Labeling Of Plaques Research Articles

Antibody-Based In Vivo Imaging of Central Nervous System Targets-Evaluation of a Pretargeting Approach Utilizing a TCO-Conjugated Brain Shuttle Antibody and Radiolabeled Tetrazines.

Bioorthogonal pretargeted imaging using the inverse-electron-demand Diels-Alder (IEDDA) reaction between a tetrazine (Tz) and a trans-cyclooctene (TCO) represents an attractive strategy for molecular imaging via antibodies. The advantages of using a pretargeted imaging approach are on the one hand the possibility to achieve a high signal-to-noise ratio and imaging contrast; on the other hand, the method allows the uncoupling of the biological half-life of antibodies from the physical half-life of short-lived radionuclides. A brain-penetrating antibody (mAb) specific for β-amyloid (Aβ) plaques was functionalized with TCO moieties for pretargeted labeling of Aβ plaques in vitro, ex vivo, and in vivo by a tritium-labeled Tz. The overall aim was to explore the applicability of mAbs for brain imaging, using a preclinical model system. In vitro clicked mAb-TCO-Tz was able to pass the blood-brain barrier of transgenic PS2APP mice and specifically visualize Aβ plaques ex vivo. Further experiments showed that click reactivity of the mAb-TCO construct in vivo persisted up to 3 days after injection by labeling Aβ plaques ex vivo after incubation of brain sections with the Tz in vitro. An attempted in vivo click reaction between injected mAb-TCO and Tz did not lead to significant labeling of Aβ plaques, most probably due to unfavorable in vivo properties of the used Tz and a long half-life of the mAb-TCO in the blood stream. This study clearly demonstrates that pretargeted imaging of CNS targets via antibody-based click chemistry is a viable approach. Further experiments are warranted to optimize the balance between stability and reactivity of all reactants, particularly the Tz.

Selection of single domain anti-transferrin receptor antibodies for blood-brain barrier transcytosis using a neurotensin based assay and histological assessment of target engagement in a mouse model of Alzheimer's related amyloid-beta pathology.

The blood-brain barrier (BBB) presents a major obstacle in developing specific diagnostic imaging agents for many neurological disorders. In this study we aimed to generate single domain anti-mouse transferrin receptor antibodies (anti-mTfR VHHs) to mediate BBB transcytosis as components of novel MRI molecular contrast imaging agents. Anti-mTfR VHHs were produced by immunizing a llama with mTfR, generation of a VHH phage display library, immunopanning, and in vitro characterization of candidates. Site directed mutagenesis was used to generate additional variants. VHH fusions with neurotensin (NT) allowed rapid, hypothermia-based screening for VHH-mediated BBB transcytosis in wild-type mice. One anti-mTfR VHH variant was fused with an anti-amyloid-beta (Aβ) VHH dimer and labeled with fluorescent dye for direct assessment of in vivo target engagement in a mouse model of AD-related Aβ plaque pathology. An anti-mTfR VHH called M1 and variants had binding affinities to mTfR of <1nM to 1.52nM. The affinity of the VHH binding to mTfR correlated with the efficiency of the VHH-NT induced hypothermia effects after intravenous injection of 600 nmol/kg body weight, ranging from undetectable for nonbinding mutants to -6°C for the best mutants. The anti-mTfR VHH variant M1P96H with the strongest hypothermia effect was fused to the anti-Aβ VHH dimer and labeled with Alexa647; the dye-labeled VHH fusion construct still bound both mTfR and Aβ plaques at concentrations as low as 0.22 nM. However, after intravenous injection at 600 nmol/kg body weight into APP/PS1 transgenic mice, there was no detectible labeling of plaques above control levels. Thus, NT-induced hypothermia did not correlate with direct target engagement in cortex, likely because the concentration required for NT-induced hypothermia was lower than the concentration required to produce in situ labeling. These findings reveal an important dissociation between NT-induced hypothermia, presumably mediated by hypothalamus, and direct engagement with Aβ-plaques in cortex. Additional methods to assess anti-mTfR VHH BBB transcytosis will need to be developed for anti-mTfR VHH screening and the development of novel MRI molecular contrast agents.

