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  • Electronic Resource  (4)
  • 1985-1989  (4)
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  • Electronic Resource  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Vestibular and optokinetic eye movements evoked in the cat by rotation about a tilted axis (1987)
    Springer
    Experimental brain research 66 (1987), S. 522-532 
    Details
    ISSN: 1432-1106
    Keywords: Off-vertical-axis rotation ; Eye movements ; Vestibulo-ocular reflex ; Optokinetic nystagmus ; Otoliths ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Horizontal and vertical eye movements were recorded from cats in response to either a) off-vertical axis rotation (OVAR) at a range of velocities (5–72 deg/s) and a range of tilts (0–60 deg) or b) horizontal (with respect to the cat) optokinetic stimulation (10–80 deg/s), also around a range of tilted axes (0–60 deg). The responses to stopping either of these stimuli were also measured: post-rotatory nystagmus (PRN) following actual rotation, and optokinetic after nystagmus (OKAN) following optokinetic stimulation. The response found during OVAR was a nystagmus with a bias slow-phase velocity that was sinusoidally modulated. The bias was dependent on the tilt and reached 50% of its maximum velocity (maximum was 73±23% of the table velocity) at a tilt of 16 deg. The phase of modulation in horizontal eye velocity bore no consistent relation to the angular rotation. The amplitude of this modulation was roughly correlated with the bias with a slope of 0.13 (deg/s) modulation/(deg/s) bias velocity. There was also a low-velocity vertical bias with the slow-phases upwardly directed. The vertical bias was also modulated and the amplitude depended on the bias velocity (0.27 (deg/s) modulation/ (deg/s) bias velocity). When separated from the canal dependent response, the build up of the OVAR response had a time constant of 5.0±0.8 s. Following OVAR there was no decline in the time constant of PRN which remained at the value measured during earth-vertical axis rotation (EVAR) (6.3±2 s). The peak amplitude of PRN was reduced, dependent on the tilt, reaching only 20% of its EVAR value for a tilt of 20 deg. When a measurable PRN was found, it was accompanied by a slowly-emerging vertical component (time constant 5.4±2s) the effect of which was to vector the PRN accurately onto the earth horizontal. OKN measured about a tilted axis showed no differences in magnitude or direction from EVAR OKN even for tilts as large as 60 deg. OKAN following optokinetic stimulation around a tilted axis appeared normal in the horizontal plane (with respect to the animal) but was accompanied by a slowly emerging (time constant 4.1±2 s) vertical component, the effect of which was to vector the overall OKAN response onto the earth horizontal for tilts less than 20 deg. These results are compared with data from monkey and man and discussed in terms of the involvement of the velocity storage mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00270685
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The contribution of the horizontal semicircular canals to the response to off-vertical-axis rotation in the cat (1988)
    Springer
    Experimental brain research 71 (1988), S. 147-152 
    Details
    ISSN: 1432-1106
    Keywords: Eye movements ; Vestibulo-ocular reflex ; Otoliths ; Off-vertical-axis rotation ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The response to off-vertical-axis rotation (OVAR) was measured in cats under circumstances in which the signals from the horizontal semicircular canals and otoliths were opposed. Opposition was achieved by sudden acceleration or deceleration during constant velocity OVAR. The degree of opposition was expressed as a canal/otolith ratio where a ratio of unity indicated agreement. For a canal/otolith ratio of 1, the OVAR gain (eye velocity/ stimulus velocity) was 0.73 (±0.13). The steady-state OVAR response was, however, reduced if the canals and otoliths were opposed. The reduction depended on the degree of opposition with a fall-off of 0.15 gain/(unit of canal/otolith ratio). These findings are discussed with respect to the central velocity store and the mechanism underlying the generation of the OVAR response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00247529
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Physiological and biochemical changes in Calanus hyperboreus from Jones Sound NWT during the transition from summer feeding to overwintering condition (1985)
    Springer
    Polar biology 4 (1985), S. 99-106 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Several biochemical and physiological characteristics of stage V and female adult Calanus hyperboreus from two different depth ranges (0–50 m and 200–500 m) were compared at a time near the peak of the summer pelagic algal bloom in Jones Sound, and again one month later, when the near surface chlorophyll levels were low and most copepods had migrated to their overwintering dephts. For a given stage deep water animals were larger and had higher total lipid levels than did surface animals. Feeding activities, as evidenced by gut pigment contents, may be lower in animals at depth, although potential digestive activities, as expressed in the levels of three digestive enzymes, were not very different either in different stages or at different depths. Respiration rates in animals that had migrated down for the winter were not much lower than in those at the surface although energetic considerations suggest that they may decrease later. Ammonia excretion rates however, changed dramatically. Surface, feeding animals had the highest rates and deep water animals in September had undetectably (〈1 ng atom ammonia nitrogen animal-1 · day-1) low rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00442907
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Grazing, defecation and excretion rates of copepods from inter-island channels of the Canadian Arctic archipelago (1988)
    Springer
    Marine biology 99 (1988), S. 333-340 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Zooplankton (〉800 μm) and water samples were collected at night at eleven stations in Parry Channel and adjacent waters, between 28 August and 14 September 1986. Chlorophyll concentrations varied between ≈17 μg l-1 at the surface at one station in Wellington Channel, Canada, and ≈1.5 μg l-1 throughout the top 30 m at one station in Byam Martin Channel, Canada. In tows from 0 to 50 m the zooplankton community at all stations was dominated by varying proportions of three species,Calanus hyperboreus, C. glacialis andMetridia longa. Levels of chlorophyllderived pigments inC. hyperboreus Stages V, IV and III were correlated with the concentration of chlorophyll at the chlorophyll maximum. Defecation rate constants, measured for the different stages where present, were variable but not correlated with ambient chlorophyll concentrations. Ammonia excretion was measured simultaneously for the communities in which defecation was being measured in the invividual species and stages. In these experiments the rate of ammonia accumulation decreased significantly over the period during which the copepods were actively defecating (usually the first 3 h) and then tended to a constant level (over the next 18 to 20 h). The time courses of ammonia accumulation could be described by a model comprised of the sum of a straight line and a saturating curve. For seven experiments the ammonia release given by the asymptote of the saturating component was correlated with the estimate of community defecation, obtained by summing the individual defecations, suggesting that the two processes were closely associated. Weight specific defecation and weight specific “defecation-associated” ammonia excretion were both correlated with ambient chlorophyll concentration. The ratio of initial to basal ammonia excretion rate varied between 2 and 20, so that “defecation-associated” ammonia release may be important in the estimation of in vivo nitrogen excretion or regeneration rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02112125
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    Paper (German National Licenses)
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