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  1. Article ; Online: Measuring Retinal Vessel Diameter from Mouse Fluorescent Angiography Images.

    García-Llorca, Andrea / Reynisson, Hallur / Eysteinsson, Thor

    Journal of visualized experiments : JoVE

    2023  , Issue 195

    Abstract: It is important to study the development of retinal vasculature in retinopathies in which abnormal vessel growth can ultimately lead to vision loss. Mutations in the microphthalmia-associated transcription factor (Mitf) gene show hypopigmentation, ... ...

    Abstract It is important to study the development of retinal vasculature in retinopathies in which abnormal vessel growth can ultimately lead to vision loss. Mutations in the microphthalmia-associated transcription factor (Mitf) gene show hypopigmentation, microphthalmia, retinal degeneration, and in some cases, blindness. In vivo imaging of the mouse retina by noninvasive means is vital for eye research. However, given its small size, mouse fundus imaging is difficult and might require specialized tools, maintenance, and training. In this study, we have developed a unique software enabling analysis of the retinal vessel diameter in mice with an automated program written in MATLAB. Fundus photographs were obtained with a commercial fundus camera system following an intraperitoneal injection of a fluorescein salt solution. Images were altered to enhance contrast, and the MATLAB program permitted extracting the mean vascular diameter automatically at a predefined distance from the optic disk. The vascular changes were examined in wild-type mice and mice with various mutations in the Mitf gene by analyzing the retinal vessel diameter. The custom-written MATLAB program developed here is practical, easy to use, and allows researchers to analyze the mean diameter and mean total diameter, as well as the number of vessels from the mouse retinal vasculature, conveniently and reliably.
    MeSH term(s) Mice ; Animals ; Retinal Vessels/diagnostic imaging ; Fluorescein Angiography/methods ; Fundus Oculi ; Optic Disk ; Retinal Diseases
    Language English
    Publishing date 2023-05-19
    Publishing country United States
    Document type Journal Article ; Video-Audio Media
    ZDB-ID 2259946-0
    ISSN 1940-087X ; 1940-087X
    ISSN (online) 1940-087X
    ISSN 1940-087X
    DOI 10.3791/64964
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Mouse microphthalmia-associated transcription factor (Mitf) mutations affect the structure of the retinal vasculature.

    Daníelsson, Stefán Broddi / García-Llorca, Andrea / Reynisson, Hallur / Eysteinsson, Thor

    Acta ophthalmologica

    2022  Volume 100, Issue 8, Page(s) 911–918

    Abstract: Purpose: Mice carrying pathogenic variants in the microphthalmia transcription factor (Mitf) gene show structural and functional changes in the retina and retinal pigment epithelium. The purpose of this study was to assess the vascular changes in Mitf ... ...

    Abstract Purpose: Mice carrying pathogenic variants in the microphthalmia transcription factor (Mitf) gene show structural and functional changes in the retina and retinal pigment epithelium. The purpose of this study was to assess the vascular changes in Mitf mice carrying pathogenic variants by determining their retinal vessel diameter.
    Methods: Mice examined in this study were: B6-Mitf
    Results: The mean diameter of retinal veins in Mitf
    Conclusion: An increase in vascularization of the retina in Mitf
    MeSH term(s) Animals ; Mice ; Mice, Inbred C57BL ; Microphthalmia-Associated Transcription Factor/genetics ; Microphthalmos/genetics ; Mutation ; Retinal Vessels/pathology
    Chemical Substances Microphthalmia-Associated Transcription Factor ; Mitf protein, mouse
    Language English
    Publishing date 2022-03-29
    Publishing country England
    Document type Journal Article
    ZDB-ID 2408333-1
    ISSN 1755-3768 ; 1755-375X
    ISSN (online) 1755-3768
    ISSN 1755-375X
    DOI 10.1111/aos.15140
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Development of a rabbit model of Adenosine triphosphate-induced monocular retinal degeneration for optimization of retinal prostheses.

    Reynisson, Hallur / Nivison-Smith, Lisa / Lovell, Nigel H / Kalloniatis, Michael / Shivdasani, Mohit N

    Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference

    2023  Volume 2023, Page(s) 1–4

    Abstract: Optimization of retinal prostheses requires preclinical animal models that mimic features of human retinal disease, have appropriate eye sizes to accommodate implantable arrays, and provide options for unilateral degeneration so as to enable a ... ...