Deep Learning for the Automatic Quantification of Pleural Plaques in Asbestos-Exposed Subjects.

Objective: This study aimed to develop and validate an automated artificial intelligence (AI)-driven quantification of pleural plaques in a population of retired workers previously occupationally exposed to asbestos. Methods: CT scans of former workers previously occupationally exposed to asbestos who participated in the multicenter APEXS (Asbestos PostExposure Survey) study were collected retrospectively between 2010 and 2017 during the second and the third rounds of the survey. A hundred and forty-one participants with pleural plaques identified by expert radiologists at the 2nd and the 3rd CT screenings were included. Maximum Intensity Projection (MIP) with 5 mm thickness was used to reduce the number of CT slices for manual delineation. A Deep Learning AI algorithm using 2D-convolutional neural networks was trained with 8280 images from 138 CT scans of 69 participants for the semantic labeling of Pleural Plaques (PP). In all, 2160 CT images from 36 CT scans of 18 participants were used for AI testing versus ground-truth labels (GT). The clinical validity of the method was evaluated longitudinally in 54 participants with pleural plaques. Results: The concordance correlation coefficient (CCC) between AI-driven and GT was almost perfect (>0.98) for the volume extent of both PP and calcified PP. The 2D pixel similarity overlap of AI versus GT was good (DICE = 0.63) for PP, whether they were calcified or not, and very good (DICE = 0.82) for calcified PP. A longitudinal comparison of the volumetric extent of PP showed a significant increase in PP volumes (p < 0.001) between the 2nd and the 3rd CT screenings with an average delay of 5 years. Conclusions: AI allows a fully automated volumetric quantification of pleural plaques showing volumetric progression of PP over a five-year period. The reproducible PP volume evaluation may enable further investigations for the comprehension of the unclear relationships between pleural plaques and both respiratory function and occurrence of thoracic malignancy.

Evaluation of Styrylbenzene analog- FSB and its affinity to bind parenchymal plaques and tangles in patients of Alzheimer's disease.

Although several histochemical markers for senile plaques (SP) and neurofibrillary tangles (NFTs) have been synthesized since the discovery of plaques in Alzheimer's disease (AD), only a handful of these markers stain both lesions in the human brain. Despite discovery of its ability to stain both SP and NFT over 13years ago, the styrylbenzene derivative, (E,E)-1-fluoro-2,5-bis-(3-hydroxycarbonyl-4-hydroxy)styrylbenzene (FSB), has only recently gained attention, primarily due to its ability to function as a contrasting agent for MRI imaging of AD pathology in vivo. The structure of the compound is a nuclide with quantized angular momentum, which explains its value as a contrast agent. In the current study, modification of the established staining procedure produced meaningful improvement in the labeling of plaques and tangles in the human brain. We utilized two rodent models of AD to show FSB's value in labeling both Aβ and tau lesions. Furthermore, our current modification allows us to detect SP in rodent brains in 15min and both SP and NFT in human brains within 20min. The study presents new evidence regarding potential binding targets for FSB as well as optimization protocols in which various parameters have been manipulated to show how section thickness, use of frozen versus paraffin-embedded sections, and selection of staining media can affect the intensity of the plaque and tangle staining in the brain. To determine the target FSB potentially binds, we performed double immunolabeling of FSB with mOC64 (a conformational antibody that label Aβ1-42). Results indicated that all plaques in the brain colocalized with mOC64, suggesting that FSB has the potential to bind all Aβ containing plaques, making it a very sensitive detector of multiple forms of SP... All antibodies were assessed for the degree of colocalization with FSB in order to better understand potential binding targets. We found more than 90% hyperphosphorylated Tau against AT8, AT180 and S214 colocalized with FSB labeled tangles. On the other hand, more than 90% of the mOC64 containing plaques colocalized with FSB stained plaques. Our results indicate that FSB is a valuable marker that can be used to detect AD pathologies in human and rodent brains with greater fluorescence intensity relative to other conventional fluorescence markers.

