Literatura académica sobre el tema "Beta autoradiography"

Background: Autoradiography of tissue with radioactive substance such as Thorotrast by Fuji Computed Radiography (FCR) has been available. We obtained autoradiographs from Thorotrast-deposited tissue by FCR. However, the nature of radiation from tissue with Thorotrast was not certain, because alpha particles are shielded by the plastic front of the FCR cassette. Therefore, we undertook investigation to clearly explain the nature of radiation from Thorotrast in case of autoradiography.Materials and Methods: Tissue blocks of liver and spleen with Thorotrast deposition were imaged by autoradiography using FCR, and radioactivity of tissue blocks was measured by a GM survey meter. Measurement was carried out by both with and without an aluminum plate between the tissue and the surface of GM survey meter to shield beta-rays.Results: Autoradiographs of the liver and spleen with Thorotrast were successful. It took only one day to obtain autoradiograph of the spleen, and 14 days for the liver. The radioactivity count decreased dramatically when an aluminum plate was inserted between the specimen and GM survey meter, but some radiation remained. The tissue blocks were contained in a plastic bag and the front of the Cassette of Imaging Plate is covered by a thin plastic board, so alpha-rays from Thorium dioxide in Thorotrast had been shielded from the beginning.Conclusion: We concluded that the radiation from the tissue blocks with Thorotrast in a plastic bag was mostly from beta-rays and less than 5% of radiation was from gamma-rays from the daughter nuclei of Thorium dioxide.

Probes labeled with 33P have potential for widespread use in in situ hybridization because they are better able to detect relatively scarce mRNAs compared with probes labeled with 35S, but the relatively short half-life of 33P is a disadvantage when it is used as a radioactivity standard for quantitative autoradiography. To determine if plastic sections containing 14C can be used as standards for quantitative autoradiography with 33P, we co-exposed 33P-labeled liver paste sections and 14C-plastic standards to Hyperfilm beta max. The autoradiographic response of Hyperfilm beta max to these isotopes was almost identical. Second-order polynomial equations obtained from analysis of film relative optical density and radioactivity permitted derivation of tissue-equivalent radioactivity from the film optical densities produced by the 14C standards for 1-14-day exposures. These results validate the use of plastic 14C standards for quantifying 33P used in contact film autoradiography.

Chronic hypoxia induces a hyperadrenergic state which down-regulates beta-adrenergic receptors (beta-AR) in the heart. We visualized lung beta-AR binding sites after adaptation to chronic hypoxia by autoradiography of whole lung sections labeled with 50 pM 125I-labeled pindolol. A low concentration of agonist (32 nM isoproterenol) selectively masked beta-ARs with high affinity for agonists. Total specific beta-AR binding increased twofold with hypoxia. In both the control and hypoxic lung sections, 60–70% of the beta-ARs were in a high-affinity state, which could be reversed by guanine nucleotide. Autoradiography revealed a high density of high- and low-affinity beta-AR sites in lung parenchyma, predominantly involving alveolar walls, but also the walls of airways and blood vessels. The distribution of high- and low-affinity beta-AR within the lung was qualitatively identical. Hypoxia increased beta-AR binding without affecting its distribution. The majority of the additional beta-ARs induced during adaptation to chronic hypoxia are in the high-affinity state, and are thus of probable functional significance.

AbstractThe significance of the beta adrenergic system in the nasal mucosa isunclear. The authors have used the technique of autoradiography to localize and classify beta adrenoceptors in human nasal mucosa. The receptors have been found to beexclusively of thebeta-2 subtype and the highest density is found in the glandularducts. It is suggested that the beta-adrenergic system may have a physiologically important role in controlling the electrolyte composition of nasal secretions.

