Synthesis of [2‐{(4‐chlorophenyl) (4‐[ 125 I]iodophenyl)} methoxyethyl]‐1‐piperidine‐3‐carboxylic acid, [ 125 I]CIPCA: A potential radiotracer for GABA uptake sites

The synthesis of racemic [2‐{(4‐Chlorophenyl) (4‐iodophenyl)} methoxyethyl]‐1‐piperidine‐3‐carboxylic acid, (CIPCA) and its radioiodinated analog [ 125ß I]CIPCA is described. CIPCA was synthesized from 4‐iodobenzoyl chloride in five steps in 16% overall yield. Ammonium sulfate catalyzed solid‐state isotopic exchange of CIPCA with Na 125 I provided [ 125 I]CIPCA in 34% isolated radiochemical yield at a specific activity of 118 Ci/mmol. [ 125 ICIPCA] demonstrated moderate brain extraction and good in vivo radiostability in preliminary biodistribution studies conducted in CD‐1 mice. [ 125 I]CIPCA is a potentially useful radiotracer for study of the GABA uptake system.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90161/1/2580361008_ftp.pd

How valid are assessments of conception probability in ovulatory cycle research? Evaluations, recommendations, and theoretical implications

Over the past two decades, a large literature examining psychological changes across women's ovulatory cycles has accumulated, emphasizing comparisons between fertile and non-fertile phases of the cycle. While some studies have verified ovulation using luteinizing hormone (LH) tests, counting methods – assessments of conception probability based on counting forward from actual or retrospectively recalled onset of last menses, or backward from actual or anticipated onset of next menses – are more common. The validity of these methods remains largely unexplored. Based on published data on the distributions of the lengths of follicular and luteal phases, we created a sample of 58,000+ simulated cycles. We used the sample to assess the validity of counting methods. Aside from methods that count backward from a confirmed onset of next menses, validities are modest, generally ranging from about .40–.55. We offer power estimates and make recommendations for future work. We also discuss implications for interpreting past research

Mouse brain distribution of a carbon-11 labeled vesamicol derivative: Presynaptic marker of cholinergic neurons

The regional mouse brain distribution of a new carbon-11 labeled derivative of vesamicol, [11C]-5-(N-methylamino)benzovesamicol ([11C]MABV) is reported. Radiotracer concentrations in vivo are in the rank order of striatum>cortex>hippocampus>hypothalamus> cerebellum, consistent with reported distributions of other presynaptic cholinergic neuronal markers. In time course studies, striatum/cerebellum and cortex/cerebellum ratios for (-)-[11C]MABV continue to increase to values of 13 and 5, respectively, 75 min after i.v. injection of [11C]MABV. The specific binding in striatum and cortex is lowered by pretreatment with (+/-)-vesamicol, and shows stereoselectivity with lower uptake and lower ratios for the (+)-enantiomer. (-)-[11C]MABV is proposed as a positron-emitting radioligand for the in vivo study of presynaptic cholinergic neurons.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28961/1/0000798.pd

Iodine-125 and fluorine-18 labeled aryl-1,4-dialkylpiperazines: Potential radiopharmaceuticals for in vivo study of the dopamine uptake system

A series of fluorine-18 and iodine-125 labeled aryl-1,4-dialkylpiperazine analogs, derivatives of GBR 12935, were synthesized as radiotracers for positron emission tomography or single photon emission computerized tomography imaging of the brain based on their affinity for the presynaptic dopamine reuptake system. High specific activity fluorine-18 tracers were prepared by nucleophilic aromatic substitution reactions; iodine-125 tracers were prepared by isotopic exchange reactions. In vitro competitive binding studies demonstrated that iodine substitution is tolerated in the 4-position of the phenyl ring of the phenalkylpiperazine group. In vivo regional brain biodistribution studies in mice indicated no selectivity of the radioiodinated ligands for the dopamine reuptake site, with striatum/cerebellum concentration ratios of 1. Similar negative results with the new fluorine-18 derivatives demonstrated that in vivo selectivity for the dopamine reuptake site appears to be critically dependent on the carbon chain length between the piperazine ring and the solitary aromatic ring. These studies suggest that development of new radiopharmaceuticals based on the GBR 12935 structure cannot be based solely on considerations of in vitro binding affinities.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30090/1/0000461.pd