Use of a stable and solvent-soluble variant of Amylo-Glo, Amylo-Glo+, for the high-contrast and resolution fluorescent localization of amyloid plaques in murine and human brain tissue sections

BackgroundAlthough numerous different fluorescent compounds have been used for the fluorescent localization of amyloid plaques, limitations include weak fluorescence, low contrast, low resolution, broad excitation / emission profile and chemical instability. New methodAmylo-Glo+ was reconstituted from a powder into a stable solution for the histological staining of plaques in brain tissue sections from both patients diagnosed with Alzheimer’s disease and APP/PS1 transgenic mice. ResultsAmylo-Glo+ was found to result in high resolution and contrast labeling of amyloid plaques. The tracer was excited exclusively by ultraviolet light illumination. The staining of amyloid plaques corresponded with the labeling pattern seen following staining with HQ-O. Counterstaining with ethidium bromide resulted in no bleed-through of the Amylo-Glo+ under blue or green light excitation. The tracer was stable in both powder and solution form. Comparison with existing methodsAmylo-Glo+ was found to be more stable, in both a powder and solution form, than the original Amylo-Glo, brighter than Congo red, of narrower emission and greater contrast than Thioflavine S and of narrower emission than X-34 and BSB. ConclusionAmylo-Glo+ is a stable and solvent soluble variant of Amylo-Glo that allows for the high contrast and resolution localization of amyloid plaques in tissue sections from the brains of transgenic mice and humans with Alzheimer’s disease. The tracer is also solely excited by ultraviolet light, making it ideal for fluorescent multiple labeling studies in combination with commonly used red or green fluorophores. It is also stable in both solution and powder form, unlike the original Amylo-Glo which is only available as a basic solution that is prone to precipitation.

Feasibility of InVivo Imaging of Fibroblast Activation Protein in Human Arterial Walls.

Increased expression of fibroblast-activating protein (FAP) in fibrous caps may contribute to progression of atherosclerotic plaques. Methods: Forty-one patients who underwent 68Ga-conjugated quinoline-based FAP inhibitor (68Ga-FAPI-04) PET/CT for noncardiovascular indications were retrospectively analyzed. Correlations were assessed between the uptake of 68Ga-FAPI-04 in large arterial walls (SUVmax and target-to-background ratio, TBR) and degree of calcification and cardiovascular risk factors. Results: Focal arterial uptake of 68Ga-FAPI-04 or calcification was detected in 1,177 arterial segments in all 41 patients. TBR was negatively correlated with the degree of calcification (Hounsfield units) (r = -0.27, P < 0.01). Mean TBR in higher-risk patients was greater than in lower-risk patients (2.2 ± 0.3 vs. 1.8 ± 0.3, P < 0.01). Immunohistochemical labeling of carotid plaques exhibited prominent FAP expression in a thin fibrous cap and moderate FAP expression in a thick cap. Conclusion:68Ga-FAPI-04 PET/CT might have potential for imaging fibroblastic activation in the arterial wall.

