Retinal ganglion cell (RGC) loss underlies several conditions which give rise to significant visual compromise, including glaucoma and ischaemic optic neuropathies. Neuroprotection of RGCs is a clinical well-defined unmet need in these diseases, and adenosine A3 receptor (A3R) activation emerges as a therapeutic pharmacological approach to protect RGCs. A porous biodegradable intraocular implant loaded with 2-Cl-IB-MECA (selective A3R agonist) was used as a strategy to protect RGCs. Drug-loaded PCL implants released 2-Cl-IB-MECA for an extended period and the released 2-Cl-IB-MECA limited glutamate-evoked calcium (Ca2+) rise in RGCs. Retinal thinning due to transient ischemia was not prevented by 2-Cl-IB-MECA-PCL implant. However, 2-Cl-IB-MECA-PCL implants decreased retinal cell death, promoted the survival of RGCs, preserved optic nerve structure and anterograde axonal transport. We further demonstrated that 2-Cl-IB-MECA-loaded PCL implants were able to enhance RGC function that was compromised by transient ischemia. Taking into consideration the beneficial effects afforded by 2-Cl-IB-MECA released from the PCL implant, this can be envisaged a good therapeutic strategy to protect RGCs.
Abstract Alzheimer’s disease (AD) is a progressive neurodegenerative disorder whose diagnosis remains a notable challenge. The literature suggests that cerebral changes precede AD symptoms by over two decades, implying a significantly advanced stage of AD by the time it is usually diagnosed. In the study herein, texture analysis was applied to computed optical coherence tomography ocular fundus images to identify differences between a group of the transgenic mouse model of the Alzheimer’s disease (3×Tg-AD) and a group of wild-type mice, at the ages of one and two-months-old. A substantial difference between groups was found at both time-points across all neuroretina’s layers. Here, the inner nuclear layer stands out both in the level of statistically significant differences and on the extension of these differences which span through the imaged area. Also, the progression of AD is suggested to be spotted by texture analysis as demonstrated by the significant difference found in the inner plexiform and the outer nuclear layers from the age of one to the age of two-months-old. These findings demonstrate the potential of the use of the retina and texture analysis to the diagnosis of AD and monitor AD progression. Besides, the differences between groups found in this study suggest that the 3×Tg-AD model may be inappropriate to study early changes associated with the AD and other animal models should be tested following the same path and rationale. Moreover, these results also suggest that the human genes present in these transgenic mice may have an impact on the neurodevelopment of offspring which would justify the significant changes found at the age of one-month-old.
Transmission line-based metamaterials are used to realize and model the conjugate-impedance matched superabsorbers. Here, we formulate an analytical-numerical approach for maximizing the effective absorption cross section of the metamaterial wormhole superabsorber, under the goal of minimizing the complexity of the structure. Analytical expressions for the gradient of the absorption cross section as a function of the structural parameters are derived. Numerical results showing enhanced absorption are obtained under three different optimization strategies: a ring-by-ring approach, a gradient-based optimization, and a mixed algorithm. The best results are achieved with the mixed algorithm, with which it is demonstrated that the optimal wormhole superabsorber significantly outperforms a black body-type absorber of a similar size. This study is of a particular interest for applications of the conjugate-impedance-matched superabsorbers as efficient harvesters of electromagnetic radiation.
Poster: ECR 2017 / C-3117 / Development of a software plug-in for non-gaussian diffusion MRI data: application to breast by: A. C. C. Amorim 1, R. G. Nunes1, F. Borlinhas1, L. Nogueira2, S. Brandao2, H. A. Ferreira1; 1Lisbon/PT, 2Porto/PT
Texture analysis describes a variety of image analysis techniques that quantify the variation in intensity and pattern. This paper provides an overview of several texture analysis approaches addressing the rationale supporting them, their advantages, drawbacks, and applications. This survey's emphasis is in collecting and categorising over five decades of active research on texture analysis. Brief descriptions of different approaches are presented along with application examples. From a broad range of texture analysis applications, this survey's final focus is on biomedical image analysis. An up-to-date list of biological tissues and organs in which disorders produce texture changes that may be used to spot disease onset and progression is provided. Finally, the role of texture analysis methods as biomarkers of disease is summarised.
