scholarly journals Measurement of Bmax and Kd with the Glycine Transporter 1 Radiotracer 18F-MK6577 using a Novel Multi-Infusion Paradigm

2015 ◽  
Vol 35 (12) ◽  
pp. 2001-2009 ◽  
Author(s):  
Yan Xia ◽  
Ming-Qiang Zheng ◽  
Daniel Holden ◽  
Shu-fei Lin ◽  
Michael Kapinos ◽  
...  
Keyword(s):  
Rank Order ◽  
Target Concentration ◽  
Glycine Transporter 1 ◽  
Glycine Transporter ◽  
Positron Emission ◽  
Fitting Method ◽  
The Brain

Glycine is a co-agonist of glutamate at the NMDA receptor. Glycine transporter 1 (GlyT1) inhibitors are reported to be potential therapeutic agents for schizophrenia. 18F-MK6577 is a new positron emission tomography (PET) radiotracer useful for imaging brain GlyT1 and its occupancy in humans. We devised a novel multi-infusion paradigm of radiolabeled and unlabeled compound and an iterative linear/nonlinear alternating fitting method to allow for the determination of in vivo affinity ( Kd) and target concentration ( Bmax) images, constraining Kd to be uniform across the brain. This paradigm was tested with 18F-MK6577 in baboons. Voxel-based analysis produced high quality Bmax images and reliable Kd estimates, and also suggested that the nondisplaceable distribution volume ( VND) is not uniform throughout the brain. In vivo GlyT1 Kd was estimated to be 1.87 nmol/L for 18F-MK6577, and the rank order of GlyT1 distribution measured in the baboon brain was: high in the brainstem (133 nmol/L), medium in the cerebellum (83 nmol/L), and low in the cortex (30 nmol/L). These in vivo Kd and Bmax values agreed well with those determined in vitro, thus validating our novel multi-infusion approach.

scholarly journals Synthesis and In Vitro Evaluation of 8-Pyridinyl-Substituted Benzo[e]imidazo[2,1-c][1,2,4]triazines as Phosphodiesterase 2A Inhibitors

Molecules ◽  
2019 ◽  
Vol 24 (15) ◽  
pp. 2791 ◽  
Author(s):  
Ritawidya ◽  
Ludwig ◽  
Briel ◽  
Brust ◽  
Scheunemann
Keyword(s):  
Potent Inhibitor ◽  
Liver Microsomes ◽  
Emission Tomography ◽  
Inhibitory Potency ◽  
Positron Emission ◽  
Neuropsychiatric Diseases ◽  
Further Development ◽  
The Brain

Phosphodiesterase 2A (PDE2A) is highly expressed in distinct areas of the brain, which are known to be related to neuropsychiatric diseases. The development of suitable PDE2A tracers for Positron Emission Tomography (PET) would permit the in vivo imaging of the PDE2A and evaluation of disease-mediated alterations of its expression. A series of novel fluorinated PDE2A inhibitors on the basis of a Benzoimidazotriazine (BIT) scaffold was prepared leading to a prospective inhibitor for further development of a PDE2A PET imaging agent. BIT derivatives (BIT1–9) were obtained by a seven-step synthesis route, and their inhibitory potency towards PDE2A and selectivity over other PDEs were evaluated. BIT1 demonstrated much higher inhibition than other BIT derivatives (82.9% inhibition of PDE2A at 10 nM). BIT1 displayed an IC50 for PDE2A of 3.33 nM with 16-fold selectivity over PDE10A. This finding revealed that a derivative bearing both a 2-fluoro-pyridin-4-yl and 2-chloro-5-methoxy-phenyl unit at the 8- and 1-position, respectively, appeared to be the most potent inhibitor. In vitro studies of BIT1 using mouse liver microsomes (MLM) disclosed BIT1 as a suitable ligand for 18F-labeling. Nevertheless, future in vivo metabolism studies are required.

