Age-related changes in CB1 receptor expression and function and the behavioral effects of cannabinoid receptor ligands.

Cannabinoid use has increased among aging individuals. However, little information on age-related differences in the behavioral effects of these agents is available. To explore potential differences in the behavioral effects of cannabinoids, we determined effects of Δ9-tetrahydrocannabinol (THC, 1-10 mg/kg) or rimonabant (0.3-3.2 mg/kg) on operant fixed-ratio responding (FR10) for food in young adult (6 months) and aged (29 months) rats. THC dose-dependently decreased responding for food. Rimonabant alone had little or no effect on responding up to 1.0 mg/kg, but disrupted responding following a 3.2 mg/kg dose. Rimonabant (1.0 mg/kg) partially antagonized response disruption by THC. These effects were similar in young adult and aged rats. However, aging has been reported to change the neurobiology of cannabinoid CB1 receptors. To confirm our rats exhibited such differences, we assessed CB1 receptor binding sites and function in six subcortical (caudate, nucleus accumbens CA1, and CA2/CA3), and three cortical regions (medial prefrontal, temporal, entorhinal) in young adult (6 months) or aged (26 months) male Lewis rats using quantitative autoradiography. CB1 receptor binding sites were reduced in cortical, but not subcortical brain regions of aged rats. CB1 receptor function, at the level of receptor-G protein interaction, was not different in any region studied. Results indicate that down-regulation of CB1 receptor binding sites observed in cortical regions of aged rats was not accompanied by a commensurate decrease in CB1 receptor-stimulated [35S]GTPγS binding, suggesting a compensatory increase in receptor function in cortical areas. Together, our results provide additional evidence of age-related changes in central CB1 receptor populations. However, the functional compensation for decreased CB1 receptor binding may mitigate changes in behavioral effects of cannabinoids. With the rising use of cannabinoid-based therapeutics among aging populations, further evaluation of age-related changes in the cannabinoid system and the impact of these changes on effects of this class of drugs is warranted.

Pharmacological characterization of mutant huntingtin aggregate-directed PET imaging tracer candidates.

Huntington's disease (HD) is caused by a CAG trinucleotide repeat expansion in the first exon of the huntingtin (HTT) gene coding for the huntingtin (HTT) protein. The misfolding and consequential aggregation of CAG-expanded mutant HTT (mHTT) underpin HD pathology. Our interest in the life cycle of HTT led us to consider the development of high-affinity small-molecule binders of HTT oligomerized/amyloid-containing species that could serve as either cellular and in vivo imaging tools or potential therapeutic agents. We recently reported the development of PET tracers CHDI-180 and CHDI-626 as suitable for imaging mHTT aggregates, and here we present an in-depth pharmacological investigation of their binding characteristics. We have implemented an array of in vitro and ex vivo radiometric binding assays using recombinant HTT, brain homogenate-derived HTT aggregates, and brain sections from mouse HD models and humans post-mortem to investigate binding affinities and selectivity against other pathological proteins from indications such as Alzheimer's disease and spinocerebellar ataxia 1. Radioligand binding assays and autoradiography studies using brain homogenates and tissue sections from HD mouse models showed that CHDI-180 and CHDI-626 specifically bind mHTT aggregates that accumulate with age and disease progression. Finally, we characterized CHDI-180 and CHDI-626 regarding their off-target selectivity and binding affinity to beta amyloid plaques in brain sections and homogenates from Alzheimer's disease patients.

Molecular imaging of fibroblast activation protein after myocardial infarction using the novel radiotracer [68Ga]MHLL1.