    Abstract Optimization of retinal prostheses requires preclinical animal models that mimic features of human retinal disease, have appropriate eye sizes to accommodate implantable arrays, and provide options for unilateral degeneration so as to enable a contralateral, within-animal control eye. In absence of a suitable non-human primate model and shortcomings of our previous feline model generated through intravitreal injections of Adenosine Triphosphate (ATP), we aimed in the present study to develop an ATP induced degeneration model in the rabbit. Six normally sighted Dutch rabbits were monocularly blinded with this technique. Subsequent retinal degeneration was assessed with optical coherence tomography, electroretinography, and histological assays. Overall, there was a 42% and 26% reduction in a-wave and oscillatory potential amplitudes in the electroretinograms respectively, along with a global decrease in retinal thickness, with increased variability. Qualitative inspection also revealed that there were variable levels of retinal degeneration and remodeling both within and between treated eyes, mimicking the disease heterogeneity observed in retinitis pigmentosa. These findings confirm that ATP can be utilized to unilaterally induce blinding in rabbits and, potentially present an ideal model for future cortical recording experiments aimed at optimizing vision restoration strategies.Clinical Relevance- A rapid, unilaterally induced model of retinal degeneration in an animal with low binocular overlap and large eyes will allow for clinically valid recordings of downstream cortical activity following retinal stimulation. Such a model would be highly beneficial for the optimization of clinically appropriate vision restoration approaches.
    MeSH term(s) Rabbits ; Animals ; Cats ; Retinal Degeneration/etiology ; Visual Prosthesis ; Adenosine Triphosphate/adverse effects ; Retina/pathology ; Retinitis Pigmentosa
    Chemical Substances Adenosine Triphosphate (8L70Q75FXE)
    Language English
    Publishing date 2023-12-11
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 2694-0604
    ISSN (online) 2694-0604
    DOI 10.1109/EMBC40787.2023.10340920
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article: Loss of Müller cell glutamine synthetase immunoreactivity is associated with neuronal changes in late-stage retinal degeneration.

    Reynisson, Hallur / Kalloniatis, Michael / Fletcher, Erica L / Shivdasani, Mohit N / Nivison-Smith, Lisa

    Frontiers in neuroanatomy

    2023  Volume 17, Page(s) 997722

    Abstract: Introduction: A hallmark of photoreceptor degenerations is progressive, aberrant remodeling of the surviving retinal neurons and glia following photoreceptor loss. The exact relationship between neurons and glia remodeling in this late stage of retinal ... ...

    Abstract Introduction: A hallmark of photoreceptor degenerations is progressive, aberrant remodeling of the surviving retinal neurons and glia following photoreceptor loss. The exact relationship between neurons and glia remodeling in this late stage of retinal degeneration, however, is unclear. This study assessed this by examining Müller cell dysfunction via glutamine synthetase immunoreactivity and its spatial association with retinal neuron subpopulations through various cell markers.
    Methods: Aged Rd1 mice retinae (P150 - P536,
    Results: Glutamine synthetase immunoreactivity was lost as a function of age in the rd1 mouse retina (P150 - P536). Immunoreactivity of other Müller cell markers, however, were unaffected suggesting Müller cells were still present in these low glutamine synthetase immunoreactive regions. Glutamine synthetase immunoreactivity loss affected specific neuronal populations: Type 2, Type 8 cone, and rod bipolar cells, as well as AII amacrine cells based on reduced recoverin, protein kinase Ca and parvalbumin immunoreactivity, respectively. The number of cell nuclei within regions of low glutamine synthetase immunoreactivity was also reduced suggesting possible neuronal loss rather than reduced cell marker immunoreactivity.
    Conclusion: These findings further support a strong interplay between glia-neuronal alterations in late-stage degeneration and highlight a need for future studies and consideration in intervention development.
    Language English
    Publishing date 2023-03-07
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2452969-2
    ISSN 1662-5129
    ISSN 1662-5129
    DOI 10.3389/fnana.2023.997722
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Mitf Links Neuronal Activity and Long-Term Homeostatic Intrinsic Plasticity.

    Atacho, Diahann A M / Reynisson, Hallur / Petursdottir, Anna Thora / Eysteinsson, Thor / Steingrimsson, Eirikur / Petersen, Petur Henry

    eNeuro

    2020  Volume 7, Issue 2

    Abstract: Neuroplasticity forms the basis for neuronal circuit complexity and differences between otherwise similar circuits. We show that the microphthalmia-associated transcription factor ( ...

    Abstract Neuroplasticity forms the basis for neuronal circuit complexity and differences between otherwise similar circuits. We show that the microphthalmia-associated transcription factor (
    MeSH term(s) Animals ; Mice ; Microphthalmia-Associated Transcription Factor/genetics ; Neurons ; Odorants ; Olfactory Bulb ; Smell
    Chemical Substances Microphthalmia-Associated Transcription Factor ; Mitf protein, mouse
    Language English
    Publishing date 2020-04-21
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2800598-3
    ISSN 2373-2822 ; 2373-2822
    ISSN (online) 2373-2822
    ISSN 2373-2822
    DOI 10.1523/ENEURO.0412-19.2020
    Database MEDical Literature Analysis and Retrieval System OnLINE

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