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Steven K Fisher - One of the best experts on this subject based on the ideXlab platform.
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noninvasive imaging of the thirteen lined Ground Squirrel photoreceptor mosaic
Visual Neuroscience, 2016Co-Authors: Benjamin S Sajdak, Steven K Fisher, Dana K Merriman, Yusufu N Sulai, Christopher S Langlo, Gabriel Luna, Alfredo DubraAbstract:Ground Squirrels are an increasingly important model for studying visual processing, retinal circuitry, and cone photoreceptor function. Here, we demonstrate that the photoreceptor mosaic can be longitudinally imaged noninvasively in the 13-lined Ground Squirrel (Ictidomys tridecemlineatus) using confocal and nonconfocal split-detection adaptive optics scanning ophthalmoscopy using 790 nm light. Photoreceptor density, spacing, and Voronoi analysis are consistent with that of the human cone mosaic. The high imaging success rate and consistent image quality in this study reinforce the Ground Squirrel as a practical model to aid drug discovery and testing through longitudinal imaging on the cellular scale.
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Experimental retinal detachment in the cone-dominant Ground Squirrel retina: Morphology and basic immunocytochemistry
Visual neuroscience, 2002Co-Authors: Kenneth A. Linberg, Tsutomu Sakai, Geoffrey P. Lewis, Steven K FisherAbstract:The cellular responses of the cone-dominant Ground Squirrel retina to retinal detachment were examined and compared to those in rod-dominant species. Retinal detachments were made in California Ground Squirrels. The retinas were prepared for light, electron, and confocal microscopy. Tissue sections were labeled with antibodies to cone opsins, rod opsin, glial fibrillary acidic protein (GFAP), vimentin, synaptophysin, cytochrome oxidase, and calbindin D 28K. Wax sections were probed with the MIB-1 antibody to detect proliferating cells. By 10 h postdetachment many photoreceptor cells in the Ground Squirrel already show structural signs of apoptosis. At 1 day many photoreceptors have collapsed inner segments (IS), yet others still have short stacks of outer segment discs. At 3 days there is a marked increase in the number of dying photoreceptors. Rod and medium-/long-wavelength opsins are redistributed in the cell membrane to their synaptic terminals. At 7 days photoreceptor cell death has slowed. Some regions of the outer nuclear layer (ONL) have few photoreceptor somata. IS remnants are rare on surviving photoreceptors. At 28 days these trends are even more dramatic. Retinal pigmented epithelium (RPE) cells do not expand into the subretinal space. The outer limiting membrane (OLM) appears flat and uninterrupted. Muller cells remain remarkably unreactive; they show essentially no proliferation, only negligible hypertrophy, and there is no increase in their expression of GFAP or vimentin. Horizontal cells show no dendritic sprouting in response to detachment. The speed and extent of photoreceptor degeneration in response to detachment is greater in Ground Squirrel than in cat retina-only a small number of rods and cones survive at 28 days of detachment. Moreover, the almost total lack of Muller cell and RPE reactivity in the Ground Squirrel retina is a significant difference from results in other species.
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retinal neurons of the california Ground Squirrel spermophilus beecheyi a golgi study
The Journal of Comparative Neurology, 1996Co-Authors: Kenneth A. Linberg, Setsuko Suemune, Steven K FisherAbstract:Although the optic nerve fibers of the cone-dominant Ground Squirrel retina have been well studied physiologically, the morphological details of the retinal neurons have not. To that end, retinal neurons of the California Ground Squirrel have been studied in Golgi-impregnated wholemounts. Two types of horizontal cell have been identified: H1 has an axon and axon terminal, whereas H2 is axonless. The dendritic field of H1 cells enlarges in a nonuniform manner with increasing displacement from the central retina. The smallest examples lie centrally in the visual streak, and the largest occur in the superior periphery. Eight types of bipolar cell are distinguished by morphological differences in dendritic branching pattern and field size in the outer plexiform layer, cell body size, and layering within the inner nuclear layer and by the morphology and stratification of axon terminals in the inner plexiform layer. A large bistratified bipolar cell (B8) is introduced here; the other 7 types closely resemble those in the retinas of other sciurid species described by R.W. West (1976, J. Comp. Neurol. 168:355–378; 1978, Vision Res. 18:129–136). The B1 type is proposed as a blue cone bipolar cell. Amacrine cells are classified into 27 cell types. Six of these occur as mirror-image pairs across the inner plexiform layer, the soma of one of each pair being “displaced” to the ganglion cell layer. The best described of these pairs is the very elaborate starburst amacrine cell, A5, which stains regularly in these wholemounted retinas. Changes in dendritic field size of both A5 subtypes with retinal location are quantified. The morphology of three amacrine cell types identified in Spermophilus beecheyi suggests that their possible counterparts in S. mexicanus (West, 1976) were, as displaced amacrine cells, misidentified as ganglion cells. Amacrine cell types that may play roles in the rod pathway, the blue cone pathway, and ganglion cell directional selectivity are discussed. No type of interplexiform cell was observed. Ganglion cells are classified into 19 cell types, 9 of which probably correspond to the ganglion cells described by West (1976) in the Mexican Ground Squirrel. The bistratified G11 cell is proposed as an ON-OFF directionally selective type. © 1996 Wiley-Liss, Inc.
