[en] The acute distribution of ¹⁴C labeled asparagine, arginine, glycine, citric acid, fructose and glucosamine was evaluated in mice by whole-body autoradiography using a new digital microdensitometer. The results were utilized to help select compounds of interest for labelling with ultra-short-lived positron emitters, such as ¹¹C and ¹³N. Quantitative whole-body autoradiography in mice appears to be an excellent method for screening and selecting compounds of interest for radiopharmaceutical synthesis, but species differences do exist. (author)

[en] The sequential enzymatic synthesis and separation of ¹³N-L-glutamic acid and ¹³N-L-alanine are described. Basically, that involves the synthesis of ¹³N-L-glutamic acid by one enzyme, the transamination of the labeled glutamic acid to form ¹³N-L-alanine by a second enzyme, and the separation of the two amino acids by rapid column chromatography. The ¹³N-L-alanine was evaluated in animals by imaging and tissue distribution studies and showed good potential as a pancreatic imaging agent

No abstract available

[en] L-Lactic acid is formed as the end product of glycolysis under anaerobic conditions in all cells, but this reaction is of special significance in the myocardium. L-Lactic acid is reversibly formed from and is in equilibrium with myocardial pyruvic acid, which is its sole metabolic pathway. ¹¹C-Pyruvic acid is synthesized from ¹¹C carbon dioxide using pyruvate-ferredoxin oxidoreductase and coenzymes. The ¹¹C-pyruvic acid is then converted to ¹¹-L-lactic acid by lactic acid dehydrogenase. The availability of ¹¹C-pyruvic acid and ¹¹C-L-lactic acid will permit the in vivo investigation of lactate metabolism. (author)

[en] Transverse axial positron annihilation coincidence detection tomography with a stationary circular ring positron camera system is described. A prototype constructed with 64 NaI(Tl) crystal system has the capability of recording 736 - 1312 simultaneous coincidence pairs and is able to perform certain dynamic function studies

No abstract available

No abstract available

[en] Transverse axial positron annihilation coincidence detection tomography with a stationary circular ring positron camera system is described. A prototype constructed with a 64NaI(T1) crystal system has the capability of recording 736-1312 simultaneous coincidence pairs and is able to perform certain dynamic function studies. (author)

[en] Methods using 5 and 6 enzymes were devised to synthesize L-[¹¹C]glutamic acid (GA) labeled on the carboxyl group of either the α-(AGA) or γ-(GGA) carbon atom. The distribution of the ¹¹C-labeled AGA or GGA in rabbits was compared with that of L-[¹³N]glutamic acid. The results show that AGA was rapidly decarboxylated with loss of the ¹¹C-label, and that GGA was also decarboxylated, but to a lesser degree. Thus, the radiolabel distribution may not reflect the distribution of the original compound. The results also demonstrate that positron labeled pharmaceuticals may be rapidly synthesized via complex enzymatic pathways. (author)