We describe two different techniques with plastic embedding in in situ hybridization histochemistry (ISHH). Their applicability was demonstrated by use of human placenta of the tenth gestational week and a tritium-labeled cDNA probe for the beta-subunit of hCG. In the first method, ISHH was performed on whole pieces of tissue (en bloc ISHH) pretreated with a weak acid solution, embedded in methacrylate, and sectioned at 3 microns for autoradiography. In the second technique, en bloc ISHH was carried out on tissue pre-treated with the weak acid and thereafter with detergent to further facilitate probe penetration. An acrylic resin was used for embedding, and section thickness was reduced to 1 microns. With both techniques, beta hCG cDNA/mRNA hybrids were localized exclusively to the syncytiotrophoblast (ST), in agreement with a previous study using sections of frozen placentas for hybridization to the same probe. However, owing to the higher resolution of the plastic sections the reliability of this localization was greatly increased. The number of autoradiographic grains over the acrylic resin 1-microns sections was found to be considerably higher than that over the methacrylate 3-microns sections. This study showed that treatment of tissue with detergent before en bloc ISHH, with subsequent embedding in acrylic resin and sectioning at 1 microns, gives high resolution in combination with a high signal-to-noise ratio after autoradiography. As the acrylic resin permits cutting of ultrathin sections, the results suggest that the technique may become useful for ISHH studies at the subcellular level.

Previous studies suggest that the desensitization and downregulation of beta 1-adrenergic receptors (beta 1-AR) in the failing heart are the result of the elevated plasma catecholamine levels associated with this disease. To examine norepinephrine (NE)-induced regulation of cardiac adrenergic receptors, rats were infused with l-NE (200 micrograms.kg-1.h-1 for 7 days) or vehicle (0.001 N HCl) by implantation of osmotic minipumps. The technique of coverslip autoradiography was used to quantify alpha 1-adrenergic receptors (alpha 1-AR), beta 1-AR, and beta 2-AR in different tissue compartments of rat hearts. For measurement of beta-AR binding, sections were incubated with 70 pM [125I]iodocyanopindolol (ICYP) alone or in the presence of 5 microM dl-propranolol or 5 x 10(-7) M CGP-20712A (a beta 1-antagonist) and then set up for autoradiography. [3H]prazosin (1 nM) with or without phentolamine was used to study alpha-AR binding. Chronic infusion of NE induced a greater downregulation of beta 2-AR compared with beta 1-AR in all regions studied, including atrial and ventricular myocytes, coronary arterioles, and connective tissue. An 18% loss of beta 1-AR was seen only in atrial myocytes; beta 1-AR density actually increased 28% in ventricular myocytes following NE infusion. There was a 15% decrease in alpha 1-AR in ventricular myocytes, whereas no change in alpha 1-AR density was seen in myocardial arterioles. Our study demonstrates that beta 2-AR are more susceptible to NE-induced downregulation than beta 1-AR. Thus other mechanisms may be involved in the selective downregulation of beta 1-AR in certain forms of heart failure.

This thesis presents three main strands of work concerned with developing digital imaging for high throughput beta autoradiography. These three strands comprise work with the image sensor technology, Monte Carlo simulation and the use of post-acquisition image analysis based on image registration. In this way, the complete autoradiography imaging chain is addressed. CCD and CMOS imaging technologies are presented as potential imaging alternatives to using conventional film in autoradiography. These digital technologies exhibit enhanced sensitivity, dynamic range and linearity compared to film using imaging methods developed at Surrey. These imaging methods address the different sources of noise typically present in CCD and CMOS technologies. Tissue imaging using 3H, 35S and 121I, the typical radioisotopes used by the Drug Addiction Group in the School of Biomedical and Biological Sciences, is presented. The first successful images of 3H-labelled tissue sections using CCD and CMOS technologies operating at room temperature are presented as one of the main achievements of this work. To better understand the image creation process some preliminary Monte Carlo simulations, using the GEANT4 toolkit, have been undertaken, demonstrating intrinsic and extrinsic key parameters of these digital sensors that can be used to optimise spatial resolution. These simulations demonstrate that each radioisotope requires a different optimum detector architecture. In this work these optimum architectures are analysed. To support the high sensitivity (i.e. fast) imaging produced by the sensor technology, automated post-acquisition analysis is also considered, using an atlas-based image registration approach, by previously aligning automatically segmented biological landmarks using a feature-based extraction approach, region growing. This has the potential to speed up the post-acquisition analysis aspects of the imaging chain. Thus a computer-based tool designed to semi-automatically elastically register a radiogram with an atlas has been developed.

