascular fraction (fv), between the 2 groups, although k3 and fv were relatively depressed in temporal cortex in AD. Absolute rates of glucose use were depressed in temporal and parietal cortex, and relative rCMRglc rates were lower in frontal, temporal, parietal, and occipital cortices.

A radiosynthesis of fluorine-18 fluoromisonidazole.

A new preparation of [18F]fluoromisonidazole [1H-1-(3-[18F] fluoro-2-hydroxypropyl)-2-nitroimidazole] is presented as a two-step, two-pot reaction sequence. The method is useful for the production of 20-30 mCi quantities of this compound from [18F]fluoride, available in 40% radiochemical yield at end of bombardment (EOB) with a specific activity (nca) of greater than 650 Ci/mmol (EOB) and a synthesis time of approximately 140 min. The key feature of the reaction scheme is the preparation of a new fluoroalkylating agent, [18F]epifluorohydrin.

Common receptors for hallucinogens in rat brain: a comparative autoradiographic study using [125I]LSD and [125I]DOI, a new psychotomimetic radioligand.

The S and R enantiomers of the psychotomimetic 5HT2 agonist DOI (2,5-dimethoxy-4-iodophenylisopropylamine) were labeled with 125I at high-specific activity. The regional distribution of binding sites for each of the enantiomers was investigated using in vitro quantitative autoradiography and compared to the regional distribution of [125I]LSD in the rat brain. Saturable, specific binding of the radioligands was determined in cortical membrane homogenates.

(R)-(-)-[77Br]4-bromo-2,5-dimethoxyamphetamine labels a novel 5-hydroxytryptamine binding site in brain membranes.

(R)-(-)-[77Br]4-Bromo-2,5-dimethoxyamphetamine [(R)-(-)-[77Br] DOB] was synthesized to a high specific activity (1875 +/- 50 Ci/mmol) and used to label membrane-associated recognition sites in rat brain. (R)-(-)-[77Br]DOB displayed high affinity (KD = 0.60 +/- 0.

Chest radiography in infant cardiac allotransplantation.

Heart transplants were performed in seven infants at Loma Linda University Medical Center from 1985 to 1987. Five of these seven patients survived. In this report, the radiographic appearance of the chest is presented before surgery, immediately after surgery, and during a documented episode of rejection.

R(-)-2,5-dimethoxy-4-77 bromoamphetamine [77Br-R(-)DOB]: a novel radioligand which labels a 5-HT binding site subtype.

R(-)-2,5-Dimethoxy-4-77Br-amphetamine [77Br-R(-)DOB], a radioligand of high specific activity (1500 +/- 200 Ci/mmol), was used to label membrane-associated recognition sites in rat brain. 77Br-R(-)DOB sites were of high affinity (KD = 0.19 nM) but low density (Bmax = 0.

Binding to the serotonin 5-HT2 receptor by the enantiomers of 125I-DOI.

Preliminary receptor binding experiments with the stereoisomers of 125I-DOI, a new putative 5-HT2 agonist ligand, were conducted. The results indicated specific binding for both enantiomers, with a two-site model giving the best fit to the binding data. R-125I-DOI showed a high affinity dissociation constant of 1.

Synthesis and in vivo evaluation of 122I- and 131I-labelled iodoperidol, a potential agent for the tomographic assessment of cerebral perfusion.

Iodoperidol (IP), an iodinated analogue of the antipsychotic drug haloperiodol, was evaluated as a cerebral blood flow radiopharmaceutical for PET or SPECT. IP was labelled with 131I or 122I (76% beta +, t1/2 = 3.6 min) in greater than 75% radiochemical yield via electrophilic aromatic iododestannylation.

Comparative evaluation of electrophilic aromatic iododemetallation techniques for labeling radiopharmaceuticals with iodine-122.

A series of metallated arenes bearing sigma-bonded tin, mercury, germanium, boron, or silicon were evaluated as labeling substrates for the generator-produced positron emitter 122I(t1/2 = 3.6 min). Using dichloramine-T with 122I, radiochemical yields exceeding 90% were achieved after 1 min at 25 degrees C using stannylated or mercurated arenes in ethanol, or germylated arenes in acidic solvent.

Size and X-ray density of normal and denervated muscles of the human leg and forearm.

