Autoradiographic Techniques Research Articles

Optical density of high fluence autoradiographic images to study boron microdistribution: validation of the technique in tissue sections

The distribution of boron in biological samples coming from BNCT protocols can be determined by the analysis of autoradiographic images formed by nuclear tracks on polymeric detectors. The tissue section is first explored to delimit regions of interest (ROIs), and then it is removed in order to reveal nuclear tracks through an etching process. A quantitative autoradiographic technique was developed to measure the boron concentration in the sample by counting the nuclear tracks on the detector. However, under certain circumstances, rapid measurements of boron distribution are required. For that purpose, a methodology was developed, allowing a rapid and easy determination of boron concentration and distribution in a tissue section by measuring grey levels in the corresponding high fluence autoradiographic image (HFA). The grey levels are then converted to optical density values which are then correlated with boron concentration values. In order to validate the technique, consecutive sections of several tissue samples were analyzed by the conventional counting method and by HFA. The image analysis and boron concentration estimation can be carried out in under 15 min, and relative differences between zones can be easily determined.

18F]-FDG uptake in brain slices prepared from an aged mouse model of Alzheimer's disease using a dynamic autoradiography technique.

2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography ([18F]-FDG-PET) is a imaging modality that has been used to measure of glucose metabolism in the brain in Alzheimer's disease (AD). Clinically, decreased glucose uptake has been reported in the brain of AD, although the precise underlying mechanisms have not yet been elucidated. To elucidate the mechanisms of decreased [18F]-FDG uptake in the AD by PET, [18F]-FDG uptake in the brain of aged model mouse of AD was investigated using a dynamic autoradiography technique "bioradiography". A X-ray phase-contrast imaging (X-PCI) and a histopathological evaluation were also investigated to elucidate the mechanisms underlying the relationships between decreased [18F]-FDG uptake and the pathological changes in the brain of AD mouse. In this study, AD model mouse (5XFAD, APP+/PS1+) were used. [18F]-FDG-bioradiography was conducted in fresh slices of brain tissue under the condition of resting (slices immersed in 5mM K+ solution) and metabolically active (in 50mM K+ solution). Amyloid β42 (Aβ42) deposition in the brain of AD mouse was confirmed by X-PCI. In addition, the positive cells of phosphated tau protein (P-tau) and deposition of Aβ42 were also examined by immunohistochemical staining. No significant differences were observed between the two groups in the resting condition. In the activate condition of the brain, [18F]-FDG uptake was significantly decreased in AD mice compared to WT mice. In X-PCI showed Aβ deposition in the AD mouse, but not in the WT. The AD mouse also showed increased P-tau, accumulation of Aβ42, increase in neuronal apoptosis, and decrease in the number of neurons than that of the WT mouse. Neuronal damage, and induction of neuronal apoptosis, decreased [18F]-FDG uptake, increased Aβ accumulation and P-tau induced neurofibrillary degeneration are observed in AD mouse. In clinical diagnosis, reduction of [18F]-FDG uptake by PET is one of the means of diagnosing the onset of AD. Our results suggest that decreased uptake of [18F]-FDG in the brains of AD may be associated with neuronal dysfunction and cell death in the brain.

The α-synuclein PET tracer [18F] ACI-12589 distinguishes multiple system atrophy from other neurodegenerative diseases

A positron emission tomography (PET) tracer detecting α-synuclein pathology will improve the diagnosis, and ultimately the treatment of α-synuclein-related diseases. Here we show that the PET ligand, [18F]ACI-12589, displays good in vitro affinity and specificity for pathological α-synuclein in tissues from patients with different α-synuclein-related disorders including Parkinson’s disease (PD) and Multiple-System Atrophy (MSA) using autoradiography and radiobinding techniques. In the initial clinical evaluation we include 23 participants with α-synuclein related disorders, 11 with other neurodegenerative disorders and eight controls. In vivo [18F]ACI-12589 demonstrates clear binding in the cerebellar white matter and middle cerebellar peduncles of MSA patients, regions known to be highly affected by α-synuclein pathology, but shows limited binding in PD. The binding statistically separates MSA patients from healthy controls and subjects with other neurodegenerative disorders, including other synucleinopathies. Our results indicate that α-synuclein pathology in MSA can be identified using [18F]ACI-12589 PET imaging, potentially improving the diagnostic work-up of MSA and allowing for detection of drug target engagement in vivo of novel α-synuclein targeting therapies.