In vivo demonstration of Congo Red labeled amyloid plaques via perfusion in the Alzheimer disease rat model

BackgroundCongo Red (CR) has been used for its binding affinity to amyloid fibrils for the better part of a century. Recently, our laboratory has demonstrated its ability to bind to tau protein as well. New MethodHere we describe a novel methodology for fast, thorough, whole-brain labeling of amyloid plaques with CR via perfusion. We tested five different variants which altered the volume of CR, the speed of perfusion, and the solution CR was solubilized in to determine the best results. Results and ConclusionWe determined that intra-cardiac perfusion of animals with 0.5 % CR in 100 ml of 50 % ethanol or perfusion with 0.5 of CR in 100 ml of 10 % neutral buffer formalin both perfused at a rate of 30 ml/min for 3.3 min resulted in the clearest CR labeling, with little to no background noise. Both variants were compatible with subsequent immunolabeling procedures for NU-1, as well as Ferritin and GFAP. Compared to traditional CR plaque labeling methodology, this new method allows for quick whole brain CR-labeling. This reduces the amount of time from days to mere minutes. It also reduces potential for variability that would result from staining slides in batches. Thus, CR-perfusion is a rapid, thorough method that can be utilized to rapidly stain amyloid in the rodent brain.

Golgi-Cox impregnation combined with fluorescence staining of amyloid plaques reveals local spine loss in an Alzheimer mouse model

BackgroundSpine loss is a hallmark of Alzheimer´s and other neurodegenerative diseases, and testing candidate therapeutic drugs needs quantitative analysis of dendritic spine densities. Golgi-Cox impregnation of neurons is a classical method to visualize dendritic spines in diseased brains. Importantly, at early disease stages spine loss occurs locally in the vicinity of amyloid plaques, and concomitant fluorescence labeling of amyloid plaques is required to detect local spine damage. New MethodBecause Golgi-Cox impregnation is done on unsectioned brains, whereas fluorescence staining is performed on sectioned material, the combination is technically challenging. We have now developed a novel combination of Golgi-Cox impregnation with methoxy-X04 fluorescence labeling of plaques that is performed on unsectioned brains. ResultsWe used this new combination method to quantify dendritic spine densities in mouse hippocampal CA1 pyramidal neurons. Comparison of neurons from wildtype and APP/PS1 mice revealed local spine loss in the vicinity of amyloid plaques in both male and female APP/PS1 mice. Comparison with existing methodGolgi-Cox impregnation of neurons combined with methoxy-X04 staining of amyloid plaques is a highly reliable, easy-to-use method for permanent visualization of spines as compared to the technically more sophisticated and less stable fluorescence imaging of spines. ConclusionOur novel combination method will be highly useful for testing potential therapeutic drugs in Alzheimer mouse models.

Labeling and Imaging of Amyloid Plaques in Brain Tissue Using the Natural Polyphenol Curcumin.

Deposition of amyloid beta protein (Aβ) in extra- and intracellular spaces is one of the hallmark pathologies of Alzheimer's disease (AD). Therefore, detection of the presence of Aβ in AD brain tissue is a valuable tool for developing new treatments to prevent the progression of AD. Several classical amyloid binding dyes, fluorochrome, imaging probes, and Aβ-specific antibodies have been used to detect Aβ histochemically in AD brain tissue. Use of these compounds for Aβ detection is costly and time consuming. However, because of its intense fluorescent activity, high-affinity, and specificity for Aβ, as well as structural similarities with traditional amyloid binding dyes, curcumin (Cur) is a promising candidate for labeling and imaging of Aβ plaques in postmortem brain tissue. It is a natural polyphenol from the herb Curcuma longa. In the present study, Cur was used to histochemically label Aβ plaques from both a genetic mouse model of 5x familial Alzheimer's disease (5xFAD) and from human AD tissue within a minute. The labeling capability of Cur was compared to conventional amyloid binding dyes, such as thioflavin-S (Thio-S), Congo red (CR), and Fluoro-jade C (FJC), as well as Aβ-specific antibodies (6E10 and A11). We observed that Cur is the most inexpensive and quickest way to label and image Aβ plaques when compared to these conventional dyes and is comparable to Aβ-specific antibodies. In addition, Cur binds with most Aβ species, such as oligomers and fibrils. Therefore, Cur could be used as the most cost-effective, simple, and quick fluorochrome detection agent for Aβ plaques.