Dana K Merriman - One of the best experts on this subject based on the ideXlab platform.
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seasonal and post trauma remodeling in cone dominant Ground Squirrel retina
Experimental Eye Research, 2016Co-Authors: Dana K Merriman, Benjamin S Sajdak, Bryan W JonesAbstract:With a photoreceptor mosaic containing ∼85% cones, the Ground Squirrel is one of the richest known mammalian sources of these important retinal cells. It also has a visual ecology much like the human's. While the Ground Squirrel retina is understandably prominent in the cone biochemistry, physiology, and circuitry literature, far less is known about the remodeling potential of its retinal pigment epithelium, neurons, macroglia, or microglia. This review aims to summarize the data from Ground Squirrel retina to this point in time, and to relate them to data from other brain areas where appropriate. We begin with a survey of the Ground Squirrel visual system, making comparisons with traditional rodent models and with human. Because this animal's status as a hibernator often goes unnoticed in the vision literature, we then present a brief primer on hibernation biology. Next we review what is known about Ground Squirrel retinal remodeling concurrent with deep torpor and with rapid recovery upon re-warming. Notable here is rapidly-reversible, temperature-dependent structural plasticity of cone ribbon synapses, as well as pre- and post-synaptic plasticity throughout diverse brain regions. It is not yet clear if retinal cell types other than cones engage in torpor-associated synaptic remodeling. We end with the small but intriguing literature on the Ground Squirrel retina's remodeling responses to insult by retinal detachment. Notable for widespread loss of (cone) photoreceptors, there is surprisingly little remodeling of the RPE or Muller cells. Microglial activation appears minimal, and remodeling of surviving second- and third-order neurons seems absent, but both require further study. In contrast, traumatic brain injury in the Ground Squirrel elicits typical macroglial and microglial responses. Overall, the data to date strongly suggest a heretofore unrecognized, natural checkpoint between retinal deafferentiation and RPE and Muller cell remodeling events. As we continue to discover them, the unique ways by which Ground Squirrel retina responds to hibernation or injury may be adaptable to therapeutic use.
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noninvasive imaging of the thirteen lined Ground Squirrel photoreceptor mosaic
Visual Neuroscience, 2016Co-Authors: Benjamin S Sajdak, Steven K Fisher, Dana K Merriman, Yusufu N Sulai, Christopher S Langlo, Gabriel Luna, Alfredo DubraAbstract:Ground Squirrels are an increasingly important model for studying visual processing, retinal circuitry, and cone photoreceptor function. Here, we demonstrate that the photoreceptor mosaic can be longitudinally imaged noninvasively in the 13-lined Ground Squirrel (Ictidomys tridecemlineatus) using confocal and nonconfocal split-detection adaptive optics scanning ophthalmoscopy using 790 nm light. Photoreceptor density, spacing, and Voronoi analysis are consistent with that of the human cone mosaic. The high imaging success rate and consistent image quality in this study reinforce the Ground Squirrel as a practical model to aid drug discovery and testing through longitudinal imaging on the cellular scale.
