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  • 1
    Electronic Resource
    Electronic Resource
    Expression of PDGF-β receptor, EGF receptor, and receptor adaptor protein Shc in rat osteoblasts during spaceflight (1999)
    Springer
    Molecular and cellular biochemistry 202 (1999), S. 63-71 
    Details
    ISSN: 1573-4919
    Keywords: space flight ; osteoblast ; PDGF-β receptor ; EGF receptor ; Shc ; c-fox
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A number of studies have indicated that microgravity induces osteopenia and modulates functions of mammalian cells. However, the molecular mechanisms underlying these effects of microgravity are still unknown. Rat osteoblasts were cultured for 4 and 5 days during Shuttle-Spacelab flight, and fixed by guanidine isothiocyanate solution on board after treatment with 1α, 25 (OH)2 vitamin D3. The mRNA levels for platelet-derived growth factor (PDGF)-β receptor, epidermal growth factor (EGF) receptor, the growth factor receptor adaptor protein Shc, and c-fos were determined using the method of quantitative reverse transcription-polymerase chain reaction. The mRNA levels for EGF receptor were not altered by microgravity. However, the mRNA levels for PDGF-β receptor, Shc, and c-fos were decreased to 62, 55 and 25% on the 4th day of flight, and 47, 40, and 43% on the 5th day, respectively, as compared to the corresponding ground controls. Expression of the growth factor receptor and the receptor adaptor protein was modulated in rat osteoblasts during spaceflight. Data suggest that signal transduction via growth factor receptors in rat osteoblasts is impaired by microgravity. Dysfunction of osteoblasts might be involved in spaceflight-induced osteopenia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007097511914
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  • 2
    Electronic Resource
    Electronic Resource
    Plastoquinone as a common link between photosynthesis and respiration in a blue-green alga (1980)
    Springer
    Photosynthesis research 1 (1980), S. 149-162 
    Details
    ISSN: 1573-5079
    Keywords: blue-green algae ; cytochrome 553 ; electron transport ; photosynthesis ; plastoquinone ; respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of plastoquinone in a thermophilic blue-green alga, Shynechococcus sp., was studied by measuring reduction kinetics of cytochrome 553 which was oxidized with red flash preferentially exciting photosystem I. Sensitivity of the cytochrome reduction to DBMIB Abbreviations: DCMU = 3-(3,4-dichlorophenyl)-1,1-dimethylurea; DBMIB = 2,5-dib romo-3-methyl-6-isopropyl-p-benzoquinone; HOQNO = 2-n-heptyl-4-hydroxyquinoline-N-oxide indicates that cytochrome 553 accepts electrons from reduced plastoquinone. Plastoquinone is in turn reduced in cells without electrons from photosystem II, since DCMU Abbreviations: DCMU = 3-(3,4-dichlorophenyl)-1,1-dimethylurea; DBMIB = 2,5-dib romo-3-methyl-6-isopropyl-p-benzoquinone; HOQNO = 2-n-heptyl-4-hydroxyquinoline-N-oxide , which inhibited methyl viologen photoreduction more strongly than DBMIB, failed to affect the cytochrome reduction. Participation of cyclic electron transport around photosystem I in cytochrome reduction in the presence of DCMU was excluded, because methyl viologen and antimycin A had no effect on the cytochrome kinetics. On the other hand, electron donation from endogenous substrates to plastoquinone was suggested from decreases in rate of the cytochrome reduction by dark starvation of cells and also from restoration of fast reduction kinetics by the addition of exogenous substrates to or by reillumination of starved cells. KCN, which completely suppressed respiratory O2-uptake, induced a marked acceleration of the cytochrome reduction in starved cells. The poison was less or not effective in stimulating the cytochrome reduction in more extensively starved or reilluminated cells. Results indicate that plastoquinone is functioning not only in the photosynthetic but also in the respiratory electron transport chain, thereby forming a common link between the two energy conservation systems of the blue-green alga.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00020594
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    Paper (German National Licenses)
    Fulltext
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