Labeling and Imaging of Amyloid Plaques in Brain Tissue Using the Natural Polyphenol Curcumin

Labeling and Imaging of Amyloid Plaques in Brain Tissue Using the Natural Polyphenol Curcumin

High Contrast and Resolution Labeling of Amyloid Plaques in Tissue Sections from APP-PS1 Mice and Humans with Alzheimer's Disease with the Zinc Chelator HQ-O: Practical and Theoretical Considerations.

Background:Various methodologies have been employed for the localization of amyloid plaques in numerous studies on Alzheimer’s disease. The majority of these stains are thought to label the plaques by virtue of their affinity for aggregated Aβ. However, plaques are known to contain numerous other components, including multivalent metals such as zinc.Objective:This investigates whether it is possible to localize the presence of zinc in parenchymal and vascular amyloid plaques in afflicted brains. To accomplish this, a novel fluorescent zinc chelator, HQ-O, was investigated to determine its mechanism of binding and to optimize a stain for the high contrast and resolution histological localization of amyloid plaques.Methods:A novel zinc chelator, HQ-O, was developed for localizing zinc within amyloid plaques. The histology involves incubating tissue sections in a dilute aqueous solution of HQ-O. Its compatibility with a variety of other fluorescent methodologies is described.Results:All amyloid plaques are stained in fine detail and appear bright green under blue light excitation. The staining of parenchymal plaques correlates closely with that seen following staining with antibodies to Aβ, however, the HQ-O sometimes also label additional globular structures within blood vessels. In situ mechanistic studies revealed that fluorescent plaque-like structures are only observed with HQ-O when synthetic Aβx-42 is aggregated in the presence of zinc.Conclusion:Zinc is intimately bound to all amyloid plaques, which was demonstrated by its histological localization using a novel fluorescent zinc chelator, HQ-O. Additionally, the tracer is also capable of labeling intravascular leucocytes due to their high zinc content.

Oligoethyleneoxy-Modified 99mTc-Labeled β-Amyloid Imaging Probes with Improved Brain Pharmacokinetics for Single-Photon Emission Computed Tomography.

An oligoethyleneoxy linker was introduced for conjugation between 99mTc/Re-bis(aminoethanethiol) (BAT) and β-amyloid (Aβ) binding scaffolds. Rhenium complexes exhibited high to moderate binding affinity to Aβ1-42 aggregates and efficient fluorescent staining to Aβ plaques in brain tissue. After radiolabeling, the 99mTc-labeled probes revealed improved brain pharmacokinetics in normal ICR mice. Probe [99mTc]15 with potent binding affinity (Ki = 13.4 nM) and the highest initial brain uptake (2.10% ID/g at 2 min) in normal ICR mice was evaluated further. In vitro autoradiography showed specific labeling of Aβ plaques by [99mTc]15 in transgenic (Tg) mouse brain tissue. Ex vivo autoradiography further demonstrated its efficient labeling of Aβ plaques in a living Tg mouse. In vivo single photon emission computed tomography (SPECT)/CT imaging in six rhesus monkeys revealed remarkably improved brain uptakes (1.94-2.63% ID within 20 min) of [99mTc]15, making it highly potential to be used in humans for Aβ plaques imaging in the brain.

Uptake of citrate-coated iron oxide nanoparticles into atherosclerotic lesions in mice occurs via accelerated transcytosis through plaque endothelial cells