Background: Myocardial infarction (MI) evokes an organized remodeling process characterized by the activation and transdifferentiation of quiescent cardiac fibroblasts to generate a stable collagen rich scar. Early fibroblast activation may be amenable to targeted therapy, but is challenging to identify in vivo. We aimed to non-invasively image active fibrosis by targeting the fibroblast activation protein (FAP) expressed by activated (myo)fibroblasts, using a novel positron emission tomography (PET) radioligand [68Ga]MHLL1 after acute MI. Methods: One-step chemical synthesis and manual as well as module-based radiolabeling yielded [68Ga]MHLL1. Binding characteristics were evaluated in murine and human FAP-transfected cells, and stability tested in human serum. Biodistribution in healthy animals was interrogated by dynamic PET imaging, and metabolites were measured in blood and urine. The temporal pattern of FAP expression was determined by serial PET imaging at 7 d and 21 d after coronary artery ligation in mice as percent injected dose per gram (%ID/g). PET measurements were validated by ex vivo autoradiography and immunostaining for FAP and inflammatory macrophages. Results: [68Ga]MHLL1 displayed specific uptake in murine and human FAP-positive cells (p = 0.0208). In healthy mice the tracer exhibited favorable imaging characteristics, with low blood pool retention and dominantly renal clearance. At 7 d after coronary artery ligation, [68Ga]MHLL1 uptake was elevated in the infarct relative to the non-infarcted remote myocardium (1.3 ± 0.3 vs. 1.0 ± 0.2 %ID/g, p < 0.001) which persisted to 21 d after MI (1.3 ± 0.4 vs. 1.1 ± 0.4 %ID/g, p = 0.013). Excess unlabeled compound blocked tracer accumulation in both infarct and non-infarct remote myocardium regions (p < 0.001). Autoradiography and histology confirmed the regional uptake of [68Ga]MHLL1 in the infarct and especially border zone regions, as identified by Masson trichrome collagen staining. Immunostaining further delineated persistent FAP expression at 7 d and 21 d post-MI in the border zone, consistent with tracer distribution in vivo. Conclusion: The simplified synthesis of [68Ga]MHLL1 bears promise for non-invasive characterization of fibroblast activation protein early in remodeling after MI.

Synthesis, Radiolabeling, and Preliminary in vivo Evaluation of [68Ga] IPCAT-NOTA as an Imaging Agent for Dopamine Transporter.

INTRODUCTION: Novel radiotracer development for imaging dopamine transporters is a subject of interest because although [99mTc]TRODAT-1, [123I]ß-CIT, and [123I]FP-CIT are commercially available; 99Mo/99mTc generator is in short supply and 123I 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 68Ga, a radioisotope derived from a 68Ge/68Ga generator. METHODS: IPCAT-NOTA 22 was synthesized and labeled with [68Ga]GaCl4 - 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: [68Ga]IPCAT-NOTA 24 obtained had a radiochemical yield of ≥90% and a specific activity of 4.25 MBq/nmol. [68Ga]IPCAT-NOTA 24 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 [68Ga]IPCAT-NOTA 24 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 [68Ga]IPCAT-NOTA 24 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 [68Ga]IPCAT-NOTA 24 uptake and transporter localization.

Evaluation of organ glucose metabolism by 18F-FDG accumulation with insulin loading in aged mice compared with young normal mice.

It is important to determine the functional changes of organs that occur as a result of aging, the understanding of which may lead to the maintenance of a healthy life. Glucose metabolism in healthy bodies is one of the potential markers used to evaluate the changes of organ function. Thus, information about normal organ glucose metabolism may help to understand the functional changes of organs. [18F]-Fluoro-2-deoxy-2-D-glucose (18F-FDG), a glucose analog, has been used to measure glucose metabolism in various fields, such as basic medical research and drug discovery. However, glucose metabolism changes in aged animals have not yet been fully clarified. The aim of this study is to evaluate changes in glucose metabolism in organs and brain regions by measuring 18F-FDG accumulation and 18F-FDG autoradiography with insulin loading in aged and young wild-type mice. In the untreated groups, the levels of 18F-FDG accumulation in the blood, plasma, muscle, lungs, spleen, pancreas, testes, stomach, small intestine, kidneys, liver, brain, and brain regions, namely, the cortex, striatum, thalamus, and hippocampus, were all significantly higher in the aged mice. The treated group showed lower 18F-FDG accumulation levels in the pancreas and kidneys, as well as in the cortex, striatum, thalamus, and hippocampus in the aged mice than the untreated groups, whereas higher 18F-FDG accumulation levels were observed in those in the young mice. These results demonstrate that insulin loading decreases effect on 18F-FDG accumulation levels in some organs of the aged mice. Therefore, aging can increase insulin resistance and lead to systemic glucose metabolism dysfunction.

