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  • Electron microscopy  (2)
  • Organ of Gabe  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 151 (1977), S. 109-118 
    ISSN: 1432-0568
    Keywords: Iris ; Mesenchymal cells ; Chicken embryo ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The iris anlage of 3–10 day old chicken embryos was studied by both light and electron microscopy. Serial semithin sections showed that some of the mesenchymal cells overlying the eye cup moved into the primitive eye cavity by the 3rd day of incubation. On the 4th day some of these cells came into close contact with the basement membrane of the dorsal iris epithelium. The bases of the epithelial cells were flat at this stage. Towards the 10th day they formed cytoplasmic processes which did not penetrate the basement membrane. Fine mesenchymal cytoplasmic processes and a large number of extracellular fibrils developed in the epithelial-mesenchymal interface. The fine mesenchymal processes came into close contact with the basement membrane of the posterior iris epithelium but did not penetrate it. Collagen-like material was observed within the cisternae of the rough ER of the mesenchymal cells at certain stages of development. Both, the mesenchymal cells and the collagen fibrils adjacent to the posterior iris layer disappeared by the 10th day when the entire iris epithelium was completely pigmented. The possible origin of the collagen fibrils and the differentiation of the posterior iris epithelium are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 147 (1975), S. 177-187 
    ISSN: 1432-0568
    Keywords: Iris ; Melanogenesis ; Chicken embryo ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The iris anlage of 2–10 and 15 days old chicken embryos were studied histochemically, and by both light and electron microscopy. Light microscopic serial sections showed that pigmentation began at the outer layer of the posterior eye pole and progressed from there forwards to the optic cup margin. The entire outer layer of the optic cup as well as the pupillary margin were completely pigmented by the 4th day of incubation. By the 10th day the posterior iris epithelium was totally pigmented. Electron microscopical studies showed that the first premelanosomes appeared at about the 3rd day of incubation in the anterior iris anlage with the exception of the pupillary margin. It could be shown that melanogenesis progressed through the following steps: premelanosomes, followed by tyrosinase activity in a Golgi-associated system of smooth endoplasmic reticulum (GERL) and small vesicles and finally differentiation of the melanosomes. The possible origin of the premelanosomes and the formation of melanin are discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 132 (1972), S. 273-285 
    ISSN: 1432-0878
    Keywords: Diplopoda ; Organ of Gabe ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung 1. Das Gabesche Organ von Schizophyllum sabulosum ist paarig und liegt im seitlichen Clypeolabrum. Es wird von Axonen des Nervus labri medialis erreicht, der vorher Seitenzweige abgegeben hat. 2. Die Axone gehören neurosekretorischen Zellen des Protocerebrum an und enthalten Neurosekret. Die Elementargranula sind recht gleichmäßig ellipsoid, der große Durchmesser beträgt ca. 1200 Å. Die Axone enden im Organ und stellen dessen extrinsische Komponente dar. 3. Außerdem gibt es zwei intrinsische Zelltypen: 1) Drüsenparenchymzellen mit axonartigen Fortsätzen und 2) gliaartige Zellen. Die Parenchymzellen bilden Sekret in Form opaker Vakuolen, die deutlich größer als die Neurosekretgranula sind. Auffällig ist das überwiegend vesikuläre endoplasmatische Reticulum. Die Mitochondrien liegen in der Nähe von myelinähnlichen Körpern; ihre Außenmembran ist stellenweise vakuolig vorgewölbt. Die axonartigen Fortsätze enthalten viele längsorientierte Mikrotubuli. 4. Die langen Fortsätze der gliaartigen Zellen umhüllen die Parenchymzellen und die extrinsischen Axone meist in mehreren Schichten. Es gibt aber auch Bereiche, in denen vor allem die Fortsätze der Parenchymzellen und die extrinsischen Axone nackt sind. 5. Das Organ ist gegen das umgebende Hämocoel von einer dicken, lamellierten Stromahülle abgegrenzt. Auch Interzellularräume sind mit Stroma gefüllt. 6. Das Organ wird mit der Cerebraldrüse einiger Chilopoden und gewissen endokrinen Organen anderer Diplopoden und Insekten verglichen.
    Notes: Summary 1. The paired organ of Gabe of Schizophyllum sabulosum is situated in the lateral clypeolabrum. It is innervated by axons of the medial labral nerve, which divides in several branches before reaching the organ. 2. Axons extend from neurosecretory cells of the protocerebrum and contain neurosecretory droplets, which are almost ellipsoid and about 1,200 Å in diameter. The axons terminate in the organ and constitute its extrinsic elements. 3. In addition, there are two types of intrinsic cells: (1) parenchyma cells with axon-like processes and (2) glia-like cells. The parenchyma cells produce secretory material in the form of opaque vacuoles, which are clearly larger than the neurosecretory granules. The preponderantly vesicular endoplasmic reticulum is conspicuous. Also characteristic are the mitochondria, whose superficial membranes are expanded locally, and which lie in the near vicinity of myeline-like bodies. The axon-like processes contain many microtubuli oriented in longitudinal direction. 4. The slender processes of the glia-like cells envelop both parenchyma cells and extrinsic axons usually in several layers; but there are also regions in which the processes of the parenchyma cells and, above all, the extrinsic axons are naked. 5. The organ is delimited from the surrounding hemocoele by a thick laminated stroma. Intercellular spaces are also filled with stroma. 6. The organ is compared with the cerebral gland of some chilopods and with certain endocrine organs of other diplopods and insects.
    Type of Medium: Electronic Resource
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