AbstractVery small superparamagnetic iron oxide nanoparticles (VSOPs) rapidly accumulate in atherosclerotic lesions, thereby enabling plaque visualization by magnetic resonance imaging (MRI). This study was performed to identify the uptake mechanisms of VSOPs into atherosclerotic plaques. Low-density lipoprotein receptor-deficient (LDLR−/−) mice with advanced atherosclerosis were analyzed using MRI and transmission electron microscopy (TEM) at various time points after intravenous administration of VSOPs. Post-mortem MRI detected VSOP labeling of atherosclerotic plaques 10 min after injection, and the signal increased over the first 3 h. TEM revealed that the intensive plaque labeling was mediated by accelerated transcytosis of VSOPs through endothelial cells overlaying atherosclerotic lesions. Experiments with endocytosis inhibitors and small interfering RNA (siRNA) revealed a dynamin-dependent mechanism involving both clathrin- and caveolin-mediated processes. In cell culture experiments, endothelial VSOP uptake was enhanced under proatherogenic flow and TNFα stimulation, conditions that are both present in plaque areas. Our study demonstrates that VSOPs enable non-invasive MRI assessment of accelerated endothelial transcytosis, an important pathomechanism in atherosclerotic plaque formation.

99mTc-Labeled 2-Arylbenzothiazoles: Aβ Imaging Probes with Favorable Brain Pharmacokinetics for Single-Photon Emission Computed Tomography.

A series of 2-arylbenzothiazole derivatives conjugated with bis(aminoethanethiol) (BAT) chelating groups were designed and synthesized. A competitive binding assay-based screening was used to select seven rhenium complexes with potent binding affinity toward Aβ1-42 aggregates (Ki < 50 nM) for 99mTc labeling and further evaluation. The 99mTc-labeled probes showed good affinity and specificity to Aβ plaques in Tg mouse brain tissue in in vitro autoradiography studies. Moreover, [99mTc]14b exhibited favorable brain pharmacokinetics in normal mice (2.11% ID/g at 2 min and 0.62% ID/g at 60 min). Ex vivo autoradiography revealed extensive labeling of Aβ plaques by [99mTc]14b in the brain of Tg mice. Furthermore, we performed the first single-photon emission computed tomography (SPECT) imaging study in nonhuman primates with 99mTc-labeled Aβ probes. The semiquantitative data showed that [99mTc]14b penetrated the brains of rhesus monkeys. These results indicate that [99mTc]14b could be utilized as a SPECT imaging probe for Aβ plaques.

Optically Pure Diphenoxy Derivatives as More Flexible Probes for β-Amyloid Plaques.

The highly rigid and planar scaffold with π-conjugated systems has been widely considered to be indispensable for Aβ binding probes. However, the flexible benzyloxybenzene derivative [(125)I]BOB-4 represents an excellent lead candidate for targeting Aβ in AD brains. Based on that, we designed two pairs of more flexible and optically pure diphenoxy derivatives with a chiral center as novel Aβ probes. These compounds possessed high affinity (Ki = 15.8-45.0 nM) for Aβ1-42 aggregates, and (R)-enantiomers showed slightly better binding ability than (S)-enantiomers. In addition, the competition binding assay implied that the optically pure diphenoxy derivatives with more flexible geometry shared the same binding site as IMPY, a classical rigid and planar Aβ probe. For (125)I-radiolabeled enantiomers, (S)-[(125)I]5 and (R)-[(125)I]5, specific plaque labeling on brain sections of Tg mice and AD patients were observed in in vitro autoradiography, persuasively proving the excellent affinity of the probes. In biodistribution, (S)-[(125)I]5 and (R)-[(125)I]5 with relatively low lipophilicity exhibited moderate initial brain uptake (4.37% and 3.72% ID/g at 2 min, respectively) and extremely fast washout from normal mice brain (brain2min/brain60min = 19.0 and 17.7, respectively). In summary, the separate enantiomers displayed similar properties in vitro and in vivo, and (S/R)-[(123)I]5 may be potential SPECT probes for recognizing Aβ plaques in AD brains.

In Vivo Amyloid-β Imaging in the APPPS1-21 Transgenic Mouse Model with a (89)Zr-Labeled Monoclonal Antibody.

