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  • 1
    Electronic Resource
    Electronic Resource
    In utero development and maturation of the retina of a non-primate mammal: A light and electron microscopic study of the guinea pig (1975)
    Springer
    Anatomy and embryology 146 (1975), S. 279-300 
    Details
    ISSN: 1432-0568
    Keywords: Retinogenesis ; Synaptogenesis ; Guinea pig ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A light and electron microscopic examination of retinogenesis in the fetal guinea pig has revealed an early development of synapses and photoreceptor cells. Differentiation of the neural retina begins around day 23 of gestation. By 34 days the retina reaches its maximum thickness. It differentiates an inner plexiform layer in which vesicle-containing processes and primitive synapses are evident. Synaptic ribbons are found in processes of this layer by 43–45 days of gestation. An outer plexiform layer develops within the neuroblast layer at 40 days of gestation; from its first appearance the outer plexiform layer contains synapses complete with synaptic ribbons. Receptor terminals of the α, paranuclear and β type are present well before birth. Photoreceptor cells form inner segments by 40 days; the formation of outer segments is indicated by 45 days but not widespread until 49 days. The retina appears mature by day 51–57. It is clear that the primate is not unique in the early differentiation of its retinal synapses relative to the time of maturation of its photoreceptor cells. The potential functional capacities of precocious retinae, and the mechanisms of synapse development are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00302175
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  • 2
    Electronic Resource
    Electronic Resource
    Histological and electron microscopic milestones in the development of the retina of a marsupial wallaby, Macropus eugenii (1989)
    Springer
    Anatomy and embryology 179 (1989), S. 571-585 
    Details
    ISSN: 1432-0568
    Keywords: Retina ; Development ; Histogenesis ; Synaptogenesis ; Wallaby
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Retinal differentiation in the pouch young of the wallaby Macropus eugenii was characterized microscopically and morphometrically. Mitosis occurs until early in the second month in the central retina, and until early in the fourth month, peripherally. Separation of the neuroblast layer by the outer plexiform layer did not immediately halt cell division. The retinal surface continued to expand well past the time of cessation of proliferation. Cell death in the ganglion cell layer continued through the fourth month centrally and to nearly five months in the periphery. The major period of cell death was coincident with the segregation of retinal afferents and the refinement of topography in the superior colliculus and dorsal lateral geniculate necleus. Beginning in the third month retinal thickness, measured between the outer limiting membrane and nerve fiber layer declined equally in peripheral and central regions. At all stages the combined thicknesses of the outer and inner nuclear layer in the retinal periphery was greater than that in the center. Together with a late thickening of the inner plexiform layer, the data are consistent with the suggestion that expansion of peripheral non-ganglion cell elements may play a role in development of center to periphery differences in ganglion cell distributions. Retinal differentiation of the wallaby follows the pattern of most mammals. The onset of development of key milestones for the acquisition of retinal function occurred in the sequence: conventional synapse formation prior to ribbon synapse formation in the inner plexiform layer, and photoreceptor outer segment differentiation prior to terminal triad synapse formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315699
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  • 3
    Electronic Resource
    Electronic Resource
    Cell junctions and their role in transmural diffusion in the embryonic chick heart (1971)
    Springer
    Cell & tissue research 120 (1971), S. 463-487 
    Details
    ISSN: 1432-0878
    Keywords: Cardiogenesis ; Cell Junctions ; Permeability ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Studies of cardiogenesis in the chick embryo focus attention upon the intercellular junctions of epicardial, myocardial, and endocardial cells, and the role they play in diffusion across the cardiac wall. Cell membranes of apposed epicardial cells approach as close together as 40 Å; those of the endocardium additionally form focal tight junctions. In the myocardium focal tight junctions are restricted to the apposed membranes of the superficial layer of cells. The majority of close appositions in all parts of the myocardium are 40 Å gap junctions. Desmosomes and fascia adherens are distributed throughout the myocardium. Diffusion of horseradish peroxidase through the epicardium and endocardium occurs primarily through the intercellular junctions. The width of the cleft between cells, 200–300 Å, also permits the diffusion between cells of the larger ferritin particles. Pinocytotic activity, responsible for ferritin transfer across mesothelial and endothelial cells in the adult, is not significant. Tracers injected into the pericardial cavity or vasculature can be observed passing through the heart in the direction of their respective diffusion gradients. Unlike the apical junctions of epithelial cells, to which they have been compared, membrane specializations of the superficial myocytes do not form a seal separating the pericardial cavity, or subepicardial space, from the extracellular spaces of the myocardium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00340585