Biodistribution of Lipid 5, mRNA, and Its Translated Protein Following Intravenous Administration of mRNA-Encapsulated Lipid Nanoparticles in Rats.

RNA-based therapeutics and vaccines represent a novel and expanding class of medicines, the success of which depends on the encapsulation and protection of mRNA molecules in lipid nanoparticle (LNP)-based carriers. With the development of mRNA-LNP modalities, which can incorporate xenobiotic constituents, extensive biodistribution analyses are necessary to better understand the factors that influence their in vivo exposure profiles. This study investigated the biodistribution of heptadecan-9-yl 8-((2-hydroxyethyl)(8-(nonyloxy)-8-] oxooctyl)amino)octanoate (Lipid 5)-a xenobiotic amino lipid- and its metabolites in male and female pigmented (Long-Evans) and nonpigmented (Sprague Dawley) rats by using quantitative whole-body autoradiography (QWBA) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques. After intravenous injection of Lipid 5-containing LNPs, 14C-containing Lipid 5 ([14C]Lipid 5) and radiolabeled metabolites ([14C]metabolites) were rapidly distributed, with peak concentrations reached within 1 hour in most tissues. After 10 hours, [14C]Lipid 5 and [14C]metabolites concentrated primarily in the urinary and digestive tracts. By 24 hours, [14C]Lipid 5 and [14C]metabolites were localized almost exclusively in the liver and intestines, with few or no concentrations detected in non-excretory systems, which is suggestive of hepatobiliary and renal clearance. [14C]Lipid 5 and [14C]metabolites were completely cleared within 168 hours (7 days). Biodistribution profiles were similar between QWBA and LC-MS/MS techniques, pigmented and nonpigmented rats, and male and female rats, excluding the reproductive organs. In conclusion, the rapid clearance through known excretory systems, with no evidence of redistribution for Lipid 5 or accumulation of [14C]metabolites, provides confidence for the safe and effective use of Lipid 5-containing LNPs. Significance Statement This study demonstrates the rapid, systemic distribution of intact and radiolabeled metabolites of Lipid 5, a xenobiotic amino lipid component of novel mRNA-LNP medicines, and its effective clearance without substantial redistribution after intravenous administration; additionally, findings were consistent between different mRNAs encapsulated within LNPs of similar composition. This study confirms the applicability of current analytical methods for lipid biodistribution analyses, and taken together with appropriate safety studies, supports the continued use of Lipid 5 in mRNA-medicines.

Measurement of an evaporation coefficient in tissue sections as a correction factor for 10B determination.

Boron neutron capture therapy (BNCT) is a cancer treatment option that combines preferential uptake of a boron compound in tumors and irradiation with thermal neutrons. For treatment planning, the boron concentration in different tissues must be considered. Neutron autoradiography using nuclear track detectors (NTD) can be applied to study both the concentration and microdistribution of boron in tissue samples. Histological sections are obtained from frozen tissue by cryosectioning. When the samples reach room temperature, they undergo an evaporation process, which leads to an increase in the boron concentration. To take this effect into account, certain correction factors (evaporation coefficients, CEv) must be applied. With this aim, a protocol was established to register and analyze mass variation of tissue sections, measured with a semimicro scale. Values of ambient temperature, pressure, and humidity were simultaneously recorded. Reproducible results of evaporation curves and CEv values were obtained for different tissue samples, which allowed the systematization of the procedure. This study could contribute to a more precise determination of boron concentration in tissue samples through the neutron autoradiography technique, which is of great relevance to make dosimetric calculations in BNCT.

Composite films based on polyacrylonitrile and detonation nanodiamonds

The properties of composite films based on polyacrylonitrile and detonation nanodiamonds were studied. It was established that the surface properties of the films (roughness and free surface energy) do not change when nanodiamonds are added. It was shown by autoradiography technique with tritium-labeled nanodiamonds that the distribution of particles in a film depends on the modification of their surface. Additives of particles and heat treatment affect the mechanical behaviour of the films, the samples become more brittle. Modification of the nanodiamonds with perfluorononanoic acid leads to a decrease in the strength of the films.