Introduction: The accumulation of amyloid-β is a pathological hallmark of Alzheimer’s disease and is a target for molecular imaging probes to aid in diagnosis and disease monitoring. This study evaluated the feasibility of using a radiolabeled monoclonal anti-amyloid-β antibody (JRF/AβN/25) to non-invasively assess amyloid-β burden in aged transgenic mice (APPPS1–21) with μPET imaging.Methods: We investigated the antibody JRF/AβN/25 that binds to full-length Aβ. JRF/AβN/25 was radiolabeled with a [89Zr]-desferal chelate and intravenously injected into 12–13 month aged APPPS1–21 mice and their wild-type (WT) controls. Mice underwent in vivo μPET imaging at 2, 4, and 7 days post injection and were sacrificed at the end of each time point to assess brain penetrance, plaque labeling, biodistribution, and tracer stability. To confirm imaging specificity we also evaluated brain uptake of a non-amyloid targeting [89Zr]-labeled antibody (trastuzumab) as a negative control, additionally we performed a competitive blocking study with non-radiolabeled Df-Bz-JRF/AβN/25 and finally we assessed the possible confounding effects of blood retention.Results: Voxel-wise analysis of μPET data demonstrated significant [89Zr]-Df-Bz-JRF/AβN/25 retention in APPPS1–21 mice at all time points investigated. With ex vivo measures of radioactivity, significantly higher retention of [89Zr]-Df-Bz-JRF/AβN/25 was found at 4 and 7 days pi in APPPS1–21 mice. Despite the observed genotypic differences, comparisons with immunohistochemistry revealed that in vivo plaque labeling was low. Furthermore, pre-treatment with Df-Bz-JRF/AβN/25 only partially blocked [89Zr]-Df-Bz-JRF/AβN/25 uptake indicative of a high contribution of non-specific binding.Conclusion: Amyloid plaques were detected in vivo with a radiolabeled monoclonal anti-amyloid antibody. The low brain penetrance of the antibody in addition to non-specific binding prevented an accurate estimation of plaque burden. However, it should be noted that [89Zr]-Df-Bz-JRF/AβN/25 nevertheless demonstrated in vivo binding and strategies to increase brain penetrance would likely achieve better results.

Preliminary Characterization and In Vivo Studies of Structurally Identical (18)F- and (125)I-Labeled Benzyloxybenzenes for PET/SPECT Imaging of β-Amyloid Plaques.

With the assistance of molecular docking and 3D-QSAR models established previously, structurally identical 18F- and 125I-labeled benzyloxybenzene derivatives were designed to achieve the early detection of Aβ plaques by PET/SPECT imaging. In competition binding assay, ligands 7a and 12a displayed high binding affinities to Aβ42 aggregates with Ki values of 19.5 nM and 23.9 nM, respectively. Specific plaque labeling was observed on the in vitro autoradiography of brain sections from AD patients and Tg mice. In biodistribution, [125I]7a, [18F]7a, [125I]12a and [18F]12a all exhibited high initial brain uptakes (>5% ID/g at 2 min). [125I]7a and [125I]12a cleared fast from the normal brain regions, while corresponding [18F]7a and [18F]12a showed slow washout rates. Dynamic microPET/CT and microSPECT/CT imaging data in normal ICR mice were in accordance with in vivo biodistribution results. In vivo metabolism results indicated that the different clearance profiles between the structurally identical 18F- and 125I-labeled tracers could be attributed to different biochemical characteristics of the radiometabolites. Radioiodinated benzyloxybenzene derivatives exhibited good in vivo biostability in brain. Ex vivo autoradiography further confirmed the strong in vivo Aβ labeling ability of [125I]7a. These new fluorinated and iodinated benzyloxybenzenes can develop into PET/SPECT dual imaging agents targeting Aβ plaques.

2-Phenylbenzothiazole conjugated with cyclopentadienyl tricarbonyl [CpM(CO)3] (M = Re, (99m)Tc) complexes as potential imaging probes for β-amyloid plaques.

