Refine
Has Fulltext
- yes (71)
Is part of the Bibliography
- yes (71)
Year of publication
Document Type
- Journal article (58)
- Preprint (5)
- Conference Proceeding (4)
- Book article / Book chapter (2)
- Doctoral Thesis (2)
Keywords
- Positronen-Emissions-Tomografie (9)
- PET (8)
- positron emission tomography (7)
- prostate cancer (6)
- PRRT (4)
- RADS (4)
- prostate-specific membrane antigen (4)
- 18F-DCFPyL (3)
- 18F-FDG (3)
- Biologie (3)
Institute
- Theodor-Boveri-Institut für Biowissenschaften (32)
- Klinik und Poliklinik für Nuklearmedizin (23)
- Medizinische Klinik und Poliklinik II (9)
- Institut für Pharmazie und Lebensmittelchemie (4)
- Medizinische Klinik und Poliklinik I (4)
- Pathologisches Institut (3)
- Rudolf-Virchow-Zentrum (3)
- Deutsches Zentrum für Herzinsuffizienz (DZHI) (2)
- Institut für Anorganische Chemie (2)
- Institut für Rechtsmedizin (2)
Sonstige beteiligte Institutionen
Some decades ago it was noted by cytologists that within the interphase nucleus large portions of the transcriptionally ("genetically," in their terms) inactive chromosomal material are contained in aggregates of condensed chromatin, the "chromocenters," whereas transcriptionally active regions of chromosomes appear in a more dispersed form and are less intensely stained with DNA-directed staining procedures (Heitz 1929, 1932, 1956; Bauer 1933). The hypothesis that condensed chromatin is usually characterized by very low or no transcriptional activity, and that transcription occurs in loosely packed forms of chromatin (including, in most cells, the nucleolar chromatin) has received support from studies of ultrathin sections in the electron microscope and from the numerous attempts to separate transcriptionally active from inactive chromatin biochemically (for references, see Anderson et al. 1975; Berkowitz and Doty 1975; Krieg and Wells 1976; Rickwood and Birnie 1976; Gottesfeld 1977). Electron microscopic autoradiography has revealed that sites of RNA synthesis are enriched in dispersed chromatin regions located at the margins of condensed chromatin (Fakan and Bernhard 1971, 1973; Bouteille et al. 1974; Bachellerie et al. 1975) and are characterized by the occurrence of distinct granular and fibrillar ribonucleoprotein (RNP) structures, such as perichromatin granules and fibrils. The discovery that, in most eukaryotic nuclei, major parts of the chromatin are organized in the form of nucleosomes (Olins and Olins 1974; Kornberg 1974; Baldwin et al. 1975) has raised the question whether the same nucleosomal packing of DNA is also present in transcriptionally active chromatin strands. Recent detailed examination of the morphology of active and inactive chromatin involving a diversity of electron microscopic methods, particularly the spreading technique by Miller and coworkers (Miller and Beatty 1969; Miller and Bakken 1972), has indicated that the DNA of some actively transcribed regions is not packed into nucleosomal particles but is present in a rather extended form within a relatively thin (4-7 nm) chromatin fiber.
Heart failure is one of the growing causes of death especially in developed countries due to longer life expectancy. Although many pharmacological and instrumental therapeutic approaches have been introduced for prevention and treatment of heart failure, there are still limitations and challenges. Nuclear cardiology has experienced rapid growth in the last few decades, in particular the application of single photon emission computed tomography (SPECT) and positron emission tomography (PET), which allow non-invasive functional assessment of cardiac condition including neurohormonal systems involved in heart failure; its application has dramatically improved the capacity for fundamental research and clinical diagnosis. In this article, we review the current status of applying radionuclide technology in non-invasive imaging of neurohormonal system in the heart, especially focusing on the tracers that are currently available. A short discussion about disadvantages and perspectives is also included.
Both prostate-specific membrane antigen (PSMA)- and somatostatin receptor (SSTR)-targeted positron emission tomography (PET) imaging agents for staging and restaging of prostate carcinoma or neuroendocrine tumors, respectively, are seeing rapidly expanding use. In addition to diagnostic applications, both classes of radiotracers can be used to triage patients for theranostic endoradiotherapy. While interpreting PSMA- or SSTR-targeted PET/computed tomography (CT) scans, the reader has to be aware of certain pitfalls. Adding to the complexity of the interpretation of those imaging agents, both normal biodistribution, and also false-positive and -negative findings differ between PSMA- and SSTR-targeted PET radiotracers. Herein summarized under the umbrella term molecular imaging reporting and data systems (MI-RADS), two novel RADS classifications for PSMA- and SSTR-targeted PET imaging are described (PSMA- and SSTR-RADS). Both framework systems may contribute to increase the level of a reader’s confidence and to navigate the imaging interpreter through indeterminate lesions, so that appropriate workup for equivocal findings can be pursued. Notably, PSMA- and SSTR-RADS are structured in a reciprocal fashion, i.e. if the reader is familiar with one system, the other system can readily be applied as well. In the present review we will discuss the most common pitfalls on PSMA- and SSTR-targeted PET/CT, briefly introduce PSMA- and SSTR-RADS, and define a future role of the umbrella framework MI-RADS compared to other harmonization systems.
