Automated radiosynthesis of [18F]DPA-714 on a commercially available IBA Synthera®.

The goal of this work was to develop a reliable method to produce the well-validated microglial activation PET tracer, [18F]DPA-714, routinely for clinical and preclinical research using an IBA Synthera®. Optimization of literature methods included reduced precursor mass and use of TBA HCO3 as the phase transfer agent in place of Kryptofix® 222 in a 65-min synthesis with an average activity yield of 24.6 ± 3.8% (n = 5). Successful quality control testing and process validation results are reported.

Neurological Effects of Repeated Blast Exposure in Special Operations Personnel.

Exposure to blast overpressure has been a pervasive feature of combat-related injuries. Studies exploring the neurological correlates of repeated low-level blast exposure in career "breachers" demonstrated higher levels of tumor necrosis factor alpha (TNFα) and interleukin (IL)-6 and decreases in IL-10 within brain-derived extracellular vesicles (BDEVs). The current pilot study was initiated in partnership with the U.S. Special Operations Command (USSOCOM) to explore whether neuroinflammation is seen within special operators with prior blast exposure. Data were analyzed from 18 service members (SMs), inclusive of 9 blast-exposed special operators with an extensive career history of repeated blast exposures and 9 controls matched by age and duration of service. Neuroinflammation was assessed utilizing positron emission tomography (PET) imaging with [18F]DPA-714. Serum was acquired to assess inflammatory biomarkers within whole serum and BDEVs. The Blast Exposure Threshold Survey (BETS) was acquired to determine blast history. Both self-report and neurocognitive measures were acquired to assess cognition. Similarity-driven Multi-view Linear Reconstruction (SiMLR) was used for joint analysis of acquired data. Analysis of BDEVs indicated significant positive associations with a generalized blast exposure value (GBEV) derived from the BETS. SiMLR-based analyses of neuroimaging demonstrated exposure-related relationships between GBEV, PET-neuroinflammation, cortical thickness, and volume loss within special operators. Affected brain networks included regions associated with memory retrieval and executive functioning, as well as visual and heteromodal processing. Post hoc assessments of cognitive measures failed to demonstrate significant associations with GBEV. This emerging evidence suggests neuroinflammation may be a key feature of the brain response to blast exposure over a career in operational personnel. The common thread of neuroinflammation observed in blast-exposed populations requires further study.

Concussion: Beyond the Cascade.

Sport concussion affects millions of athletes each year at all levels of sport. Increasing evidence demonstrates clinical and physiological recovery are becoming more divergent definitions, as evidenced by several studies examining blood-based biomarkers of inflammation and imaging studies of the central nervous system (CNS). Recent studies have shown elevated microglial activation in the CNS in active and retired American football players, as well as in active collegiate athletes who were diagnosed with a concussion and returned to sport. These data are supportive of discordance in clinical symptomology and the inflammatory response in the CNS upon symptom resolution. In this review, we will summarize recent advances in the understanding of the inflammatory response associated with sport concussion and broader mild traumatic brain injury, as well as provide an outlook for important research questions to better align clinical and physiological recovery.

Previous fracture and subsequent fracture risk: a meta-analysis to update FRAX.

A large international meta-analysis using primary data from 64 cohorts has quantified the increased risk of fracture associated with a previous history of fracture for future use in FRAX. INTRODUCTION: The aim of this study was to quantify the fracture risk associated with a prior fracture on an international basis and to explore the relationship of this risk with age, sex, time since baseline and bone mineral density (BMD). METHODS: We studied 665,971 men and 1,438,535 women from 64 cohorts in 32 countries followed for a total of 19.5 million person-years. The effect of a prior history of fracture on the risk of any clinical fracture, any osteoporotic fracture, major osteoporotic fracture, and hip fracture alone was examined using an extended Poisson model in each cohort. Covariates examined were age, sex, BMD, and duration of follow-up. The results of the different studies were merged by using the weighted ß-coefficients. RESULTS: A previous fracture history, compared with individuals without a prior fracture, was associated with a significantly increased risk of any clinical fracture (hazard ratio, HR = 1.88; 95% CI = 1.72-2.07). The risk ratio was similar for the outcome of osteoporotic fracture (HR = 1.87; 95% CI = 1.69-2.07), major osteoporotic fracture (HR = 1.83; 95% CI = 1.63-2.06), or for hip fracture (HR = 1.82; 95% CI = 1.62-2.06). There was no significant difference in risk ratio between men and women. Subsequent fracture risk was marginally downward adjusted when account was taken of BMD. Low BMD explained a minority of the risk for any clinical fracture (14%), osteoporotic fracture (17%), and for hip fracture (33%). The risk ratio for all fracture outcomes related to prior fracture decreased significantly with adjustment for age and time since baseline examination. CONCLUSION: A previous history of fracture confers an increased risk of fracture of substantial importance beyond that explained by BMD. The effect is similar in men and women. Its quantitation on an international basis permits the more accurate use of this risk factor in case finding strategies.