In vivo neuropharmacology of schizophrenia

1999 ◽  
Vol 174 (S38) ◽  
pp. 23-33 ◽  
Author(s):  
V. Bigliani ◽  
L. S. Pilowsky
Keyword(s):  
Single Photon ◽  
Photon Emission ◽  
Emission Tomography ◽  
Binding Assays ◽  
Single Photon Emission ◽  
Positron Emission ◽  
The Brain ◽  
Major Target

Since the introduction of chlorpromazine in the 1950s, followed by the discovery (with in vitro receptor binding assays), in the mid-1970s, that antipsychotic drugs block a subtype of dopamine receptor (D2/D2-like) (Creese et al, 1976) and that affinity for these receptors appears to correlate directly with clinical potency for antipsychotics (Peroutka & Synder, 1980), the study of neurotransmitters and receptors has been a major target of schizophrenia research (Owens, 1996). In 1983, the first visualisation, by positron emission tomography (PET), of the binding of D2 dopamine receptors in the brain of a living human subject was reported (Wagner et al, 1983). Following this, the number of research studies using PET and single photon emission tomography (SPET) has increased enormously.

scholarly journals Preclinical characterization of [18F]T-008, a novel PET imaging radioligand for cholesterol 24-hydroxylase

2021 ◽  
Author(s):  
Tatsuki Koike ◽  
Cristian C. Constantinescu ◽  
Shuhei Ikeda ◽  
Toshiya Nishi ◽  
Eiji Sunahara ◽  
...  
Keyword(s):  
Mouse Brain ◽  
Pet Imaging ◽  
Rank Order ◽  
Cholesterol Homeostasis ◽  
Dependent Manner ◽  
Wild Type ◽  
In Vivo Evaluation ◽  
The Brain

Abstract Purpose Cholesterol 24-hydroxylase (CH24H) is a brain-specific enzyme that plays a major role in brain cholesterol homeostasis by converting cholesterol into 24S-hydroxycholesterol. The selective CH24H inhibitor soticlestat (TAK-935) is being pursued as a drug for treatment of seizures in developmental and epileptic encephalopathies. Herein, we describe the successful discovery and the preclinical validation of the novel radiolabeled CH24H ligand (3-[18F]fluoroazetidin-1-yl){1-[4-(4-fluorophenyl)pyrimidin-5-yl]piperidin-4-yl}methanone ([18F]T-008) and its tritiated analog, [3H]T-008. Methods In vitro autoradiography (ARG) studies in the CH24H wild-type (WT) and knockout (KO) mouse brain sections were conducted using [3H]T-008. PET imaging was conducted in two adult rhesus macaques using [18F]T-008. Each macaque received two test–retest baseline scans and a series of two blocking doses of soticlestat administered prior to [18F]T-008 to determine the CH24H enzyme occupancy. PET data were analyzed with Logan graphical analysis using plasma input. A Lassen plot was applied to estimate CH24H enzyme occupancy by soticlestat. Results In ARG studies, binding of [3H]T-008 was specific to CH24H in the mouse brain sections, which was not observed in CH24H KO or in wild-type mice after pretreatment with soticlestat. In rhesus PET studies, the rank order of [18F]T-008 uptake was striatum > cortical regions > cerebellum, which was consistent with CH24H distribution in the brain. Pre-blocking with soticlestat reduced the maximum uptake and increased the washout in all brain regions in a dose-dependent manner. Calculated global occupancy values for soticlestat at a dose of 0.89 mg/kg were 97–98%, indicating maximum occupancy. Conclusion The preclinical in vitro and in vivo evaluation of labeled T-008 demonstrates that [18F]T-008 is suitable for imaging CH24H in the brain and warrants further studies in humans. Graphical abstract

scholarly journals Determination of [11C]PBR28 Binding Potential in vivo: A First Human TSPO Blocking Study

2014 ◽  
Vol 34 (6) ◽  
pp. 989-994 ◽  
Author(s):  
David R Owen ◽  
Qi Guo ◽  
Nicola J Kalk ◽  
Alessandro Colasanti ◽  
Dimitra Kalogiannopoulou ◽  
...  
Keyword(s):  
Volume Of Distribution ◽  
Translocator Protein ◽  
Binding Potential ◽  
Healthy Human ◽  
Positron Emission ◽  
Dose Dependent ◽  
In Vitro Data

Positron emission tomography (PET) targeting the 18 kDa translocator protein (TSPO) is used to quantify neuroinflammation. Translocator protein is expressed throughout the brain, and therefore a classical reference region approach cannot be used to estimate binding potential ( BP ND). Here, we used blockade of the TSPO radioligand [11C]PBR28 with the TSPO ligand XBD173, to determine the non-displaceable volume of distribution ( V ND), and hence estimate the BP ND. A total of 26 healthy volunteers, 16 high-affinity binders (HABs) and 10 mixed affinity binders (MABs) underwent a [11C]PBR28 PET scan with arterial sampling. Six of the HABs received oral XBD173 (10 to 90 mg), 2 hours before a repeat scan. In XBD173-dosed subjects, V ND was estimated via the occupancy plot. Values of BP ND for all subjects were calculated using this V ND estimate. Total volume of distribution ( V T) of MABs (2.94 ± 0.31) was lower than V T of HABs (4.33 ± 0.29) ( P<0.005). There was dose-dependent occupancy of TSPO by XBD173 (ED50 = 0.34 ± 0.13 mg/kg). The occupancy plot provided a V ND estimate of 1.98 (1.69, 2.26). Based on these V ND estimates, BP ND for HABs is approximately twice that of MABs, consistent with predictions from in vitro data. Our estimates of [11C]PBR28 V ND and hence BP ND in the healthy human brain are consistent with in vitro predictions. XBD173 blockade provides a practical means of estimating V ND for TSPO targeting radioligands.

