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  • 1
    Electronic Resource
    Electronic Resource
    An experimental study of the uptake and loss of Ra-226 by the tissue of the tropical freshwater musselVelesunio angasi (Sowerby) under varying Ca and Mg water concentrations (1986)
    Springer
    Hydrobiologia 139 (1986), S. 59-80 
    Details
    ISSN: 1573-5117
    Keywords: Radium-226 ; uptake ; mussel ; calcium ; magnesium ; metabolic analogue ; competitive inhibition ; uranium ; mining
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Freshwater musselsVelesunio angasi (Sowerby) from Magela Creek, Alligator Rivers Region, Northern Territory, Australia, experimentally exposed to mean elevated Ra-226 water concentrations ranging between 0.95 and 1.85 Bq 1−1 for 28 days, accumulated Ra-226 in their tissue to mean concentrations ranging from 2.8 to 4.8 Bq per gram of dry tissue. The Ra-226 (log10) was accumulated in a linear pattern over exposure periods of 28 and 56 days. Mussel size and sex had little or no effect on the rates of uptake of Ra-226 per gram of tissue. Increased Ca and Mg water concentrations, both in combination and singly, reduced the rate of uptake of Ra-226 by mussel tissue. The experimental data are consistent with Ra-226 accumulation being inversely proportional to both Ca and Mg water concentrations; for Ca the constant of proportionality i.e. $$Ra = \frac{C}{{[Ca]}}$$ is unity; for Mg it is about 0.1. The results indicate competitive inhibition of the uptake of Ra-226 by Ca, i.e. that the mussel treated Ra-226 as a metabolic analogue of Ca; however, there are other possible interpretations of these results that need not invoke competitive inhibition. For Mg the results suggest involvement of some other mechanism(s) apart from or in addition to competitive inhibition of Ra-226 by Mg. Exposure of mussels that had accumulated Ra-226 under field and laboratory conditions to radium-free water for up to 286 days resulted in no significant loss (P 〉 0.05) of Ra-226 from the tissue. This indicates a very long biological half-life for Ra-226 in the tissue ofV. angasi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00770242
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  • 2
    Electronic Resource
    Electronic Resource
    Action of phosphatidylcholine in protecting ram sperm from cold shock (1986)
    New York, NY : Wiley-Blackwell
    Gamete Research 15 (1986), S. 43-56 
    Details
    ISSN: 0148-7280
    Keywords: calcium ; ultrastructure ; motility ; respiration ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Rapid cooling (cold shocking) of washed ejaculated ram sperm to 0°C irreversibly reduced motility, tail beat frequency, and respiration and increased the uptake of 45Ca2+. The plasma membranes were removed from the sperm head, and the acrosomes were detached from the nuclei. The plasma membranes of the middle piece were removed, and the mitochondria contained pale and expanded cristae, similar in appearance to ATP-deprived mitochondria in the “condensed” configuration. The presence of 2.0 mg/ml phosphatidylcholine (lecithin) in the medium prevented ultrastructural damage on cold shock, and the motility, tail beat frequency, respiratory rate, and calcium uptake were maintained at levels similar to washed sperm. As the “protective” effect of phosphatidylcholine against cold shock was maintained to a certain extent after rewashing and centrifuging the sperm prior to cold shock, the interaction of phosphatidylcholine with ram sperm membranes may be fairly “tight” and not easily disrupted.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120150106
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