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Retinal signal processing

Joanna Borowska-Fielding, Natalia Murataeva, Ben Smith, Anna-Maria Szczesniak, Emma Leishmann, Laura Daily, Tom Toguri, Cecelia Hillard, Julian Romero, Heather Bradshaw, Melanie Kelly, Alex Straiker
The cannabinoid receptor CB2 plays a significant role in the regulation of immune function whereas neuronal expression remains a subject of contention. Multiple studies have described CB2 in retina and a recent study showed that CB2 deletion altered retinal visual processing. We revisited CB2 expression using immunohistochemistry and a recently developed CB2-eGFP reporter mouse. We examined the consequence of acute vs. prolonged CB2 deactivation on the electroretinogram (ERG) responses. We also examined lipidomics in CB2 knockout mice and potential changes in microglia using Scholl analysis...
August 16, 2018: Neuropharmacology
Vanessa Gama Goulart, Grasielle Duarte Menezes, Sheila Espírito-Santo, Adriana da Cunha Faria-Melibeu, Claudio Alberto Serfaty, Paula Campello-Costa
OBJECTIVE: Interleukin 4 (IL-4) is an anti-inflammatory cytokine related to different aspects of central nervous system development such as survival, proliferation, and differentiation, among others. Our goals were to investigate the effect of intravitreous treatment with IL-4 on the activation of downstream signaling pathways in the retina and the distribution of retinal axons within the superior colliculus (SC). MATERIAL AND METHODS: Lister hooded rats were submitted to an intravitreous injection of either IL-4 (5 U/µL) or PBS (vehicle) at postnatal day 10 (PND10)...
August 15, 2018: Neuroimmunomodulation
Lyndsay A Wylie, Kevin P Mouillesseaux, Diana C Chong, Victoria L Bautch
The BMP pathway regulates developmental processes including angiogenesis, yet its signaling outputs are complex and context-dependent. Recently, we showed that SMAD6, an intracellular BMP inhibitor expressed in endothelial cells, decreases vessel sprouting and branching both in vitro and in zebrafish. Genetic deletion of SMAD6 in mice results in poorly characterized cardiovascular defects and lethality. Here, we analyzed the effects of SMAD6 loss on vascular function during murine development. SMAD6 was expressed in a subset of blood vessels throughout development, primarily in arteries, while expression outside of the vasculature was largely confined to developing cardiac valves with no obvious embryonic phenotype...
August 9, 2018: Developmental Biology
Diana S Brightman, Rachel L Grant, Philip A Ruzycki, Ray Suzuki, Anne K Hennig, Shiming Chen
Development of retinal structure and function is controlled by cell type-specific transcription factors and widely expressed co-regulators. The latter includes the mixed-lineage leukemia (MLL) family of histone methyltransferases that catalyze histone H3 lysine 4 di- and tri-methylation associated with gene activation. One such member, MLL1, is widely expressed in the central nervous system including the retina. However, its role in retinal development is unknown. To address this question, we knocked out Mll1 in mouse retinal progenitors, and discovered that MLL1 plays multiple roles in retinal development by regulating progenitor cell proliferation, cell type composition and neuron-glia balance, maintenance of horizontal neurons, and formation of functional synapses between neuronal layers required for visual signal transmission and processing...
August 9, 2018: Scientific Reports
Christina Mayer, Claus Bruehl, Emma L Salt, Ricarda Diem, Andreas Draguhn, Richard Fairless
Retinal ganglion cells (RGCs), a diverse body of neurons which relay visual signals from the retina to the higher processing regions of the brain, are susceptible to neurodegenerative processes in several diseases affecting the retina. Previous evidence shows that RGCs are damaged at early stages of autoimmune optic neuritis (AON), prior to subsequent degeneration of the optic nerve. In order to study cell type-specific vulnerability of RGCs we performed immunohistochemical and patch-clamp electrophysiological analyses of RGCs following induction of AON using the experimental autoimmune encephalomyelitis model in Brown Norway rats...
August 1, 2018: Neuroscience
Edward A Hayter, Timothy M Brown
BACKGROUND: Intrinsically photosensitive retinal ganglion cells (ipRGCs) drive an array of non-image-forming (NIF) visual responses including circadian photoentrainment and the pupil light reflex. ipRGCs integrate extrinsic (rod/cone) and intrinsic (melanopsin) photoreceptive signals, but the contribution of cones to ipRGC-dependent responses remains incompletely understood. Given recent data revealing that cone-derived colour signals influence mouse circadian timing and pupil responses in humans, here we set out to investigate the role of colour information in pupil control in mice...