Discrete binding patterns of two heparin-reactive proteins, basic fibroblast growth factor and peptide p5R, in amyloid-laden and healthy mice.

Peptide p5R is a synthetic, polybasic, heparin-binding peptide that preferentially reacts with amyloid deposits in vivo and in tissue sections. Basic fibroblast growth factor (bFGF1) similarly interacts with heparin-like molecules, notably heparan sulfate proteoglycans (HSPG), in the extracellular matrix and on cell surfaces. The aim of this study was to compare the biodistribution of p5R and bFGF in healthy mice as well as those with systemic inflammation-associated amyloidosis (AA), which contains HSPG, by using SPECT/CT imaging, tissue biodistribution measurements and micro-autoradiography. Although both proteins are known to bind heparan sulfate, their biodistribution was remarkably different in the healthy and diseased animals. Imaging revealed uptake of both radiolabeled proteins in the liver, spleen, and kidneys of mice with amyloidosis; however, 125I-bFGF, but not 125I-p5R, was observed in normal tissue at sites of HSPG expression, including the hepatic and splenic sinusoids and renal glomerulae. Microautoradiography demonstrated that while p5R bound exclusively to amyloid deposits in the spleen and liver of AA mice, bFGF had a broader binding pattern. Consequently, even though bFGF and p5R both interact with heparan sulfate moieties, p5R binding was restricted to HSPG in amyloid deposits and did not bind HSPG in healthy tissues, whereas bFGF preferentially reacted with HSPG in normal tissue. The data suggest that peptide p5R selectively binds HSPG in amyloid and that the HSPG in healthy tissue, recognized by bFGF, is not targeted by the peptide.

A high-resolution in vivo atlas of the human brain's benzodiazepine binding site of GABAA receptors.

Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the human brain and plays a key role in several brain functions and neuropsychiatric disorders such as anxiety, epilepsy, and depression. For decades, several in vivo and ex vivo techniques have been used to highlight the mechanisms of the GABA system, however, no studies have currently combined the techniques to create a high-resolution multimodal view of the GABA system. Here, we present a quantitative high-resolution in vivo atlas of the human brain benzodiazepine receptor sites (BZR) located on postsynaptic ionotropic GABAA receptors (GABAARs), generated on the basis of in vivo [11C]flumazenil Positron Emission Tomography (PET) data. Next, based on ex vivo autoradiography data, we transform the PET-generated atlas from binding values into BZR protein density. Finally, we examine the brain regional association between BZR protein density and ex vivo mRNA expression for the 19 subunits in the GABAAR, including an estimation of the minimally required expression of mRNA levels for each subunit to translate into BZR protein. This represents the first publicly available quantitative high-resolution in vivo atlas of the spatial distribution of BZR densities in the healthy human brain. The atlas provides a unique neuroscientific tool as well as novel insights into the association between mRNA expression for individual subunits in the GABAAR and the BZR density at each location in the brain.

Organization of the macaque monkey inferior parietal lobule based on multimodal receptor architectonics.

The macaque monkey inferior parietal lobe (IPL) is a structurally heterogeneous brain region, although the number of areas it contains and the anatomical/functional relationship of identified subdivisions remains controversial. Neurotransmitter receptor distribution patterns not only reveal the position of the cortical borders, but also segregate areas associated to different functional systems. Thus we carried out a multimodal quantitative analysis of the cyto- and receptor architecture of the macaque IPL to determine the number and extent of distinct areas it encompasses. We identified four areas on the IPL convexity arranged in a caudo-rostral sequence, as well as two areas in the parietal operculum, which we projected onto the Yerkes19 surface. We found rostral areas to have relatively smaller receptor fingerprints than the caudal ones, which is in an agreement with the functional gradient along the caudo-rostral axis described in previous studies. The hierarchical analysis segregated IPL areas into two clusters: the caudal one, contains areas involved in multisensory integration and visual-motor functions, and rostral cluster, encompasses areas active during motor planning and action-related functions. The results of the present study provide novel insights into clarifying the homologies between human and macaque IPL areas. The ensuing 3D map of the macaque IPL, and the receptor fingerprints are made publicly available to the neuroscientific community via the Human Brain Project and BALSA repositories for future cyto- and/or receptor architectonically driven analyses of functional imaging studies in non-human primates.