NMDA receptor channels: Labeling of MK-801 with iodine-125 and fluorine-18

Methods for labeling the glutamate channel blocking agent MK-801 with iodine-125 (125I) and fluorine-18 (18F) are described. Radioiodine was incorporated in the 1- or 3-positions of the aromatic ring of (+/-)MK-801 by solid-state halogen exchange techniques. Attachment of the [18F]fluoromethyl group to the bridgehead methyl position was achieved by reaction of [18F]fluoride with the triflamide alcohol 8 or the novel cyclic sulfamate 9 recently reported by Merck chemists. Radiochemical yields of (+/-)13-[18F]- fluoromethyl-MK-801 were >72%, EOB; radiochemical purity >99%. In competitive binding studies using rat brain homogenates, (+/-)3-bromo-MK-801 showed greater affinity than (+/-)MK-801 for the glutamate-linked channel. The experimental log P (2.1 +/- 0.1) of MK-801 is optimal for transit of the blood-brain barrier. These preliminary findings support further testing of 3-[123I]iodo-MK-801 and (+/-)13-[18F]fluoromethyl-MK-801 as possible agents for in vivo mapping of the glutamate receptor complex.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27605/1/0000649.pd

Synthesis of a nonpeptide carbon-11 labeled substance P antagonist for PET studies

CP 96,345 is a nonpeptide high affinity antagonist of the substance P (NK1) receptor. The radiosynthesis of [11C]CP 96,345 suitable for Positron Emission Tomography (PET) applications is described. [11C]CP 96,345 was prepared by O-methylation of a desmethyl precursor via in situ generation of its phenolate salt. The in vivo tissue distribution of [11C]CP 96,345 in guinea pigs (n = 2) at 5 and 30 min was determined. Uptake was low in brain ([approximate] 0.04% dose/g) and highest ([approximate] 1-2% dose/g) in the spleen and lungs. The present findings indicate that the use of [11C]CP 96,345 in PET might be more applicable to the study of substance P receptors in peripheral tissues involved with inflammatory disease and arthritis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30822/1/0000482.pd

Mutations in PIEZO2 Cause Gordon Syndrome, Marden-Walker Syndrome, and Distal Arthrogryposis Type 5

Gordon syndrome (GS), or distal arthrogryposis type 3, is a rare, autosomal-dominant disorder characterized by cleft palate and congenital contractures of the hands and feet. Exome sequencing of five GS-affected families identified mutations in piezo-type mechanosensitive ion channel component 2 (PIEZO2) in each family. Sanger sequencing revealed PIEZO2 mutations in five of seven additional families studied (for a total of 10/12 [83%] individuals), and nine families had an identical c.8057G>A (p.Arg2686His) mutation. The phenotype of GS overlaps with distal arthrogryposis type 5 (DA5) and Marden-Walker syndrome (MWS). Using molecular inversion probes for targeted sequencing to screen PIEZO2, we found mutations in 24/29 (82%) DA5-affected families and one of two MWS-affected families. The presence of cleft palate was significantly associated with c.8057G>A (Fisher’s exact test, adjusted p value < 0.0001). Collectively, although GS, DA5, and MWS have traditionally been considered separate disorders, our findings indicate that they are etiologically related and perhaps represent variable expressivity of the same condition

Direct optical resolution of vesamicol and a series of benzovesamicol analogues by high-performance liquid chromatography

The direct optical resolution of the vesicular acetylcholine uptake inhibitors vesamicol and benzovesamicol and nine benzovesamicol analogues were performed by HPLC on a commercially available cellulose tris(3,5-dimethylphenyl carbamate) chiral stationary phase. Separation of each enantiomeric pair was optimized with respect to solvent strength and flow-rate, using mobile phase mixtures of hexane-2-propanol-diethylamine. The method has been successfully applied to the analysis of the optical purity of benzovesamicol intermediates and products, including (-)-5-[123I]iodobenzovesamicol which is currently undergoing clinical evaluation as a tracer for mapping central cholinergic neurons, and the purification of both antipodes of ( +/-)-7-[125I]iodobenzovesamicol.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31629/1/0000563.pd

False neurotransmitters; PROS and CONS as PET tracers

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90163/1/2580260193_ftp.pd

Metabolic fate of the heart agent [18F]6-fluorometaraminol

Studies were performed to determine whether [18F]6-fluorometaraminol (18F-FMR), a new neuronal heart radiopharmaceutical, is metabolized in vivo and if the metabolites are taken up in heart. Rat, dog, baboon and guinea pig were injected with 18F-FMR and tissue samples were analyzed for metabolites by HPLC. Liver contained the most metabolites of the tissues studied with 25-90% of the radioactivity present as metabolites at 1 h in all the species studied. While metabolites of 18F-FMR are found in blood, no significant accumulation of these metabolites is found in heart ([les]0.3%) 1 h after i.v. administration in any species except rat. These studies suggest that 18F-FMR is a suitable agent for quantitative imaging of the heart by positron emission tomography.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28226/1/0000679.pd