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Normalization of <sup>11</sup> C-autoradiographic images for semi-quantitative analysis of woody tissue photosynthesis
摘要： To understand plant survival and mortality during drought it is important to gain better insights into the different mechanisms contributing to both the carbon budget and the hydraulic functioning of plants. However, the role of internally transported carbon dioxide (CO2) in xylem together with related woody tissue photosynthesis is often neglected. Trees contain large amounts of CO2 (often between 3 and 10%, and sometimes exceeding 20%), which is substantially higher than the atmospheric CO2 concentration (c. 0.04%). It is known that a portion of this locally respired CO2 escapes to the atmosphere during transport and that photosynthetic active cells in woody tissues or leaves can fix another portion. A new approach for direct visualization of woody tissue (stem) photosynthesis is presented in this study and using a radioactive 11C-tracer and autoradiographic imaging. To allow semi-quantitative comparison of woody tissue photosynthesis between different branches, a normalization method is required. We developed such a normalization technique by taking into account: (i) the radioactivity at the start of the experiment; (ii) the labeling time; (iii) the start and (iv) duration of exposure of the branch to the autoradiographic phosphor screen. In addition to these time-related parameters, we also accounted for total transpiration during the labeling experiment.
关键词： biomedical imaging,woody tissue photosynthesis,positron autoradiography
更新于2025-09-23 15:22:29
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Comparative <i>in vivo</i> imaging of arsenic and phosphorus in <i>Pteris vittata</i> gametophyte by synchrotron μ-XRF and radioactive tracer techniques
摘要： Comparative in vivo imaging of arsenic and phosphorus in Pteris vittata gametophyte by synchrotron μ-XRF and radioactive tracer techniques. Synchrotron μ-XRF and autoradiography complementally revealed the different behavior of arsenic and phosphorus in Pteris vittata L. at a high spatial resolution with its living state. We found that P. vittata develops the several sequestration mechanisms of As from important biological functions at the different growth stages. Some of them relate to the activities in the roots of the sporophyte and the reproduction on the gametophyte.
关键词： arsenic hyperaccumulator,autoradiography,synchrotron X-ray analysis
更新于2025-09-19 17:15:36
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Synthesis and Preliminary Evaluations of a Triazole-cored Antagonist ([18F]N2B-0518) as PET Imaging Probe for GluN2B Subunit in the Brain
摘要： GluN2B is the most studied subunit of N-methyl-D-aspartate receptors (NMDARs) and implicated in the pathologies of various central nervous system disorders and neurodegenerative diseases. As pan NMDAR antagonists often produce debilitating side effects, new approaches in drug discovery have shifted to subtype-selective NMDAR modulators, especially GluN2B-selective antagonists. While positron emission tomography (PET) studies of GluN2B-selective NMDARs in the living brain would enable target engagement in drug development and improve our understanding in the NMDAR signaling pathways between normal and disease conditions, a suitable PET ligand is yet to be identified. Herein we developed an 18F-labeled potent antagonist, 2-((1-(4-[18F]fluoro-3-methylphenyl)-1H-1,2,3-triazol-4-yl)methoxy)-5-methoxypyrimidine ([18F]13; also called [18F]N2B-0518) as a PET tracer for imaging the GluN2B subunit. The radiofluorination of [18F]13 was efficiently achieved by our spirocyclic iodonium ylide (SCIDY) method. In in vitro autoradiography studies, [18F]13 displayed highly region-specific binding in brain sections of rat and non-human primate, which was in accordance with the expression of GluN2B subunit. Ex vivo biodistribution in mice revealed that [18F]13 could penetrate the blood-brain barrier with moderate brain uptake (3.60% ID/g at 2 min) and rapid washout. Altogether, this work provides a GluN2B-selective PET tracer bearing new chemical scaffold and shows high specificity to GluN2B subunit in vitro, which may pave the way for the development of a new generation of GluN2B PET ligands.
关键词： subtype-selective,PET imaging,18F-labeling,autoradiography,GluN2B subunit,spirocyclic iodonium ylide
更新于2025-09-19 17:15:36
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Autoradiography Imaging in Targeted Alpha Therapy with Timepix Detector
摘要： There is a lack of data related to activity uptake and particle track distribution in targeted alpha therapy. These data are required to estimate the absorbed dose on a cellular level as alpha particles have a limited range and traverse only a few cells. Tracking of individual alpha particles is possible using the Timepix semiconductor radiation detector. We investigated the feasibility of imaging alpha particle emissions in tumour sections from mice treated with Thorium-227 (using APOMAB), with and without prior chemotherapy and Timepix detector. Additionally, the sensitivity of the Timepix detector to monitor variations in tumour uptake based on the necrotic tissue volume was also studied. Compartmental analysis model was used, based on the obtained imaging data, to assess the Th-227 uptake. Results show that alpha particle, photon, electron, and muon tracks were detected and resolved by Timepix detector. The current study demonstrated that individual alpha particle emissions, resulting from targeted alpha therapy, can be visualised and quantified using Timepix detector. Furthermore, the variations in the uptake based on the tumour necrotic volume have been observed with four times higher uptake for tumours pretreated with chemotherapy than for those without chemotherapy.
关键词： autoradiography,alpha particle imaging,targeted alpha therapy,Thorium-227,Timepix detector
更新于2025-09-09 09:28:46
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Synthesis and evaluation of 4-(2-fluoro-4-[11C]methoxyphenyl)-5-((2-methylpyridin-4-yl)methoxy)picolinamide for PET imaging of the metabotropic glutamate receptor 2 in the rat brain
摘要： Metabotropic glutamate receptor 2 (mGluR2) has been suggested as a therapeutic target for treating schizophrenia-like symptoms arising from increased glutamate transmission in the human forebrain. However, no reliable positron emission tomography (PET) radiotracer allowing for in vivo visualization of mGluR2 in the human brain is currently available. In this study, we synthesized 4-(2-fluoro-4-[11C]methoxyphenyl)-5-((2-methylpyridin-4-yl)methoxy)picolinamide ([11C]1) and evaluated its potential as a PET tracer for imaging mGluR2 in the rodent brain. Compound 1, a negative allosteric modulator (NAM) of mGluR2, showed high in vitro binding affinity (IC50: 26 nM) for mGluR2 overexpressed in human cells. [11C]1 was synthesized by O-[11C]methylation of the phenol precursor 2 with [11C]methyl iodide. After the reaction, HPLC purification and formulation, [11C]1 of 7.4 ± 2.8 GBq (n = 8) was obtained from [11C]carbon dioxide of 22.5 ± 4.8 GBq (n = 8) with >99% radiochemical purity and 70 ± 32 GBq/μmol (n = 8) molar activity at the end of synthesis. In vitro autoradiography for rat brains showed that [11C]1 binding was heterogeneously distributed in the cerebral cortex, striatum, hippocampus, and cerebellum. This pattern is consistent with the regional distribution pattern of mGluR2 in the rodent brain. The radioactivity was significantly reduced by self- or MNI-137 (a mGluR2 NAM) blocking. Small-animal PET studies indicated a low in vivo specific binding of [11C]1 in the rat brain. The brain uptake was increased in a P-glycoprotein and breast cancer resistant protein double knockout mouse, when compared to a wild-type mouse. While [11C]1 presented limited potential as an in vivo PET tracer for mGluR2, we suggested that it can be used as a lead compound for developing new radiotracers with improved in vivo brain properties.
关键词： positron emission tomography,radiotracer,schizophrenia,metabotropic glutamate receptor 2,in vitro autoradiography
更新于2025-09-04 15:30:14