Conjugate impedance matched metamaterials are shown to be effective traps for electromagnetic waves. Objects made of such materials are able to receive radiation even when it is not directly incident on their surface. Here, we develop methods of physical modeling of such objects and investigate interactions of conjugate impedance matched superabsorbers with passing electromagnetic radiation. We study realizations of such metamaterials with meshes of loaded transmission lines and develop a theory of electromagnetic wave propagation and absorption in such media. Peculiar wave propagation, wave trapping and absorption effects in metamaterial black holes and wormholes are demonstrated. Possible modifications under the goal of optimizing absorption while minimizing complexity of the involved metamaterials are discussed. Conjugate-impedance matched superabsorbers may find applications as efficient harvesters of electromagnetic radiation, and as novel antennas and sensors.
Abstract Purpose In this work, we aimed to assess the difference in thickness of the retina of the triple‐transgenic mice model of Alzheimer’s disease (3xTg‐AD), compared to controls (wild‐type ‐ WT), at the age of one month. Methods Mice’s retinas were imaged by optical coherence tomography (OCT) using the Phoenix Micron IV OCT (Phoenix Research Labs, USA) to produce 512 B‐scans of 512 A‐scans each. All right eyes of 45 3xTg‐AD and 46 WT mice were imaged in vivo, and all scans were performed horizontally centred in the optic disc and vertically above it. All mice were weighted at the scan time. A software was developed to determine the inner limiting membrane and the photoreceptor‐retinal pigment epithelium interface, automatically, to produce a detailed thickness map of 512 × 512 values, later split into 3x3 regions. The average thickness of each region and the average of the entire imaged area were computed. All processing, software development and statistical analyses were performed using Matlab R2019a (The Mathworks Inc, USA). Results The Kolmogorov‐Smirnov normality test was applied to all measures. Since the majority failed the normality assumption, the Mann‐Whitney test was used to determine differences between groups. No statistically significant differences were found between groups for the weight (p‐value=0.9536; m(sd): 14.84(2.71) grams for 3xTg‐AD and 14.88(2.58) grams for WT). A strong statistically significant difference (p‐value < 0.001) was found between the thickness of the retina of the two groups for all nine regions and the average retinal thickness, with the 3xTg‐AD mice presenting a thinner retina ‐ average values for the entire imaged area of 290.26(7.15) (m(sd)) microns compared to the WT (302.20(4.08)). Conclusions The 3xTg‐AD mice present a statistically thinner retina regarding the control group, at the age of one month, even though no statistically significant differences were found between groups for the weight.
Abstract The early diagnosis of neurodegenerative disorders is still an open issue despite the many efforts to address this problem. In particular, Alzheimer’s disease (AD) remains undiagnosed for over a decade before the first symptoms. Optical coherence tomography (OCT) is now common and widely available and has been used to image the retina of AD patients and healthy controls to search for biomarkers of neurodegeneration. However, early diagnosis tools would need to rely on images of patients in early AD stages, which are not available due to late diagnosis. To shed light on how to overcome this obstacle, we resort to 57 wild-type mice and 57 triple-transgenic mouse model of AD to train a network with mice aged 3, 4, and 8 months and classify mice at the ages of 1, 2, and 12 months. To this end, we computed fundus images from OCT data and trained a convolution neural network (CNN) to classify those into the wild-type or transgenic group. CNN performance accuracy ranged from 80 to 88% for mice out of the training group’s age, raising the possibility of diagnosing AD before the first symptoms through the non-invasive imaging of the retina.
Mice are widely used as models for many diseases, including eye and neurodegenerative diseases.However, there is a lack of normative data for retinal thickness over time, especially at young ages.In this work, we present a normative thickness database from one to four-months-old, for nine layers/layer-aggregates, including the total retinal thickness, obtained from the segmentation of spectral-domain optical coherence tomography (SD-OCT) data from the C57BL6/129S mouse strain.Based on fifty-seven mice, this normative database provides an opportunity to study the ageing of control mice and characterize disease models' ageing, such as the triple transgenic mouse model of Alzheimer's disease (3×Tg-AD) used in this work.We report thickness measurements, the differences in thickness per layer, demonstrate a nasal-temporal asymmetry, and the variation of thickness as a function to the distance to the optic disc center.Significant differences were found between the transgenic group's thickness and the normative database for the entire period covered in this study.Even though it is well accepted that retinal nerve fiber layer (RNFL) thinning is a hallmark of neurodegeneration, our results show a thicker RNFL-GCL (RNFL-Ganglion cell layer) aggregate for the 3×Tg-AD mice until four-months-old.
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