Performing radiosynthesis in microvolumes to maximize molar activity of tracers for positron emission tomography

For many applications, positron emission tomography tracers must be produced with high specific activity. Here the authors identify variables leading to increased specific activity when tracers are synthesized in microliter volumes, and show that specific activity can influence tracer biodistribution

The Radiopharmaceutical Chemistry of Fluorine-18: Nucleophilic Fluorinations

The positron-emitting radionuclide fluorine-18 plays a prominent role in radiopharmaceuticals for positron emission tomography (PET) due to its favourable nuclear decay properties. Depending on the production method, 18F can be obtained in two different chemical forms: electrophilic [18F]fluorine gas and nucleophilic [18F]fluoride. Nucleophilic [18F]fluoride exhibits several advantages with respect to accessibility and chemical handling. Therefore, nucleophilic 18F-substitution reactions are of pivotal importance for the production of PET radiotracers. This chapter is devoted to this class of reactions, and in the following pages, we seek to provide a general overview of 18F itself as well as insights into nucleophilic 18F-substitution reactions. More specifically, the prerequisites for this reaction with regard to solvent, leaving groups, reactants, etc. are examined. Furthermore, several examples are discussed which demonstrate the potential of this reaction to create highly clinical relevant PET tracers. Finally, this chapter also provides practical tips and tricks for those performing this reaction in the laboratory

Global profiling of genes modified by endoplasmic reticulum stress in pancreatic beta cells reveals the early degradation of insulin mRNAs

AIMS/HYPOTHESIS: Pancreatic beta cells respond to endoplasmic reticulum (ER) stress by activating the unfolded protein response. If the stress is prolonged, or the adaptive response fails, apoptosis is triggered. We used a 'homemade' microarray specifically designed for the study of beta cell apoptosis (the APOCHIP) to uncover mechanisms regulating beta cell responses to ER stress. MATERIALS AND METHODS: A time course viability and microarray analysis was performed in insulin-producing INS-1E cells exposed to the reversible ER stress inducer cyclopiazonic acid (CPA). Modification of selected genes was confirmed by real-time RT-PCR, and the observed inhibition of expression of the insulin-1 (Ins1) and insulin-2 (Ins2) genes was further characterised in primary beta cells exposed to a diverse range of agents that induce ER stress. RESULTS: CPA-induced ER stress modified the expression of 183 genes at one or more of the time points studied. The expression of most of these genes returned to control levels after a 3 h recovery period following CPA removal, with all cells surviving. Two groups of genes were particularly affected by CPA, namely, those related to cellular responses to ER stress, which were mostly upregulated, and those related to differentiated beta cell functions, which were downregulated. Levels of Ins1 and Ins2 mRNAs were severely decreased in response to CPA treatment as a result of degradation, and there was a concomitant increase in the level of IRE1 activation. CONCLUSIONS/INTERPRETATION: In this study we provide the first global analysis of beta cell molecular responses to a severe ER stress, and identify the early degradation of mRNA transcripts of the insulin genes as an important component of this response.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe