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BMJ Open Diabetes Research & Care Apr 2021Glucagon-like peptide-1 (GLP-1) increases insulin secretion from pancreatic beta-cells and GLP-1 receptor (GLP-1R) agonists are widely used as treatment for type 2...
INTRODUCTION
Glucagon-like peptide-1 (GLP-1) increases insulin secretion from pancreatic beta-cells and GLP-1 receptor (GLP-1R) agonists are widely used as treatment for type 2 diabetes mellitus. Studying occupancy of the GLP-1R in various tissues is challenging due to lack of quantitative, repeatable assessments of GLP-1R density. The present study aimed to describe the quantitative distribution of GLP-1Rs and occupancy by endogenous GLP-1 during oral glucose tolerance test (OGTT) in pigs, a species that is used in biomedical research to model humans.
RESEARCH DESIGN AND METHODS
GLP-1R distribution and occupancy were measured in pancreas and gastrointestinal tract by ex vivo autoradiography using the GLP-1R-specific radioligand Lu-exendin-4 in two groups of pigs, control or bottle-fed an oral glucose load. Positron emission tomography (PET) data from pigs injected with Ga-exendin-4 in a previous study were used to retrieve data on biodistribution of GLP-1R in the gastrointestinal tract.
RESULTS
High homogenous uptake of Lu-exendin-4 was found in pancreas, and even higher uptake in areas of duodenum. Low uptake of Lu-exendin-4 was found in stomach, jejunum, ileum and colon. During OGTT, there was no increase in plasma GLP-1 concentrations and occupancy of GLP-1Rs was low. The ex vivo autoradiography results were highly consistent with to the biodistribution of Ga-exendin-4 in pigs scanned by PET.
CONCLUSION
We identified areas with similarities as well as important differences regarding GLP-1R distribution and occupancy in pigs compared with humans. First, there was strong ligand binding in the exocrine pancreas in islets. Second, GLP-1 secretion during OGTT is minimal and GLP-1 might not be an important incretin in pigs under physiological conditions. These findings offer new insights on the relevance of porcine diabetes models.
Topics: Animals; Autoradiography; Diabetes Mellitus, Type 2; Gastrointestinal Tract; Glucagon-Like Peptide 1; Pancreas; Swine; Tissue Distribution
PubMed: 33903116
DOI: 10.1136/bmjdrc-2020-002083 -
Journal of Nuclear Medicine : Official... Oct 2011Histopathologic validation of a PET tracer requires assessment of colocalization of the tracer with its intended biologic target. Using thin tissue section...
UNLABELLED
Histopathologic validation of a PET tracer requires assessment of colocalization of the tracer with its intended biologic target. Using thin tissue section autoradiography, it is possible to visualize the spatial distribution of the PET tracer uptake and compare it with the distribution of the intended biologic target (as visualized with immunohistochemistry). The purpose of this study was to develop and evaluate an objective methodology for deformable coregistration of autoradiography and microscopy images acquired from a set of sequential tissue sections.
METHODS
Tumor-bearing animals were injected with 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT), (14)C-FDG, and other markers of tumor microenvironment including Hoechst 33342 (blood-flow surrogate). After sacrifice, tumors were excised, frozen, and sectioned. Multiple stacks of sequential 8 μm sections were collected from each tumor. From each stack, the middle (reference) sections were used to obtain images of (18)F-FLT and (14)C-FDG uptake distributions using dual-tracer autoradiography. Sections adjacent to the reference were used to acquire all histopathologic data (e.g., images of cell proliferation, hematoxylin and eosin). Hoechst images were acquired from all sections. To correct for deformations and misalignments induced by tissue processing and image acquisition, the Hoechst image of each nonreference section was deformably registered to the reference Hoechst image. This transformation was then applied to all images acquired from the same tissue section. In this way, all microscopy images were registered to the reference Hoechst image. The Hoechst-to-autoradiography image registration was done using rigid point-set registration based on external markers visible in both images.
RESULTS
The mean error of Hoechst to (18)F-FLT autoradiography registration (both images acquired from the same section) was 30.8 ± 20.1 μm. The error of Hoechst-based deformable registration of histopathologic images (acquired from sequential tissue sections) was 23.1 ± 17.9 μm. Total error of registration of autoradiography images to the histopathologic images acquired from adjacent sections was evaluated at 44.9 μm. This coregistration precision supersedes current rigid registration methods with reported errors of 100-200 μm.
CONCLUSION
Deformable registration of autoradiography and histopathology images acquired from sequential sections is feasible and accurate when performed using corresponding Hoechst images.
Topics: Animals; Autoradiography; Carbon Radioisotopes; Cell Line, Tumor; Dideoxynucleosides; Fluorodeoxyglucose F18; Humans; Immunohistochemistry; Male; Mice; Mice, Nude; Neoplasms, Experimental; Positron-Emission Tomography; Radiographic Image Interpretation, Computer-Assisted; Radiopharmaceuticals; Transplantation, Heterologous; Tumor Microenvironment
PubMed: 21865287
DOI: 10.2967/jnumed.111.091595 -
American Journal of Primatology Jan 2016While osteopenia (OPE) and osteoporosis (OPO) have been studied in various species of aging nonhuman primates and extensively in ovariectomized rhesus and cynomolgus...
While osteopenia (OPE) and osteoporosis (OPO) have been studied in various species of aging nonhuman primates and extensively in ovariectomized rhesus and cynomolgus macaques, there is virtually no information on the effects of castration on the skeleton of male nonhuman primates. Most information on castrated male primates comes from a few studies on the skeletons of eunuchs. This report used a subset of the Caribbean Primate Research Center's (CPRC) Cayo Santiago (CS) rhesus macaque skeletal collection to qualitatively and quantitatively compare the bone mineral density (BMD) of castrated and age-matched intact males and, thereby, determine the long-term effects of castration (orchidectomy) on bone. Lumbar vertebrae, femora, and crania were evaluated using dual-energy X-ray absorptiometry (DEXA or DXA) and digital radiography augmented, when fresh tissues were available, with autoradiography and histology. Results confirmed physical examinations of long bones that castration causes changes in the skeleton of male rhesus macaques similar to those found in eunuchs, including OPE and OPO of the vertebrae and femora, thinning of the skull, and vertebral fractures and kyphosis of the spine more severe than that caused by normal aging alone. Also like eunuchs, some castrated CS male rhesus monkeys had a longer life span than intact males or females. Based on these results and the effects of castration on other tissues and organs of eunuchs, on behavior, hormone profiles and possibly on cognition and visual perception of human and nonhuman primates, and other mammals, castrated male rhesus macaques should be used with caution for laboratory studies and should be considered a separate category from intact males. Despite these caveats, the castrated male rhesus macaque should make an excellent animal model in which to test hormone replacement therapies for boys and men orchidectomized for testicular and prostate cancer.
Topics: Absorptiometry, Photon; Animals; Autoradiography; Bone Density; Femur; Lumbar Vertebrae; Macaca mulatta; Male; Orchiectomy; Puerto Rico; Radiographic Image Enhancement; Skull
PubMed: 25771746
DOI: 10.1002/ajp.22399 -
Journal of Neuroinflammation Jun 2016Traumatic brain injury (TBI) is a major cause of death and disability. Neuroinflammation contributes to acute damage after TBI and modulates long-term evolution of...
BACKGROUND
Traumatic brain injury (TBI) is a major cause of death and disability. Neuroinflammation contributes to acute damage after TBI and modulates long-term evolution of degenerative and regenerative responses to injury. The aim of the present study was to evaluate the relationship of microglia activation to trauma severity, brain energy metabolism, and cellular reactions to injury in a mouse closed head injury model using combined in vivo PET imaging, ex vivo autoradiography, and immunohistochemistry.
METHODS
A weight-drop closed head injury model was used to produce a mixed diffuse and focal TBI or a purely diffuse mild TBI (mTBI) in C57BL6 mice. Lesion severity was determined by evaluating histological damage and functional outcome using a standardized neuroscore (NSS), gliosis, and axonal injury by immunohistochemistry. Repeated intra-individual in vivo μPET imaging with the specific 18-kDa translocator protein (TSPO) radioligand [(18)F]DPA-714 was performed on day 1, 7, and 16 and [(18)F]FDG-μPET imaging for energy metabolism on days 2-5 after trauma using freshly synthesized radiotracers. Immediately after [(18)F]DPA-714-μPET imaging on days 7 and 16, cellular identity of the [(18)F]DPA-714 uptake was confirmed by exposing freshly cut cryosections to film autoradiography and successive immunostaining with antibodies against the microglia/macrophage marker IBA-1.