Purpose: The metabolically most active lesion in 2-deoxy-2-(\(^{18}\)F)fluoro-D-glucose (\(^{18}\)F-FDG) PET/CT can predict progression-free survival (PFS) in patients with medullary thyroid carcinoma (MTC) starting treatment with the tyrosine kinase inhibitor (TKI) vandetanib. However, this metric failed in overall survival (OS) prediction. In the present proof of concept study, we aimed to explore the prognostic value of intratumoral textural features (TF) as well as volumetric parameters (total lesion glycolysis, TLG) derived by pre-therapeutic \(^{18}\)F-FDG PET.
Methods: Eighteen patients with progressive MTC underwent baseline \(^{18}\)F-FDG PET/CT prior to and 3 months after vandetanib initiation. By manual segmentation of the tumor burden at baseline and follow-up PET, intratumoral TF and TLG were computed. The ability of TLG, imaging-based TF, and clinical parameters (including age, tumor marker doubling times, prior therapies and RET (rearranged during transfection) mutational status) for prediction of both PFS and OS were evaluated.
Results: The TF Complexity and the volumetric parameter TLG obtained at baseline prior to TKI initiation successfully differentiated between low- and high-risk patients. Complexity allocated 10/18 patients to the high-risk group with an OS of 3.3y (vs. low-risk group, OS=5.3y, 8/18, AUC=0.78, P=0.03). Baseline TLG designated 11/18 patients to the high-risk group (OS=3.5y vs. low-risk group, OS=5y, 7/18, AUC=0.83, P=0.005). The Hazard Ratio for cancer-related death was 6.1 for Complexity (TLG, 9.5). Among investigated clinical parameters, the age at initiation of TKI treatment reached significance for PFS prediction (P=0.02, OS, n.s.).
Conclusions: The TF Complexity and the volumetric parameter TLG are both independent parameters for OS prediction.
The aim of this study was to investigate if the biomarkers myelin basic protein (MBP) and neurofilament-H (NF-H) yielded informative value in forensic diagnostics when examining cadaveric cerebrospinal fluid (CSF) biochemically via an enzyme-linked immunosorbent assay (ELISA) and comparing the corresponding brain tissue in fatal traumatic brain injury (TBI) autopsy cases by immunocytochemistry versus immunohistochemistry. In 21 trauma and 19 control cases, CSF was collected semi-sterile after suboccipital puncture and brain specimens after preparation. The CSF MBP (p = 0.006) and NF-H (p = 0.0002) levels after TBI were significantly higher than those in cardiovascular controls. Immunohistochemical staining against MBP and against NF-H was performed on cortical and subcortical samples from also biochemically investigated cases (5 TBI cases/5 controls). Compared to the controls, the TBI cases showed a visually reduced staining reaction against MBP or repeatedly ruptured neurofilaments against NF-H. Immunocytochemical tests showed MBP-positive phagocytizing macrophages in CSF with a survival time of > 24 h. In addition, numerous TMEM119-positive microglia could be detected with different degrees of staining intensity in the CSF of trauma cases. As a result, we were able to document that elevated levels of MBP and NF-H in the CSF should be considered as useful neuroinjury biomarkers of traumatic brain injury.
A General Synthetic Route to NHC‐Phosphinidenes: NHC‐mediated Dehydrogenation of Primary Phosphines
(2021)
The dehydrocoupling of primary phosphines with N-heterocyclic carbenes (NHCs) to yield NHC-phosphinidenes is reported. The reaction of two equivalents of the NHCs Me\(_2\)Im (1,3-dimethylimidazolin-2-ylidene), Me\(_4\)Im (1,3,4,5-tetramethylimidazolin-2-ylidene), iPr\(_2\)Im (1,3-di-iso-propylimidazolin-2-ylidene) and Mes\(_2\)Im (2,4,6-trimethylphenylimidazolin-2-ylidene) with PhPH\(_2\) and MesPH\(_2\) led to the NHC stabilized phosphinidenes (NHC)PAr: (iPr\(_2\)Im)PPh (1), (Mes\(_2\)Im)PPh (2), (Me\(_4\)Im)PPh (3), (Mes\(_2\)Im)PMes (4), (Me\(_2\)Im)PMes (5), (Me\(_4\)Im)PMes (6) and (iPr\(_2\)Im)PMes (7). The reaction of tBuPH\(_2\) with two equivalents of the NHCs afforded the corresponding NHC stabilized parent phosphinidenes (NHC)PH: (iPr\(_2\)Im)PH (8), (Mes\(_2\)Im)PH (9) and (Me\(_4\)Im)PH (10). Reaction of 1 with oxygen and sulfur led to isolation of iPr\(_2\)Im-P(O)\(_2\)Ph (11) and iPr\(_2\)Im-P(S)\(_2\)Ph (12), whereas the reaction with elemental selenium and tellurium gave (NHC)PPh cleavage with formation of (iPr\(_2\)Im)Se (13), iPr\(_2\)ImTe (14) and different cyclo-oligophosphines. Furthermore, the complexes [{(iPr\(_2\)Im)PPh}W(CO)\(_5\)] (15), [Co(CO)\(_2\)(NO){(iPr\(_2\)Im)PPh}] (16) and [(η\(^5\)-C\(_5\)Me\(_2\))Co(η\(^2\)-C\(_2\)H\(_4\)){(iPr\(_2\)Im)PPh}] (17) have been prepared starting from 1 and a suitable transition metal complex precursor. The complexes 16 and 17 decompose in solution upon heating to ca. 80 °C to yield the NHC complexes [Co(iPr\(_2\)Im)(CO)\(_2\)(NO)] and [(η\(^5\)-C\(_5\)Me\(_5\))Co(iPr\(_2\)Im)(η\(^2\)-C\(_2\)H\(_4\))] with formation of cyclo-oligophosphines. The reaction of 1 with [Ni(COD)\(_2\)] afforded the diphosphene complex [Ni(iPr\(_2\)Im)\(_2\)(trans-PhP=PPh)] 18.