Les détecteurs gazeux ont démontré, au cours de ces dernières décennies, leur haute performance pour l'imagerie de particules radioactives, atteignant des résolutions spatiales inférieures à 100 µm. Les propriétés scintillantes de certains mélanges gazeux, combinées au gain important des détecteurs gazeux et à l'usage d'une caméra à bas bruit électronique, ont permis d'utiliser la lumière scintillée pour l'imagerie. Cette approche permet d'obtenir une large surface de détection et une haute résolution spatiale tout en réalisant l'imagerie en temps réel à un coût par pixel réduit, avec une faible complexité d'analyse des données. Les principaux objectifs de cette thèse sont d'optimiser la résolution spatiale ainsi que la sensibilité du détecteur, soit par une méthode d'acquisition "événement par événement" avec des temps d'acquisition d'image courts, soit par "intégration" avec des temps d'acquisition longs.Un détecteur Micromegas en verre innovant pour la lecture optique a été développé, tirant parti de la haute résolution spatiale inhérente au détecteur Micromegas.L'adaptabilité du gain du détecteur Micromegas liée au mécanisme d'amplification par avalanche, lui permet de couvrir une large gamme de flux et d'énergies de particules. Durant cette thèse, des mesures d'imagerie ont été réalisées à l'aide de sources avec des niveaux de radioactivité inférieurs à un Becquerel et des énergies de quelques keV, jusqu'à des flux caractéristiques d'un synchrotron et d'une source de spallation, avec des énergies dépassant le MeV.Le rendement lumineux du détecteur a été étudié pour différents mélanges gazeux et pour diverses valeurs de gain sous irradiation aux rayons-X afin d'optimiser la sensibilité du détecteur. L'homogénéité et la précision de la réponse du détecteur ont été caractérisées par radiographie à rayons-X. La Fonction d'Étalement du Point (PSF) du Micromegas à lecture optique a été mesurée à l'aide d'un faisceau de rayons-X parallèles de quelques microns d'épaisseur, générés par le rayonnement synchrotron. Cette mesure a permis de déterminer la résolution spatiale du détecteur pour différentes configurations et d'identifier et de quantifier les effets qui rentrent en jeux. L'impact de la microgrille et des piliers sur la réponse en scintillation du détecteur a également été observé et quantifié.Deux applications ont été choisies afin d'illustrer le potentiel du Micromegas à lecture optique: l'autoradiographie pour la quantification d'échantillons tritiés de très faible activitié et la radiographie neutronique à haute résolution en environnement hautement radioactif.L'autoradiographie et le comptage radioactif de rayonnements beta faiblement énergétiques ont été réalisés avec des échantillons de glucose tritié. Des activités inférieures à un Becquerel ont été mesurées avec précision et simultanément sur un grand nombre d'échantillons tout en assurant une reconstruction précise de leur position. Ce travail valide la possibilité de quantifier la concentration de médicaments anticancéreux à l'échelle de cellules tumorales uniques.Enfin, l'utilisation du Micromegas à lecture optique pour la neutronographie a été démontrée en utilisant une source de spallation produisant des neutrons thermiques à un flux d'environ 10⁸ n. s⁻¹cm⁻ ² mA⁻¹. L'uniformité de la réponse du détecteur a été étudiée, et les effets de la diffusion et du parcours moyen des particules dans le gaz sur la netteté de l'image ont été mesurés et comparés à une simulation. Une résolution spatiale de l'ordre de 400 µm a été obtenue en utilisant une amplification à double étages au sein du détecteur Micromegas
Gaseous detectors have demonstrated, over the past decades, their high performance for imaging radioactive particles, achieving spatial resolutions below 100 µm. The scintillating properties of certain gas mixtures, combined with the significant gain of gaseous detectors and the use of a low-noise camera, have enabled the use of scintillation light for imaging. This approach allows for a large detection surface and high spatial resolution while achieving real-time imaging at a low cost per pixel, with low data analysis complexity. The main objectives of this thesis are to optimize the spatial resolution and sensitivity of the detector, either by an "event-by-event" acquisition method with short image acquisition times or by "integration" with long acquisition times.An innovative glass Micromegas detector for optical readout has been developed, taking advantage of the inherently high spatial resolution of the Micromegas detector. The adaptability of the Micromegas detector's gain, due to the avalanche amplification mechanism, allows it to cover a wide range of particle fluxes and energies. During this thesis, imaging measurements were performed using sources with radioactivity levels below one Becquerel and energies of a few keV, up to fluxes characteristic of a synchrotron and a spallation source, with energies exceeding one MeV.The light yield of the detector was studied for different gas mixtures and various gain values under X-ray irradiation to optimize the detector's sensitivity. The homogeneity and precision of the detector's response were characterized by X-ray radiography. The Point Spread Function (PSF) of the optical readout Micromegas was measured using a parallel X-ray beam a few microns thick, generated by synchrotron radiation. This measurement allowed us to determine the detector's spatial resolution for different configurations and to identify and quantify the effects involved. The impact of the micro-mesh and pillars on the detector's scintillation response was also observed and quantified.Two applications were chosen to illustrate the potential of the optical readout Micromegas: autoradiography, for the quantification of very low-activity tritiated samples and high-resolution neutron radiography in highly radioactive environments.Autoradiography and radioactive counting of low-energy beta radiation were performed with tritiated glucose samples. Activities below one Becquerel were measured accurately and simultaneously on a large number of samples, while ensuring precise reconstruction of their position. This work validates the possibility of quantifying the concentration of anticancer drugs at the scale of single tumor cells.Finally, the use of the optical readout Micromegas for neutron imaging was demonstrated using a spallation source which produces thermal neutrons with a flux of approximately 10⁸ n. s⁻¹cm⁻ ² mA⁻¹. The uniformity of the detector's response was studied, and the effects of the diffusion and the mean free path of particles in the gas on image sharpness were measured and compared to a simulation. A spatial resolution on the order of 400 µm was achieved using double-stage amplification within the Micromegas detector

