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  • 1
    Electronic Resource
    Electronic Resource
    Use of plaid patterns to distinguish the corticofugal and direct retinal inputs to the brainstem optokinetic nystagmus generator (1991)
    Springer
    Experimental brain research 86 (1991), S. 324-332 
    Details
    ISSN: 1432-1106
    Keywords: Vision ; Optokinetic nystagmus ; Eye movements ; Plaids ; Brainstem ; Motion perception ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have recorded the direction of optokinetic nystagmus (OKN) elicited by moving plaid patterns in order to dissociate the pathways that mediate horizontal OKN. The plaids used comprised two drifting sinusoidal gratings arranged such that their individual directions of drift were very different from the direction of coherent motion of the overall pattern. The direction of OKN with binocular viewing was close to the mean of the component directions, suggesting a dominant influence of cortical visual neurons that respond to oriented one-dimensional components of the image. But the direction of OKN was consistently shifted slightly towards the direction of motion of the overall pattern, suggesting a secondary influence responsive to pattern direction. OKN recordings obtained during monocular viewing suggest that this secondary influence reflects the direct retinal pathway to the brainstem structures mediating OKN.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228955
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Physiological adaptations of an under-ice population of Pseudocalanus in Barrow Strait (N.W.T) to increasing food supply in spring (1990)
    Springer
    Polar biology 10 (1990), S. 561-570 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Zooplankton and water samples were collected at weekly intervals between April 25 and May 30, 1986 in Barrow Strait, N.W.T. (Canadian Arctic Archipelago). In tows from 0–30 m, the zooplankton community (〉202 μm) was dominated by Pseudocalanus. The population was apparently growing and developing as shown by an increase in the proportion of adults (stage VI) and decreases in the proportion of stages III, IV, and V as the season progressed. Respiration and excretion rates of the Pseudocalanus populations were probably linked, there being an immediate increase in excretion rate, accompanying an increase in feeding rate when chlorophyll concentrations increased, which was followed by a smaller increase in respiration rate after a time lag. Hence, there was a large decrease in the O∶N ratio. Increased metabolism coincided with changes in the population structure, as did protease and bodily protein, but could not be clearly linked to dietary acclimation. Only laminarinase activity could be statistically related to an identifiable fraction of potential nutritional value in the water, particulate soluble carbohydrate, but neither showed overall seasonal change.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239367
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    An increase in the concentration of hepatic iron during the metamorphosis of the lamprey Geotria australis is accompanied by increased superoxide dismutase activity (1990)
    Springer
    Fish physiology and biochemistry 8 (1990), S. 451-457 
    Details
    ISSN: 1573-5168
    Keywords: iron ; superoxide dismutase ; lamprey ; liver ; metamorphosis ; Geotria australis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The concentration of total non-haem iron and its ferritin iron component, and the activity of the enzyme superoxide dismutase (SOD), were measured in the livers of ammocoetes, metamorphosing animals (stages 1–7) and recently metamorphosed downstream migrants of the lamprey Geotria australis. Total non-haem iron in the liver rose significantly from 0.15–0.55 μg.mg wet weight−1 in ammocoetes and metamorphosing stages 1–3 to 2.2–2.9 μg.mg−1 in stages 5–7 and to 8.8 μg.mg−1 in downstream migrants. The comparable values for ferritin iron were 0.06–0.26, 1.4–2.0, and 5.3 μg.mg−1. Superoxide dismutase activity fell sharply from 0.39 μg.mg−1 in large ammocoetes to between 0.07 μg.mg−1 in stage 1 and 0.15 μg.mg−1 in stage 6, before rising significantly to 0.26 μg.mg−1 in stage 7 and 0.35 μg.mg−1 in downstream migrants. The sharp fall in SOD activity at the beginning of metamorphosis is assumed to be related to the marked decline in plasma iron which occurs at the onset of this non-trophic phase in the life cycle. It is proposed that the subsequent increase in SOD activity in the liver of G. australis with increasing iron represents a mechanism aimed at reducing the potentially toxic effects of iron accumulation. This view is consistent with the significant and positive correlation found between both total non-haem and ferritin iron and SOD activity in the liver of non-trophic animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00003401
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    Paper (German National Licenses)
    Fulltext
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