July 31, 2018: BMC Biology
Ana R Santiago, Raquel Boia, Inês D Aires, António F Ambrósio, Rosa Fernandes
Oxidative stress plays key roles in the pathogenesis of retinal diseases, such as diabetic retinopathy. Reactive oxygen species (ROS) are increased in the retina in diabetes and the antioxidant defense system is also compromised. Increased ROS stimulate the release of pro-inflammatory cytokines, promoting a chronic low-grade inflammation involving various signaling pathways. An excessive production of ROS can lead to retinal endothelial cell injury, increased microvascular permeability, and recruitment of inflammatory cells at the site of inflammation...
2018: Frontiers in Physiology
Genevieve Syn, Denise Anderson, Jenefer M Blackwell, Sarra E Jamieson
Recent interest has focussed on the influence of infectious disease organisms on the host epigenome. Toxoplasma gondii infection acquired congenitally or in early life is associated with severe ocular and brain developmental anomalies, while persistent asymptomatic infection is a proposed risk factor for neurodegenerative and psychiatric disorders, including Parkinson's and Alzheimer's Diseases, and schizophrenia. Genome-wide analysis of the host methylome and transcriptome following T. gondii infection in a retinal cell line identified genes (132, 186 and 128 genes at 2, 6 and 24 h post-infection) concordant for methylation and expression, i...
July 26, 2018: Infection, Genetics and Evolution
T Rajalakshmi, Shanthi Prince
The physiological modeling of retinal layers to provide an insight into how the incoming image is converted into its equivalent spike train that can be decoded by the human brain is a key issue. Most of the retinal layer models concentrate mainly on image compression, edge detection and image reconstruction. A retinal layer model to generate spike waveform corresponding to the visual information is not covered much in the literature. The aim of this study was to develop a mathematical model of retinal layers that has complex neural structures, that can detect the incoming signal and transform the signal into the equivalent spike train...
July 28, 2018: Biomedizinische Technik. Biomedical Engineering
Cédric Rochepeau, Laurent Kodjikian, Max-Adrien Garcia, Charlotte Coulon, Carole Burillon, Philippe Denis, Benoît Delaunay, Thibaud Mathis
PURPOSE: To investigate choriocapillaris (CC) blood flow in unaffected fellow eyes of patients with central serous chorioretinopathy (CSC) using quantitative optical coherence tomography angiography (OCTA) analysis. DESIGN: Case-control study. METHODS: Patients with acute, recurrent or persistent CSC, along with healthy gender- and age-matched subjects were included. Objective assessment of CC blood flow was performed using OCTA measurements...
July 24, 2018: American Journal of Ophthalmology
Francesco Segatta, Itay Gdor, Julien Réhault, Simone Taioli, Noga Friedman, Mordechai Sheves, Ivan Rivalta, Sanford Ruhman, Giulio Cerullo, Marco Garavelli
By comparing two-dimensional electronic spectroscopy (2DES) and Pump-Probe (PP) measurements on xanthorhodopsin (XR) and reduced-xanthorhodopsin (RXR) complexes, the ultrafast carotenoid-to-retinal energy transfer pathway is revealed, at very early times, by an excess of signal amplitude at the associated cross-peak and by the carotenoid bleaching reduction due to its ground state recovery. The combination of the measured 2DES and PP spectroscopic data with theoretical modelling allows a clear identification of the main experimental signals and a comprehensive interpretation of their origin and dynamics...
July 26, 2018: Chemistry: a European Journal
Michele Rucci, Jonathan D Victor
During development, the eye tunes its size to its optics so that distant objects are in focus, a state known as emmetropia. Although multiple factors contribute to this process, a strong influence appears to be exerted by the visual input signals entering the eye. Much research has been dedicated to the possible roles of specific features of the retinal image, such as the magnitude of blur. However, in humans and other species, the input to the retina is not an image, but a spatiotemporal flow of luminance...
July 2, 2018: Journal of Vision
Melina A Agosto, Ivan A Anastassov, Michael A Robichaux, Theodore G Wensel
The chemical signal of light onset, a decrease in glutamate release from rod and cone photoreceptors, is processed by a postsynaptic G protein signaling cascade in ON-bipolar cells (BPCs). The metabotropic glutamate receptor mGluR6, along with other cascade elements, is localized synaptically at the BPC dendritic tips. The effector ion channel protein transient receptor potential melastatin-1 (TRPM1), in contrast, is located not only at the dendritic tips but also in BPC bodies and axons. Little is known about the intracellular localization of TRPM1, or its trafficking route to the dendritic tip plasma membrane...