Assigning Function to Phylogeny: MAR-FISH.

Microautoradiography (MAR) is a technique by which assimilated radioactive tracers incorporated into the biomass can be detected by a film emulsion. This allows for the testing of cellular preferences in electron donors and acceptors of individual cells in complex microbial assemblages, as well as the ability to take up substrates under diverse environmental exposures.Combination with staining techniques such as fluorescence in situ hybridization (FISH) can be used to identify the involved cells. Here, the practical aspects of a combined microautoradiography and fluorescence in situ hybridization (MAR-FISH) approach are described.

Synthesis and Evaluation of Fluorine-18 Labeled 2-Phenylquinoxaline Derivatives as Potential Tau Imaging Agents.

In this study, three pairs of optically pure 18F-labeled 2-phenylquinoxaline derivatives were evaluated as Tau imaging agents for the diagnosis of Alzheimer's disease (AD). The chiral 2-fluoromethyl-1,2-ethylenediol side chain was attached to the 2-phenylquinoxaline backbone to increase hydrophilicity, thereby improving the binding affinity of the probe to tangles and their selectivity toward Tau tangles over ß-amyloid plaques (Aß). These probes displayed excellent fluorescent properties and high selectivity for tangles on brain sections from transgenic mice (rTg4510) and AD patients. Quantitative binding assays with AD homogenates showed that the probes (R)-5 and (S)-16 have a high affinity (Ki = 4.1 and 10.3 nM, respectively) and high selectivity (30.5-fold and 34.6-fold, respectively) for tangles over Aß. The high affinity and selectivity of (R)-[18F]5 and (S)-[18F]16 for tangles were further confirmed with autoradiography on AD brain tissue in vitro. In addition, they displayed sufficient blood-brain barrier penetration (7.06% and 10.95% ID/g, respectively) and suitable brain kinetics (brain2 min/brain60 min = 10.1, 6.5 respectively) in normal mice. Ex vivo metabolism studies and micro-positron emission computed tomography (PET) revealed high brain biostability, good brain kinetic properties, and low nonspecific binding for (S)-[18F]16. Together, these results demonstrate that (R)-[18F]5 and (S)-[18F]16 are promising PET probes for Tau tangles imaging.

[18F]-sodium fluoride autoradiography imaging of nephrocalcinosis in donor kidneys and explanted kidney allografts.

Nephrocalcinosis is present in up to 43% of kidney allograft biopsies at one-year after transplantation and is associated with inferior graft function and poor graft survival. We studied [18F]-sodium fluoride ([18F]-NaF) imaging of microcalcifications in donor kidneys (n = 7) and explanted kidney allografts (n = 13). Three µm paraffin-embedded serial sections were used for histological evaluation of calcification (Alizarin Red; Von Kossa staining) and ex-vivo [18F]-NaF autoradiography. The images were fused to evaluate if microcalcification areas corresponded with [18F]-NaF uptake areas. Based on histological analyses, tubulointerstitial and glomerular microcalcifications were present in 19/20 and 7/20 samples, respectively. Using autoradiography, [18F]-NaF uptake was found in 19/20 samples, with significantly more tracer activity in kidney allograft compared to deceased donor kidney samples (p = 0.019). Alizarin Red staining of active microcalcifications demonstrated good correlation (Spearman's rho of 0.81, p < 0.001) and Von Kossa staining of consolidated calcifications demonstrated significant but weak correlation (0.62, p = 0.003) with [18F]-NaF activity. This correlation between ex-vivo [18F]-NaF uptake and histology-proven microcalcifications, is the first step towards an imaging method to identify microcalcifications in active nephrocalcinosis. This may lead to better understanding of the etiology of microcalcifications and its impact on kidney transplant function.