The cyanobacterial amino acid β-N-methylamino-L-alanine (BMAA) is a neurotoxin implicated in the etiology of neurodegenerative diseases. Cyanobacteria are cosmopolitan organisms present in various environments. BMAA can cause long-term neurodegenerative alterations in rats exposed during the neonatal period, a period that corresponds to the last trimester and the first few years of life in humans. As BMAA has been reported to be bioaccumulated in the aquatic food chain and detected in mussels, crayfish and fish used for human consumption, the main aim of this thesis has been to investigate the final step in the mammalian food-chain, i.e. the transfer of BMAA into breast milk. Autoradiographic imaging and mass spectrometry analysis showed an enantiomer-selective uptake of BMAA and that the neurotoxin was transferred from lactating mice and rat, via the milk, to the brain of the nursed pups. The results show that transport of BMAA may be disproportional to dose. In addition, BMAA was found present both as free amino acid and tightly associated to proteins in rat brains. Surprisingly, however, no association to milk proteins was found. In vitro studies of murine (HC11) and human (MCF7) mammary epithelial cells suggest that BMAA can pass the human mammary epithelium into milk. Additional transport studies on human intestinal, glioblastoma and neuroblastoma cells showed that L-BMAA was consistently favored over D-BMAA and that the transport was mediated by several amino acid transporters. We also demonstrated that egg-laying quail transfer BMAA to its offspring by deposition in the eggs, particularly in the yolk but also in the albumen. Furthermore, comparative analysis of carboxyl- and methyl-labeled [14C]-BMAA suggested that BMAA was not metabolized to a large degree. Altogether, the results indicate that BMAA can be transferred from mothers, via the milk, to the brain of nursed human infants. Determinations of BMAA in mothers’ milk and cows’ milk are therefore warranted. We also propose that birds’ eggs could be an additional source of BMAA exposure in humans. It might therefore be of concern that mussels are increasingly used as feed in commercial egg production.