Stabilisation of Malmi soft clay with traditional and low-CO2 binders

Deep soil mixing (DSM), a soil improvement method, is a carbon-intensive activity due to the traditional use of lime and cement as soil binders, which generate large carbon emissions during their production. There is, thus, a growing need for the decarbonisation of infrastructure construction activities, such as DSM, as European cities work towards their carbon-neutrality goals. This paper presents a case study where soft, sensitive postglacial clay from northeast Helsinki is stabilised with the traditional lime-cement (50:50) binder and six alternative low-carbon binders. The low-carbon binders are composed of reduced lime and cement quantities and/or different by-products that include Lime Kiln Dust (LKD), biomass-based fly-ash from bioenergy production, blast furnace slag and the mineral gypsum. The effects of the stabilisation of the alternative binders on the studied clay are evaluated through the results from drained triaxial tests. The lime-cement (50:50) binder is then used as a reference to evaluate the performance of the alternative binders. Additionally, the porosity and porosity distribution of selected stabilised samples were evaluated with the autoradiography technique (AG). Four of the alternative binders showed similar strength levels, at the same confining pressures after 28 days of curing, when compared with the reference binder. Moreover, a higher strength development than the reference binder was observed after 60 days in binders such as the partially LKD-based binder and the gypsum-quicklime-cement mix. Likewise, similar effects of confinement on volumetric behaviour and ductility were exhibited by the binders with comparatively higher strength. Last, results from the AG also showed similarities in terms of porosity and porosity distribution among the stabilised samples with reference and selected low-carbon binders. In general, results show that the inclusion of alternative and side streams material in DSM has the potential to be a more ecological solution with high binding efficiency for soft and sensitive clay improvement.

PO18: An Efficient and Reproducible Autoradiography Technique for HDR-Gynecological Applicators Commissioning

<h3>Purpose</h3> High Dose Rate (HDR) brachytherapy commissioning of Elekta's gynecological (Gyn) applicator sets include a large inventory of CT/MR compatible plastic, applicator tubes of varying shapes and sizes. This often present a challenge to the efficiency of source autoradiography - an essential test to determine and verify final dwell position of the HDR source and its positioning/stepping accuracy. We present a technique of acquiring radiograph-autoradiograph combinations of HDR-Gyn applicators that allows testing of several applicators simultaneously, in a rigid and reproducible set-up. <h3>Materials Methods</h3> Elekta provides x-ray catheter (marker) sets as a required accessory to verify source positioning inside Gyn applicators. Once the markers are calibrated & Final Marker Position (FMP) characterized, using Elekta's Source Position Check Ruler & CT-scans, the technique of radiograph-autoradiograph superposition is recommended for determination of final dwell position (FDP) & verification of source positioning accuracy. To ensure a rigid & reproducible set-up, template trays to hold multiple applicator tubes & Gafochromic EBT3 film for recording multiple radiographs in unison were built using Styrofoam. Channels were carved in styrofoam creating tight narrow groves fitting applicators in place. Applicators were taped with tips laid flat & flush with the film secured to styrofoam base independently. Primary advantage of using styrofoam is that it offers no backscatter to radiography as well as gamma photons from the Ir-192 source. Additionally, it is readily available and easy to work with. Each tray held 4-6 applicators with markers allowing a simultaneous radiograph acquisition, &∼ 5 cm lateral spacing enabled independent images. Truebeam^TM Linear accelerator was used for radiography. Multiple pre-prepared template trays with applicators were exposed at a source-to-film-distance of 100 cm with 400 monitor units using 2.5 MV imaging beam. This technique provided best visualization of the plastic applicator & marker on a gafochromic EBT3 film. Once the multiple-applicator-radiograph is acquired, templates were transported to adjacent HDR suite, set on a rigid couch, markers carefully removed & transfer tube connected for acquisition of autoradiograph coincident with recently acquired radiograph, using Flexitron afterloader. For Ir-192 source's autoradiograph, a 10-15 seconds dwell time is adequate to darken film with marker visualization reasonably intact for analysis. Pre-prepared templates and availability of personnel allowed simultaneous use of linear accelerator & afterloader, for radiograph & autoradiograph acquisition, adding further efficiency. Source positioning & stepping accuracy was verified by coincidence of center of darkening at the exposed dwell-position & center of visualized markers, on a viewbox illuminator. <h3>Results</h3> Using techniques and workflow developed, 60 CT/MR compatible HDR-Gyn plastic applicators were commissioned. Autoradiography-radiography superposition with x-ray markers enabled verification of Elekta specified distances between the outer tip of the IU/ovoid tubes, inner tip & the final dwell position, & HDR source positioning & stepping accuracy within 1 mm. Figure 1-A shows Styrofoam templates with multiple channels for affixing applicators over EBT3 Gafochromic film for radiography, 1-B is HDR room setup for autoradiography and 1-C shows images of multiple different applicator tubes depicting the radiograph-autoradiograph overlay with marker visualization and HDR source positioning. <h3>Conclusion</h3> We present an efficient autoradiography technique for commissioning of a large inventory HDR-Gyn plastic applicators using a linear accelerator & HDR afterloader.