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inhibition of borna disease virus replication by an endogenous bornavirus like element in the Ground Squirrel genome
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Kan Fujino, Masayuki Horie, Tomoyuki Honda, Dana K Merriman, Keizo TomonagaAbstract:Animal genomes contain endogenous viral sequences, such as endogenous retroviruses and retrotransposons. Recently, we and others discovered that nonretroviral viruses also have been endogenized in many vertebrate genomes. Bornaviruses belong to the Mononegavirales and have left endogenous fragments, called “endogenous bornavirus-like elements” (EBLs), in the genomes of many mammals. The striking features of EBLs are that they contain relatively long ORFs which have high sequence homology to the extant bornavirus proteins. Furthermore, some EBLs derived from bornavirus nucleoprotein (EBLNs) have been shown to be transcribed as mRNA and probably are translated into proteins. These features lead us to speculate that EBLs may function as cellular coopted genes. An EBLN element in the genome of the thirteen-lined Ground Squirrel (Ictidomys tridecemlineatus), itEBLN, encodes an ORF with 77% amino acid sequence identity to the current bornavirus nucleoprotein. In this study, we cloned itEBLN from the Ground Squirrel genome and investigated its involvement in Borna disease virus (BDV) replication. Interestingly, itEBLN, but not a human EBLN, colocalized with the viral factory in the nucleus and appeared to affect BDV polymerase activity by being incorporated into the viral ribonucleoprotein. Our data show that, as do certain endogenous retroviruses, itEBLN potentially may inhibit infection by related exogenous viruses in vivo.
Richard Policht - One of the best experts on this subject based on the ideXlab platform.
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acoustic analysis of alarm calls of the european Ground Squirrel spermophilus citellus and the taurus Ground Squirrel s taurensis mammalia sciuridae
Zoologischer Anzeiger – A Journal of Comparative Zoology, 2012Co-Authors: Irena Schneiderova, Richard PolichtAbstract:Abstract In comparison to some other species of Ground Squirrels, little is known about alarm calls of the European Ground Squirrel Spermophilus citellus, occurring in some parts of Central Europe and the Balkans, and essentially nothing is known about alarm calls of the Taurus Ground Squirrel S. taurensis, recently described from a small area in Taurus Mountains in southern Anatolia, Turkey. In this study, we performed a detailed analysis, description and comparison of alarm calls in these closely related species. We recorded 20 free-living individuals (10 per species) spontaneously vocalizing toward human in their natural colonies, and analyzed a total of 600 alarm calls (30 per individual). In both species, alarm calls in this context are tonal sounds usually consisting of two different elements. There is almost no frequency modulation in the first element, while the second element is highly modulated in frequency. In spite of the similar basic structure, the calls of each species differed significantly in most of temporal and spectral parameters. Our results support the assumption that vocalizations in sciurids are useful features supporting species identification. The potential factors that might be important in shaping the acoustic structure of alarm calls in S. citellus and S. taurensis remain a fruitful area for future research.
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acoustic analysis of the alarm call of the anatolian Ground Squirrel spermophilus xanthoprymnus a description and comparison with alarm calls of the taurus s taurensis and european s citellus Ground Squirrels
Naturwissenschaften, 2012Co-Authors: Irena Schneiderova, Richard PolichtAbstract:The Anatolian Ground Squirrel Spermophilus xanthoprymnus like other Ground-dwelling sciurids, emits alarm calls in the presence of predators. In this study, we provide a description of the acoustic structure of alarm call of this species and compare it to those of two closely related species, the Taurus Ground Squirrel Spermophilus taurensis and the European Ground Squirrel Spermophilus citellus. The alarm call of S. xanthoprymnus is a tonal sound mostly consisting of two different elements—the first element has low frequency modulation while the second element is highly frequency modulated. A similar basic structure can be found in the alarm calls of some other old world Ground Squirrel species of the genus Spermophilus, including S. taurensis and S. citellus. Despite this similarity, we found that these three species can be clearly distinguished on the basis of their alarm calls. Differences in the acoustic structure of S. xanthoprymnus and S. taurensis calls are especially remarkable, as these two species were considered to be conspecific until 2007. S. xanthoprymnus and S. taurensis were also demonstrated to have closer acoustic similarity, which is in contrast to results based on molecular data indicating that S. taurensis is most closely related to S. citellus.
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alarm calls of the european Ground Squirrel spermophilus citellus and the taurus Ground Squirrel s taurensis encode information about caller identity
Bioacoustics-the International Journal of Animal Sound and Its Recording, 2011Co-Authors: Irena Schneiderova, Richard PolichtAbstract:ABSTRACT Vocalizations of many mammalian species have been reported to encode information about caller identity. In this study, we analyzed 300 alarm calls from 10 free-living European Ground Squirrels Spermophilus citellus (30 per individual) and 300 alarm calls from 10 free-living Taurus Ground Squirrels S. taurensis (30 per individual), and tested the potential of these calls to encode information about the callers' identities. Discriminant analysis including all 10 European Ground Squirrel individuals correctly classified 98% of calls, and cross-validation reached a classification success of 97%. Correct classification of 98% and cross-validation of 98% was assigned when the analysis included only those individuals producing calls consisting of both elements (eight individuals). For the Taurus Ground Squirrel, correct classification was 95% and cross-validation 94% for all 10 animals. When only those individuals producing calls consisting of both elements were included (eight individuals), discriminan...