Tissue-specific differences in the compartmentalization of rat nuclear triiodothyronine receptors

1990 ◽  
Vol 122 (2) ◽  
pp. 181-190 ◽  
Author(s):  
Charles P. Barsano ◽  
Zafar Iqbal ◽  
Gordon L. Pullen ◽  
B. Elena Muñoz ◽  
Sant P. Singh
Keyword(s):  
Nuclear Receptors ◽  
Rank Order ◽  
Glass Wool ◽  
Association Constants ◽  
Small Samples ◽  
Nuclear Compartment ◽  
Hormone Responsiveness

Abstract In addition to the recognized rat liver nuclear T3 receptor extractable with hypertonic salt, recent studies have described nucleoplasmic receptors extractable with isotonic KCl and salt-resistant receptors localized to the nuclear matrix. A method was developed for the determination of intra-nuclear receptor distribution 1in small samples of nuclei dispersed within glass wool matrices. After in vitro labelling with 6 nmol/l [125I]T3, dispersed nuclei were sequentially extracted with 0.15 mol/l KCl (yielding nucleoplasmic receptors), 0.4 mol/l KCl, and 2 mol/l KCl (the latter two concentrations yelding hypertonic salt-extractable receptors). The salt-resistant receptors were retained within the glass wool columns. The intra-nuclear distribution of in vivo labelled receptors was very similar to that obtained by in vitro labelling. The equilibrium association constants for L-T3 binding among the receptor pools ranged from 0.6 × 109 to 1.0 × 109 l/mol. The distribution of total nuclear receptors within each nuclear compartment was (percentage of nucleoplasmic, hypertonic salt-extractable, and salt-resistant receptors): Cerebrum: 23.6, 52.2, 24.2; Liver: 25.2, 57.2, 17.5; Kidney: 45.9, 33.5, 20.6; Testis: 65.5, 14.7, 19.7; and Spleen: 66.7, 18.7, 14.6. The rank order of percentage of hypertonic salt-extractable receptors approximates the rank order of thyroid hormone-responsiveness by traditional criteria. The inverse is true for the percentage of nucleoplasmic receptors. The percentage of salt-resistant receptors was very similar in all of the tissues.

scholarly journals Functional expression of SGLTs in rat brain

2010 ◽  
Vol 299 (6) ◽  
pp. C1277-C1284 ◽  
Author(s):  
Amy S. Yu ◽  
Bruce A. Hirayama ◽  
Gerald Timbol ◽  
Jie Liu ◽  
Ernest Basarah ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Brain Slices ◽  
Glucose Transporters ◽  
Functional Expression ◽  
Positron Emission ◽  
Health And Disease ◽  
Pass Through ◽  
The Brain

This work provides evidence of previously unrecognized uptake of glucose via sodium-coupled glucose transporters (SGLTs) in specific regions of the brain. The current understanding of functional glucose utilization in brain is largely based on studies using positron emission tomography (PET) with the glucose tracer 2-deoxy-2-[F-18]fluoro-d-glucose (2-FDG). However, 2-FDG is only a good substrate for facilitated-glucose transporters (GLUTs), not for SGLTs. Thus, glucose accumulation measured by 2-FDG omits the role of SGLTs. We designed and synthesized two high-affinity tracers: one, α-methyl-4-[F-18]fluoro-4-deoxy-d-glucopyranoside (Me-4FDG), is a highly specific SGLT substrate and not transported by GLUTs; the other one, 4-[F-18]fluoro-4-deoxy-d-glucose (4-FDG), is transported by both SGLTs and GLUTs and will pass through the blood brain barrier (BBB). In vitro Me-4FDG autoradiography was used to map the distribution of uptake by functional SGLTs in brain slices with a comparable result from in vitro 4-FDG autoradiography. Immunohistochemical assays showed that uptake was consistent with the distribution of SGLT protein. Ex vivo 4-FDG autoradiography showed that SGLTs in these areas are functionally active in the normal in vivo brain. The results establish that SGLTs are a normal part of the physiology of specific areas of the brain, including hippocampus, amygdala, hypothalamus, and cerebral cortices. 4-FDG PET imaging also established that this BBB-permeable SGLT tracer now offers a functional imaging approach in humans to assess regulation of SGLT activity in health and disease.