GTPγS-Autoradiography for Studies of Opioid Receptor Functionality.

The opioid receptors have been an interesting target for the drug industry for decades. These receptors were pharmacologically characterized in the 1970s and several drugs and peptides have emerged over the years. In 2012, the crystal structures were also demonstrated, with new data on the receptor sites, and thus new possibilities will appear. The role of opioids in the brain has attracted considerable interest in several diseases, especially pain and drug dependence. The opioid receptors are G-protein-coupled receptors (GPCR ) that are Gi coupled which make them suitable for studying the receptor functionality. The [35S]GTP γS autoradiography assay is a good option that has the benefit of generating both anatomical and functional data in the area of interest. It is based on the first step of the signaling mechanism of GPCRs. When a ligand binds to the receptor GTP will replace GDP on the a-subunit of the G-protein, leading to a dissociation of the ßγ-subunit. These subunits will start a cascade of second messengers and subsequently a physiological response.

Development and evaluation of [125 I]IPPI for Tau imaging in postmortem human Alzheimer's disease brain.

OBJECTIVE: Alzheimer's disease (AD) is a neurodegenerative disease characterized by aggregation of Tau protein into paired helical filaments causing neurofibrillary tangles (NFT) in the brain. The aim of this study was to develop and evaluate the effectiveness of a novel radioiodinated tracer, 6-[125 I]iodo-3-(1H-pyrrolo[2,3-c]pyridine-1-yl)isoquinoline ([125 I]IPPI), for binding to Tau protein (Ki = 0.75 nM) in postmortem human brain (AD and cognitively normal (CN). METHODS: Radiosynthesis of [125 I]IPPI was carried out by radioiododestannylation and purified chromatographically. Computational modeling studies of IPPI and MK-6240 binding on Tau fibril were evaluated. In vitro autoradiography studies were carried out with [3 H]PIB for Aß plaques and [125 I]IPPI for Tau in AD and CN brains and evaluate drug effects. RESULTS: [125 I]IPPI was produced in >95% purity. Molecular modeling of IPPI revealed binding energies of IPPI (-7.8, -8.1, -8.2, -7.5 Kcal/mol) at the four sites were comparable to MK-6240 (-8.7, -8.5, -8.3, -7.5 Kcal/mol). Ratio of average grey matter (GM) [125 I]IPPI in AD versus CN was found to be 7.31 (p = .07) and AD GM/ white matter (WM) = 4.35 (p = .09). Ratio of average GM/WM [125 I]IPPI in CN was 1.21. Binding of [125 I]IPPI correlated with the presence of Tau, confirmed by anti-Tau Dako A0024. Specifically bound [125 I]IPPI to Tau in AD brains was displaced by MK-6240 and IPPI (>90%). Monoamine oxidase inhibitors (MAO) inhibitors deprenyl and clorgyline effected [125 I]IPPI binding at >1 µM concentrations. CONCLUSION: [125 I]IPPI exhibited high binding in human AD frontal cortex and anterior cingulate and is a suitable radioiodinated ligand for Tau imaging.

Brief descriptions of the principles of prominent methods used to study the penetration of materials into human hair and a review of examples of their use.

Consumers are attracted to the latest fashion trends and different looks. This drives the search for novel hair treatments. Some chemicals present in hair treatment products can penetrate the hair shaft. These materials can either nourish or injure the hair cortex. Different techniques have been used to investigate the mechanism of molecule penetration and the conditions under which penetration occurs. This article reviews the techniques applied for this purpose. Various microscopy techniques are used to capture clear and colourful images to determine the diffusion pathways and the exact location of the molecules under study. However, the laborious sample preparation often leads to sample destruction since cross-sectioning is often required. While various other techniques have been successfully used for investigating the penetration methods, most of these require different amounts of work to be put in for sample preparation and instrumentation. Several spectroscopic techniques have been used to study the penetration of the molecules because of the high levels of accuracy and the quick response time of these techniques. Moreover, the samples are not damaged during the investigation.