The development of [18F]ACI‐12589, a high affinity and selective alpha‐synuclein radiotracer, as a biomarker for Parkinson’s disease and other synucleinopathies

AbstractBackgroundParkinson’s disease (PD) and other alpha‐synucleinopathies are characterized by the progressive accumulation of alpha‐synuclein (a‐syn) inclusions in the brain, which start in the pre‐motor stage of the disease and correlates with its severity. An imaging agent for a‐syn could allow differential diagnosis and support interventional trails. AC Immune has developed and is currently testing in a first in human (FiH) clinical trial the recently discovered compound, ACI‐12589, as a PET tracer with high affinity and selectivity for a‐syn.MethodScreening of our conformation‐specific, small‐molecular weight MorphomerTM library was followed by an iterative medicinal chemistry optimization program. The primary screening strategy included the development and use of a proprietary binding assay, that importantly involved aggregates derived from PD brain samples. Autoradiography experiments performed with human tissue samples from different alpha‐synucleinopathies provided target engagement and signal specificity data. Autoradiography techniques were also employed to assess selectivity, using tissue samples from Alzheimer’s disease or Frontotemporal lobar degeneration‐TDP donors. Selected compounds were 18F radiolabeled and evaluated for their pharmacokinetics in non‐human primates (NHPs) before proceeding to clinical studies.ResultRecent optimization efforts have led to the identification of several new, highly promising chemical scaffolds. From these, the compound ACI‐12589, has emerged with highly favorable characteristics including low nanomolar affinity and excellent target occupancy in saturation binding experiments using PD brain homogenates. Using high‐resolution autoradiography, ACI‐12589 illustrates target engagement across multiple alpha‐synucleinopathies including PD, Multiple System Atrophy, and Dementia with Lewy Bodies. In classical autoradiography experiments, ACI‐12589 demonstrates significantly higher specific signal in diseased versus non‐diseased tissue samples. Furthermore, ACI‐12589 has at least 30‐fold selectivity versus Abeta and shows no binding to Tau nor TDP‐43 aggregates. Studying [18F]ACI‐12589 in NHPs reveals rapid brain uptake and quick wash out. ACI‐12589 was considered safe in the IND‐enabling toxicology study allowing advancement into the FiH clinical study.ConclusionBased on experience with other tracers, [18F]ACI‐12589 meets the target product profile deemed necessary of a highly favorable candidate to succeed as a radiotracer for imaging a‐syn inclusions. As such, [18F]ACI‐12589 has advanced into the First in Human clinical trial in patients with Parkinson’s disease to be followed by evaluation in other alpha‐synucleinopathies.

Fluorescence-Activated Cell Sorting-Radioligand Treated Tissue (FACS-RTT) to Determine the Cellular Origin of Radioactive Signal

Glial cells probably have a considerable implication in the pathophysiology of neurodegenerative disorders, such as Alzheimer's disease (AD). Their alterations are perhaps associated with a pro-inflammatory state. The TgF344-AD rat strain has been designed to express human APP and human PS1ΔE9 genes, encoding for amyloid proteins Aβ-40 and Aβ-42 and displays amyloid pathology and cognitive deficits with aging. The TgF344-AD rat model is used in this study to evaluate the cellular origin of the 18 kDa translocator protein (TSPO, a marker of glial cell activation) binding, and the 5HT2A-receptor (5HT2AR) serotonin receptor levels that are possibly disrupted in AD. The technique presented here is Fluorescence-Activated Cell Sorting to Radioligand Treated Tissue (FACS-RTT), a quantitative cell-type-specific technique complementary to in vivo PET or SPECT or ex vivo/in vitro autoradiography techniques. It quantifies the same radiolabeled tracer used prior for imaging, using a γ counter after cytometry cell sorting. This allows determining the cellular origin of the radiolabeled protein with high cellular specificity and sensitivity. For example, studies with FACS-RTT showed that (i) the increase in TSPO binding was associated with microglia in a rat model of lipopolysaccharide (LPS)-induced neuroinflammation, (ii) an increase in TSPO binding at 12- and 18-months was associated with astrocytes first, and then microglia in the TgF344-AD rats compared to wild type (WT) rats, and (iii) the striatal density of 5HT2AR decreases in astrocytes at 18 months in the same rat AD model. Interestingly, this technique can be extended to virtually all radiotracers.