RESULTS
Functional outcome correlated with focal brain lesions, gliosis, and axonal injury. [(18)F]DPA-714-μPET showed increased radiotracer uptake in focal brain lesions on days 7 and 16 after TBI and correlated with reduced cerebral [(18)F]FDG uptake on days 2-5, with functional outcome and number of IBA-1 positive cells on day 7. In autoradiography, [(18)F]DPA-714 uptake co-localized with areas of IBA1-positive staining and correlated strongly with both NSS and the number of IBA1-positive cells, gliosis, and axonal injury. After mTBI, numbers of IBA-1 positive cells with microglial morphology increased in both brain hemispheres; however, uptake of [(18)F]DPA-714 was not increased in autoradiography or in μPET imaging.
CONCLUSIONS
[(18)F]DPA-714 uptake in μPET/autoradiography correlates with trauma severity, brain metabolic deficits, and microglia activation after closed head TBI.
Topics: Animals; Autoradiography; Fluorine Radioisotopes; Fluorodeoxyglucose F18; Head Injuries, Closed; Male; Mice; Mice, Inbred C57BL; Microglia; Positron-Emission Tomography
PubMed: 27266706
DOI: 10.1186/s12974-016-0604-9 -
Autoradiography on deparaffinized tissue sections - A feasibility study with Ga-labeled PET-tracers.Applied Radiation and Isotopes :... Nov 2022Tissue available for retrospective research questions is often already paraffin-embedded for better preservation. However, in vitro autoradiography (AURA) is normally...
Tissue available for retrospective research questions is often already paraffin-embedded for better preservation. However, in vitro autoradiography (AURA) is normally performed on cryopreserved tissue sections. We hypothesized a) that it would also be feasible with deparaffinized tissue sections, enabling the use of human paraffin-embedded tissue for in vitro AURA and b) that the results would be comparable to those obtained with corresponding cryosections. For that purpose, the clinically relevant oncological targets CXCR4, SSTR and PSMA were evaluated. In vitro AURA on deparaffinized tissue sections was feasible, but only with the two receptor ligands [Ga]Ga-PentixaFor and [Ga]Ga-DOTANOC. [Ga]Ga-PSMA-11 did not show any binding on deparaffinized tissue sections, suggesting that native tissue is required for an interaction between this inhibitor and the enzyme.
Topics: Autoradiography; Feasibility Studies; Gallium Radioisotopes; Humans; Positron-Emission Tomography; Retrospective Studies
PubMed: 36030760
DOI: 10.1016/j.apradiso.2022.110425 -
ACS Chemical Neuroscience Mar 2021Microglia play a role in several central nervous system (CNS) diseases and are a highly sought target for positron emission tomography (PET) imaging and therapeutic...
Microglia play a role in several central nervous system (CNS) diseases and are a highly sought target for positron emission tomography (PET) imaging and therapeutic intervention. 5-Cyano--(4-(4-[C]methylpiperazin-1-yl)-2-(piperidin-1-yl)phenyl)furan-2-carboxamide ([C]CPPC) is a radiopharmaceutical designed to selectively target microglia macrophage colony stimulating factor-1 receptor (CSF-1R) in the CNS. Herein, we report the first preclinical evaluation of [H]CPPC using radioligand binding methods for the evaluation of putative CSF-1R inhibitors in rodent models of neuroinflammation. The distribution of [H]CPPC by autoradiography did not align with 18 kDa translocator protein (TSPO) distribution using [H]PBR28 and IBA-1 staining for microglia. In the CNS, [H]CPPC had considerable nonspecific binding, as indicated by a low displacement of the tritiated ligand by unlabeled CPPC and the known CSF1R inhibitors BLZ-945 and PLX3397. Spleen was identified as a tissue that provided an adequate signal-to-noise ratio to enable screening with [H]CPPC and a library of 20 novel PLX3397 derivatives. However, unlabeled CPPC lacked selectivity and showed off-target binding to a substantial number of kinase targets (204 out of 403 tested) at a concentration relevant to radioligand binding assays (10 μM). These findings suggest that, while [H]CPPC may have utility as a radioligand tool for the evaluation of peripheral targets and screening of CSF-1R inhibitors, it may have limited utility as an CNS imaging probe on the basis of the current evaluation.
Topics: Animals; Autoradiography; Microglia; Positron-Emission Tomography; Radiopharmaceuticals; Receptor Protein-Tyrosine Kinases; Rodentia
PubMed: 33667059
DOI: 10.1021/acschemneuro.0c00802 -
Scientific Reports Oct 2022Targeted radiopharmaceutical therapy with alpha-particle emitters (αRPT) is advantageous in cancer treatment because the short range and high local energy deposition of...
