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  • 1
    ISSN: 1432-1106
    Keywords: Inferior olive ; Cerebellum ; Flocculus ; Rabbit ; Eye movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary After the dorsal cap and adjacent ventrolateral outgrowth regions of the inferior olive had been chronically destroyed in the rabbits, the eye movements evoked by local stimulation of the flocculus were reduced in amplitude and reversed in direction, indicating that the inhibition by flocculus Purkinje cells of vestibulo-ocular relay neurons could no longer be actuated by the stimulation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Vestibular ; Ocular ; Optokinetic ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Dynamic characteristics of the horizontal vestibulo-ocular reflex (HVOR), the optokinetic response (OKR), and their interactions were investigated in alert albino rabbits. For stimulation of the horizontal semicircular canals, the whole rabbit was rotated sinusoidally on a motor-driven turntable at peak-to-peak amplitudes of 5 ° to 30 ° over a frequency range of 1/30 to 1/2 Hz. Optokinetic stimulation was provided by a narrow vertical slit light source presented in front of the eye to be tested. The evoked horizontal eye movements were observed and measured by means of a closed circuit television system adapted to provide an analog signal proportional to the eye movement. The net HVOR was obtained by rotation of the turntable in darkness and the net OKR by rotation of the light source. Combining rotation of the turntable with a stationary light source immediately increased the gain and reduced the phase shift of the HVOR. The light source moving in phase with the turntable, but at twice the angular amplitude, reduced the gain and advanced the phase of the HVOR. Eye movement curves of the HVOR modified by a fixed or moving slit light could be reconstructed approximately by a linear combination of the net HVOR and OKR.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Adaptation ; Vestibular ; Ocular ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Adaptability of the horizontal vestibulo-ocular reflex (HVOR) and the optokinetic response (OKR) was examined in alert albino rabbits during sustained runs lasting 5–12 h under four different stimulus conditions. (1) Sinusoidal rotation of the rabbit in darkness by 5 ° at 1/10 Hz, or (2) sinusoidal movement of a vertical slit light by 2.5 ° or 5 ° at 1/10 Hz around the optical axis of the stationary rabbit, affected the gain of neither the HVOR nor the OKR. (3) Combination of the stimulus as in (1) with the stationary slit light increased the gain of the HVOR gradually. A plateau at about 140% of the initial control was reached in 5 h. (4) Combination of the stimulus as in (1) with the slit light movement by 10 ° in phase with the turntable decreased the HVOR gain gradually, a plateau being obtained at about 70 % of the initial control in 5 h. Changes of the HVOR gain induced in conditions (3) and (4) were not frequency-specific and accompanied by no significant modification of either the gain or phase of the OKR or the linear property of HVOR-OKR interaction. A small but significant change of the HVOR phase was also detected under the condition (3) but not (4).
