Browsing by Subject "Topography"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Publication
    Open Access
    Comparative Analysis of Tyrosine Hydroxylase Amacrine Cells in the Mammalian Retina: Distribution and Quantification in Mouse, Rat, Ground Squirrel and Macaque Retinas
    (MDPI, 2025-07-20) Kiyoharu J. Miyagishima; Xiaomin Lai; Amurta Nath; William N. Grimes; Xiyuan Ping; Jeffrey S. Diamond; Morven A. Cameron; Wei Li; Francisco M. Nadal-Nicolás; Francisco M. Nadal-Nicolás; Oftalmología, Optometría, Otorrinolaringología y Anatomía Patológica; Francisco M. Nadal-Nicolás; Facultades de la UMU::Facultad de Medicina
    Dopaminergic amacrine cells (DACs) are a subclass of amacrine cells that modulate retinal processing and light adaptation by releasing dopamine. Although the role of dopamine is largely conserved, their retinal distribution across mammals remains incompletely characterized. In mice, rats, thirteen-lined ground squirrels (TLGSs), and macaques, we systematically compared the localization, number, and topography of DACs by their expression of tyrosine hydroxylase (TH), a crucial enzyme in the biosynthesis of dopamine. In all species examined, TH+ cells were primarily located in the inner nuclear layer; however, there was a species-dependent influence on their number and distribution. Mice exhibited the highest density of TH+cells but completely lacked displaced TH+cells (dTH+cells) in the ganglion cell layer. Despite interspecies variation in the total number of TH+cells in the retina, the overall density in rats, TLGSs, and macaques was similar. Most species displayed a higher density of DACs toward central retinal regions. However, rats exhibited a distinctive dorsal concentration, particularly among dTH+cells. Although most species examined exhibited a similar ratio of TH+cells to Brn3a+ retinal ganglion cells, TLGSs showed a marked reduction, indicating a potentially diminished dopaminergic modulatory role. Species-specific DAC topographies aligned with specialized visual regions, such as the visual streak in TLGS and the macula in macaques. These results reveal both conserved and divergent features of retinal dopamine circuitry, reflecting evolutionary adaptations to visual processing demands.
  • Thumbnail Image
    Publication
    Open Access
    Descripción topográfica en el relato de viajes : el riesgo de reconstruir arbitrariamente los espacios.
    (Universidad de Murcia, Servicio de Publicaciones., 2025) Taranco, David
    En el relato de viajes, la topografía se presenta como una figura retórica que, más allá de la función descriptiva a que está emparejada, aporta verosimilitud. Este elemento resulta de vital importancia para dicho género al no estar amparado por un pacto ficcional entre la autoría y el público lector. Sin embargo, verosimilitud no es sinónimo de veracidad. En este artículo se analizan diversas descripciones en relatos de viajes a fin de exponer la forma en que la topografía puede conducir a una reconstrucción arbitraria de los espacios.
