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  • 1
    Electronic Resource
    Electronic Resource
    Biochemical characterization of 1,25(OH)2D3 receptors in chick embryonal duodenal cytosol (1982)
    Springer
    Calcified tissue international 34 (1982), S. 265-269 
    Details
    ISSN: 1432-0827
    Keywords: 1,25(OH)2D3 Receptor ; Chicken Duodenal Cytosol ; Chicken Embryo ; Affinity ; 1,25(OH)2D3 Concentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary This study presents measurements of serum vitamin D metabolites, calcium and phosphorus as well as measurements of the equilibrium dissociation constant for duodenal 1,25(OH)2D3 receptor in 15-, 18-, 19-, and 20-day chick embryos in comparison to that in 1- and 118-day-old chicks and to vitamin D-deficient chicks. The present results showed that: (a) serum 1,25(OH)2D and 24,25(OH)2D levels rise from 15 and 18 to days 19 and 20 of embryonic development while serum phosphate levels are stable; (b) serum calcium levels rise at hatching to adult levels; (c) the duodenal 1,25(OH)2D3 receptor is detectable in 15-day-old embryo and has a Kd similar to that of 118-day-old vitamin D-replete chicks; and (d) the activity of 1,25(OH)2D3 receptor in chick duodenal cytosol is maximal at hatching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411248
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  • 2
    Electronic Resource
    Electronic Resource
    Acidification of the young phagosomes ofParamecium is mediated by proton pumps derived from the acidosomes (1997)
    Springer
    Protoplasma 196 (1997), S. 12-20 
    Details
    ISSN: 1615-6102
    Keywords: Acidosomes ; Concanamycin B ; Phagosomes ; Proton pumps ; Paramecium ; Vacuolar ATPase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Although it is generally accepted that phagosome acidification is induced through the activity of a vacuolar proton pump (V-ATPase) present on the phagosome membrane, exactly how these pumps are delivered to the phagosomes is not well understood. To study this question inParamecium, it was necessary to first show that an authentic V-ATPase was present on their phagosomal membranes. Three antibodies raised against V-ATPases or their subunits were each found to label one or two large digestive vacuoles (DVs) inParamecium multimicronucleatum when immunofluorescence microscopy was used. Using horseradish peroxidase immunocytochemistry to increase sensitivity, about 10 DVs were shown to contain a V-ATPase. In high magnification images and cryoultramicrotomy these proton pumps were found to be located on the acidosomes, suggesting the vacuolar proton pumps on the DVs originate from the acidosomes. The authenticity of the V-ATPase was further confirmed by its sensitivity to cold temperature and to the V-ATPase specific inhibitor, concanamycin B, which at 10 nM doubled the t1/2 for vacuole acidification. Thus, we conclude that (1) acidosomes and some DVs ofParamecium have a bona-fide concanamycin B-sensitive and cold-sensitive V-ATPase, (2) the V-ATPase is delivered to the young DVs during acidosome fusion, and (3) the V-ATPase is involved in vacuole acidification. Finally, we have now determined thatParamecium has two immunologically related V-ATPases that are involved in two very different functions, (1) the acidification of phagosomes and (2) fluid segregation in the contractile vacuole complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281054
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