Targeted radiopharmaceutical therapy with alpha-particle emitters (αRPT) is advantageous in cancer treatment because the short range and high local energy deposition of alpha particles enable precise radiation delivery and efficient tumor cell killing. However, these properties create sub-organ dose deposition effects that are not easily characterized by direct gamma-ray imaging (PET or SPECT). We present a computational procedure to determine the spatial distribution of absorbed dose from alpha-emitting radionuclides in tissues using digital autoradiography activity images from an ionizing-radiation quantum imaging detector (iQID). Data from At-radioimmunotherapy studies for allogeneic hematopoietic cell transplantation in a canine model were used to develop these methods. Nine healthy canines were treated with 16.9-30.9 MBq At/mg monoclonal antibodies (mAb). Lymph node biopsies from early (2-5 h) and late (19-20 h) time points (16 total) were obtained, with 10-20 consecutive 12-µm cryosections extracted from each and imaged with an iQID device. iQID spatial activity images were registered within a 3D volume for dose-point-kernel convolution, producing dose-rate maps. The accumulated absorbed doses for high- and low-rate regions were 9 ± 4 Gy and 1.2 ± 0.8 Gy from separate dose-rate curves, respectively. We further assess uptake uniformity, co-registration with histological pathology, and requisite slice numbers to improve microscale characterization of absorbed dose inhomogeneities in αRPT.
Topics: Animals; Dogs; Alpha Particles; Autoradiography; Radiopharmaceuticals; Radiometry; Radioisotopes; Antibodies, Monoclonal
PubMed: 36289434
DOI: 10.1038/s41598-022-22664-5 -
Molecular Imaging 2019Noise-induced hearing loss leads to anatomic and physiologic changes in primary auditory cortex (A1) and the adjacent dorsal rostral belt (RB). Since acetylcholine is...
Evaluating Cholinergic Receptor Expression in Guinea Pig Primary Auditory and Rostral Belt Cortices After Noise Damage Using [H]Scopolamine and [F]Flubatine Autoradiography.
Noise-induced hearing loss leads to anatomic and physiologic changes in primary auditory cortex (A1) and the adjacent dorsal rostral belt (RB). Since acetylcholine is known to modulate plasticity in other cortical areas, changes in A1 and RB following noise damage may be due to changes in cholinergic receptor expression. We used [H]scopolamine and [F]flubatine binding to measure muscarinic acetylcholine receptor (mAChR) and nicotinic acetylcholine receptor (nAChR) expression, respectively, in guinea pig A1 and RB 3 weeks following unilateral, left ear noise exposure, and a temporary threshold shift in hearing. [H]Scopolamine binding decreased in right A1 and RB (contralateral to noise) compared to sham controls across all cortical layers. [F]Flubatine binding showed a nonsignificant upward trend in right A1 following noise but only significantly increased in right RB and 2 layers of left RB (ipsilateral to noise). This selective response may ultimately influence cortical plasticity and function. The mechanism(s) by which cholinergic receptors are altered following noise exposure remain unknown. However, these data demonstrate noise exposure may differentially influence mAChRs that typically populate interneurons in A1 and RB more than nAChRs that are traditionally located on thalamocortical projections and provide motivation for cholinergic imaging in clinical patient populations of temporary or permanent hearing loss.
Topics: Animals; Autoradiography; Benzamides; Bridged Bicyclo Compounds, Heterocyclic; Female; Guinea Pigs; Hearing Loss; Receptors, Muscarinic; Receptors, Nicotinic; Scopolamine
PubMed: 31099304
DOI: 10.1177/1536012119848927 -
Acta Neuropathologica Communications Mar 2019[F-18]-MK-6240, a novel tau positron emission tomography (PET) tracer recently discovered for the in vivo detection of neurofibrillary tangles, has the potential to...
