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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 9 (1988), S. 9-16 
    ISSN: 0886-1544
    Keywords: adaptation ; cAMP ; cell motility ; chemotaxis ; Dictyostelium discoideum ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: When developing amebae of Dictyostelium discoideum are treated with constant concentrations of cAMP above 10-8 M, the average rate of motility is depressed, with maximum inhibition at roughly 10-6 M. It is demonstrated that shifting the concentration of cAMP from 0 M to concentrations ranging from 10-8 to 10-6 M in a perfusion chamber results in the immediate inhibition of motility. After shifting from 0 M to 10-8 or 10-7 M, the rate of cell motility remains low, then rebounds to a higher level, exhibiting a standard adaptation response. No adaptation is exhibited after a shift from 0 M to 10-6 M, a concentration resulting in maximum inhibition. It is demonstrated that the level of inhibition and the extent of the adaptation period are dependent upon the concentration of cAMP after the shift, and that submaximal inhibition is additive. The characteristics of adaptation in this motility response are very similar to the characteristics of adaptation for the relay system and phosphorylation of the putative cAMP receptor.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0730-2312
    Keywords: tumor cells ; cell-cell interaction ; desmoplasia ; extracellular matrix ; stroma reaction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The influence of various normal and malignant human cells on the level of collagen synthesis by human fibroblasts was tested in coculture. As revealed by immunoperoxidase staining, in cocultures with breast adenocarcinoma cells (MCF7, SA52, T47D) fibroblasts synthesized collagen while tumor cells did not. Fibroblasts displayed increased collagen production without change in the overall protein synthesis. Several other types of cells derived from normal human tissues (keratinocytes, normal mammary cells) or from fibrosarcoma, melanoma, cervical carcinoma, choriocarcinoma, or other breast adenocarcinoma (SW613, MDA, BT20) did not affect collagen synthesis of fibroblasts. Although to a lesser extent, this stimulating effect was reproduced by using the conditioned medium (CM) of the active cells but not with CM of the other cell types. A slight stimulation was also obtained when tumoral MCF7 cells and fibroblasts shared the same medium but were physically separated, suggesting that close contact was required for optimal stimulation of collagen synthesis. The collagen synthesis stimulating activity was not related to a modification of fibroblast proliferation rate. The production of collagen types I, III, and VI and fibronectin were increased in cocultures of fibroblasts with MCF7 cells. The increased synthesis of collagen types I and III and fibronectin was paralleled by similar changes in the steady-state level of their mRNAs. On the contrary, the increased production of collagen type VI appeared regulated at a post-transcriptional level.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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