Technetium-99m-labeled cyclopentadienyl tricarbonyl complexes conjugated with the 2-phenylbenzothiazole binding motif were synthesized. The rhenium surrogates , , and were demonstrated to have moderate to high affinities for Aβ1-42 aggregates with Ki values of 142, 76, 64 and 24 nM, respectively. During the fluorescence staining of brain sections of transgenic mice and patients with Alzheimer's disease, these rhenium complexes demonstrated perfect and intense labeling of Aβ plaques. Moreover, in in vitro autoradiography, (99m)Tc-labeled complexes clearly detected β-amyloid plaques on sections of brain tissue from transgenic mice, which confirmed the sufficient affinity of these tracers for Aβ plaques. However, these compounds did not show desirable properties in vivo, especially showing poor brain uptake (below 0.5% ID g(-1)), which will hinder the further development of these tracers as brain imaging agents. Nonetheless, it is encouraging that these (99m)Tc-labeled complexes designed by a conjugate approach displayed sufficient affinities for Aβ plaques.

Genetic fuzzy rule based classification systems for coronary plaque characterization based on intravascular ultrasound images

Vascular tissue characterization is of great importance concerning the possibility of an Acute Cardiac Syndrome (ACS). Gray-scale intravascular ultrasound (IVUS) is a powerful tomographic modality providing a thorough visualization of coronary arteries. Among the existing methods, virtual histology (VH) is the most popular and clinically available technique for plaque component analysis. IVUS-VH though suffers from a poor longitudinal resolution due to the electrocardiogram (ECG)-gated frame acquisition. In order to surmount this demerit, a new image-based methodology for plaque assessment is suggested in this paper that differentiates tissue components into four classes: calcium, necrotic core, fibrous and fibro-lipid. The available IVUS frames characterized by VH are used for plaque labeling. In addition, a rich set of five textural feature families are extracted from IVUS images and computed at different scales. To increase the discrimination capabilities between the classes, all features are combined into an integrated feature vector. The classification of plaque types is accomplished using a genetic fuzzy rule-based classification system (GFRBCS) that is able to handle effectively highly-dimensional feature spaces. The incorporated feature selection mechanism along with the rule extraction algorithm allows the creation of compact fuzzy rule bases with enhanced classification accuracy. The high interpretability properties of our classifier assist physicians to gain a deeper insight regarding the impact of features involved in the evaluation of atherosclerotic plaques. An extensive experimental analysis is carried out, where various tests are performed in order to highlight the advantages of the proposed scheme against existing methods of the literature, including other GRBCSs and the support vector machine (SVM) classifier. In particular, the attained results show that the applied classifier exhibits better generalization capabilities than the competing methods, i.e., higher accuracy in characterizing unseen IVUS images.

Intraventricular human immunoglobulin distributes extensively but fails to modify amyloid in a mouse model of amyloid deposition.

Intravenous immunoglobulin infusions into Alzheimer patients have been found to provide cognitive benefit over a period of 6 mo in open label studies. One suggestion has been that these preparations contain small amounts of antibodies directed against monomeric and oligomeric Aβ which underlie their effectiveness in patients. To test this hypothesis, we infused Gammagard, a version of intravenous immunoglobulin (IVIG), into the lateral ventricle of amyloid precursor protein (APP) transgenic mice with pre-existing amyloid deposits. Mice were infused over 4 weeks, and tested behaviorally for the last 2 weeks of treatment. Brains were analyzed for histopathology. We found widespread distribution of human-immunoglobulin G (h-IgG) staining in the mouse forebrain, including cerebral cortices and hippocampus. Some cortical neurons appeared to concentrate the h-IgG, but we did not detect evidence of amyloid plaque labeling by h-IgG. The IVIG-treated mice had no change in phenotype compared to saline-infused animals with respect to activity, learning and memory, or amyloid deposition. APP mice infused with an anti-Aβ monoclonal antibody did show some reduction in amyloid deposits. These data do not support the argument that anti-Aβ antibodies in IVIG preparations are responsible for cognitive benefits seen with these preparations.