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  • Ultrastructure  (4)
  • 42.10  (3)
  • Springer  (7)
  • PANGAEA
  • 2020-2024
  • 2020-2023
  • 1975-1979  (7)
  • 1965-1969
  • 1955-1959
  • 1979  (7)
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Publisher
  • Springer  (7)
  • PANGAEA
Years
  • 2020-2024
  • 2020-2023
  • 1975-1979  (7)
  • 1965-1969
  • 1955-1959
Year
  • 1
    ISSN: 1432-0878
    Keywords: Pancreatic endocrine cells ; Enteroendocrine cells ; Ultrastructure ; Cyprinidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pancreatic endocrine cells of Barbus conchonius are concentrated in a large (principal) islet, located near the gall bladder, and in a number of smaller islets. Five types of endocrine cells can be distinguished in these pancreatic islets: B cells, A1 (or D cells), 2 types of A2 cells (A2r cells with round granules; and A2fl cells with flocculent granules) and a scarce 5th cell type. The hormones produced by B and A2fl cells are probably insulin and glucagon respectively. The A2r cell contains granules with the same diameter as the granules of the enteroendocrine type III cell of the gut. Both cell types may resemble the enteroglucagon-producing EG cell of mammals. The function of the A1 cells, which are frequently found without secretory granules, and of the 5th cell type, will be discussed. The pancreatic islets of B. conchonius are strongly innervated, which suggests the presence of a direct nervous control system. Some intermediate or mixed cells containing exocrine and endocrine A2r granules are found contiguous with the principal islet. The origin of pancreatic endocrine cells is also the subject of discussion.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 18 (1979), S. 291-296 
    ISSN: 1432-0630
    Keywords: 02 ; 42.10 ; 41
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The connection of the natural resonances and the symmetry group of the cross-section of the diffracting-cylinders is established. As is done in spectroscopy, selection rules for the propagation directions of the diffracted field are deduced. Some remarks about the case of propagating modes along a dielectric rod are also made.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 18 (1979), S. 53-62 
    ISSN: 1432-0630
    Keywords: 42.82 ; 42.10 ; 42.80 ; 85.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The characteristics of slab waveguide tapers with finite-thickness cladding are investigated by approximating the tapered section as a series of uniform five-layer waveguides with successive changes in the core and cladding thickness. The behaviour of multimode coupling and transmission characteristics for typical tapers are studied in detail by computer simulation, employing parameter values appropriate for practical systems. Strong coupling and efficient conversion between core and cladding modes are demonstrated. In addition, it is shown that for tapers of moderate slopes, the nearest-neighbour coupling approximation is quite adequate for the calculation of the individual mode amplitudes. For steeper tapers, however, additional neighbouring modes have to be taken into account, and the modal energy tends to spread further towards the higher-order modes. It is also demonstrated that relatively large step-size can be used in the iterative numerical calculations. This, in conjunction with the choice of an appropriate coupling scheme (e.g., the nearest-neighbour approximation for mild tapers), makes it possible to reduce the cost of computer simulation. The relevance of the present analysis to fiber tapers is also discussed.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 20 (1979), S. 345-351 
    ISSN: 1432-0630
    Keywords: 42.10 ; 42.82
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A short description of a rigorous electromagnetic theory based on the numerical integration of a differential system is given. It allows the study of the stop-bands of a corrugated waveguide. Dispersion curves in the first and the second-order stop-bands are computed for various periodic waveguides. A selection rule due to the symmetry of the corrugation is found. The reflection of a plane wave by the guide is examined. It is demonstrated that under peculiar circumstances, the reflection coefficient has a modulus equal to unity.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 198 (1979), S. 373-380 
    ISSN: 1432-0878
    Keywords: Ventral cochlear nucleus ; Calyceal processes ; Flattened synaptic vesicles ; Ultrastructure ; Morphometric study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In this paper we report the appearance of flat vesicle-containing endings in aldehyde-fixed ventral cochlear nucleus of rats with qualitative and quantitative properties suggesting they should be identified as calyceal processes. Their synaptic vesicles are elongate and significantly smaller than the vesicles in the calyces of Lenn and Reese (1966). Therefore these endings are flat vesicular calyceal processes, possibly of inhibitory function.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 199 (1979), S. 249-256 
    ISSN: 1432-0878
    Keywords: Hepatocytes ; Birds ; Ultrastructure ; Estrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Administration of estradiol-17-β induces the synthesis of vitellogenin in primary cultures of chick embryo liver. The ultrastructural changes accompanying steroid induced vitellogenin synthesis were investigated in hepatocytes cultures incubated for 0, 12 and 24 h following hormonal treatment. Both electron microscopy and immuno-chemical techniques were used. The immuno-fluorescence data indicate that the cultures contain a cell population of 90–95% hepatocytes, both in control and estradiol-treated groups. Ultrastructurally, cultured hepatocytes are similar to in vivo ones, except for a reduced accumulation of storage materials, glycogen and lipids. In the estradiol-treated cultures hepatocytes show an accumulation of free ribosomes, enlargement of rough endoplasmic reticulum, and development of the Golgi apparatus. The data are discussed in relation to previous biochemical findings.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 196 (1979), S. 449-454 
    ISSN: 1432-0878
    Keywords: Gastric epithelium (Rat) ; Phagocytosis ; Cell loss ; Aspirin ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Gastric surface epithelial cells (SEC) from fed rats, from rats fasted for 16 h and from mucosae exposed in an ex-vivo chamber to 16 mM aspirin for 5 min were examined by transmission electron microscopy. SEC have the capability to phagocytose adjacent epithelial cells and parietal cells. Phagocytosis is rare in mucosae from fasted animals but common in fed animals or after brief exposure to aspirin. Phagocytic capabilities are not restricted to the progenitor zone but exist throughout the surface epithelium. Phagocytosis may provide a mechanism for the removal of damaged or senescent cells from the surface epithelium.
    Type of Medium: Electronic Resource
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