Microglial activation persists beyond clinical recovery following sport concussion in collegiate athletes.

Introduction: In concussion, clinical and physiological recovery are increasingly recognized as diverging definitions. This study investigated whether central microglial activation persisted in participants with concussion after receiving an unrestricted return-to-play (uRTP) designation using [18F]DPA-714 PET, an in vivo marker of microglia activation. Methods: Eight (5 M, 3 F) current athletes with concussion (Group 1) and 10 (5 M, 5 F) healthy collegiate students (Group 2) were enrolled. Group 1 completed a pre-injury (Visit1) screen, follow-up Visit2 within 24 h of a concussion diagnosis, and Visit3 at the time of uRTP. Healthy participants only completed assessments at Visit2 and Visit3. At Visit2, all participants completed a multidimensional battery of tests followed by a blood draw to determine genotype and study inclusion. At Visit3, participants completed a clinical battery of tests, brain MRI, and brain PET; no imaging tests were performed outside of Visit3. Results: For Group 1, significant differences were observed between Visits 1 and 2 (p < 0.05) in ImPACT, SCAT5 and SOT performance, but not between Visit1 and Visit3 for standard clinical measures (all p > 0.05), reflecting clinical recovery. Despite achieving clinical recovery, PET imaging at Visit3 revealed consistently higher [18F]DPA-714 tracer distribution volume (VT) of Group 1 compared to Group 2 in 10 brain regions (p < 0.001) analyzed from 164 regions of the whole brain, most notably within the limbic system, dorsal striatum, and medial temporal lobe. No notable differences were observed between clinical measures and VT between Group 1 and Group 2 at Visit3. Discussion: Our study is the first to demonstrate persisting microglial activation in active collegiate athletes who were diagnosed with a sport concussion and cleared for uRTP based on a clinical recovery.

Imaging Diverse Pathogenic Bacteria In Vivo with 18F-Fluoromannitol PET.

Infectious disease remains the main cause of morbidity and mortality throughout the world. Of growing concern is the rising incidence of multidrug-resistant bacteria, derived from various selection pressures. Many of these bacterial infections are hospital-acquired and have prompted the Centers for Disease Control and Prevention in 2019 to reclassify several pathogens as urgent threats, its most perilous assignment. Consequently, there is an urgent need to improve the clinical management of bacterial infection via new methods to specifically identify bacteria and monitor antibiotic efficacy in vivo. In this work, we developed a novel radiopharmaceutical, 2-18F-fluoro-2-deoxy-mannitol (18F-fluoromannitol), which we found to specifically accumulate in both gram-positive and gram-negative bacteria but not in mammalian cells in vitro or in vivo. Methods: Clinical isolates of bacteria were serially obtained from wounds of combat service members for all in vitro and in vivo studies. Bacterial infection was quantified in vivo using PET/CT, and infected tissue was excised to confirm radioactivity counts ex vivo. We used these same tissues to confirm the presence of bacteria by extracting and correlating radioactive counts with colony-forming units of bacteria. Results: 18F-fluoromannitol was able to differentiate sterile inflammation from Staphylococcus aureus and Escherichia coli infections in vivo in a murine myositis model using PET imaging. Our study was extended to a laceration wound model infected with Acinetobacter baumannii, an important pathogen in the nosocomial and battlefield setting. 18F-fluoromannitol PET rapidly and specifically detected infections caused by A. baumannii and several other important pathogens (Enterococcus faecium, S. aureus, Klebsiella pneumoniae, A. baumannii, Pseudomonas aeruginosa, and Enterobacter spp.). Importantly, 18F-fluoromannitol PET was able to monitor the therapeutic efficacy of vancomycin against S. aureus in vivo. Conclusion: The ease of production of 18F-fluoromannitol is anticipated to facilitate wide radiopharmaceutical dissemination. Furthermore, the broad sensitivity of 18F-fluoromannitol for bacterial infection in vivo suggests that it is an ideal imaging agent for clinical translation to detect and monitor infections and warrants further studies in the clinical setting.