Benjamin S Sajdak - One of the best experts on this subject based on the ideXlab platform.
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seasonal and post trauma remodeling in cone dominant Ground Squirrel retina
Experimental Eye Research, 2016Co-Authors: Dana K Merriman, Benjamin S Sajdak, Bryan W JonesAbstract:With a photoreceptor mosaic containing ∼85% cones, the Ground Squirrel is one of the richest known mammalian sources of these important retinal cells. It also has a visual ecology much like the human's. While the Ground Squirrel retina is understandably prominent in the cone biochemistry, physiology, and circuitry literature, far less is known about the remodeling potential of its retinal pigment epithelium, neurons, macroglia, or microglia. This review aims to summarize the data from Ground Squirrel retina to this point in time, and to relate them to data from other brain areas where appropriate. We begin with a survey of the Ground Squirrel visual system, making comparisons with traditional rodent models and with human. Because this animal's status as a hibernator often goes unnoticed in the vision literature, we then present a brief primer on hibernation biology. Next we review what is known about Ground Squirrel retinal remodeling concurrent with deep torpor and with rapid recovery upon re-warming. Notable here is rapidly-reversible, temperature-dependent structural plasticity of cone ribbon synapses, as well as pre- and post-synaptic plasticity throughout diverse brain regions. It is not yet clear if retinal cell types other than cones engage in torpor-associated synaptic remodeling. We end with the small but intriguing literature on the Ground Squirrel retina's remodeling responses to insult by retinal detachment. Notable for widespread loss of (cone) photoreceptors, there is surprisingly little remodeling of the RPE or Muller cells. Microglial activation appears minimal, and remodeling of surviving second- and third-order neurons seems absent, but both require further study. In contrast, traumatic brain injury in the Ground Squirrel elicits typical macroglial and microglial responses. Overall, the data to date strongly suggest a heretofore unrecognized, natural checkpoint between retinal deafferentiation and RPE and Muller cell remodeling events. As we continue to discover them, the unique ways by which Ground Squirrel retina responds to hibernation or injury may be adaptable to therapeutic use.
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noninvasive imaging of the thirteen lined Ground Squirrel photoreceptor mosaic
Visual Neuroscience, 2016Co-Authors: Benjamin S Sajdak, Steven K Fisher, Dana K Merriman, Yusufu N Sulai, Christopher S Langlo, Gabriel Luna, Alfredo DubraAbstract:Ground Squirrels are an increasingly important model for studying visual processing, retinal circuitry, and cone photoreceptor function. Here, we demonstrate that the photoreceptor mosaic can be longitudinally imaged noninvasively in the 13-lined Ground Squirrel (Ictidomys tridecemlineatus) using confocal and nonconfocal split-detection adaptive optics scanning ophthalmoscopy using 790 nm light. Photoreceptor density, spacing, and Voronoi analysis are consistent with that of the human cone mosaic. The high imaging success rate and consistent image quality in this study reinforce the Ground Squirrel as a practical model to aid drug discovery and testing through longitudinal imaging on the cellular scale.
Alfredo Dubra - One of the best experts on this subject based on the ideXlab platform.
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noninvasive imaging of the thirteen lined Ground Squirrel photoreceptor mosaic
Visual Neuroscience, 2016Co-Authors: Benjamin S Sajdak, Steven K Fisher, Dana K Merriman, Yusufu N Sulai, Christopher S Langlo, Gabriel Luna, Alfredo DubraAbstract:Ground Squirrels are an increasingly important model for studying visual processing, retinal circuitry, and cone photoreceptor function. Here, we demonstrate that the photoreceptor mosaic can be longitudinally imaged noninvasively in the 13-lined Ground Squirrel (Ictidomys tridecemlineatus) using confocal and nonconfocal split-detection adaptive optics scanning ophthalmoscopy using 790 nm light. Photoreceptor density, spacing, and Voronoi analysis are consistent with that of the human cone mosaic. The high imaging success rate and consistent image quality in this study reinforce the Ground Squirrel as a practical model to aid drug discovery and testing through longitudinal imaging on the cellular scale.