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 45 (1982), S. 233-242 
    ISSN: 1432-1106
    Keywords: Gerebellum ; Flocculus ; Eye movement ; Kainic acid ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The horizontal vestibulo-ocular reflex (HVOR) and optokinetic response (OKR) were examined in alert albino rabbits following unilateral flocculectomy. Chemical flocculectomy with local application of kainic acid was used to avoid the retrograde degeneration of inferior olive neurons that accompanies surgical flocculectomy. Effects of chemical flocculectomy, however, were identical to those of surgical flocculectomy. The following functional deficiencies were observed in the movements of the ipsilateral eye: (1) reduction of the HVOR gain; (2) increased lag of the HVOR phase; (3) increased non-linearity of the relationship between the HVOR gain and the amplitude of turntable rotation; (4) decreased OKR gain; (5) delay with increased variation in the OKR phase; (6) impairment of rapid visual-vestibular interaction; (7) loss of the adaptation of the HVOR. Only a transient depression of the HVOR gain was seen in the contralateral eye. Control experiments with lesions in the paraflocculus, nodulus, and uvula, or lobules VI and VII, revealed no such deficiencies, except that lesions in the nodulus and uvula produced marked advancement of the HVOR phase. The effects of flocculectomy are consistent with present knowledge of both neuronal circuitry and activity of the rabbit flocculus.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 282 (1990), S. 402-407 
    ISSN: 1432-069X
    Keywords: Electron microscopy ; Culture ; Hair cells ; Growth ; Differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cultured hair cells from 4-day-old C3H mice were studied by electron microscopy. The hair roots isolated from the skin by collagenase digestion were dispersed into a cell suspension by treatment with a mixture of trypsin and ethylenediaminetetraacetate. The cells were cultured in MCDB-153 (a medium containing seven growth factors) for 1, 3, 6 or 13 days. The number of cultured cells on day 3 was twice that on day 1, and stayed at the same level until day 13. By electron microscopy, some of the cells cultured for 1 day were seen to be undifferentiated and others already showed differentiation into various hair structures. Such differentiated cells disappeared on day 3 and most of the cells cultured for 3 days were undifferentiated. Cells cultured for 6 days were differentiated showing inner root sheath cell, hair cortical cell and medulla cell structures. The characteristics of these cultured cells corresponded well to those of in vivo cells of the hair tissues from the back skin of 7-day-old C3H mice. On day 13 degeneration occurred in the cultured cells. In none of these cultures were mesenchymal cells, such as fibroblasts, found. The present electron microscopic study reveals that immature cells obtained from mouse hair tissues proliferate in vitro and differentiate into several subpopulations corresponding to those of in vivo cell layers of hair tissues. The present culture technique may be useful for studies of hair cell growth and differentiation.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 284 (1992), S. 290-296 
    ISSN: 1432-069X
    Keywords: Cepharanthine ; Minoxidil ; Culture ; Hair cells ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of cepharanthine and minoxidil on proliferation, differentiation and keratinization of cultured cells from the murine hair apparatus were examined electron microscopically. Both cepharanthine and minoxidil stimulated cell proliferation and delayed initiation of differentiation and keratinization of the cultured cells. On day 6, most control cells (87%) cultured in a 0.03 mM calcium medium without cepharanthine and minoxidil were differentiated into several subpopulations corresponding to those of in vivo cell layers of the hair apparatus, while most of the cells cultured with cepharanthine (71%) or minoxidil (70%) were still immature. On day 13, the number of degenerated cells increased (63%) in the control culture, whereas in the culture treated with cepharanthine or minoxidil, cell degeneration scarcely occurred (5% and 8%, respectively). Differentiated cells having tonofilaments were often observed in the cepharanthine- and minoxidil-treated cultures (76% and 72%, respectively). Elevation of extracellular calcium up to 1.0 mM induced keratinization (34%) in the control culture on day 6, while no keratinized cells were observed in the cepharanthine- or minoxidil-treated culture. On day 13 keratinization similarly occurred in the cultures with cepharanthine (30%) or minoxidil (48%). These results show that both cepharanthine and minoxidil may directly influence proliferation, differentiation and keratinization of cultured cells from the hair apparatus.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 281 (1989), S. 254-259 
    ISSN: 1432-069X