Les consommateurs sont attirés par les dernières tendances et les différents styles de la mode. Cela stimule la recherche pour de nouveaux traitements capillaires. Certains produits chimiques présents dans les produits de soins capillaires peuvent pénétrer la tige du cheveu. Ils peuvent tantôt nourrir, tantôt endommager le cortex pileux. Différentes techniques ont été utilisées pour étudier le mécanisme de pénétration des molécules et les conditions dans lesquelles cette pénétration a lieu. Cet article examine les techniques appliquées à cette fin. Diverses techniques de microscopie sont mises en œuvre pour capturer des images claires et colorées afin de déterminer les voies de diffusion et la localisation exacte des molécules à l'étude. Cependant, la préparation laborieuse des échantillons conduit fréquemment à la destruction des échantillons, car une coupe transversale est souvent exigée. Si plusieurs autres techniques ont été utilisées avec succès pour étudier les méthodes de pénétration, la plupart d'entre elles nécessitent différents niveaux d'activité à mettre en œuvre pour la préparation des échantillons et l'instrumentation. Plusieurs techniques spectroscopiques ont été utilisées pour étudier la pénétration des molécules en raison de leurs niveaux élevés de précision et de leur délai de réponse rapide. De plus, les échantillons ne sont pas endommagés pendant l'investigation.

Dopamine D1 + D3 receptor density may correlate with parkinson disease clinical features.

OBJECTIVE: Dopamine D2-like receptors - mainly dopamine D2 receptors (D2R) and dopamine D3 receptors (D3R) - are believed to be greatly involved in the pathology of Parkinson disease (PD) progression. However, these receptors have not been precisely examined in PD patients. Our aim was to quantitatively calculate the exact densities of dopamine D1 receptors (D1R), D2R, and D3R in control, Alzheimer disease (AD), and Lewy body disease (LBD) patients (including PD, Dementia with Lewy bodies, and Parkinson disease dementia); and analyze the relationship between dopamine receptors and clinical PD manifestations. METHODS: We analyzed the densities of D1R, D2R, and D3R in the striatum and substantia nigra (SN) using a novel quantitative autoradiography procedure previously developed by our group. We also examined the expression of D2R and D3R mRNA in the striatum by in situ hybridization. RESULTS: The results showed that although no differences of striatal D1R were found among all groups; D2R was significantly decreased in the striatum of PD patients when compared with control and AD patients. Some clinical manifestations: age of onset, PD stage, dopamine responsiveness, and survival time after onset; showed a better correlation with striatal D1R + D3R densities combined compared to D1R or D3R alone. INTERPRETATION: There is a possibility that we may infer the results in diagnosis, treatment, and prognosis of PD by detecting D1R + D3R as opposed to using dopamine D1 or D3 receptors alone. This is especially true for elderly patients with low D2R expression as is common in this disease.

Simple methodology for ensuring the precision of measuring radioactivity at low concentrations in very small tissues using quantitative whole-body autoradiography.

Quantitative whole-body autoradiography (QWBA) is largely used to evaluate tissue distribution of small molecule drugs. In QWBA, radioactivity is measured as the intensity obtained from the autoradiogram. It is known that lower intensity per a region of interest (ROI) or smaller size of ROI increases the variability of intensity. In fact, as some tissues are very small (e.g., the choroidea), ensuring reliability on the intensity for measuring radioactivity in these tissues is difficult in case of under- or over-estimation of radioactivity concentration owing to their variation of low radioactivity intensity of ROI. We thus analyzed the relationships between the size, intensity, and precision of ROI to determine the statistically significant lower limit of quantification (LLOQ) in very small tissues. To investigate the difference in correlation between the radiation source (commercial planar radiation standard [com-ST] and self-made radiation standard [self-ST] consisting of radioactive compounds and matrices), apparatus, or setting environment of the apparatus, correlation analysis was conducted under various conditions. Our results revealed that LLOQ can be calculated by simply using the correlation equation because a common relationship was observed between self-ST, which is used in QWBA, and com-ST. This methodology was thus considered valuable for ensuring LLOQ determination in QWBA.