HIF-1α affects sensitivity of murine squamous cell carcinoma to boron neutron capture therapy with BPA

Purpose To examine whether hypoxia and Hif-1α affect sensitivity of murine squamous cell carcinoma cells to boron neutron capture therapy (BNCT). Materials and methods SCC VII and SCC VII Hif-1α-deficient mouse tumor cells were incubated under normoxic or hypoxic conditions, and cell survival after BNCT was assessed. The intracellular concentration of the 10B-carrier, boronophenylalanine-10B (BPA), was estimated using an autoradiography technique. The expression profile of SLC7A5, which is involved in the uptake of BPA, and the amount of DNA damage caused by BNCT with BPA were examined. A cell survival assay was performed on cell suspensions prepared from tumor-bearing mice. Results Hypoxia ameliorated SCC VII cell survival after neutron irradiation with BPA, but not BSH. Hypoxia-treated SCC VII cells showed decreased intracellular concentrations of BPA and the down-regulated expression of the SLC7A5 protein. BPA uptake and the SLC7A5 protein were not decreased in hypoxia-treated Hif-1α-deficient cells, the survival of which was lower than that of SCC VII cells. More DNA damage was induced in SCC VII Hif-1α-deficient cells than in SCC VII cells. In experiments using tumor-bearing mice, the survival of SCC VII Hif-1α-deficient cells was lower than that of SCC VII cells. Conclusion. Hypoxia may decrease the effects of BNCT with BPA, whereas the disruption of Hif-1α enhanced sensitivity to BNCT with BPA.

Colocalization of tracks from boron neutron capture reactions and images of isolated cells

In Boron Neutron Capture Therapy, the boronated drug plays a leading role in delivering a lethal dose to the tumour. The effectiveness depends on the boron macroscopic concentration and on its distribution at sub-cellular level. This work shows a way to colocalize alpha particles and lithium ions tracks with cells. A neutron autoradiography technique is used, which combines images of cells with images of tracks produced in a solid-state nuclear track detector.

Neutron autoradiography to study the microdistribution of boron in the lung

In Argentina, a multi-institutional project has been established to assess the feasibility of applying BNCT ex-situ to the treatment of patients with multiple metastases in both lungs. Within this context, this work aims at applying the neutron autoradiography technique to study boron microdistribution in the lung. A comprehensive analysis of the different aspects for the generation of autoradiographic images of both normal and metastatic BDIX rat lungs was achieved. Histology, boron uniformity, optimal tissue thickness and water content in tissue were explored for the two types of samples. A qualitative and a quantitative analysis were performed. No heterogeneities in uptake were observed in normal lung. Conversely, samples with metastasis showed preferential boron uptake in the tumour areas with respect to surrounding tissue. Surrounding tissue would present a slightly higher uptake of boron than the normal lung. Quantitative results of boron concentration values and ratios determined by neutron autoradiography were obtained. In order to contribute to BNCT dosimetry, further analysis increasing the number of samples is warranted.

Ventral striatum regulates behavioral response to ethanol and MDMA combination.

Our previous studies consistently showed that MDMA-induced locomotor hyperactivity is dramatically increased by coadministration of ethanol (EtOH) in rats, indicating possible potentiation of MDMA abuse liability. Thus, we aimed to identify the brain region(s) and neuropharmacological substrates involved in the pharmacodynamics of this potentiation. We first showed that potentiation of locomotor activity by the combination of ip administration of EtOH (1.5 g/kg) and MDMA (6.6 mg/kg) is delay sensitive and maximal when both drugs are injected simultaneously. Then, we used the 2-deoxyglucose quantitative autoradiography technique to assess the impact of EtOH, MDMA, or their combination on local cerebral metabolic rates for glucose (CMRglcs). We showed a specific metabolic activation in the ventral striatum (VS) under MDMA + EtOH versus MDMA or EtOH alone. We next tested if reversible (tetrodotoxin, TTX) or permanent (6-hydrodoxyopamine, 6-OHDA) lesion of the VS could affect locomotor response to MDMA and MDMA + EtOH. Finally, we blocked dopamine D1 or glutamate NMDA receptors in the VS and measured the effects of MDMA and MDMA + EtOH on locomotor activity. We showed that bilateral reversible inactivation (TTX) or permanent lesion (6-OHDA) of the VS prevented the potentiation by EtOH of MDMA-induced locomotor hyperactivity. Likewise, blockade of D1 or NMDA receptors in the VS also reduced the potentiation of MDMA locomotor activity by EtOH. These data indicate that dopamine D1 and glutamate NMDA receptor-driven mechanisms in the VS play a key role in the pharmacodynamics of EtOH-induced potentiation of the locomotor effects of MDMA.