    Keywords: Innermost cell layer ; Tonofilaments ; Huxley's cells ; Henle's cells ; Anagen hair follicles ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To elucidate the biologic roles and further cytologic characteristics of the innermost cell (IMC) layer of the outer root sheath (ORS), human anagen hair follicles were ultrastructurally examined. In the lower follicle, the transeversely running tonofilaments in the inner side of the cytoplasm of the IMCs showed a massive accumulation, facing the keratinized part of a Huxley's cell protruding through a Henle's pore. In a rare instance, a spindle-shaped cell was seen between the IMC layer and the keratinized Henle's layer. At the lower isthmus portion, some of the IMCs containing a large number of tonofilaments showed a partial degeneration of the inner side of the cytoplasm. More distally, intercellular spaces between the keratinized IMCs and keratinized Henle's cells were partly dilated and contained amorphous substances. It is suggested that the IMCs in the lower follicle may play a role to support and cover the inner hair structures, tightly as hoops of a barrel. In the isthmus portion, the IMCs may loosely support and guide the keratinized Henle's cells undergoing degeneration.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1106
    Keywords: Vestibulospinal ; VIIIth nerve ; Deiters' nucleus ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anaesthetized rabbits, the medulla was surveyed with recording microelectrodes to identify different types of vestibulospinal tract neurones. Field potentials, unitary extracellular spikes and intracellular potentials were recorded during antidromic stimulation at C1 and C6 segments and during orthodromic stimulation through VIIIth nerve. The lateral and medial vestibulospinal tracts (LVST and MVST) were stimulated discriminately with the method developed in Appendix. On the basis of different axonal courses and conduction velocities, three major groups were distinguished for those cells which were activated monosynaptically by the primary vestibular afferents; 1. fast conducting LVST; 2. fast conducting MVST; and 3. slowly conducting MVST. Three other groups were discriminated for those cells which received only a polysynaptic or no action from primary vestibular afferents. These were; 4. fast conducting LVST; 5. slowly conducting LVST and 6. slowly conducting MVST. All of these six types of VST cells were represented within Deiters' nucleus. Only a relatively small number of MVST cells were found in the medial vestibular nucleus.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1106
    Keywords: Semicircular canal ; Vestibular-ocular inhibition ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anesthetized albino rabbits, electric stimulation of vestibular nerve branches innervating semicircular canals produced not only reflex contraction in certain extraocular muscles, but also a transient relaxation in others. From relaxing muscles was recorded a slow muscle potential that reflected depression of spontaneous spike discharges in muscle fibers. When recorded monophasically, spontaneous spikes of muscle fibers were superposed to form a direct current potential, and depression of the spikes resulted in a transient reduction of this direct current potential, i.e., the slow muscle potential. The slow muscle potential was correlated to the postsynaptic inhibition induced in oculomotor neurons through the vestibulo-ocular reflex arc for the following reasons; its latency was compatible with that of the IPSPs recorded from oculomotor neurons; it was removed by severing axons of the inhibitory second-order vestibular neurons; it was blocked by intravenous injection of picrotoxin as were the IPSPs in oculomotor neurons. By recording slow muscle potentials, a specific canal-muscle relationship for the vestibulo-ocular reflex inhibition of oculomotor neurons was shown to be complementary to that obtained for the vestibulo-ocular reflex excitation.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 24 (1976), S. 257-271 
    ISSN: 1432-1106
    Keywords: Semicircular canal ; Vestibulo-ocular reflex ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anesthetized albino rabbits, ampullary branches of the vestibular nerve were stimulated electrically. Prominent and stable reflex contraction was induced in extra-ocular muscles by applying single current pulses of relatively long duration, 3–5 msec. Survey with a glass microelectrode revealed that, during application of relatively wide pulses to a canal, primary vestibular fibers discharged impulses repetitively at a rate as high as 300–1400/sec and that after being transmitted across second-order vestibular neurons these impulses built up summated EPSPs in oculomotor neurons, large enough to trigger off motoneuronal discharges. From each semicircular canal, prominent reflex contraction was evoked selectively in two muscles; from the anterior canal in the ipsilateral superior rectus and contralateral inferior oblique; from the horizontal canal in the ipsilateral medial rectus and contralateral lateral rectus; and from the posterior canal in the ipsilateral superior oblique and contralateral inferior rectus. Acute lesion experiments indicated that signals for this excitation reached IIIrd and IVth nuclei via three different pathways; from the anterior canal through the ipsilateral brachium conjunctivum, from the horizontal canal through the ipsilateral fasciculus longitudinalis medialis and from the posterior canal through the contralateral fasciculus longitudinalis medialis.
    Type of Medium: Electronic Resource
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