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  • 1
    Electronic Resource
    Electronic Resource
    Auditory nerve activity and cochlear morphology after noise exposure (1979)
    Springer
    European archives of oto-rhino-laryngology and head & neck 224 (1979), S. 111-116 
    Details
    ISSN: 1434-4726
    Keywords: Auditory nerve fiber ; Acoustic trauma ; Hair cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Four chinchillas were exposed for 5 days to an octave band of noise centered at 4 kHz and having an SPL of 86 dB. After a recovery period of approximately 6 months, behavioral audiograms were obtained and auditory nerve fiber activity was recorded. The animals were killed and the cochleas embedded in plastic to obtain a surface preparation and 1 μ radial sections of the organ of Corti. Behavioral threshold shifts ranged from 5 to 20 dB at frequencies between 4 and 11 kHz. Auditory nerve fiber thresholds were elevated up to 70 dB for units with characteristic frequencies between 4 and 14 kHz. Units with higher and lower characteristic frequencies had normal thresholds. Cochleagrams showed narrow lesions of inner and/or outer hair cells over approximately a 1 mm distance. A comparison of the three realms of data revealed the following: (1) The greatest threshold shifts from the noise exposure were seen in the single nerve fiber thresholds while the smallest shifts were seen in the behavioral thresholds, (2) the greatest behavioral and neural threshold shifts and greatest cochlear damage occurred 1 octave above the center frequency of the noise exposure, and (3) based on the frequency-place map of the chinchilla cochlea, the range of fibers with elevated thresholds exceeded the extent of the OHC lesion. A number of anatomical changes were seen that effectively increased the extent of the damage found in the chochleagram. These changes included: distortions in the surface topography of the organ of Corti affecting the orientation of IHC; missing pillar cells in the presence of normal OHC and/or IHC and protrusion of the IHC cuticular plate into the subtectorial space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00455233
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrastructural changes to the cochlea resulting from impulse noise (1981)
    Springer
    European archives of oto-rhino-laryngology and head & neck 230 (1981), S. 273-278 
    Details
    ISSN: 1434-4726
    Keywords: Acoustic trauma ; Cochlear pathology ; Hair cell ; Stereocilia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Following impulse noise trauma to chinchillas, observation of plastic-embedded surface preparations of the organ of Corti showed no consistent relationship between cochlear hair cell loss and permanent hearing loss (Hamernik et al. 1980). In some animals there was a loss of hearing when hair cells were present. The cochleas from that experiment were examined with transmission electron microscopy to determine at the ultrastructural level if there was damage to the sensory cells that would explain the change in threshold sensitivity. Ultrastructural changes in cochlear hair cells include an increase in lysosomes, multivesicular bodies, vacuolization of subsurface cisternae, and proliferation of Hensen bodies. These changes are observed in all experimental animals. Alterations to the ultrastructure of the stereocilia vary from animal to animal and on the outer hair cells, the changes include loosening of the stereocilia membranes, loss of stiffness, fusion of the stereocilia and disintegration of the rootlets. These changes are observed only in animals that have a permanent threshold shift after noise trauma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00456329
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Division patterns in the thallus ofPelvetia compressa embryos and the effects of gravity (1998)
    Springer
    Protoplasma 203 (1998), S. 112-117 
    Details
    ISSN: 1615-6102
    Keywords: Brown alga ; Cleavage plane ; Embryogenesis ; Gravity ; Microtubules ; Spindle orientation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The pattern of divisions in the thallus ofPelvetia compressa embryos was determined with respect to the embryonic growth axis. To detect all possible division planes, embryos were viewed from two vantages which permitted observations of (1) the thallus pole and (2) the longitudinal embryonic profile. Following formation of rhizoid and thallus cells by any asymmetrical division transverse to the embryonic axis that is established prior to any divisions, the thallus cell divided twice along the embryonic axis (axial divisions) in orthogonal planes, and then divided transverse to the growth axis. This division pattern produced an eight-cell thallus with four cells in each of two layers. The spatial relation between gravity and the first axial division was investigated, and gravity was found to have little effect on the alignment of this division. The reproducible pattern of divisions in the thallus indicates spatial control of spindle positioning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01280593
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    Paper (German National Licenses)
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