May 2018: ENeuro
Ana I Arroba, Antonio Campos-Caro, Manuel Aguilar-Diosdado, Ángela M Valverde
Retinal degenerative diseases are a group of heterogeneous diseases that include age-related macular degeneration (AMD), retinitis pigmentosa (RP), and diabetic retinopathy (DR). The progressive degeneration of the retinal neurons results in a severe deterioration of the visual function. Neuroinflammation is an early hallmark of many neurodegenerative disorders of the retina including AMD, RP and DR. Microglial cells, key components of the retinal immune defense system, are activated in retinal degenerative diseases...
2018: Frontiers in Aging Neuroscience
Florencia Garrido-Charad, Tomas Vega-Zuniga, Cristián Gutiérrez-Ibáñez, Pedro Fernandez, Luciana López-Jury, Cristian González-Cabrera, Harvey J Karten, Harald Luksch, Gonzalo J Marín
The optic tectum (TeO), or superior colliculus, is a multisensory midbrain center that organizes spatially orienting responses to relevant stimuli. To define the stimulus with the highest priority at each moment, a network of reciprocal connections between the TeO and the isthmi promotes competition between concurrent tectal inputs. In the avian midbrain, the neurons mediating enhancement and suppression of tectal inputs are located in separate isthmic nuclei, facilitating the analysis of the neural processes that mediate competition...
August 7, 2018: Proceedings of the National Academy of Sciences of the United States of America
Junwon Lee, Sang-Hwi Choi, Young-Beom Kim, Ikhyun Jun, Jin Jea Sung, Dongjin R Lee, Yang In Kim, Myung Soo Cho, Suk Ho Byeon, Dae-Sung Kim, Dong-Wook Kim
Purpose: We aimed to establish an efficient method for retinal ganglion cell (RGC) differentiation from human pluripotent stem cells (hPSCs) using defined factors. Methods: To define the contribution of specific signal pathways to RGC development and optimize the differentiation of hPSCs toward RGCs, we examined RGC differentiation in three stages: (1) eye field progenitors expressing the eye field transcription factors (EFTFs), (2) RGC progenitors expressing MATH5, and (3) RGCs expressing BRN3B and ISLET1...
July 2, 2018: Investigative Ophthalmology & Visual Science
Takuma Sonoda, Seul Ki Lee, Lutz Birnbaumer, Tiffany M Schmidt
Melanopsin is expressed in distinct types of intrinsically photosensitive retinal ganglion cells (ipRGCs), which drive behaviors from circadian photoentrainment to contrast detection. A major unanswered question is how the same photopigment, melanopsin, influences such vastly different functions. Here we show that melanopsin's role in contrast detection begins in the retina, via direct effects on M4 ipRGC (ON alpha RGC) signaling. This influence persists across an unexpectedly wide range of environmental light levels ranging from starlight to sunlight, which considerably expands the functional reach of melanopsin on visual processing...
July 6, 2018: Neuron
Jun Cheng
Sparse learning has been shown to be effective in solving many real-world problems. Finding sparse representations is a fundamentally important topic in many fields of science including signal processing, computer vision, genome study and medical imaging. One important issue in applying sparse representation is to find the basis to represent the data, especially in computer vision and medical imaging where the data is not necessary incoherent. In medical imaging, clinicians often grade the severity or measure the risk score of a disease based on images...
June 29, 2018: IEEE Transactions on Medical Imaging
Giovanni Pietro Seu, Gian Nicola Angotzi, Fabio Boi, Luigi Raffo, Luca Berdondini, Paolo Meloni
Microelectrode array (MEA) systems with up to several thousands of recording electrodes and electrical or optical stimulation capabilities are commercially available or described in the literature. By exploiting their submillisecond and micrometric temporal and spatial resolutions to record bioelectrical signals, such emerging MEA systems are increasingly used in neuroscience to study the complex dynamics of neuronal networks and brain circuits. However, they typically lack the capability of implementing real-time feedback between the detection of neuronal spiking events and stimulation, thus restricting large-scale neural interfacing to open-loop conditions...
May 30, 2018: IEEE Transactions on Biomedical Circuits and Systems
Tiina Öhman, Fitsum Tamene, Helka Göös, Sirpa Loukovaara, Markku Varjosalo
Aging is a phenomenon that is associated with profound medical implications. Idiopathic epiretinal membrane (iEMR) and macular hole (MH) are the major vision-threatening vitreoretinal diseases affecting millions of aging people globally, making these conditions an important public health issue. iERM is characterized by fibrous tissue developing on the surface of the macula, which leads to biomechanical and biochemical macular damage. MH is a small breakage in the macula and is associated with many ocular conditions...
July 2, 2018: Aging Cell
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