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Four patients with radiologically normal pituitary gland were examined with positron emission tomography after the administration of (methyl-C)-L-methionine. On a following day the examination was repeated with (methyl-c)-D-methionine. The accumulation rate of L-methionine in the pituitary was measured, giving a value that was about twice that of normal brain tissue. The accumulation rate of D-methionine in the pituitary was almost a factor of 10 lower than that of L-methionine. In the normal brain tissue that ratio was 2.3. The study clearly indicates that the methionine uptake in the pituitary is stereospecific. C-D-methionine is freely distributed in the tissue without entrapment, whereas C-L-methionine is irreversibly bound. It is concluded that PET with C-L-methionine can be used to study amino acid utilization in the pituitary. [ABSTRACT FROM AUTHOR]

Specific binding of [C]-N-methyl-spiperone to striatal dopamine D2 receptors was assessed using positron emission tomography (PET) in 6 patients with adult-onset focal dystonia (predominantly spasmodic torticollis) and in 5 healthy subjects. No significant difference in average specific striatal tracer uptake between patients and healthy subjects was found. However, in the 5 patients showing lateralisation of clinical signs a trend to higher striatal tracer uptake in the contralateral hemisphere was observed. [ABSTRACT FROM AUTHOR]

N-[methyl-C] nicotine (C-nicotine) was given intravenously to monkeys and the uptake and regional distribution of radioactivity was followed in the brain using positron emission tomography (PET). TheC-radioactivity in the brain peaked within 1-2 min and then rapidly declined. Pretreatment with unlabelled nicotine (10 μg/kg) reduced the uptake ofC-radioactivity to the brain by 30%. The uptake of radioactivity was higher following (+)C-nicotine than (−)C-nicotine. Both enantiomers were distributed in a similar manner within the brain. When animals were infused with a peripheral nicotinic blocker (trimetaphan) the uptake of radioactivity to the brain was lower following (+)C-nicotine compared to (−)C-nicotine. The amount of radioactivity was high in the occipital cortex, thalamus, intermediate in the frontal cortex and low in white matter in (−)C injected monkeys while no regional difference in distribution ofC-radioactivity was observed after injection of (+)C-nicotine. [ABSTRACT FROM AUTHOR]