[F-18]-MK-6240, a novel tau positron emission tomography (PET) tracer recently discovered for the in vivo detection of neurofibrillary tangles, has the potential to improve diagnostic accuracy in the detection of Alzheimer disease. We have examined regional and substrate-specific binding patterns as well as possible off-target binding of this tracer on human brain tissue to advance towards its validation. We applied [F-18]-MK-6240 phosphor screen and high resolution autoradiography to postmortem samples from patients with a definite pathological diagnosis of Alzheimer disease, frontotemporal lobar degeneration-tau (Pick's disease, progressive supranuclear palsy and corticobasal degeneration), chronic traumatic encephalopathy, frontotemporal lobar degeneration-Tar DNA-binding protein 43 (TDP-43), dementia with Lewy bodies, cerebral amyloid angiopathy and elderly controls free of pathologic changes of neurodegenerative disease. We also directly compared the binding properties of [F-18]-MK-6240 and [F-18]-AV-1451 in human tissue, and examined potential nonspecific binding of both tau tracers to monoamine oxidases (MAO) by using autoradiography in the presence of selective monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B) inhibitors. Our data indicate that MK-6240 strongly binds to neurofibrillary tangles in Alzheimer disease but does not seem to bind to a significant extent to tau aggregates in non-Alzheimer tauopathies, suggesting that it may have a limited utility for the in vivo detection of these pathologies. There is no evidence of binding to lesions containing β-amyloid, α-synuclein or TDP-43. In addition, we identified MK-6240 strong off-target binding to neuromelanin and melanin-containing cells, and some weaker binding to areas of hemorrhage. These binding patterns are nearly identical to those previously reported by our group and others for [F-18]-AV-1451. Of note, [F-18]-MK-6240 and [F-18]-AV-1451 autoradiographic binding signals were only weakly displaced by competing concentrations of selective MAO-B inhibitor deprenyl but not by MAO-A inhibitor clorgyline, suggesting that MAO enzymes do not appear to be a significant binding target of any of these two tracers. Together these novel findings provide relevant insights for the correct interpretation of in vivo [F-18]-MK-6240 PET imaging.
Topics: Adult; Aged; Aged, 80 and over; Autoradiography; Brain; Female; Fluorine Radioisotopes; Humans; Isoquinolines; Male; Middle Aged; Neurodegenerative Diseases; Positron-Emission Tomography; Radiopharmaceuticals; Reproducibility of Results
PubMed: 30857558
DOI: 10.1186/s40478-019-0686-6 -
Drug Design, Development and Therapy 2021Novel radiotracer development for imaging dopamine transporters is a subject of interest because although [Tc]TRODAT-1, [I]β-CIT, and [I]FP-CIT are commercially...
INTRODUCTION
Novel radiotracer development for imaging dopamine transporters is a subject of interest because although [Tc]TRODAT-1, [I]β-CIT, and [I]FP-CIT are commercially available; Mo/Tc generator is in short supply and I production is highly dependent on compact cyclotron. Therefore, we designed a novel positron emission tomography (PET) tracer based on a tropane derivative through C-2 modification to conjugate NOTA for chelating Ga, a radioisotope derived from a Ge/Ga generator.
METHODS
IPCAT-NOTA was synthesized and labeled with [Ga]GaCl at room temperature. Biological studies on serum stability, LogP, and in vitro autoradiography (binding assay and competitive assay) were performed. Furthermore, ex vivo autoradiography, biodistribution, and dynamic PET imaging studies were performed in Sprague Dawley rats.
RESULTS
[Ga]IPCAT-NOTA obtained had a radiochemical yield of ≥90% and a specific activity of 4.25 MBq/nmol. [Ga]IPCAT-NOTA of 85% radiochemical purity (RCP%) was stable at 37°C for up to 60 minutes in serum with a lipophilicity of 0.88. The specific binding ratio (SBR%) reached 15.8 ± 6.7 at 60 minutes, and the 85% specific uptake could be blocked through co-injection at 100- and 1000-fold of the cold precursor in in vitro binding studies. Tissue regional distribution studies in rats with [Ga]IPCAT-NOTA showed striatal uptake (0.02% at 5 minutes and 0.007% at 60 minutes) with SBR% of 6%, 25%, and 62% at 5-15, 30-40, and 60-70 minutes, respectively, in NanoPET studies. The RCP% of [Ga]IPCAT-NOTA at 30 minutes in vivo remained 67.65%.
CONCLUSION
Data described here provide new information on the design of PET probe of conjugate/pendent approach for DAT imaging. Another chelator or another direct method of intracranial injection must be used to prove the relation between [Ga]IPCAT-NOTA uptake and transporter localization.
Topics: Animals; Autoradiography; Dopamine Plasma Membrane Transport Proteins; Gallium Radioisotopes; Heterocyclic Compounds, 1-Ring; Male; Positron-Emission Tomography; Rats; Rats, Sprague-Dawley; Time Factors; Tissue Distribution
PubMed: 34168430
DOI: 10.2147/DDDT.S288600