Update of the fracture risk prediction tool FRAX: a systematic review of potential cohorts and analysis plan.

We describe the collection of cohorts together with the analysis plan for an update of the fracture risk prediction tool FRAX with respect to current and novel risk factors. The resource comprises 2,138,428 participants with a follow-up of approximately 20 million person-years and 116,117 documented incident major osteoporotic fractures. INTRODUCTION: The availability of the fracture risk assessment tool FRAX® has substantially enhanced the targeting of treatment to those at high risk of fracture with FRAX now incorporated into more than 100 clinical osteoporosis guidelines worldwide. The aim of this study is to determine whether the current algorithms can be further optimised with respect to current and novel risk factors. METHODS: A computerised literature search was performed in PubMed from inception until May 17, 2019, to identify eligible cohorts for updating the FRAX coefficients. Additionally, we searched the abstracts of conference proceedings of the American Society for Bone and Mineral Research, European Calcified Tissue Society and World Congress of Osteoporosis. Prospective cohort studies with data on baseline clinical risk factors and incident fractures were eligible. RESULTS: Of the 836 records retrieved, 53 were selected for full-text assessment after screening on title and abstract. Twelve cohorts were deemed eligible and of these, 4 novel cohorts were identified. These cohorts, together with 60 previously identified cohorts, will provide the resource for constructing an updated version of FRAX comprising 2,138,428 participants with a follow-up of approximately 20 million person-years and 116,117 documented incident major osteoporotic fractures. For each known and candidate risk factor, multivariate hazard functions for hip fracture, major osteoporotic fracture and death will be tested using extended Poisson regression. Sex- and/or ethnicity-specific differences in the weights of the risk factors will be investigated. After meta-analyses of the cohort-specific beta coefficients for each risk factor, models comprising 10-year probability of hip and major osteoporotic fracture, with or without femoral neck bone mineral density, will be computed. CONCLUSIONS: These assembled cohorts and described models will provide the framework for an updated FRAX tool enabling enhanced assessment of fracture risk (PROSPERO (CRD42021227266)).

Dissecting Fc signatures of protection in neonates following maternal influenza vaccination in a placebo-controlled trial.

Influenza is an important cause of illness and morbidity for infants. Seasonal influenza vaccination during pregnancy aims to provide protection to mothers, but it can also provide immunity to infants. The precise influence of maternal vaccination on immunity in infants and how vaccine-elicited antibodies provide protection in some but not all infants is incompletely understood. We comprehensively profiled the transfer of functional antibodies and defined humoral factors contributing to immunity against influenza in a clinical trial of maternal influenza vaccination. Influenza-specific antibody subclass levels, Fc ɣ receptor (FCGR) binding levels, and antibody-dependent innate immune functions were all profiled in the mothers during pregnancy and at birth, as well as in cord blood. Vaccination increased influenza-specific antibody levels, antibody binding to FCGR, and specific antibody-dependent innate immune functions in both maternal and cord blood, with FCGR binding most enhanced via vaccination. Influenza-specific FCGR binding levels were lower in cord blood of infants who subsequently developed influenza infection. Collectively these data suggest that in addition to increased antibody amounts, the selective transfer of FCGR-binding antibodies contributes to the protective immune response in infants against influenza.

Calcaneal quantitative ultrasound is associated with all-cause and cardiovascular disease mortality independent of hip bone mineral density.