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  • 4
    Electronic Resource
    Electronic Resource
    The structure and distribution of the cross-striated fibril and associated membranes in guinea pig photoreceptors (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 155 (1979), S. 319-337 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Examination of longitudinally and transversely sectioned photoreceptor cells of the guinea pig retina revealed an aggregate of thin filaments forming a single cross-striated fibril coursing through the full length of the non-receptor portion of the cell. The fibril begins as the ciliary rootlet from the region of the basal body of the connecting cilium. From the basal body it passes between the mitochondria of the ellipsoid and along the Golgi zone of the myoid region of the inner segment, narrowing from an irregularly shaped bundle to a ribbon-shaped aggregate. The fibril separates into discrete strands, each curving along the nucleus, reuniting into a single bundle to pass down the cell's axon, and terminating deep within the synaptic terminal. The fibril is flanked by two separate membranous saccules, each continuous along nearly its full length. The fibril's extensive course in the guinea pig and its association with continuous membranes necessitates a reexamination of earlier proposals for the function of cross-striated filamentous structures in photoreceptor cells.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001550304
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  • 5
    Electronic Resource
    Electronic Resource
    Human retinal development: Ultrastructure of the outer retinaSupported by grants from the Medical Research Council of Canada and Fight for Sight, Inc., New York. (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 137 (1973), S. 357-385 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The morphogenesis of the outer human retina from 6.5 to 18 weeks of gestational age (16-156 mm) was studied by light and electron microscopy. During this period the retinal pigment epithelium changes from a pseudostratified columnar epithelium, with mitoses at its inner edge, to a single layer of cuboidal cells. Initially, mature pigment granules, premelanosomes, polysomes, rough endoplasmic reticulum and a Golgi complex occupy the epithelial cytoplasm. Lateral epithelial surfaces show infoldings and neighboring epithelial cells are bound at their inner borders by a junctional complex consisting of a zonula occludens and zonula adherens. Later, pigment epithelial development is marked by an increase in cytoplasmic organelle content and the appearance of slender processes at the inner epithelial border. Initially, the outer neural retina is formed by a uniform population of elongated cells containing oval nuclei with multiple nucleoli and, in the cytoplasm, mitochondria, polysomes and the Golgi complex. Cell division is common in the proliferative layer at the outer edge of the posterior neural retina until 120 mm crown-rump length, and cell membrane junctions between outer neuroblasts remain intact during mitosis. Cilia project outwards from outer neuroblasts and invaginate the immediately adjacent pigment epithelium. At 120 mm crown-rump length, differentiating rods, cones and Müller cell processes are distinguishable and developing ribbon synapses and surface contacts are present at the base of the cone prior to outer segment formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001370402
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  • 6
    Electronic Resource
    Electronic Resource
    Phagocytosis of photoreceptor outer segments during retinal development in uteroSupported by the Medical Research Council of Canada. (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 152 (1978), S. 523-527 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The retinal pigmented epithelium of the fetal guinea pig was examined for evidence of phagocytosis and degradation of outer segments. Beginning at the early stages of outer segment formation and continuing through the remaining fetal period, pigment epithelial cells contained large and small phagosomes with multi-lamellated internal structure. Thus, mammalian retinal photoreceptor cells which normally develop and mature in utero in the absence of light undergo a process of phagocytosis of outer segment fragments comparable to that found in species whose retinae mature postnatally outside of the uterus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001520406
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