Effect of pH and inhibitors on beta-amyloid fibril assembly

1996 ◽  
Vol 54 ◽  
pp. 752-753
Author(s):  
Beverly E. Maleeff ◽  
Timothy K. Hart ◽  
Stephen J. Wood ◽  
Ronald Wetzel
Keyword(s):  
Amyloid Fibril ◽  
Peptide Fragment ◽  
Hydrophobic Peptides ◽  
Amyloid Fibril Formation ◽  
Effects Of Ph ◽  
Severity Of The Disease ◽  
Kinetics Of ◽  
The Brain

Alzheimer's disease is characterized post-mortem in part by abnormal extracellular neuritic plaques found in brain tissue. There appears to be a correlation between the severity of Alzheimer's dementia in vivo and the number of plaques found in particular areas of the brain. These plaques are known to be the deposition sites of fibrils of the protein β-amyloid. It is thought that if the assembly of these plaques could be inhibited, the severity of the disease would be decreased. The peptide fragment Aβ, a precursor of the p-amyloid protein, has a 40 amino acid sequence, and has been shown to be toxic to neuronal cells in culture after an aging process of several days. This toxicity corresponds to the kinetics of in vitro amyloid fibril formation. In this study, we report the biochemical and ultrastructural effects of pH and the inhibitory agent hexadecyl-N-methylpiperidinium (HMP) bromide, one of a class of ionic micellar detergents known to be capable of solubilizing hydrophobic peptides, on the in vitro assembly of the peptide fragment Aβ.

A Molecular Approach to Immunoscintigraphy: A Study of the T-Antigen Conformation on the Surface of Tumors

1987 ◽  
Vol 26 (01) ◽  
pp. 1-6 ◽  
Author(s):  
S. Selvaraj ◽  
M. R. Suresh ◽  
G. McLean ◽  
D. Willans ◽  
C. Turner ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Tumor Cell ◽  
T Antigen ◽  
Human Carcinomas ◽  
Animal Tumor ◽  
Synthetic Antigens

The role of glycoconjugates in tumor cell differentiation has been well documented. We have examined the expression of the two anomers of the Thomsen-Friedenreich antigen on the surface of human, canine and murine tumor cell membranes both in vitro and in vivo. This has been accomplished through the synthesis of the disaccharide terminal residues in both a and ß configuration. Both entities were used to generate murine monoclonal antibodies which recognized the carbohydrate determinants. The determination of fine specificities of these antibodies was effected by means of cellular uptake, immunohistopathology and immunoscintigraphy. Examination of pathological specimens of human and canine tumor tissue indicated that the expressed antigen was in the β configuration. More than 89% of all human carcinomas tested expressed the antigen in the above anomeric form. The combination of synthetic antigens and monoclonal antibodies raised specifically against them provide us with invaluable tools for the study of tumor marker expression in humans and their respective animal tumor models.

Storage of Human Blood Platelets

1974 ◽  
Vol 32 (02/03) ◽  
pp. 405-416 ◽  
Author(s):  
M. R Hardeman ◽  
Carina J L. Heynens
Keyword(s):  
Storage Temperature ◽  
Platelet Rich Plasma ◽  
Blood Platelets ◽  
Storage Period ◽  
Serotonin Uptake ◽  
Hypotonic Shock ◽  
Glycolytic Intermediates

SummaryStorage experiments were performed at 4°, 25° and 37° C with platelet-rich plasma under sterile conditions. In some experiments also the effect of storing platelets at 4° C in whole blood was investigated.Before, during and after three days of storage, the platelets were tested at 37° C for their serotonin uptake and response to hypotonic shock. In addition some glycolytic intermediates were determined.A fair correlation was noticed between the serotonin uptake and hypotonic shock experiments. Both parameters were best maintained at 25° C. Also platelet counting, performed after the storage period, indicated 25° C as the best storage temperature. Determination of glycolytic intermediates did not justify any conclusion regarding the optimal storage temperature. Of the various anticoagulants studied, ACD and heparin gave the best results as to the serotonin uptake and hypotonic shock response, either with fresh or stored platelets. The use of EDTA resulted in the lowest activity, especially after storage.The results of these storage experiments in vitro, correspond well with those in vivo reported in the literature.

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