Uranium Traps in Phreatic Sandstone-type Prospect, Taunsa Area, Dera Ghazi Khan, Eastern Sulaiman Range, Pakistan: Evidences from Autoradiography and Optical Microscopy

Taunsa uranium occurrence like other uranium resources in Pakistan is hosted by the Late Miocene-Pliocene age Litra Formation of the Siwalik Group molasse sediments. Taunsa uranium prospect is a unique phreatic-type uranium resource in terms of its disturbed geological setting of the eastern limb of the Zindapir anticline in the eastern Sulaiman range. Autoradiography technique was used to locate the spots of anomalous uranium concentration in thin sections from ore of Taunsa prospect. Twenty polished thin sections from uranium ore ranging from 200 ppm-600 ppm were attached to detectors for a month which produced prominent alpha track which were used to find the traps of uranium. Subsequently, these spots were studied under SEM and EPMA for further investigations of uranium phases. Autoradiography revealed that Taunsa uranium ore is mostly associated with organic matter (probably petroleum), black shale clasts, biotite, fougerite (a green colour rusty mineral) and with micritic clasts. This study suggests that prospective facies of the host sandstone containing relatively abundant black shale clasts, organic matter and biotite may be targeted during exploratory drilling in Taunsa uranium deposit and its extensions in the eastern limb of Zindapir anticline

Uranium Traps in Phreatic Sandstone-type Prospect, Taunsa Area, Dera Ghazi Khan, Eastern Sulaiman Range, Pakistan: Evidences from Autoradiography and Optical Microscopy

Taunsa uranium occurrence like other uranium resources in Pakistan is hosted by the Late Miocene-Pliocene age Litra Formation of the Siwalik Group molasse sediments. Taunsa uranium prospect is a unique phreatic-type uranium resource in terms of its disturbed geological setting of the eastern limb of the Zindapir anticline in the eastern Sulaiman range. Autoradiography technique was used to locate the spots of anomalous uranium concentration in thin sections from ore of Taunsa prospect. Twenty polished thin sections from uranium ore ranging from 200 ppm-600 ppm were attached to detectors for a month which produced prominent alpha track which were used to find the traps of uranium. Subsequently, these spots were studied under SEM and EPMA for further investigations of uranium phases. Autoradiography revealed that Taunsa uranium ore is mostly associated with organic matter (probably petroleum), black shale clasts, biotite, fougerite (a green colour rusty mineral) and with micritic clasts. This study suggests that prospective facies of the host sandstone containing relatively abundant black shale clasts, organic matter and biotite may be targeted during exploratory drilling in Taunsa uranium deposit and its extensions in the eastern limb of Zindapir anticline

Comparison of phosphor screen autoradiography and micro-pattern gas detector based autoradiography for the porosity of altered rocks

This study aims to further develop the 14C-PMMA porosity calculation method with a novel autoradiography technique, the Micro-pattern gas detector autoradiography (MPGDA). In this study, the MPGDA is compared with phosphor screen autoradiography (SPA). A set of rock samples from Martinique Island exhibiting a large range of connected porosities was used to validate the MPGDA method. Calculated porosities were found to be in agreement with ones from the SPA and the triple-weight method (TW). The filmless nature of MPGDA as well as straightforward determination of C-14 radioactivity from the source rock makes the porosity calculation less uncertain. The real-time visualization of radioactivity from C-14 beta emissions by MPGDA is a noticeable improvement in comparison to SPA.