Osteoporosis has been linked with increased risk of cardiovascular disease previously. However, few studies have detailed bone and vascular information. In a prospective study of older women, we demonstrated heel quantitative ultrasound measures were associated with increased cardiovascular and all-cause mortality, independent of established cardiovascular risk factors. INTRODUCTION: Osteoporosis and low bone mineral density (BMD) have been previously linked to cardiovascular disease (CVD) and mortality. Calcaneal quantitative ultrasound (QUS) is used to evaluate bone material properties, especially in older women. However, it is uncertain whether it is related to risk of mortality. This study was aimed to investigate the association between calcaneal QUS measurements and 15-year all-cause and CVD mortality in 1404 older women (mean age 75.2 ± 2.7 years). METHODS: One thousand four hundred four older women, participants of Calcium Intake Fracture Outcome study (CAIFOS), had calcaneal bone measured at baseline (1998) and followed for 15 years. The primary outcomes, any deaths, and deaths attributable to cardiovascular causes ascertained by using linked data were obtained from Western Australia data linkage system. RESULTS: Over the 15 years of follow-up (17,955 person years), 584 of the women died, and 223 from CVD. For every standard deviation (SD), reduction in broadband ultrasound attenuation (BUA) in minimally and multivariable-adjusted model including cardiovascular risk factors increased relative hazards for all-cause (multivariable-adjusted HR 1.15; 95%CI: 1.06-1.26, p = 0.001) and CVD mortality (multivariable-adjusted HR 1.20; 95%CI: 1.04-1.38, p = 0.010). Such relationships also persisted when hip BMD was included in the model (all-cause mortality HR 1.19; 95%CI: 1.07-1.33, p = 0.002; CVD mortality HR 1.28; 95%CI: 1.07-1.53, p = 0.008). CONCLUSION: BUA is associated with all-cause and CVD mortality in older women independent of BMD and established CVD risk factors. Understanding why and how these are related may provide further insights about the bone-vascular nexus as well as therapeutic targets benefiting both systems.

An automated radiosynthesis of [18F]DPA-714 on a commercially available radiosynthesizer, Elixys Flex/Chem.

[18F]DPA-714 is a radiotracer specific to the translocator protein (TSPO) and is useful for in vivo Positron Emission Tomography imaging studies. In this report, we have developed an automated radiosynthesis of [18F]DPA-714 on a commercially-available radiosynthesis platform, which comports with USP <823> guidelines. The wide availability of the radiosynthesis module and ease of dissemination of the production sequence will facilitate preclinical and clinical research of TSPO-related pathology.

Dynamics of breast milk antibody titer in the six months following SARS-CoV-2 infection.

BACKGROUND: While a growing body of literature describes antibody dynamics in serum, little is known about breast milk antibody titers in the months following SARS-CoV-2 infection. OBJECTIVES: We evaluated the dynamics of the humoral immune response to SARS-CoV-2 in two women who were breastfeeding when infected. We assessed paired breast milk and serum samples for six months post-infection for antibodies specific to the SARS-CoV-2 receptor binding domain (RBD) of the spike protein. RESULTS: Starting at 10 days after symptom onset, IgA antibody levels were persistent over a 6-month time period in human milk. For both mothers, no detectable IgA was found in the samples collected pre-symptom onset. RBD-specific IgG and IgM antibodies in tandem serum collected from the two donors demonstrated stable IgG levels over the six-month time period post-symptom onset. CONCLUSIONS: We found that breastfeeding mothers produced a durable IgA response for up to six months following COVID-19 infection, suggesting an important role for breast milk in protection of infants.

ImmunoPET-informed sequence for focused ultrasound-targeted mCD47 blockade controls glioma.

Phagocytic immunotherapies such as CD47 blockade have emerged as promising strategies for glioblastoma (GB) therapy, but the blood brain/tumor barriers (BBB/BTB) pose a persistent challenge for mCD47 delivery that can be overcome by focused ultrasound (FUS)-mediated BBB/BTB disruption. We here leverage immuno-PET imaging to determine how timing of [89Zr]-mCD47 injection relative to FUS impacts antibody penetrance into orthotopic murine gliomas. We then design and implement a rational paradigm for combining FUS and mCD47 for glioma therapy. We demonstrate that timing of antibody injection relative to FUS BBB/BTB disruption is a critical determinant of mCD47 access, with post-FUS injection conferring superlative antibody delivery to gliomas. We also show that mCD47 delivery across the BBB/BTB with repeat sessions of FUS can significantly constrain tumor outgrowth and extend survival in glioma-bearing mice. This study generates provocative insights for ongoing pre-clinical and clinical evaluations of FUS-mediated antibody delivery to brain tumors. Moreover, our results confirm that mCD47 delivery with FUS is a promising therapeutic strategy for GB therapy.