Detection of Radioactive DNA in Polyacrylamide Gels.

Bands of radioactive DNA separated by polyacrylamide gel electrophoresis may be detected by autoradiography or phosphorimaging. Analytical polyacrylamide gels containing radioactive DNA are usually fixed and dried before autoradiography. However, if bands of radioactive DNA are to be recovered from the gel, the gel should generally not be fixed or dried.

Autoradiography and Phosphorimaging.

Many of the commonly used techniques in molecular cloning depend on methods to map accurately the distribution of radioactive atoms on two-dimensional (2D) surfaces. Without this ability, methods such as Southern blotting, northern hybridizations, radiolabeled DNA sequencing, and library screening would not have been possible. In the 1970s and 1980s-the pioneering days of molecular cloning-imaging of 2D surfaces was obtained using autoradiography. In this technique, ß-particles emitted by radioactive specimens were recorded on X-ray film, producing a latent image that can be converted to a true image by developing and fixing the film. Autoradiography was a lot of fun, but it was also messy. In the impatient excitement of wanting to see how an experiment had turned out, people used to hold the newly developed X-ray films in their metal frames up to the darkroom light. Drips of the final wash would run down their arms, clothes would be stained, and shoes ruined. It is hardly surprising that autoradiography was quickly abandoned when sensitive phosphorimagers came onto the market at the end of the 1990s.

Penetration, distribution, and elimination of remofuscin/soraprazan in Stargardt mouse eyes following a single intravitreal injection using pharmacokinetics and transmission electron microscopic autoradiography: Implication for the local treatment of Stargardt's disease and dry age-related macular degeneration.

Age-related macular degeneration (AMD) is the leading cause of blindness in older people in the developed world while Stargardt's disease (SD) is a juvenile macular degeneration and an orphan disease. Both diseases are untreatable and are marked by accumulation of lipofuscin advancing to progressive deterioration of the retinal pigment epithelium (RPE) and retina and subsequent vision loss till blindness. We discovered that a small molecule belonging to the tetrahydropyridoether class of compounds, soraprazan renamed remofuscin, is able to remove existing lipofuscin from the RPE. This study investigated the drug penetration, distribution, and elimination into the eyes of a mouse model for increased lipofuscinogenesis, following a single intravitreal injection. We measured the time course of concentrations of remofuscin in different eye tissues using high-performance liquid chromatography combined with mass spectroscopy (HPLC-MS). We also visualized the penetration and distribution of 3 H-remofuscin in eye sections up to 20 weeks post-injection using transmission electron microscopic (TEM) autoradiography. The distribution of silver grains revealed that remofuscin accumulated specifically in the RPE by binding to the RPE pigments (melanin, lipofuscin and melanolipofuscin) and that it was still detected after 20 weeks. Importantly, the melanosomes in choroidal melanocytes only rarely bind remofuscin emphasizing its potential to serve as an active ingredient in the RPE for the treatment of SD and dry AMD. In addition, our study highlights the importance of electron microscopic autoradiography as it is the only method able to show drug binding with a high intracellular resolution.

Discovery of Diphenoxy Derivatives with Flexible Linkers as Ligands for ß-Amyloid Plaques.

The highly rigid and planar scaffolds with π-conjugated systems have been widely considered to be indispensable for ß-amyloid (Aß) binding ligands. In this study, a library of diphenoxy compounds with different types of more flexible linkers as Aß ligands were synthesized and evaluated. Most of them displayed good affinity (Ki < 100 nM) for Aß1-42 aggregates, and some ligands even showed values of Ki less than 10 nM. Structure-activity relationship analysis revealed that modification on the linkers or substituents tolerated great flexibility, which challenged the long-held belief that rigid and planar structures are exclusively favored for Aß binding. Three ligands were labeled by iodine-125, and they exhibited good properties in vitro and in vivo, which further supported that this flexible scaffold was potential and promising for the development of Aß imaging agents.