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  • 1995-1999  (4)
  • 1950-1954
  • 1995  (4)
  • 1950
  • acidification  (2)
  • Barley  (1)
  • Contralateral  (1)
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  • 1995-1999  (4)
  • 1950-1954
Year
  • 1995  (4)
  • 1950
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Effect of reversible dorsal cold block on the persistence of inhibition generated by spinal reflexes (1995)
    Springer
    Experimental brain research 107 (1995), S. 205-214 
    Details
    ISSN: 1432-1106
    Keywords: Motoneuron ; Stretch reflex ; Cutaneous ; Contralateral ; Spinal ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of bilateral focal cooling of dorsolateral thoracic spinal cord on segmental reflex pathways to the triceps surae muscles were assessed in decerebrate cats from the reflex forces produced by single shocks or trains of electrical stimuli applied to the ipsilateral caudal cutaneous sural and the contralateral tibial nerves. The validity of the dorsal cold block technique as a substitute for acute surgical dorsal hemisection was established by showing that focal cooling reliably reproduced the stretch-induced “clasp knife” inhibition of triceps surae reflexive force seen following dorsal hemisection. Under control (warm) conditions, the inhibitory components of electrically evoked ipsilateral sural and contralateral tibial reflexes faded rapidly during sustained trains, with a resultant production of large-amplitude reflex force as measured from either the entire triceps surae or from the medial gastrocnemius muscle alone. Dorsal cold block greatly reduced the amplitude of reflexive force evoked by sustained electrical stimulation of either nerve. Indeed, the cold block completely reversed the sign of train-evoked reflexes to a net inhibition of reflex force output in one-half of the sural and one-half of the contralateral tibial stimulation experiments. Peak transient forces evoked by single shocks to the sural or contralateral tibial nerves were also sometimes reduced, but this result was more variable than for prolonged nerve stimulation. The persistence of activity in segmental inhibitory pathways during dorsal cold block, as indicated by instances of reflex sign reversal, suggests that descending bulbospinal pathways traversing the dorsolateral funiculi may be responsible for “fading” of segmental inhibitory reflex components in decerebrate cats with intact spinal cords during sustained afferent input. The possibility that the enhanced magnitude and duration of segmental inhibition during cold block will increase the likelihood of disruption of the size principle for motoneuron recruitment is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230042
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Nucleolar transformation in plants grown on clinostats (1995)
    Springer
    Protoplasma 185 (1995), S. 194-204 
    Details
    ISSN: 1615-6102
    Keywords: Barley ; Nucleoli ; Proteins ; Roots ; Stress ; “Weightlessness”
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cells of carrot calli (Daucus carota L.) grown on clinostats (simulated weightlessness) exhibit increases in nucleolar number and volume. In clinostat-grown whole barley plants (Hordeum vulgare L. cv. Steptoe), nucleoli in ∼70% of root meristem and root cortical cells in the 1 mm root apex exhibit multiple nodulations after one day of growth. The nucleolar nodules (1.1 μm mean diameter) are densely and finely fibrous, distinctly different from the nucleolus in which the content is so compact that the granular component is masked. Control nucleoli (from vertically rotated and stationary seedlings) rarely exhibit nodule-like protrusions, are not compact, and contain a well defined granular component. Proteins that are heat soluble, characteristic of many stress responses, rapidly increase in barley grown on clinostats. Barley growth on clinostats is slowly and steadily inhibited. There is no difference between vertically rotated and stationary controls for any of the parameters measured, indicating that clinostat motion per se does not affect significantly barley development. The evidence taken together suggests that barley plants germinated and grown on clinostats are stressed, the effects of which are expressed sequentially by alteration of nucleolar morphology, increased production of heat-soluble proteins, and decreased plant growth. Similar stress-related changes may be expected to occur in plants subjected to weightlessness during space flight. It is therefore of interest that nucleoli in wheat roots (Triticum aestivum L. cv. Broom) obtained from the space flight IML-1 mission show irregularity that is not observed in any of the ground controls for the flight experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01272860
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The role of sea-salts in enhancing and mitigating surface water acidity (1995)
    Springer
    Water, air & soil pollution 85 (1995), S. 553-558 
    Details
    ISSN: 1573-2932
    Keywords: Sea-salts ; acidification ; Scottish catchments ; aluminium ; salmonids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Enhancement of the acidity of fresh waters due to sea-salt “episodes” has been reported in western regions of Scotland, Ireland and Norway and eastern regions of Canada and the United States of America. In all cases these short-term pH depressions have been ascribed to cation-exchange processes in catchment soils whereby sodium ions displace acidic cations (H+, Al3+) resulting in a lowering of the Na/Cl ratio in run-off water. Studies of sea-salt episodes in different catchment types of similar sensitivity in Scotland show significant variations in chemical responses, especially in terms of acidification status. Catchments with high background salt content, in a low sulphur deposition area, show only a small increase in acidity with negligible aluminium release and most of the sodium retention matched by Ca and Mg release. Catchments in intermediate deposition areas, with low background salt levels, exhibit smaller sodium retention with increased leaching of acidity and labile aluminium. High non-marine S deposition sites, with intermediate background salt levels, reveal high levels of acidity and aluminium leaching associated with some calcium leaching and evidence of Mg retention. Mitigation of acidification occurs at sites with high background sea-salt levels (eg north west Scotland) where acidic deposition is selectively retained in catchment soils. Non-marine sulphate values in run-off are therefore much lower (often producing negative values) than those predicted from current S deposition values. Consequently such sites are presently producing false exceedances of freshwater Critical Loads when current S deposition values are used. Future reductions in S deposition will probably affect the adsorption characteristics at these sites with consequent effects on sulphate leaching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00476887
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The consequences of liming a highly acidified catchment in central Scotland (1995)
    Springer
    Water, air & soil pollution 85 (1995), S. 1015-1020 
    Details
    ISSN: 1573-2932
    Keywords: acidification ; liming ; catchment ; fish ; Scotland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Research during the mid 1980s identified acidified, forested catchments in central Scotland whose hydrochemistry was not capable of supporting native fish populations. Calcium concentrations were around 20 μeq l−1, less than the suggested critical value of 50 μeq l−1, with hydrogen concentrations around 70 μeq l−1, greater than the critical value of about 30 μeq l−1. Limestone was applied by aerial application to the source areas of selected streams in 1990 with around 5% (15 ha) of the total catchment area of 270 ha treated at 10 tonnes ha−1. Stream monitoring, carried out over the period 1989–1995, showed an immediate response to liming followed by a progressive decline. Calcium values were elevated to 〉150 μeq l−1 and hydrogen concentrations reduced to 20 μeq l−1, reverting in time towards pre-liming values. Although salmonid survival was improved during low flow conditions in summer, only a few fry survived to the autumn as acid episodes increased, and these were subsequently lost from the system during the winter period. Budget calculations indicated losses of around 30% of the applied calcium during the first four years. Studies on the vegetation and soils revealed a greater than expected penetration of calcium to depth (10–20 cm) in the soil profile. Results suggest that source area liming at this rate has had minimal effects on the vegetation and by increasing the proportion of the catchment limed to 15% could have a much greater success in reducing the frequency of biologically damaging episodes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00476963
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    Paper (German National Licenses)
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