Comparative effectiveness of denosumab, teriparatide, and zoledronic acid among frail older adults: a retrospective cohort study.

The comparative effects of zoledronic acid, denosumab, and teriparatide for preventing hip fractures in frail older adults, especially those in nursing homes, were unknown. We found that denosumab and zoledronic acid may be as effective as teriparatide for hip fracture prevention in nursing home residents. INTRODUCTION: Several non-oral drugs exist for osteoporosis treatment, including zoledronic acid (ZA), denosumab, and teriparatide. Little data exist on the comparative effectiveness of these drugs for hip fracture prevention in frail older adults. We examined their comparative effectiveness in one of the frailest segments of the US population-nursing home (NH) residents. METHODS: We conducted a national retrospective cohort study of NH residents aged ≥ 65 years using 2012 to 2016 national US Minimum Data Set clinical assessment data and linked Medicare claims. New parenteral ZA, denosumab, and teriparatide use was assessed via Medicare Parts B and D; hip fracture outcomes via Part A; and 125 covariates for confounding adjustment via several datasets. We used inverse probability weighted (IPW) competing risk regression models to compare hip fracture risk between groups with teriparatide as the reference. RESULTS: The study cohort (N = 2019) included 1046 denosumab, 578 teriparatide, and 395 ZA initiators. Mean age was 85 years, 90% were female, and 68% had at least moderate functional impairment. Seventy-two residents (3.6%) had a hip fracture and 1100 (54.5%) died over a mean follow-up of 1.5 years. Compared to teriparatide use, denosumab use was associated with a 46% lower risk of hip fracture (HR 0.54, 95% CI 0.29-1.00) and no difference was observed for ZA (HR 0.70, 95% CI 0.26-1.85). CONCLUSIONS: Denosumab and ZA may be as effective as teriparatide for hip fracture prevention in frail older adults. Given their lower cost and easier administration, denosumab and ZA are likely preferable non-oral treatments for most frail, older adults.

Bone density and strength from thoracic and lumbar CT scans both predict incident vertebral fractures independently of fracture location.

In a population-based study, we found that computed tomography (CT)-based bone density and strength measures from the thoracic spine predicted new vertebral fracture as well as measures from the lumbar spine, suggesting that CT scans at either the thorax or abdominal regions are useful to assess vertebral fracture risk. INTRODUCTION: Prior studies have shown that computed tomography (CT)-based lumbar bone density and strength measurements predict incident vertebral fracture. This study investigated whether CT-based bone density and strength measurements from the thoracic spine predict incident vertebral fracture and compared the performance of thoracic and lumbar bone measurements to predict incident vertebral fracture. METHODS: This case-control study of community-based men and women (age 74.6 ± 6.6) included 135 cases with incident vertebral fracture at any level and 266 age- and sex-matched controls. We used baseline CT scans to measure integral and trabecular volumetric bone mineral density (vBMD) and vertebral strength (via finite element analysis, FEA) at the T8 and L2 levels. Association between these measurements and vertebral fracture was determined by using conditional logistic regression. Sensitivity and specificity for predicting incident vertebral fracture were determined for lumbar spine and thoracic bone measurements. RESULTS: Bone measurements from T8 and L2 predicted incident vertebral fracture equally well, regardless of fracture location. Specifically, for predicting vertebral fracture at any level, the odds ratio (per 1-SD decrease) for the vBMD and strength measurements at L2 and T8 ranged from 2.0 to 2.7 (p < 0.0001) and 1.8 to 2.8 (p < 0.0001), respectively. Results were similar when predicting fracture only in the thoracic versus the thoracolumbar spine. Lumbar and thoracic spine bone measurements had similar sensitivity and specificity for predicting incident vertebral fracture. CONCLUSION: These findings indicated that like those from the lumbar spine, CT-based bone density and strength measurements from the thoracic spine may be useful for identifying individuals at high risk for vertebral fracture.

Correction to: The factor-of-risk biomechanical approach predicts hip fracture in men and women: the Framingham Study.