  • Thumbnail Image
    Publication
    Open Access
    Long-term effect of optic nerve axotomy on the retinal ganglion cell layer
    (Association for Research in Vision and Ophthalmology., 2015-09-01) Nadal-Nicolás, Francisco Manuel; Sobrado Calvo, Paloma; Jiménez López, Manuel; Vidal Sanz, Manuel; Agudo Barriuso, Marta; Oftalmología, Optometría, Otorrinolaringología y Anatomía Patológica; Facultades de la UMU::Facultad de Medicina
    Purpose: To analyze the long-term effect of optic nerve injury on retinal ganglion cells (RGCs) and melanopsin+RGCs orthotopic and displaced, and on the rest of the ganglion cell layer (GCL) cells. Methods: In adult albino rats, the left optic nerve was crushed (ONC) or transected (ONT). Injured and contralateral retinas were analyzed at increasing survival intervals (up to 15 months). To study all GCL cells and RGCs, retinas were immunodetected with Brn3a and melanopsin to identify the general RGC population (Brn3a+) and m+RGCs, and counter-stained with 4′,6-diamidino-2-phenylindole (DAPI). Brn3a+RGCs and m+RGCs displaced to the inner nuclear layer were analyzed as well. In additional retinas, glial cells in the GCL were identified with glial fibrillary acidic protein (GFAP) or Iba1, and in some retinas, Brn3a, calretinin, and γ-synuclein were immunodetected. Results: Orthotopic and displaced RGCs behave similarly within the RGC and m+RGC populations. Both lesions cause an exponential loss of RGCs (4%–1% survival at 6 months after ONC or ONT), but not of m+RGCs, whose number remains stable from 1 to 15 months (34%–44% of the initial population). γ-synuclein is expressed by RGCs and displaced amacrine cells (dACs), allowing us to confirm that axotomy does not affect the latter, and to determine that out of the approximately 217,406 cells that compose the GCL (excluding endothelia), 10% are glial cells, 50% dACs, and the remaining 40% are RGCs. Conclusions: In the GCL, only RGCs are lost after axotomy, and there are important differences in the course of loss and rate of survival between melanopsin+RGCs and the rest of RGCs.
  • Thumbnail Image
    Publication
    Open Access
    Postnatal development of the Ammon's horn (CA1 and CA3 fields). A karyometric and topographic study
    (Murcia : F. Hernández, 1994) Pérez Delgado, M.M.; Serrano Aguilar, P.G.; Castañeyra Perdomo, A.; Ferres Torres, R.
    We have performed a karyometric study of the pyramidal neurons of CA1 and CA3 fields of the Ammon's horn, in male mice aged from the 5th to the 190th postnatal day. Nuclear sizes were measured with the aid of a Magiscan Analysis System, used in an interactive form, in both superficial and deep layers of the stratum pyramidal in those fields. The measurements were made at three different topographic levels: rostral; intermediate; and caudal, to detec any possible difference related to the topography of the neuron in the same field. We have found that both CAI and CA3 fields are correlated in the postnatal development of their nuclear pyramidal sizes and that al1 topographic levels of the hippocampus reach their highest karyometric sizes at the 10th-15th postnatal day. Caudal levels show higher karyometric values than the other levels and some differences between neurons of the superficial and deep layers of both fields are also described here and analysed in relation to the different ontogenetic gradients of these cells.
  • Thumbnail Image
    Publication
    Open Access
    Volcar la mesa: revolución ritual y mito en el santuario de Apolo en Delfos
    (Ateneo Cantonal de Estudios Políticos (ACEP), 2019) Hernández Castro, David
    El ciclo de festivales enaetéricos del Septerion, la Herois y la Carila que se celebraba en el santuario de Apolo en Delfos tuvo una enorme importancia para la evolución de la exper iencia religiosa en la Antigua Grecia. Los especialistas modernos los han relacionado con los ritos estacionales y de propiciación de la cosecha, los ritos de expiación y las «ceremonias de corte» ( incision ceremonies ), pero en los últimos años se han prod ucido grandes avances en varios campos (las relaciones entre el ritual y el mito, la arqueología, la arqueoastronomía) que favorecen una interpretación más integral, donde se preste mayor atención a los contextos sociales, políticos, topográficos y narrati vos. En este sentido, el ciclo de festivales del Septerion, la Herois y la Carila se encuentra en el centro del gran movimiento de reforma política y religiosa que se produjo en Delfos a finales del siglo VI a.C. y que tuvo como escenario de fondo e l enfre ntamiento entre los Alcmeónidas y los Pisistrátidas. En el ámbito religioso, el resultado de este movimiento fue la sustitución del Apolo Kerdoos de los tesalios por el Apolo Katharsios de los atenienses, del Apolo de la Ganancia , al Apolo de las Purificac iones. En el ámbito político, el desenlace fue la institución de la democracia y el declive de la tiranía.