Purpose: A new PET radiotracer \(^{18}\)F-AF78 showing great potential for clinical application has been reported recently. It belongs to a new generation of phenethylguanidine-based norepinephrine transporter (NET)-targeting radiotracers. Although many efforts have been made to develop NET inhibitors as antidepressants, systemic investigations of the structure–activity relationships (SARs) of NET-targeting radiotracers have rarely been performed. Methods: Without changing the phenethylguanidine pharmacophore and 3-fluoropropyl moiety that is crucial for easy labeling, six new analogs of \(^{18}\)F-AF78 with different meta-substituents on the benzene-ring were synthesized and evaluated in a competitive cellular uptake assay and in in vivo animal experiments in rats. Computational modeling of these tracers was established to quantitatively rationalize the interaction between the radiotracers and NET. Results: Using non-radiolabeled reference compounds, a competitive cellular uptake assay showed a decrease in NET-transporting affinity from meta-fluorine to iodine (0.42 and 6.51 µM, respectively), with meta-OH being the least active (22.67 µM). Furthermore, in vivo animal studies with radioisotopes showed that heart-to-blood ratios agreed with the cellular experiments, with AF78(F) exhibiting the highest cardiac uptake. This result correlates positively with the electronegativity rather than the atomic radius of the meta-substituent. Computational modeling studies revealed a crucial influence of halogen substituents on the radiotracer–NET interaction, whereby a T-shaped π–π stacking interaction between the benzene-ring of the tracer and the amino acid residues surrounding the NET binding site made major contributions to the different affinities, in accordance with the pharmacological data. Conclusion: The SARs were characterized by in vitro and in vivo evaluation, and computational modeling quantitatively rationalized the interaction between radiotracers and the NET binding site. These findings pave the way for further evaluation in different species and underline the potential of AF78(F) for clinical application, e.g., cardiac innervation imaging or molecular imaging of neuroendocrine tumors.
Background: Radiolabeled agents that are substrates for the norepinephrine transporter (NET) can be used to quantify cardiac sympathetic nervous conditions and have been demonstrated to identify high-risk congestive heart failure (HF) patients prone to arrhythmic events. We aimed to fully characterize the kinetic profile of the novel \(^{18}\)F-labeled NET probe AF78 for PET imaging of the cardiac sympathetic nervous system (SNS) among various species.
Methods: \(^{18}\)F-AF78 was compared to norepinephrine (NE) and established SNS radiotracers by employing in vitro cell assays, followed by an in vivo PET imaging approach with healthy rats, rabbits and nonhuman primates (NHPs). Additionally, chase protocols were performed in NHPs with NET inhibitor desipramine (DMI) and the NE releasing stimulator tyramine (TYR) to investigate retention kinetics in cardiac SNS.
Results: Relative to other SNS radiotracers, 18F-AF78 showed higher transport affinity via NET in a cell-based competitive uptake assay (IC\(^{50}\) 0.42 ± 0.14 µM), almost identical to that of NE (IC\(^{50}\), 0.50 ± 0.16 µM, n.s.). In rabbits and NHPs, initial cardiac uptake was significantly reduced by NET inhibition. Furthermore, cardiac tracer retention was not affected by a DMI chase protocol but was markedly reduced by intermittent TYR chase, thereby suggesting that \(^{18}\)F-AF78 is stored and can be released via the synaptic vesicular turnover process. Computational modeling hypothesized the formation of a T-shaped π-π stacking at the binding site, suggesting a rationale for the high affinity of \(^{18}\)F-AF78.
Conclusion: \(^{18}\)F-AF78 demonstrated high in vitro NET affinity and advantageous in vivo radiotracer kinetics across various species, indicating that \(^{18}\)F-AF78 is an SNS imaging agent with strong potential to guide specific interventions in cardiovascular medicine.