The original version of this article, published 23 February 2011, unfortunately contained a mistake. The following correction has therefore been made in the original.

Alternative splicing in a presenilin 2 variant associated with Alzheimer disease.

OBJECTIVE: Autosomal-dominant familial Alzheimer disease (AD) is caused by by variants in presenilin 1 (PSEN1), presenilin 2 (PSEN2), and amyloid precursor protein (APP). Previously, we reported a rare PSEN2 frameshift variant in an early-onset AD case (PSEN2 p.K115Efs*11). In this study, we characterize a second family with the same variant and analyze cellular transcripts from both patient fibroblasts and brain lysates. METHODS: We combined genomic, neuropathological, clinical, and molecular techniques to characterize the PSEN2 K115Efs*11 variant in two families. RESULTS: Neuropathological and clinical evaluation confirmed the AD diagnosis in two individuals carrying the PSEN2 K115Efs*11 variant. A truncated transcript from the variant allele is detectable in patient fibroblasts while levels of wild-type PSEN2 transcript and protein are reduced compared to controls. Functional studies to assess biological consequences of the variant demonstrated that PSEN2 K115Efs*11 fibroblasts secrete less Aß 1-40 compared to controls, indicating abnormal γ-secretase activity. Analysis of PSEN2 transcript levels in brain tissue revealed alternatively spliced PSEN2 products in patient brain as well as in sporadic AD and age-matched control brain. INTERPRETATION: These data suggest that PSEN2 K115Efs*11 is a likely pathogenic variant associated with AD. We uncovered novel PSEN2 alternative transcripts in addition to previously reported PSEN2 splice isoforms associated with sporadic AD. In the context of a frameshift, these alternative transcripts return to the canonical reading frame with potential to generate deleterious protein products. Our findings suggest novel potential mechanisms by which PSEN variants may influence AD pathogenesis, highlighting the complexity underlying genetic contribution to disease risk.

Prediction of incident vertebral fracture using CT-based finite element analysis.

Prior studies show vertebral strength from computed tomography-based finite element analysis may be associated with vertebral fracture risk. We found vertebral strength had a strong association with new vertebral fractures, suggesting that vertebral strength measures identify those at risk for vertebral fracture and may be a useful clinical tool. INTRODUCTION: We aimed to determine the association between vertebral strength by quantitative computed tomography (CT)-based finite element analysis (FEA) and incident vertebral fracture (VF). In addition, we examined sensitivity and specificity of previously proposed diagnostic thresholds for fragile bone strength and low BMD in predicting VF. METHODS: In a case-control study, 26 incident VF cases (13 men, 13 women) and 62 age- and sex-matched controls aged 50 to 85 years were selected from the Framingham multi-detector computed tomography cohort. Vertebral compressive strength, integral vBMD, trabecular vBMD, CT-based BMC, and CT-based aBMD were measured from CT scans of the lumbar spine. RESULTS: Lower vertebral strength at baseline was associated with an increased risk of new or worsening VF after adjusting for age, BMI, and prevalent VF status (odds ratio (OR) = 5.2 per 1 SD decrease, 95% CI 1.3-19.8). Area under receiver operating characteristic (ROC) curve comparisons revealed that vertebral strength better predicted incident VF than CT-based aBMD (AUC = 0.804 vs. 0.715, p = 0.05) but was not better than integral vBMD (AUC = 0.815) or CT-based BMC (AUC = 0.794). Additionally, proposed fragile bone strength thresholds trended toward better sensitivity for identifying VF than that of aBMD-classified osteoporosis (0.46 vs. 0.23, p = 0.09). CONCLUSION: This study shows an association between vertebral strength measures and incident vertebral fracture in men and women. Though limited by a small sample size, our findings also suggest that bone strength estimates by CT-based FEA provide equivalent or better ability to predict incident vertebral fracture compared to CT-based aBMD. Our study confirms that CT-based estimates of vertebral strength from FEA are useful for identifying patients who are at high risk for vertebral fracture.

Improved, one-pot synthesis of 6-[18 F]fluorodopamine and quality control testing for use in patients with neuroblastoma.