An accurate assessment of muscle size and tissue density can be obtained by X-ray computed tomography. CAT scans of the extensor and flexor muscle compartments of the leg and forearm were performed on normal subjects to establish: normal ranges of muscle densities, and the effect of sex and side dominance on muscle size and density. The same muscle groups were studied in patients with nerve damage resulting in either total or very extensive denervation of the corresponding muscle compartments.

18F-labelled N,N-dimethylamphetamine analogues for brain imaging studies.

The radiochemical yields of nine N,N-dimethyl-2-(substituted phenyl)-isopropylamines (amphetamine analogues) were determined following reaction with [18F]acetyl hypofluorite in a 0.1 M HCl solution at room temperature. The meta-dimethoxy substituted amphetamines gave the highest radiofluorination yields (24-32% at EOB).

A 122Xe-122I generator for remote radio-iodinations.

A 122Xe-122I generator system is described that produces 122I extraction efficiencies of approximately 60%. Radiocontaminants were less than 0.1% at the time of 122I removal following a 10 min ingrowth period.

Gallium-68 lipophilic complexes for labeling platelets.

Generator produced 68Ga-labeled platelets could be useful for positron emission tomographic (PET) studies of thrombosis or atherosclerosis. To label platelets with 68Ga, we have studied the effects of trace metals in elutions of 68Ga from 68Ge. Studies were conducted on the formation of lipophilic 68Ga complexes 8-hydroxyquinoline, tropolone, and mercaptopyridine-N-oxide (MPO).

Iodine-122-labeled amphetamine derivative with potential for PET brain blood-flow studies.

The positron emitter 122I (t1/2 3.6 min) was collected from a xenon-122/iodine-122 (122Xe/122I) generator and incorporated into an amphetamine analog, 2,4-dimethoxy-N,N-dimethyl-5-[122I]iodophenylisopropylamine (5-[122I]-2,4-DNNA). The remote synthesis was achieved in 3 min with a 50% radioincorporation yield and a product radiopurity of greater than 98%.

Radiohalogen-labeled imaging agents. 3. Compounds for measurement of brain blood flow by emission tomography.

The radioiodine-labeled amines currently available as brain-imaging agents, based on our previous work and that of others, are prepared either by exchange labeling or by direct iodination of a protected intermediate. The intrinsic slowness of these processes limits their potential for use with the positron-emitting 122I, as it has a half-life of only 3.6 min.

The gamma-aminobutyric acid receptor in catfish brain.

When the binding of [3H]gamma-aminobutyric acid (GABA) to its receptor in catfish synaptic membranes was studied, a high affinity (Kd = 8.4 nM) and a low affinity (Kd = 65 nM) binding component was observed. Muscimol, thiomuscimol, tetrahydroisoxazole-5,4-c-pyridin-3-ol, imidazole acetic acid and bicuculline each competitively inhibited both high affinity and low affinity [3H]GABA binding.

Labeled choline and phosphorylcholine: body distribution and brain autoradiography: concise communication.

Following intravenous injection of labeled choline or phosphorylcholine in rats and mice, the brain uptake as percent injected dose was less than 0.2% with 6-12% going to kidney and 3-6% to liver. A study of [14C]choline autoradiography in a stump-tailed macaque demonstrated a five- to sixfold greater uptake in gray matter than in white matter.

Regional cerebral metabolic alterations in dementia of the Alzheimer type: positron emission tomography with [18F]fluorodeoxyglucose.

Alzheimer disease is the most common cause of dementia in adults. Despite recent advances in our understanding of its anatomy and chemistry, we remain largely ignorant of its pathogenesis, physiology, diagnosis, and treatment. Dynamic positron emission tomography using [18F]fluorodeoxyglucose (FDG) was performed on the Donner 280-crystal ring in 10 subjects with dementia of the Alzheimer type and six healthy age-matched controls.

Nitrogen-13-labeled nitrite and nitrate: distribution and metabolism after intratracheal administration.

Radioactive nitrogen-13 from nitrite (NO2-) or nitrate (NO3-) administered intratracheally or intravenously without added carrier to mice or rabbits was distributed evenly throughout most organs and tissues regardless of the entry route or the anion administered. Nitrogen-13 from both anions was distributed uniformly between plasma and blood cells. We found rapid in vivo oxidation of NO2- to NO3- at concentrations of 2 to 3 nanomoles per liter in blood.