Lysophosphatidic Acid Reduces Microregional Oxygen Supply/Consumption Balance after Cerebral Ischemia-Reperfusion

Background: Lysophosphatidic acid (LPA) is a small phospholipid-signaling molecule, which can alter responses to stress in the central nervous system. Objective: We hypothesized that exogenous LPA would increase the size of infarct and reduce microregional O₂ supply/consumption balance after cerebral ischemia-reperfusion. Methods: This was tested in isoflurane-anesthetized rats with middle cerebral artery blockade for 1 h and reperfusion for 2 h with or without LPA (1 mg/kg, at 30, 60, and 90 min after reperfusion). Regional cerebral blood flow was determined using a C¹⁴-iodoantipyrine autoradiographic technique. Regional small-vessel (20–60 µm in diameter) arterial and venous oxygen saturations were determined microspectrophotometrically. Results: There were no significant hemodynamic or arterial blood gas differences between groups. The control ischemic-reperfused cortex had a similar O₂ consumption to the contralateral cortex. However, microregional O₂ supply/consumption balance was significantly reduced in the ischemic-reperfused cortex with many areas of low O₂ saturation (43 of 80 veins with O₂ saturation below 50%). LPA did not significantly alter cerebral blood flow, but it did significantly increase O₂ extraction and consumption of the ischemic-reperfused region. It also significantly increased the number of small veins with low O₂ saturations in the reperfused region (76 of 80 veins with O₂ saturation below 50%). This was associated with a significantly increased cortical infarct size after LPA administration (11.4 ± 0.5% control vs. 16.4 ± 0.6% LPA). Conclusion: This suggests that LPA reduces cell survival and that it is associated with an increase in the number of small microregions with reduced local oxygen balance after cerebral ischemia-reperfusion.

Mobility of daughter elements of 238U decay chain during leaching by In Situ Recovery (ISR): New insights from digital autoradiography

In highly permeable sedimentary rock formations, U extraction by in-situ leaching techniques (ISR − In-Situ Recovery) is generally considered to have a limited environmental impact at ground level. Significantly, this method of extraction produces neither mill tailings nor waste rocks. Underground, however, the outcome for 238U daughter elements in aquifers is not well known because of their trace concentrations in the host rocks. Thus, understanding the in-situ mobility of these elements remains a challenge. Two samples collected before and after six months of ISR experiments (Dulaan Uul, Mongolia) were studied with the help of a digital autoradiography technique (DA) of alpha particles, bulk alpha spectrometry, and complementary petrographic observation methods. These techniques demonstrate that before and after leaching, the radioactivity is concentrated in altered and microporous Fe–Ti oxides. Most of the daughter elements of U remain trapped in the rock after the leaching process. DA confirms that the alpha activity of the Fe–Ti oxides remains high after uranium leaching, and the initial secular equilibrium of the 238U series for 230Th to 210Po daughter elements (including 226Ra) of the fresh rocks is maintained after leaching. While these findings should be confirmed by more systematic studies, they already identify potential mechanisms explaining why the U-daughter concentrations in leaching water are low.

UV-C radiation effect on nuclear tracks of different ions in polycarbonate

The neutron autoradiography technique was developed in our laboratory using polycarbonate nuclear track detectors, to qualitatively and quantitatively analyze boron distribution and concentration in biological samples from experimental models coming from Boron Neutron Capture Therapy research. Spatial resolution was later improved by generating an imprint of the biological sample (e.g. cellular culture, tissue sections) on the detector surface, which can be microscopically observed together with nuclear tracks originated by 10B capture products. This methodology was developed for polycarbonate detectors and involves UV-C light irradiation of the sample-detector assembly. The chemical etching process of the detector, usually performed to enlarge the nuclear tracks, also “reveals” the imprint of the sample.In this work we report a fading effect in nuclear tracks due to UV-C exposure. Significant differences in track density produced by alpha ions and Li recoils coming from the neutron capture reaction, 10B(n,α)7Li, were found between exposed and unexposed to UV-C light (254 nm wavelength) polycarbonate foils. A decreasing relation between track density and exposure time to UV-C radiation could also be observed for these ions. To analyze the effect produced by UV-C radiation on nuclear tracks of different ions, polycarbonate detectors irradiated with 7Li, 12C, 16O, 32S, 127I, 197Au beams and air degraded alpha particles from a241Am source were also studied. A wavelength dependent photodegradation mechanism affecting the polycarbonate detector would be altering the nuclear tracks development in different ways, according to ion damage characteristics.