6-[18 F]Fluorodopamine ([18 F]F-DA) is taken into cells via the norepinephrine transporter (NET). Recent [18 F]F-DA positron emission tomography-computed tomography (PET-CT) imaging of adult neuroendocrine tumors shows a dramatic improvement in sensitivity over the standard-of-care, meta-iodobenzylguanidine (MIBG) single-photon emission computed tomography (SPECT)-CT. A new precursor (ALPdopamine™) allows no-carrier-added synthesis resulting in high-molar activity [18 F]F-DA. Automated synthesis of [18 F]F-DA was performed in a single reactor using a two-step procedure: 1) fluorination via thermolysis of a diaryliodonium salt precursor, followed by 2) acid hydrolysis. Phase transfer agents, Kryptofix 222 and two tetraalkylammonium salts, were investigated. Optimized synthesis of [18 F]F-DA was achieved in 56 to 60 minutes (26% end of synthesis [EOS], nondecay corrected). The product passed all Food and Drug Administration (FDA)-required quality control testing for human use. Accumulation of [18 F]F-DA in SK-N-BE(2)-C (high NET expression) cells was significantly higher than in SH-EP (minimal NET expression) cells (P < 0.0001). ALPdopamine provides an effective scaffold for the routine production of [18 F]F-DA for human use. Validation of uptake by neuroblastoma (NB) cell lines supports the use of [18 F]F-DA for imaging NB patients. A pediatric NB imaging trial using [18 F]F-DA PET has been approved (Investigational New Drug application (IND) no. 138638) based on the methods reported here. We expect [18 F]F-DA will be localized in NB tumors and that high-quality functional images will be obtained within minutes after injection.

Radiosynthesis, ex Vivo Biodistribution, and in Vivo Positron Emission Tomography Imaging Evaluations of [11C]2-Pyridinealdoxime Methiodide ([11C]2-PAM): A First-In-Class Antidote Tracer for Organophosphate Intoxication.

2-Pyridinealdoxime methiodide (2-PAM) is a widely used antidote for the treatment of organophosphorus (OP) exposure that reactivates the target protein acetylcholinesterase. Carbon-11 2-PAM was prepared to more fully understand the in vivo mode of action, distribution, and dynamic qualities of this important countermeasure. Alkylation of 2-pyridinealdoxime with [11C]CH3I provided the first-in-class [11C]2-PAM tracer in 3.5% decay corrected radiochemical yield from [11C]CH3I, >99% radiochemical purity, and 4831 Ci/mmol molar activity. [11C]2-PAM tracer distribution was evaluated by ex vivo biodistribution and in vivo dynamic positron emission tomography (PET) imaging in naïve (OP exposure deficient) rats. Tracer alone and tracer coinjected with a body mass-scaled human therapeutic dose of 30 mg/kg nonradioactive 2-PAM demonstrated statistically similar tissue and blood distribution profiles with the greatest uptake in kidney and significantly lower levels in liver, heart, and lung with lesser amounts in blood and brain. The imaging and biodistribution data show that radioactivity uptake in brain and peripheral organs is rapid and characterized by differential tissue radioactivity washout profiles. Analysis of arterial blood samples taken 5 min after injection showed ∼82% parent [11C]2-PAM tracer. The imaging and biodistribution data are now established, enabling future comparisons to outcomes acquired in OP intoxicated rodent models.

The T-Box Riboswitch: tRNA as an Effector to Modulate Gene Regulation.

The T-box riboswitch is a unique, RNA-based regulatory mechanism that modulates expression of a wide variety of amino acid-related genes, predominantly in Firmicutes. RNAs of this class selectively bind a specific cognate tRNA, utilizing recognition of the tRNA anticodon and other tRNA features. The riboswitch monitors the aminoacylation status of the tRNA to induce expression of the regulated downstream gene(s) at the level of transcription antitermination or derepression of translation initiation in response to reduced tRNA charging via stabilization of an antiterminator or antisequestrator. Recent biochemical and structural studies have revealed new features of tRNA recognition that extend beyond the initially identified Watson-Crick base-pairing of a codon-like sequence in the riboswitch with the tRNA anticodon, and residues in the antiterminator or antisequestrator with the tRNA acceptor end. These studies have revealed new tRNA contacts and new modes of riboswitch function and ligand recognition that expand our understanding of RNA-RNA recognition and the biological roles of tRNA.