L’autoradiographie b est une technique d’imagerie médicale qui permet de visualiser la localisation de molécules marquées avec des traceurs radioactifs émetteurs b dans des coupes histologiques. Cette technique est largement employée dans les domaines de la biologie cellulaire ou de la pharmacologie. Le développement de la technologie des détecteurs gazeux à structure PIM au laboratoire Subatech a permis d’aboutir à la conception d’un appareil d’imagerie b de très haute résolution spatiale (20 µm FWHM) réalisant des images d’une demi lame histologique sur des émetteurs de basses énergies comme du 3H ou de 14C. Le développement récent d’une nouvelle approche concernant la méthode de reconstruction du point d’émission permet d’élargir le champ d’application aux émetteurs de hautes énergies tels que l’131I, le 18F ou le 46Sc. Un nouveau dispositif de grande surface (18x18 cm2), compact et conçu pour l’utilisateur final a été mis au point. Il permet désormais l’imagerie de 10 lames de microscope simultanément. Grâce à une solution de multi-modalité, il conserve les bonnes caractéristiques de résolutions spatiales acquises précédemment en l’étendant sur une grande surface d’analyse. Différentes formes d’échantillons comme des coupes sur lames de microscope ou sur rubans adhésifs peuvent ainsi être analysés. Les simulations et les expérimentations menées durant cette thèse ont permis d’aboutir à un agencement optimal des structures composant le détecteur. La caractérisation et les résultats ont montré que la structure PIM est une structure à considérée dans le cadre de l’imagerie b de haute résolution sur différents types d’émetteurs
The b autoradiography is a widely used technique in pharmacology or biological fields. It is able to locate in two dimensions molecules labeled with beta emitters. The development of a gaseous detector incorporating micromesh called PIM in the Subatech laboratory leads to the construction of a very high spatial resolution apparatus dedicated to b imaging. This device is devoted to small analysis surface of a half microscope slide in particular of 3H or 14C and the measured spatial resolution is 20 µm FWHM. The recent development of a new reconstruction method allows enlarging the field of investigation to high energy beta emitters such as 131I, 18F or 46Sc. A new device with a large active area of 18x18 cm2 has been built with a user friendly design. This allows to image simultaneously 10 microscope slides. Thanks to a multi-modality solution, it retains the good characteristics of spatial resolution obtained previously on a small surface. Moreover, different kinds of samples, like microscope slides or scotches can be analysed. The simulation and experimentation work achieved during this thesis led to an optimal disposition of the inner structure of the detector. These results and characterization show that the PIM structure has to be considered for a next generation of b-Imager

Radioactive waste management is nowadays, after nearly 50 years of concern, a technical and economical challenge faced by existing nuclear power countries. In decommissioning of nuclear facilities after removal of the nuclear equipment (laboratory materials, glove boxes, etc.), the radioactive inventory of the various building materials is needed to state the working condition for dismantling. Thus, characterization is essential for decommissioning and moreover for radioactive waste classification and management. A radionuclide imaging technique, the Digital Autoradiography (DA), also known as storage phosphor technology, has been studied for decommissioning projects because of its advantages such low price, easy utilization and sensitivity. DA has been proven to be an efficient technic in localization of beta emitter (especially C-14 and H-3) contamination remaining in nuclear facilities under dismantling. Samples have been collected where C-14 or H-3 have been observed by DA and analyzed by the classical technique : pyrolysis followed by liquid scintillation counting. Real applications to classify potential waste coming from a laboratory under dismantling are described in this paper.